Hypothermic oxygenated and normothermic machine perfusion mitigate innate systemic and hepatic inflammation after liver transplantation.

Abstract

Background: Immune-mediated injury drives ischaemia-reperfusion injury (IRI) following liver transplantation. While hypothermic oxygenated (HOPE) and normothermic machine perfusion (NMP) improve clinical outcomes, their immunological effects in humans remain unclear.

Objective: To examine hepatic and systemic immune responses across preservation strategies in a randomised controlled clinical setting.

Design: In this mechanistic substudy of the HOPE-NMP randomised controlled trial (NCT04644744), we analysed immune responses in n=47 recipients of extended criteria donor livers from brain-dead donors randomised to static cold storage (SCS), end-ischaemic HOPE or end-ischaemic NMP. Liver biopsies were obtained at organ arrival and early IRI. Blood samples were collected preoperatively, during reperfusion and on postoperative days 1, 2, 3 and 7.

Methods: Analyses included spectral flow cytometry, multiplex immunofluorescence with spatial analyses, cytokine profiling, cellular bioenergetics and mass spectrometry.

Results: In human liver allografts, both HOPE and NMP reduced neutrophil infiltration during early IRI, without altering intrahepatic spatial distribution. Machine perfusion induced phenotypic modulation of graft-infiltrating myeloid cells, characterised by downregulation of pro-inflammatory and adhesion markers. Peripheral lymphocyte numbers, particularly of NK cells and T cells, normalised faster after HOPE, compared with SCS and NMP groups, correlating with reduced liver injury. Absolute and relative systemic neutrophil numbers were lower in HOPE-recipients. Machine perfusion decreased the inflammatory activation of circulating myeloid and innate lymphoid cells, while inhibitory immune checkpoints were upregulated postoperatively.

Conclusions: In a randomised controlled trial using human samples, HOPE and NMP differentially modulate hepatic and systemic immune responses, attenuating neutrophil-driven inflammation and promoting immune regulation after liver transplantation.