Cyclosporine and skin allografts for the treatment of thermal injury. I. Extensive graft survival with low-level long-term administration and prolongation in a rat burn model.

The hypothesis tested in the present and accompanying study is that an effective treatment for severe burns involves early excision of necrotic tissue followed by skin allografting and cyclosporine (CsA) immunosuppressive therapy. LEW (RT1) rats served as recipients of thermal injury and/or skin allografts. BN x LEW F1 (LBN, RT1(l+n)) rats served as skin donors. LEW burn recipients received a hot water (90 degrees C for 10 sec) 30% body surface area (BSA) full-thickness burn. As expected, LEW recipients treated with CsA (25 mg/kg/day for 20 days) demonstrated significant graft prolongation compared with controls (P less than 0.005). Skin graft survival was similarly prolonged in LEW recipients undergoing burn injury, primary wound excision, and CsA administration compared with burn-skin allograft controls (P less than 0.001). Mortality was not increased in the thermal injury-CsA-treated recipients compared with burn controls. A final experiment was initiated to investigate how low-level long-term (greater than 100 days) maintenance CsA treatment influenced skin allograft survival for possible future consideration in burn trauma. Recipients receiving skin allografts plus CsA (20 days, 8mg/kg/day, followed by every other day thereafter) did not reject their grafts. However, a possible early sign of rejection (a single small ulcerative lesion) was noted in five of these long-term CsA-treated animals at a mean of 34 +/- 11 (SD) days. The lesion in these animals did not progress any further during CsA administration. Histopathologic study of selected animals removed from the CsA maintenance regimen for greater than 50 days following long-term administration revealed a number of interesting chronic lesions similar to those previously reported in the skin component of composite tissue (limb) allografts following long-term low-level CsA intervention. In conclusion, CsA was very successful in preventing rejection of skin allografts in a rat burn model without apparent adverse effects.