DIRECTIONAL DEPENDENCE OF SENSING CHARACTERISTICS TO MECHANICAL STIMULUS IN OSTEOBLASTIC CELLS

Abstract. It is widely recognized that living bone tissue can change its structure to adapt to the mechanical environment. Osteoblasts play an important role in this adaptive bone remodeling process to reconstruct a new bone, and are believed to sense mechanical stimuli such as stress/strain. However, the mechanism by which cells sense and transduce mechanical signals to the intracellular biochemical-signaling cascade is still unclear. Present study addresses this issue by investigating the characteristics of the response of a single MC3T3-E1 osteoblastic cell to a mechanical stimulus. First, by applying quantitative perturbation to a single cell by a microneedle, the change in intracellular calcium ion concentration [Ca2+]i was observed as a primal signaling response to the mechanical stimulus, and the threshold value of the perturbation as the mechanical stimulus was quantitatively evaluated. Second, to study directional dependence of the response to the mechanical stimulus, the effect of actin fiber orientation on the threshold value of the calcium response was investigated at various magnitudes and directions of the stimulus. As a result, directional dependence of the osteoblastic response to the perturbation was found. This result is phenomenological evidence that the cytoskeletal actin fiber structures are involved in the mechanotransduction mechanism. 1