Mechanical strain promotes osteogenic differentiation of mesenchymal stem cells on TiO₂ nanotubes substrate

Previous studies demonstrated cycle mechanical strain induced osteogenic differentiation of MSCs. But in general, MSCs are typically seeded on a flexible membrane or within a soft matrix. TiO₂ nanotubes substrate topography plays a critical role in promoting the MSCs response and affects MSCs fate. Titanium implants surface modified by TiO₂ nanotubes topography provides the opportunity to improve osseointegration by additionally regulating the MSCs fate. Titanium is one of most commonly used materials in the orthopedics and can undergo elastic deformation under certain mechanical stress. Therefore, for clinic trails, it is necessary to investigate the effect of mechanical strain on osteogenesis of MSCs on TiO₂ nanotubes modified titanium substrate. But until now, there has been no research focused on the relationship between mechanical strain and osteogenesis of MSCs on the TiO₂ nanotubes topography substrate. Here, we firstly applied the mechanical stress to the TiO₂ nanotubes modified titanium specimen to investigate the effects of mechanical strain on the biological behaviors of MSCs. Our present study showed that mechanical strain promoted cell proliferation, spreading and increased vinculin expression of MSCs on the TiO₂ nanotubes substrate. Additionally, mechanical strain enhanced the ALP activity and osteogenesis genes expression such as Runx2, BSP, ALP, OPN and OCN. Our results preliminarily demonstrated that mechanical strain enhanced the osteogenic differentiation of MSCs through the FAK-Erk1/2-Runx2 pathway on the TiO₂ nanotubes substrate.