Adherent cells are known to exert traction forces to adhere to their extracellular matrix at focal adhesions, where integrins interact with the extracellular matrix and mediate various cellular signals. Therefore, it is hypothesized that extracellular matrix-mediated integrin expression may modulate cellular traction forces, resulted in alterations in cell physiology. In this study, to test the hypothesis, traction force measurements are performed on bovine thoracic smooth muscle cells using a polydimethylsiloxane-based micropillar substrate coated with different types of extracellular matrix. The top of the micropillars was selectively coated with fibronectin (FN), vitronectin (VN), and type I collagen (COL I) at 30 and 50 mu g/ml and cells were plated on the extracellular matrix-coated micropillars. For FN and VN, the cells have several spikes at the cell periphery, whereas, for COL 1, the cell expresses relatively oval shape. At 30 mu g/ml, traction forces were 5.5 +/- 0.6, 5.8 +/- 1.3 and 8.5 +/- 2.2 nN for FN, VN, COL I, respectively. At 50 mu g/ml, traction forces significantly increased compared to 30 mu g/ml and were 12.4 +/- 6.8, 13.5 +/- 4.0 and 18.1 +/- 4.7 nN for FN, VN, COL I, respectively. These results indicate that extracellular matrix may specifically modulate integrin expression followed by development of actin stress fibers, possibly leading to changes in traction forces.
