Hemodiafiltration improves performance of 24 hour ex situ normothermic liver machine perfusion

Performing ex situ normothermic machine perfusion (NMP) for ≥24 h represents an opportunity to evaluate and treat livers, but is limited by the lack of support from relevant extrahepatic organs. Incorporation of systems of renal replacement therapy, including hemodiafiltration (HDF), appears useful in this regard during prolonged ex situ liver NMP. This study aimed to demonstrate the impact and benefits associated with incorporation of continuous HDF during 24-h ex situ NMP in a relevant preclinical model, including transplantation and post-transplant follow-up.

Porcine livers (n = 28) underwent 24-h ex situ NMP with either partial perfusate exchange at 12 h and no HDF (NHDF, n = 11) or HDF initiated 2 h after NMP start (n = 17). Biochemical, histological, endothelial, and metabolomic parameters were assessed. A subset of grafts undergoing NMP + HDF (n = 8) were transplanted into recipients.

Incorporation of HDF during NMP maintained stable pH and electrolyte levels, effectively preventing hypernatremia, hypochloremia, and hypocalcemia developing without HDF. HDF cleared metabolic wastes (e.g. urea) and inflammatory cytokines (IL-1B, IL-2, IL-6, IL-8, and IL-18), resulting in reduced injury and oxidative stress markers after 24 h (Suzuki score 0.8 ± 0.4 HDF vs. 2.7 ± 1.3 NHDF, p <0.001). Vasoprotective endothelial response mechanisms, including KLF2 and eNOS gene and protein expression, were upregulated, whereas stellate cell activation and sinusoidal contraction were reduced among HDF-treated grafts. HDF reduced metabolomic alterations arising in livers during 24-h NMP, and adequate graft maintenance using NMP + HDF was demonstrated by full functional and metabolic recovery during post-transplant follow-up.

Continuous HDF promotes a more physiological biochemical and metabolic environment, reduces inflammation and oxidative stress, and preserves homeostatic endothelial response mechanisms in livers undergoing 24-h ex situ NMP, facilitating successful transplantation in a complex preclinical model.

In this preclinical study, livers were normothermically perfused for 24 h ex situ, both with and without continuous HDF. Incorporation of HDF offered relevant improvements in numerous on-device measures, including the maintenance of physiological biochemical parameters; removal of injurious metabolic wastes; and improvement of injury and stress responses in parenchymal and nonparenchymal cells. A subset of livers were successfully transplanted and demonstrated full functional and metabolic recovery during follow-up. These findings indicate that advanced renal replacement therapies, such as HDF, are a key aspect of improving and prolonging ex situ normothermic liver perfusion, although there is ongoing need to develop more physiological metabolic support protocols for livers while on such devices.