Regional,species,and age related variations in the mechanical properties of arteries 1

Abstract

Changes in passive arterial wall mechanical properties have been correlated with connective tissue composition during growth and development. These results indicate that passive arterial wall mechanics are determined in part by a) the total connective tissue content (collagen and elastin); b) the ratio of collagen to elastin; and c) the “concentration” of connective tissue in extracellular space. Studies of the mechanics and composition of arteries from different anatomical sites indicate that the low and high strain mechanics of these vessels correlates well with their elastin and collagen content, respectively. Differences in mechanics at moderate values of strain can be explained on the basis of differences in the details of the recruitment of collagen fibers to support wall load with increasing strain in different arteries. Differences in the mechanics of carotid arteries from different species at high and low strain suggest that values of elastin and collagen elastic moduli may vary with amino acid composition, for example. Studies of stiffness during arterial smooth muscle activation (series elasticity, SE) in arteries from different anatomical locations revealed no correlation between values of SE and connective tissue composition. However, the results of these studies indicate that arteries with the stiffest SE had the most effective contractile apparatus producing relatively larger constriction responses for a given active stress response compared to other muscles. Smaller arteries from the same vascular bed exhibit similar characteristics with no differences in SE. The more effective contractile apparatus in this case is probably the result of a relatively larger wall thickness in the case of smaller arteries. Treatment of arteries with collagenase produces reductions in active stress development which parallel collagen removal. This suggests a role of collagen in the intercellular coupling of cellular force development. Thus, passive wall elements play a variety of roles in the arterial wall by contributing to both active and passive properties.