Effect Of Mechanical Stretching On Invasive Behavior Of BMSCs And Related Molecular Mechanism

Bone?marrow?derived mesenchymal stem cells(BMSCs)are pluripotent stem cells with self-renewal and differentiation ability,which play an important role in healing of damaged tissue and regenerative medicine.However,BMSCs transfer from bone marrow microenvironment to target tissue is a complex process.This process is very complex,influenced by mechanical and chemical factors.At present,studies have shown that BMSCs proliferation,differentiation and migration are all affected by mechanical stimulation.Our previous study has shown that cyclic mechanical stretch can promote BMSC migration but inhibit BMSC invasion.However,the related molecular mechanism,especially the molecular mechanism of inhibiting BMSC invasion,is not clear.Based on this,the molecular mechanism of mechanical stretch affecting the invasion ability of BMSCs was further investigated in this paper.MT1-MMP is a member of the MMPs family,and its main function is to degrade the ECM,which plays an important role in the process of cell invasion.The PI3K/Akt signaling pathway is involved in mediating the expression and activity of MMPs and plays an important role in the process of cell invasion.Therefore,in this study,the primary BMSCs were isolated from the femur and tibia of the hind limbs of rats by whole bone marrow adherent and cultured for passages.BMSCs were then loaded by mechanical stretching loading device and their invasion ability was detected.The effect of mechanical stretching on MT1-MMP expression and the effect of MT1-MMP on the invasion ability of BMSCs were further tested.Finally,the effect of mechanical stretching on the activiation of PI3K/Akt signaling pathway and the effect of PI3K/Akt signaling pathway on the expression of MT1-MMP and the invasion ability of BMSCs were investigated.Results showed that the invasion ability of BMSCs was significantly reduced by mechanical stretching,and the expression level and optical intensity of MT1-MMP were also down-regulated.The invasion ability of BMSCs was significantly increased by overexpression of MT1-MMP,and overexpressing MT1-MMP restored mechanical-stretching-reduced BMSCs invasion,suggesting that the invasion ability of BMSCs is regulated by MT1-MMP.In addition,the activation of PI3K/Akt signaling pathway was significantly reduced by mechanical stretching.The relationship among PI3K/Akt signaling pathway,MT1-MMP expression and BMSC invasion ability wasfurther studied,and it was found that under the treatment of PI3 K inhibitor LY294002,the phosphorylation level of Akt,MT1-MMP expression level and BMSC invasion ability were significantly decreased.BMSCs were treated with Akt inhibitor A-443654 and similar results were obtained.Furthermore,the application of Akt phosphorylation activator SC79 upregulated Akt phosphorylation,which increased the expression of MT1?MMP and BMSC invasion.Moreover,the treatment of SC79 inhibited the mechanical stretching-reduced BMSC invasion.In this study,we reveal that mechanical stretching inhibits BMSC invasion by downregulating MT1?MMP expression by suppressing the PI3K/Akt signaling pathway.This study can increase the understanding of the mechanical transduction mechanism of BMSCs,and provide theoretical guidance for further study on BMSC motility regulated by mechanical stimuli.