[Favorable effect of chitosan sustained-release FK506 incorporated conduits on axonal regeneration in rat sciatic nerve].

Objective: To investigate the efficacy of 3 mm gap bridging repairing neurotmesis with chitosan sustained-release FK506 incorporated conduits.

Methods: Forty-five adult male SD rats were divided randomly into 3 groups. The rats were received a neurotomy to bilateral sciatic nerve and subsequently reconnected with regeneration chambers. The bridging conduits of group A, B and C were made of silicon tube, chitosan and chitosan sustained-release FK506 incorporated respectively. Conduits absorption and surrounding tissue cicatrization were observed at 6, 8 and 12 weeks after neurotomy. The nerve regeneration and functional recovery were evaluated by electrophysiology, histological changes, morphometric analysis, and weighing of gastrocnemius muscles.

Results: The silicon tubes of group A adhered severely with surrounding tissue. Bridging grafts of group B and C adhered relatively slightly and could be stripped easily from surrounding tissue. The regeneration chambers still existed fully at 6 weeks and began to be degraded at 8 weeks after neurotomy. The bridging grafts of group B and C were disintegrated at 12 weeks and the continuity of sciatic nerve was established without obvious adhesion with surrounding tissue. The statistical evaluation for nerve regeneration demonstrated that rats of group C showed the best results. Although rats of group B and A were found to be the second and the third respectively, there is no significant difference between them.

Conclusion: Remaining 3 mm gap bridging repairing rat sciatic nerve with chitosan sustained-release FK506 incorporated conduits, which stabilize for more than 2 months before degradation in vivo, can significantly promote nerve regeneration and facilitate function recovery without adverse effects.