| The effect of the nerve reconstruction is affected seriously by the denerved skeletal muscle's atrophy. It is a tough problem to prevent the skeletal muscle's atrophy after the denervation for a long time such as the high level nerve injury. Recent years, the studies on this point revealed that the skeletal muscle's atrophy have relationship with some ingredients of peripheral nerve, especially the role of schwann cell. As a kind of peripheral neurilemma cell, the schwann cell is applied and studied extensively because of it's important role in the nerve regeneration after injury. At the same time, the schwann cell also is considered as a seed cell in the peripheral nerve tissue engineering. As for the study on the role of schwann cell in skeletal muscle and the endplate after nerve injury, there is a little. Based on the domestic and abroad works before, we concluded the changing regularity pattern of the distal schwann cell, skeletal muscle and the endplate after nerve injury and found that the proliferation regularity of schwann cell has consistency with the proliferation regularity of muscle satellite cell, the content of myogenin and the changing curve of nutrition factors such as BDNF and CNTF. The endplate and skeletal muscle always regenerated slowly in some time after nerve injury. The regularity was same to the time of wallerian degeneration and the proliferation of schwann cell. The apparent degeneration also took place when the schwann cell activity decreased, the Bunger band atrophied and the schwann cell disappeared. The terminal schwann cell covering the neuromuscular junction stretched out branches into the muscles and formed a complex network after nerve injury. This process would lasted about 8 weeks. When the nerve fiber ending regenerated and reached the endplate at this time, the schwann cell stopped to growth and atrophied gradually. Further more, the schwann cell secreted some factors correlated to the nutrition and regeneration of skeletal muscle after nerve injury. So we presumed that the proliferation of schwann cell may delayed the degeneration role of the skeletal muscle and endplate after nerve injury. In order to testify this presumption indirectly, we made the preliminary observation of the role of schwann cell to muscle satellite cell, skeletal muscle and endplate in denerved rats using the schwann cell of neonate rat cultured in vitro (mixed cultivation and united cultivation) and the cell transplantation inner skeletal muscle. In the first segment of our study, the peripheral nerve and the skeletal muscle of hind limb of SD rats with age of one week were resected. Through the cultured method in vitro, we got the highly purified schwann cell and the muscle satellite cell, then we cultured the different content schwann cell (2.5×104/ml,5×104/ml) with identical content muscle satellite cell(1×105/ml), observed the influence on the growth, proliferation and differentiation of the muscle skeletal cell. At the same time, the different content schwann cell (5×104/ml,1×105/ml)was co-cultured with identical content muscle satellite cell(1×105/ml) using the MCPW cell cultured system. Then the proliferated velocity and activity of muscle satellite cell weredetected by cell counting and flow cytometry. The two co-cultured methods were all contrasted to the single cultured method. In the second segment, after signaled the schwann cell of neonate rat with BrdU, we injected the schwann cell(200μl,1×106/ml) with microinjector into the right gastrocnemius of rat whose nerve was resected on the point of the nerve enter the muscle before. At the same time, we injected isodose DMEM culture solution without serum into gastrocnemius in control group. 1, 2, 4, 6 and 8 weeks later, the contractile ability of gastrocnemius was detected using living function experimental system. After that, we measured the relative humid weight, stained the muscle with HE stainning method, observed the pathological changes of muscle and the myocyte, calculated the section area of the skeletal muscle cell using image analysis system, analyzed the data and progressed statistical treatment. Further more, we used BrdU tracing method and immunohistochemistry staining method with S-100аprotein monoclonal antibody to display the condition of schwann cell's living, quantity and distribution in gastrocnemius, used the auric chloride staining method to display the terminal of nerve and the morphous of endplate. Also the ultrastructure of muscle satellite cell single cultured and mixed culture and gastrocnemius in control and experimental group was observed by scanning electron microscope and transmission electron microscope. The results reveal that: there was no reciprocal inhibition between the two kinds cells in mixed culture group. The compatibility was good. Some cell connected by synapse each other. The two kinds cells proliferated fast. In mixed culture group, the muscle skeletal cell proliferation and differentiation were active, the myotube formed earlier, bulkier and more than the control group, the myotube arranged in order, and contract powerfully, especiallywhen the schwann cell quantity was more. The ultrostructure of the muscle satellite cell also reveal that the cell mixed cultured had the characteristic of active proliferation and differentiation, such as the smaller bulky, the little surface projection, more cytolysosome lined close to cell membrane and conferted myofilament. In co-cultivation group, the muscle satellite cell proliferated faster than the single culture group, the SPF and PI value were higher than single culture group. The transplantation experiment reveal that the schwann cell of neonate rat can live in skeletal muscle. But the distribution was unevenness. The cell number increased after 4 weeks, some cells were encapsulated by inflammatory reaction. The hind limb lymph nodes were swelled in majority. Contrast to the control group, on the same time, the gastrocnemius tetanus intensity time and relative humid weight ratio in experimental group decreased little, the muscular atrophy lightened and the muscle fiber section area enlarged. There was significant difference on statistical analysis, especially from 2 to 4 weeks after operation. Under light microscope, the functional condition of myocyte was active, more nucleus ingression and collection. There were more disintegration phases. The myofilament arranged in order. The satellite cell was more. But the inflammatory reaction in experimental group was sever than the control group. The uric chloride staining revealed that the endplate became degenerated 2 weeks after nerve injury, the schwann cell filament extended on the surface of the muscle fiber, and the filament increased and connected each other in net shapes in experimental group. Contrasted to the control group, the myofibrillar atrophy and degeneration emerged earlier in experimental group, the schwann cell filament was longer and more intensive. Under the electronmicroscope, the mitochondrialcavitation was little, the myofilament and myocomma arranged in order, the muscle satellite was more and active in experimental group. We can conclude from this study that: the schwann cell cultured in vitro may accrete with the muscle satellite cell and can promote its proliferation and the differentiation obviously, the schwann cell also may improve the proliferated activity of the muscle satellite cell. The schwann cell transplanted in vivo not only can live, but can promote the muscle cell nuclear fission, elevate the proliferated activity, delay the muscle cell atrophy and the decrease of contractibility on some degree, protect the endplate degeneration. But the grafting cell may cause some immunity reaction. According to this study, the transplanted schwann cell may play the role to the denervated skeletal muscle and endplate on three aspects: the first, the schwann cell secrete some kinds of nutrition factors related to skeletal muscle, these factors can slow down the functional metabolic degeneration; the second, the schwann cell promote the proliferation and differentiation of the muscle satellite cell through direct contact or indirect secreted of various kinds of factors ways and facilitate the muscle cell regeneration; the third, the schwann cell and the proliferated terminal schwann cell may protect the endplate together, and provide a good circumstance for the regenerated nerve and reinnervation of the denervated skeletal muscle. Based on the lots of works of predecessor before, we concluded the changing regularity pattern of the schwann cell, the denervated skeletal muscle and endplate, made an audacious theoretical presumption. Through our study, we testified that the schwann cell cultured in vitro can promote the proliferation and differentiation of muscle satellite cell, provide the the...
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