Heme Oxygenase-1-Modified Bone Marrow Mesenchymal Stem Cells Perfusion Using a Normothermic Machine Perfusion System Reduces the Acute Rejection of Liver Transplantation by Regulating Natural Killer T Cell Co-Inhibitory Receptors

Background: Acute rejection (ACR) remains an important risk factor affecting the survival of recipients following liver transplantation (LT). Immunosuppressive agents are associated with many 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 systemic BMMSCs application. Methods: BMMSCs were isolated from rat bone marrow and modified with the adenovirus for 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 and Gene chip technology was used to detect differential gene expression, then the flow cytometry was used to analyze changes in natural killer (NK) T cells. Findings: NMP can induce BMMSCs to colonize the donor liver during in vitro preservation, and the survival of HO-1/BMMSCs in the liver after transplantation was significantly longer than that of BMMSCs. When the donor liver contained HO-1/BMMSCs, the ACR of LT is obviously controlled, and the survival time was significantly prolonged. Interpretation: The application of HO-1/BMMSCs reduces the number of NKT cells in the liver following transplantation, increases the expression of the NKT cell co-inhibitory receptors, BTLA and CD160, and reduces the level of NKT cell expression of IFN-γ. Thus, NK cell and CD8+ T cell activation was inhibited, which reduced the ACR. Funding Information: The work was supported by the National Natural Science Foundation of China (No. 82070639, 81670574, 81441022 and 81270528). Declaration of Interests: All of the authors declared no conflict of interest. Ethics Approval Statement: All animal protocols were based on the National Institutes of Health Guide for the Care and Use of Laboratory Animals (National Institutes of Health publication 85 - 23, Bethesda, MD). All procedures were approved by the Ethics Committee of Tianjin First Central Hospital (license number: 2016-03-A1).