Effects and mechanism of mechanical stretch promoting proliferation and inhibiting osteogenic and adipogenic differentiation of skeletal satellite cells in mice
Objective To investigate the effect of mechanical stretch on the proliferation and differen-tiation of skeletal satellite cells in mice,and explore its mechanism.Methods The research was divid-ed into two parts.In the first part,all mice were not given osteogenic or adipogenic induction,and randomly divided into a control group,a mechanical stretch(MS)group,a solvent control group[Di-methyl sulfoxide(DMSO)+mechanical stretch],a Notch inhibitor(KY-02111)+mechanical stretch group and a Wnt inhibitor(FLI-06)+mechanical stretch group,with the aim to evaluate cell prolifera-tion and migration,and the effect of mechanical stretch on the Wnt and Notch signaling pathway.In the second part,all mice were randomly divided into 6 groups:a control group,an induced differentia-tion(ID)group,an induced differentiation+mechanical stretch(IDMS)group,an induced differentia-tion+DMSO+mechanical stretch(IDDMS)group,an induced differentiation+Notch inhibitor(KY-02111)+mechanical stretch(IDNMS)group,and an induced differentiation+Wnt inhibitor(FLI-06)+mechanical stretch(IDWMS)group.All groups except the control group were induced differenti-ation using osteoblastic or adipogenic medium,and the IDMS group was applied tensile stress to the cell basement membrane,with the IDDMS and IDNMS groups given DMSO and KY-02111 or FLI-06 with a final concentration of 5 μM into the culture medium,respectively.On the 7th and 14th days af-ter culture,cell proliferation was detected using CCK-8,while on the 14th day after culture,cell mi-gration was observed using the streak method.Alkaline phosphatase and oil red staining were per-formed on all cells.Moreover,the mRNA expression of osteogenic[alkaline phosphatase(ALP)and Runt-related transcription factor(Runx)-2]and adipogenic[fatty acid-binding protein(FABP)4 and li-poprteinlipase(LPL)]differentiation marker genes were quantitatively detected by using the real-time PCR.Meanwhile,while the expression of c-Myc and Cyclin B(CCNB)1 proteins was measured using Western blotting.Results Cell proliferation increased significantly in MS group compared with the con-trol group(P<0.01),while that of IDMMS and IDNMS groups decreased significantly compared with MS group.As to cell migration,MS group was significantly better than the control group(P<0.01),while there was a significant decrease in both IDMMS and IDNMS groups compared with MS group(P<0.01).According to ALP and oil red staining,a significant increase in ALP activity and lipid droplet secretion was observed in skeletal muscle satellite cells of ID groups compared with the control group,with the increase in IDMMS and IDNMS groups significantly greater than MS group.More-over,the results of real-time PCR showed that the expression of ALP and Runx-2mRNA in the osteo-genic induction group and the FABP4 and LPL mRNA in the adipogenic induction group increased sig-nificantly compared with the control group(P<0.05),with a significant decrease in the above measure-ments of IDMS group compared with ID group,but a significant increase in IDMMS and IDNMS groups compared with IDMS group(P<0.01).Meanwhile,according to Western blotting,the expres-sion of c-Myc and CCNB1proteins increased significantly in the skeletal muscle satellite cells of MS group compared with the control group(P<0.01),while that of IDMMS and IDNMS groups decreased significantly compared with MS group(P<0.01).Conclusion Mechanical stretch can promote the prolif-eration and migration of skeletal satellite cells in mice,but inhibit osteogenic and adipogenic differenti-ation.Its mechanism is related to the activation of Wnt and Notch signal pathways.
skeletal muscle satellite cellsdifferentiationmechanical stretchWnt signal pathwayNotch signal pathway
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