BACKGROUND:To improve local microenvironment and reduce local scars is conducive to peripheral nerve regeneration that promotes nerve function recovery.OBJECTIVE:To evaluate the effect of fresh amniotic membrane on the regeneration of tinjured peripheral nerve.METHODS:Sixty healthy Sprague-Dawley rats were randomly divided into three groups (n=20 per group) after constructing a model of sciatic nerve injury of the unilateral leg. In group A, the nerve was wrapped with fresh human amnion at the anastomosis end after the repair of nerve. In group B, the nerve was wrapped with biofilm at the anastomosis end after the repair of nerve. In group C, no treatment was conducted after the repair of nerve (blank control). The effects were evaluated by anatomical observation, light microscope observation, immunohistochemical detection (2, 4, 8, 12 weeks after surgery), transmission electron microscope observation, axon imaging analysis, action potential detection, and sciatic nerve function index (4, 8, 12 weeks after surgery).RESULTS AND CONCLUSION: (1) Gross observation. The amniotic membrane and biofilm were absorbed partialy at postoperative 2 weeks, mostly at postoperative 4 weeks and completely at postoperative 8 weeks. In the groups A and B, the nerve was adhered slightly and loosely to the surrounding tissues, with a fair range of motion. In the group C, the nerve was tightly adhered to the surrounding tissues, with a poor range of motion. (2) Observation under light microscope. The nerve regeneration was better in the groups A and B than group C at 2, 4, 8, 12 weeks postoperatively. (3) Observation under electron microscope. Regenerated nerve fibers were rarely seen and lamelar structures were unclear in the three groups at 4 weeks postoperatively. Then, increased regenerated nerve fibers, thickened myelin sheath, clear lamelar structure and enlarged axon diameter were found in the groups A and B compared with the group C at 8 and 12 weeks postoperatively. (4) Immunohistochemical detection. The expression and distribution of S-100 protein in the groups A and B were better than those in the group C. (5) Axon image analysis. Groups A and B were superior to the group C in the diameter of myelinated nerve fibers, thickness of myelin sheath and number of regenerated nerve fibers. There was a significant difference by statistical analysis (P < 0.05). (6) Electrophysiological examination. Shorter latency period, higher amplitude and faster nerve conduction velocities were observed in the groups A and B compared with the group C (P < 0.05). (7) The sciatic function index. The sciatic function index in group A or B was significantly higher than that in group C (P < 0.05). To conclude, the human amniotic membrane can reduce adhesion between the damaged nerve and surrounding tissues, and prevent scarring at the anastomosis end. In addition, it promotes the regeneration of nerve fibers, increase axon diameter and myelin sheath thickness, and ease inflammatory and immune responses at the neural incision.