impacto sobre la rigidez arterial de un tratamiento

Impacto sobre la rigidez arterial de un tratamiento

inmunosupresor basado en la inhibición de la señal de

coestimulación (belatacept) frente a otros basados en

la inhibición de la calcineurina (ciclosporina,

tacrolimus) en el trasplante renal

Tesis presentada por

Edoardo Melilli

Para obtener el título de doctor por la Universitat de Barcelona

Dirigida por

Josep Mª Cruzado Garrit

Programa de Doctorado de Medicina Facultad de Medicina

Universitat de Barcelona

2017

UNIVERSITAT DE BARCELONA DIVISION DE SCIENCIA CLINICA

FACULTAT DE MEDICINA

Impacto sobre la rigidez arterial de un tratamiento

inmunosupresor basado en la inhibición de la señal de

coestimulación (belatacept) frente a otros basados en la

inhibición de la calcineurina (ciclosporina, tacrolimus) en el

trasplante renal

Doctorando: Dr. Edoardo Melilli Director de la Tesis: Prof. Josep María Cruzado Garrit Línea: Trasplante Nefrología y Trasplante Renal IDIBELL

Agradecimientos:

Mis agradecimientos van a mi Director de Tesis, Dr. Josep Mª Cruzado, por

haber aceptado dirigir esta tesis y por su apoyo constante en la realización de

la misma; al Prof. Josep Mª Grinyó, por darme la posibilidad primero de venir a

rotar como residente en el Servicio de Nefrología del Hospital de Bellvitge en

2008 y, después, de volver en 2010 como adjunto; al Dr. Alberto Martínez

Castelao, por haber puesto en mis manos la tecnología necesaria para la

realización de la tesis.

A mis compañeros Nefrólogos y Residentes del Servicio de Nefrología del

Hospital de Bellvitge, compartir con vosotros todos los días la pasión hacia

nuestra especialidad es lo que hace más soportable un trabajo que a veces

resulta muy intenso. Sois mi segunda familia y lo sabéis.

Ai miei colleghi nefrologi e specializzandi di Verona, in particolare al Dr. Nicola

Tessitore, per avermi insegnato l’importanza di valutare con cura il peso di ogni

variabile nei processi diagnostici e/o terapeutici e per le ore passate a

discorrere di storia del jazz; grazie al Dr. Nicola Marchionna per la sua amicizia

e vicinanza negli anni di specializzazione;

A los que por primeros me introdujeron en el mundo de la Nefrología: el Prof.

Maurizio Li Vecchi de la Università di Palermo y el Dr. Juan García Valdecasas

de la Universidad de Granada.

Ai miei compagni di studio degli anni universitari, Gioacchino, Ciccio, Achille e

Antonio. In questi anni siamo riusciti a mantenere i contatti nonostante le

distanze e le vostre scelte “discutibili” di non fare Nefrologia ma chirurgia o

peggio.

Ai miei genitori, spero che questa tesi possa farvi sentire orgogliosi e almeno in

parte compensare la mia distanza e le mie infinite assenze.

A Pina, porque sin ti no hubiera sido posible y porque me haces una persona

mejor.

ABREVIATURAS

Aix: Índice de aumento de la presión arterial central, expresado en % AP: Índice de aumento de la presión arterial, expresado en mm/Hg ARAII: Antagonista de los receptores de angiotensina II BLC: Belatacept CNI: Inhibidores de la calcineurina DAMPS: Patrones moleculares asociados a peligro ERC: Enfermedad Renal Crónica eGFR: Filtrado glomerular estimado IECA: Inhibidores de la enzima convertidora de angiotensina iMtor: Inhibidores diana de rapamicina en células de mamífero IRR: Índice de resistencia renal MAPA: Monitorización ambulatoria de la presión arterial PWV: Velocidad de la onda de pulso

Índice

1.Introducción_______________________________________________________ 11

2.Medicióndelarigidezarterialenlaprácticaclínicahabitual________________ 15

3.Rigidezarterialenpacientestrasplantadosrenales._______________________ 23

4.Inmunosupresiónyrigidezarterial.Elpapeldelasdiferentesclasesdeinmunosupresores____________________________________________________ 25

4.1.Inhibidoresdelacalcineurina:tacrolimusyciclosporina_______________________284.2.InhibidoresdemTor:SirolimusyEverolimus________________________________304.3Inhibidordelaseñaldelacoestimulación:belatacept. ________________________32

5.Hipótesisdeltrabajo ________________________________________________ 37

6.Objetivos__________________________________________________________ 39

7.Estudiospublicados_________________________________________________ 417.1DifferentialimpactofbelataceptandcyclosporineAoncentralaorticbloodpressureandarterialstiffnessafterrenaltransplantation.ClinTransplant.2014______________417.2.Arterialstiffnessinkidneytransplantation:asinglecentercase-controlstudycomparingbelataceptversuscalcineurininhibitorimmunosuppressivebasedregimen.Nefrología.2015 __________________________________________________________487.3.Impactofimmunosuppressivetherapyonarterialstiffnessinkidneytransplantation:Arealltreatmentsthesame?InpressClinicalKidneyJournal______________________57

8.Resultados ________________________________________________________ 678.1Estudio1:DifferentialimpactofbelataceptandcyclosporineAoncentralaorticbloodpressureandarterialstiffnessafterrenaltransplantation_________________________678.2Estudio2:Arterialstiffnessinkidneytransplantation:asinglecentercase-controlstudycomparingbelataceptversuscalcineurininhibitorimmunosuppressivebasedregimen _________________________________________________________________70

9.Discusión__________________________________________________________ 75

10.Conclusiones______________________________________________________ 81

Bibliografía__________________________________________________________ 83

Edoardo Melilli Belatacept, rigidez arterial y trasplante renal

11

1. Introducción

La elevada mortalidad cardiovascular es uno de los aspectos más frustrantes

en el campo del trasplante renal. Frente a unos resultados excelentes de

supervivencia del injerto al año del trasplante renal1, el riesgo cardiovascular es

todavía muy elevado si lo comparamos con el de la población general, 2

independientemente de la recuperación de la función renal. 3, 4

Las complicaciones cardiovasculares representan la 1ª causa de mortalidad en

los pacientes trasplantados renales en España y la segunda causa de pérdida

del injerto renal.5

Según recientes datos publicados por el Registro de enfermos renales de

Cataluña, las causas cardiacas y vasculares en los primeros 5 años post-

trasplante renal suman entre el 44 y 47 % de todas las causas de muerte.

Durante los últimos 10 años (2005-2015), los datos de mortalidad por 100

pacientes-año por causas cardiovasculares se han mantenido sustancialmente

estables, ligeramente en aumento las causas vasculares y ligeramente en

disminución las causas cardiacas.6

Este exceso de mortalidad no se explica simplemente por la amplia prevalencia

de factores de riesgo cardiovascular clásicos (dislipidemia, hábito tabáquico,

hipertensión arterial, obesidad) en los receptores de un trasplante renal, ya que

su corrección no ha supuesto una mejora significativa en la supervivencia.3, 5

Por otra parte, las calculadoras de riesgo cardiovascular utilizadas para la

estimación del riesgo en la población general infraestiman sistemáticamente el

riesgo de los pacientes trasplantados renales.7

El tratamiento inmunosupresor y otros factores de riesgo cardiovascular no

convencionales pueden explicar en parte este fallo en la previsión de eventos

cardiovasculares en los trasplantados renales.8

La rigidez arterial es uno de estos factores de riesgo cardiovasculares no

convencionales cuya importancia ha ido creciendo en la última década. La

rigidez arterial es un proceso biológico relacionado con el envejecimiento,9, 10


12

con la presión arterial, 11 con la inflamación, 12, 13 con el estadio de insuficiencia

renal 14 y con las calcificaciones vasculares. 15 La calcificación de la túnica

media de los grandes vasos elásticos (por ejemplo aorta) está causada por

diferentes mecanismos fisiopatológicos, entre ellos destacan el aumento de la

fetuin-A, la deposición de la proteína de matriz con ácido gamma-

carboxiglutámico, el aumento de los niveles séricos de osteoprotegerina, la

disminución de la proteína Klotho y el cambio de morfotipo de las células

musculares lisas vasculares hacia un fenotipo secretor tipo células

osteoblásticas.16 Todos estos factores determinan una aparición precoz del

proceso de calcificación vascular en pacientes con insuficiencia renal crónica,17

determinando así un aumento de la rigidez arterial.

En los receptores de un trasplante renal, diferentes estudios han relacionado la

elasticidad arterial con factores tales como edad del donante,18 rigidez arterial

del donante vivo, 19 diabetes post trasplante, 20 tiempo de isquemia fría, 21

hipomagnesemia, 22 actividad física de resistencia 23 y filtrado glomerular.

Kneifel et al,24 concretamente, en un estudio de diseño transversal, mostraron

que dos parámetros relacionados con la rigidez arterial (C1 y C2 – evaluados

con la tonometría radial) tenían relación inversa con el (eGFR) glomerular

estimado según MDRD, replicando así los resultados en paciente con

enfermedad renal crónica (ERC) no trasplantados.20

A diferencia de otro tipo de paciente, en los receptores de un trasplante renal,

el tiempo de enfermedad (años con insuficiencia renal y/o en tratamiento renal

substitutivo crónico) es un aspecto determinante. Ferro et al. mostraron como el

tiempo en tratamiento renal substitutivo resulta ser una variable predictiva

independiente del Aix (un parámetro de rigidez arterial) tras el trasplante

renal.25 Por otro lado, el trasplante renal y la consiguiente recuperación de la

función renal son capaces, per se, de reducir y/o evitar la progresión de la

rigidez aórtica. Por ejemplo, Zoungas et al. demostraron como el Aix mejora

significativamente tras un año del trasplante renal.26 Más recientemente, Karras

A et al, efectuando un estudio longitudinal, han evaluado otros dos parámetros

de rigidez arterial, la velocidad de la onda de pulso (PWV) y la distensibilidad

de la arteria carótida a 3 y 12 meses del trasplante renal, confirmando que

ambos parámetros de rigidez arterial mejoraban, independientemente de la


13

función renal alcanzada y de la presión arterial, pero en función del tipo de

donante. Los receptores de trasplantes procedentes de donante vivo o de

cadáver con criterios estándar resultaban tener una mejora significativa de la

rigidez arterial en comparación con los trasplantes procedentes de donantes

con criterios expandidos.27

El papel de algunos fármacos comúnmente utilizados tras el trasplante renal

(inmunosupresores, antihipertensivos, análogos de la vitamina D, etc.) en la

progresión de la rigidez arterial ha sido objeto de estudio en los últimos años.

El tratamiento con inhibidores de la calcineurina (CNI), sobre todo de la

ciclosporina, es reconocido como factor de progresión de la rigidez arterial.25, 28

En pacientes hipertensos, la reducción de la presión arterial consigue reducir la

rigidez arterial con algunas clases de fármacos anti-hipertensivos que parecen

más eficaces con respecto a otras, 29,30 aunque este efecto clase-dependiente

resulta relacionado más con la magnitud de la reducción de presión arterial que

con la clase de fármaco.31 Cabe destacar que, tras el trasplante renal la mejora

de la rigidez arterial puede ser independiente de la reducción de la presión

arterial,25 y que diferentes parámetros de rigidez arterial predicen eventos

cardiovasculares de manera independiente de la presión arterial misma.32

Los calcimiméticos y los análogos de la vitamina D pertenecen a otra clase de

fármacos que se suelen utilizar en el post-trasplante renal y que podrían tener

un impacto sobre la rigidez arterial. La relación entre déficit de Vitamina D y

aumento de la rigidez arterial en pacientes con ERC está bien documentada.33

Recientemente, un estudio en pacientes con ERC ha mostrado como el uso de

calcifediol mejora los parámetros de velocidad de la onda de pulso con

respecto a calcitriol o placebo. 34 En cambio, en pacientes trasplantados

renales, el uso de paricalcitol o de vitamina D nativa no mejoran los parámetros

de rigidez arterial. 35 , 36 Finalmente, el impacto de regímenes de

inmunosupresión basados en anti-calcineurínicos o en los inhibidores de mTor

ha sido evaluado en un trial recién publicado, no demostrando grandes

diferencias entre las dos clases de fármacos.37


14


15

2. Medición de la rigidez arterial en la práctica clínica habitual

El descubrimiento, a partir de los años 60, que la hipertensión arterial es una

de las causas de aumento del riesgo de mortalidad cardiovascular ha sido un

gran avance en la medicina moderna.38, 39 Puesto que la hipertensión arterial es

reconocida hoy en día como el primer factor de riesgo cardiovascular, 40 la

medición rutinaria de la presión arterial es probablemente la maniobra médica

más eficaz en la prevención de eventos cardiovasculares en la historia de la

medicina.

Las principales líneas-guía en prevención cardiovascular estratifican el riesgo

basándose en valores de presión arterial medidos a nivel de la arterial braquial.

Cabe destacar pero que los valores de presión medidos con este método no

tienen una correlación óptima ni con los valores intra-arteriales braquiales ni

con los intra-arteriales aórticos, por lo tanto son necesarios métodos capaces

de mejorar la estimación del riesgo cardiovascular.41 Las medidas invasivas de

las presiones intra-arteriales (presión intra-aórtica o intra-braquial) representan

el “gold standard” en la estimación del riesgo cardiovascular, ya que presentan

una correlación directa con la rigidez arterial, pero implican la necesidad de

cateterismo arterial.42

Por su naturaleza elástica, la aorta no es un mero conducto, ya que es capaz

de acumular parte del volumen de sangre eyectado durante la fase sistólica y

de empujarlo a lo largo del árbol vascular durante la fase diastólica. 43

La capacidad elástica de la aorta se puede expresar a través de los parámetros

de compliance y distensibilidad que representan el cambio del volumen relativo

(ΔV/V) o absoluto (ΔV) por un determinado cambio de presión (ΔP). 44 La

distensibilidad aortica (AD) por lo tanto puede ser expresada con la siguiente

formula:

AD = área aórtica máxima – área aórtica mínima área aórtica mínima X ΔP


16

El volumen de sangre que se propaga gracias a la distensibilidad de la aorta

genera una onda con morfología de presión fácilmente distinguible. La

velocidad de la onda de pulso es la velocidad de propagación de dicha onda de

presión a través del árbol vascular. A causa de cambios estructurales y

funcionales, debido principalmente a los procesos de envejecimiento y de

arteriosclerosis, la aorta pierde progresivamente su elasticidad y la onda de

pulso se propaga más rápidamente.45 La relación entre distensibilidad aórtica y

PWV se expresa a través de la siguiente ecuación:

PWV: √ΔP x A ρ x ΔA

donde: P = presión A = área ρ = viscosidad

Simplificando, se puede considerar que la PWV es el inverso de la

distensibilidad. Esta fórmula considera la elasticidad del vaso como si este

fuera una estructura cavernosa (hollow) y que la capacidad elástica se

mantuviera constante a lo largo de su recorrido (asunción que en algunos

casos puede ser diferente). Como alternativa, otra fórmula más precisa es la

siguiente:

PWV = Einc x h/2r x ρ

donde

Einc = módulo incremental elástico (o módulo de Young), mide la capacidad

elástica del material objeto de estudio

h = espesor del vaso


17

r = radio

ρ = densidad.

No hay que confundir la PWV con la velocidad de la sangre, ya que la primera

se mide en m/s y representa la energía acumulada durante la sístole, mientras

que la segunda se mide en cm/s y representa el movimiento de una masa a

través de la columna sanguínea.43

Cuando alcanza los puntos de impedancia en el árbol aórtico (bifurcaciones y

vasos más pequeños), la onda de pulso anterógrada generada durante la

sístole da lugar a su vez a una onda hacia atrás (retrógrada) que, en presencia

de rigidez arterial, llega a la aorta durante la sístole del mismo ciclo cardíaco,

causando un incremento de la presión arterial central, definido como

“augmentation pressure” (AP, medido en mm/Hg) y que se puede también

cuantificar como Aix, definido como el porcentaje de presión de pulso central

atribuido a la onda de pulso retrógrada. En caso de una PWV aórtica baja, la

onda retrógrada vuelve a la aorta entre el final del ciclo sistólico y el inicio de la

diástole, favoreciendo el aumento de la presión diastólica y la perfusión

coronaria y reduciendo la transmisión de la presión pulsátil a la

microcirculación.43

Las Figuras 1 y 2 muestran como los cambios estructurales en la aorta, en las

pequeñas arterias y en las arteriolas modifican la PWV, el AP y el Aix, los tres

parámetros más evaluados en estudios sobre de la rigidez arterial.


18

Figura 1. La velocidad de onda de pulso (PWV) y sus modificaciones dependiendo de la presencia de patología. Desde Melilli et al. CKJ 2017 in press.


19

Figura 2. Ejemplo ilustrativo de la morfología de una onda pulso en situación normal y en caso de reducción de elasticidad arterial. Debido a la reducción del tiempo de tránsito en caso de rigidez arterial la onda retrograda se suma a la anterógrada y se obtiene un aumento de la presión aórtica (incremento de la augmentation pressure). Desde Seibert F, Melilli E et al. modificada.110

Existen diferentes métodos para valorar de manera no invasiva la rigidez

arterial. Algunos de ellos son capaces de medir la rigidez arterial “regional”, o

sea de un largo tramo de la aorta, mientras que otros (como la resonancia

magnética y/o los métodos que utilizan echotracking) pueden medir la

distensibilidad de un vaso superficial y la PWV local (de un tramo corto del

vaso, en general a nivel del arco aórtico). 44, 46

Los aparatos más comúnmente usados para medir la PWV regional en los

estudios clínicos son Sphigmocor® y Complior®, cada uno con su propio

algoritmo para el análisis de las ondas de pulso. El algoritmo de intersección

del aparato Sphigmocor®, en principio, presenta más precisión con respecto a

los algoritmos usados por otros aparatos.47 Analizando la morfología de las

ondas de pulso periféricas a través de la tonometría de aplanación es posible


20

calcular el AP (medido como mmHg) y el Aix (definido por %). Estos dos

índices reflejan la presión aortica central y, por lo tanto, deberían ser mejor

predictores de eventos cardiovasculares comparados con la presión arterial

sistémica,48 , 49 aunque no hay consenso sobre la precisión de los métodos

disponibles para medirlos no invasivamente. 50, 51, 52

Siendo un tiempo de tránsito, la velocidad de la onda de pulso depende de la

distancia medida entre dos puntos. Por lo tanto, un momento crítico en su

evaluación es la correcta medición de la distancia entre los dos puntos (suelen

ser la carótida común y arteria femoral) utilizados para detectar las ondas de

pulso a través de la tonometría de aplanación o de la ecografía.

Idealmente, para medir la PWV con precisión, la distancia entre los dos puntos

debería seguir el recorrido de la aorta. Este puede ser medido de dos formas:

directamente desde la carótida a la femoral común, o calculando la distancia

entre la muesca esternal y la femoral común y substrayendo la distancia

medida entre la muesca esternal y la carótida común. Dependiendo del método

utilizado, se ha detectado una desviación de hasta el 30 %.53 Nuestro grupo

usa el método de medición de la distancia directa y luego corrige por un factor

de 0.8, siguiendo las recomendaciones del documento de consenso.54

Las mediciones para la PWV se realizan dos veces, si entre las dos mediciones

hay una diferencia > 0.5 m/s, se recomienda efectuar una tercera medición.54

La Figura 3 muestra las 4 fases para medir la rigidez arterial.


21

Figura 3. Medición de la PWV en 4 pasos.

Aunque el número de publicaciones acerca de la rigidez arterial en trasplante

renal está en aumento, la mayoría de estudios presentan limitaciones

metodológicas que sugieren cautela en la interpretación de los resultados. Del

mismo modo que con cualquier método de medición realizado por un operador,

existe el riesgo de una alta variación inter-observador. Aunque las técnicas

para medir la rigidez se han ya validado en términos de reproducibilidad en

pacientes sanos y CKD, 55 , 56 , 57 la mayoría de estudios publicados en el

trasplante renal no reportan datos acerca de la variabilidad intra- o inter-

observador, y por consiguiente es difícil establecer y comparar la calidad de los

datos de cada estudio. De hecho, solo pocos estudios llevados a cabo en el

trasplante renal han reportado un índice de coeficiente de variación aceptable

(ICC) para operador,19, 58, 59 pero existe todavía una extrema escasez de datos

en variaciones intra-paciente de los parámetros de rigidez.


22


23

3. Rigidez arterial en pacientes trasplantados renales.

En la evaluación de la rigidez arterial, es de fundamental importancia

establecer qué valores de los parámetros analizados se utilizan como cut-off o

corte de normalidad.

Para la PWV, las guías clínicas de hipertensión de la ESH/ESC de 2007

recomiendan un valor de umbral fijo de 12 m/s para detectar pacientes con un

alto riesgo cardiovascular.60 No obstante, más recientemente un documento de

consenso ha fijado este valor en 10 m/s.54 De todos modos, e

independientemente del valor de corte, el riesgo cardiovascular aumenta

incluso con un umbral más bajo.60

En una cohorte de 330 pacientes trasplantados renales de un estudio alemán,

la PWV fue predictiva de supervivencia y eventos cardiovasculares

independientemente de la edad de los pacientes. Los pacientes con una PWV

de 7.5 m/s o superior mostraron una peor tasa de supervivencia que los

pacientes con una PWV inferior a 7.5 m/s.61

En 2011, en un estudio prospectivo de una cohorte de 512 receptores de

trasplante renal, se determinó la PWV, el AP y el Aix en el momento del

trasplante renal. Tras un tiempo medio de seguimiento de 5 años, se incluyeron

la PWV y el AP en un modelo basado en variables clínicas y en datos de

laboratorio con el objetivo de predecir eventos cardiovasculares. El aporte de

PWV y AP llevó a una mejora neta de reclasificación para eventos

cardiovasculares del 15.9 %. Además, los pacientes con una PWV de 8.1 m/s o

superior presentaban una peor tasa de supervivencia cardiovascular con

respecto a los pacientes con una PWV inferior a 8.1 m/s.62

Finalmente, un estudio reciente de un grupo noruego con 1022 receptores de

trasplante renal ha mostrado que, por debajo de un valor de corte de 12 m/s,

cada incremento en PWV de 1 m/s a partir de 8 m/s estaba relacionado con un

aumento del riesgo de muerte del 36 %. 63

La tabla 1 resume los estudios que han evaluado el impacto de la rigidez


24

arterial en el post trasplante renal.

Tabla 1. Resumen estudios valor predictivo rigidez arterial en el post-trasplante

Estudio Número pacientes

Follow up

(media)

Método para medir la distancia para cálculo

de PWV

¿PWV es predictor de mortalidad

cardiovascular?

¿Aix y/o AP son predictores de

mortalidad cardiovascular?

Mitchel A

2010 61 330 3.8 Distancia desde la

muesca supraesternal hasta el ombligo + desde el ombligo hasta el sitio femoral menos la distancia desde la carótida hasta la muesca supraesternal

SI NA

Verbeke F

201162 512 5 80% de la distancia

medida desde la carótida hasta la femoral.

SI SI

Dahle D

201563 1040 4.2 Distancia desde la

muesca supraesternal hasta el ombligo + 10 cm.

SI NA

“Augmentation pressure y augmentation index” han sido relacionados con la

función renal, 64 con el aumento del riesgo cardiovascular en pacientes

hipertensos 30 y con la cardiopatía isquémica.65 En trasplante renal, por un lado

el Augmentation index es predictor de eventos cardiovasculares, 62 aunque

también destaca una vez más el efecto protector del trasplante renal sobre el

Aix.66 Kaur M et al. reportaron como, en un grupo de pacientes en hemodiálisis

y sometidos a trasplante renal, el Aix disminuía desde un 27.7±11 % hasta un

17.1±9 % (p 0.0001) a los 3 meses del trasplante, mientras que tanto la presión

arterial sistémica como la presión aórtica central y la velocidad de la onda de

pulso no mostraron variaciones significativas.66

Los estudios efectuados han mostrado un potente valor predictivo de la PWV y

del Aix para eventos cardiovasculares y mortalidad (ver Tabla 1),

independientemente de la edad y de otras variables clínicas o de laboratorio,

confirmando de este modo los datos obtenidos en otros estudios con

poblaciones de pacientes diferentes.67


25

4. Inmunosupresión y rigidez arterial. El papel de las diferentes clases de inmunosupresores

Como se ha descrito anteriormente, la toxicidad de los CNIs sobre los vasos

arteriales está bien documentada, por lo menos a nivel de microcirculación. Los

tipos de toxicidad descritos para la ciclosporina son dos: toxicidad aguda y

crónica.68

La toxicidad aguda es una alteración funcional debida a un desequilibrio entre

vasoconstrictores y vasodilatadores, que lleva a una reducción en el flujo

sanguíneo renal y a un incremento en la resistencia vascular, sobre todo a nivel

arteriolar. Ya que la resistencia de la red arteriolar es la “última barrera” contra

la presión de pulso y representa el punto de inicio de la onda retrógrada, esta

vasoconstricción a nivel arteriolar es, con mucha probabilidad, la causa del

aumento de algunos parámetros de rigidez (Aix y AP) en pacientes tratados

con ciclosporina. Diferentes factores parecen jugar un papel en esta toxicidad

aguda: hiperactivación del sistema renina-angiotensina,69 sobreexpresión de

los receptores endoteliales,70 daño de la célula endotelial,71 alteración en la

producción de óxido nítrico L-arginina e hiperactivación del sistema simpático.72

Se sabe que los antagonistas del calcio y ARAII o IECA mitigan la toxicidad

aguda, dificultando de este modo la interpretación de cómo todos los anteriores

factores contribuyen a la toxicidad vascular aguda en un contexto clínico.73, 74

La toxicidad crónica se caracteriza por un cambio estructural en los vasos,

afectando sobre todo las pequeñas arterias y las arteriolas.75 Las lesiones

hialinas en la pared arteriolar, sello distintivo de la toxicidad de los CNI, son

presentes en la biopsia de protocolo a 10 años en la mayoría de pacientes que

reciben tacrolimus o ciclosporina 76 La terapia con iMtors (sirolimus y

everolimus) ha demostrado atenuar la vasculopatía del injerto en receptores de

trasplante de corazón.77, 78

Si los fármacos inmunosupresores son capaces de modificar la PWV u otros

parámetros de rigidez arterial, influyendo directa o indirectamente en la

vasculatura, sigue siendo especulativo y difícil de demostrar. Primero, porque el


26

trasplante de por sí mejora la rigidez arterial.20, 26, 27, 66 Segundo, por la relación

intrínseca entre PWV y presión arterial, aunque Seibert et al. mostraron que

una PWV alta está relacionada con eventos cardiovasculares, de manera

independiente a la mejora de la presión arterial sistémica post-trasplante.32

Finalmente, porque la mayoría de estudios publicados hasta ahora son

pequeños, retrospectivos y caso-controles (ver Tabla 2).

Tabla 2. Estudios principales en trasplante renal sobre la relación rigidez arterial y el tipo de inmunosupresión y sus limitaciones principales.

Estudio Diseño Aparato N. IMS Resultados Limitación

Zoungas S.26

2004 Longitudinal Mikro-t. 36 24 CYC

12 TAC PWV: no diferencias AIX: TAC ¯¯¯/ CYC ¯

N pequeña.

Ferro C25

2002 Transversal

Sphigm. 250 146 CYC 62 TAC

PWV: NA AIX: TAC ¯VS CYC

Diseño

Stróecki P80

2007 Transversal Complio 152 76 CYC

76 TAC PWV: TAC ¯ VS CYC AIX: NA

Diseño

Seckinger J58 2008

Conversión CYC a EVR

Complio 27 10 CYC 17 EVR

PWV: CYC EVR ¯ AIX: NA

N pequeña; Follow up corto;

Joannidé R89

2011 Conversión CYC a SRL

Sphigm 44 21 CYC 23 SRL

PWV: CYC SRL ¯ AIX: CYC SRL ¯

N pequeña; Criterio de selección;

Gungor 090

2011 Transversal Sphigm 81 47 CNI

34 iMtor PWV: No diferencias AIX: No diferencias

N pequeña; Mescla CNI/Imtor

Seibert F110

2014 Transversal Sphigm 46 23 BLC

23 CYC PWV: no diferencias AP: BLC ¯ VS CYC

N pequeña; Criterio de selección;

Melilli E59

2015 Transversal Sphigm 40 20 BLC

20 CNI PWV<8.1: BLC60%-CNI40% AIX: NA

N pequeña; Diseño;

Cruzado JM91

2016 Conversión TAC a EVR

Spighm 60 32 TAC 28 EVR

PWV: No diferencias PWV normal N pequeña;

Holdaas H37

2017 Conversión CNI a EVR

Sphigm 164 95 CNI 69 EVR

PWV: No diferencias AIX: NA

PWV normal Mescla CNI

Leyenda: TAC = tacrolimus; CYC = ciclosporina; EVR = everolimus; SRL = sirolimus; iMtor =EVR y SRL; CNI=CYC y TAC; BLC= belatacept; PWV=pulse wave velocity; Aix=Augmentation index; IMS=inmunosupresión utilizada; NA: No reportado.

A pesar de dichas limitaciones, existen pruebas de que los protocolos de

retirada de CNI tienen un efecto protector en la progresión de la rigidez arterial

en los pacientes receptores de trasplante renal.


27

La tabla 3 resume el impacto de fármacos inmunosupresores diferentes en

PWV, Aix y presión arterial sistémica.

Tabla 3. Efecto de los inmunosupresores más frecuentemente utilizados sobre la rigidez arterial en el post-trasplante renal.

Fármaco Presión Arterial Sistémica PWV Aix o AP

Ciclosporina +++ ++ ++/+

Tacrolimus +/++ -/+ +

iMtor (everolimus o sirolimus) - - -/+

Belatacept - - -

Mycophenolate Mofetil - ? ?

Steroid + ? ?


28

4.1. Inhibidores de la calcineurina: tacrolimus y ciclosporina

Los primeros datos acerca del efecto de los CNI en las funciones de las

grandes arterias son conflictivos. Zoungas S. et al. en un estudio prospectivo,

compararon la PWV antes y después de trasplante renal en 36 pacientes. A 12

meses del trasplante, la PWV mejoró en todos los pacientes,

independientemente del uso de ciclosporina o tacrolimus, aunque la reducción

del Aix fue mayor en pacientes tratados con tacrolimus (−8.0 ± 16.5 % vs −27.4

± 18.2 % p 0.01).26

En un pequeño estudio, Covic et al. mostraron que la ciclosporina disminuye

agudamente el Aix. De todos modos, el estudio adolece de grupo de control y

la reducción de AIX tras la administración de ciclosporina estaba relacionada

con una disminución en el tiempo de la onda retrógrada, lo que podría llevar a

una velocidad de la onda de pulso aumentada a largo plazo.79

Es interesante ver que, en el mismo periodo, un estudio transversal (con 250

receptores de trasplante renal estables) mostró que la ciclosporina aumentaba

el Aix y la presión arterial mucho más que el tacrolimus.25 En 2007, Stróecki P.

et al. compararon la PWV en 76 pacientes tratados con ciclosporina 1:1 con

tacrolimus. Los dos grupos de estudio estaban pareados por las principales

características clínicas (edad, presión arterial, tiempo en hemodiálisis,

diabetes). El grupo ciclosporina tenía valores de PWV mayores con respecto al

grupo tacrolimus (9.33 ± 2.10 vs. 8.54 ± 1.35 respectivamente; p <0.01).80 En

otro estudio del mismo grupo, un análisis de regresión múltiple mostró que

edad, sexo masculino, presión arterial media, ciclosporina (vs tacrolimus) y

concentración de glucosa en ayunas estaban independientemente asociados

con un aumento en PWV.81 El efecto de la ciclosporina en la rigidez parecía

deberse probablemente a un aumento del tono vascular o a una vasodilatación

por óxido nítrico, aunque un estudio de Silverborn M et al. no confirmó tal

hipótesis. Comparando 18 receptores de trasplante pulmonar (todos tratados

con ciclosporina) con pacientes en lista de espera y controles sanos se

analizaron resistencia arterial, relajación no dependiente del endotelio y rigidez

arterial (con método echotracking). Los receptores de trasplante pulmonar


29

presentaban arterias significativamente menos elásticas con respecto a los

controles sanos o a los pacientes en lista de espera, aunque no se detectó

ninguna diferencia en la presión arterial o en la respuesta endotelial al óxido

nítrico.82

Puesto que la ciclosporina estaba relacionada con una mayor PWV, la

conversión a tacrolimus podría ser una opción para mejorar la rigidez arterial.

Esta hipótesis se ha testado en un pequeño estudio en el cual se han

convertido a tacrolimus receptores de trasplante renal estable tratados con

ciclosporina (más de 10 años). La PWV (con método echotracking) y la MAPA

fueron medidas al inicio y repetidas 3 meses después de la conversión. No se

ha visto ninguna diferencia en la presión arterial ni en PWV, probablemente

debido al poco tiempo de la conversión.83

A pesar de las limitaciones en sus diseños, todos los estudios anteriores

sugieren un posible impacto negativo de CNI, y sobre todo ciclosporina, en la

rigidez arterial.


30

4.2. Inhibidores de mTor: Sirolimus y Everolimus

Los iMtor –everolimus y sirolimus– están todavía en desarrollo en el régimen

inmunosupresor en el trasplante renal. Sin embargo, desde su primer uso no

han demostrado una eficacia superior en cuanto a supervivencia renal o

prevención de rechazo con respecto al tacrolimus. 84 , 85 A parte de sus

propiedades inmunosupresoras, los iMtor ejercen cierto efecto pleiotrópico

sobre la aterogénesis86 , 87 y la fibrosis,88 así que, teóricamente, la elasticidad

arterial de los receptores de trasplante renal podría beneficiarse de su uso.

En un ensayo clínico aleatorizado, se convirtieron 17 de 27 pacientes de

ciclosporina a everolimus 6 meses después del trasplante renal. La PWV quedó

estable en el grupo everolimus (9.50±1.92 vs. 9.13±1.62 m/s, ΔPWV -0.37±1.14

m/s) mientras que aumentó en el grupo ciclosporina. (9.93±1.94 vs. 10.8±2.24

m/s, ΔPWV +0.89±1.47 m/s).58

En un sub-estudio del ensayo CONCEPT,89 se convirtieron 23 de 44 pacientes

de ciclosporina a sirolimus 12 semanas después del trasplante renal. PWV y

Aix se midieron en las semanas 12, 26, 52. La PWV aumentó progresivamente

en el grupo tratado con ciclosporina, mientras que se redujo en el grupo

sirolimus, siendo la diferencia estadísticamente significativa en la semana 52.

En ambos grupos se detectó un aumento en Aix, pero fue más elevado en el

grupo ciclosporina. Según los autores, la reducción progresiva de PWV en el

grupo sirolimus fue la causa, y no la consecuencia, de un mejor control de la

presión arterial.

A pesar de estos resultados alentadores, un estudio transversal de Gungor O

et al.90 no ha mostrado beneficios en PWV o Aix en un grupo de pacientes

tratados con iMtor (por lo menos 6 meses, sirolimus o everolimus) comparados

con CNI (ciclosporina o tacrolimus). En un análisis de regresión lineal, solo los

factores de riesgo convencionales (edad, presión arterial, nivel de colesterol y

proteinuria) fueron predictores de rigidez arterial.

Más recientemente, un ensayo clínico aleatorizado acerca del efecto de la


31

conversión tardía de CNI (tacrolimus) a iMtor (everolimus) ha mostrado un

pequeño beneficio en la regresión de la hipertrofia ventricular izquierda en

ambos grupos. Como resultado secundario, se han evaluado el cambio en la

presión arterial (medida por MAPA) y en la PWV antes y después de la

conversión. El tiempo medio desde el trasplante ha sido de 1.7 años en el

grupo tacrolimus (25 pacientes) y 1.3 años en el grupo everolimus (31

pacientes). A 24 meses de la aleatorización, ambos grupos tenían una presión

arterial muy bien controlada, aunque el estado dipper se mantuvo en más

pacientes con everolimus (30% de los tratados con tacrolimus eran no dipper

vs 22% de los pacientes tratados con everolimus). Los valores de PWV

iniciales, a 12 y 24 meses eran en el rango normal sin diferencias significativas

entre los dos grupos de estudio.91

Uno de los objetivos secundarios del ensayo clínico aleatorizado ELEVATE ha

evaluado la PWV y la presión arterial mediante MAPA.92 Los datos de PWV se

obtuvieron de 277, 223 y 184 pacientes, en los meses 3, 12 y 24. Los pacientes

convertidos a everolimus mostraron una ligera disminución en PWV (mes 12: -

0.24 m/s; mes 24: -0.03 m/s) mientras que los pacientes tratados con

ciclosporina se objetivó un aumento progresivo de la PWV (mes 12: 0.11 m/s;

mes 24: 0.16 m/s). Aunque la diferencia no fue significativa, se podría

argumentar que los valores basales estaban en el rango normal (promedio 7.8

m/s para grupo everolimus y 7.6 m/s para grupo ciclosporina). El seguimiento a

24 meses ha confirmado el valor predictivo de la PWV, ya que la incidencia de

eventos vasculares en toda la cohorte fue baja (2.8% en el grupo everolimus y

4.8% en el grupo ciclosporina). En una población de bajo riesgo de este tipo, es

necesario un número mayor de pacientes para mostrar cualquier beneficio en

un parámetro cardiovascular (o PWV) a partir de cualquier intervención

terapéutica (tal como una conversión a iMtor). Además, ya que tales pequeñas

variaciones (0.4-0.5 m/s) normalmente ocurren en un largo plazo de tiempo, el

seguimiento a 24 meses fue probablemente insuficiente para poder detectar un

cambio significativo en la PWV.93, 94 Puesto que los pacientes con una alta

PWV inicial son susceptibles de un aumento más elevado en la PWV 9 no se

puede excluir la posibilidad de que una conversión a iMtor sea beneficiosa para

esos pacientes.


32

4.3 Inhibidor de la señal de la coestimulación: belatacept.

La necesidad de nuevos fármacos que tengan la misma eficacia anti-rechazo

de los CNIs y/o iMtor pero con un mejor perfil de seguridad ha sido el empuje

para el desarrollo del belatacept.

La activación y la proliferación de los linfocitos T se basa en la interacción entre

el receptor de la célula T (TCR) con el conjunto antígeno + complejo mayor de

histocompatibilidad (MHC) de las células presentadoras de antígeno (APC).

Esta interacción, conocida como señal uno, es fundamental en la activación del

linfocito T pero no suficiente, siendo necesaria otra interacción no antígeno

especifica conocida como señal dos o señal de la coestimulación. La molécula

CD28, expresada en la superficie del linfocito T, reconoce las moléculas CD80

y/o CD86 de la APC. La activación del linfocito depende de estas dos señales.

CTLA4 es una molécula de superficie presente en linfocitos reguladores y en

linfocitos activados cuya función es competir con CD28 en la interacción con

CD80 y CD86 y, por esta razón, su función global es de inhibición de la

respuesta inmune. Abatacept es una proteína de fusión entre una IgG humana

y la porción extracelular del CTLA4 y es una de las opciones terapéuticas en la

artritis reumatoide y en la psoriasis. Sin embargo, en el trasplante renal el

abatacept se ha demostrado poco eficaz, por lo menos a nivel experimental. 95

La modificación del abatacept a través de la substitución de dos aminoácidos

(L104 à E y A29 à Y) ha aumentado su avidez por el receptor, en dos veces

hacia el CD80 y en cuatro veces hacia el CD86, siendo la capacidad inhibitoria

sobre los linfocitos T diez veces más potente.96 La molécula LEA29Y, también

conocida como Belatacept, fue aprobada como inmunosupresor para la

profilaxis del rechazo agudo del trasplante renal por la Food and Drugs

Administration en 2011, tras conocerse los resultados de dos ensayos clínicos

randomizados de fase III.97, 98

El estudio BENEFIT incluyó pacientes de bajo riesgo inmunológico y receptores

de un trasplante renal de novo procedente de un donante de criterios estándar

(SCD). En el estudio los pacientes se seleccionaron aleatoriamente y se

repartieron en 3 grupos: grupo 1 tratado con Belatacept, con un régimen de


33

suministro menos frecuente (grupo LI); grupo 2 tratado con Belatacept con un

régimen de suministro más frecuente (Grupo MI); grupo 3 tratado con

ciclosporina. Todos los pacientes recibieron inducción con Basiliximab y

tratamiento de mantenimiento con micofenolato mofetilo y prednisona. A 12

meses, la media de eGFR fue de 65 ml/min, 63.4 ml/min y 50.4 ml/min para los

grupos MI, LI y ciclosporina respectivamente (p < 0.0001 para cada grupo

belatacept comparado con Ciclosporina). La incidencia de rechazo agudo fue

mayor en los pacientes tratados con belatacept (27 % MI, 10 % LI y 7 %

ciclosporina). Todos los rechazos ocurrieron durante los primeros 6 meses,

siendo celulares en la totalidad de los casos. Estos excelentes resultados sobre

la evolución del filtrado glomerular fueron confirmados a 60 meses y a 84

meses de seguimiento. 99, 100 A los 7 años, la media del eGFR corregido por

superficie corporal seguía siendo mayor en los dos grupos belatacept con

respecto al grupo ciclosporina (70.4 y 72.1 ml/min por MI and LI vs 44.9 ml/min

p. < 0.0001). Además, se observó un reducción del objetivo combinado riesgo

de mortalidad y de pérdida del injerto renal del 43 % con el uso de belatacept

frente a ciclosporina (HR 0.57 (95% CI, 0.35–0.95); P=0.02 para MI vs

ciclosporina y 0.57 (95% CI, 0.35–0.94); P=0.02 para LI vs ciclosporina),

aunque la diferencia por cada evento analizado separadamente no fue

estadísticamente significativa.100

El estudio BENEFIT-EXT98 investigó el uso de belatacept en pacientes

receptores de un trasplante renal procedente de un donante de criterios

expandidos (ECD). El protocolo fue idéntico al del estudio BENEFIT,

comparándose también 3 grupos de pacientes (MI – LI y Ciclosporina). A los 12

meses, el grupo MI tenia función renal mejor que el grupo ciclosporina (52.1

ml/min vs 45.2 ml/min P= 0.008) mientras que no hubo diferencias significativas

entre el grupo LI y el grupo ciclosporina. La tasa de rechazo agudo fue similar

en los 3 grupos (17.9 %, 17.1 % 14.1 % para MI, LI y Ciclosporina

respectivamente).98 A 84 meses de seguimiento, la función renal se mantenía

significativamente mejor en los dos grupos tratados con belatacept (filtrado

glomerular ajustado por superficie corporal 53.9 ml/min vs 54.2 ml/min vs 35.3

ml/min P< 0.001). No se objetivaron diferencias significativas en la

supervivencia del injerto y/o del paciente entre los dos grupos.101


34

Recientemente han sido publicados los resultados a 36 meses de un estudio

de fase II sobre la conversión de CNI (ciclosporina y/o tacrolimus) a

belatacept.102 Los pacientes convertidos a belatacept presentaron una mejora

estimada en el eGFR de 1.90 ml/min/1.73 m2 por año (95 % CI 0.89-2.92)

mientras que los que mantenían tratamiento con CNI tuvieron una mejora de

tan solo 0.07 ml/min/1.73m2 por año (95 % CI 20.96 – 1.09). La pendiente de

las curvas de eGFR se separó de manera significativa entre los dos grupos de

tratamiento durante todo el tiempo del estudio (P= 0.01 per interacción tiempo-

tratamiento). No hubo diferencias significativas en la tasa de rechazo agudo

entre los dos grupos. 102

El aumento precoz del filtrado glomerular demostrado por estos estudios puede

imputarse a la ausencia de vasoconstricción debida al uso de CNI. Más allá de

este mecanismo puramente hemodinámico, el aumento del eGFR a largo plazo

apunta a que el uso de belatacept pueda obviar el daño vascular crónico

mediado por CNI, por lo menos a nivel renal. 103

Sobre los factores de riesgo cardiovascular, el belatacept parece ser superior a

los CNI. A los 12 meses, la presión arterial sistólica y diastólica eran más bajas

en pacientes tratados con belatacept con respecto a los tratados con

ciclosporina, aunque todos los grupos tenían el mismo nivel inicial de presión

arterial.97 La presión arterial sistólica media resultó ser inferior de 5-6 mmHg y

de 8-10 mmHg para los pacientes de los grupos belatacept vs los tratados con

ciclosporina en los ensayos BENEFIT y BENEFIT-EXT respectivamente.

También la presión arterial diastólica media resulto inferior de 2 mmHg en el

estudio BENEFIT y de 4-5 mmHg en estudio BENEFIT-EXT a 24 meses.104

Además, en el ensayo BENEFIT, ambos regímenes de belatacept (MI y LI) se

asociaban con una reducción del 30% en la probabilidad de requerir un mayor

número de fármacos antihipertensivos al mes 12 (P=0.02 LI vs. ciclosporina).105

A dos años, el perfil lipídico de los pacientes tratados con belatacept mejoró en

comparación con la ciclosporina.104 En el ensayo BENEFIT, a 12 meses, se

observó un aumento en los valores de colesterol no HDL que fue

significativamente mayor en el grupo ciclosporina comparado con los demás

regímenes (18.3 ± 2.8 mg/dl en el grupo ciclosporina, 8 ± 2.8 y 8.1 ± 2.8 mg/dl

en MI y LI, p. 0.01 para ambos vs ciclosporina). Los niveles de triglicéridos a 12


35

meses disminuyeron en los dos grupos belatacept (-17.1 ± 7 mg/dL y –21 ± 6.9

mg/dL por MI y LI respectivamente), mientras que aumentaron en el grupo

ciclosporina (+6.6 ± 6.9 mg/dL – P= 0.01 y P= 0.004 para MI y LI vs

ciclosporina).97

En ambos estudios, BENEFIT y BENEFIT-EXT, la incidencia de diabetes post

trasplante (NODAT) fue menor para los grupos tratados con belatacept aunque

no estadísticamente significativa.104 Un reciente meta-análisis mostró que la

incidencia de NODAT fue inferior con belatacept a 12 meses con respecto a los

CNI (4 ensayos clínicos, 1516 pacientes, OR=0.43, CI 0.24-0.78, P=0.006,

índice de heterogeneidad=18%).106

Recientemente, el uso del abatacept en pacientes con artritis reumatoide se ha

relacionado con una reducción de eventos cardiovasculares con respecto a

otros fármacos,107 aunque el abatacept no parece tener un efecto protector

sobre la rigidez arterial, probablemente debido a su ineficacia para disminuir la

inflamación sistémica.108, 109

No hay ensayos con suficiente poder estadístico que hayan analizado en

detalle el posible efecto favorable del belatacept sobre eventos

cardiovasculares, ni tampoco estudios exploratorios que hayan evaluado la

relación entre rigidez arterial y belatacept, excepto los estudios publicados que

son parte de la presente tesis.


36


37

5. Hipótesis del trabajo

Belatacept es un nuevo fármaco inmunosupresor eficaz como terapia de

inducción y de mantenimiento en trasplante, a la vez que muestra un perfil

cardiovascular mucho más favorable que los CNIs y iMtor. La hipótesis de esta

tesis es que, en base al mecanismo de acción de belatacept, los pacientes

tratados con un régimen inmunosupresor basado en este fármaco, tendrían

una menor rigidez arterial que aquellos pacientes tratados con un régimen

basado en CNI, ya sea tacrolimus o ciclosporina.


38


39

6. Objetivos Nuestro objetivo general ha sido evaluar el impacto de un régimen de

inmunosupresión libre de CNI, basado en el uso de la inhibición de la señal de

coestimulación con belatacept, sobre la rigidez aórtica después de un

trasplante renal.

El objetivo principal es demostrar que los parámetros de rigidez arterial,

velocidad de la onda de pulso (PWV) y augmentation pressure (AP) son

inferiores en el grupo tratado con belatacept con respecto a pacientes tratados

con CNI (tacrolimus y/o ciclosporina).

Como objetivos secundarios se analizan las posibles relaciones entre los

parámetros de rigidez arterial y los siguientes factores:

- clínicos: posible relación entre rigidez arterial y variables clínicas;

- analíticos: relación entre rigidez arterial y datos de función renal,

proteinuria, perfil lipídico, metabolismo óseo-mineral (PTH y Calcemia);

- radiológicos: relación entre rigidez arterial e índices de resistencia intra-

renales (IRR) en el ecodoppler post-trasplante renal


40


41

7. Estudios publicados

7.1 Differential impact of belatacept and cyclosporine A on central aortic blood pressure and arterial stiffness after renal transplantation. Clin Transplant. 2014

El Augmentation pressure es inferior en pacientes tratados con

belatacept en comparación a pacientes tratados con ciclosporina110

Differential impact of belatacept andcyclosporine A on central aortic bloodpressure and arterial stiffness after renaltransplantation

Seibert FS, Steltzer J, Melilli E, Grannas G, Pagonas N, Bauer F,Zidek W, Griny!o J, Westhoff TH. Differential impact of belataceptand cyclosporine A on central aortic blood pressure and arterialstiffness after renal transplantation.

Abstract: Calcineurin inhibitors (CNI) are potent vasoconstrictors andinduce an acceleration of arteriosclerosis, thus contributing to thecardiovascular risk after renal transplantation. The study compares theimpact of belatacept and cyclosporine A (CsA) on arterial stiffness andcentral aortic blood pressure. We performed a case–control study in 46patients (23 on belatacept and 23 on CsA) matched for age, body massindex, time after transplantation, and time on dialysis prior totransplantation. Pulse wave analysis (SphygmoCor, AtCor!) was used toassess central aortic blood pressure, aortic augmentation pressure, andpulse wave velocity (PWV) as a marker of arterial stiffness. Assessment ofvascular function was performed after a minimum of 20 months and amedian follow-up of 81 months post-transplant. Peripheral systolic anddiastolic blood pressure did not significantly differ in the two groups(p > 0.05 each). The central aortic augmentation pressure was higher inthe CsA group (12.7 mmHg vs. 7.3 mmHg, p = 0.048). PWV as ameasure of arterial stiffness did not differ in the two groups. Thus,belatacept is not associated with a significant difference in arterialstiffness compared to CsA after a median of 81 months post-transplant.It is associated, however, with a lower aortic augmentation pressure, astrong independent cardiovascular risk factor.

Felix S. Seiberta,b, Julia Steltzerb,Eduardo Melillic, Gerrit Grannasd,Nikolaos Pagonasa,b, FredericBauera,b, Walter Zidekb, JosepGriny!oc and Timm H. Westhoffa,b

aMedizinische Klinik I, Universit€atsklinik

Marienhospital, Ruhr-University Bochum,

Herne, Germany, bDepartment of Nephrology,

Charit!e – Campus Benjamin Franklin, Berlin,cDepartment of Nephrology, Hospital

Universitari de Bellvitge, Barcelona, Spain anddDepartment of Surgery and Transplantation,

University of Hannover, Hannover, Germany

Key words: arterial stiffness – augmentation

pressure – belatacept – calcineurin

inhibitor – renal transplantation

Corresponding author: Prof. Dr. med. Timm H.

Westhoff, Medizinische Klinik I,

Universit€atsklinik Marienhospital Herne,

Ruhr-University Bochum, H€olkeskampring 40,

44625 Herne, Germany.

Tel.: +49 2323 499 1671;

fax: +49 2323 499 302;

e-mail: timm.westhoff@marienhospital-herne.

de

Conflict of interest: None.

Accepted for publication 22 June 2014

End-stage renal disease (ESRD) is associated withan excessively increased cardiovascular risk. Kid-ney transplantation ameliorates the risk comparedto patients on the waiting list (1), but cardiovascu-lar morbidity and mortality remain substantiallyincreased compared to the general population.Thus, cardiovascular events are the leading causeof death and constitute one of the leading reasonsof graft failure (1, 2). In this context, the deleteri-ous effects of calcineurin inhibitors (CNI) on arte-rial function are of relevance. CNIs are bothpotent vasoconstrictors (acute CNI toxicity) and

promoters of intravascular fibrosis leading toobliterative arteriolopathy (chronic CNI toxicity).These effects lead to an increase of arterial stiffness,an independent predictor of cardiovascular events.Several authors have described the devastatingimpact of cyclosporine A (CsA) on arterial stiff-ness, as measured by augmentation index andpulse wave velocity (PWV) (3–6).

Due to the nephrotoxic side effects of CNI,there is an ongoing search for alternative immu-nosuppressants with less deleterious long-termeffects on renal function. Recently, belatacept, a

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© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Clin Transplant 2014: 28: 1004–1009 DOI: 10.1111/ctr.12413 Clinical Transplantation

costimulation inhibitor, has been approved forrenal transplant recipients. The BENEFIT studydemonstrated a preservation of renal functioncompared to a CsA-based immunosuppressiveregimen (7). Moreover, belatacept was associatedwith less hypertension, hyperlipidemia, and new-onset diabetes (NODAT, pooled analysis ofBENEFIT and BENEFIT-EXT) (8). Asdescribed above, the nephrotoxicity of CsA ispredominantly based on vascular damage. Withregard to these findings of the BENEFIT study,it may be postulated that belatacept has less del-eterious effects on arterial function compared toCsA. Attempts have been made to measure theextent of arteriosclerotic wall changes in a stan-dardized non-invasive manner. Computerizedpulse wave analysis has provided several param-eters that mirror arterial stiffness including PWVand augmentation index. These parameters areindependent predictors of cardiovascular mortal-ity in patients with impairment of renal function(9).

As described above, CsA is a strong vasocon-strictor that may contribute to post-transplanthypertension. In the BENEFIT study, belataceptdid not increase brachial blood pressure to thesame extent. The CAFE study indicated that cen-tral aortic pressure might be a better predictor ofcardiovascular risk than brachial blood pressure(10). The central aortic blood pressure is a compos-ite of the antegrade pressure wave induced by theejected blood volume and a retrograde pressurewave induced by reflection at the peripheral arter-ies (11). The augmentation pressure represents theaugmentation (mmHg) in central systolic pressuredue to the rejected wave (Fig. 1). In healthy young

subjects, the augmentation pressure is very low,whereas it may be substantially increased in elderlysubjects with a high level of arteriosclerosis (Fig. 1)(12, 13). To date, there are no data on the impactof belatacept on central aortic blood pressure aug-mentation.The present case–control study investigates the

differential effects of belatacept and CsA on arte-rial stiffness and central aortic blood pressure.Arterial stiffness and central aortic blood pressurewere assessed in 23 patients on belatacept and 23patients on CsA matched for age, BMI, time aftertransplantation, and time on dialysis prior totransplantation.

Patients and methods

Study population and protocol

Patients were recruited from transplant centers inGermany and Spain (Berlin, Hannover, Barce-lona). For reasons of comparability of pulsewave analysis, bilateral fistula was regarded asan exclusion criterion. Inclusion criteria werewritten informed consent for participation, suc-cessful renal transplantation >18 months ago,and an immunosuppressive triple regimencontaining mycophenolic acid (MPA), steroids,and either belatacept or CsA. Transplantation<18 months ago was defined as exclusion crite-rion, because we have previously shown thatchanges in pulse wave properties may have avariable character in the first month after trans-plantation (14). Moreover, repeated renal trans-plantation was defined as an exclusion criterion.Approval for the study was obtained from the

Fig. 1. Exemplary illustration of pulse waves with regular vs. reduced arterial compliance. Due to a shorter transit time, the reflectedpulse wave shifts towards the forward wave and thus augments aortic pressure in case of increased arterial stiffness.

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Belatacept and arterial function

Ethical Committee of the Charit!e – Univer-sit€atsmedizin Berlin. Participants underwent anon-invasive assessment of brachial blood pres-sure, central aortic blood pressure, and arterialstiffness as measured by PWV.

Assessment of PWV, aortic blood pressure, andaugmentation pressure by the SphygmoCor device

Measurements were conducted in a quiet clinicalresearch laboratory at a constant ambient temper-ature of 20 to 22°C between 12 and 2 p.m., atleast three h and on average four to six h afteringestion of CNI as published previously (15, 16).Since CNI levels might acutely influence arterialelasticity, all the measurements were performed atthis defined span of time to assure comparabilityof results. Patients were resting in a supine posi-tion for 15 min before the measurement proce-dure was started. Measurements were performedin the same session. Brachial blood pressure wasmeasured oscillometrically. Applanation tonome-try was performed using a SphygmoCor device(AtCor Medical!, Sydney, NSW, Australia) asrecommended (17). In brief, recording of radialpressure waveforms was performed by a high-fidelity micromanometer placed on the tip of ahandheld tonometer (Millar Instruments!, Hous-ton, TX, USA), which was gently applied to thesurface of the skin overlying the radial artery atthe non-fistula arm. Pulse waves were recordedfor 12 s. In accordance with the manufacturer’srecommendations, several recordings were takenif needed to accomplish recommended qualitycontrol criteria, namely a quality index ≥80%.Transformation of peripheral pressure waveformswas performed by means of a generalized transferfunction (18), which had been previously vali-dated using intra-arterially measured pressurewaves (19). Calibration of the recorded pressurewaveforms was carried out using the brachial sys-tolic and diastolic blood pressure values. Aug-mentation pressure represents the augmentation(mmHg) in central systolic pressure due to thereturn of the reflected wave at the aorta (Fig. 1).PWV was calculated from measurements of pulsetransit time and the distance travelled betweentwo recording sites as “PWV = distance/transittime.” An electrocardiogram (ECG) was used todetermine the start of the pulse wave. The meanof 12 s of tonometer recorded pulse waves at theradial and carotid artery was used to determinethe arrival of the pulse wave at the peripheralrecording site (aortic PWV). The distance wasmeasured between the recording sites and thesuprasternal notch. The mean value of three

consecutive measurements was used for statisticalanalysis.

Statistical analysis

Data are presented as median and interquartilerange. Intergroup differences in numeric parame-ters were analyzed by Wilcoxon–Mann–WhitneyU-test. Comparison of dichotomic categoricalparameters was made by Fisher’s exact test.p < 0.05 was regarded statistically significant. Allstatistical analyses were performed using PASWStatistics 21.0 (SPSS Inc., Chicago, IL, USA).

Results

Forty-six patients were enrolled in the study (41cadaveric grafts, five live donor transplantations).Twenty-three participants were on a belatacept-based regimen, 23 participants on a CsA-basedregimen. Epidemiological information, data ontransplantation and graft function, cause ofESRD, concomitant diseases as well as distributionof antihypertensives and statins are presented inTable 1. The predominant cause of end-stage renalfailure was glomerulonephritis followed by poly-cystic kidney disease. Pulse wave analysis was suc-cessful in all the patients. The two groups showedno significant differences with regard to gender dis-tribution, age, BMI, time on dialysis prior totransplantation, and time since transplantation.There were four live donor transplantations in theCsA group and one in the belatacept group(p = 0.35). EGFR (calculated by the ChronicKidney Disease Epidemiology Collaboration[CKD-Epi] formula (20)) tended to be higher in thebelatacept group (59 mL/min/1.73 m2 vs. 54 mL/min/1.73 m2, p = 0.057). Presence of concomitantdiseases including hypertension, diabetes, cardio-vascular events, and tobacco use was not signifi-cantly different in the two groups (p > 0.05 each),except for hyperlipoproteinemia, which occurredmore often in the CsA group (p = 0.029).

Table 2 summarizes the measured vascularparameters. Systolic brachial blood pressure wasnumerically higher in the CsA group withoutreaching significance (137 mmHg vs. 128 mmHg,p = 0.68). Diastolic brachial blood pressure valuesdid not statistically differ in the two groups(78 mmHg vs. 77 mmHg, p = 0.90). The use ofbeta-blockers and calcium channel blockers tendedto be higher in CsA patients (p = 0.071 each).Heart rate was significantly higher in belataceptpatients (62.3 bpm vs. 71.7 bpm, p = 0.003). PWVas a marker of arterial stiffness was identical in thetwo groups (8.8 m/s vs. 8.8 m/s, p = 0.78). The

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aortic augmentation pressure was significantlylower in belatacept patients (12.7 mmHg vs.7.3 mmHg, p = 0.048) and the systolic aorticpressure tended to be lower in these patients(125.5 mmHg vs. 114.3 mmHg, p = 0.22).Diastolic aortic blood pressure was numericallylower in belatacept patients without reaching sta-tistical significance (77.3 mmHg vs. 74.7 mmHg,p =0.78).

Discussion

The BENEFIT study indicated a favorable cardio-vascular profile of belatacept compared to CsAincluding a significantly lower blood pressure ofthe brachial artery and a lower intake of antihyper-tensive drugs (7). To date, there are no data oncentral aortic blood pressure, an independent riskmarker, that may be of stronger predictive rele-vance for cardiovascular events than brachialblood pressure (10). Moreover, it is unknownwhether the improved cardiovascular side effectprofile translates into a measurable benefit in arte-rial stiffness. The present study provides these datafor the first time. Our findings reveal no differencein arterial stiffness as measured by PWV after amedian of 81 months post-transplant. There was,however, a significantly lower central aortic aug-mentation pressure in belatacept compared toCsA. Augmentation pressure in comparison withPWV reflects not only arterial stiffness but thetonus of small arterial vessels, which has an impor-tant impact on the reflected pulse wave.In the BENEFIT/BENEFIT-EXT trials,

patients on belatacept had a significantly lowerincidence of new-onset diabetes after transplanta-tion (NODAT), lower serum lipids, lower periph-eral blood pressure, and a higher eGFR. Thepresent study confirms the data on hyperlipidemia.As described above, the nephrotoxicity of CsA ispredominantly based on vascular damage. Thus,how can it be explained that the use of belataceptdid not lead to a benefit in arterial stiffness in ourstudy? Arterial stiffness is regarded as a footprintof vascular aging, and PWV is a well-established

Table 1. Epidemiological and renal data of the study population

Cyclosporine Belatacept p

Epidemiological and renal dataNumber of subjectsincluded

23 23

Male (%) 16 (69.6) 18 (78.3) 0.74Female (%) 7 (30.4) 5 (21.7)Age (yr) 55 (49–64) 54 (49–62) 0.72Body mass index(kg/m2)

25.9 (23.4–27.9) 24.5 (21.8–27) 0.22

Live donortransplantation

4 1 0.35

Time onhemodialysis(months)

51 (15–85) 43 (7–84) 0.5

Time sincetransplantation(months)

92 (43–120) 77 (70–125) 0.77

eGFR(mL/min/1.73 m2)

54 (42–60) 59 (50.4–85.4) 0.057

Cause of end-stage renal disease (%)Glomerulonephritis 4 (17.4) 7 (30.4)Polycystic kidneydisease

4 (17.4) 5 (21.7)

Nephrosclerosis 3 (13) 2 (8.7)Diabetic nephropathy 1 (4.4) 1 (4.4)Interstitial nephritis 2 (8.7) 2 (8.7)Alport syndrome 0 (0) 1 (4.4)Hereditary dysplasia/reflux

4 (17.6) 1 (4.4)

Amyloidosis 1 (4.4) 1 (4.4)Maligne hypertension 1 (4.4) 1 (4.4)Unknown 3 (13) 2 (8.7)Concomitant diseases (%)Hypertension 23 (100) 20 (87) 0.23Diabetes mellitus 4 (17.4) 2 (8.7) 0.67Cardiovascularevents

5 (21.7) 5 (21.7) 1.0

Hyperlipoproteinemia 19 (82.6) 11 (47.8) 0.029

Use of tobacco 8 (34.8) 15 (65.2) 0.08Antihypertensives and statins (%)Calcium channelblockers

17 (73.9) 10 (43.5) 0.07

ACE inhibitors/ARB 9 (39.1) 14 (60.9) 0.24Beta-blockers 17 (73.9) 10 (43.5) 0.07Statins 9 (39.1) 10 (43.5) 1.00

Numeric data are presented as median with interquartile range and weretested for statistically significant differences by Wilcoxon–Mann–WhitneyU-test. Categorical parameters (gender, live donation) were comparedby Fisher’s exact test. p < 0.05 was regarded statistically significant(bold type).

Table 2. Comparison of vascular parameters of patients with cyclo-sporine A and belatacept

Cyclosporin A Belatacept p

Peripheral systolicblood pressure(mmHg)

137 (121–147) 128 (116–152) 0.68

Peripheral diastolicblood pressure(mmHg)

78 (65–83) 77 (62–90) 0.90

Aortic systolicpressure (mmHg)

125.5 (108.3–132) 114.3 (102–132) 0.22

Aortic diastolicpressure (mmHg)

77.3 (66–83) 74.7 (61.7–91) 0.78

Augmentationpressure (mmHg)

12.7 (8.3–16) 7.3 (2.3–11.7) 0.048

Heart rate (bpm) 62.3 (55.3–67.3) 71.7 (63.3–78) 0.003

Pulse wavevelocity (m/s)

8.8 (8.1–9.5) 8.8 (7.7–9.7) 0.78

Numeric data are presented as median with interquartile range and weretested for statistically significant differences by Wilcoxon–Mann–WhitneyU-test. p < 0.05 was regarded statistically significant (bold type).

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cardiovascular risk marker in subjects withimpaired renal function (5, 9, 21). As the progres-sion of arteriosclerosis is massively accelerated inuremia, it is not surprising that successful renaltransplantation has been shown to reduce arterialstiffness (2, 4, 6). Nevertheless, arteriosclerosis is achronic process developing over the years and dec-ades. A potential explanation for the lacking differ-ence in PWV in our study is that the period of sixto seven yr of treatment with either belatacept orCsA is too short to reveal a measurable effect onthe extent of arteriosclerosis. Prior studies haveshown that pulse wave analysis is indeed able todetect differential effects of immunosuppression onarterial function after renal transplantation (16).The immunosuppressive regimen had a differen-

tial effect on blood pressure. In contrast to CsA,belatacept has no vasoconstrictive properties. Ourstudy confirms the results on peripheral bloodpressure. The lack of statistical significance in sys-tolic brachial blood pressure may be attributed tothe small study size. In addition to the effect onperipheral blood pressure, the present study revealsa significant differential effect on aortic augmenta-tion pressure for the first time. CsA is known toincrease aortic pressure augmentation due to itsvasoconstrictive and proarteriosclerotic properties.Ferro and coworkers assessed the contribution ofseveral classical and non-classical cardiovascularrisk factors on aortic pressure augmentation inrenal transplant recipients. The presence of CsA inthe immunosuppressive regimen significantly con-tributed to an increase in pressure augmentation(3). This study made use of the same pulse waveanalysis system (AtCor!) as used in our study.CsA has various vasoactive effects. On the onehand, CsA has a short-term modulating effect andameliorates arterial tone shortly after ingestion(22): this can be explained rather by the vitaminE-containing diluents vehicle (e.g., Neoral!; Nov-artis, Basel, Switzerland) than by CsA itself. There-fore, we chose to avoid measurements early afteringestion as described above. On the other hand,CsA leads to a reduced production of vasodilators(prostaglandins and nitric oxide) and enhancedrelease of vasoconstrictors (endothelin and throm-boxane) (23–25). Moreover, CsA causes anincrease of free reactive oxygen species (26) andmay increase sympathetic tone (27). CsA comparedto belatacept necessitates the use of more antihy-pertensive drugs including beta-blockers (7). Theresulting lower heart rate in CsA patients contrib-utes to the increase in augmentation pressure.Augmentation pressure is determined by the cumu-lative influence of structural hemodynamic

properties of peripheral vessels. This augmentedpressure translates into an increased cardiac work-load, thereby resulting in adverse cardiovascularevents. An increase of augmentation pressure isassociated with, for example, poor renal function(28, 29), worse arterial stiffness in diabetes (30, 31),leads to cardiovascular events in hypertension (10,12), and has devastating effects in patients withcoronary artery disease – in this case with even acalculated increase of nearly 20% mortality every10 mmHg augmented pressure (32). In the above-mentioned CAFE trial cohort, central pulse pres-sure was significantly associated with a compositeoutcome of total cardiovascular events and devel-opment of renal impairment (10).

The study is limited by the low sample size. Thesample size was sufficient, however, to detect a sig-nificant difference in augmentation pressure. Be-latacept was approved for renal transplantation in2011 in Europe. Hence, there are very few patientsusing belatacept for a longer period. Almost all ofthem have been study participants in phase II andIII trials. Twenty-three patients was the maximumnumber of patients that could be included in thethree large transplant centers of Berlin, Hannover,and Barcelona. With regard to the slowly progres-sive course of vascular calcification, we refrainedfrom including patients using belatacept for<1.5 yr. Since there is currently no further de novostudy, the present results will probably constitutethe largest study on this issue for the near future.

In summary, the present findings show that be-latacept is associated not only with a lower periph-eral blood pressure but also with a lower aorticaugmentation pressure as a strong marker of car-diovascular risk compared to CsA. There is no sig-nificant difference, however, in arterial stiffnessafter seven yr of immunosuppression.

Authors’ contributions

Felix S. Seibert: Participated in performance ofresearch, data analysis, and writing the manu-script; Julia Steltzer, Eduardo Melilli, Gerrit Gran-nas, Nikolaos Pagonas, and Frederic Bauer:Participated in performance of research; WalterZidek and Josep Grinyo: Participated in researchdesign and reviewed the manuscript; Timm H.Westhoff: Involved in research design, data analy-sis, and writing the manuscript and contributed theidea.

Sources of financial support

Bristol-Myers Squibb supported the study.

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Seibert et al.

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48

7.2. Arterial stiffness in kidney transplantation: a single center case-control study comparing belatacept versus calcineurin inhibitor immunosuppressive based regimen. Nefrología. 2015

Después del trasplante renal la prevalencia de tener la PWV dentro

de la normalidad es mayor en pacientes tratados con un régimen de

inmunosupresión basado en belatacept en comparación con un

grupo de pacientes tratados con CNI (prevalentemente con

tacrolimus). El uso de belatacept es factor predictor independiente

de tener una PWV normal conjuntamente con la edad del receptor y

la presión arterial sistémica.59

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originalshttp://www.revistanefrologia.com

© 2015 Revista Nefrología. Official Publication of the Spanish Nephrology Society

Correspondence: Edoardo MelilliDepartamento de Nefrología y Trasplante Renal. Hospital Universitari de Bellvitge. L’Hospitalet de Llobregat, [email protected]@yahoo.it

ABSTRACT

Arterial stiffness is nowadays a well-accepted predictor of car-diovascular mortality in general population; as well as in kidney transplant recipient population. The femoral-carotid pulse wave velocity (cf-PWV) is the widest used method to assess the arterial stiffness. The aim of this study was to test whether CNI-free im-munosuppression based on belatacept was associated with lower cf-PWV, as a surrogate marker of arterial stiffness, than CNI. This was a retrospective case-control study. We included all the cas-es treated with belatacept as a maintenance immunosuppression in our center (n=20). An appropriate control group of patients (n=20) treated with CNI was selected to achieve match for key factors associated with arterial stiffness. After a follow-up of 5 years after transplantation, the Belatacept group had a reduced prevalence of patients with a cf-PWV higher than 8.1m/s (50% in BLC vs. 25% in CNI, p=0.08). At multivariate logistic regression analysis, the risk of high cf-PWV was correlated with age (OR 1.24; p<0.03) and renal resistive index (OR 1.25; p<0.05). Belatacept treat-ment was associated with a significant reduction in risk of cf-PWV (OR 0.008; P=0.045). Belatacept-based maintenance immunosup-pression could improve kidney transplant recipient’s survival by reducing cardiovascular events related to stiffness.

Keywords: Belatacept. Arterial stiffness. Calcineurin inhibitors.Pulse wave velocity. Renal transplantation.

Arterial stiffness in kidney transplantation: a single center case-control study comparing belatacept versus calcineurin inhibitor immunosuppressive based regimenEdoardo Melilli, Oriol Bestard-Matamoros, Anna Manonelles-Montero, Neus Sala-Bassa, Richard Mast, Josep M. Grinyó-Boira, Josep M. CruzadoDepartamento de Nefrología y Trasplante Renal. Hospital Universitari de Bellvitge. L’Hospitalet de Llobregat, Barcelona

Nefrologia 2015;35(1):58-65doi:10.3265/Nefrologia.pre2014.Sep.12615

Endurecimiento arterial en el trasplante renal: estudio caso-control en un único centro para la comparación de un tratamiento inmunosupresor con belatacept frente a uno con inhibidores de la calcineurina RESUMENActualmente, el endurecimiento arterial se considera un buen indicador de mortalidad cardiovascular tanto en la población general como en receptores de trasplantes de renales. Para cuantificarlo, el método más empleado es la medición de la velocidad de onda del pulso carótido-femoral (VOPcf). El objetivo de este estudio es analizar si un tratamiento inmunosupresor con belatacept, sin inhibidores de la calcineurina (ICN), se asocia a una VOPcf (como marcador alternativo del endurecimiento arterial) menor que la asociada a un tratamiento con ICN. Se trata de un estudio retrospectivo caso-control, en el que incluimos todos los casos que recibieron un tratamiento inmunosupresor de mantenimiento con belatacept en nuestro centro (n=20). Para estos, seleccionamos un grupo de controles adecuado (n=20), que había recibido un tratamiento con ICN y con idénticos factores clave asociados al endurecimiento arterial. Tras el seguimiento llevado a cabo durante los 5 años posteriores al trasplante, la prevalencia de pacientes con una VOPcf superior a 8,1 m/s se había reducido en el grupo al que se le administró belatacept (50% en el grupo BLC frente al 25% en el grupo ICN, p = 0,08). El análisis de regresión logística multivariante reveló que el riesgo de presentar una VOPcf alta se encontraba correlacionado con la edad (OR: 1,24; p < 0,03) y el índice de resistencia renal (OR: 1,25; p < 0,05). El tratamiento con belatacept se asoció a una reducción significativa del riesgo de aumentar la VOPcf (OR: 0,008; p = 0,045). La inmunosupresión de mantenimiento con belatacept podría favorecer la tasa de supervivencia de receptores de trasplantes renales gracias a la disminución de los eventos cardiovasculares relacionados con el endurecimiento arterial.Palabras clave: Belatacept. Endurecimiento arterial. Inhibidores de la calcineurina. Velocidad de onda del pulso. Trasplante renal.

risk in the clinical setting, such as arterial stiffness, which is an artery-ageing indicator as well. An increase on the stiffness causes an increase of the intra aortic pressure, which, at the microcirculation level, damages several organs like the kidneys.2 Among some surrogate measurements of the arterial stiffness, the carotid-femoral pulse wave velocity (cf-PWV) is considered an accurate index for cardiovascular risk assessment in various pathological conditions, including patients with chronic kidney disease (CKD), end-stage renal disease (ESRD)3 and kidney transplantation.4 The cf-PWV

INTRODUCTION Cardiovascular disease and cancer remain the leading causes of mortality among kidney allograft recipients.1 There are some potential surrogate markers for assessing the cardiovascular

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performed during the first half of 2011. At this time, 24 renal allograft recipients were being treated with belatacept (BLC) as maintenance immunosuppression. As control group, we performed an individual matching (one by one) identifying in our database 26 renal allograft recipients treated with CNI during the whole the post transplant follow-up (CNI) and matched for the most important determinants of cf-PWV, which are blood pressure (the same number of medications, maximum accepted systolic and diastolic pressure difference of 5mmHg between each case and his and control, at the time of the PWV test), age (maximum accepted difference of 5 years between each case and his control), gender (matching), time since transplantation (maximum accepted difference of 6 months between each case and his control), time in dialysis (maximum accepted difference of 3 months between each case and his control), body max index (BMI – maximum accepted difference of 1kg/m2 between each case and his control) and cause of nephropathy (matching).6,13 All the patients of the two groups had given an informed consent. All the BLC patients were participants in Benefit and Benefit extended trial at our center.

Pre- and post-transplant clinical, demographic and laboratory data were obtained from patient’s charts. Inclusion criteria were renal transplantation, treatment with belatacept or CNI and informed consent. Patients were excluded from the study if there was any change in type of maintenance immunosuppression after transplantation, or they had atrial fibrillation, severe obesity (BMI >35kg/m2) and previous vascular interventions on the aorta.

Renal measurements Graft function was assessed by an estimated glomerular filtration rate (eGFR) calculated as a MDRD formula. Proteinuria was assessed by protein/creatinine ratio and expressed as g/mol. All blood analytic tests were performed between 30 and 7 days before the hemodynamic and arterial stiffness measurements.

All patients were submitted to a standard kidney graft sonography between three and six months since transplantation. All Doppler examinations were performed by three experienced sonographers with an Anteres® machine (Siemens), equipped with 2.5-4Mhz micro-convex-array transducer (CH4-1 Transducer Siemens). For each patient, after the visualization of three segmental arteries, the Doppler spectrum was recorded and analyzed. During the examination, patients were asked to refrain from forced inspiration since this could modify the intra-abdominal pressure. The peak systolic velocity (Vmax) and end diastolic velocity (Vmin) were measured; the kidney segmental arterial resistive index (RRI) was calculated as [RI=1⁄4 1-(Vmin/Vmax)]. For statistical purposes the mean RRI of the three areas explored was used.

is related with age and with other cardiovascular risk factors such as arterial pressure,5 inflammation6,7 and vascular calcifications.8 However, its relationship with some classical atherosclerosis indicators, such as lipoproteins and carotid non-calcified plaques is rather low.9,10 Therefore, cf-PWV has emerged as an important predictor of cardiovascular mortality.

Regarding CKD population, there is lack of data analyzing whether kidney transplantation is capable to reduce or delay the progression of the arterial stiffness.11 The deleterious effect caused by calcineurin inhibitors (CNI) (especially cyclosporine) on endothelial cells is mainly supported by experimental studies.12 However, clinical evidence about the CNI stiffening effect in the arterial structure is quite limited13 and even controversial.14-16 Concerning mammalian target of rapamycin inhibitors (mTORi), sirolimus seems to be capable to delay the progression of arteriosclerotic injuries,17,18 whereas everolimus inhibits the fibrotic process in some tissues.19 Some authors suggest that patients treated with mTORi show a lower arterial stiffness (lower pulse wave velocity) than patients treated with CNI,20,21 although others do not agree with that conclusion.22 On the other hand, up to now any treatment is able to increase the arterial elasticity without reducing the arterial pressure4, at least in the clinical setting. Moreover, the reduction of arterial pressure caused by antihypertensive agents is associated with the reduction and/or slowing down of the progression of the arterial stiffness.23,24

The biologic immunosuppressant belatacept (BLC) is the result of a fusion between a common fragment Fc of human IgG and the CTL4 protein which, binding itself to the CD80 and CD86 receptors on antigen presenting cells (APC), inhibits co-stimulatory signals, which are essential in order to activate the T-lymphocyte. In two clinical trials recently published,25,26 belatacept has demonstrated an anti-rejection efficacy similar to cyclosporine. After a 3 years follow-up, patients treated with belatacept have shown better renal function, less renal fibrosis in protocol biopsy and a better cardiovascular profile.27 No data exist about the relationship between belatacept and arterial stiffness measured by cf-PWV.

In order to test whether a CNI-free immunosuppression based on belatacept is associated with a lower cf-PWV (as a surrogate marker of arterial stiffness) than CNI, we performed a retrospective case control study evaluating cf-PWV between a group of patients treated with belatacept (BLC) and a group treated with CNI (CNI).

MATERIALS AND METHODS Study population Bellvitge Hospital Institutional Review Board approved the study protocol. Pulse wave velocity measurements were

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Hemodynamic and arterial stiffness measurements Arterial pressure was measured, at the same time of the cf-PWV measurements, over the brachial artery three times at 5 minutes intervals with an oscillatory device (OMRON M6 Comfort HEM-7000-E). Data were presented as systolic pressure, diastolic pressure and pulse pressure (systolic – diastolic pressure). The status of arterial hypertension was defined by the use of antihypertensive medication and/or clinic blood pressure >140/90mmHg.

A unique operator (E.M.) performed the cf-PWV measurement in all patients during the morning in a quiet room, 3 hours after a light breakfast and after 30 minutes at rest. Aortic PWV was measured with the Sphigmocor® device (AtCor Medical, Sydney, Australia) by sequentially recording ECG-gated carotid and femoral artery pressure waves, using the intersecting tangent algorithm to determine the characteristic points. The path length was calculated as the 80% of the direct distance between the carotid and femoral measurement sites, as recommended by others.28 The cf-PWV was calculated as the path length divided by transit time (m/s). The cf-PWV was performed twice for each patient and the mean result was used for the analysis. The intra-observer analysis of the two measurement of pulse wave velocity was carried out with the intraclass correlation coefficient (ICC). An ICC >0.8 indicated the good liability of the test.

Statistical analysis Results are expressed by mean ± standard deviation. Comparison between groups was performed by means of χ² de Pearson

for categorical data. Fisher test was applied when number of cases was <5. The one-way analysis of variance or t-test was used for normally distributed data and the nonparametric Kruskall–Wallis or Mann–Whitney U-test for non- normally distributed variables. Univariate and multivariate cox model was used to evaluate risk factors for cf-PWV >8.1m/s. All p values were two-tailed and the statistical significance level was fixed as P <0.05. SPSS 20.0 (SPSS Inc, Chicago, IL) software was used for data management and analysis.

RESULTS Patients We identified a total of 24 patients treated with belatacept in our center.

Two of them were excluded because they were on CNI treatment before conversion to belatacept. Other two, one with atrial fibrillation one with severe obesity (BMI >35kg/m2), were excluded due to technical hurdle to measure stiffness. Thus, 20 patients on BLC group were available for the study. In the CNI group 3 patients were excluded because were shift to a combination with iMtor and CNI. Other 2 patients, one with severe obesity (BMI >35kg/m2) one with a stent graft for an endovascular aneurysm repair, were excluded due to technical hurdle to measure stiffness. 1 patient in the CNI group died due to cerebrovascular accident before to perform the PWV test. So in the CNI group 20 patients remained available for the study. Patient baseline characteristics are showed in Table 1. In the CNI group, 16 were treated with tacrolimus and 4 with cyclosporine. All

Table 1. Baseline patient’s characteristicCNI (20) BLC (20) p-Values

Age (years) 56.2±13.7 53.6±13.2 0.77Follow up from transplant (median months/range) 61 [45-113] 61 [35-118] 0.33Gender (M/F) 15/5 12/8 0.31Time on dialysis (median months/range) 17 [0-81] 22 [0-93] 0.59BMI (kg/m2) 26.8±4.48 25.3±4.33 0.80HLA mismatch 2.3±1.08 2.55±1.20 0.59Nephropathy (%)

Not Known 40 35 0.98PKD 20 25 0.98Glomerulonephritis 20 20 0.98Interstitials nephritis 20 20 0.98

Diabetes pretransplant (yes/no)

NODAT (yes/no)

0/20

0/20

2/20

1/20

0.14

Previous cardiovascular events (%) 15 20 0.90Smokers % (current/ex/never) 15/25/60 15/20/65 0.96Acute rejection (%) 15 5 0.34Delayed graft function (%) 10 15 0.64Cold ischemia time 15.3±4.6 20.5±7.6 <0.05Renal resistive index (mean) at 6 m 0.70±0.07 0.70±0.09 0.76


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not shown). Renal resistive index post transplantation (see material and methods) was similar in the two groups (Table 1).

Cardiovascular risk factors Hypertension prevalence was similar in both groups. Moreover, similar findings were observed regarding the number of antihypertensive medications, mean systolic pressure, diastolic pressure and brachial pulse pressure at the time of the test (Table 2). Also, no difference in inhibitor of renin system use (both ACE-I or ARB) was seen (p. 0.73 data not shown). CNI patients needed more commonly statins to control dyslipidemia. There were no differences in total cholesterol, LDL, HDL, triglycerides and PTH between the two groups. Also, no differences in smoking prevalence were seen (Table 1).

Pulse wave velocity The intraclass correlation coefficient for the operator (E.M.) was 0.89 (IC 0.75-0.95).

40 patients were receiving mofetil mycophenolate (MMF) and 22 of them were on prednisone (5mg/day) at the time of the study. Two patients (BLC group) were diabetic before transplantation and one (BLC group) had new onset diabetes after transplantation (NODAT). Both groups were similar regarding age, gender, time in dialysis, time from transplant, acute rejection, previous cardiovascular events, BMI and cause of nephropathy. All these factors are known for their influence on arterial stiffness. However, cold ischemia time was significantly longer in the BLC group. All acute rejection episodes were mild and responded to steroid treatment.

Renal function assessment Renal function (eGFR) at the time of the study (mean 5-yr after transplantation) was numerically higher in the BLC than in the CNI group (Table 2). Also, no statistical differences were found regarding proteinuria between the two groups (Table 2). We analyzed predictors of normal renal function defined as eGFR >60mL/min by univariate logistic regression analysis. Among variables included in Table 1 and 2, the only predictor was belatacept-based immunosuppression (OR 0.27, IC 0.71-1.04; P=0.058 data

Table 2. Clinical, vascular and laboratory variables at the time of the study

CNI (20) BLC (20) p-Values

HTA (%) 70 65 0.73

Number of antihypertensive medications

Class (%)

ACE-I or ARB

Diuretics

CCB

BB

aB

Others

Statin treatment

1.35±1.2

35

20

50

15

15

0

11/20

1.15±0.8

30

10

30

35

10

5

5/20

0.64

0.05

Systolic blood pressure (mean) 144±23 139±19 0.4

Diastolic blood pressure (mean) 83±10 80±11 0.4

Brachial pulse pressure 61±22 59±20 0.8

PWV (median/range) 7.9 [5.2-15.5] 7.4 [4.1-12] 0.4

PWV >8.1m/s (%) 50 25 0.08

Proteinuria (g/mol) 21.4±29.2 19.5±25.8 0.6

eGFR (MDRD) mL/min 55,2±20.9 69,3±17.3 0.07

iPTH (pmol/L) 13,8±6.3 11.6±6.7 0.68

Total cholesterol LDLHDLTriglycerides

4.81±0.83.06±0.81.23±0.31.52±0.5

4.89±1.143.09±1

1.34±0.51.33±0.8

0.660.430.090.57

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Because there is an important correlation between brachial pulse pressure and systolic blood pressure, only one of them must be selected for the multivariate model. We chose brachial pulse pressure since it has a higher correlation with cf-PWV than that observed with systolic blood pressure.2 Therefore, belatacept use, recipient age, renal resistive index, pulse blood pressure, proteinuria and statin use were considered in the multivariate logistic regression model (Table 4). Among these variables, recipient age and a high renal resistive index were independent predictors of a high cf-PWV. On the other hand, belatacept treatment was an independent predictor of a low cf-PWV.

DISCUSSION In this study we evaluated aortic stiffness by means of a validated reference method29 in an adult renal transplant cohort with low number of previous cardiovascular events and low diabetes prevalence. Importantly, the time after kidney transplantation in the two groups was long enough to allow the evaluation of a parameter like arterial stiffness, which needs years to be modified. The major finding in our study was that belatacept treatment was associated with a lower prevalence of high arterial stiffness than CNI (see Figure 1 and Table 2). Moreover, in the multivariate analysis, belatacept treatment was an independent predictor of displaying a PWV below 8.1m/s. Although our threshold of 8.1m/s is quite lower than the 10m/s indicated by an expert consensus statement28 concerning hypertensive population, the relationship between cardiovascular risk and pulse velocity wave is continuous. Probably, in kidney transplant recipients

There were no differences in PWV median between the two groups 7.9±3.4m/s [Range 4.1-12m/s] in CNI group and 7.4±4 m/s [Range 5.2-15.5m/s] in BLC group (p=0.4 see Figure 1).

Due to large discrepancy of age in our population study, we chose a value of 8.1m/s of cf-PWV as cut-off value for high arterial stiffness, which was correlated with an augmented risk of cardiovascular mortality in a recent retrospective study performed in transplant population.4

The prevalence of cf-PWV above 8.1m/s was lower in the BLC group (50% in the CNI group versus 25% in the BLC group) (see Table 2 and Figure 1).

As cf-PWV higher than 8.1m/s was considered a surrogate risk factor for cardiovascular events in renal transplantation, we performed a logistic regression analysis considering cf-PWV as a categorical variable (cut-off of 8.1m/s) in order to identify predictors of high PWV in this population (Table 3). By univariate analysis, some baseline variables, such as recipient age and renal resistive index, were associated with cf-PWV >8.1m/s. Also, belatacept use tended to be associated with a low cf-PWV (OR 0.33; P=0.08). Others factors like cold ischemia time, HLA mismatch, acute rejection and BMI did not show any association with cf-PWV (data not shown). Among the variables examined when PWV test was performed, systolic blood pressure, brachial pulse pressure, statin use and proteinuria were associated with a high PWV, but not eGFR (Table 3). On the other hand, diastolic pressure, dyslipidemia (LDL, HDL and triglycerides), calcemia, phosphatemia and magnesemia were not associated with PWV (data not shown).

Table 3. Univariate regression logistic analysis for risk of PWV >8.1ms

Pulse wave velocity Univariate

<8.1 >8.1 OR p

Treat group

CNI (%) 40 66.7

BLC (%) 60 33.3 0.33 0.08

Sex

Male (%) 68 66.7

Female (%) 32 33.3 1.06 0.93

Age (mean years) 49.3±12.3 65±6.7 1.16 <0.01Renal Resistive Index

Statin treatment No (%) Yes (%)

0.67±0.08

7228

0.76±0.07

4060

1.19

3.85

<0.01

0.05GFR (mean mL/min) 66.68 55.49 0.97 0.19

Proteinuria (mean ratio Cr/Pr) 16.5±18.6 35.3±35.5 1.02 0.05

Systolic blood pressure (mean mmHg) 131.2±14 158.6±20 1.11 <0.01

Pulse blood pressure (mean mmHg) 50.1±10 76.4±24 1.10 <0.01


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as well as in kidney recipients,4 the GFR was inversely related to cf-PWV. In our study we have not observed any relationship between GFR and cf-PWV, probably due to the well-preserved GFR in the patients included. This result is similar to the one reported in a study including patients with diabetes and mild CKD, where no difference in PWV was seen between patients with GFR >60mL/min versus <60mL/min.32 On the other hand, the deleterious effect of arterial stiffness on renal microcirculatory system is well documented and appearance of proteinuria (or microalbuminuria) is very common in hypertensive patients.33 We found a correlation between proteinuria and PWV. However, the cause of proteinuria in renal transplant recipients is multifactorial, not just a consequence of arterial stiffness and probably this is the reason why proteinuria was not an independent predictor of PWV in the multivariate analysis.

Another interesting point of our analysis was the demonstration of a close positive correlation between resistive renal index post transplantation with a high cf-PWV. Each 0.01 reduction in the renal resistive index was associated with a reduction of 19% in the probability of having an elevated pulse wave velocity. Other authors have also demonstrated the relationship between the renal resistive index and the pulse wave velocity in hypertensive patients.33 The increase in renal resistive index represents the physiological response to a high intra-aortic pulse pressure due to high stiffness. Interestingly, renal resistive index and recipient age were independent predictors of a high pulse wave velocity, reflecting the importance of the biological (aging) status of the patient in this parameter. Among other cardiovascular risk factors, statin use was related with a high PWV in the univariate but not in the multivariate analysis, thus suggesting that patients with more vascular lesions (older and/or with high arterial stiffness) are more likely to receive a statin.

Our study has some limitations. Firstly, its cross-sectional nature, since it is not a randomized prospective trial. Secondly, we are aware of the risk of incidence-prevalence bias due to the exclusion of some patients, anyway the number of patients excluded is similar for the two study groups and only one patient in CNI group died. Thirdly,

-a group of hypertensive patients with a high cardiovascular mortality- the threshold of 10m/s is too high to best fit the cardiovascular risk, as suggested by others.4

As showed by others,2,4 also in our patients pulse wave velocity was directly correlated to arterial blood pressure (both systolic and brachial pulse pressure) and with age. Although elevated blood pressure may cause vascular damage and accelerated conduit, artery stiffening, aortic or vascular stiffness can, per se, increase pressure pulsatility and finally increase systolic blood pressure. A recent report of a Framingham study showed for the first time that a high arterial stiffness, in the long time, is a predictor of development of blood pressure hypertension and not vice-versa.30 Unfortunately we did not have basal data on blood pressure and on cf-PWV, so we could not conclude whether high stiffness was cause or consequence of the high prevalence of arterial hypertension in ours patients. In our study, hypertension prevalence was high in both groups and was quite well controlled, moreover a small difference, although not statistical significant, was seen in blood pressure measurement between the two groups. The type of CNI treatment could influence this finding, since in our study the majority of control arm patients were on tacrolimus and this CNI is more favorable than cyclosporine for controlling blood pressure.31 Thus, the fact that blood pressure was similar between belatacept and CNI groups suggests that the beneficial effect of belatacept on PWV may be independent from blood pressure control. Recently, Vinh and colleagues reported that CTLA4-Ig treatment in mice prevents angiotensin or desoxy-corticosterone acetate (DOCA)-salt-induced hypertension, and that this effect is mimicked by genetic CD80/CD86 deficiency.29 Dendritic cell can expose damage-associated molecular patterns (DAMPS) produced by vascular stress induced by mild arterial hypertension, thus promoting T cell-activation through co-stimulation signals, that can lead to a progression of stiffness and severe arterial hypertension.29 Ideally, belatacept could disrupt this cycle, blocking the costimulation of T-cell by dendritic cells.

In our study, like in the Benefit trial,26 belatacept treated patients showed a better renal function estimated by the eGFR-MDRD. In studies performed in CKD patients,2

Table 4. Multivariate regression logistic analysis for risk of PWV >8.1ms

OR P CI

Belatacept (yes vs. no) 0.008 0.045 0.004 0.890

Agea 1.24 0.033 1.017 1.528

Renal Resistive Indexb 1.25 0.053 1.030 1.540

Statin treatment (yes vs. no) 3.35 0.07 0.005 193.3

Pulse blood pressure (mean mmHg) 1.08 0.09 0.98 1.02a OR representing change of 1 years between two individuals.b OR representing change of 0.01 of resitance index between two individuals.

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due the exclusion process, there is a little difference of prevalence (although no statistically significant) of male patients in the CNI group, possibly caused by an imbalance in favor of less stiffness in BLC group, however this difference is very small (5 vs. 8 female in CNI and BLC respectively) and probably become blurred when matching the group for other variables.

Finally, blood pressure was measured in office, and neither ambulatory blood pressure monitoring nor self-home blood pressure monitoring was performed. The fact that the difference in blood pressure was slightly inferior in the BLC group, although no significant, is another possible limitation of our study.

In conclusion, recipient age and renal resistive index were independent predictors of high arterial stiffness in kidney allograft recipients. Moreover, our study showed, for the first time, that belatacept treatment, as maintenance immunosuppression, is independently associated with low arterial stiffness long-term after transplantation. Therefore, beyond its beneficial effect on renal function, belatacept could improve kidney transplant recipient’s survival by reducing cardiovascular events related to stiffness. These results should be confirmed in a well-powered prospective trial.

Acknowledgments

This study was performed without any funding from pharmaceutical companies. This study was partly supported by the RETICS program REDinREN 12/021/0003 from the ISCIII, Spanish Government.

We thank Dr. Nuria Porta for her assistance in statistical data analysis.

Conflicts of interest The authors declare that they have no conflicts of interest related to the contents of this article.

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30. Kaess BM, Rong J, Larson MG, Hamburg NM, Vita JA, Levy D, et al. Aortic stiffness, blood pressure progression, and incident hypertension. JAMA 2012;308(9):875-81.

31. Claes K, Meyer-Kriesche HU, Schold JD, Vanrenterghem Y, Halloran PF, Ekberg H. Effect of different immunosuppressive regimens on the evolution of distinct metabolic parameters: evidence from the Simphony study. Nephrol Dial Transplant 2012;27:850-7.

32. Sjöblom P, Nystrom FH, Länne T, Engvall J, Östgren CJ. Microalbuminuria, but not reduced eGFR, is associated with cardiovascular subclinical organ damage in type 2 diabetes. Diabetes Metab 2014;40(1):49-55.

33. Hashimoto J, Ito S. Central pulse pressure and aortic stiffness determine renal hemodynamics: pathophysiological implication for microalbuminuria in hypertension. Hypertension 2011;58(5):839-46.

Devuyst O, et al. The relation between hypomagnesaemia and vascular stiffness in renal transplant recipients. Nephrol Dial Transplant 2011;26:2362-9.

22. Gungor O, Kircelli F, Carrero JJ, Hur E, Demirci MS, Asci G, et al. The effect of immunosuppressive treatment on arterial stiffness and matrix Gla protein levels in renal transplant recipients. Clin Nephrol 2011;75:491-6.

23. Williams B, Lacy PS, Thom SM, Cruickshank K, Stanton A, Collier D, et al. Differential impact of blood pressure-lowering drugs on central aortic pressure and clinical outcomes: principal results of the Conduit Artery Function Evaluation (CAFE) study. Circulation 2006;113(9):1213-25.

24. Agarwal R. Antihypertensive agents and arterial stiffness: relevance to reducing cardiovascular risk in the chronic kidney disease patient. Curr Opin Nephrol Hypertens 2007;16:409-15.

25. Vincenti F, Larsen CP, Alberu J, Bresnahan B, Garcia VD, Kothari J, et al. Three-year outcomes from BENEFIT, a randomized, active-controlled, parallel-group study in adult kidney transplant recipients. Am J Transplant 2012;12:210-21.

26. Durrbach A, Pestana JM, Pearson T, Vincenti F, Garcia VD, Campistol J, et al. A phase III study of belatacept versus cyclosporine in kidney transplants from extended criteria donors (BENEFIT-EXT study). Am J Transplant 2010;10:547-57.

27. Larsen C, Grinyó J, Medina-Pestana J, Vanrenterghem Y, Vincenti F, Breshahan B, et al. Belatacept-based regimens versus a cyclosporine

Sent to review: 3 Jun. 2014 | Accepted: 23 Sep. 2014


57

7.3. Impact of immunosuppressive therapy on arterial stiffness in kidney transplantation: Are all treatments the same? In press Clinical Kidney Journal

Revisión: La rigidez arterial en el trasplante renal: no todos los

inmunosupresores son iguales.8

J_ID: NDTPLUS Customer A_ID: SFX120 Copyedited by: PR Manuscript Category: CKJ Review Cadmus Art: OP-NDTP

C K J R E V I E W

Impact of immunosuppressive therapy on arterialstiffness in kidney transplantation: are all treatmentsthe same?

5 Edoardo Melilli, Anna Manonelles, Nuria Montero, Josep Grinyo,Alberto Martinez-Castelao, Oriol Bestard and Josep CruzadoAQ1

Department of Nephrology, Bellvitge University Hospital, L’Hospitalet de Llobregat, Cataluny, Spain

Correspondence and offprint requests to: Edoardo Melilli; E-mail: [email protected]

Abstract10 Arterial stiffness is a biologic process related to ageing, and its relationship with cardiovascular risk is well established.

Several methods are currently available for non-invasive measurement of arterial stiffness that provide valuableinformation to further assess patients’ vascular status in real time. In kidney transplantation recipients, several factorscould accelerate the stiffness process, such as use of calcineurin inhibitors (CNIs), presence of chronic kidney disease andother classical cardiovascular factors, which would explain, at least in part, the high cardiovascular mortality and

15 morbidity. Despite the importance of arterial stiffness as a biomarker of cardiovascular risk, and unlike other cardiovascularrisk factors (e.g. left ventricular hypertrophy), only few clinical trials or retrospective studies of kidney recipients so far haveevaluated its impact. In this review, we describe the clinical impact of arterial stiffness as a prognostic marker ofcardiovascular disease and the effects of different immunosuppressive regimens on its progression, focusing on thepotential benefits of CNI-sparing protocols and supporting the rationale for individualization of immunosuppression in

20 patients with lower arterial elasticity. Among the immunosuppressive drugs, a belatacept-based regimen seems to offerbetter vascular protection, compared to CNIs, although further studies are needed to confirm the preliminary positiveresults.

Key words: arterial stiffness, augmentation index, immunosuppression, kidney transplantation, pulse wave velocity

25 IntroductionHigh cardiovascular mortality and morbidity in kidney trans-plant patients still remains a great concern. Although the 1-yearsurvival rates post-transplantation are high, cardiovascular riskin these patients is higher than in healthy subjects [1, 2].

30 Cardiovascular disease is the leading cause of death andthe second cause of graft loss in kidney recipients [3].However, classical cardiovascular risk factors are not reliable

predictors of cardiovascular events in this population; in fact,the risk score calculators used for the general population usu-

35ally underestimate the cardiovascular risk in kidney recipients[4]. Immunosuppressive therapy and other unconventionalrisk factors (such as arterial stiffness) could explain the failurein predicting cardiovascular events in this population. Amongimmunosuppressive drugs, steroids and calcineurin inhibitors

40(CNIs) have a negative impact on the cardiovascular system

Received: June 6, 2017. Editorial decision: September 6, 2017

VC The Author 2017. Published by Oxford University Press on behalf of ERA-EDTA.This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited.For commercial re-use, please contact [email protected]

1

Clinical Kidney Journal, 2017, 1–9

doi: 10.1093/ckj/sfx120CKJ Review


[5, 6], as they are potent vasoconstrictors which directly leadto vascular fibrosis [7]. Moreover, treatment regimens basedon use of CNIs and corticoidAQ11 increase blood pressure (throughsalt retention and/or hyperactivationAQ3 of the renin–angiotensin

45 system) and low-density lipoprotein cholesterol levels, thusindirectly affecting the vasculature [8, 9].AQ4

Prednisone withdrawal and CNI-sparing therapy protocolsare tempting strategies to reduce the cardiovascular burden inkidney transplant recipients, but these immunosuppressive

50 regimens might increase the risk of rejection, thereby limitingtheir potential clinical benefit [10]. Instead, an individualizedimmunosuppressive protocol could improve outcomes inselected patients with high cardiovascular and low immuno-logical risk. Biomarkers would be useful towards such per-

55 sonalized medicine, but they are unfortunately still lacking.Consequently, transplant clinicians are looking for tools topredict and prevent cardiovascular events.

In contrast to this discouraging scenario, some recent stud-ies have addressed the importance of arterial stiffness parame-

60 ters as powerful predictive variables of cardiovascular events inkidney transplant recipients [11, 12].

Arterial stiffness is a biologic process related to ageing [13,14] and blood pressure [15], but also with inflammation [16, 17],arterial calcification [18] and chronic kidney disease (CKD) stage

65 [19]. In kidney transplant recipients, several studies have alsoassociated arterial elasticity with donor age [20], donor vascularstiffness (in the case of living donors) [21], new-onset diabetespost-transplantation [22], cold ischaemia time [23], renal graftfunction (Gfr) [24], hypomagnesaemia [25] and resistance train-

70 ing [26]. In addition, CNI therapy is known to contribute to vas-cular stiffness acceleration [27].

Arterial stiffness in hypertensive patients has been studiedin previous clinical trials [28, 29], which showed that certainclasses of blood pressure-lowering drugs appear to decrease

75 stiffness more effectively than others, although this might berelated to their better control of blood pressure [30].AQ12 In kidneytransplant studies, except for a few minor studies that analysedthe effect of several immunosuppressive protocols on arterialstiffness, only two recent randomized clinical trials have intro-

80 duced arterial stiffness as a secondary end point [31, 32].Here, we provide a descriptive review of the literature focus-

ing on the usefulness of pulse wave velocity (PWV) as a predic-tor of cardiovascular events and on how immunosuppressivetherapy could modify arterial stiffness in kidney transplant

85 recipients.

Arterial stiffness evaluation in kidneytransplantationThe three layers of the arterial wall contribute, each to a differ-ent extent, to its elastic property which can be measured at

90 both macro- and micro-scale levels [33]. With ageing and/or dueto concurrent diseases (e.g. arteriosclerosis), the balancebetween elastin fibres and collagens tends to be disrupted infavour of the latter. This process involves several players,including: matrix metalloproteinases [34, 35, 36] which degrade

95 elastin fibres and the connections between them; calcium depo-sition in the tunica media; and collagen glycosylation byadvanced glycation end-products (AGEs) [37]. Also endothelialand vascular smooth muscle cells can affect the elastic propertyof the arterial wall, although the mechanisms are not well

100 understood [33]. All the aforementioned factors cause an accel-eration of the arterial stiffnessAQ13 .

The gold standard for measuring arterial stiffness is intra-aortic arterial pressure measurement, an invasive methodrequiring arterial catheterization [38]. Nowadays, there also

105exist several non-invasive methods for arterial stiffnessassessment [39, 40], with PWV calculation being the mostwidely used. Since the aorta has elastic properties, after eachsystole, pressure is transmitted through the aortic wall andbranches, generating a forward wave with propagation speed

110(PWV) depending on the wall elasticity, being faster in patientswith greater stiffness [41]. When the wave reaches the impe-dance points on the arterial tree, it generates a reflected, back-ward wave which, in presence of increased stiffness, reachesthe aorta during the systole of the same cardiac cycle, thus

115causing an augmentation of the central blood pressure (AP)which can be quantified as the augmentation index (Aix),defined as the percentage of the central pulse pressure attrib-uted to the reflected pulse wave [42].

Figure 1 shows how structural changes in the aorta, small120arteries and arterioles modify the PWV, Aix and pulse pressure,

the three parameters commonly evaluated in studies of arterialstiffness AQ6.

A detailed description of the definition of arterial stiffnessand of the validity of all methods currently available for the

125evaluation and measurement of aortic stiffness has beenrecently and exhaustively reviewed by Adenwalla et al., towhich we refer the readers [43].

Increased arterial stiffness in kidneytransplant recipients is a powerful predictor of

130cardiovascular eventsResults from PWV measurements should be evaluated based onthe patient’s age. Although the 2007 ESH/ESC AQ8hypertensionguidelines recommend a fixed threshold value of 12 m/s todetect patients with high cardiovascular risk [44], more recently,

135a consensus document has set this value at 10 m/s [45].However, irrespective of the cut-off value, cardiovascular risk isincreased even at a lower threshold [44].

In a Dutch study including a kidney transplant cohort of 330patients, the PWV was found to be predictive of cardiovascular

140events and survival, irrespective of patients’ age. Interestingly,patients with a PWV of 7.5 m/s or greater showed worse survivalrates than those with a PWV of <7.5 m/s [46].

In 2011, in a prospective study of a cohort of 512 kidneytransplant recipients, PWV, together with central aortic pres-

145sure (AP) and Aix, were measured at the time of kidney trans-plantation. After a mean follow-up of 5 years, PWV and AP wereincluded in a model based on clinical variables and laboratorydata to predict cardiovascular events. Adding PWV and AP dataled to a net reclassification improvement for cardiovascular

150events of 15.9%. Moreover, patients with a PWV of 8.1 m/s orgreater had worse cardiovascular survival rates AQ14, compared withpatients with a PWV of <8.1 m/s [11].

Lastly, a recent study from a Norwegian group including1022 kidney transplant recipients showed that below a cut-off

155value of 12 m/s, each increment in PWV of 1 m/s starting from8 m/s was associated with a 36% increase in mortality risk [12].

The aforementioned studies demonstrate the powerful pre-dictive value of PWV for cardiovascular events and mortality(see Table 1), irrespective of age and other clinical or laboratory

160variables, thus confirming data obtained from other studiesinvolving different patient populations [47].

2 | E. Melilli et al.


Arterial stiffness and immunosuppressionAs previously described, CNI toxicity on arteries is well known,at least at the microcirculatory level. Two types of toxicity for

165 cyclosporine have been described: acute and chronic toxicity[48]. Acute toxicity is a functional alteration due to an imbal-ance between vasoconstrictors and vasodilators, leading to adecrease in renal blood flow and to an increase in vascularresistance, particularly at the arteriolar level. Since arteriolar

170 network resistance is the ‘last barrier’ against pulsatileAQ15 pres-sure and represents the gate of the backward wave [49], this

vasoconstriction at arteriolar level is probably the cause ofaugmentation of certain stiffness parameters (Aix and AP) inpatients treated with cyclosporine. Several factors seem to

175play a role in this acute toxicity: hyperactivation of the renin–angiotensin system [50], upregulation of endothelin receptors[51], endothelial cell injury [52], alteration in L-arginine nitricoxide production and hyperactivation of the sympatheticsystem [53]. Calcium antagonists and angiotensin receptor

180blockers (ARBs) or angiotensin-converting enzyme inhibitors(ACEis) are known to mitigate the acute toxicity, which makes

Fig. 1. Scheme of wave propagation according the PWV model. (A) Healthy subject/healthy artery: PWV is slow at the aortic level and fast at small (muscular) arteries.Each wave represents the sum of a unique forward wave (blue arrow) and multiple backward waves (black arrows). Backward waves are generated from reflectionpoints located in the circulatory system: bifurcations (green dashes), and small arteries and arterioles (not shown in the figure). Due to the PWV gradient, the lengthand resistance at reflection points, backward waves reach, with a delay, the systolic peak of the forward wave, so there is no significant augmentation pressure (orAix). (B) Patients with arterial stiffness: aortic media calcification and atherosclerotic plaque (red arrows in upper boxAQ26 ) tend to increase the PWV at the aortic level.Moreover, changes in muscular tone and structure in small arteries (blue arrow) and/or arteriolar hyalinosis (black arrows) increase resistance, amplifying the magni-tude of reflected waves. As a consequence, more prominent backward waves reach the forward wave near to systolic peak, thus generating a notable increase in cen-tral AP, expressed as augmentation pressure.

Table 1. Main studies on the predictive power of arterial stiffness for cardiovascular end point (mortality and event)

SourceNumber

of patientsFollow-up

(mean years)Independent predictivepower for CV death: PWV

Independent predictivepower for CV death: Aix or AP

Mitchel et al. 2010 [46] 330 3.8 YES NAVerbeke et al. 2011 [11] 512 5 YES YESDahle et al. 2015 [12] 1040 4.2 YES NA

Aix, augmentation index; Ap, aortic pressure; CV, cardiovascular; PWV, pulse wave velocity. All studies used SphigmocorVR device for calculation of PWV and Aix or AP.

Are all treatments the same?AQ2

| 3


it difficult to understand how all these factors contribute toacute vascular toxicity [54, 55].

Chronic toxicity is characterized by a structural change in185 vessels, particularly small arteries and arterioles [56]. Hyalinosis

lesions on the arteriolar wall, a hallmark of CNI toxicity, arepresent in protocol biopsy at 10 years in the majority of patientsreceiving tacrolimus or cyclosporine [57]. Treatment using themTOR inhibitors (imTORs) sirolimus and everolimus has been

190 shown to attenuate allograft vasculopathy in heart transplantrecipients [58–60].

Whether immunosuppressive drugs could modify PWV,directly or indirectly influencing vasculature, remains largelyspeculative and difficult to demonstrate for the following reasonsAQ16

195 [61]. First of all, transplantation per se ameliorates arterial stiff-ness [62, 22, 63], probably as a result of recovery in renal function.Renal function is, in fact, closely related to PWV, as shown byFord et al. [19]. Moreover, transplantation allows better control ofblood pressure, thus decreasing PWV, although Seibert et al.

200 showed that high PWV was related to cardiovascular events afterkidney transplantation, regardless of peripheral blood pressure[64]. Finally, the majority of studies published so far are small-scale, retrospective and case-controls (see Table 2).

Despite these limitations, there is some evidence of a protec-205 tive effect of CNI-sparing protocols on the progression of arterial

stiffness in kidney transplant recipients. Table 3 summarizesthe impact of different immunosuppressive drugs on PWV, Aixand blood pressure.

CNIs and stiffness210 Initial data on CNI effects on large arterial functions have been

conflicting. In a prospective study, Zoungas et al. comparedPWV before and after kidney transplantation in 36 patients. At12 months post-transplantation, PWV improved in all patients,irrespective of cyclosporine or tacrolimus use, although Aix

215 reduction was greater in patients treated with tacrolimus(!8.0 6 16.5% versus !27.4 6 18.2%; P ¼ 0.01) [63].

In a small study, Covic et al. showed that cyclosporineacutely decreased the Aix [73]. However, the study lacked a con-trol group and the decrease in Aix after cyclosporine uptake was

220related to a decrease in the timing of the reflected wave, whichcould lead to an increased PWV in the long term.

Interestingly, in the same period, a cross-sectional study(including 250 stable kidney transplant recipients) showedthat cyclosporine increased Aix and blood pressure

225considerably more than tacrolimus [65]. In 2007, Strozecki et al.compared PWV in 76 patients taking cyclosporine with 76patients taking tacrolimus. The two study groups werematched for main clinical characteristics (age, blood pressure,time on haemodialysis, diabetes). The cyclosporine group had

230higher PWV values, compared with the tacrolimus group(9.33 6 2.10 versus 8.54 6 1.35, respectively; P < 0.01) [66]. Inanother study by the same group, stepwise multiple regressionanalysis showed that age, male sex, mean arterial pressure(MAP), cyclosporine (versus tacrolimus) and fasting glucose

235concentration were independently associated with increasedPWV [74]. Cyclosporine effect on stiffness is probably due to anincrease in vascular tone or to impaired nitric oxide vasodila-tation AQ17, although a study from Silverborn et al. did not confirmthis hypothesis [75]. In their proof of concept study, 18 lung

240transplant recipients (all treated with cyclosporine) were

Table 2. Main studies on effect of IMS on arterial stiffness in kidney transplant recipients

Source Design N IMS Results Limitation

Zoungas et al. 2004 [63] Longitudinal 36 24 CYC PWV: no difference Small12 TAC Aix: TAC ###/CYC #

Ferro et al. 2002 [65] Transversal 250 146 CYC PWV: NA Design62 TAC Aix: TAC # versus CYC

Strzoecki et al. 2007 [66] Transversal 152 76 CYC PWV: TAC # versus CYC Design76 TAC Aix: NA

Seckinger et al. 2008 [67] Conversion CYC to EVR 27 10 CYC PWV: CYC "; EVR # Small17 EVR Aix: NA Short follow-up

Joannides et al. 2011 [68] Conversion CYC to SRL 44 21 CYC PWV: CYC "; SRL # Small23 SRL Aix: CYC "; SRL # Sselection criteria

Gungor et al. 2011 [69] Transversal 81 47 CNI PWV: no difference Small34 imTOR Aix: no difference Mixed CNI/imTOR

Seibert et al. 2014 [70] Transversal 46 23 BLC PWV: no difference Small23 CYC Aix: BLC # versus CYC Selection

Melilli et al. 2015 [71] Transversal 40 20 BLC PWV <8.1: BLC 60%, CNI 40% Small20 CNI Aix: NA CNI mixed

Cruzado et al. 2016 [72] Conversion TAC to EVR 60 32 TAC PWV: no difference Normal PWV28 EVR Small

Holdaas et al. 2017 [31] Conversion CNI to EVR 164 95 CNI PWV: no difference Normal PWV69 EVR Aix: NA CNI mixed

Aix, augmentation index; BLC, belatacept; CYC, cyclosporine; EVR, everolimus; IMS, xxxAQ25 ; PWV, pulse wave velocity; SRL, sirolimus; TAC, tacrolimus.

Table 3. Main effects of different immunosuppressive drugs onPWV, Aix and blood pressure

DrugsSystemic bloodpressure PWV Aix or AP

Cyclosporine þþþ þþ þþ/þTacrolimus þ/þþ !/þ þimTOR (everolimus

or sirolimus)! ! !/þ

BLC ! ! !Mycophenolate mofetil ! ? AQ9?Steroid þ ? ?



compared with patients waiting for lung transplantation andhealthy controls. Arterial resistance, non-endothelial-dependent relaxation and arterial stiffness (by echo-tracking)were analysed. Lung recipients had significantly less elastic

245 arteries than healthy controls or patients on the transplantwaiting list, even though no difference in blood pressure orendothelial response to nitric oxide was obtained.

Since cyclosporine was found to be related to higher PWV,conversion to tacrolimus could be an option to improve arterial

250 stiffness. This hypothesis was tested in a small study wherebystable kidney recipients taking cyclosporine (>10 years) wereconverted to tacrolimus. PWV (by echo-tracking) and ambula-tory blood pressure monitoring (ABPM) were performed at base-line and repeated at 3 months post-conversion. No difference

255 was observed in blood pressure or PWV, probably due to theshort time span from conversion [76].

Despite the limitations in their study design, all the afore-mentioned studies suggest a possible negative impact of CNIs,and especially cyclosporine, on PWV.

260 imTORs and arterial stiffness

The imTORs everolimus and sirolimus have been indevelopmentAQ18 in immunosuppressive regimens for use in kidneytransplantation. Yet since they were first used, they have notshown superior efficacy in terms of renal survival or prevention

265 of rejection, compared to tacrolimus [77, 78]. Beyond theirimmunosuppressive property, imTORs exert certain pleiotropiceffect on atherogenesis [79, 80] and fibrosis [81], so at least intheory, kidney transplant recipients may benefit from the use ofimTORs in terms of arterial elasticity.

270 In a randomized clinical trial, 17 of 27 patients wereswitched from cyclosporine to everolimus 6 months after kid-ney transplantation. PWV remained stable in the everolimusgroup (9.50 6 1.92 versus 9.13 6 1.62 m/s, DPWV !0.37 6 1.14 m/s), whereas it was increased in the cyclosporine group

275 (9.93 6 1.94 versus 10.8 6 2.24 m/s, DPWV þ 0.89 6 1.47 m/s) [67].In a sub-study of the CONCEPT trial [68], 23 of 44 patients

were converted from cyclosporine to sirolimus 12 weeks afterkidney transplantation. PWV and Aix were evaluated at weeks12, 26 and 52. Patients in the sirolimus group experienced a

280 decrease in PWV, whereas those in the cyclosporine group hadan increase in PWV, with a significant difference at week 52.Both groups experienced an increase in Aix, which was moremarked in the cyclosporine group. According to the authors, theprogressive decrease in PWV in the sirolimus group was a

285 cause, rather than a consequence, of the better blood pressurecontrol.

Despite these encouraging results, a cross-sectional study byGungor et al. [69] showed no benefit in terms of PWV or Aix in agroup of patients treated with an imTOR (for at least 6 months,

290 with either sirolimus or everolimus), compared to treatmentwith CNIs (cyclosporine or tacrolimus). In a linear regressionanalysis, only conventional risk factors (age, blood pressure,cholesterol level and proteinuria) were predictive of arterialstiffness.

295 More recently, a randomized clinical trial on the effect of lateconversion from CNIs (tacrolimus) to an imTOR (everolimus)showed a small benefit related to regression of left ventricularhypertrophy in both groups. As secondary outcomes, changesin blood pressure (measured by ABPM) and PWV were evaluated

300 before and after conversion. The median time from transplanta-tion was 1.7 years for the tacrolimus group (25 patients) and1.3 years for the everolimus group (31 patients). At 24 months

from randomization, both groups had very well-controlledblood pressure, although the dipper status was preserved in

305more patients on everolimus (30% of tacrolimus-treatedpatients were non-dippers versus 22% of patients on everoli-mus). PWV values at baseline and 12 and 24 months were in thenormal range, with no significant differences between the twostudy groups [72].

310Another ancillary study from a recent trial [31] evaluatedPWV and blood pressure by ABPM. PWV data were obtained for277, 223 and 184 patients at randomization and months 12 and24, respectively. Patients converted to everolimus had a slightdecrease in PWV (month 12: !0.24 m/s; month 24: !0.03 m/s),

315whereas patients on cyclosporine experienced a progressiveincrease in PWV (month 12: 0.11 m/s; month 24: 0.16 m/s).Although the difference was not significant, one can argue thatbasal AQ21values were in the normal range (mean 7.8 m/s for theeverolimus group and 7.6 m/s for the cyclosporine group).

320Follow-up at 24 months confirmed the predictive value of PWV,since the incidence of cardiovascular events in the entire cohortwas low (2.8% in the everolimus group and 4.8% in the cyclo-sporine group). In such low-risk populations, a greater numberof patients is necessary in order to show any benefit in a cardio-

325vascular end point (or PWV) from any therapeutic intervention(such as conversion to an imTOR). Moreover, since such smallvariations (0.4–0.5 m/s) usually occur over a long time span,follow-up at 24 months was probably too early a time point todetect any significant change in PWV [82, 83].

330Since patients with high PWV at baseline are susceptible to asteeper increase in PWV [13], we cannot exclude the possibilitythat conversion to imTORs is beneficial for these patients.

Co-stimulatory blockade and arterial stiffnessThe biologic immunosuppressant belatacept (BLC) is a fusion

335protein comprising the common fragment Fc of human immu-noglobulin G (IgG) and CTL4, which, upon binding to CD80 andCD86 receptors on antigen-presenting cells (APCs), inhibits co-stimulatory signals essential for T-lymphocyte activation. Inthe two non-inferiority clinical trials BENEFIT AND BENEFIT-

340EXT [84, 85], BLC was demonstrated to have an anti-rejectionefficacy similar to cyclosporine. At 3-year follow-up, patientstreated with BLC showed better renal function, less renal fibro-sis in protocol biopsy and a better cardiovascular profile AQ19[86]. Inparticular, at 12 months, systolic and diastolic blood pressures

345were lower in patients treated with BLC than in those treatedwith cyclosporine, as shown in the BENEFIT and BENEFIT-EXTtrials, even though both treatment groups had the same base-line level of blood pressure. Moreover, in the BENEFIT trial, bothBLC regimens AQ20were associated with a 30% reduction in the odds

350of requiring a higher number of antihypertensive medicationsat month 12 (P¼ 0.02, BLC-LI versus cyclosporine A) [87].

Data analysis from these trials at different time points (12,36 and 84 months) also showed that patients treated with BLChad a better Gfr, compared with patients treated with cyclo-

355sporine [87]. A long-term analysis from the BENEFIT trial at7 years showed a 43% reduction in mortality risk or risk of graftloss with both the more intensive and the less intensive BLCregimens, compared with the cyclosporine regimen [88]. SinceGfr is a powerful predictor of cardiovascular events and mortal-

360ity in kidney transplant recipients [89, 90], these results werenot unexpected.

In addition to better survival rates related to Gfr, data fromother studies suggest improved control of arterial stiffness in BLC-based regimens. In an experimental model of angiotensin- or

Are all treatments the same? | 5


365 deoxycorticosterone acetate (DOCA)-salt-induced hypertension,Vihn et al. administered treatment infusion based on CTLA4-Ig (adrug with effects mimicking genetic CD80/CD86 deficiency) inmice, thus preventing hypertension acceleration [91]. A possibleinfluence of the immune system on hypertension is not new, since

370 T-cell contribution in DOCA-salt-induced hypertension in thymec-tomized mice had been shown over 25 years ago [92]. In mildhypertension, endothelial vessel damage causes release of DAMPs(damage-associated molecular patterns) and altered self-proteins.Hypothetically, these molecules could be recognized as antigens

375 presented by dendritic cells and thus trigger the immune system,activating T-cells and stimulating cytokine production and inflam-mation [93], the latter being closely associated with increased vas-cular stiffness [16].

From a clinical perspective, only two studies have analysed380 the impact of BLC on arterial stiffness in kidney transplant recipi-

ents. In the first study [70], Seibert et al., in a case-control retro-spective study, compared 23 patients treated with BLC with 23patients treated with cyclosporine. The two groups showed nosignificant differences with regard to gender distribution, age,

385 body mass index, time on dialysis prior to transplantationand time since transplantation. After a mean follow-up of88 months (all patients included had a minimum time fromtransplantation of 20 months and were first-kidney recipients),augmentation pressure was significantly better in the BLC group

390 (augmentation pressure 12.7 mmHg [8.3–16] versus 7.3 mmHg[2.3–11.7]; P¼ 0.048), despite no differences in systolic and dia-stolic blood pressures (both peripheral and central). PWV meanvalues were identical in both groups (8.8 m/s).

In the second study [71], our group compared 20 patients395 treated with BLC with 20 patients on CNIs (16 on tacrolimus and

four on cyclosporine). The control CNI group was matched forall the main variables affecting PWV. There were no differencesin median PWV between the two groups: 7.9 6 3.4 m/s (range4.1–12 m/s) in the CNI group and 7.4 6 4 m/s (range 5.2–15.5 m/s)

400 in the BLC group (P¼ 0.4). Due to the large discrepancy in age inour population study, we chose a value of 8.1 m/s of femoral-carotid PWV (cf-PWV) as the cut-off value for high arterial stiff-ness, which was shown to correlate with an increasedcardiovascular mortality risk in a recent retrospective study per-

405 formed in a transplant population [11]. In the study, 50% ofpatients in the CNI group had a PWV >8.1 m/s versus 25% ofpatients in the BLC group (P¼ 0.08). Regression logistical analy-sis showed that age, renal resistive index at 3–6 months aftertransplantation and BLC [odds ratio 0.008 (95% confidence inter-

410 val 0.004–0.890); P ¼ 0.045] were predictive variable of PWV.Although these two studies have some limitations (transver-

sal, lack of basalAQ21 record of arterial stiffness measurements),data on PWV and augmentation pressure suggest thatimprovement in arterial stiffness could be obtained using BLC

415 as the main immunosuppressant.

LimitationsAlthough the number of publications on arterial stiffness in kid-ney transplantation is increasing, most studies present limita-tions that warrant caution in interpreting the results.

420 As with any method of measurement performed by an oper-ator, there is a risk of high inter-observer variation. Althoughthe techniques used to measure arterial stiffness have beenalready validated in terms of reproducibility in healthy and CKDpatients [29, 94, 95], most published studies on kidney trans-

425 plantation do not report data on intra- or inter-observer varia-bility, making it difficult to assess and compare the data quality

of each study. In fact, only a few studies on kidney transplanta-tion have reported an acceptable variation coefficient index(ICC) for operator variability [21, 76, 93]. There is also an extreme

430paucity of data on intra-patient variations in stiffnessparameters.

Confounding factors represent another limitation relevantto arterial stiffness studies, including blood pressure andduration of kidney disease, both closely related to arterial stiff-

435ness. In kidney transplantation, studies published so far haveonly reported the impact of time on dialysis [22, 25, 66], whereasdata on duration of disease and/or blood pressure are scarce.Moreover, most of these studies analysed only the relationshipbetween a unique determination of blood pressure AQ22and stiffness

440parameters. More rigorous blood pressure determinations usingABPM and repeated arterial stiffness measurements are neededin order to confirm a possible independent effect of immuno-suppression on arterial stiffness. Other confounding factorssuch as diabetes and disorders of mineral and bone metabolism

445are also related to arterial stiffness in kidney transplantation[25, 68, 96]. Use of vitamin D supplementation may achieve adecrease in PWV in CKD patients [97], although no data on vita-min D repletion in recipients are available. Nonetheless, parical-citol did not seem to exert a reducing effect on PWV after 1-year

450treatment, as shown by Pihlstrøm et al. in a randomized trial onthe effect of paricalcitol on parathyroid hormone (PTH) levels inkidney transplant recipients [32].

In conclusion, all these confounders mask the true magni-tude of the impact of immunosuppressive regimens on arterial

455stiffness.

Open questions and ideas for future clinicalstudiesMeasurements of PWV, Aix and AP usually take between 20 and30 minutes when performed by an experienced operator, which

460stands as one of the obstacles impeding the widespread use ofarterial stiffness evaluation in patients on transplant waitinglists or post-transplantation. Although magnetic resonanceand/or certain blood pressure devices can assess stiffnessparameters, thus rendering these tests less cumbersome, these

465parameters have not yet been proven to be predictive of cardio-vascular events AQ23[43, 98, 99]. Moreover, the costs of measurementdevices approved by regulatory agencies often mean they areunaffordable to healthcare systems, thus restricting their use toresearch purposes only.

470Since baseline high PWV values predict a higher cardiovas-cular risk, future trials in transplantation could include basal AQ21PWV as a biomarker to discriminate those patients at veryhigh cardiovascular risk who could benefit from a CNI-free immunosuppressive regimen (BLC-based, for example).

475Moreover, monitoring of PWV after transplantation at differenttime points could identify those patients with rapid progres-sion of arterial stiffness who could benefit from conversion ofCNIs to imTORs or who need tighter control of mineral andbone metabolism or blood pressure.

480ConclusionKidney transplant recipients with higher values of PWV are atincreased cardiovascular and mortality risk. Preliminary datafrom small studies indicate that CNIs, and especially cyclospor-ine, could increase PWV in renal transplant recipients.

485Although some studies suggest a possible protective effect of



imTORs on arterial stiffness, data from two randomized trialshave not shown significant differences after either early or lateconversion of CNIs to imTORs. The reduction in cardiovascularmortalityAQ24 shown by long-term results from BLC trials could be

490 due to a decrease in arterial stiffness, which warrants furtherinvestigation.

AcknowledgementsAQ7

We thank Dr M. Goma and Dr A. Vidal from the PathologyUnit of Bellvitge Hospital for their help with the vascular

495 image in Figure 1.

Conflict of interest statement

None declared.

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67

8. Resultados

8.1 Estudio 1: Differential impact of belatacept and cyclosporine A on central aortic blood pressure and arterial stiffness after renal transplantation

Los pacientes fueron reclutados desde 3 centros (Berlín, Hannover y

Barcelona), solo se incluyeron pacientes portadores de 1er trasplante renal cuya

inmunosupresión se basaba en belatacept más micofenolato mofetilo +/-

esteroides (grupo de estudio - casos). Se realizó una comparación transversal

con el mismo número de pacientes tratados desde el trasplante con

ciclosporina más micofenolato mofetilo +/- esteroides (grupo control –

controles).

46 pacientes (23 por grupo) fueron sometidos a la realización de las siguientes

pruebas: PWV, AP a través del Sphigmocor.

Las características basales de los dos grupos de estudio se muestran a

continuación en la Tabla 4.

Tabla 4. Características basales de los dos grupos de estudio

Ciclosporina (N. 23) Belatacept (N. 23) p.

Hombre (%) 16 (69.6) 18 (78.3) 0.74

Mujer (%) 7 (30.4) 5 (21.7)

Edad (y) 55 (49-64) 54 (49-62) 0.72

BMI (Kg/m2) 25.9 (23.4-27.9) 24.5 (21.8-27) 0.22

Trasplante Donante Vivo 4 1 0.35

Tiempo en diálisis (meses) 51 (15-85) 43 (7-84) 0.5

Tiempo desde el trasplante (meses) 92 (43-120) 77 (70-125) 0.77

eGFR (ml/min/1.73m2) 54 (42-60) 59 (50.4-85.4) 0.057

Causa de IRC (%) - Glomeruloneph

4 (17.4)

7 (30.4)


68


- PKD - Nefroangioscl. - Nefr diab. (4.4) - Nefritis inters. - No filiadas - Otras

4 (17.4) 3 (13) 1 (4.4) 2 (8.7) 3 (13) 6 (26.4)

5 (21.7) 2 (8.7) 1 (4.4) 2 (8.7) 2 (8.7) 4 (17.6)

Patologías concomitantes (%) Hipertensión Arterial Diabetes Cardiovascular

23 (100) 4 (17.4) 5 (21.7)

20 (87) 2 (8.7) 5 (21.7)

0.23 0.67 1

Dislipidemia 19 (82.6) 11 (47.8) 0.029

Uso de Tabaco 8 (34.8) 15 (65.2) 0.08

Anti-hta y estatinas (%) - Calcio antagonistas - IECA/ARAII - Beta Bloqueantes - Estatinas

17 (73.9) 9 (39.1) 17 (73.9) 9 (39.1)

10 (43.5) 14 (60.9) 10 (43.5) 10 (43.5)

0.07 0.24 0.07 1

Los dos grupos no presentaron diferencias significativas excepto en el valor de

colesterol total (mayor en el grupo ciclosporina). La función renal fue mejor en

el grupo belatacept, aunque no estadísticamente significativa (P= 0.057). No se

evidenció ninguna diferencia estadísticamente significativa en el resto de

variables de interés en la rigidez aórtica. De cara al tratamiento anti-

hipertensivo (que podría impactar en los resultados de las pruebas) no se

observaron tampoco diferencias significativas.

Los resultados sobre parámetros de presión arterial y rigidez arterial del estudio

mostraron que, pese a cifras similares de presión arterial, tanto a nivel

periférico como central, el Augmentation Pressure fue menor en el grupo

tratado con belatacept (P=0.048). No se detectaron diferencias en los valores

de PWV (media entre los dos grupos). Ver Tabla 5.


69

Tabla 5. Diferencias en valores hemodinámicos entre pacientes en tratamiento con ciclosporina y belatacept


Presión arterial sistólica periférica (mmHg)

137 (121-147) 128 (116-152) 0.68

Presión arterial diastólica periférica (mmHg)

78 (65-83) 77 (62-90) 0.90

Presión sistólica aortica (mmHg) 125.5 (108.3–132) 114.3 (102–132) 0.22

Presión diastólica aortica (mmHg) 77.3 (66–83) 74.7 (61.7–91) 0.78

Augmentation Pressure (mmHg) 12.7 (8.3–16) 7.3 (2.3–11.7) 0.048

Frecuencia Cardiaca (lpm) 62.3 (55.3–67.3) 71.7 (63.3–78) 0.003

PWV (m/s) 8.8 (8.1–9.5) 8.8 (7.7–9.7) 0.78


70

8.2 Estudio 2: Arterial stiffness in kidney transplantation: a single center case-control study comparing belatacept versus calcineurin inhibitor immunosuppressive based regimen

En este segundo estudio de diseño transversal se seleccionaron 24 pacientes

desde nuestro centro y tratados con belatacept, todos procedentes de los

estudios BENEFIT y BENEFIT-EXT.111, 112 De ellos 4 se descartaron: 2 por

recibir CNI en el momento del estudio, 1 por tener fibrilación auricular y 1 por

obesidad severa (IMC > 35), factores por los cuales era técnicamente imposible

efectuar el estudio de rigidez arterial. Como grupo de comparación se

identificaron 20 controles tratados con CNI (17 tratados con tacrolimus y 3 con

ciclosporina). La búsqueda de pacientes del grupo control fue efectuada

realizando un match de cada paciente del grupo de belatacept para las

variables que potencialmente influyen en la rigidez arterial: presión arterial

(mismo número de medicaciones anti hipertensivas y diferencia máxima

aceptada en presión sistólica y diastólica sistémica de 5 mmHg entre caso y

control), edad (diferencia máxima aceptada de 5 años entre caso y control),

sexo (match idéntico), tiempo desde el trasplante (6 meses de diferencia

máxima permitida entre caso y control), tiempo en diálisis (3 meses de

diferencia máxima aceptada entre caso y control), BMI (1 Kg/m2 de diferencia

máxima aceptada entre caso y control).

La Tabla 6 a continuación resume las características basales y post-trasplante

de los grupos de estudio.

Tabla 6. Características basales y post-trasplante de los grupos de estudio

CNI (20) BLC (20) p.

Edad (años ± DS) 56,2 ± 13,7 53,6 ± 13,2 0.77

Tiempo desde el Trasplante (mediana meses/Rango) 61 [45-113] 61 [35-118] 0.33

Sexo (H / M) % 15 / 5 12 / 8 0.31

Tiempo en Diálisis (mediana meses/Rango 17 [0-81] 22 [0 – 93] 0.59

BMI (kg/m2) 26,8 ± 4.48 25,3 ± 4.33 0.80


71

CNI (20) BLC (20) p.

HLA mismatch (mediana/Rango) 2 [1-5] 2 [2-5] 0.59

Causa de IRC (%)

No filiada 40 35 0.98

Poliquistosis 20 25 0.98

Glomerulonephritis 20 20 0.98

Nefritis intersticial 20 20 0.98

Diabetes pre-trasplante (si/no) % NODAT (si/no) %

0/20 0/20

2/20 1/20

0.14

Eventos Cardiovasculares Previos (%) 15 20 0.90

Fumador (Activo/Ex-fumador/No fumador) % 15/25/60 15/20/65 0.96

Rechazo agudo post Trasplante (%) 15 5 0.34

DGF (%) 10 15 0.64

Isquemia Fría 15,3 ± 4.6 20,5 ± 7.6 < 0.05

Índice de Resistencia intra-renal ecográfico (media±DS) 0.70 ± 0.07 0.70 ± 0.09 0.76

No se detectaron diferencias significativas para las principales variables

basales entre los dos grupos de estudio. El grupo tratado con CNI tuvo un

menor tiempo de isquemia fría (P= 0.05).

Se efectuó el test de cálculo de la velocidad de la onda de pulso. Las pruebas

fueron efectuadas por el mismo operador (E.M.). El coeficiente de variación

intra-clase para el test efectuado fue de 0.89 (IC 0.75-0.95).

Los resultados de la velocidad de la onda de pulso (media ± DS) no mostraron

diferencias significativas entre los dos grupos, aunque la prevalencia de una

PWV > 8.1 m/s (considerada como valor de corte según el estudio de Verbeke

et al.62) fue el doble en el grupo tratado con CNI con respecto al grupo tratado

con belatacept, con tendencia a la significación estadística (P= 0.08), y esto a

pesar de tener cifras de presión arterial periféricas muy parecidas. No hubo

diferencias significativas en el número y tipo de fármacos anti-hipertensivos


72

utilizados. La función renal fue ligeramente mejor en el grupo tratado con

belatacept, aunque de manera no significativa (P= 0.07). Como era de esperar,

el uso de estatinas en el grupo tratado con CNI fue superior (P= 0.05). No se

evidenciaron diferencias entre otros parámetros de laboratorio tales como

colesterol total, HDL, LDL, triglicéridos, PTH, Calcemia y fosfatemia

determinados en un periodo de entre 7 y 30 días antes de la realización del

test.

La tabla 7 muestra las características clínicas y analíticas de los dos grupos de

estudio.

Tabla 7. características clínicas y analíticas de los dos grupos de estudio

CNI (20) BLC (20) p.

HTA (%) 70 65 0.73

Numero de medicamentos anti-HTA (mediana±rango) Clase (%)

IECA o ARAII Diuréticos Calcio antagonistas Beta bloqueantes Alfa Bloqueantes Otros

Tratamiento con estatinas

1 [1-4] 35 20 50 15 15 0 11/20

1 [1-3] 30 10 30 35 10 5 5/20

0.64 0.05

Presión arterial sistólica (media±DS) 144 ± 23 139 ± 19 0.4

Presión arterial diastólica (media±DS) 83 ± 10 80 ± 11 0.4

Presión de pulso (media±DS) 61 ± 22 59 ± 20 0.8

PWV (mediana/rango) 7.9 [5.2-15.5] 7.4 [4.1-12] 0.4

PWV >8.1 m/s (%) 50 25 0.08

Proteinuria (g/mol) 21.4 ± 29.2 19.5± 25.8 0.6

eGFR (MDRD) ml/min 55,2 ± 20.9 69,3 ± 17.3 0.07

iPTH (pmol/L) 13,8 ± 6.3 11.6 ± 6.7 0.68

Colesterol total LDL HDL Triglicéridos

4.81 ± 0.8 3.06 ±0.8 1.23 ± 0.3 1.52 ± 0.5

4.89 ± 1.14 3.09 ± 1 1.34 ± 0.5 1.33 ± 0.8

0.66 0.43 0.09 0.57


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Se realizó un análisis univariante logístico binomial para identificar los

parámetros relacionados con el riesgo de padecer una PWV > 8.1 m/s.

Entre las variables evaluadas en el estudio se relacionaron con una mayor

rigidez arterial (PWV > 8.1 m/s) la edad, la presión sistólica y la presión de

pulso. También se detectó una relación entre el valor de índice de resistencia

intraparenquimatoso post-trasplante (IRR) evaluado con ecografía-doppler y la

PWV elevada. Se objetivó una tendencia a la significación estadística con el

uso de estatina (P= 0.05) respeto a mayor rigidez arterial y de belatacept (P=

0.08) que, por el contrario, resultaba ser protector respecto al valor de rigidez

arterial (OR 0.33).

Ver Tabla 8.

Tabla 8. Regresión logística binomial per PWV superior a 8.1 m/s Pulse Wave Velocity Univariante

<8.1 >8.1 OR p.

Tratamiento

CNI (%) 40 66.7

BLC (%) 60 33.3 0.33 0.08

Sexo

Hombre (%) 68 66.7

Mujer (%) 32 33.3 1.06 0.93

Edad (media±DS) 49.3 ± 12.3 65 ± 6.7 1.16 <0.01

IRR (media±DS)

Uso de estatina

No (%)

Si (%)

0.67 ± 0.08

72

28

0.76 ± 0.07

40

60

1.19

3.85

<0.01

0.05

eGFR (ml/min) 66.68 55.49 0.97 0.19

Proteinuria (Cr/Pr) 16.5 ± 18.6 35.3 ± 35.5 1.02 0.05

Presión arterial sistólica 131.2 ± 14 158.6 ± 20 1.11 <0.01

Presión de pulso 50.1 ± 10 76.4 ± 24 1.10 <0.01


74

En el análisis multivariante se evidenció como solo la edad (factor de riesgo) y

el uso de belatacept (factor protector) se mantenían significativos (P= 0.03 y P=

0.04, respectivamente). El IRR se acercó a la significación estadística (P=

0.053) Ver Tabla 9.

Tabla 9. Análisis de regresión logística binomial multivariante por riesgo de tener una PWV > 8.1 m/s.

OR P CI

Belatacept (yes vs no) 0.008 0.045 0.004 0.890

Edad* 1.24 0.033 1.017 1.528

IRR** Uso de estatina (yes vs no)

1.25 3.35

0.053 0.07

1.030 0.005

1.540 1.933

Presión de Pulso 1.08 0.09 0.98 1.02

*ORporcadaañodediferencia**ORporcada0.01dediferenciaenelIRR


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9. Discusión

La rigidez arterial ha demostrado ser un poderoso factor de riesgo

cardiovascular en pacientes trasplantados renales. Muchos factores se

relacionan con una mayor rigidez arterial, en especial aórtica. Entre los factores

modificables que se relacionan con la rigidez arterial se encuentran los

diferentes tipos de inmunosupresores. Sin embargo, la mayoría de estudios

publicados han analizado únicamente el efecto de los inmunosupresores más

utilizados: los CNI y los iMtor.

En el presente trabajo de tesis doctoral, me he centrado en estudiar el efecto

del régimen inmunosupresor libre de CNI y basado en belatacept sobre la

rigidez arterial con la hipótesis de que este podría relacionarse con una mejora

de los parámetros de rigidez arterial.

Como se comentó previamente, diferentes ensayos mostraron que los

pacientes tratados con belatacept presentaban una mejor función del injerto

renal con respecto a los pacientes tratados con ciclosporina. Además, un

análisis tras 7 años de observación del ensayo BENEFIT ha mostrado una

reducción del 43% en el riesgo de muerte y/o de pérdida de injerto para los

pacientes tratados con belatacept con respecto al régimen de ciclosporina.100

Ya que la función renal es un potente predictor de eventos cardiovasculares y

de mortalidad en los receptores de trasplante renal,113, 114 estos resultados

eran, hasta cierto punto, de esperar.

Más allá de una mejor tasa de supervivencia relacionada con un mayor filtrado

glomerular, otros datos apuntan a la posibilidad de que se alcance un mejor

control de la rigidez arterial en un régimen basado en belatacept. En un modelo

experimental de hipertensión inducida por sal y acetato de desoxicorticosterona

(DOCA), Vihn et al suministraron un tratamiento basado en CTLA4-Ig (un

fármaco similar a belatacept en cuanto al mecanismo de acción, cuyo efecto es

imitado por deficiencia genética CD/80/CD86) en ratones, evitando la

aceleración de la hipertensión. 115 Una posible influencia del sistema

inmunitario en la hipertensión no es una novedad. Hace más de 25 años se


76

describió que las células T participan en la hipertensión inducida por sal y

DOCA en ratones timectomizados.116 Más recientemente, Guzir et al, en un

modelo de hipertensión arterial inducida por angiotensina II, han demostrado la

importancia de los linfocitos (sobretodo T) en el desarrollo de la hipertensión

arterial sistémica.117 En la hipertensión leve, los daños en el endotelio vascular

causan liberación de DAMPs (damage-associated molecular patterns) y de

auto-proteínas alteradas. Hipotéticamente, todas estas moléculas podrían ser

antígenos presentados por células dendríticas y activar el sistema inmunitario,

activando las células T y estimulando la producción de citoquinas y la

inflamación,118 siendo esta última la estrechamente relacionada con el aumento

de la rigidez vascular.12

Desde una perspectiva clínica, solo los dos estudios publicados por nuestro

grupo (uno conjuntamente con un grupo alemán) y que conforman esta tesis

doctoral, han analizado el impacto del belatacept en la rigidez arterial en

receptores de trasplante renal.

Ambos estudios han evaluado la rigidez arterial utilizando la metodología

considerada como el patrón oro en la medición no invasiva de la rigidez arterial.

Se han evaluado diferentes grupos de pacientes tratados con belatacept y CNI

(tacrolimus y ciclosporina), que reflejaban el elevado riesgo cardiovascular

típico de los trasplantados renales, puesto que la prevalencia de eventos

cardiovasculares previo al trasplante se situó entre el 15 y el 20% en ambos

estudios. Cabe destacar también que el tiempo después del trasplante renal

fue suficientemente largo para detectar posibles diferencias en velocidad de la

onda de pulso, parámetro que suele modificarse a lo largo de los años.

Aunque ambos estudios no encontraron diferencias significativas en las medias

de PWV en los diferentes grupos (belatacept, ciclosporina, tacrolimus), cabe

destacar que, debido a la amplia variación en la edad de los pacientes

incluidos, es probable que el número de pacientes evaluados para detectar

diferencias significativas, por lo menos en sus valores medios, no fuese

suficiente. Desafortunadamente, el número de pacientes tratados con

belatacept es aún escaso, debido principalmente a su coste y a la falta de

nuevos ensayos clínicos.103 Debido a estas limitaciones, decidimos efectuar un


77

análisis de los pacientes utilizando un valor de corte de PWV bien establecido y

analizar la prevalencia de pacientes con valores superiores a dicho valor de

corte en dos grupos (belatacept vs CNI-principalmente tacrolimus). La elección

del valor de corte de 8.1 m/s se basó en un estudio anteriormente publicado

por otro grupo que mostraba como, a partir de este valor, el riesgo

cardiovascular aumentaba progresivamente en pacientes trasplantados

renales.62 Aunque este valor es ligeramente inferior al punto de corte de 10 m/s

establecido para pacientes hipertensos,47 está ampliamente documentado que

la relación entre el riesgo cardiovascular y la PWV es lineal. Además, parece

lógico que, en un grupo de pacientes con una prevalencia elevada de eventos

cardiovasculares previos al trasplante, un valor de corte de 10 m/s puede ser

insuficientemente sensible para determinar el riesgo cardiovascular, aunque

este punto requeriría un estudio al respecto.

Los resultados más importantes de ambos estudios fueron que los pacientes

tratados con belatacept presentaron una menor prevalencia de rigidez arterial

elevada con respecto a los tratados con CNI (estudio 2) y que también, pese a

no identificar diferencias significativas en los valores presión arterial sistémica,

el grupo de pacientes tratados con belatacept presentaba parámetros de

augmentation pressure inferiores (estudio 1).

Además, en el análisis multivariante del estudio 2, el tratamiento con belatacept

resultó ser predictor independiente de una PWV< 8.1 m/s. Entre las otras

variables, como era de esperar, también la edad del paciente y la presión

arterial sistémica fueron predictores independientes de la PWV. Aunque la

relación entre presión arterial sistémica y velocidad de la onda de pulso es bien

conocida, recientemente una publicación procedente del estudio Framingham

mostró como pacientes con una rigidez arterial basal ligeramente elevada

desarrollaban, tras un largo tiempo de observación, hipertensión arterial,

mientras que la presión arterial basal no era capaz de predecir el proceso de

rigidez. 119

La mayor limitación de ambos estudios fue no disponer de datos basales de

PWV debido al diseño transversal, de manera que no pudimos concluir si la

rigidez arterial fue la causa o la consecuencia de la hipertensión arterial. No


78

obstante, hay que remarcar que la hipertensión arterial en los pacientes

incluidos en ambos estudios estaba bien controlada, ligeramente a favor del

grupo tratado con belatacept, pero sin alcanzar diferencias estadísticamente

significativas. Hay que tener en cuenta que el efecto sobre la presión arterial de

los dos inhibidores de la calcineurina es bastante diferente, teniendo la

ciclosporina un perfil más desfavorable comparado con el tacrolimus. 120

Considerado que la mayoría de pacientes del grupo control tratado con CNI en

el estudio 2 recibió tratamiento con tacrolimus, nuestros resultados sugieren

que el efecto beneficioso del belatacept sobre la velocidad de onda de pulso es

independiente de un mejor control presión arterial. Por otro lado, en el estudio 1

se remarca como, más allá del aumento de la presión sistólica de los pacientes

tratados con ciclosporina (otra vez, no estadísticamente significativo), se

objetivó una diferencia significativa en la AP a favor del grupo tratado con

belatacept. De hecho, la ciclosporina aumenta el Aix y/o la augmentation

pressure principalmente por su efecto vasoconstrictor y pro arteriosclerótico.

Los pacientes tratados con belatacept en ambos estudios presentaban valores

de función renal mejores con respecto a sus controles (tanto con ciclosporina

como con tacrolimus) aunque la diferencia no fue estadísticamente significativa.

En el estudio 2, la función renal no resultó ser predictor de PWV,

probablemente por un número insuficiente de pacientes o más bien debido al

hecho de que la mayoría de pacientes tenían un filtrado glomerular preservado

(alrededor de 60 ml/min). El estudio 2 también evidenció una correlación entre

proteinuria y PWV. Una rigidez arterial elevada se ha relacionado con

proteinuria en pacientes hipertensos. 121 Sin embargo, en pacientes

trasplantados renales la proteinuria suele ser de origen multifactorial y,

evidentemente, consecuencia y no causa de elevada rigidez arterial, tal como

ha mostrado el análisis multivariante.

Un interesante aspecto no esperado de nuestro estudio (estudio 2) resultó ser

la relación entre el índice de resistencia intra-renal medido a través de la

ecografía doppler después del trasplante renal (3 meses) y la rigidez arterial.

Cada reducción de 0.01 en el índice de resistencia renal fue asociada con una

reducción del 19 % de probabilidad de desarrollar una elevada rigidez arterial.

Otros autores han demostrado la relación entre el índice de resistencia renal y


79

la velocidad de la onda de pulso en pacientes hipertensos, 122 y más

recientemente, el índice de resistencia renal medido después del trasplante

renal ha demostrado ser predictor independiente de mortalidad.123 Naessens M

et al. relacionan el índice resistencia renal con la edad del receptor y la presión

de pulso y no con las características del órgano, y por esa razón sería capaz

de predecir mortalidad.123 En nuestro estudio (Estudio 2) no había diferencias

en el índice de resistencia renal a 3 meses del trasplante renal entre los dos

grupos de estudio. Este dato sugiere indirectamente que los dos grupos de

pacientes, los tratados con belatacept y los tratados con CNI, al tiempo de la

realización de la ecografía-doppler no presentaban diferencias relevantes en la

velocidad de onda de pulso y, por lo tanto, refuerza nuestra conclusión.

Finalmente, en el estudio 2, entre los factores de riesgo cardiovasculares, el

uso de estatinas fue relacionado con una mayor rigidez arterial al análisis

univariante pero no al multivariante, indicando que pacientes con mayores

lesiones vasculares (mas añosos y/o con elevada rigidez arterial) son más

propensos a recibir estatinas.

Ambos estudios presentan algunas limitaciones, una de ellas apuntada

previamente. Primera, el diseño de ambos estudios es transversal y caso-

control y, segunda, el número de pacientes fue limitado. Cabe destacar que

actualmente el uso de belatacept está restringido en España y que los estudios

publicados y/o en fase activa que utilizan un régimen basado en la inhibición de

la señal de la coestimulación124 no están evaluando los parámetros de rigidez

arterial, por lo tanto, es muy probable que los resultados presentados en esta

tesis representarán los estudios más grandes en este campo en los próximos

años.


80


81

10. Conclusiones

• Los pacientes trasplantados renales tratados con belatacept

comparados con aquellos tratados con ciclosporina, tras un tiempo de

observación de 81 meses, presentan valores de augmentation pressure

inferiores

• La prevalencia de una rigidez aórtica elevada (>8.1 m/s) tras un

seguimiento de 61 meses tras el trasplante renal, fue superior en los

pacientes tratados con CNI respecto a aquellos que recibieron

belatacept (50% vs 25 %, respectivamente). Aunque este dato no

alcanzó significación estadística, (P= 0.08), puede ser considerado como

clínicamente relevante.

• El uso de belatacept resultó ser una factor protector en el desarrollo de

elevada rigidez aórtica tras el trasplante renal.

• En pacientes trasplantados renales, la proteinuria se relaciona con la

velocidad de onda de pulso.

• La edad de los receptores y los índices de resistencia renales fueron

variables predictivas de elevada rigidez arterial

• No se objetivó diferencia en los valores de PTH en los pacientes

tratados con belatacept frente a CNI. No se objetivó relación entre PTH y

valores de rigidez arterial.

• No se objetivaron diferencias significativas en los valores de colesterol

en pacientes tratados con belatacept frente a CNI, aunque estos últimos

necesitaron un mayor uso de statinas. No se objetivó relación entre

valores de colesterol y parámetros de rigidez arterial.


82


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