Monocytes play a central role in the events that lead to a vulnerable atherosclerotic lesion. The first step in this process, monocyte adhesion, is known to be shear stress dependent through a combination of physical and biological factors. One consequence of the subsequent inflammatory response is local enzymatic degradation that can potentially weaken the plaque and make it more susceptible to fissure from the mechanical stresses associated with arterial blood pressure. Progression of the atherosclerotic lesion to rupture is therefore strongly influenced by a combination of mechanical and fluid dynamic factors. These factors relate to the distributions of shear stress acting on the endothelium and tissue-borne strains experienced by the endothelium and monocytes/macrophages. One objective of this proposal is to gain a better appreciation of these stresses and strains, their magnitude and distribution, through realistic numerical simulation of blood flow and vessel wall deformation. A second objective is to use these numerical results, in conjunction with histological measurements and MR imaging, to establish relationships between the hemodynamics and vessel wall deformation on one hand, and monocyte adhesion/invasion and plaque deterioration on the other. The realism of these calculations will rely upon detailed anatomical and compositional data obtained by MR imaging. The hypotheses listed below will be tested by comparing predictions of numerical simulations to histologic examination of the tissue.
Specific Aim 1. Use MR imaging of vessel anatomy, composition, and velocity profile combined with computational methods of fluid and solid analysis to generate a realistic simulation of flow and deformation in the vicinity of an atherosclerotic lesion.
Specific Aim 2. To test the hypothesis that locations on the lumenal surface exposed to low fluid dynamic shear stress correlate with regions of inflammation and tissue degradation.
Specific Aim 3. To test the hypothesis that sites of inflammation/degradation correlate with regions within the tissue that experience high mechanical strain.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL061794-04
Application #
6390170
Study Section
Special Emphasis Panel (ZHL1-CSR-B (S1))
Program Officer
Wassef, Momtaz K
Project Start
1998-09-30
Project End
2003-03-31
Budget Start
2001-09-01
Budget End
2003-03-31
Support Year
4
Fiscal Year
2001
Total Cost
$204,375
Indirect Cost
Name
Massachusetts Institute of Technology
Department
Biomedical Engineering
Type
Schools of Arts and Sciences
DUNS #
City
Cambridge
State
MA
Country
United States
Zip Code
02139
Younis, H F; Kaazempur-Mofrad, M R; Chan, R C et al. (2004) Hemodynamics and wall mechanics in human carotid bifurcation and its consequences for atherogenesis: investigation of inter-individual variation. Biomech Model Mechanobiol 3:17-32
Dai, Guohao; Kaazempur-Mofrad, Mohammad R; Natarajan, Sripriya et al. (2004) Distinct endothelial phenotypes evoked by arterial waveforms derived from atherosclerosis-susceptible and -resistant regions of human vasculature. Proc Natl Acad Sci U S A 101:14871-6
Kaazempur-Mofrad, M R; Isasi, A G; Younis, H F et al. (2004) Characterization of the atherosclerotic carotid bifurcation using MRI, finite element modeling, and histology. Ann Biomed Eng 32:932-46
Williamson, S D; Lam, Y; Younis, H F et al. (2003) On the sensitivity of wall stresses in diseased arteries to variable material properties. J Biomech Eng 125:147-55
Younis, H F; Kaazempur-Mofrad, M R; Chung, C et al. (2003) Computational analysis of the effects of exercise on hemodynamics in the carotid bifurcation. Ann Biomed Eng 31:995-1006
Yang, J H; Sakamoto, H; Xu, E C et al. (2000) Biomechanical regulation of human monocyte/macrophage molecular function. Am J Pathol 156:1797-804