Prevention of postischemic acute renal transplant failure

Background: Renal transplantation is the treatment of choice for end stage renal disease. Although major achievements in immunosuppression have been accomplished, chronic transplant nephropathy is the main cause of graft loss and short transplant half live. The main risk factor for chronic transplant failure is postischemic acute renal failure (ARF), occurring in about 40 % of all cadaveric allograft recipients. The primary victims of renal hypoxia are tubule epithelial cells, which undergo apoptosis. We have shown, that the development of ARF can be predicted by the number of apoptotic tubule epithelial cells in donor kidney biopsies. Three Specific Aims: 1. To identify the genome wide gene expression pattern in cadaveric donor kidney biopsies with ARF compared to primary function using DNA microarrays. Differential regulation of Bcl-2 family members among the groups will be analyzed by clustering and segmentation (inductive modeling). 2. To design specific antisense oligonucleotides against several apoptosis promotor genes of the Bcl-2 family and evaluate their efficacy in cell culture by high throughput methods. 3. To evaluate the effect of the oligonucleotides in a rat model of ARF. Experimental Design I Methods: A human donor kidney biopsy bank was set up by us over the last three years in Vienna. Tubule cells were isolated from the frozen specimen by LCM. A genome wide gene expression analysis will be conducted using DNA microarrays, and sophisticated bioinformatics to identify promising targets in the Bcl-2 family. Modified antisense oligonucleotides will be designed by computational modeling, and their antiapoptotic efficacy evaluated in cell culture experiments using human primary tubule epithelial cells. The in vivo "Proof of Concept" will be performed in a rat model of postischemic acute renal failure. Expected Value of the Proposed Project: The annual cost of hemodialysis are roughly 45000 EURO per person. Currently about 350 renal transplantations are performed annually in Austria. Every year of extended allograft function gained by the proposed procedure, would result in savings of more than 40000 EURO per patient, yielding a total of over 14 million EURO.

The key objective of this proposal was to identify factors in donor kidneys that are associated with impaired renal transplant function in the recipient. This issue is of main interest since roughly one quarter of transplant kidneys develop delayed allograft function after transplantation. This scenario is highly associated with reduced long term graft and patient survival. So far no clinically established therapy or preventive measure exist to counterbalance this event. We specifically addressed this question in an open cohort study of human kidney transplant donors and recipients with the ambitious aim to develop and evaluate a prevention strategy based on the data derived in the present project. We studied the genome-wide gene expression profiles in human cadaveric and living donor kidney biopsies obtained before transplantation. Sophisticated bioinformatics and statistical analyses were applied to derive biologically sound results. Data from these analyses were associated with the post transplant course of the recipient. The main finding was that a unique molecular signature distinguished kidneys with subsequent primary function from those with acute allograft failure. The majority of subjects with acute allograft failure eventually will recover function but long term graft function is impaired in such cases. Furthermore, we could show that such a genetic profile is useful in the identification of kidneys with subsequent impaired mid-term graft function. The key differences in the gene ontologies between well and impaired functioning transplants was the activation of the inflammation cascade. Based on these findings we put together a grant application aiming for an extension of the current protocol from 2006 to 2008. It sounded obvious to us that if inflammation in the donor kidney (present before transplantation) is the key indicator of subsequent poor function, immunosuppression of the cadaveric donor before organ harvest might be a rational intervention to ameliorate the high rate of impaired allograft function. In the extension study of project P15679, which was generously funded by the FWF (P- 18325) from late 2005 to 2008, we will specifically elucidate whether the infusion of 1000mg of methylprednisolone or placebo into the cadaveric donor six hours before organ retrieval will reduce the rate of acute renal allograft failure from currently 30 to 15%. The required samples size was calculated to be roughly 400, thus a multicenter approach was chosen. The required safety interim analysis of the first 50 randomized cases was conducted in calendar week 23 of 2006 and showed very promising results.