| ObjectiveExercise-induced muscle injury and muscle repair is a complex and continuouspathological process, which were adjusted by a lot of growth factors. In the damagedstage have muscle fiber necrosis and infiltration of inflammatory cytokines; and in therepair stage have activation proliferation and differentiation of skeletal musclesatellite cell. In recent years, many studies have confirmed that microRNAsparticipate in the regulation of various physiological activities of skeletal muscle,including miR-206which is a skeletal muscle-specific miRNA. This study aims toadopt the method of histology to observe the morphological changes of skeletalmuscle fibers after the disposable downhill running through the animal model of EIMIestablished by Armstrong; and at the same time observe the expression changes of theskeletal muscle specific miRNA--miR-206and its upstream transcription factorMyoD, as well as to further improve and enrich the molecular mechanism of theskeletal muscle injury and repair process, and to provide new theoretical basis andtreatment for exercise-induced injuries and muscle lesions.Methods72only2months of good exercise ability male SD rats, were randomly divided intocontrol group and exercise group, exercise group is divided into0h after exercisegroup,6h after exercise group,12h after exercise group,24h after exercise group,48h after exercise group,72h after exercise group,1w after exercise group,2w afterexercise group, and each group of eight rats. At formal exercise intervention period,the control group didn’t intervene, other exercise groups rats were ran a continuousdownhill running exercise intervention, at speed16m/min, as-16°slope, the totalrunning time is90min.After the movement, rats anesthesied respectively after0h,6h,12h,1d and2d,3d,1w,2w later, and remove the bilateral gastrocnemiusquickly. Then conduct the following experiments:1) Using Histological identification of HE staining to observe the changes of shapeand structure of skeletal muscle after the various periods of EIMI;2) Using western blot to detect TGF-β1and MyoD protein expression;3) Using RT-PCR experiments to test the expression changes of TGF-β1,MyoDmRNA level and skeletal muscle miRNA--miR-206.Results1) Histological results showed: the skeletal muscle morphological structure of groupC is normal, after6h found skeletal muscle fibers turn round, it tips swollen,swollen still exists and gradually increase after24h,48h after found the inflammatory cell infiltration,72h later basophilic granules, most prompt damagedegree is most serious, occasional inflammatory cells after1w, no swelling,2wlater muscle fiber returned to normal muscle fiber morphological structurebasically.2) Western blot results showed: After one-time downhill running, the expression ofTGF-β1protein are decreased except the group1w compared to group C; at0-48hit decreased gradually, and then began to rise, and then at2w it returned to thenormal level; but the MyoD protein expression level was increased in48h,1w,2w group after running in the gastrocnemius of rats; at0h to48h the expression ofMyoD gradually increased; at48h it reached on a peak, and then drop rapidly at72h;1w it began to increase;3) RT-PCR results showed: After one-time downhill running, the expression ofMyoD mRNA in group48h、1w、2w compare to group C is increased; the TGF-β1mRNA are incrased compared to group C,and the miR-206are decreasedcompared to group C; TGF-β1mRNA increased from6h to24h, and then beganto decline; the expression of MyoD mRNA and miR-206were up-regulatedimmediately after exercise with the time in6-12h;12hours later reached on apeak, then began down-regulated,2w later down-regulated to the normal level;Conclusions1) One-time downhill running can lead to injury of rat gastrocnemius; and the injuryskeletal muscle can repair to normal level after2w;2) In the course of a downhill running, MyoD may activate the expression ofmiR-206, and promotes muscle repair after injury. |
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