Subnormothermic Ex Vivo Porcine Kidney Perfusion Improves Energy Metabolism: Analysis Using 31P Magnetic Resonance Spectroscopic Imaging

Abstract

Background. The ideal preservation temperature for donation after circulatory death kidney grafts is unknown. We investigated whether subnormothermic (22 °C) ex vivo kidney machine perfusion could improve kidney metabolism and reduce ischemia-reperfusion injury. Methods. To mimic donation after circulatory death procurement, kidneys from 45-kg pigs underwent 60 min of warm ischemia. Kidneys were then perfused ex vivo for 4 h with Belzer machine perfusion solution UW at 22 °C or at 4 °C before transplantation. Magnetic resonance spectroscopic imaging coupled with LCModel fitting was used to assess energy metabolites. Kidney perfusion was evaluated with dynamic-contrast enhanced MRI. Renal biopsies were collected at various time points for histopathologic analysis. Results. Total adenosine triphosphate content was 4 times higher during ex vivo perfusion at 22 °C than at 4 °C perfusion. At 22 °C, adenosine triphosphate levels increased during the first hours of perfusion but declined afterward. Similarly, phosphomonoesters, containing adenosine monophosphate, were increased at 22 °C and then slowly consumed over time. Compared with 4 °C, ex vivo perfusion at 22 °C improved cortical and medullary perfusion. Finally, kidney perfusion at 22 °C reduced histological lesions after transplantation (injury score: 22 °C: 10.5 ± 3.5; 4 °C: 18 ± 2.25 over 30). Conclusions. Ex vivo kidney perfusion at 22°C improved graft metabolism and protected from ischemia-reperfusion injuries upon transplantation. Future clinical studies will need to define the benefits of subnormothermic perfusion in improving kidney graft function and patient’s survival.

Sodium Hydrosulfide Treatment During Porcine Kidney Ex Vivo Perfusion and Transplantation

“…Next, mean ATP levels were measured by averaging pMRSI voxels containing graft tissue. 13,16 Alpha (α), beta (β), and gamma (γ) ATP, and phosphomonoesters containing AMP, were similar in both groups (Figure 1C). Similarly, post-autotransplantation, cortical and medullary flow (Figure 1D), and ATP levels (Figure 1E) were similar in both control-and NaHStreated kidneys.…”

Kidney Preservation Strategies to Improve Transplant Outcomes

“…Subnormothermic (21-22°C) machine perfusion was proposed as an alternative to perfusion at 37°C. 10 Subnormothermia aims to avoid cold-induced graft injury without increasing metabolism to a level requiring oxygen carriers for adequate oxygenation. 10 Perfusion of a cell-free, oxygenated perfusate at 22°C promoted mitochondrial respiration and ATP stores before transplantation.…”

“…10 Subnormothermia aims to avoid cold-induced graft injury without increasing metabolism to a level requiring oxygen carriers for adequate oxygenation. 10 Perfusion of a cell-free, oxygenated perfusate at 22°C promoted mitochondrial respiration and ATP stores before transplantation. Overall, preclinical studies suggest that 22°C might be the optimal temperature to protect against ischemia-reperfusion injury in the kidney while avoiding complex machines used for normothermic perfusion.…”

Acellular Perfusate is an Adequate Alternative to Packed Red Blood Cells During Normothermic Human Kidney Perfusion

“…8,9 In porcine preclinical models, NMP reduced graft injury and improved kidney function after kidney transplantation. 2,6 Consistently, in donated after circulatory death (DCD) pig kidneys, NMP improved early creatinine clearance and reduced apoptosis compared with SCS. 9 In a recent clinical study, short-term NMP after HMP appeared to reduce DGF rate, although no difference was observed at the 1-y follow-up.…”

“…4,5 To reduce cold ischemia, normothermic (37 °C) machine perfusion (NMP), with "blood-mimicking perfusate," containing packed red blood cells (RBCs) with or without fresh frozen plasma, has shown great promise. 2,6 Although cold anoxic storage aims to arrest cell metabolism, NMP provides a continuous flow of warmed, oxygenated perfusate containing nutritional substrates, thereby maintaining the metabolic activity of the kidney. 7 In addition, NMP allows graft assessment, reconditioning, and repair.…”