Role of pulsatility in hypothermic reconditioning of porcine kidney grafts by machine perfusion after cold storage.

BACKGROUND: Brief in-house machine perfusion after cold storage (CS) (hypothermic reconditioning) has been proposed as a convenient tool to improve kidney graft function. The present study aimed to investigate the mechanistic role of vascular pulsatility in this context. METHODS: Kidney function after cold preservation (4°C, 18 hr) and subsequent reconditioning by 90 min of pulsatile machine perfusion (PP) (30/20 mm Hg) or nonpulsatile machine perfusion (NPP) (30 mm Hg) was studied in an isolated kidney perfusion model in pigs (n=6 for both) and compared with simply CS grafts. RESULTS: Compared with CS, PP but not NPP significantly improved renal perfusate flow and urine production and significantly increased the reduction of perfusate levels of creatinine and urea during reperfusion. Perfusate levels of fatty acid binding protein, a marker of tubular cell injury, were dramatically reduced by PP but not NPP. PP and NPP lowered fractional excretion of sodium, but significance was only reached for PP. Molecular effects of PP comprised a significant (vs. CS) mRNA elevation of the endothelial anti-inflammatory transcription factor Krüppel-like factor 2 as well as endothelial nitric oxide synthase, along with significantly higher perfusate levels of the endogenous vasodilator nitric oxide. Functional efficiency of PP over CS was confirmed in additional porcine transplant experiments (n=5 for both) by, for example, up to threefold improved clearance of creatinine during the first days after transplantation. CONCLUSION: PP of 90 min shortly before transplantation seems to be an efficient mechanism to reduce proinflammatory endothelial phenotype and improve functional outcome of kidney grafts even after preceding static storage.