Individual and combined effects of shear stress magnitude and spatial gradient on endothelial cell gene expression

The apparent tendency of atherosclerotic lesions to form in complex blood flow environments has led to many theories regarding the importance of hemodynamic forces in endothelium-mediated atherosusceptibility. The effects of shear stress magnitude and spatial shear stress gradient on endothelial cell gene expression in vitro were examined in this study. Converging-width flow channels were designed to impose physiological ranges of shear stress gradient and magnitude on porcine aortic endothelial cells, and real-time quantitative PCR was performed to evaluate their expression of five genes of interest. Although vascular cell adhesion molecule-1 expression was insensitive to either variable, each of the remaining genes exhibited a unique dependence on shear stress magnitude and gradient. Endothelial nitric oxide synthase showed a strong positive dependence on magnitude but was insensitive to gradient. The expression of c-jun was weakly correlated with magnitude and gradient, without an interaction effect. Monocyte chemoattractant protein-1 expression varied inversely with gradient and also depended on the interaction of gradient with magnitude. Intercellular adhesion molecule-1 expression also exhibited an interaction effect, and increased with shear magnitude. These results support the notion that vascular endothelial cells are able to sense shear gradient and magnitude independently.