Elderly Liver Grafts are More Susceptible to Ischemia‐Reperfusion After Prolonged Cold Ischemia than Grafts from Young Donors—An Ex Vivo Liver Machine Perfusion Analysis in <i>Sprague Dawley</i> Rats

ABSTRACT Organ shortage in liver transplantation results in increased use of extended criteria donors. This study investigates the effects of donor age and cold ischemia time (CIT) on liver graft quality in a rat normothermic machine perfusion (NMP) model. Livers from 3‐ and 12‐month‐old rats undergo 6 or 12 h of CIT followed by 6 h of NMP. Analyses include perfusate biochemistry, histology, and proteomics. Older donors with prolonged CIT show the highest perfusate alanine‐aminotransferase (highest median 751 U L −1 vs. lowest median 415 U L −1 , p = 0.06) and significantly elevated lactate dehydrogenase (8,659 U L −1 vs. 4,125 U L −1 , p = 0.005). Histological analysis reveals increasing tissue damage with advancing donor age and longer CIT. The older group also displays a lower perfusate‐to‐biliary glucose delta and a higher biliary glucose‐to‐perfusate ratio, indicating more severe bile duct injury. Proteomic profiling identifies differential expression of proteins involved in oxidative stress, apoptosis, cellular detoxification, antioxidant capacity, and fatty acid metabolism. Advanced donor age and prolonged CIT markedly impair liver graft quality, underscoring the need to minimize CIT. Advancing preservation strategies, refining viability criteria, and developing molecular interventions may improve graft viability and transplant success as donor demographics shift towards older populations.