Normothermic Machine Perfusion Preserves Endothelial Clearance, Modulates Inflammation After Prolonged Warm Ischemia in Liver Grafts

Background. Prolonged warm ischemia time (WIT) increases susceptibility to ischemia–reperfusion injury in liver grafts. Viability assessment during normothermic machine perfusion (NMP) mainly targets hepatocyte and cholangiocyte function, whereas the contribution of liver sinusoidal endothelial cells (LSECs) is less explored. We evaluated whether clearance of hyaluronan (HA) and N-terminal propeptide of procollagen type III (PIIINP) reflects LSEC clearance function and predicts inflammatory activation during NMP. Methods. In a porcine model with 45 min of WIT, livers were randomized to either immediate NMP for 12 h (n = 7), or 4 h of static cold storage followed by 8 h of NMP (SCS-NMP, n = 7). Perfusate HA and PIIINP were quantified as markers of LSEC function. Interstitial cytokines and metabolic profiles were assessed with microdialysis. Results. Immediate NMP resulted in significantly lower HA and PIIINP concentrations after 4 and 12 h, accompanied by increased expression of their clearance receptors, stabilin-1 and stabilin-2. Moreover, impaired HA clearance was associated with elevated levels of interleukin (IL)-1α, IL-1β, IL-6, and interferon-γ, whereas PIIINP correlated positively with granulocyte-macrophage colony-stimulating factor. Histology confirmed preserved sinusoidal structure with continuous Wheat Germ Agglutinin lectin labeling. The SCS-NMP group exhibited greater lactate/pyruvate ratios and glycerol levels, indicating greater metabolic stress and cellular injury. Conclusions. Immediate NMP after prolonged WIT preserves LSEC clearance, modulates inflammatory cytokine release, and enhances metabolic recovery compared with SCS-NMP. These findings highlight the overlooked role of LSECs during ex situ perfusion of ischemic grafts. This may have implications for graft assessment under conditions of prolonged warm ischemia.