Morphological and Functional Flow-Induced Response of Endothelial Cells and Adhesive properties of Leukocytes in 3D Stenotic Models

Abstract

Endothelial cell dysfunction in response to hemodynamic forces is believed to be a cause of focal atherosclerosis. Flow in stenotic vessels creates complex spatial wall shear stress (WSS) gradients which may alter endothelial cell function and promote adhesion of inflammatory cells. In vitro studies have generally used unrealistic geometries, which cannot reproduce the complexity of physiological hemodynamics. We have developed a three dimensional asymmetric stenosis cell culture model to better study the interaction of endothelial cells with blood components. Human abdominal aortic endothelial cells (ECs) were exposed to steady physiological flows in our models. The adhesive properties of human promyelocytic cells (NB4) following exposure to all-trans-retinoic acid (ATRA) on ECs, were studied. Cells subjected to one dimensional flow aligned in flow direction and had a spindle-like shape when compared to static controls. EC morphology differed in the spatial WSS gradient regions, being randomly oriented and of cobblestone shape. Tumor necrosis factor α stimulation (TNF-α) increased significantly the expression of intercellular adhesion molecule (ICAM-1) and vascular cell adhesion molecule (VCAM-1) on ECs as observed by confocal microscopy and western blots. These cell adhesion molecules are known to be involved in inflammation and upregulated under the control of transcription factor nuclear factor κB (NF-κB). Under static conditions, NB4 cells adhered to a greater extent than under flow, with decreased adhesion observed with increasing flowrate. Regionally, cells under flow adhered more in the low wall shear stress recirculation region distal to the stenosis than in the one dimensional flow inlet region. At the proximal shoulder regions, greater adhesion was noticed although this was not significant. This suggests an important shear mediated role of neutrophil-endothelial interactions in the progression of atherosclerosis. Moreover, the regional response to complex hemodynamics may play an important role in plaque stability.