Infusion of third-party mesenchymal stem cells after liver transplantation: a phase-1, open-label, clinical study

Background: Mesenchymal stromal cells (MSC) are multipotent bone mar- row progenitors that have demonstrated significant immunosuppressive effects in various in vivo and in vitro studies. This study aimed to be the first evaluation of the safety and tolerability of MSC infusion after liver transplantation in a prospective, controlled phase-1 study. Methods: 10 liver transplant recipients under standard immunosuppression (TAC-MMF-low dose steroids until day 30) received 1.5–3 9 106/kg third party MSC on post-operative day 3 ` 2. These patients were prospectively compared to a group of 10 control liver recipients. Primary endpoints were MSC infusion toxicity, and incidence of cancer and opportunistic infections at month 6. Secondary endpoints were patient and graft survivals and rejection at month 6, as well as the effects of MSC on recipients’ immune function and on immunohistology of at month 6 graft biopsies. Results: No MSC infusional toxicity was observed. Both groups were comparable in terms of donor and recipient characteristics. There was no difference in primary end-points between control and MSC groups. No patient developed de novo cancer. There was no statistical difference in patient and graft survivals or in rejection rates. There was no graft rejection in the MSC group. Month-6 graft biopsies were not different according to Banff and fibrosis scores. Discussion: This phase 1 study showed excellent tolerability and safety of a single infusion of third-party MSC after liver transplantation. There were no graft safety issues and no excess of immunosuppression after MSC injection. Further analyses of consequences of MSC injection on the immune profile are needed. The possibility of avoiding calcineurin-inhibitors with repeated MSC injections as main immunosuppressive therapy and/of tolerance induction by MSC infusion should be investigated by further studies. This study is in part supported by an ESOT Senior Clinical Research Grant and by the University of Liege