[A histo-morphometric study on peripheral nerve allografts in rats with cyclosporin A]

This investigation evaluates regeneration across peripheral nerve allografts in minor mismatch rats immunosuppressed with Cyclosporin A (CSA). Lewis(RT1(1)) rats were recipients of 20 mm sciatic nerve grafts from allogenic Fischer (RT1(1)) donors. The recipients were randomly allocated to CSA immunosuppressed or untreated groups. CSA was administered at a daily dose of 5 mg/kg by subcutaneous injection for 8 weeks. Two animals from each group were sacrificed at 2, 4, 6, 8 and 12 weeks after the operation, and bilateral sciatic nerves were resected. Until the 8th week, the CSA-treated group showed good vascularization and minimal scar formation. The regeneration was faster and better in the CSA-treated group than in the untreated group. At the 12th week, however, the CSA-treated group showed scarring in the grafted nerves and Wallerian degeneration in the distal nerves, whereas the untreated group showed increased vascularization and myelinated fibers. The results have demonstrated that CSA greatly facilitates the regeneration process across the nerve allograft whereas the discontinuation of CSA leads to reduction of the regenerated nerve fibers. These findings would indicate that the use of CSA is imperatively needed even in minor mismatch cases.