A structural constitutive model considering angular dispersion and waviness of collagen fibres of rabbit facial veins

Aristotelis Agianniotis,Nikos Stergiopulos,Rana Rezakhaniha

doi:10.1186/1475-925x-10-18

Aristotelis Agianniotis, Nikos Stergiopulos + Show 1 more

Open Access

https://doi.org/10.1186/1475-925x-10-18

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Abstract

BackgroundStructural constitutive models of vascular wall integrate information on composition and structural arrangements of tissue. In blood vessels, collagen fibres are arranged in coiled and wavy bundles and the individual collagen fibres have a deviation from their mean orientation. A complete structural constitutive model for vascular wall should incorporate both waviness and orientational distribution of fibres. We have previously developed a model, for passive properties of vascular wall, which considers the waviness of collagen fibres. However, to our knowledge there is no structural model of vascular wall which integrates both these features.MethodsIn this study, we have suggested a structural strain energy function that incorporates not only the waviness but also the angular dispersion of fibres. We studied the effect of parameters related to the orientational distribution on macro-mechanical behaviour of tissue during inflation-extension tests. The model was further applied on experimental data from rabbit facial veins.ResultsOur parametric study showed that the model is less sensitive to the orientational dispersion when fibres are mainly oriented circumferentially. The macro-mechanical response is less sensitive to changes in the mean orientation when fibres are more dispersed. The model accurately fitted the experimental data of veins, while not improving the quality of the fit compared to the model without dispersion. Our results showed that the orientational dispersion of collagen fibres could be compensated by a less abrupt and shifted to higher strain collagen engagement pattern. This should be considered when the model is fitted to experimental data and model parameters are used to study structural modifications of collagen fibre network in physiology and disease.ConclusionsThe presented model incorporates structural features related to waviness and orientational distribution of collagen fibres and thus offers possibilities to better understand the relation between structure and function in the vascular wall. Also, the model can be used to further study mechanically induced collagen remodelling in vascular tissue in health and disease.

Highlights

Structural constitutive models of vascular wall integrate information on composition and structural arrangements of tissue
Collagen fibres appear in coiled and wavy bundles in their unloaded state [14,15] and the individual collagen fibres have a deviation from their mean orientations [16,17]
To formulate the strain energy function and in the absence of vascular tone, we considered only passive properties of the vascular wall and separated our constituent-based strain energy function into two parts representing the elastin and collagen components: Ψ passive = felast Ψ elast + fcollΨ coll where felast and fcoll are the fractions of wall cross-section area composed of elastin and collagen, and Ψelast and Ψcoll represent the SEF for the network of elastin and collagen fibres, respectively

Summary

Introduction

Structural constitutive models of vascular wall integrate information on composition and structural arrangements of tissue. Collagen fibres are arranged in coiled and wavy bundles and the individual collagen fibres have a deviation from their mean orientation. Structural constitutive models, in particular, attempt to integrate information on composition and structural arrangements of tissue to avoid ambiguities in material characterization. In this way, they offer an insight into the function, structure and mechanics of the principal wall components i.e. elastin, collagen and vascular smooth muscle cells. Collagen fibres appear in coiled and wavy bundles in their unloaded state [14,15] and the individual collagen fibres have a deviation from their mean orientations [16,17]. A complete structural constitutive model for vascular collagen should incorporate both waviness and orientational distribution of fibres

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