OSCILLATORY SHEAR-STRESS AND HYDROSTATIC-PRESSURE MODULATE CELL-MATRIX ATTACHMENT PROTEINS IN CULTURED ENDOTHELIAL-CELLS

Endothelial cells (ECs) may behave as hemodynamic sensors, translating mechanical information from the blood flow into biochemical signals, which may then be transmitted to underlying smooth muscle cells. The e xtracellular matrix (ECM), which provides adherence and integrity for the endothelium, may serve an important signaling function in vascular diseases such as atherogenesis, which has been shown to be promoted b y low and oscillating shear stresses. In this study, confluent bovine aortic ECs (BAECs) were exposed to an oscillatory shear stress or to a hydrostatic pressure of 40 mmHg for time periods of 12 to 48 h. Paral lel control cultures were maintained in static condition. Although ECs exposed to hydrostatic pressure or to oscillatory flow had a polygona l morphology similar to that of control cultures, these cells possesse d more numerous central stress fibers and exhibited a partial loss of peripheral bands of actin, in comparison to static cells. In EC cultur es exposed to oscillatory flow or hydrostatic pressure, extracellular fibronectin (Fn) fibrils were more numerous than in static cultures. C oncomitantly, a dramatic clustering of alpha(5) beta(1) Fn receptors a nd of the focal contact-associated proteins vinculin and talin occurre d. Laminin(Ln) and collagen type IV formed a network of thin fibrils i n static cultures, which condensed into thicker fibers when BAECs were exposed to oscillatory shear stress or hydrostatic pressure. The ECM- associated levels of Fn and Ln were found to be from 1.5- to 5-fold gr eater in cultures exposed to oscillatory shear stress or pressure for 12 and 48 h, than in static cultures. The changes in the organization and composition of ECM and focal contacts reported here suggest that E Cs exposed to oscillatory shear stress or hydrostatic pressure may hav e different functional characteristics from cells in static culture, e ven though ECs in either environment exhibit a similar morphology.