HO-1/Bmmscs Perfusion Using a Normothermic Machine Perfusion System Reduces the Acute Rejection of DCD Liver Transplantation by Regulating NKT Cell Co-Inhibitory Receptors

Abstract Background: Liver transplantation (LT) represents the most effective treatment for many end-stage liver diseases. While donation after cardiac death (DCD) donor livers are used due to organ shortage, acute rejection (ACR) remains an important risk factor affecting the survival of recipients following transplantation. Although immunosuppressive agents can be used, they are associated with complications. Bone marrow mesenchymal stem cells (BMMSCs) are used in the treatment of organ transplantation; however, there is limited colonization in the target organs and a short survival time following BMMSCs application. Thus, an optimized BMMSCs application method is required to suppress immune rejection and promote the long-term survival of allogeneic liver transplant recipients. Methods: BMMSCs were isolated and modified with heme oxygenase 1 (HO-1) gene. HO-1/BMMSCs were perfused into the donor liver in vitro using a normothermic machine perfusion (NMP) system, followed by LT. The severity of ACR was evaluated based on the liver histopathology. Gene chip technology was used to detect differential gene expression, and the flow cytometry was used to analyze changes in natural killer (NK) T cells. Results: NMP can induce BMMSCs to colonize the donor liver during in vitro preservation, and the survival of HO-1/BMMSCs in the liver grafts was significantly longer than that of BMMSCs. When the donor liver contained HO-1/BMMSCs, the ACR is obviously controlled, and the survival time was significantly prolonged. The application of HO-1/BMMSCs reduces the number of NKT cells in the liver grafts, increases the expression of the NKT cell co-inhibitory receptors, and reduces the level of NKT cell expression of IFN-γ. Thus, NK cell and CD8+ T cell activation was inhibited, which reduced acute of rejection of the transplanted liver. Conclusions: The NMP system preserves the DCD donor liver in vitro, and also allows large quantities of BMMSCs to colonize the liver. HO-1-modified BMMSCs are able to improve and prolong the local immunosuppressive effect of BMMSCs following transplantation by reducing the number of NKT cells and up-regulating NKT cell co-inhibitory receptor expression. This results in the transmission of inhibitory signals to NKT cells, reduced NKT cell IFN-γ levels, and the inhibition of ACR.