CELL-ADAPTABLE HYDROGELS PROMOTE BONE REGENERATION BY ENHANCING MECHANOSENSING OF MESENCHYMAL STEM CELLS

The mechanical cues provided by the bone extracellular matrix (ECM) are essential for regulating cellular mechanics and metabolism, thereby driving osteogenic differentiation of bone marrow mesenchymal stem cells (MSCs). While microtubules have emerged as key players in cellular mechanotransduction, the role of microtubule post-translational modifications in mechanosensitive signaling and differentiation remains poorly understood. In this study, we engineered a high-dynamic hydrogel, crosslinked via host-guest complexation between p-tert-butylphenyl-modified hyaluronic acid (HA-TP) and β-cyclodextrin. The dynamic nature of the hydrogel networks, with frequent association and dissociation of the host-guest linkages, enables fast network remodeling, as evidenced by fast stress relaxation within 10 seconds. Micro-rheological analysis demonstrated that this high-dynamic HA-TP hydrogel significantly enhanced the microscopic Brownian movement of nanoparticles relative to the control hydrogel with lower network dynamics. This cell-adaptable hydrogel mimics the early stages of intramembranous ossification, promoting the proliferation, spreading, and migration of encapsulated human MSCs (hMSCs). Mechanical signals from the hydrogel are transmitted through focal adhesions to the microtubules, triggering detyrosination of microtubules by the VASH2 enzyme. This detyrosination stabilizes microtubules, facilitating the transport of lipid droplets closer to mitochondria, which in turn enhances lipid consumption and supports osteogenic differentiation of MSCs. Furthermore, in vivo studies revealed that mesenchymal stem cells loaded with the high-dynamic hydrogel significantly promoted bone regeneration in rat skulls. These findings unveil a novel mechanism by which mechanotransduction mediates microtubule post-translational modifications, linking cellular energy status to microtubule dynamics in stem cells. The insights gained from this study provide a foundation for understanding the role of cytoskeletal mechanotransduction in cellular function and tissue regeneration.