Role of smooth muscle activation in the static and dynamic mechanical characterization of human aortas

Abstract

Experimental data and a suitable material model for human aortas with smooth muscle activation are not available in the literature despite the need for developing advanced grafts; the present study closes this gap. Mechanical characterization of human descending thoracic aortas was performed with and without vascular smooth muscle (VSM) activation. Specimens were taken from 13 heart-beating donors. The aortic segments were cooled in Belzer UW solution during transport and tested within a few hours after explantation. VSM activation was achieved through the use of potassium depolarization and noradrenaline as vasoactive agents. In addition to isometric activation experiments, the quasistatic passive and active stress–strain curves were obtained for circumferential and longitudinal strips of the aortic material. This characterization made it possible to create an original mechanical model of the active aortic material that accurately fits the experimental data. The dynamic mechanical characterization was executed using cyclic strain at different frequencies of physiological interest. An initial prestretch, which corresponded to the physiological conditions, was applied before cyclic loading. Dynamic tests made it possible to identify the differences in the viscoelastic behavior of the passive and active tissue. This work illustrates the importance of VSM activation for the static and dynamic mechanical response of human aortas. Most importantly, this study provides material data and a material model for the development of a future generation of active aortic grafts that mimic natural behavior and help regulate blood pressure.

Cardiovascular deconditioning and impact of artificial gravity during 60-day head-down bed rest—Insights from 4D flow cardiac MRI

“…In an ex vivo experiment, the smooth muscle activation was shown to lead to an increase in aortic stiffness (Franchini et al, 2022). It seems in line with spaceflight findings, where a positive relationship has been observed between carotid intima-media thickness and β-stiffness (Arbeille et al, 2016).…”

Disparate biomechanical properties of the aorta in non‐aneurysmal and aneurysmal mice treated with angiotensin II

“…We previously reported that aortic VSMC contraction significantly alters the biomechanical properties of mouse aortic tissue (Leloup et al, 2019 ), which was recently confirmed for tissue specimens from the human descending thoracic aorta (Franchini et al, 2022 ). Aortic biomechanical properties and the role of VSMC contraction in aortic stiffness regulation were also shown to be altered during aging (Amabili et al, 2020 , 2021 ; De Moudt et al, 2022b ).…”

Revealing Layer‐Specific Ultrastructure and Nanomechanics of Fibrillar Collagen in Human Aorta via Atomic Force Microscopy Testing: Implications on Tissue Mechanics at Macroscopic Scale

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