Orientation of smooth muscle-derived A10 cells in culture by cyclic stretching: Relationship between stress fiber rearrangement and cell reorientation

Mechanical stress causes various responses in cells both in vivo and in vit ro. Realignment of cells and stress fibers is one of the remarkable phenome na that are induced by the stress. However, the mechanism by which their re alignment is controlled is largely unknown. In this study, effects of mecha nical stretch on the morphology of cultured cells were examined using a cyc lic and reciprocal cell stretching apparatus. A10 cells, a cell line derive d from rat aortic smooth muscle, were used as a model, since they are spind le-shaped and have remarkable stress fibers aligned along the longitudinal cell axis. Therefore, the orientation of the cell and stress fibers could b e easily identified. When the cells were cultured on elastic silicone membr anes and subjected to cyclic and reciprocal stretch with an amplitude of 20 % at a frequency of 60 cycles per minute, actin stress fibers were aligned obliquely to the direction of stretching with angles of 50 to 70 degrees wi thin about 15 min after the onset of stretching. Then, after 1-3 hr of cycl ic stretching, the long axes of a majority of the cells were also reoriente d to similar directions to the stress fibers. The stretch-induced cell reor ientation was blocked by 1 mu M cytochalasin B, but not by colcemid. These results indicate that the orientation of cells and actin filaments are clos ely related and actin filaments play a critical role in the early step of t he cell reorientation.