The Effects and Mechanisms of Mechanical Stretch on the Proliferation of Satellite Cells in Rat Skeletal Muscle

Objective:To investigate the effects and mechanisms of different traction modes on the proliferation of rat skeletal muscle satellite cells. Methods:Satellite cells were isolated and purified by two-step enzymatic digestion and differential adherence centrifugation. The third generation satellite cells were collected and a Flex cell pulling system was used to stretch the cells at a frequency of 1 Hz,and 5% and 15% stretches for 4 h and 6 h,respectively. The CCK-8 was used to detect the proliferation of satellite cells at 24 hours after the stretch;the activity of Akt,P38,ERK and JNK was detected immediately after the stretch and at 24 hours after the stretch,and the expression of Myf5 and MyoD was also detected at 24 hours after the stretch. Result:1)Compared with the control group(no stretch,the same below),15% stretch for 4 h or 6 h was increased the proliferation of skeletal muscle satellite cell(P<0.01),but the 5% stretch for 4 h or 6 h had was no significant proliferation(P>0.05);2)A higher protein expression in Myf5 was observed after 15% stretch for 6 h than that of the control group(P<0.01),and the protein expression of MyoD at 4 h and 6 h was both higher than that of the control group(P<0.01). However,no significant difference was observed in the expression of MyoD and Myf5 after 5% stretch for 4 h or 6 h compared with the control group(P>0.05);3)Immediately and 24 hours after traction:The activities of Akt,P38,ERK and JNK after 15% stretch for 4 h or 6 h were higher than those in the control group(P<0.01;P<0.05). However,no significant difference was observed in the activities of Akt,P38,ERK and JNK after 5% stretch for 4 h or 6 h against the control group. There was no significant change(P>0.05). Conclusion:Mechanical traction with 15% stretch can promote the proliferation of skeletal muscle satellite cells,which may be achieved by activating Akt,P38,ERK,JNK pathways.