Heterogeneity of deformation of aortic wall at the microscopic level: Contribution of heterogeneous distribution of collagen fibers in the wall

Abstract

There is growing evidence of heterogeneous distribution of collagen fibers in the aortic wall. To investigate the effects of collagen microstructure on local aortic wall deformation, porcine thoracic aortas were sliced into 100 µm-thick sections perpendicular to their radial direction and stretched biaxially with a laboratory-made tensile tester under a microscope equipped with a birefringence imaging system. Strain tensor components were calculated from fluorescent images of the cell nuclei for each 50 × 50 µm 2 area. Retardance Ret and slow axis azimuth θ were measured as indices of collagen density and fiber direction, respectively. Aortic wall deformation was highly heterogeneous: standard deviations of strains were significantly larger, by 3-5 times, in aortic slices than in homogeneous silicone sheets. A significant negative correlation was found between maximum principal strain and Ret (R = −0.077), and a positive correlation between minimum principal strain direction and θ (R = 0.345). These indicate that the aorta is less distensible in areas with higher collagen density and in the direction of collagen fiber alignment. Microscopic heterogeneity may induce heterogeneous responses of smooth muscle cells and have crucial effects on mechanical homeostasis in the aortic wall.

Magnesium Orotate Influence on Thoracic Aorta in Laboratory Rabbits Receiving Levofloxacin

“…[28]. Образцы аорты кроликов, получавших левофлоксацин, демонстрировали в основном неупругое поведение, характерное для тканей с микроскопической гетерогенностью [29]. При морфометрическом исследовании аорты кроликов, получавших только левофлоксацин, обнаружены фокусы умеренной фрагментации эластических мембран, показано снижение их толщины и относительного содержания в средней оболочке.…”

Repeated High Rate Facet Capsular Stretch at Strains That are Below the Pain Threshold Induces Pain and Spinal Inflammation With Decreased Ligament Strength in the Rat

“…Stiffness of soft tissues has been shown to be positively correlated with collagen fiber realignment [58], suggesting that the decrease in stiffness (Table 1) may be accompanied by collagen fiber disorganization. Disorganized collagen fiber networks in aortic tissue have been shown to produce inhomogeneous local strains [59], As such disorganized local fiber networks in the ligament during a subthreshold loading (in this case during the second FJD) could induce less homogenous strain fields and higher local strains that would directly activate nociceptive fibers in the ligament and could be a mechanism for pain generation. Since collagen realignment is evident in the facet capsule after a single painful exposure but not a single subthreshold exposure [25,40], changes in ligament microstructure may only be induced after a repeated exposure.…”

Biomechanics of aortic wall failure with a focus on dissection and aneurysm: A review

“…Following the protocol reported by Sugita & Matsumoto [135], recently Sugita & Matsumoto [136] performed biaxial extension tests on thinly sliced porcine thoracic aortas with a reduced cross section in the center and reported a heterogeneous deformation field in terms of strains similar to Sugita & Matsumoto [134]. Strain distribution and the collagen realignment were similar between the crack initiation sites and the remaining tissue sample, in contrast to the idea behind the maximum principal strain failure criterion.…”