The effects of an autologous transplant on patterns of regeneration in rat sciatic nerve.

Autologous transplants are often used in repair of peripheral nerve injury. Quantitative evaluation of the results of such a transplant is obviously desirable. In previous study, we determined numerical and cytologic parameters of the regeneration that followed transection of rat sciatic nerve, but no transplant was used. This work now serves as a basis for evaluating the use of an autologous transplant in the same transection paradigm. Our procedure is to remove 8 mm of sciatic nerve in the thigh. The removed segment is then put into the center of a silicone tube and the proximal and distal stumps of the severed nerve are placed into the ends of the tube. The data show: (1) a high percentage of successful regenerations; (2) a relatively large nerve in the gap; (3) a typical outer perineurium underlying the epineurium; (4) a well-developed fascicular perineurium; and (5) approximately equal numbers of myelinated and unmyelinated axons in the gap and distal stump. If a transplant is not used there are: (1) a greater number of failures of regeneration; (2) a smaller nerve in the gap; (3) a less well-developed fascicular perineurium; (4) unequal numbers of axons in the gap as compared to the distal stump; and (5) no outer perineurium forms. The presence of a typical outer perineurium after a transplant and its absence if a transplant is not used is probably the most striking cytologic difference between the two paradigms. The equal numbers of axons in the gap and distal stump following regeneration after transplantation presumably indicate that all axons in the gap enter the distal stump without branching or ending blindly, a situation that is presumably beneficial and contrasts with the findings when a transplant is not used. Both paradigms show a remarkable increase in the density of blood vessels in the regenerated nerve in the gap between the two stumps. These findings will serve as a basis for further studies on the mechanisms of peripheral nerve regeneration.