Endothelial cell response and leukocyte adhesion in an asymmetric stenosis model: Role of fluid wall shear stress gradients

The focal nature of atherosclerosis has been associated with complex geometries. The response of endothelial cells to hemodynamics is believed to be linked to atherosclerotic plaque development, progression and rupture. Great advances have been made in our ability to study cellular responses to mechanical forces. Unfortunately, the inability to recreate in vitro the realistic in vivo mechanical stimuli may be obscuring our understanding. In order to determine the mechanistic link between hemodynamics and plaque stability, three dimensional in vitro cell culture models were designed and biomolecular techniques were adapted to analyze endothelial cell function. Dextran was used as a supplement to increase the growth medium viscosity and its effects were characterized. Straight/tubular in vitro models were used to study the acute and long term response of endothelial cells to wall shear stress (WSS) of different magnitude. Anatomically realistic and asymmetric stenosis models were created in order to examine the morphological response of endothelial cells to complex hemodynamic forces. Within the stenosis models, the regional adhesive properties of neutrophils were tested as well as the localized expression of inflammatory molecules. Results show that appropriate time matched dextran containing static controls are required as this additive modified inflammatory marker cell expression both under static and flow conditions in a concentration and time dependent manner. Endothelial cells exposed to wall shear stress altered their morphology depending on the magnitude and duration of exposure. Morphological adaptation was sensitive to the spatial wall shear stress gradients present in both the asymmetric stenosis and the anatomically realistic models. Neutrophil adhesion and inflammatory marker expression differed in the spatial WSS gradient regions of the asymmetric stenosis models. This study highlights the possible role for spatial wall shear stress gradients in the development and progression of atherosclerotic plaques, through the localized analysis of inflammatory markers and neutrophil adhesion.