Wall shear stress regulation of occludin expression in human umbilical vein endothelial cells

Previous studies have demonstrated the relationship of occludin expression to endothelial layer permeability; but none have determined the relationship between prolonged exposure to shear stress and occludin expression. The purpose of this study is to determine the effects of varying fluid shear stress on the regulation of occludin in endothelial cells after cell realignment. A flow system, which consisted of four parallel plate flow chambers, was developed in order to simultaneously expose human umbilical vein endothelial cells to 0.3, 10, 20, and 30 dynes/cm² levels of shear stress. A constant flow rate was applied to all flow chambers and shear stress was controlled by varying the viscosities of the flowing media. To date, results have shown that occludin expression is down-regulated, though only by <10% over the entire range, by increases in shear stress magnitude. Occludin expression in the static cultures were also found to be significantly greater than those exposed to shear. These differences show that occludin expression is a shear dependent phenomenon, but not as large a difference was observed as compared to previously reported results for short time exposures.