Contribution of Collagen Fiber Undulation to Regional Biomechanical Properties Along Porcine Thoracic Aorta

Abstract

As major extracellular matrix components, elastin, and collagen play crucial roles in regulating the mechanical properties of the aortic wall and, thus, the normal cardiovascular function. The mechanical properties of aorta, known to vary with age and multitude of diseases as well as the proximity to the heart, have been attributed to the variations in the content and architecture of wall constituents. This study is focused on the role of layer-specific collagen undulation in the variation of mechanical properties along the porcine descending thoracic aorta. Planar biaxial tensile tests are performed to characterize the hyperelastic anisotropic mechanical behavior of tissues dissected from four locations along the thoracic aorta. Multiphoton microscopy is used to image the associated regional microstructure. Exponential-based and recruitment-based constitutive models are used to account for the observed mechanical behavior while considering the aortic wall as a composite of two layers with independent properties. An elevated stiffness is observed in distal regions compared to proximal regions of thoracic aorta, consistent with sharper and earlier collagen recruitment estimated for medial and adventitial layers in the models. Multiphoton images further support our prediction that higher stiffness in distal regions is associated with less undulation in collagen fibers. Recruitment-based models further reveal that regardless of the location, collagen in the media is recruited from the onset of stretching, whereas adventitial collagen starts to engage with a delay. A parameter sensitivity analysis is performed to discriminate between the models in terms of the confidence in the estimated model parameters.

Effect of glucose on the biomechanical function of arterial elastin

“…(3). The summation of the squared differences between the estimated and experimental Cauchy stress is minimized (Zeinali-Davarani et al 2013, 2015), and the corresponding material parameters a , b , c and n are obtained. A root-mean-square (RMS) measure of the goodness of fit is calculated as (Zeinali-Davarani et al 2013, 2015): $$\text{RMS}=\sqrt{\frac{1}{\mathit{num}}\sum _1^{\mathit{num}}{\left({\sigma }_L^{\mathrm{italicest}}-{\sigma }_L^{\mathrm{italicexp}}\right)}^2}+\sqrt{\frac{1}{\mathit{num}}\sum _1^{\mathit{num}}{\left({\sigma }_C^{\mathrm{italicest}}-{\sigma }_C^{\mathrm{italicexp}}\right)}^2}$$…”

Cell–matrix interaction during strain-dependent remodelling of simulated collagen networks

“…The cell-network system was stretched by different amounts (5,10,15,20,25,30,35,40,45,50, 55 and 60% strain) before remodelling. The system was stretched uniaxially and incompressibility was enforced.…”

Kinematics of collagen fibers in carotid arteries under tension-inflation loading

“…The measurement of fiber waviness [11,44,53,49] revealed in particular that recruitment, or engagement of collagen fibers, is gradual (unsynchronized among fibers) and starts at a finite strain [23,13]. The process can differ whether the observed vascular region is close or remote from the heart (distal regions vs. proximal regions) [55]. Collagen fiber bundles may also undergo a progressive realignment in response to the application of a macroscopic deformation [1,30,11,13,31].…”