Microvibration stimuli causes localized depolymerization of the actin cytoskeleton of osteoblasts around the nucleus

Reports have indicated that microvibration stimulation activates bone remodeling and promotes bone formation. However, the mechanism by which microvibration stimulation facilitates bone formation remains incompletely understood, and it is unclear how osteoblasts sense microvibration stimulation. In this study, we focused on the actin cytoskeleton, a key component of the mechanosensing mechanism. The actin cytoskeleton plays a role in mechanotransduction by physically transmitting mechanical stimuli from the cell surface to the interior of the cell. It is also known that actin stress fibers undergo structural remodeling in response to changes in the tension acting upon them. We investigated the structural remodeling of the actin cytoskeleton in osteoblasts subjected to microvibration stimulation using fixed cells and fluorescence staining of actin. Our results revealed that in osteoblasts subjected to microvibration, local actin depolymerization occurred around the cell nucleus for approximately 3 hours following the application of vibration. Furthermore, by 10 hours post-vibration, the actin cytoskeleton had repolymerized and returned to its pre-vibration state. These findings suggest that microvibration stimulation is transmitted from focal adhesions to the actin cytoskeleton surrounding the cell nucleus and then further into the cell.