Research Of Transforming Growth Factor-β1 In Skeletal Muscle After A Downhill Running

ObjectiveSkeletal muscle has the remarkable ability to repair after injury. Skeletal muscle repair is a highly synchronized process involving the activation of various cellular responses. Activation of adult muscle satellite cells is a key element in this process.TGF-β1 has long been recognized as modulators of satellite cells activity, inhibiting both proliferation and differentiation, which play an important role in skeletal muscle injury and repair. This study induced the rats injured by using downhill running model, then investigated the change of muscle fiber from the histological level and the variance of TGF-β1 expression by the level of molecular biology.Methods72 8-week-SD healthy rats were divided into control group(C, n=8) and exercise group(E, n=64) which were then sub-divided into 0h,6h,12h,24h,48h,72h, 1w, and 2w group by avoirdupois (n=8). Exercise groups rats had to do downhill running of 90min,when the speed was 16m/min and grade was-16°. Then the rats were scarified respectively at once or at 6h,12h,24h,48h,72h, 1w, and 2w later, and were rendered to the following analysis:(1) the histological analysis:take the right lower limb gastrocnemius, fixed by paraformaldehyde, and then observe the change of skeletal muscle morphology by HE staining.(2) mRNA analysis:take the left lower limb gastrocnemius and extract the total RNA for real-time PCR assay to detect the change of TGF-β1mRNA expression.(3) immunohistochemical analysis:take the right lower limb gastrocnemius, fixed by paraformaldehyde, then detect the TGF-β1 by immunohistochemical technique.Results(1) Histological changes:The gastrocnemius cells in the C group were arranged with order, no abnormity; there were no significant morphological changes in the Oh group; the muscle fibers in the 6h and 12h group significantly swell but there were partial necrosis in the latter; the muscle fiber showed disruption in the 24h group with some inflammatory cell infiltration; the inflammatory cells increased in the 48h group; there were a large number of inflammatory cells infiltration in the 72h group; but there were few inflammatory cell infiltration in the 1w group with no significant swelling of muscle fibers, and the muscle fiber in the 2w group gradually recovered to the normal level.(2) mRNA:The expression of TGF-β1 mRNA in the Oh to 2w groups decreased compared to the control group; and the expression of TGF-β1 mRNA at 12h,72h,1w,2w groups were all remarkably decreased (P<0.05).(3) TGF-β1:The content of TGF-β1 in the 0h to 2w groups decreased compared to the control group; and the expression of TGF-β1 in the 0h,6h,72h and 2w groups were all remarkably decreased (P<0.05).Conclusion1. A downhill running exercise could significantly induce skeletal muscle damage, after 2 weeks skeletal muscle injury return to normal, and no fibrosis.2. After a downhill run, the overall expression of TGF-β1 in the skeletal muscle decreased during the repair after injury, not only at the level of transcription, but also at the level of translation.