2012 年 7 巻 2 号 p. 130-140
In order to determine how cells change their traction forces at focal adhesions (FAs) under macroscopic deformation conditions, we investigated the dynamic changes in traction force at FAs by culturing porcine aortic smooth muscle cells (SMCs) on elastic micropillar substrates and giving them macroscopic deformation by stretching the substrates. We patterned adhesion region on the top surface of a polydimethylsiloxane-based micropillar array using our original micropatterning technique to align the cells on the pillar array parallel to the stretch direction. SMCs plated on the micropillars successfully spread in the adhesion region and their actin stress fibers (SFs) aligned in the direction to be stretched. Cells were then stretched and released cyclically with strain rates of 0.3%/15s up to 3—6% strain, and deflection of micropillars at both side regions of cells were measured simultaneously to obtain the traction force at each FA in situ. SMCs aligned in the stretch direction showed two types of responses: almost a half of the SMCs changed their force in phase with the applied strain, and showed gradual active contraction with the stretch cycles (synchronous group); and the rest tended to keep their force constant and became elongated with the cycles (asynchronous group). In the asynchronous group, the force sometimes changed in antiphase with the cell strain as if the cells maintain intracellular traction force at a constant level. These results may indicate that SMCs sometimes exhibit active homeostatic responses to keep their pretension constant during macroscopic stretching, and such tensional homeostatic responses may occur concurrently with cell elongation.
