Effects of fluid shear stress on occludin production of endothelial cells

Endothelial cells (ECs) line the innermost layer of blood vessels and act as a barrier between the blood and sub-endothelial tissues. Wall shear stress (WSS), has been found to directly alter morphology and biochemical concentrations of ECs. Previous studies have demonstrated the relationship of occludin expression to endothelial layer permeability; but limited studies have been performed to investigate the relationship between prolonged exposure to shear stress and occludin. 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. The cells were then immunofluorescently stained for occludin, and photomicrographs were collected and analyzed to measure changes in expression.; Results have shown that when compared to static cultures, occludin levels of ECs exposed to shear stress was down regulated and the occludin diffused in the cell membrane. ECs exposed to physiologically high shear stress (30 dynes/cm2) are slightly down regulated when compared to low (10 dynes/cm2) and normal (20 dynes/cm2) physiological shear. The decrease in occludin expression caused by changes in the local shear stress could be crucial in the pathogenesis of cardiovascular diseases, such as intimal hyperplasia.