Proliferation in Skeletal Muscle Satellite Cells after Mechanical Stretch with Various Frequencies

Abstract

PURPOSE: When skeletal muscle is stretched, satellite cells are activated to enter the cell cycle, but the frequencies of mechanical stretch in satellite cells proliferation has not been assessed previously. The purpose of the present study was to determine the stretch frequencies on growth of muscle satellite cells by primary culture technique. METHODS: Cultured quiescent satellite cells were subjected to mechanical stretch in a FlexerCell 4000T System. satellite cells were subjected to mechanical strain for 6 hours per day over a period of 4 days with the frequencies of 0, 0.5, 1 and 2 Hz, respectively. Cell cycle distribution of satellite cells was detected using flow cytometry. Total RNA was extracted from the cells samples and RT-PCR detection was used to evaluate mRNA of MGF, MyoD and Myf5 relative expression. RESULTS: The morphology of satellite cells became a typical long spindle following mechanical stimulation, Compared with the control group, The amount of cells in G0/G1 phase at 0.5 Hz, 1 Hz group was significantly decreased (p <0.05), while the amount of cells in S + G2/M phase increased (p <0.05). Compared with 0 Hz group, the amount of cells in G0/G1 phase at 0.5 Hz, 1 Hz and 2 Hz group was significantly decreased (p <0.05). However, the amount of S + G2/M phase cells was significantly increased (p <0.01). Compared with the control group, the expression of Myf5 and MGF mRNA in 1 Hz group was significantly increased (p <0.05), and other treatment groups increased too, but no significant difference (p > 0.05). Compared with the control group, the expression of MyoD mRNA in all treatment groups was significantly increased (p < 0.05), and 1 Hz and 2Hz groups were highly significantly increased (p <0.01), but there was no significant difference between the experimental groups. CONCLUSIONS: The mechanical stretch stimulated the proliferation of skeletal muscle satellite cells, which is related to the frequency of strain stimulated the expression of MyoD, Myf5 and MGF mRNA. Supported by Grant from National Natural Science Foundation of China No.30800542, No.10572097.