טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentLorber Dana
SubjectThe Flow Field in a Stenosis Model of a Coronary Artery and
its Influence on the Permeability of Endothelial
Cells
DepartmentDepartment of Biomedical Engineering
Supervisors Professor Emeritus Eitan Kimmel
Professor Uri Shavit


Abstract

Changes in endothelium permeability are associated with initiation of various pathologies in arteries, especially atherosclerosis.  Here we study the permeability of endothelial cells exposed to different flow regimes in a model of a constricted coronary artery. Bovine Aortic Endothelial Cells (BAEC) were grown to confluence on collagen gel plugs. The plugs were mounted in various locations along a model of coronary stenosis, built with an asymmetric constriction, which provides various flow regimes.  Values of Re number and wall shear stress range from 690 and 0.6 dyne/cm2 at the undisturbed entrance, to 1540 and 17.9 dyne/cm2 at the minimal area of the constricted zone, respectively. After exposure to flow in the tube for an hour, the BAEC were exposed to fluorescent dextran 70 kDa in a diffusion chamber for another hour. Using a mass transfer simulation, the diffusion coefficient of the collagen gel and the permeability of the cell monolayer were derived. In parallel, the details of the flow field were investigated in a similar tube, by a PIV (Particle Image Velocimetry) system. The shear stress near the wall was derived from the velocity measurements. We find that permeability of BAEC monolayer to large molecules increase when the relative unsteadiness shear stress parameter increases. Two versions of this parameter were calculated by dividing the temporal or spatial fluctuations in the wall shear stress by the average wall shear stress. Above some level of unsteadiness, permeability reaches a plateau. Surprisingly, permeability is not affected at all by the average value of the shear stress.