The Distinct Innate Immune Response of Warm Ischemic Injured Livers during Continuous Normothermic Machine Perfusion

Abstract

Although normothermic machine perfusion (NMP) provides superior preservation of liver grafts compared to static cold storage and allows for viability testing of high-risk grafts, its effect on the liver immune compartment remains unclear. We investigated the innate immune response during 6 h of continuous NMP (cNMP) of livers that were directly procured (DP, n = 5) or procured after 60 min warm ischemia (WI, n = 5), followed by 12 h of whole blood (WB) reperfusion. WI livers showed elevated transaminase levels during cNMP but not after WB reperfusion. Perfusate concentrations of TNF-α were lower in WI livers during cNMP and WB reperfusion, whereas IL-8 concentrations did not differ significantly. TGF-β concentrations were higher in WI livers during NMP but not after WB reperfusion, whereas IL-10 concentrations were similar. Endoplasmic stress and apoptotic signaling were increased in WI livers during cNMP but not after WB reperfusion. Additionally, neutrophil mobilization increased to a significantly lesser extent in WI livers at the end of NMP. In conclusion, WI livers exhibit a distinct innate immune response during cNMP compared to DP livers. The cytokine profile shifted towards an anti-inflammatory phenotype during cNMP and WB reperfusion, and pro-apoptotic signaling was stronger during cNMP. During WB reperfusion, livers exhibited a blunted cytokine release, regardless of ischemic damage, supporting the potential reconditioning effect of cNMP.

The dynamics of cytokine release during 24 hours continuous normothermic machine perfusion liver preservation: An explorative porcine study

“…17 Our findings indicate that continuous NMP liver preservation modulates cytokine release and shifts the balance toward anti-inflammatory signaling during perfusion. 18 Therefore, we argue that cytokine absorption may be unnecessary and potentially counterproductive in this specific application of NMP. In contrast, higher cytokine concentrations were observed during end-ischemic NMP in donation after circulatory death livers and grafts that did not meet pre-specified viability criteria.…”

“…All livers were preserved with continuous NMP for 6 h and then subjected to reperfusion with WB-NMP to simulate transplantation. 18 The concentration of cytokines in the perfusate was measured during both the NMP and WB-NMP reperfusion phases and compared between livers that suffered warm ischemic injury and non-ischemic controls. Compared to controls, the overall release of pro-inflammatory cytokines during NMP was significantly lower in the group with 60 min of warm ischemia.…”

“…This difference remained significant even during the subsequent WB-NMP reperfusion phase. 18 Therefore, continuous NMP modulates the inflammatory response "on pump" even with clinically relevant pre-existing ischemic injury and this protective effect may last until the early post-reperfusion period. In contrast, in the studies on end-ischemic NMP by Hautz et al 15 and Mathis et al, 17 the perfusate concentration of pro-inflammatory cytokines, IL-6 in particular, was significantly higher during perfusion of donation after circulatory death compared to donation after brain death livers.…”

“…Indeed, NMP remained associated with a shift toward antiinflammatory signaling, which was more pronounced in warm ischemic injured livers compared to controls during both NMP and the subsequent WB-NMP reperfusion. 18 Inflammation is crucial for tissue regeneration, 20 with cytokine like TGFbeta playing pivotal roles. 21 The "excess" of TGFbeta relative to other pro-inflammatory cytokines observed during continuous NMP also in warm ischemic injured livers 18 may be linked to the activation of regenerative pathways and the reduction of cytokine-producing hepatic monocytes observed by Jassem et al at the end of human liver continuous NMP.…”