| Objective: Acute-injured peripheral nerves could be often seen in clinical studies. The repair and regeneration of acute-injured peripheral nerves have been perfect improving in last decades, including the using of microsurgical technique, tissue engineering technique, gene therapy, et al. However, the functional recovery of the nerves is unsatisfactory up to the present. In resent years the research is focused on the protecting of the injured nerves and accelerating regeneration. Along with the development of convalescence medicine, many studies about treating peripheral nerve diseases with physical factors have been attracted attentions of many clinical workers. The reports showed that decimeter wave could improve local blood circulation of the repairing site, alleviate hypoxia of regenerating nerves and increase the expression of immunologic reaction to S-100 protein in Schwann cell. It is also found that decimeter wave could accelerate the process of the repairing and regeneration of the peripheral nerve entrapment. In order to investigate the mechanism of decimeter wave effects on promoting the regeneration of peripheral nerves, we designed the model of acute-injured peripheral nerves of SD rats and studied the injured nerves histologically and functionally at different times after treatment.Methods: 80 Sprague-Dawley (SD) rats (200-250g) were randomly divided into 2 groups: group A, the decimeter wave treated group and group B, the operative control group. The right sciatic nerves of 80 SD rats were crushed with forceps to form the experimental animal model of peripheral acute-injured nerves. Then the rats of group A were fixed on a table prostrated and the right posterior thighs were exposed to decimeter wave every day from 1 day after operation to the sacrifice day. The rats of group B were also fixed on a table prostrated at same time, but were not exposed to decimeter wave. At the 1st, 2nd, 4thand 8th week postoperation, the samples were observed by anatomical, light and electron microscope observation, morphometric analysis and S-100 protein immunochemical staining. At the 8th week postoperation, electrophysiological assessment was conducted to measure the latency, nerve conduction velocity and amplitude of compound muscle action potentials. At the 1st, 2nd, 4thand 8th week postoperation, the MFS index was analyzed. At the 10th day before operation and at different times after operation, the SFI index was analyzed. All dates were analyzed statistically.Results: 1 The anatomical and light microscope observation: At the 1st week postoperation, the area of nerves where were crushed with forceps became very thin. The nerves of group B were more congestive and edematous than that of group A. Only a few of axons were observed continuously. Some regenerating blood vessels could be seen. The shape of myelin sheath was edematous in group B. A lot of inflammatory infiltration and tissue fragments were observed. At the 2nd week postoperation, the nerves of group A were less congestive and edematous than that of group B. The nerves became thicker, more slick and regular in group A. At the 4th week postoperation, the tissue around nerves in both groups was less congestive and edematous. There was less inflammatory infiltration in group A than that in group B. The epineurium of group A was pink and less congestive. The nerves of group B were stiff and less flexible. At the 8th week postoperation, the adhesion around nerves was much looser and had more regular distribution in group A than that in group B. There were many regenerating axons and blood vessels in group A. There was still a little inflammatory infiltration in the nerves of group B. The repristination of nerves in group A was better than that in group B. 2 The electron microscope observation: At the 2nd week postoperation, the tissue structure was disordered and the shape of myelin sheath was irregular. The ply structure could not be seen clearly. The nerves of group B were metamorphic evidently. Some segment of myelin sheath was curving and cuppy. At the 4th week postoperation, the myelin sheath was less edematous in group A than that in group B, and the regenerating axonal sprouts contained mitochondria, vesicles, neurolilaments and neurotubles were increasing. The organelle was less in axon in group B. At the 8th week postoperation, the fibers of nerves in group A were regular. The shape of myelin sheath became thicker and slicker, and the axonal diameter became bigger. The shape of organelle was regular. In group B, the thickness of myelin sheath was thin and the organelle in axon was immature. 3 The immunohistochemical staining: At different points postoperation, the S-100 protein in Schwann cells at the injured nerve in group A was more than that in group B. 4 The morphometric analysis: Distal nerve segments in group A had more myelinated axons counts, large mean axon diameters and mean myelin sheath thickness compared with those of group B (P<0.01). 5 The electrophysiological assessment: The parameters (latency, nerve conduction velocity and amplitude of compound muscle action potentials) revealed a better trend in group A compared with that in group B (P<0.05). 6 The motor function scale(MFS): In group A the time of MFS reached 2 point and 1 point was shorter than that in group B (P<0.01). 7 The analysis of SFI: The SFI recovery rate in group A was significantly higher than that in group B (P<0.01).Conclusions: Decimeter wave had obvious effects on the regeneration and functional recovery of the acute-injured peripheral nerves. The mechanism included: 1 Decimeter wave could restrain the inflammation, alleviate the congestion and relieve the adhesion of the acute-injured nerves, thereby decrease formation of new entrapment after injury. 2 Decimeter wave could restrain the hyperplasia of connective tissue and decrease the cicatrization in the regenerating area of the nerves. These were propitious to the inosculation of the fibers of the injured nerves. 3 Decimeter wave could promote the proliferation of Schwann cells and the expression of S-100 protein. It could also enhance axons growth and myelinization of the acute-injured nerves. 4 Decimeter wave could improve the local blood circulation of the acute-injured nerves in order to increasing the inflow and outflow of nutrition and accelerating the metabolism.
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