THE MECHANICAL ROLE OF GAGS IN THE AORTIC VALVE
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Aortic valve (AV) dysfunction accounts for ~43% of all valvular disease. There is huge demand for improved prosthetic valves, but to develop such replacements, it is first critical to understand structure-function mechanics of the native valve, to provide insight into how we can replicate these functions. The AV is composed of three layers, namely the fibrosa, spongiosa, and ventricularis, each with a distinct matrix composition and organisation. The central spongiosa is rich in glycosaminoglycans (GAGs) and thought to be critical in facilitating valve flexion and maintaining structural integrity during loading. This study focuses on the effects of GAGs on AV mechanics and micromechanics, comparing native AV leaflets, with leaflets treated with Chondroitinase ABC and hyaluronidase to remove GAGs. GAG digestion had no effect on gross quasi-static tensile properties of leaflets. However, micro-mechanical analysis highlighted the importance of GAGs in modulating stiffness across the width of a leaflet in the radial direction. Native AV leaflets were stiffest free edge region, with stiffness correlating to spongiosa thickness. Digesting GAGs led to homogenous strains across the leaflet, suggesting GAGs may play a critical role in modulating stiffness of AV leaflets in a localized manner, to control AV micro-mechanics for optimal mechanical function.
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