Comparison of competing ex vivo preservation techniques and investigation of the mechanisms of graft recovery during ex-vivo perfusion in marginal kidney grafts

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Kidney transplantation represents the treatment of choice for end-stage renal disease. The enormous gap between supply and demand has lead to the more frequent use of organs from extended criteria and donation after circulatory death. A major problem with these marginal grafts is delayed graft function due to an increased susceptibility to ischemia and reperfusion injury, which leads to decreased long-term function. Therefore, the transplant community has focused its efforts on investigating methods for improving the function of these grafts. Normothermic ex-vivo kidney perfusion and oxygenated hypothermic perfusion are promising options to achieve that. In a porcine model of donation after circulatory death, studies have shown that marginal grafts subjected to normothermic ex-vivo kidney perfusion instead of the traditional cold storage demonstrate improved function of the grafts. Also, there is evidence from other animal studies that oxygenated hypothermic perfusion is superior to cold storage. The objective of the present research project is to investigate which method offers the best option for kidney preservation and which mechanisms are involved in the improved donation after circulatory death graft function in perfused grafts over static cold storage. We hypothesize that providing oxygen to the grafts prevents anaerobic metabolism, which results in a reduction in mediators involved in ischemia-reperfusion. However, other novel pathways may also be implicated. Therefore, we will initiate an unbiased examination of gene expression through microarray analysis, to then validate the results using quantitative polymerase chain reaction and then correlate these results with appropriate protein expression studies such as through enzyme-linked immunosorbent assays and Western blots. Also, potential biomarkers that correlate with improved graft function can be identified and these markers may then be utilized to assess the function and health of marginal grafts undergoing ex-vivo perfusion prior to transplant in patients. Finally, we will investigate whether a combination of oxygenated hypothermic perfusion and normothermic ex-vivo kidney perfusion offers a better preservation method in marginal grafts. The results of this study will support the translation of oxygenated hypothermic perfusion and normothermic ex-vivo kidney perfusion to human studies, and a personalized approach could be adopted as marginal grafts deemed unfit for transplant may be subjected to oxygenated hypothermic perfusion and normothermic ex-vivo kidney perfusion for restoration, improvement and assessment of graft function prior to transplantation.