DYNAMICS OF FLOW-DEPENDENT ARTERIAL PERMEABILITY

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DESCRIPTION (provided by applicant): The overall objective of this research is to understand how hemodynamic stress in vivo affects the uptake of macromolecules by the arterial wall and the accompanying vascular inflammatory response. The interest in macromolecular transport and inflammation is prompted by their importance in the genesis and development of atherosclerosis. A primary hypothesis of this research is that vascular endothelial function is critically influenced by changes in hemodynamic stress. This is examined in two contexts: the adaptive endothelial response to diurnal variations in local shear stress, and the sensitivity of the cells to the harmonic content of the shear stress waveform. It is hypothesized that both the adaptive response and chronic exposure to shear waveforms with high harmonic content are associated with decreases in the barrier function of the endothelium and the expression of inflammatory mediators. The research plan includes two series of animal experiments, and studies of cultured endothelial cells in laminar flow chambers. In baseline experiments, the spatial variation of macromolecular permeability in the coronary (CA) and external iliac arteries (EIA) of swine will be measured using photographic densitometry of Evans Blue dye-albumin complex. The permeability distribution in the CA will be correlated on a site-by-site basis against measures of wall shear stress in the same vessel; the latter will be obtained from flow simulations in computational regions derived from injection casts of the arteries. In shunt experiments, the flow and shear stress in one EIA will be raised by arteriovenous shunting, while the other artery serves as a control; the dependence of albumin uptake on the duration and magnitude of the increase will be assessed. In both series, fixed tissue and unfixed endothelial cells will be recovered, and endothelial monolayer organization, protein distribution and levels, and gene expression will be measured. In the baseline experiments, these data will be related to local shear and shear waveform, and the responses of the CA and EIA will be compared. In the shunt experiments, they will be used to identify the molecular process accompanying adaptation. Flow chamber experiments will expose cultured porcine arterial endothelial cells to flows that replicate selected components of the in vivo flow environment, to isolate their contributions to the in vivo response. The influence of hypercholesterolemia on significant responses found in the normolipemic animals will be examined.