The network of collagen fibers in the aortic valve leaflet is

The network of collagen fibers in the aortic valve leaflet is thought to play an important role in the strength and durability of the valve. pattern influences the Bevirimat shape of the closed valve. We observed a curved or bent pattern with collagen materials angled downward from your commissures toward the center of the leaflet to form a pattern that is concave toward the leaflet free edge. Simulations showed that these curved dietary fiber trajectories straighten under pressure load leading to functionally important changes in closed valve shape. Relative to a pattern of right collagen materials running parallel to the leaflet free Bevirimat edge the concave pattern of curved materials produces a closed valve Bevirimat having a 40% increase in central leaflet coaptation elevation and with reduced leaflet billow producing a even more physiological shut valve form. Furthermore simulations display that these adjustments in packed Bevirimat leaflet shape reveal adjustments in leaflet curvature because of modulation of in-plane membrane tension resulting from styling from the curved fibres. This effect seems to play a significant role in regular valve function and could have essential implications for the look of prosthetic and tissues engineered replacing valves. of two factors and is stage (is normally a weighting function and it is a weighting community around in the still left half from the leaflet and positive in the proper half from the leaflet while for mesh components in the low 25% from the leaflet the neighborhood fibers angle is used as zero levels (Fig. 3). The packed state from the valve was simulated for 9 different meshes matching to collagen fiber angle boosts over the number of simulated sides (Fig. 6). Primary strains in the leaflets are visualized by superimposing color maps of tension (second Piola-Kirchhoff tension) over the undeformed leaflets (Fig. 4E-H). Plotting the next principal tension computed along the leaflet midline implies that as fibers angle is elevated tension is elevated in the low central part of the leaflets and reduced in top of the central part of the leaflets at the bottom from the coaptation area (Fig. 7). Fig. 6 Central coaptation elevation of simulated shut valve vs. the main material direction position in the commissures toward the leaflet free of charge edge. Nevertheless this design would bring about tangential displacement of leaflet tissues from the valve middle during loading reducing or eliminating central coaptation. A recent study (Fan et al. 2013 reproduced our preliminary result modeling the effect of a curved principal direction on the shape of the loaded Rabbit Polyclonal to ATN1. leaflet (Hammer 2011 adjusting their material properties to simulate an elastomeric pulmonary valve scaffold. This is the first study to report the relationship between the curved collagen pattern in the normal aortic valve leaflet and the shape and coaptation changes of the leaflets of the closed valve under load. One limitation of this study is the use of pig instead of human aortic valves although the close similarity between porcine and human aortic valves Bevirimat has been reported and the few normal human aortic valve leaflets that we have examined have similar gross collagen architecture to that of the porcine valves. Our computational model while based on experimentally measured leaflet shapes and material law still relies on the simplifying assumption that the orthotropic constitutive law is constant throughout each leaflet. We also make the assumption of constant leaflet thickness despite clear differences in thickness in different leaflet regions. This may be reasonable however for computing leaflet stress because the collagen rich layer that bears most of the stress is not noticeably thicker in the leaflet regions Bevirimat with increased thickness. Finally when measuring the leaflet outlines in the unstrained configuration we neglect the residual stress present in the leaflets. In fact this residual stress was manifest as a small increase in leaflet height after dissolving and dissecting away the unstained tissue. However our leaflet constitutive equation was based biaxial testing of intact leaflet patches and thus includes effects of residual stress. Furthermore we did not observe any consistent change in the pattern of the stained collagen fibers after the other leaflet tissues were dissolved and dissected away. The effect of the curved collagen.