Expresión de genes citoprotectores y de regeneración celular tras el síndrome de isquemia-reperfusión en un modelo experimental de trasplante renal con donantes a corazón latiente y parado

Abstract

Se planteó la siguiente hipótesis de trabajo: la isquemia caliente que sufren los donantes a corazón parado altera negativamente la expresión de ciertos genes citoprotectores y de regeneración tisular. <br/>Con los siguientes objetivos: Determinar la expresión de genes citoprotectores durante el trasplante renal y a los cinco días postrasplante. Establecer el efecto de diferentes tiempos de isquemia caliente y del tratamiento inmunosupresor sobre la expresión estos genes.<br/><br/>El modelo experimental de trasplante renal incluye cuarenta pares de cerdos en dos grupos de donantes a corazón parado y latiente. El período de isquemia fría es el mismo para todos los grupos, mientras que la isquemia caliente se divide en tres grupos: 30, 45 y 90 minutos. La terapia inmunosupresora consiste en ciclosporina, excepto en un grupo de donantes a corazón latiente que fue tratado con azatioprina. Los perfiles de expresión de TGF-beta 1, TSP-1, HIF-1, NOS2, NOS3, HO-1, y 18s rRNA se determinaron por PCR cuantitativa en las biopsias corticales recogidas tras la inducción anestésica, tras la isquemia caliente, tras la reperfusión en el receptor y al quinto día posterior al trasplante.<br/><br/>Globalmente los resultados de la presente tesis muestran que tiempos cortos de isquemia caliente afectan a la expresión génica de factores implicados en la supervivencia celular, así como de factores parcialmente responsables de la regeneración tisular. Este estudio ayuda a explicar la mayor frecuencia de retraso de función del injerto que se observa en los pacientes con órganos de donantes a corazón parado. <br/><br/>FUENTES:<br/><br/>1. Expression of transforming growth factor-beta 1 and hypoxia-inducible factor-1beta in an experimental model of kidney trasplantation. Lario S, Mendes D, Bescós M, Iñigo P, Campos B, Alvarez R, Alcaraz A, Rivera-Fillat F, Campistol JM. Transplantation 2003; 75: 1647-1654.<br/><br/>2. Thrombospondin-1 mRNA expression in experimental kidney transplantation with heart- and non-heart beating donors. Lario S, Bescós M, Campos B, Mur C, Luque P, Alvarez R, Campistol JM. J Nephrol 2007; 20: 588-595.

<i>"Expression of cytoprotective genes during experimental kidney transplantation with heart- and non-heart beating donors."<br/><br/>TEXT:<br/><br/>Background: Ischemia-reperfusion (IR) is a risk factor for delayed graft function, a clinical syndrome more frequently observed in non-heart beating donors (NHBD). Hypoxia-inducible factor 1 (HIF-1) activates transcription of several genes implicated in cell survival, such vascular endothelial growth factor (VEGF), and tissue repair, such transforming growth factor-beta (TGF-beta) isoforms. TGF-beta 1 has a central role in the restoration of renal function after ischemia-reperfussion. The aim of the present study was to characterize TGF-beta 1 and HIF-1 beta related genes during renal transplantation with heart (HBD) and non-heart beating donors (NHBD).<br/><br/>Methods: The experimental pig model of kidney transplantation comprised heart beating donors (HBD, n=9) and NHBD (n=22). Cortical biopsies were collected after anesthetic induction (basal), after warm ischemia (WI), after cold ischemia (CI), after 1 hour of reperfusion (1R) and five days (5D) after transplantation. Immunosupressive therapy consisted of cyclosporine, except one HBD group treated with azathioprine. Thrombospondin-1, TGF-&#61538;1 and HIF-1beta controlled genes (VEGF, HO-1, NOS-2, NOS-3) mRNA expression was determined by real-time PCR. <br/><br/>Results: TGF-beta 1 expression increased after the cold ischemia period in HBD and remained unaltered during surgical process in all NHBD groups. HIF-1 beta and VEGF expression were not greatly modified in biopsies obtained during surgery in neither HBD nor NHBD groups. All groups showed a significantly increase in TGF-beta 1 and HIF-1beta expression and a down-regulation of VEGF five days after transplantation, independently of the immunosupressive treatment. There were no statistically differences among the groups at five days, although the increase of TGF-beta 1 was more pronounced in HBD groups, especially in those animals treated with azathioprine. TSP-1 mRNA was significantly increased at 5D in NHBD animals but was unchanged in the HBD group. HO-1 was upregulated in HBD (p<0.05) and NOS2 mRNA was significantly increased in both groups. No difference in NOS3 expression was observed at 5D.<br/><br/>Conclusions: The initial up-regulation of TGF-beta 1 observed in HBD just after cold ischemia could have a positive action on epithelial tubular regeneration. Warm ischemia has a detrimental effect on TGF-beta 1 expression during the early phases of renal transplantation, having no effect on VEGF and HIF-1&#61537; expression. The up-regulation of TGF-&#61538;1 and HIF-1&#61537; observed in the days after transplantation could have a positive effect on tubular repair. TGF-&#61538;1 expression was lower in animals treated with cyclosporine, probably related to cellular toxicity or arteriolar vasoconstriction, explaining in part the frequent and severe delayed graft function observed in non-heart beating renal transplantation. The increased TSP-1 expression in NHBD may indicate a compensatory response to the reported diminished TGF-beta1 expression. The augmented NOS2 and HO-1 expression in HBD could have a positive effect on the recovery of kidney function. </i>