Impact of Donor Age and Prolonged Warm Ischemia in Normothermic Machine Perfusion of Rat Livers

Expanding the liver donor pool increasingly depends on extended criteria donors (ECD), including older individuals and those after circulatory death. However, ECD grafts are more susceptible to ischemia-reperfusion injury. Normothermic machine perfusion (NMP) offers a promising solution to preserve the metabolic activity of liver grafts and to assess the graft quality at the same time.

We used a standardized rat NMP model to examine the combined effects of donor age and donation after cardiac death on graft viability. Following circulatory arrest and 30 min of warm ischemia, livers from young (3-month-old) and older (12-month-old) Sprague-Dawley rats underwent either 3 or 6 h of NMP (n = 6/group). We assessed functional parameters during NMP, metabolic markers, histological injury, and performed proteomic analysis.

All grafts remained metabolically active, with lactate clearance and bile production observed across all groups. While older livers exhibited a more acidotic perfusate pH, younger livers showed significantly higher transaminase release. Histological analysis revealed significantly increased necrosis in older livers after prolonged perfusion. Proteomic profiling identified age- and perfusion time-dependent shifts in pathways related to mitochondrial damage, oxidative stress, and immune activation. Notably, these molecular signs of injury were not consistently reflected in conventional viability markers.

This study highlights how donor age and warm ischemia impact the quality of ECD liver grafts. Histological and molecular assessment during NMP may lead to tailored interventions to improve the quality of such grafts, which is not well reflected by conventional parameters. Our findings support the role of NMP in expanding the utilization of ECD grafts amid organ shortages and an aging donor population.