Histological evaluation of composit tissue allograft survival in a rat model with FK506 (Tacrolimus) and mycophenolate mofetil *
The goal of limb transplantation, which consists of composite tissue transplantation, is to attain good functional recovery without immunological responses. Many experimental studies have examined the immunosuppressive effects of FK506. However, few experimental reports on an immunosuppressive regimen consisting of FK506 and mycophenolate mofetil have been made. We performed a series of experimental studies on vascularized rat hind limb allografts with FK506 and mycophenolate mofetil. The purpose of this study was to investigate the immunosuppressive effects of a combined regimen using FK506 and mycophenolate mofetil on rejection responses to vascularized limb allografts in rats. Vascularized limb allografts were microscopically transplanted from ACI (RT-la) rats to Lewis (RT-ll) rats. An isografts without immunosuppression group and an allograft with FK506 and mycophenolate mofetil immunosuppression group were then compared. Gross findings for the transplanted limbs, and the histological findings of the transplanted limb component tissues were then evaluated at 30, 60, or 90 days after surgery. All the grafted limbs survived, and no signs of rejection were observed in the isografts. The transplanted limbs showed mild swelling and erythema, but no mummification occurred in the allografts during the evaluation periods. Histologically, no skin rejection occurred in the isografts, and no rejections of bone, cartilage, or muscle occured. In the allografts, however, the skin was moderately rejected, and bone, cartilage and muscle were minimally rejected. The rejection was graded as follows: skin, 0.6; muscle, 0.4; bone, 0.4; and cartilage, 0.3; the mean rejection grading score was 0.43 for the allografts. The rejection of the skin was severer than that of the other components. Further immunological and pharmacological investigations of immunosuppressants are needed prior to the clinical application of allogenic limb transplantation. (Accepted on August 8, 2011)
