Effects of elastin degradation and surrounding matrix support on artery stability

Abstract

Tortuous arteries are often associated with aging, hypertension, atherosclerosis, and degenerative vascular diseases, but the mechanisms are poorly understood. Our recent theoretical analysis suggested that mechanical instability (buckling) may lead to tortuous blood vessels. The objectives of this study were to determine the critical pressure of artery buckling and the effects of elastin degradation and surrounding matrix support on the mechanical stability of arteries. The mechanical properties and critical buckling pressures, at which arteries become unstable and deform into tortuous shapes, were determined for a group of five normal arteries using pressurized inflation and buckling tests. Another group of nine porcine arteries were treated with elastase (8 U/ml), and the mechanical stiffness and critical pressure were obtained before and after treatment. The effect of surrounding tissue support was simulated using a gelatin gel. The critical pressures of the five normal arteries were 9.52 kPa (SD 1.53) and 17.10 kPa (SD 5.11) at axial stretch ratios of 1.3 and 1.5, respectively, while model predicted critical pressures were 10.11 kPa (SD 3.12) and 17.86 kPa (SD 5.21), respectively. Elastase treatment significantly reduced the critical buckling pressure (P < 0.01). Arteries with surrounding matrix support buckled into multiple waves at a higher critical pressure. We concluded that artery buckling under luminal pressure can be predicted by a buckling equation. Elastin degradation weakens the arterial wall and reduces the critical pressure, which thus leads to tortuous vessels. These results shed light on the mechanisms of the development of tortuous vessels due to elastin deficiency.

Creating a model of diseased artery damage and failure from healthy porcine aorta

“…Disease and ageing, however, alter the respective compositions, leading to often undesirable changes in function. Ageing has been shown to cause a loss of medial elastin followed by an increase in the stiffer collagen fibres, further stiffened by additional cross-linking, to compensate [8,9,10,11]. This results in the elastin-collagen interaction altering and the stiffer collagen fibres being recruited at smaller deformations, leading to an observed stiffening of the arterial wall.…”

Stability of Carotid Artery Under Steady-State and Pulsatile Blood Flow: A Fluid–Structure Interaction Study

“…Theoretical and experimental studies have shown that artery buckling occurs under both static pressure and pulsatile flow conditions [1,[13][14][15][16][17]. The critical buckling pressure depends on vessel wall dimensions, material properties, axial stretch ratio, and surrounding matrix support [1,3,16,17].…”

“…The critical buckling pressure depends on vessel wall dimensions, material properties, axial stretch ratio, and surrounding matrix support [1,3,16,17]. However, it remains unclear how the buckling behavior of arteries under pulsatile flow differs from the buckling behavior under static pressure or steadystate flow.…”

Evolution and rupture of vulnerable plaques: a review of mechanical effects

“…In Fung, 90 the stretch ratio in rabbit arteries varies from 1.6 in the carotid to 1.4 for the upper abdominal aorta, whereas Fung and Liu 91 showed that the opening angle in normal rats varies from 160° in the ascending aorta and 90° in the arch to 60° in the thoracic region. Details of the use of these parameters for the modeling of the vessel properties are not discussed here, but the reader can refer to Lee et al, 92 Holzapfel et al, 93 or Raghavan et al 94 for additional information on this issue. Concerning the variation of the elastic properties as a function of the load applied (pressure, tension, and flow, for instance), one can refer to Martinez et al 95 and Lee et al 92 In these papers, the authors measure the evolution of the longitudinal and circumferential stretch ratio as a function of internal pressure during an inflation test.…”

“…Details of the use of these parameters for the modeling of the vessel properties are not discussed here, but the reader can refer to Lee et al, 92 Holzapfel et al, 93 or Raghavan et al 94 for additional information on this issue. Concerning the variation of the elastic properties as a function of the load applied (pressure, tension, and flow, for instance), one can refer to Martinez et al 95 and Lee et al 92 In these papers, the authors measure the evolution of the longitudinal and circumferential stretch ratio as a function of internal pressure during an inflation test. This procedure enables them to approximate the stress-strain evolution, characteristic of the elastic properties of a material, by a mathematical hyperelastic model.…”