Surface topography measurement and intracellular stress analysis of cultured endothelial cells exposed to fluid shear stress

Intracellular stress distributions in cultured endothelial cells exposed to fluid shear stress were studied using finite-element analysis, in which cell surface geometries were measured by atomic force microscopy. After applying shear stress, the endothelial cells showed marked elongation and orientation in the flow direction. Finite-element analysis indicated that wall shear stress in the central region around the nucleus was significantly higher than those in the upstream and downstream sides for both control, statically cultured cells, and sheared cells, but the intracellular stress concentrations between the central regions and the other two sides reduced with fluid flow. Fluorescent images showed that stress fibers of F-actin bundles were mainly formed in the central portion of the cells. These results indicate that endothelial cells may change their cytoskeletal structures to increase their stiffness and reduce stress concentrations in the cells.