MOLECULAR AND CELL BIOLOGICAL STUDY ON CELLULAR RESPONSE TO MECHANICAL STRESS

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The stress fiber is one of the most prominent cytoskeletal components that contribute to the maintenance of cell architecture. It has generally been believed that upon cyclic stretching, both cells and their stress fibers become perpendicularly aligned to the direction of stretching. However, using our newly developed stretching device, we have recently found the contrary evidence that stress fibers in endothelial cells rapidly become rearranged at a specific oblique angle relative to the direction of stretching. In light of this finding, we attempted to establish the explanation for such a phenomenon either experimentally or theoretically. It was thus revealed that stress fibers align at a particular angle so as to minimize their length alterations in cyclic deforming fields. Rearrangement of the stress fibers at this angle probably occurs as a result of avoiding compressive stress and may be interpreted as a way of reducing the mechanical stress to which. they are subjected during the deformation. This hypothesis explains well the reason not only for the survival of the stress fibers at a particular oblique angle, but also for the reduced numbers of stress fibers found, at the other angles on cyclic deforming fields. Moreover, theoretical study supports this hypothesis of intracellular stress fiber orientation under cyclic deformation.We also expand our study from microscopic level to macroscopic level, that is, individual human being. Exercise with skeletal muscle contraction can be considered to mechanical stress from the standpoint of cells in body. We studied cellular response to both endurance and resistance exercise.