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 b asal surface of the endothelium will influence the dynamics of cell/substra te contacts. Such dynamics could be important in the design of synthetic va scular grafts to promote endothelial cell adhesion. To examine whether the initial response of cell/substrate contact sites to flow depends on the mag nitude 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 intern al reflection fluorescence microscopy. Flow induced a rapid fluctuation in the membrane topography, which was reflected in dynamic changes in cell/sub strate contacts. Exposure to flow caused marked changes in contact area. Co ntact movement occurred normal and parallel to the direction of flow. Conta ct 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 cont act center of mass were described in terms of a directed diffusion model. P rior to onset of flow, contact movement was random. Flow induced a signific ant convective component to contact movement for 300-600 s, followed by ree stablishment of diffusive growth and movement of contacts. These results su ggest that fluid stresses are rapidly transmitted from the apical to the ba sal surface of the cell via the cytoskeleton.