A fiber matrix model for the filtration through fenestral pores in
a compressible arterial intima.
Huang, Yaqi, Shu Chien, Sheldon Weinbaum.
Department of Mechanical Engineering, David Rumschitzki, Department
of Chemical Engineering, The City College of the City University of
New York, New York, NY 10031, Institute for Biomedical Engineering,
and Departments of AMES-Bioengineering and Medicine, University of
California, San Diego, La Jolla, CA 92093, Department of Mechanical
Engineering, The City College of the City University of New York, New
York, NY 10031
APStracts 3:0426H, 1996.
This paper advances a new hypothesis to explain the changes in
hydraulic conductivity of an intact artery wall with increasing
transmural pressure that Tedgui and Lever [29] and Baldwin et al. [3,
4] have observed experimentally. This hypothesis suggests that the
compaction due to pressure loading of the proteoglycan matrix in the
arterial intima near fenestral pores of the internal elastic lamina
(IEL) leads to a narrowing of the pore entrance area and a large
decrease in the local intrinsic Darcy permeability of the matrix. To
quantitati-vely assess the feasibility of this mechanism, a local
two-dimensional model is proposed to study the filtration flow in the
vicinity of the fenestral pores in a compressible intima and a
related expression is derived for the hydraulic conductivity of the
IEL. Using a heterogenous fiber matrix theory, which includes
proteoglycan and collagen components, we first predict the change in
Darcy perme-ability with intimal thickness Li. The model then
calculates the local velocity profiles and pressure distributions in
the intima and media. The results show that there is a marked non
-linear steepening of the intimal pressure profiles near the fenestral
pores when the intima thins at higher lumen pressures. The predicted
relative change in the resistances of the IEL (with the intima), RI,
and of the media, Rm, as a function of intimal thickness shows that
there is a steep increase in RI/Rm when Li is less than 20 percent of
its unstressed value. The numerical results strongly support the
quantitative feasibility of our hypothesis and also suggest that
intimal compression has a limiting behavior in which the much stiffer
collagen fibrils inhibit further compaction at high pressures after
the proteoglycan matrix is maximally compressed. When used to
calculate an effective IEL hydraulic conductivity for use in the
solution of the large scale intimal flow and convective-diffusion
equations, the model also predicts how different transmural pressures
alter the growth of an intimal HRP spot that derives from a localized
(a single cell's boundary) endothelial leakage. Such a prediction is
amenable to experimental verification.
Received 6 April 1995; accepted in final form 16 September 1996.
APS Manuscript Number H340-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996