Muscle allograft survival after cyclosporin A immunosuppression

In normal rats, autografts of skeletal muscle survive, whereas allografts of muscle are immunologically rejected. In the present study we sought to determine whether or not the new immunosuppressive drug cyclosporin A (CyA) would prevent the rejection of muscle allografts. Autografts and allografts of rat extensor digitorum longus muscles were made into recipients that went untreated (i.e., no treatment or vehicle injected) or that received daily injections of CyA (5 mg/kg). Autografts of muscle survived throughout the 12-week period of study. On the other hand, untreated rats rejected muscle allografts within 2 weeks, whereas allografts in CyA-treated recipients survived, even at 12 weeks when the experiment was terminated. In another study, CyA therapy was discontinued after 4 weeks in rats that received bilateral muscle allografts, both of which had survived; one was removed at that time. The second muscle allograft from these rats was examined 2 months later, and all were found rejected. CyA was also effective in preventing the rejection of muscle allografts in rats that were previously sensitized to the same transplantation antigens present on the allogeneic muscle cells. These results demonstrated that CyA can prevent the rejection of muscle allografts but only if drug treatment is continued. We conclude that CyA is a potent immunosuppressive agent which could prove useful in clinical muscle allotransplantation or in experimental animal studies that require immunosuppression.