[Osteocytes and mechanical stress].

A number of fascinating studies suggest that osteocytes play an important role in bone metabolism, especially in its regulation by mechanical stimuli. However, it has been still discussed how the osteocytes were activated by mechanical stimuli. For example, direct mechanical load applied to cells at levels measured to occur in humans in vivo do not affect bone cells in vitro . In order to solve the contradiction, theories based on fluid flow-induced shear stress stimulation around osteocytes in bone have appeared with the most prominence. In addition, I would like to introduce recent hypothesis to mechanically stimulate osteocyte, such as strain amplification by radial hoop strains, flow induced integrin mediated signaling, and osteocyte lacuna strain. To validate the availability of these hypothesis, it is important to observe 3-dimensional osteocyte morphology as well as its interaction with pericellular matrix.