Mandibular allotransplant procedures in dogs with the immunosuppressive agent FK506

Objective Treatment of mandibular lesions sometimes leads to the formation of large defects in the bone. Mandible reconstruction using grafted tissue, bone, and/or medical implants is required following the resection of such lesions. However, such grafts may not completely restore the continuity of the mandible. Facial transplantations using allografts are common, but mandibular allotransplantation has not been performed in humans, due to the unstable immune reaction of the complex tissue. In this study, mandibular transplantations performed under the effect of the immunosuppressive agent, FK506, were evaluated in dogs. Methods Mandibular allotransplantations were performed in 21 pairs of sex-blind beagle dogs. The left side of the mandible in the donor dog was transplanted to the left side of the mandible in the recipient dog. The FK506 doses were 0 mg for 3 dog pairs, 0.08 mg/kg/day for 3, 0.12 mg/kg/day for 5, 0.16 mg/kg/day for 5, and 0.32 mg/kg/day for 5 pairs. Twelve weeks after transplantation, the dogs were euthanized. Computed tomography (CT) and histological examinations of the transplanted sides were performed. Results Successful graft acceptance was dependent on immunosuppressive agent doses, and dogs administered more than 0.16 mg/kg/day FK506 showed 100 % survival. However, dogs administered 0.32 mg/kg/day FK506 showed significant weight loss 12 weeks after the surgery. CT findings showed thick mandibular cortical bone in the transplanted sites. Conclusions These results indicate that 0.16 mg/kg/day FK506 was the ideal dose for allotransplantations. Bone hyperplasia was observed in the transplanted sides, but it is not a disadvantage for allotransplantations.