Microstructural and mechanical characterization of the layers of human descending thoracic aortas

Amabili, Marco; Asgari, Meisam; Breslavsky, Ivan D.; Franchini, Giulio; Giovanniello, Francesco; Holzapfel, Gerhard

doi:10.1016/j.actbio.2021.07.036

Cited by 53 publications

(42 citation statements)

References 44 publications

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“…The passive (i.e., without VSM activation) quasistatic mechanical properties of the intact wall of the human aorta and its three individual layers have been extensively investigated experimentally. In particular, uniaxial extension tests were carried out on strips (cut in the circumferential and longitudinal directions) from the intact wall or separated layers ( 6 – 9 ), and biaxial tests on squares and cruciform samples of aortic tissue ( 10 , 11 ) were conducted. The microstructure of the collagen and elastin fiber distributions in the three layers was also examined in detail using second-harmonic generation and two-photon excited fluorescence microscopy ( 9 , 10 , 12 ).…”

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confidence: 99%

“…In particular, uniaxial extension tests were carried out on strips (cut in the circumferential and longitudinal directions) from the intact wall or separated layers ( 6 – 9 ), and biaxial tests on squares and cruciform samples of aortic tissue ( 10 , 11 ) were conducted. The microstructure of the collagen and elastin fiber distributions in the three layers was also examined in detail using second-harmonic generation and two-photon excited fluorescence microscopy ( 9 , 10 , 12 ). Along with the progress of experiments, advanced structure-based material models have also been refined.…”

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confidence: 99%

“…Viscoelastic models have been developed ( 18 , 19 ), but they can only partially describe the experimental results. Experimental data show that the aorta stiffens with increasing age ( 8 , 9 , 11 ), which favors hypertension ( 20 ).…”

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confidence: 99%

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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%

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confidence: 99%

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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 mechanical behavior and structural architectures of soft fibrous tissues are extensively studied in specific tissues (Fratzl and Zizak, 1997;Schulze-Bauer et al, 2002;Holzapfel et al, 2005;Sommer et al, 2009;Yang et al, 2015;Niestrawska et al, 2016;Holzapfel and Ogden, 2018;Frank et al, 2019;Kramer et al, 2019), including the mechanical role of the tissue constituents using enzymatic digestion (Basalo et al, 2004;Barbir et al, 2010;Isaacs et al, 2014). Recently, new techniques such as multiphoton microscopy, Second-harmonic generation (SHG), and Smallangle X-ray scattering (SAXS) were used for in situ multi-scale examinations of tissues under load (Bancelin et al, 2015;Yang et al, 2015;Niestrawska et al, 2016;Lynch et al, 2017;Pissarenko et al, 2019;Amabili et al, 2021). These techniques provide valuable data regarding the structure-function relationship in different tissues and how the entangled mechanical mechanisms work simultaneously on different scales.…”

Section: Mechanical Mechanismsmentioning

confidence: 99%

“…Spatial location and gradual tissue changes also affect this parameter. In addition, fiber volume fraction can be measured in tissues like skin and vessels using diverse imaging techniques (Rezakhaniha et al, 2012;Niestrawska et al, 2016;Pissarenko et al, 2019;Amabili et al, 2021).…”

Section: Fiber Volume Fractionmentioning

confidence: 99%

Structural Mechanisms in Soft Fibrous Tissues: A Review

Sharabi

2022

Front. Mater.

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Through years of evolution, biological soft fibrous tissues have developed remarkable functional properties, unique hierarchical architectures, and -most notably, an unparalleled and extremely efficient deformation ability. Whereas the structure-function relationship is well-studied in natural hard materials, soft materials are not getting similar attention, despite their high prevalence in nature. These soft materials are usually constructed as fiber-reinforced composites consisting of diverse structural motifs that result in an overall unique mechanical behavior with large deformations. Biomimetics of their mechanical behavior is currently a significant bioengineering challenge. The unique properties of soft fibrous tissues stem from their structural complexity, which, unfortunately, also hinders our ability to generate adequate synthetic analogs, such that autografts remain the “gold standard” materials for soft-tissue repair and replacement. This review seeks to understand the structural and deformation mechanisms of soft collagenous tissues, with a particular emphasis on tendon and ligaments, the annulus fibrosus (AF) in the intervertebral disc (IVD), skin, and blood vessels. We examined and compared different mechanical and structural motifs in these different tissue types, which are subjected to complex and varied mechanical loads, to isolate the mechanisms of their deformation behavior. Herein, we focused on their composite structure from a perspective of the different building blocks, architecture, crimping patterns, fiber orientation, organization and their structure-function relationship. In the second part of the review, we presented engineered soft composite applications that used these structural motifs to mimic the structural and mechanical behavior of soft fibrous tissues. Moreover, we demonstrated new methodologies and materials that use biomimetic principles as a guide. These novel architectural materials have tailor-designed J-shaped large deformations behavior. Structural motifs in soft composites hold valuable insights that could be exploited to generate the next generation of materials. They actually have a two-fold effect: 1) to get a better understanding of the complex structure-function relationship in a simple material system using reverse biomimetics and 2) to develop new and efficient materials. These materials could revolutionize the future tailor-designed soft composite materials together with various soft-tissue repair and replacement applications that will be mechanically biocompatible with the full range of native tissue behaviors.

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Mechanical Characterization of Collagen Hydrogels by Quasistatic Uniaxial Tensile Experiments

Kim

Lee

et al. 2023

Adv Eng Mater

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Collagen serves as an essential structural material in the human body. Despite the complex mechanical conditions surrounding the collagen hydrogels, previous studies mostly focus on analyzing the mechanical behavior under dynamically‐varying compressive or shear loads, but the tensile properties at the quasi‐static time scale have been relatively less studied. This work aims to investigate the quasi‐static tensile behavior of reconstituted collagen hydrogels under uniaxial tensile stresses. The evolution of the collagen fiber network structures with straining was visually observed using the confocal microscope equipped with the tensile strain actuator. While the unfolding of the initially‐undulated fibers accommodates the early stage strains, the deformation mechanism continuously changes to the stretching of fibers through the network alignment to the tensile direction. This transition commences with the buckling of a fiber lying transverse to the loading direction, which otherwise locks the rotation of adjacent fibers.This article is protected by copyright. All rights reserved.

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Microstructural and mechanical characterization of the layers of human descending thoracic aortas

Cited by 53 publications

References 44 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

Structural Mechanisms in Soft Fibrous Tissues: A Review

Mechanical Characterization of Collagen Hydrogels by Quasistatic Uniaxial Tensile Experiments

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