Analysis of DCD porcine kidney graft viability during sub-normothermic perfusion using magnetic resonance imaging and spectroscopy

Abstract

Abstract Objective Better preservation strategies for the storage of donation after circulatory death grafts could increase the number of kidneys available and improve patient survival. Warm (22°C and 37°C) ex-vivo perfusion has emerged as an alternative to hypothermia and a feasible strategy to recover/repair organs, but the underlying mechanism remains elusive. Here, using magnetic resonance imaging spectroscopy (MRIs), we evaluated kidney viability, and adenosine triphosphate (ATP) production during sub-normothermic ex-vivo kidney perfusion (22°C + O2) versus hypothermic machine perfusion (4°C and 4°C + O2) in a porcine kidney autotransplantation model. Methods To mimic donation after circulatory death (DCD), kidneys from 8-month-old pigs underwent 60 minutes of warm ischemia, prior to procurement. Kidneys were then perfused ex-vivo at 4°C with (4°C + O2), and without oxygen (4°C) or at 22°C (22°C + O2) before autotransplantation. During the ex-vivo perfusion, and after transplantation we assessed energy metabolites using MRIs. In addition, we performed Gadolinum (Gd) perfusion sequences. Each sample underwent histopathological analyzing and scoring. mRNA expression was analyzed on renal biopsies at various time points. Results Using MRI, we found that in pig kidney, total ATP content was 4 times higher during ex-vivo perfusion at sub-normothermic temperature compared to cold perfusion, with or without oxygen. At 22°C, ATP levels gradually increased up to 10 hrs of perfusion, then progressively declined. Similarly, AMP content was increased in SNOP perfused organs, then slowly consumed. over time. In addition, 22°C + O2 improved cortical and medullary perfusion (Gd elimination). Finally, sub-normothermic ex-vivo perfused graft had lower grade of histological damages 1 hour after transplantation compared to cold perfused organs (injury score 22°C + O2 : 8.8–12.2, 4°C : 13.5–18.8, 4°C + O2 : 17.5–18.5). Conclusion In kidneys, sub-normothermic perfusion improved graft viability when compared with hypothermic perfusions. These results suggest that sub-normothermic ex-vivo kidney perfusion might dampen the negative effect of warm ischemia and promote kidney metabolism such as ATP production. Future clinical studies will define the benefits of sub-normothermic ex-vivo kidney perfusion in improving kidney graft function, and patient's survival.