The Relationship Between Intimal Thickening and the Hemodynamic Environment of the Arterial Wall
The time-varying shear rates at the walls of human arteries are estimated from laser Doppler anemometer measurements in flow-through casts of human aortic and coronary bifurcations, through which physiologically realistic, fluid dynamically scaled, pulsatile flows are passed. These shear rates are then correlated against morphological measurements at corresponding sites in the vessels from which the casts had been made. These correlations suggest that the dependence of intimai thickening rate on mural shear is complex and changes over time; in particular, the intimai thickness at sites exposed to high or more unidirectional shear stresses increases quickly to a modest value, growing slowly thereafter, while the thickness at sites exposed to low or more oscillatory shears rises more slowly but, after time, reaches higher values. This behavior can be the result of competing shear-dependent processes. This explanation of the experimental results is supported by a mathematical model of intimai thickening that incorporates a selection of the biological processes that take place in the arterial wall as it responds to its hemodynamic environment. A best parsimonious fit to the data is obtained when, at sites exposed to relatively high shear, smooth muscle cells accumulate more rapidly in the intima but express extracellular matrix at a slower rate.
KeywordsShear Rate Pulsatile Flow Oscillatory Shear Intimal Thickness Aortic Bifurcation
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