EFFECT OF BRAIN DEATH ON GENE EXPRESSION AND TISSUE ACTIVATION IN DONOR KIDNEYS

Abstract

O47 Aims: After kidney transplantation, a decreased graft survival and increased chronic rejection rate are seen when grafts from brain dead donors are compared to those from living donors. Previously, we showed in our animal brain death model a nonspecific and progressive tissue and endothelial activation as a first trigger of organ damage. In this study, we focused on the effects of brain death on the inflammatory response (adhesion molecules, leucocyte invasion, gene expression) and on stress related genes encoding heat shock proteins in humans. Outcomes were correlated with clinical parameters of the brain dead donors and the corresponding kidney recipients. Methods: From 1998 until now, kidney biopsies have been obtained during organ retrieval from brain dead and living human organ donors. Biopsies were snap frozen and used for immunohistochemistry. Further, mRNA was isolated for RT-PCR. Results: Kidneys derived from living donors showed less delayed graft function (p<0.05) and a tendency towards better patient survival after one year (p=0.06). After brain death, immunohistochemistry showed an increase of e-selectin (p<0.01) and interstitial leukocyte invasion (p<0.05) vs controls. ICAM and VCAM levels were similar in both groups. Also, semi-quantitative RT-PCR using gene-specific primers showed that levels of MCP-1 were twice as high in brain dead donor kidneys, but did not reach significance (p=0.07). No differences however were found for expression levels of IL-1, IL-6, IL-8, TGF-β and iNOS. Levels of TNF-α expression remained inconclusive. A 3-fold increased expression after brain death of genes encoding the heat shock proteins HO-1 (p<0.05) and Hsp70 (p<0.01) was seen. In the brain dead group, higher levels of e-selectin and interstitial leucocyte invasion were typically seen in kidneys from donors with low blood pressures during ICU stay and donor operation. However, this didn’t seem to affect recipient and graft survival at 1 and 3 years. Further, brain dead kidney donors with ASAT and ALAT serum levels above reference values (ASAT >40 iu/L, ALAT >30 iu/L) showed a strong relation with increased (>5-fold, p<0.01) HO-1 expression while normal serum injury levels correlated with a lower HO-1 expression (2-fold, p<0.05). In recipients of living donor kidneys, higher HO-1 levels in graft resulted in lower serum creatinine levels one and three years after transplantation (p<0.05). Grafts from brain dead donors did not show this effect. Conclusions: The presence of interstitial leukocytes and the early adhesion molecule e-selectin in brain dead donor kidneys indicate an early phase inflammatory process during organ retrieval. Elevated levels of MCP-1 are seen and suggest a role for monocytes/macrophages in this phase. In addition, a significant upregulation of genes encoding the heat shock proteins HO-1 and Hsp70 was found after brain death. We speculate that brain death induces a stress related response against which protective proteins in the future graft are formed. However, this response might not be enough to counteract the harmful effects of brain death. Which systemic and/or local factors trigger BD related graft injury is currently under investigation.