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• Substrate stiffness influences the osteogenesis of SMCs. • Transforming growth factor-β1 involves in the osteogenesis of SMCs. • SMCs on the substrate of intermediate stiffness show higher osteogenesis level. Vascular stiffening occurs with advanced age and under pathological conditions such as vascular calcification, during which the osteogenesis of smooth muscle cells (SMCs) plays a key role. However, whether the stiffness of cellular microenvironment influences osteogenic responses in vascular SMCs is not well understood. Here, we cultured SMCs on the poly(dimethylsiloxane) (PDMS) substrates with varying stiffness from 0.363 to 2.327 MPa. The cell osteogenic transdifferentiation was induced by β-glycerophosphate. Our findings demonstrated that the extent of osteogenesis in SMCs varied with the substrate stiffness. On three substrate stiffness, cells on the intermediate one (0.909 MPa) showed the highest extent of the osteogenesis based on the expression of osteogenic markers and calcium deposition. Transforming growth factor-β1 and autophagy were involved in this stiffness-dependent process. This work highlights the importance of substrate stiffness to the osteogenesis of vascular SMCs, giving new scientific information for understanding of SMCs-mediated vascular calcification and designing of vascular implants. [ABSTRACT FROM AUTHOR]

Changes in the stiffness of the cellular microenvironment are involved in many pathological processes of blood vessels. Substrate stiffness has been shown to have extensive effects on vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs). However, the material stiffness of most previously reported in-vitro models is ranging from ~100 kPa to the magnitude of MPa, which does not match the mechanical properties of natural vascular tissue (10–100 kPa). Herein, we constructed hydrogel substrates with the stiffness of 18–86 kPa to explore the effect of physiological stiffness on vascular cells. Our findings show that, with the increase of stiffness at the physiological range, the cell adhesion and proliferation behaviors of VECs and VSMCs are significantly enhanced. On the soft substrate, VECs express more nitric oxide (NO), and VSMCs tend to maintain a healthy contraction phenotype. More importantly, we find that the number of differentially expressed genes in cells cultured between 18 kPa and 86 kPa substrates (560 in VECs, 243 in VSMCs) is significantly higher than that between 86 kPa and 333 kPa (137 in VECs, 172 in VSMCs), indicating that a small increase in stiffness within the physiological range have a higher impact on vascular cell behaviors. Overall, our results expanded the exploration of how stiffness affects the behavior of vascular cells at the physiological range. [Display omitted] • Changes in the stiffness of a material at the physiological range have a stronger effect on the vascular cells. • Materials stiffness affects endothelial cell adhesion and function • Smooth muscle cell proliferation and phenotype are affected by materials stiffness. [ABSTRACT FROM AUTHOR]