21°C is the emerging ideal temperature for kidney preservation in the presence of hydrogen sulfide

Kidney transplantation is the treatment of choice for patients with end-stage kidney disease. However, the shortage of transplantable kidneys has led to ever-increasing waiting lists. As a result, kidneys obtained via donation after cardiac death (DCD) are being used more frequently for transplantation. However, they exhibit poorer outcomes due to ischemia-reperfusion injury (IRI) and cold preservation methods, such as static cold storage (SCS). Supplementing cold preservation solutions with hydrogen sulfide donors, such as AP39, has been shown to improve renal IRI and graft outcomes, but the injury associated with cold preservation remains. This thesis evaluates the effect of subnormothermic kidney preservation at 21°C with AP39. In an in vitro model of renal IRI, adding AP39 to University of Wisconsin (UW) solution improved its viability for subnormothermic preservation at 21°C in a dose-dependent manner. Additionally, subnormothermic storage of DCD porcine kidneys in AP39-supplemented UW solution reduced necrosis compared to SCS in UW alone. Since oxygenated perfusion is the norm for normothermic (35-37°C) and subnormothermic (20-34°C) kidney preservation research, AP39-supplemented autologous blood was used for the ex vivo perfusion of DCD porcine kidneys at 21°C. The treatment group exhibited higher urine output, lower tissue injury and pro-survival gene expression patterns compared to subnormothermic perfusion with blood alone and SCS. Seeing as the use of blood would complicate the clinical translation of our approach due to national shortages and logistical complexities, we investigated the effect of adding AP39 to Hemopure, a hemoglobin-based oxygen carrier. Subnormothermic perfusion of DCD porcine kidneys with AP39-suppelemted Hemopure improved renal graft function and reduced tissue injury in a similar manner as in the previous model. Several important conclusions emerged. Adding 200 nM AP39 to preservation solutions, blood and blood substitutes improved renal outcomes. Importantly, oxygenated subnormothermic perfusion with AP39-supplemented perfusates improved DCD kidney outcomes compared to SCS, the clinical standard of care. Additionally, subnormothermic preservation with AP39 reduced renal apoptosis and induced pro-survival gene expression. Overall, we transformed a novel idea into a viable kidney preservation approach that is pending patent approval. If clinically approved, this approach could facilitate the increased use of DCD kidneys for kidney transplantation