The Response of Human Aortic Endothelial Cells in a Stenotic Hemodynamic Environment: Effect of Duration, Magnitude, and Spatial Gradients in Wall Shear Stress

Abstract

Inflammation plays a key role in the development and stability of coronary plaques. Endothelial cells alter their expression in response to wall shear stress (WSS). Straight/tubular and asymmetric stenosis models were designed to study the localized expression of atheroprone molecules and inflammatory markers due to the presence of the spatial wall shear stress gradients created by an eccentric plaque. The effects of steady wall shear stress duration (0–24 h) and magnitude (4.5–18 dynes/cm2) were analyzed in human abdominal aortic endothelial cells through quantitative real-time polymerase chain reaction (PCR) and immunofluorescence analysis in straight/tubular models. Regional expression was assessed by immunofluorescence and confocal microscopy in stenosis models. Under steady fully developed flow, endothelial cells exhibited a sustained increase in levels of atheroprotective genes with WSS duration and magnitude. The local response in the stenosis model showed that expression of endothelial nitric oxide synthase and Kruppel-like factor 2 is magnitude rather than gradient dependent. A WSS magnitude dependent transient increase in translocation of transcription factor nuclear factor κB was observed. Intercellular adhesion molecule 1, vascular cell adhesion molecule 1, and E-selectin exhibited a sustained increase in protein expression with time. The mRNA levels of these molecules were transiently upregulated and this was followed by a decrease in expression to levels lower than static controls. Regionally, increased inflammatory marker expression was observed in regions of WSS gradients both proximal and distal to the stenosis when compared with the uniform flow regions, whereas the atheroprotective markers were expressed to a greater extent in regions of elevated WSS magnitudes. The results from the straight/tubular model cannot explain the regional variation seen in the stenosis models. This may help explain the localization of inflammatory cells at the shoulders of plaques in vivo.