Biomechanics on nano- and micro-mechanical systems in bone cells

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It is recognized that bone cells can sense mechanical stimuli, however, the mechanism by which cells sense mechanical stimulus and transduce it into intracellular biochemical signals is still not clearly understood. This study focuses on actin cytoskeleton as a functional component in the mechanosensory system. First, intracellular tension in the actin stress fibers was locally released in an osteoblastic cell, and it was found that tension-released stress fibers were selectively disassembled, suggesting that tension is essential for a stability of the stress fibers. Second, mechanical perturbation was applied to a single cell using a microneedle, and the calcium resoponse and membrane deformation were simultaniously observed using multiple fluorescent labeling techniques. These studies suggested that interactions among mechanical and biochemical factors would be key issues to explore detail mechanosensory mechanism.Based on these results, we further conducted an in vitro experiment an … More d in silico simulation for cytoskeletal actin filament. First, using a crawling cells on the substrate, we investigated a spatiotemporal regulation of the actin filament network in the lamellipodium in which the interactions among mechanical and biochemical factors are involved. Quantitative evaluation of the strain field of actin network struture revealed that the presense of negative incremental strains in the lamellipodium whose direction is parallel to the crawling direction. This result suggests that biomechanical factors such as tension release in the filament is involed in the regulation of actin filament depolymerization, thereby contributiong to the regulation of cell dynamics. Furthermore, we conducted a molecular dynamics simulation for a single actin filament to clarify the effect of acting tensile force on the twisting behavior, and we found that the tension-twisting coupling behavior was observed and its twisting angle depends on the tensile force itself, suggesting a biomechanical and biochemical coupling may be involved in the depolymerization initiated by the tension release. Less