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. Overall design: Human liver mRNA profils of fatty and lean liver samples subjected to 0, 3 or 6 hours of normothermic machine reperfusion

背景与研究目的：肝移植是终末期肝病的有效治愈手段，但面临严重的器官短缺问题。供体肝脏的常温机器灌注（Normothermic Machine Perfusion，NMP）可在移植前实现动态保存，并完成肝脏活力评估。目前对于常温机器灌注过程中诱导的损伤与修复机制仍知之甚少。因此，本研究针对一组废弃人肝，按肝脏活力分层，检测其在常温机器灌注过程中的基因与蛋白表达变化。
研究方法与结果：本研究纳入6例循环死亡后捐献（Donation After Circulatory Death，DCD）的肝脏，均接受12小时的常温机器灌注，其中3例符合移植活力标准。我们采用批量转录组学（bulk transcriptomics），基于肝脏活力评估不同组间与损伤、修复及再生反应相关的基因表达差异。结果显示，符合活力标准的肝脏在常温机器灌注3小时后即展现出先天免疫的强力激活，随后促修复与促存活通路发生富集；而非活力肝脏则出现先天免疫应答的延迟且持续富集。与非活力肝脏相比，活力肝脏可有效诱导自噬（autophagy）——这一细胞修复与稳态维持通路——的激活，且其促存活信号通路的富集范围也更为广泛。
研究结论：废弃DCD人肝的常温机器灌注会引发缺血再灌注损伤，但重要的是，其可通过激活自噬通路实现细胞修复。符合移植活力标准的肝脏中，自噬的激活程度更为显著。针对自噬机制进行靶向治疗，或可实现非活力肝脏的功能修复，使其可用于临床移植。
实验整体设计：本数据集涵盖经0、3或6小时常温机器再灌注的脂肪性与非脂肪性肝脏样本的人肝mRNA表达谱。