Elastin-Dependent Aortic Heart Valve Leaflet Curvature Changes During Cyclic Flexure

Abstract

The progression of calcific aortic valve disease (CAVD) is characterized by extracellular matrix (ECM) remodeling, leading to structural abnormalities and improper valve function. The focus of the present study was to relate aortic valve leaflet axial curvature changes as a function of elastin degradation, which has been associated with CAVD. Circumferential rectangular strips (L × W = 10 × 2.5 mm) of normal and elastin-degraded (via enzymatic digestion) porcine AV leaflets were subjected to cyclic flexure (1 Hz). A significant increase in mean curvature (p < 0.05) was found in elastin-degraded leaflet specimens in comparison to un-degraded controls at both the semi-constrained (50% of maximum flexed state during specimen bending and straightening events) and fully-constrained (maximally-flexed) states. This significance did not occur in all three flexed configurations when measurements were performed using either minimum or maximum curvature. Moreover, the mean curvature increase in the elastin-degraded leaflets was most pronounced at the instance of maximum flexure, compared to un-degraded controls. We conclude that the mean axial curvature metric can detect distinct spatial changes in aortic valve ECM arising from the loss in bulk content and/or structure of elastin, particularly when there is a high degree of tissue bending. Therefore, the instance of maximum leaflet flexure during the cardiac cycle could be targeted for mean curvature measurements and serve as a potential biomarker for elastin degradation in early CAVD remodeling.

Radiofrequency Ablation Alters the Microstructural Organization of Healthy and Enzymatically Digested Porcine Mitral Valves

“…Following elastin digestion, the loss of tissue connectivity causes collagen fibers to lose their undulation as the leaflet enlarges. This suggests a physical coupling between collagen and elastin [40] that endows leaflet tissue with its nonlinear material response. Indeed, comparisons between measured fiber distributions from co-localized SHG and MPF images revealed a correlation between collagen and elastin orientation in control leaflets (Fig.…”

Extracellular matrix-derived materials for tissue engineering and regenerative medicine: A journey from isolation to characterization and application

“…In large arteries such as the aorta, elastin is responsible for the reversible extensibility during the stress-relaxation cycle, while collagen provides the strength and ability to withstand the high pressure in these large elastic arteries [ 23 , 24 ]. Indeed, some cardiovascular pathologies have been associated with elastin dysregulation in these tissues over time, such as calcific aortic valve disease, and congenital supravalvular aortic stenosis [ 23 , 25 ]. Due to all this, elastin is widely used in tissue engineering as a biomaterial [ 26 ].…”

The effect of the fibrocalcific pathological process on aortic valve stenosis in female patients: a finite element study

“…During the early stage of the systolic phase, the pressure distribution is mainly determined by the paravalvular pressure drop across the valve. The collagen remodeling in the spongiosa and ventricularis layers of the leaflet was not taken into account, together with the elastin degradation [3,51].…”