Changes in shape and cytoskeletal structure of vascular endothelial cells induced by fluid-imposed shear stress were studied in vivo and in vitro. In in vivo experiments, aortic tissue specimens including the flow dividers of the branching of the left subclavian artery and the aortic intercostal ostium were obtained and their endothelial cell shapes were observed using the scanning electron microscope. It was found that the shape and orientation of endothelial cells were strongly affected by blood flow conditions. In in vitro cell culture experiments, porcine aortic endothelial cells were cultured on glass coverslips and extracellular matrix coated (ECM coated) glass coverslips and exposed to shear stress using a parallel plate flow chamber. When we applied a shear stress of 2 pa for 24 hrs, the rearrangement of F-actin filaments occurred within 3 hrs and preceded the cell shape change in the early stage after shear exposure. The endothelial cells on ECM-coated coverslips exhibited more elongated cell shapes even under no-flow conditions. After exposure to shear stress, the endothelial cells on ECM-coated glass showed more retarded elongation and orientation to the direction of flow than those on no-coated glass, suggesting that the anchorage to the substrate was enhanced by ECMs.
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