Interplay of actin nematodynamics and anisotropic tension controls endothelial mechanics

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Abstract

Blood vessels expand and contract actively, while continuously experiencing dynamic external stresses from the blood flow. The mechanical response of the vessel wall is that of a composite material: its mechanical properties depend on its cellular components, which change dynamically as cells respond to external stress. Mapping the relationship between these underlying cellular processes and emergent tissue mechanics is an on-going challenge, in particular in endothelial cells. Here we assess the mechanics and cellular dynamics of an endothelial tube using a microstretcher that mimics the native environment of blood vessels. Characterization of the instantaneous monolayer elasticity reveals a strain-stiffening, actin-dependent and substrate-responsive behaviour. After a physiological pressure increase, the tissue displays a fluid-like expansion, with reorientation of cell shape and actin fibres. We introduce a mechanical model that considers the actin fibres as a network in the nematic phase and couples their dynamics with active and elastic fibre tension. The model accurately describes the response to pressure of endothelial tubes.

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Keywords

Mechanical properties, Materials characterization and Biomaterials

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