Viscoelasticity of the Vessel Wall: The Role of Collagen and Elastic Fibers

Abstract

The aortic wall contains collagen fibrils, smooth muscle cells, and elastic fibers as the primary load-bearing components. It is well known that the collagen fibrils bear loads in the circumferential direction, whereas elastic fibers provide longitudinal as well as circumferential support. Stiffening of the vessel wall is associated with loss of elastic tissue and increases in the collagen content: however, little is known about the mechanism of vessel wall stiffening with age. The purpose of this review is to attempt to relate structural changes that occur to the collagen and elastic fibers to changes in the viscoelastic behavior that are associated with aging. Analysis of the viscoelastic mechanical properties of collagen fibrils from tendon, skin, and aortic wall suggest that the collagen fibrils of aortic wall are different than those of other tissues. The elastic spring constant of the collacen fibrils in vessel walls is significantly less than that found in tendon, suggesting that the presence of type III collagen in aortic wall increases the flexibility of the collagen fibrils. Furthermore, it is hypothesized that changes in the interface between collagen fibrils, elastic fibers, and smooth muscle during aging and in connective tissue disorders leads to changes in the viscoelasticity of the vessel wall.

FTIR protein secondary structure analysis of human ascending aortic tissues

“…Smooth muscle cells and a rich extracellular matrix, principally composed of collagen and elastin fibers, are the most important components of this layer. These proteins are directly implicated in the aneurismal development and are modified, structurally and quantitatively, during the advent of this aortic pathology [13][14][15].…”

The Plastic Nature of the Vascular Wall: A Continuum of Remodeling Events Contributing to Control of Arteriolar Diameter and Structure

“…For example, aging is associated with an increased deposition of collagens type I and III in blood vessels. This augmented deposition of collagen reduces compliance and expands pulse pressure in the elderly (27,152). In hypertension, sympathetic stimulation and activation of the renin-angiotensin system promotes the production of collagen by vascular smooth muscle cells and fibroblasts, thus contributing to extracellular matrix remodeling of the vascular wall (145,166).…”

“…Angiotensin II, a vasoconstrictor that induces inward eutrophic remodeling of resistance arteries (108), stimulates MMP secretion in isolated vascular smooth muscle cells (29). Given that these cells in the vascular wall are surrounded by multiple extracellular matrix proteins that provide anchoring points and structural support (32,45,127,138,152,171), degradation and subsequent rearrangement of the matrix that surrounds them could have profound and rapid functional consequences on vasoregulation that with progression may lead to a more chronically altered vascular wall structure. Moreover, partial degradation of the extracellular matrix surrounding vascular smooth muscle cells is likely a necessary step for allowing the repositioning of cells during the remodeling process.…”

Congruence of Imaging Estimators and Mechanical Measurements of Viscoelastic Properties of Soft Tissues

“…In practice, the reliable data on soft tissue properties are limited in the literature, although this need is vast. Several groups (Dunn and Silver 1983;Hof 2003;Huang et al 2005;Klein et al 2005;Kuo et al 2001;Lally et al 2004;Provenzano et al 2002;Silver et al 2001;Suki et al 1994;Wu et al 2003) have reported findings on mechanical properties of some soft tissues, but most of their studies were focused on tendons, ligaments, cartilage, skin, muscles, lungs, or arteries, which, to some extent, have active force-generating mechanical properties. In contrast, just a few publications (Arbogast and Margulies 1998;Chen et al 1996;Darvish and Crandall 2001;Krouskop et al 1998;Liu and Bilston 2000;Nasseri et al 2002;Phipps et al 2005aPhipps et al , 2005bSnedeker et al 2005;Yang and Church 2006;Yeh et al 2002) presented quantitative results on the viscoelastic behavior of tissues such as brain, breast, prostate, liver, or kidney.…”