Short-term cell/substrate contact dynamics of subconfluent endothelial cells following exposure to laminar flow.

The manner in which fluid stresses are transmitted from the apical to the basal surface of the endothelium will influence the dynamics of cell/substrate contacts. Such dynamics could be important in the design of synthetic vascular grafts to promote endothelial cell adhesion. To examine whether the initial response of cell/substrate contact sites to flow depends on the magnitude of the applied shear stress, subconfluent monolayers of endothelial cells were exposed to flow at 10, 20, and 30 dyn cm-2 wall shear stresses for 20 min. Cell/substrate contact sites were visualized with total internal reflection fluorescence microscopy. Flow induced a rapid fluctuation in the membrane topography, which was reflected in dynamic changes in cell/substrate contacts. Exposure to flow caused marked changes in contact area. Contact movement occurred normal and parallel to the direction of flow. Contact sites demonstrated significant variability in contact area at 30 dyn cm-2 during the experiment but no significant movement of the contact sites in flow direction after 20 min of flow. Mean square displacements of the contact center of mass were described in terms of a directed diffusion model. Prior to onset of flow, contact movement was random. Flow induced a significant convective component to contact movement for 300-600 s, followed by reestablishment of diffusive growth and movement of contacts. These results suggest that fluid stresses are rapidly transmitted from the apical to the basal surface of the cell via the cytoskeleton.