![]() Cell adhesion involves binding and clustering of integrins to ECM ligands ( 1, 2), active spreading of the cells across the substrate ( 3, 4), and contraction of the actomyosin cytoskeleton, generating mechanical traction forces at the sites of adhesion ( 5– 7). Mechanical force plays a critical role in the interactions of cells with their surrounding extracellular matrix (ECM). Together, these findings demonstrate a coordination of biochemical and mechanical signals to regulate cell adhesion and mechanics, and they introduce the use of arrays of mechanically isolated sensors to manipulate and measure the mechanical interactions of cells. Contractility in the unspread cells was rescued by expression of constitutively active RhoA. Cells that were prevented from spreading and flattening against the substrate did not contract in response to stimulation by serum or lysophosphatidic acid, whereas spread cells did. By controlling cell adhesion on these micromechanical sensors, we showed that cell morphology regulates the magnitude of traction force generated by cells. Force increased with size of adhesions for adhesions larger than 1 μm 2, whereas no such correlation existed for smaller adhesions. We report two classes of force-supporting adhesions that exhibit distinct force–size relationships. ![]() ![]() The deflections of the posts occurred independently of neighboring posts and, therefore, directly reported the subcellular distribution of traction forces. Cells attached to, spread across, and deflected multiple posts. By controlling the geometry of the posts, we varied the compliance of the substrate while holding other surface properties constant. We describe an approach to manipulate and measure mechanical interactions between cells and their underlying substrates by using microfabricated arrays of elastomeric, microneedle-like posts. ![]()
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