Red blood cells as oxygen carrier during normothermic machine perfusion of kidney grafts: friend or foe?

Renal ex-vivo normothermic machine perfusion (NMP) is under development as an assessment tool for high-risk kidney grafts, and as a means of achieving more physiologically accurate organ preservation. On-going hemolysis has been reported during NMP, as this technique relies on red blood cells (RBCs) for oxygen delivery. In this study we confirm the occurrence of progressive hemolysis during 6-hour kidney NMP. NMP-associated erythrostasis in the glomeruli and in peri-glomerular vascular networks point to an interaction between the RBCs and the graft. Continuous hemolysis resulted in pro-oxidative changes in the perfusate, which could be quenched by addition of fresh frozen plasma. In a cell based system, this hemolysis induced redox stress and exhibited toxic effects at high concentrations. These findings highlight the need for a more refined oxygen carrier in the context of renal NMP.