Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Microbiology and Immunology

Supervisor

Sener, Alp

Abstract

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.

Summary for Lay Audience

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. Kidneys from deceased donors are being used more frequently to meet the demand. Unfortunately, these kidneys typically exhibit poorer outcomes than kidneys from living donors and thousands of these kidneys are discarded each year due to logistical limitations and strict selection criteria. As such, strategies that can improve the outcomes and facilitate the use of more deceased donor kidneys are of interest. One factor that contributes to the poor outcomes of these kidneys is cold preservation from the time of retrieval until transplantation. Our research has shown that adding hydrogen sulfide donors to cold preservation solutions improves kidney graft outcomes. However, the premise of cold preservation still causes tissue damage. Thus, the aim of this thesis is to evaluate the impact of kidney preservation around room temperature (21°C) with the use of a hydrogen sulfide donor called AP39. We used a combination of cellular and pig kidney perfusion models to investigate the effect of adding AP39 during kidney preservation at 21°C. We found that adding AP39 to preservation solutions, blood and blood substitutes improved their suitability for kidney preservation at 21°C. Importantly, kidney preservation at 21°C improved renal graft function and reduced kidney injury compared to cold storage, the clinical standard of care, in our pig kidney perfusion models. Additionally, AP39 reduced kidney injury and induced pro-survival gene expression in this context. Overall, we transformed a novel yet obscure idea into a viable and effective kidney preservation approach that is pending patent approval. If clinically approved upon testing with discarded human kidneys, this approach could facilitate the increased use of deceased donor kidneys for kidney transplantation.

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