Advancing perfusion models: Dual-vessel ex vivo rat liver perfusion based on a clinical setup

Normothermic ex vivo liver machine perfusion (NEVLP) has been developed to address the increasing organ shortage in liver transplantation, potentially through pharmacological conditioning of grafts originating from extended criteria donors. To establish new therapeutic concepts, simple and standardized animal models are needed, that simulate clinical NEVLP as closely as possible. Liver grafts from 36 Sprague-Dawley rats were perfused for 6 h in a dual-vessel NEVLP system using varying doses of the clinically used vasodilator epoprostenol, with and without the addition of the Kupffer cell inhibitor glycine. Cell culture medium supplemented with rat plasma and erythrocytes was compared to Steen-based perfusion solution, which is used in clinical NEVLP. Perfusion pressures and bile production were recorded, and perfusate was analyzed for transaminase secretion. Tissue samples were assessed histologically, and tissue levels of cytokines and 8-Isoprostane were measured. Increasing levels of epoprostenol and the addition of glycine resulted in a stepwise decrease of transaminase secretion and improved bile production. Steen significantly decreased transaminase release as well as IL-1β production. Liver grafts perfused with the optimised Steen-based protocol exhibited lowest levels of oxidative stress with best-preserved liver integrity. In conclusion, high doses of epoprostenol seem to ameliorate liver function and prevent cellular damage beyond the vasodilatory effect, with glycine acting synergistically. The anti-inflammatory and anti-oxidative properties of Steen further optimise perfusion conditions. Our rodent NEVLP system may be used to rapidly test new agents for pharmacologic conditioning of livers and to translate these findings from bench-to-bedside.