Damage-Associated Molecular Patterns Induce Inflammatory Injury During Machine Preservation of the Liver: Potential Targets to Enhance a Promising Technology

Abstract

Machine preservation (MP) has emerged as a promising technology in liver transplantation, but the cellular processes occurring during MP have not been characterized. Recent studies have noted the presence of inflammatory molecules generated during MP. We hypothesized that there is a metabolism-dependent accumulation of damage-associated molecular patterns (DAMPs) and inflammatory cytokines during MP and that these molecules provoke inflammation in the graft. To stratify groups by metabolic rate, MP was performed on rat livers from standard donors at 3 different temperatures: room temperature (RT), subnormothermic (30°C), and normothermic (37°C). Static cold storage at 4°C was included as a reference group. Following a 4-hour preservation period, graft reperfusion was performed ex vivo at 37°C (n = 6 for all groups). Levels of DAMPs and inflammatory cytokines were measured, and their biological activity was assessed by determining toll-like receptor (TLR) stimulation, inflammatory gene expression, and activation of cell death pathways. There was a time-dependent increase in levels of DAMPs during MP with high-mobility group box 1 and extracellular DNA levels increasing for all groups (P < 0.05, 30 versus 240 minutes). Tumor necrosis factor α levels in the perfusate also increased during MP for all groups (P < 0.05, 30 minutes versus 240 minutes). Levels of inflammatory molecules correlated with increased activation of TLRs (TLR3, P = 0.02, normothermic machine preservation [MP37] versus machine preservation at room temperature [MPRT]; TLR9, P = 0.02, MP37 versus MPRT). Priming of the NLRP3 inflammasome and activation of cell death pathways were reduced in grafts preserved by MP at room temperature. In conclusion, inflammatory molecules produced during MP have a biological impact on the graft. Therapies to attenuate DAMP-mediated inflammation during MP may further enhance this promising technology.