Structure, Mechanical Properties, and Mechanics of Intracranial Saccular Aneurysms

Biomechanics of the extracellular matrix in arteries determines their macroscopic mechanical behavior. In particular, the distribution of collagen fibers and bundles plays a significant role. Experimental data showed that in most arterial walls there are preferred fiber directions. However, the realignment of collagen fibers during tissue deformation is still controversial: whilst authors claim that fibers should undergo affine deformations, others showed the contrary. In order to have an insight about this important question of affine deformations at the microscopic scale, we measured the realignment of collagen fibers in the adventitia layer of carotid arteries using multiphoton microscopy combined with an unprecedented Fourier based method. We compared the realignment for two types of macroscopic loading applied on arterial segments: axial tension under constant pressure (scenario 1) and inflation under constant axial length (scenario 2). Results showed that, although the tissue underwent macroscopic stretches beyond 1.5 in the circumferential direction, fiber directions remained unchanged during scenario 2 loading. Conversely, fibers strongly realigned along the axis direction for scenario 1 loading. In both cases, the motion of collagen fibers did not satisfy affine deformations, with a significant difference between both cases: affine predictions strongly under-estimated fiber reorientations in uniaxial tension and over-estimated fiber reorientations during inflation at constant length. Finally, we explained this specific kinematics of collagen fibers by the complex tension-compression interactions between very stiff collagen fibers and compliant surrounding proteins. A tensegrity representation of the extracellular matrix in the adventitia taking into account these interactions was proposed to model the motion of collagen fibers during tissue deformation.

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“…Eventually, its remodeling under pathological situations such as aneurysms may degrade this load bearing function [27].…”

Section: Introductionmentioning

confidence: 99%

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

Krasny

Magoariec

Morin

et al. 2018

Journal of the Mechanical Behavior of Biomedical Materials

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“…On the other hand, if the stress-driven remodeling for some reason does not work properly, larger stresses can be produced. This kind of qualitative speculations goes in the same direction of the arguments provided by Humphrey and Canham (2000), who discriminate among several possible mechanisms for the rupture of cerebral aneurysms and finally point the attention on the remodeling process.…”

Section: Final Remarksmentioning

confidence: 90%

Stress-modulated remodeling of a non-homogeneous body

Ambrosi

Guillou

Martino

2007

Biomech Model Mechanobiol

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Many soft tissues, and arteries in primis, exhibit residual stress after unloading, a characteristic related to the ability to self-organize their own constituents (cells and extracellular matrix proteins). This behavior can be theoretically predicted in a continuum mechanics framework assuming that the body self-remodels toward a homeostatic stress state. Open questions concern the characteristics of a stationary grown state, as dictated by the mechanical properties of the material and by the specific external load. In this paper, we illustrate a mathematical framework and we perform numerical simulations for the remodeling of a two-dimensional (axisymmetric) nonlinear elastic cylinder. In particular, we address the stress-modulated remodeling of the cylinder wall when local variations in the mechanical properties of the material occur. Our main result is that, as in one spatial dimension, the tendency of the system to homeostasis generates, thanks to the remodeling process, a residual stress that homogenizes the tension in the body under load. Possible physiological implications of this result are discussed in the final section.

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“…Variations of the tissue stretch and the recruitment stretch are considered to be independent of each other, while the variations of collagen stretch λ c , collagen density n c and collagen stressτ f can be found successively from (43) 2 , (43) 1 and (43) 3 as…”

Section: The Unknowns Here Are λ(T) λ C (T) λ Rec (T) and N C (T)mentioning

confidence: 99%

“…This is associated with serious medical complications and even death. Little is known about why aneurysms appear, how they grow, and what the criteria for their rupture are [3].…”

mentioning

confidence: 99%

Stability against dynamic remodeling of an arterial tissue

et al. 2009

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Geometry and structure of the arterial wall are maintained through continuous growth and remodeling (G&R). To understand these processes, mathematical models have been proposed in which the outcome of G&R depends on a mechanical stimulus through evolution equations. Rate parameters in these equations cannot be determined easily from experimental data. Assuming that the healthy artery is stable against remodeling, a physiologically acceptable range for the two rate parameters in the framework of an existing model of arterial G&R is determined here. The model is explicitly evaluated for the example of a cylindrical blood vessel, both thick-walled and thin-walled. For the thin-walled vessel a criterion for stability against remodeling is derived by means of a linear stability approach, and is expressed in terms of the ratio of the rates of remodeling parameters. It is shown that this criterion is equivalent to the condition that the physiological healthy state of the artery can be reached, implying that if the healthy state exists then it is stable. Explicit numerical results are presented for a typical cerebral artery and an abdominal aorta.

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Structure, Mechanical Properties, and Mechanics of Intracranial Saccular Aneurysms

Cited by 61 publications

References 84 publications

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

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

Stress-modulated remodeling of a non-homogeneous body

Stability against dynamic remodeling of an arterial tissue

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