| Sumario: | Normothermic machine perfusion (NMP) is an increasingly adopted preservation strategy in liver transplantation that facilitates organ assessment, safely prolongs preservation and is associated with reduced ischaemia reperfusion injury (IRI) related complications. However, these IRI-related benefits are less apparent in higher risk organs, which maintain a propensity to develop severe preservation injury despite NMP. The underlying mechanisms and contributory factors associated with this persistent injury are unclear, but may be related to molecular processes occurring during NMP or other preservation factors such as the length of cold ischaemia prior to NMP. This thesis aims to characterise the immunological and molecular processes occurring during NMP and devise interventions targeting these processes to reduce preservation injury. Through an evaluation of samples from clinical trials of human liver perfusion, I have demonstrated that ex situ reperfusion injury/inflammation (ERI) is an immunologically and molecularly distinct entity observed consistently across livers preserved with NMP. I have shown that the presence and length of prior static cold storage (pSCS) can impact the molecular signature of donor livers affecting key pathways and processes involved in mitochondrial function and cellular energetics. I have found that circulating damage associated molecular patterns (DAMPs), constitute an important element in ERI and alongside immune cells and inflammatory cytokines within the perfusate, propagate injury and inflammation ex situ, likely impacting the immunogenicity of the graft. I developed a large animal model to investigate these observations and explore possible modulatory interventions. Finally, I demonstrated that by mitigating ERI, ex situ graft function could be improved and preservation injury reduced in a porcine NMP model. This is achieved by the removal of highly pro-inflammatory nuclear DAMPs (neutrophil extracellular traps (NETs)/nucleosomes, free histones and cell free DNA) from the circulating perfusate during NMP with a specialised column.
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