Viscoelastic characterization of human descending thoracic aortas under cyclic load

Franchini, Giulio; Breslavsky, Ivan D.; Holzapfel, Gerhard; Amabili, Marco

doi:10.1016/j.actbio.2021.05.025

Cited by 45 publications

(47 citation statements)

References 37 publications

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“…The passive dynamic material properties (also referred to as viscoelastic) of the human aortas, on the other hand, are much less studied, even if they are of great importance since the aorta is dynamically loaded by pulsating pressure under physiological conditions. The experiments were performed on a mock circulatory loop under physiological pulsatile pressure and flow ( 3 , 16 ) and on strips of thoracic descending aortas ( 8 , 17 ). Viscoelastic models have been developed ( 18 , 19 ), but they can only partially describe the experimental results.…”

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confidence: 99%

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

Franchini

Breslavsky

Giovanniello

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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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.

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confidence: 99%

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

Franchini

Breslavsky

Giovanniello

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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“…The stiffness of the tissue at large strains is thus rapidly increased up to that of collagen. This explains the nonlinearity of the stress–strain curves (also called J‐shaped curves) [ 47,48 ] observed in tensile tests on several tissues such as longitudinal and circumferential strips of human thoracic aorta, [ 21,22,24,25 ] with the outset of deformation requiring a relatively low applied stress, while much higher stresses needed to impose larger strains. [ 47 ] Upon releasing the applied load at large strains, the tissue minimizes the deformation and returns to its original state.…”

Section: Resultsmentioning

confidence: 99%

“…At macroscopic scale, dynamic mechanical analysis (DMA) is commonly applied to evaluate the response of the material at different deformation rates, which yields the storage and loss moduli. [ 24 ] Such tests yield larger stiffness for the response of biological materials by increasing the deformation rate. At small scale, changing the speed of the AFM cantilever, and thus the speed of pushing the spherical probe into the surface of the sample, reveals viscoelastic effects.…”

Section: Resultsmentioning

confidence: 99%

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

Asgari

Latifi

Giovanniello

et al. 2022

Advanced NanoBiomed Research

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Soft biological tissues are natural biomaterials with structures that have evolved to perform physiological functions, for example, conferring elasticity while preserving the mechanical integrity of arteries. Furthermore, the mechanical properties of the tissue extracellular matrix (ECM) significantly affect cell behavior and organ function. ECM mechanical properties are strongly affected by collagen ultrastructure, and perturbations in collagen networks can cause tissue mechanical failure. It is thus crucial to understand the ultrastructural mechanical properties of soft tissues. Herein, the ultrastructural and nanomechanical properties of arterial tissues are reported. Specifically, maps of aorta tissue stiffness in its three constitutive layers, namely tunica intima, media, and adventitia, are reported. Atomic force microscopy (AFM) with large and ultrasharp tips is used to explore tissue stiffness at two scales. Quasistatic tensile tests are further conducted to understand a potential correspondence between small‐scale mechanical properties obtained via AFM indentation and macroscopic behavior of the tissue at low and large strains. Furthermore, gradients in stiffness across the various layers as well as deformation rate effects are investigated. It is envisioned that the established methodology serves as a tool to investigate the effect of ECM remodeling associated with vascular diseases such as aneurysms and arterial stiffening linked to hypertension.

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“…CT can be used to calculate the CS and LS of the aorta by calculating the displacement, diameter, or area of the aorta. 28 For example, Morrision et al 22 used 4D heart-gated CT to measure the CS of the thoracic aorta in normal subjects. The branch vessels of the aorta were used as anatomical markers to locate the aortic wall.…”

Section: Ctmentioning

confidence: 99%

Evaluation of aortic biomechanics in patients with aortic disease via imaging: A review

Wang

Gong

2021

J of Clinical Ultrasound

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As a bridge between the heart and the arteries, the aorta plays an important role in the cardiovascular system. The morbidity and mortality of aortic disease are extremely high, which is a serious threat to human life. The biomechanical abnormality of the aorta is an important factor of a series of pathological changes in the aortic wall. At present, there are many imaging methods to evaluate the biomechanics of the aorta, which will benefit to the early diagnosis and treatment of aortic disease. In this review, we describe the application of various imaging methods and parameters in aortic disease.

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Viscoelastic characterization of human descending thoracic aortas under cyclic load

Cited by 45 publications

References 37 publications

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

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

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

Evaluation of aortic biomechanics in patients with aortic disease via imaging: A review

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