Viability of discarded human livers during normothermic machine perfusion is associated with activation of repair mechanisms

Background and Aims: Liver transplantation provides an effective cure for end-stage liver disease but is hampered by a severe organ shortage. Normothermic machine perfusion (NMP) of donor livers allows dynamic preservation in addition to viability assessment prior to transplantation. Little is known about the injury and repair mechanisms induced during NMP. Therefore, we examined gene and protein expression changes in a cohort of discarded human livers during NMP, stratified by liver viability. Approach and Results: 6 human livers from donation after circulatory death (DCD) underwent 12 hours of NMP, of which 3 met viability criteria. We applied bulk transcriptomics to evaluate differences in gene expression relating to injury, repair, and regenerative responses among livers based on viability. Viable livers demonstrated robust activation of innate immunity after 3 hours of NMP followed by enrichment of pro-repair and pro-survival mechanisms. Nonviable livers demonstrated delayed and persistent enrichment of innate immune responses. Viable livers demonstrated effective induction of autophagy, the cellular repair and homeostasis pathway, compared to nonviable livers. Enrichment of pro-survival signaling was also broader in these livers. Conclusions: NMP of discarded DCD human livers results in ischemia-reperfusion injury, but importantly activates autophagy as a means of cellular repair. More pronounced activation of autophagy was seen in livers that met viability criteria for transplantation. Therapeutic targeting of the autophagy mechanism may allow rehabilitation of nonviable livers for transplantation. Human liver mRNA profils of fatty and lean liver samples subjected to 0, 3 or 6 hours of normothermic machine reperfusion