Normothermic human kidney preservation drives iron accumulation and ferroptosis

Ex vivo normothermic machine perfusion has been proposed to protect deceased donor organs, promoting metabolic recovery and allowing quality assessment. However, its benefits for preserving deceased donor kidneys remain ambiguous. We postulate that the use of red blood cells (RBCs) as oxygen carriers and associated secondary hemolysis may in fact cause renal injury, offsetting potential advantages. During 48-hour normothermic perfusion of seven human deceased donor kidneys, we observed progressive hemolysis, leading to iron accumulation in perfusate, tissue, and urine. Untargeted lipidomic analysis revealed profound increases in oxidized phospholipid species in perfused kidneys, pointing towards iron-dependent cell death known as ferroptosis. Next, in twelve additional human kidney perfusions, we demonstrate that either dialysis-based free hemoglobin removal or cell-free perfusion attenuates hemolysis-driven iron accumulation, phospholipid peroxidation, and acute kidney injury. Our findings highlight the pathological role of hemolysis and iron on the kidney, urging restraint in the clinical application of RBC-based kidney perfusion.