Cells perceive the distribution differences of adhesion ligands and consequently establish cellular polarization to regulate osteogenic differentiation.

Abstract

Engineering implant topography has emerged as a promising strategy to promote bone regeneration in complex fractures and large bone defects. Among such topographies, TiO₂ nanotubes serve as a model topography and have been shown, within a certain range, to positively regulate osteogenic differentiation through diameter-dependent effects. However, the underlying mechanisms remains fragmentary. Here, we revealed how cells perceived nanotube interfaces and identified the intracellular force-based mechanotransduction that arose from interface perception. We unexpectedly found that cellular perception of nanotube interfaces depended on diameter-associated topographical cues that induced differential distribution of adhesive ligands. Cells engaged these adhesive ligands to modulate focal adhesion (FA) organization, with small and many FAs forming on the small-diameter nanotubes (30 nm), whereas fewer but larger FAs formed on the large-diameter nanotubes (100 nm). Fewer but larger FAs regulated cytoskeletal assembly, generating greater intracellular force and enhancing cellular polarization. Furthermore, large-diameter nanotubes promoted nuclear pore deformation and YAP nuclear translocation, leading to enhanced osteogenic differentiation both in vitro and in vivo. Together, our findings suggest that nanotube diameter-dependent geometry regulates the spatial presentation of adhesive ligands and subsequently influences FA maturation, cellular polarization, and YAP-associated mechanotransduction. This study provides mechanistic insight into how implant nanotopography modulates osteogenic responses and offers a theoretical basis for the rational design of osteogenic implant surfaces.