Mechanisms Of Response To Mechanical Strain In Differentiation Of Osteogenic From Mesenchymal Stem Cells

Objective To study the effect of cyclic substrate deformation on the mechanical signaling pathway of mouse Mesenchymal Stem Cells(MSCs) line(Dl). Methods Cyclic strain(3% 0.5Hz) was applied to mouse MSCs in osteogenic media. The ways of immunocytochemistry, RT-PCR were used to analyse the gene expression of OSX(Osterx),osteocalcin (OCN) ,and the protein of alkaline phosphatase (ALP), type I collagen (COL1) and OCN; the structure of microfilament and Ca²⁺ levels were detected by confocal laser scanning microscope (CLSM); The signaling inhabitors,such as SB203580 ( p38MAPK specific inhabitor ) , PD98059(MEK-1/2MAPK specific inhabitor), LY294002 (PI₃Ks specific inhabitor ), Cytochalasin B (microfilament specific inhabitor), EGTA (Ca²⁺specific inhabitor) , were used to investigate mechanical signaling pathway.Results The cyclic substrate deformation could stimulate increasing expression of ALP, type I collagen, OCN and activate the gene expression of OSX and OCN over unstrained cells.Mechanical strain changed the structure of microfilament and cell reorientation, and promoted obviously Ca²⁺ levels. Ca²⁺ sparks releasing were observed with fluo-3-AM by strain-induced. Strain-induced the expression of mRNA of OSX,OCN was largely mediated by Ca²⁺ signaling and Phosphatidylinositol-3-kinases(PI₃Ks) pathway.Conclusions Strain can enhance differentiation of mesenchymalstem cells to osteogen . Microfilament, Ca²⁺ signaling and PI₃Ks pathway play an important role on strain-induced mesenchymal stem cells differentiation.