The Experimental Study On The Artificial Nerve Tissue Graft Repaired Rat Sciatic Nerve Defect Of 3 And 6 Months

Objective: This study aimed to investigate whether or not the long-term denervated peripheral nerve could be repaired by artificial nerve graft.Methods: Left sciatic nerve was transected and a 4 mm segment removed, and long term (3 and 6 months) defects (10 mm ) of peripheral nerve were prepared. Then the female SD rats were randomly divided into three groups: artificial nerve graft (ANG) group (n=10), nerve autograft (NA) group (n=6, as positive control) and non-grafted (NG) group (n = 6, as negative control).The artificial nerve graft was used to bridge the 10-mm sciatic nerve gap. The gap was bridged with autologous nerve in NA group, but left unconnected in NG group.The artificial nerve graft was also used to bridge the fresh 10 mm nerve defect (n=8). Three months post-operatively (The postoperative time was prolonged to 6 months of another 10 rats of 3 months nerve defect), a combination of electrophysiological examination, Fluoro-Gold retrograde tracing, histological assessment including light microscopy and transmission electron microscopy, immunohistochemistry as well as morphometric analyses to both regenerated nerves and target muscles was utilized to investigate the nerve repair effects of our artificial nerve graft. Results: Reproducible compound muscle action potentials (CMAPs) were detected for the most of rats in ANG group and almost all in NA group, but none in NG group. The latency of CMAPs were longer in 6 months nerve defect ANG groups compared with those in 3 months(p<0.05). There was no significant difference between the two long term groups about amplitudes and motor nerve conduction velocities of CMAPs though the values of the two items were higher in 3 months long term group. The regenerated nerve fibes were found in the two long term groups at the sites of 5 mm distal to the distal coaptation and the middle portion of the artificial nerve graft. But in 3 months longterm group, the density of myelinated nerve fibers were larger, the number of neurons labelled by FG was higher too. Between the two long term group, there was no significant difference in the wet weight ratio of (operated side/ body weight) . The cross-sectional areas of muscle fibres were smaller in 6 months long term group (P<0.05), but the ratio of the hyperplastic collagen fiber was higher (P<0.05). The variation about motor plate was as atrophia as gastrocnemius muscle.The quantity and quality of regenerated nerve were better in two NA groups when compared with their corresponding experiment groups. But the muscle reinnervational outcome is as poor as the long term group. However, regeneration of nerve and the reinnervation of target organ all got predominant performance in fresh injury group. When the postoperative time after repair pronlonged to 6 months, better performance was observed, but no significant difference.Conclusion: Artificial nerve graft can sustain axonal regeneration from prolonged axotomized proximal stump of sciatic nerve to chronically denervated stump to some extent. But the capacity of nerve regeneration decreased following prolonged axotomy and denervation. And it seems that better outcomes of nerve regeneration may be obtained when the postoperative time after repair was pronlonged.