Axon regeneration through blood vessel allografts after cyclosporine treatment.

The present study describes the usefulness of blood vessel allografts to repair gaps in rat peripheral nerve after immunosuppression with cyclosporine. Isogeneic strains of rats with known histoincompatibility were used for this study. A 10-mm gap was created in the peroneal nerve of host Fischer rats. The gap was bridged by a 12-mm section of internal carotid artery removed from a Buffalo strain of rat. The host rats were divided into two groups. One group received no immunosuppression, whereas the other group was treated with cyclosporine. Untreated control rats immunologically rejected the allografted vessels and were unable to support host axonal regeneration through them. On the other hand, in cyclosporine-treated rats the allografted vessels survived. The regenerating host axons reorganized to form a functional nerve within the vessel conduit. The regenerated axons persisted even after rejection of the allografted vessel caused by cessation of immunotherapy. These results show that blood vessel allografts can serve as an effective conduit for reorganization of regenerated nerves and can bridge gaps in peripheral nerves.