Collagen Biomechanics in Cerebral Arteries and Bifurcations Assessed by Polarizing Microscopy

Rowe, A.; Finlay, Helen M.; Canham, Peter B.

doi:10.1159/000072831

Cited by 66 publications

(53 citation statements)

References 7 publications

(11 reference statements)

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“…Previous studies suggested that the bifurcation apex may be protected from hemodynamic stresses by a narrow band of densely packed collagen fibers that covers the bifurcation medial pad and provides strength and stiffness to the region. 2,5,21 It was shown using surgically created arterial bifurcations in animals that the acceleration region adjacent to the medial pad was characterized by disrupted internal elastic lamina and loss of endothelium, which is consistent with early-stage IAs. 17 Whereas our simulations showed that the acceleration area grew from 0.38 mm to almost 7 mm with a larger angle, the medial pad was reported to take values between 0.42 mm 2 and 1.40 mm 2 .…”

Section: Discussionmentioning

confidence: 75%

Widening of the basilar bifurcation angle: association with presence of intracranial aneurysm, age, and female sex

Tütüncü¹,

Schimansky²,

Baharoglu³

et al. 2014

JNS

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Object. Arterial bifurcations represent preferred locations for aneurysm formation, especially when they are associated with variations in divider geometry. The authors hypothesized a link between basilar apex aneurysms and basilar bifurcation (a) and vertebrobasilar junction (VBJ) angles.Methods. The a and VBJ angles were measured in 3D MR and rotational angiographic volumes using a coplanar 3-point technique. Angle a was compared between age-matched cohorts in 45 patients with basilar artery (BA) aneurysms, 65 patients with aneurysms in other locations (non-BA), and 103 nonaneurysmal controls. Additional analysis was performed in 273 nonaneurysmal controls. Computational fluid dynamics (CFD) simulations were performed on parametric BA models with increasing angles.Results. Angle a was significantly wider in patients with BA aneurysms (146.7° ± 20.5°) than in those with non-BA aneurysms (111.7° ± 18°) and in controls (103° ± 20.6°) (p < 0.0001), whereas no difference was observed for the VBJ angle. A wider angle a correlated with BA aneurysm neck width but not dome size, which is consistent with CFD results showing a widening of the impingement zone at the bifurcation apex. BA bifurcations hosting even small aneurysms (< 5 mm) had a significantly larger a angle compared with matched controls (p < 0.0001). In nonaneurysmal controls, a increased with age (p < 0.0001), with a threshold effect above 35 years of age and a steeper dependence in females (p = 0.002) than males (p = 0.04).Conclusions. The a angle widens with age during adulthood, especially in females. This angular widening is associated with basilar bifurcation aneurysms and may predispose individuals to aneurysm initiation by diffusing the flow impingement zone away from the protective medial band region of the flow divider. (http://thejns.org/doi/abs/10.3171/2014 key WorDS • vessel morphology • basilar bifurcation • vascular disorders • bifurcation aneurysms • vascular age dependencyAbbreviations used in this paper: AUC = area under the curve; BA = basilar artery; CFD = computational fluid dynamics; IA = intracranial aneurysm; MPR = multiplanar reconstruction; MRA = MR angiography; PCA = posterior cerebral artery; ROC = receiver operating characteristic; VBJ = vertebrobasilar junction; WSS = wall shear stress.

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Section: Discussionmentioning

confidence: 75%

Widening of the basilar bifurcation angle: association with presence of intracranial aneurysm, age, and female sex

Tütüncü¹,

Schimansky²,

Baharoglu³

et al. 2014

JNS

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“…19,20 In qPLM, two parameters related to the birefringent properties of the specimen are determined, independent of polarizer orientation, for each pixel in the acquired images: 19,21 retardance (expressed in nanometers) and theaverage orientation of the polarization axis with the greater index of refraction (the slow axis). qPLM has been used to examine collagen ultra-structure in normal and damaged articular cartilage, [21][22][23] collagen deposition in burn healing, 24 structural changes in myocardial tissue after infarction and regenerative treatments, 25 wall structural integrity of brain arteries, 26 and the paths of white matter tracts in the brain, 27,28 among other applications. To the best of our knowledge, qPLM has never been applied to examine cochlear cross-sections.…”

Section: Introductionmentioning

confidence: 99%

Quantitative polarized light microscopy of unstained mammalian cochlear sections

et al. 2013

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Abstract. Hearing loss is the most common sensory deficit in the world, and most frequently it originates in the inner ear. Yet, the inner ear has been difficult to access for diagnosis because of its small size, delicate nature, complex three-dimensional anatomy, and encasement in the densest bone in the body. Evolving optical methods are promising to afford cellular diagnosis of pathologic changes in the inner ear. To appropriately interpret results from these emerging technologies, it is important to characterize optical properties of cochlear tissues. Here, we focus on that characterization using quantitative polarized light microscopy (qPLM) applied to unstained cochlear sections of the mouse, a common animal model of human hearing loss. We find that the most birefringent cochlear materials are collagen fibrils and myelin. Retardance of the otic capsule, the spiral ligament, and the basilar membrane are substantially higher than that of other cochlear structures. Retardance of the spiral ligament and the basilar membrane decrease from the cochlear base to the apex, compared with the more uniform retardance of other structures. The intricate structural details revealed by qPLM of unstained cochlear sections ex vivo strongly motivate future application of polarization-sensitive optical coherence tomography to human cochlea in vivo.

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“…Most bifurcations of the cerebral vasculature are structurally stable, but a small number develop a weakness that causes the wall to expand outwardly in the region near the flow divider of the branching artery (Austin et al, 1993;MacDonald et al, 2000;Rowe et al, 2003). Some measurements of the macroscopic mechanical properties of cerebral arteries and aneurysms exist (Coulson et al, 2004;Monson et al, 2003Monson et al, , 2005Scott et al, 1972;Steiger, 1990;Tóth et al, 1998Tóth et al, , 2005 and the structural organisation of these tissues is fairly well documented (Canham et al, 1991b(Canham et al, ,a, 1992(Canham et al, , 1996(Canham et al, , 1999Finlay et al, 1991Finlay et al, , 1995Finlay et al, , 1998Hassler, 1972;MacDonald et al, 2000;Rowe et al, 2003;Smith et al, 1981;Whittaker et al, 1988). In the aneurysmal wall, the tunica media and the internal elastic lamina have often disappeared or are severely fragmented (Abruzzo et al, 1998;Sakaki et al, 1997;Stehbens, 1963;Suzuki and Ohara, 1978;Tóth et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

A theoretical model for fibroblast-controlled growth of saccular cerebral aneurysms

Kroon

Holzapfel

2009

Journal of Theoretical Biology

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A new theoretical model for the growth of saccular cerebral aneurysms is proposed by extending the recent constitutive framework of Kroon and Holzapfel (J. Theor. Biol., 247:775-787, 2007). The continuous turnover of collagen is taken to be the driving mechanism in aneurysmal growth. The collagen production rate depends on the magnitude of the cyclic deformation of fibroblasts, caused by the pulsating blood pressure during the cardiac cycle. The volume density of fibroblasts in the aneurysmal tissue is taken to be constant throughout the growth process. The growth model is assessed by considering the inflation of an axisymmetric membranous piece of aneurysmal tissue, with material characteristics representative of a cerebral aneurysm. The diastolic and systolic states of the aneurysm are computed, together with its load-free state. It turns out that the value of collagen pre-stretch, that determines growth speed and stability of the aneurysm, is of pivotal importance. The model is able to predict aneurysms with typical berry-like shapes observed clinically, and the predicted wall stresses correlate well with the experimentally obtained ultimate stresses of this type of tissue. The model predicts that aneurysms should fail when reaching a size of about 1.2-3.6 mm, which is smaller than what has been clinically observed. With some refinements, the model may, however, be used to predict future growth of diagnosed aneurysms.

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Collagen Biomechanics in Cerebral Arteries and Bifurcations Assessed by Polarizing Microscopy

Cited by 66 publications

References 7 publications

Widening of the basilar bifurcation angle: association with presence of intracranial aneurysm, age, and female sex

Widening of the basilar bifurcation angle: association with presence of intracranial aneurysm, age, and female sex

Quantitative polarized light microscopy of unstained mammalian cochlear sections

A theoretical model for fibroblast-controlled growth of saccular cerebral aneurysms

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