The Effects of Oxygenation on Ex Vivo Kidneys Undergoing Hypothermic Machine Perfusion

Abstract

Background Supplemental oxygenation of the standard hypothermic machine perfusion (HMP) circuit has the potential to invoke favorable changes in metabolism, optimizing cadaveric organs before transplantation. Methods Eight pairs of porcine kidneys underwent 18 hours of either oxygenated (HMP/O2) or aerated (HMP/Air) HMP in a paired donation after circulatory death model of transplantation. Circulating perfusion fluid was supplemented with the metabolic tracer universally labeled glucose. Perfusate, end-point renal cortex, and medulla samples underwent metabolomic analysis using 1-dimension and 2-dimension nuclear magnetic resonance experiments in addition to gas chromatography-mass spectrometry. Analysis of 13C-labeled metabolic products was combined with adenosine nucleotide levels and differences in tissue architecture. Results Metabolomic analysis revealed significantly higher concentrations of universally labeled lactate in the cortex of HMP/Air versus HMP/O2 kidneys (0.056 mM vs 0.026 mM, P < 0.05). Conversely, newly synthesized [4,5-13C] glutamate concentrations were higher in the cortex of HMP/O2 kidneys inferring relative increases in tricarboxylic acid cycle activity versus HMP/Air kidneys (0.013 mmol/L vs 0.003 mmol/L, P < 0.05). This was associated with greater amounts of adenoside triphosphate in the cortex HMP/O2 versus HMP/Air kidneys (19.8 mmol/mg protein vs 2.8 mmol/mg protein, P < 0.05). Improved flow dynamics and favorable ultrastructural features were also observed in HMP/O2 kidneys. There were no differences in thiobarbituric acid reactive substances and reduced glutathione levels, tissue markers of oxidative stress, between groups. Conclusions The supplementation of perfusion fluid with high-concentration oxygen (95%) results in a greater degree of aerobic metabolism versus aeration (21%) in the nonphysiological environment of HMP, with reciprocal changes in adenoside triphosphate levels.

Genetic Engineering of the Kidney to Permanently Silence MHC Transcripts During ex vivo Organ Perfusion

“…In order to minimize the risks for cell damage during perfusion, the perfusion solution was oxygenated in our system. Previous studies have indicated the benefits of oxygenating the perfusion solution already during hypothermic perfusion by reducing oxidative stress and supporting the energy status in presence of low metabolic rates (50,51). During sub-normothermic to normothermic perfusion the increased metabolism demands an appropriate oxygen supply, but recent studies indicate that normothermic perfusion with reduced perfusate oxygenation for a limited period of time may also be possible without severely compromising renal function or tissue integrity (52).…”

Machine preservation of extremities

“…HMP relies on decreased baseline metabolism and decreased oxygen demand in hypothermic conditions. The oxygenation of perfusate is the result of passive diffusion from the air contained within the reservoir . As a result, the typical HMP devices do not need to have an oxygenator.…”

“…The oxygenation of perfusate is the result of passive diffusion from the air contained within the reservoir. 32 As a result, the typical HMP devices do not need to have an oxygenator. However, the need for oxygen persists because the metabolic rate remains at levels estimated around 10% 33 and several studies have shown the benefits of oxygenation during HMP.…”

ShearFAST: a user-friendlyin vitrotoolset for high throughput, inexpensive fluid shear stress experiments

“…The presence of fluid flow via low pressure (30 mmHg) pulsatile perfusion is a definitive difference that separates hypothermic machine perfusion (HMP), a mode of ex-vivo organ preservation, from more traditional static cold storage techniques. Preservation using HMP results in more favorable post-transplant outcomes when compared to static storage (19)(20)(21)(22), and the exertion of fluid flow is a likely mechanism by which HMP promotes such benefit (23)(24)(25). However, the optimal HMP environment, including the optimal degree of FSS for each structure within the kidney is yet to be defined by animal models or clinical trials.…”