[Immunosuppressive effect of mitomycin C-treated peripheral mononuclear blood cells (MICs) in vascularised composite allotransplantation]

Vascularized Composite Allotransplantation (VCA) enables the restoration of complex tissue defects. Since the first successful hand and face transplants were performed, clinical and experimental research has consistently improved immunosuppressive therapies. The incubation of peripheral blood mononuclear cells (PBMCs) with mitomycin C (MMC) results in immunomodulatory cells (MICs). In previous studies, the systemic application of MICs on the day of allogeneic hind limb transplantation led to a significant immunosuppression in rats. The aim of this study is to further investigate the optimal point in time of MIC application in a complex VCA model.

In six groups, 60 allogeneic hind limb transplantations were performed. Fully mismatched rats were used as hind limb donors [Lewis (LEW)] and recipients [Brown-Norway (BN)]. Group A received donor-derived MICs seven days preoperatively. Group B received no immunosuppression; group C received untreated PBMCs seven days prior to transplantation. Animals in group D received cell culture media, whereas group E was treated with a standard immunosuppression consisting of tacrolimus and prednisolone. In group F, syngeneic hind limb transplantations (BN→BN) were performed. Transplant rejection was assessed clinically and histologically.

Group A showed a significantly earlier onset of allograft rejection after 3.5 ± 0.2 days (p < 0.01) when compared with control groups B, C and D (5.5 ± 0.7, 5.3 ± 0.7 und 5.7 ± 0.5). Groups E and F showedno allograft rejection.

This study shows that the time of application determines the immunomodulatory effects of MICs. Whereas the systemic application of MICs on the day of transplantation led to a significant immunosuppression in previous studies, this study demonstrates that preoperative injections of MICs lead to an acceleration of allotransplant rejection. Follow-up studies are necessary to investigate further modifications of application time as well as dose-effect relations and cell characteristics of these potential immunosuppressive cells.