EFFECT OF PASSIVE MOVEMENT ON EXPRESSION OF miRNA-1 AND DIFFERENTIATION OF MYOBLASTS IN DENERVATION-INDUCED SKELETAL MUSCLE ATROPHY IN RATS

Abstract

To investigate the expression of miRNA-1 in denervated skeletal muscle at different periods, and to explore effects of passive movement on the expression of miRNA-1 and differentiation of myoblasts in denervation-induced skeletal muscle atrophy in rats. Twenty-seven Sprague Dawley rats, weighing (200±10) g, were randomly divided into sham-operated group (group A, n=3), denervated group (group B, n=12), and passive movement group (group C, n=12). After the right sciatic nerve was exposed and dissociated, the sciatic nerve of 1 cm in length was removed in groups B and C; resection was not performed in group A. At 1 day after operation, passive flexion and extension movement was performed on the right hind limb in group C. At 6 hours in group A and at 3, 7, 14, and 28 days in groups B and C, 3 rats were sacrificed to measure the wet weight ratio of gastrocnemius muscle, to observe the diameter of the gastrocnemius muscle cell and evaluate the muscle atrophy by HE staining; RT-PCR was used to detect the mRNA expression of miRNA-1 and myocyte differentiation factor (MyoD), and immunohistochemistry to determine the protein expression of MyoD. Atrophy in various degrees was observed in denervated gastrocnemius muscle of groups B and C. 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 groups B and C were significantly less than those in group A (P<0.05); the wet weight ratio at 7, 14, 28 days and the cell diameter at 7, 14 days of group B were significantly greater than those of group A (P<0.05). The expressions of miRNA-1 and MyoD mRNA gradually increased with time in groups B and C, but were significantly less than those of group A at each time point (P<0.05). At 7, 14, and 28 days after operation, the expressions of miRNA-1 and MyoD mRNA in group C were significantly higher than those in group B (P<0.05). Immunohistochemical staining showed positive expression of MyoD in groups A, B, and C at each time point, but higher expression was observed in groups B and C than group A; the expression increased with time in groups B and C, and it was significantly higher in group C than group B. 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 at 14 and 28 days (P<0.05); positive correlation was found between the relative expression of MyoD and miRNA-1 mRNA (P<0.05). Passive movement can prevent amyotrophy by increasing the expression of miRNA-1 and promoting the differentiation of myoblasts.