TiO2 nanotubes regulate osteo-adipogenic balance through SREBP1 to determine the fate of bone marrow mesenchymal stem cells

Titanium-based materials are commonly utilized in bone tissue repair due to their exceptional physical and chemical properties. Surface modification of titanium dioxide (TiO₂) nanotubes effectively modulates cellular osteo-adipogenic balance, thereby promoting stem cells osteogenic differentiation. Sterol regulatory element-binding protein 1 (SREBP1), a pivotal transcriptional factor involved in lipid metabolism, plays a significant role in mechanotransduction. Nevertheless, it remains unclear whether SREBP1 also exerts a crucial influence on regulating the differentiation of bone marrow mesenchymal stem cells induced by TiO₂ nanotubes and its involvement in mechanotransduction during this process. Therefore, this study aimed to investigate the mechanistic role of SREBP1 in cell differentiation induced by TiO₂ nanotubes. The results demonstrated that TiO₂ nanotubes exerted regulatory control over SREBP1, enhancing the expression of regulatory factors that induce osteogenic differentiation while suppressing the expression of marker genes associated with adipogenic differentiation. Simultaneously, this regulation inhibited the transcription and translation of pivotal enzymes involved in fatty acid anabolism. Activated by the nanostructure, Lipin1 acted as an upstream target that negatively regulated the expression of SREBP1. The signaling pathway involving Lipin1/SREBP1 was regulated by stress fibers responding to mechanotransduction induced by TiO₂ nanotubes. Consequently, SREBP1 serves as a critical regulatory factor linking mechanotransduction mediated by TiO₂ nanotubes and maintaining homeostasis between stem cell osteo-adipogenic differentiation processes. This provides novel insights for designing biomaterials for bone repair.