SUBCELLULAR-DISTRIBUTION OF SHEAR-STRESS AT THE SURFACE OF FLOW-ALIGNED AND NONALIGNED ENDOTHELIAL MONOLAYERS

The stresses acting on the luminal surface of endothelial cells due to shear flow were determined on a subcellular scale. Atomic force micro scopy was used to measure the surface topography of confluent endothel ial monolayers cultured under no-flow conditions or exposed to steady shear stress (12 dyn/cm(2) for 24 h). Flow over these surface geometri es was simulated by computational fluid dynamics, and the distribution of shear stress on the cell surface was calculated. Flow perturbation s due to the undulating surface produced cell-scale variations of shea r stress magnitude and hence large shear stress gradients. Reorganizat ion of the endothelial surface in response to prolonged exposure to st eady flow resulted in significant reductions in the peak shear stresse s and shear stress gradients. From the relationship between surface ge ometry and the resulting shear stress distribution, we have defined a hydrodynamic shape factor that characterizes the three-dimensional mor phological response of endothelial cells to flow. The analysis provide s a complete description of the spatial distribution of stresses on in dividual endothelial cells within a confluent monolayer on a scale rel evant to the study of physical mechanisms of mechano-transduction.