Dynamic-stiffening collagen-coated substrate enhances osteogenic differentiation of mesenchymal stem cells through integrin α2β1

Matrix stiffness dynamically increases during the bone formation process. Enhancement of the osteogenic differentiation of mesenchymal stem cells (MSCs) by the dynamic stiffening of the substrate has been reported in previous research. However, the mechanism by which the dynamic stiffening of the matrix effects the osteogenic differentiation of MSCs remains quite unknown. A previously reported dynamic hydrogel system with dynamic matrix stiffening was used in this study to investigate the mechanical transduction mechanism of MSCs. The integrin α2β1 and phosphorylation focal adhesion kinase levels were evaluated. The results indicated that dynamic stiffening of the matrix mediated the activation of integrin α2β1, and further influenced the focal adhesion kinase (FAK) phosphorylation level of MSCs. In addition, integrin α2 is a probable integrin subunit that causes integrin β1 activation during the matrix dynamic stiffening process. The integrin β1 is the main integrin subunit regulating the osteogenic differentiation of MSCs induced by FAK phosphorylation. Overall, the results suggested that the dynamic stiffness facilitated the osteogenic differentiation process of the MSCs by regulating the integrin-α2β1-mediated mechanical transduction pathway, which implied that integrin α2β1 played a crucial role in the physical biological coupling in the dynamic matrix microenvironment.