Developing normothermic machine liver perfusion for improvement of marginal donor graft quality

The studies incorporated in this thesis examined ways to develop ex situ normothermic machine perfusion (NMP) of the liver as a tool to enhance the reconditioning of high-risk extended criteria donor (ECD) organs. Two possible alternatives were investigated: (1) The use of hypothermic oxygenated machine perfusion as a therapeutic intervention preceding NMP; and (2) the delivery of a pharmacological combination of drugs targeting hepatic lipid metabolism during NMP. Using human donor livers discarded for transplantation, the feasibility of a combined protocol of hypothermic oxygenated perfusion (HOPE) and NMP was shown. HOPE optimised hepatic mitochondrial bioenergetic and oxidative status as well as mitigated ischaemia-reperfusion injury, while NMP maintained the organs' metabolism thus allowing the assessment of its metabolic functions. This combined protocol was facilitated with the use of a single acellular haemoglobin-based oxygen carrier (HBOC)-based perfusate throughout the entire perfusion, using a cold-to-warm machine perfusion protocol. These combined protocols enabled superior recovery of metabolic functions of ECD livers compared to NMP alone. The delivery of a combination of drugs targeting the hepatic lipid metabolism during NMP was also investigated. This approach reduced the intracellular lipid content of discarded human donor livers via enhancement of fatty-acids β-oxidation and solubilisation of lipids in the perfusate. The boosted lipid metabolism improved the metabolic status of the organs optimising their functional recovery and halted oxidative stress-related hepatobiliary injury. These findings are promising and guarantee future clinical investigation, opening a window of opportunity to improve the reconditioning of ECD livers.