Mitochondrial Therapy During Machine Perfusion Restores the Function of DCD Livers: A Cross-Circulation Evaluation for Transplant Suitability

Donation after circulatory death (DCD) has significantly increased the number of organs potentially available for transplantation. Livers are more vulnerable than most other solid organs to warm ischemia in the DCD process. The injury induced by warm ischemic time (WIT) is further exacerbated during cold ischemia and reperfusion, resulting in tissue damage caused by the production of reactive oxygen species. These are not only cytotoxic but also perpetuate mitochondrial dysfunction and cell death. To improve the utilization of livers from uncontrolled DCD (uDCD) or controlled DCD (cDCD) donors with prolonged WIT, new strategies to mitigate WIT must be developed.Ex vivo normothermic machine perfusion (NMP) has increased DCD organ utilization and improved the assessment of the viability of organs before transplantation. NMP could also serve as a platform for isolated treatment of organs prior to transplant. An innovative approach to mitigate organ injury is to treat damaged livers with mitochondrial transplantation (MTx). In this study, we tested the efficacy of xenogeneic mitochondrial administration to restore the function of porcine DCD livers with two hours of warm ischemia. DCD livers were explanted and connected to NMP, where mitochondrial transplantation was administered as a bolus dose in the portal vein and hepatic artery at the start of perfusion. After four hours of NMP, treated livers demonstrated a significant increase in bile production, improved bile quality, and restored cytoarchitecture.To further assess the transplantation suitability of these livers post-NMP, they were connected to cross-circulation (CC) with a recipient pig. After six hours of CC, untreated livers became oedematous, exhibited significant aspartate aminotransferase elevations in the bile, and showed cellular degeneration, including near-complete loss of Kupffer cells. In contrast, livers treated with MTx maintained function across CC and were comparable to healthy controls. These data validate the efficacy of MTx in restoring function in DCD livers exposed to prolonged ischaemic times, presenting a promising approach to expand the donor pool.