Molecular Biological Changes in Reloaded Skeletal Muscles after Rat Hindlimb Suspension

Abstract. [Purpose] The purpose of this study was to clarify the expression changes of MyoD mRNA under reloading rat skeletal muscles after hindlimb suspension. [Subjects] The subjects were 27 Wistar male rats aged 8 weeks old. [Methods] They were randomly divided into a control group (n=5) and 4 experimental groups (n=5 to 6). The experimental groups were all submitted to 14 days of hindlimb suspension provoking muscle disuse atrophy, and afterwards they were assigned to no-reload hindlimb suspended group (HS) and 2, 7 and 14 days reloading groups (2D, 7D, 14D). [Results] The MyoD mRNA expression level increased in the HS group was significantly higher in the 2D reloading group and decreased to controls levels in the 7D reloading group. [Conclusion] The MyoD mRNA expression results suggest that reloading after hindlimb suspension stimulates satellite cell activation. Furthermore, the peak of MyoD mRNA expression was observed after 2 days of reloading.