| Objective The process of repair and regeneration after skeletal muscle injury is complex and continuous,which involves the regulation of various growth factors.In recent years,the micro RNAs family has been recognized as a key regulator of many developmental processes.Some studies have found that the upstream of micro RNA-133 a is regulated by myogenic regulatory factors Myo D and Myo G.The downstream of micro RNA-133 a participates in the regulation of proliferation and differentiation of muscle satellite cells through negative regulation of IGF-1R acting on PI3K/AKT signaling pathway.In this study,the skeletal muscle injury model induced by one-off downhill running was used to explore the expression of micro RNA-133 a and related regulatory factors at different time after injury,and to further understand the regulation mechanism of skeletal muscle injury repair process,so as to provide a new experimental basis for the treatment of skeletal muscle injury.Method Seventy-two healthy two-month-old male SD rats were randomly divided into 9 groups,8 rats in each group,the control group(C)and the experimental group,respectively.The experimental group included 0 hours after exercise,6 hours after exercise,12 hours after exercise,24 hours after exercise,48 hours after exercise,72 hours after exercise,1 week after exercise and 2 weeks after exercise.All rats were fed in cages and fed freely.Rats in the experimental group were given one-off downhill running.The specific parameters of the animal model in the experimental scheme were as follows: the inclination angle of the treadmill was-16 degrees,the speed was 16 m/min,and the total exercise time was 120 minutes.Rats in the control group did not run downhill,but the other conditions were the same as those in the experimental groups.Rats in the experimental group were sampled at 0,6,12,24,48,72,1 and 2 weeks after exercise respectively.Rats in the control group were sampled directly at bilateral gastrocnemius muscles.The following experimental operations were performed:(1)HE staining of paraffin section of gastrocnemius muscle was used to observe the morphological changes of gastrocnemius muscle in the process of injury repair.(2)RT-PCR was used to detect the changes of the expression levels of micro RNA-133 a,Myo D and Myo G.(3)Western-Blot was used to detect the expression of Myo D,Myo G,IGF-1R and p-AKT protein.Results 1.HE staining results showed that the muscle fibers in the control group were polygonal and arranged tightly,and the nuclei were distributed at the edge of muscle cells;some muscle fibers began to round in the 0-12 H group after exercise;a small amount of basophilic granules were observed in the 24 h group after exercise,suggesting that inflammatory cell infiltration might occur;inflammatory cell infiltration appeared in the 48 h group after exercise;inflammatory cell infiltration was obvious in the 72 h group after exercise;The swelling of muscle fibers was not obvious in the latter 1W group,and the cell morphology tended to be regular.In the 2W group,the muscle fibers basically returned to normal shape after exercise,suggesting that the repair process was basically completed.2.Changes of the expression of micro RNA-133 a and Myo Dm RNA and Myo Gm RNA: Compared with the control group,the expression of micro RNA-133 a increased firstly and then decreased,and there was significant difference between the groups at 6h and 12 h after exercise(P < 0.05).Myo D m RNA expression level decreased immediately after exercise in the 0 h group,with significant difference compared with the control group(P < 0.05).The expression level of Myo G m RNA increased first and then decreased.There was no significant difference between the two groups.3.Changes of Myo D,Myo G,IGF-1R and p-AKT protein expression: Compared with the control group,the expression of Myo D protein increased first and then decreased.There were significant differences in the groups of 0 h,6 h and 48 h after exercise(P < 0.05).The expression of Myo G protein first decreased and then increased,and there were significant differences between the two groups at 0 h,6 h,12 h,24 h and 72 h after exercise(P < 0.05).The expression level of IGF-1R protein decreased first and then increased.Compared with the control group,the expression level of IGF-1R protein had significant difference at 0 h,6 h and 12 h after exercise(P < 0.05).The expression level of p-AKT protein decreased first and then increased.Compared with the control group,there were significant differences in the groups of 0 h,6 h,12 h and 72 h after exercise(P < 0.05).Conclusion 1.One-off downhill running can successfully cause skeletal muscle injury,which can be repaired 2 weeks after injury.2.In the process of repairing skeletal muscle injury caused by one-off downhill running,the upstream of micro RNA133 a may be positively regulated by myogenic transcription factor Myo D.The downstream promotes the repairing process of skeletal muscle injury by negatively regulating the expression of IGF-1R protein in PI3K/AKT signaling pathway. |
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