Correlation of endothelial cell shape and wall shear stress in a stenosed dog aorta.

Abstract

The pattern of endothelial geometry at various locations along stenosed dog aortas was examined. This was done to test the hypotheses that the shape of an endothelial cell is related to the local wall shear stress associated with the flowing blood and that alterations in hemodynamics, produced by vascular geometrical changes, influence endothelial cell geometry. Aortic stenosis with a reduction of 71% of the cross-sectional area was produced. The animals were sacrificed 12 weeks later, and the endothelial cell geometry and orientation were studied using the vascular casting technique and a computerized analysis to determine cell area and shape index. The regions of the stenosis examined were those known to experience different hemodynamic conditions. The value of the shape index was found to fall rapidly in the convergent region of the stenosis and to increase suddenly in the divergent region, eventually returning to the prestenotic value at a more distal site. Using a model of a stenosis made from a vascular cast, laser Doppler anemometry was applied to measure velocity profiles and to estimate the local wall shear stress in a stenosed aorta. It is shown that the shape index distribution along these stenosed vessels may be correlated with the level of wall shear stress, with more elongated cells occurring in regions of higher shear stress. (Arteriosclerosis 6:220-229, March/April 1986) T he evidence for the involvement of fluid dynamics in the atherosclerotic process centers primarily on the pattern of the disease.1 " 3 It is often regions of arterial branching and sharp curvature that have the greatest predilection for the development of atherosclerosis. These are also regions where the flow will assume unusual characteristics or at least deviate from what otherwise might be considered a well-behaved arterial flow. The indictment provided by this indirect evidence, particularly as it relates to the bifurcations and geometrical contortions of the arterial vasculature, presently motivates much of the interest in arterial fluid dynamics.It has been suggested that vascular geometry may affect the atherogenic process through its influence on the hemodynamic environment to which the intima is exposed. 4 ' 5 Under such a hypothesis, whatever affects vascular geometry would alter the local detailed flow characteristics and correspondingly influence endothelial morphology and function. Our interest in hemodynamic Received November 5,1984; revision accepted November 12, 1985. forces, in particular arterial wall shear stress, stems from the belief that it is through this hemodynamically imposed frictional force that a fluid mechanic effect on the endothelium becomes manifest. In this context, the topic of interest is the influence of hemodynamic forces on endothelial morphology, cell function, cell turnover rate, and transendothelial transport, and it is the first of these, endothelial morphology, more specifically, en face cell shape, which is the subject of this investigation.There is a body of accumulating data th...

Computational modeling of coupled blood-wall mass transport of LDL: effects of local wall shear stress

“…The effects of shear stress on endothelial cells have been investigated in various studies. Although there is no study that directly investigates the relationship between shear stress and the fraction of leaky junctions, there have been studies on the effect of shear stress on cell shape (4,17,27), proliferation rate (12, 41), and hydraulic conductivity and permeability (27,28). Levesque et al (17) observed a stenosed dog aorta and correlated the cell shape with levels of shear stress.…”

Vascular Endothelium, Hemodynamic Forces, and Atherogenesis

“…In areas of uniform laminar flow, endothelial cells exhibit an ellipsoidal cell (and nuclear) shape and alignment in the direction of flow, whereas in regions of disturbed flow, this orderly pattern is disrupted. 8,9 In addition, arterial wall remodeling (eg, after experimental surgical coarctation or shunting procedures) appears to depend at least in part on a functionally intact endothelium. 10 Direct evidence that hemodynamic forces can influence endothelial structure and function has come from studies in which cultured endothelial cells have been subjected to defined fluid mechanical forces under well controlled conditions in vitro.…”

Relation of vessel wall shear stress to atherosclerosis progression in human coronary arteries.

“…It has been shown that endothelial cells undergo morphological alterations in response to changes in the degree and orientation of shear stress, with elongated endothelial cells that are located in regions of high shear stress having their long axes aligned parallel to the direction of flow and polygonal endothelial cells in low shear stress regions being aligned in haphazard directions. 46 -47 It has been postulated by Asakura and Karino 22 that these alterations may be responsible for the changes in endothelial cell permeability to atherogenic lipoprotein particles. Yoshizumi et al 48 have recently shown that low shear stress stimulates the expression of endothelin mRNA and the release of endothelin into the culture medium from cultured porcine endothelial cells.…”