Expression Of MiRNA-1 And Differentiation Of Myoblasts In Denervation-induced Skeletal Muscle Atrophy In Rats Intervened By Passive Movement

Objective:(1). To investigate the expression of Micro RNA-1 in denervated skeletal muscle at different periods.(2) To explore effects of passive movement on the expression of miRNA-1 and differentiation of myoblasts in denervation-induced skeletal muscle atrophy.Methods:27 Sprague-Dawle rats weighted(200±10)g were randomly divided into 9groups(n=3). Sham operation was performed in the sham-operated group and were sacrificed at the day of operation. Sciatic nerves of rats were cut off in the denervated and passive movement groups. Rats in the passive movement group were performed passive movement(45° traction and full range flexion) at 1 day after operation,twice per day,600 frequency per day. At 3,7,14 and 28 days after operation,the gastrocnemius were harvested to be measured by HE staining,miRNA-1 in each gastrocnemius were detected by RT-PCR and the expressions of MyoD were determined by RT-PCR and westernblot;differentiation of myoblasts were detected by immunohistochemistry.Results:Atrophy in various degrees was observed in denervated gastrocnemius muscle of denervated and passive movement. The muscle fiber arranged in disorder and the diameter of the muscle cells decreased gradually with the time, without normal structure and morphology. The wet weight ratio and the cell diameter of the gastrocnemius in the denervated and passive movement groups were significantly less than those in the sham-operated group(P<0.05); the wet weight ratio at 7, 14, 28 days and the cell diameter at 7, 14 days of the denervated group were significantly greater than those of the sham-operated group(P<0.05). The expressions of miRNA-1 and MyoD m RNA gradually increased with time in the denervated and passive movement groups, but were significantly less than those of the sham-operated group at each time point(P<0.05). At 7,14, and 28 days after operation, the expressions of miRNA-1 and MyoD m RNA in the passive movement group were significantly higher than those in the denervated group(P<0.05). Immunohistochemical staining showed positive expression of MyoD in all groups at each time point, but higher expression was observed in the denervated and passive movement groups than the sham-operated group; the expression increased with time in the denervated and passive movement groups, and it was significantly higher in the passive movement group than the denervated group. The correlation analysis results showed that the overall change trend of miRNA-1 and MyoD had no relation with the gastrocnemius wet weight ratio at 3 and 7 days(P>0.05), and had positive correlation at14 and 28 days(P<0.05); positive correlation was found between the relative expression of MyoD and miRNA-1 m RNA(P<0.05).Conclusion :Passive movement can prevent amyotrophy by increasing the expression of miRNA-1 and promoting the differentiation of myoblasts.