Gene Expression and Collagen Fiber Micromechanical Interactions of the Semilunar Heart Valve Interstitial Cell
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The semilunar (aortic and pulmonary) heart valves function under dramatically different hemodynamic environments, and have been shown to exhibit differences in mechanical properties, extracellular matrix (ECM) structure, and valve interstitial cell (VIC) biosynthetic activity. However, the relationship between VIC function and the unique micromechanical environment in each semilunar heart valve remains unclear. In the present study, we quantitatively compared porcine semilunar mRNA expression of primary ECM constituents, and layer- and valve-specific VIC–collagen mechanical interactions under increasing transvalvular pressure (TVP). Results indicated that the aortic valve (AV) had a higher fibrillar collagen mRNA expression level compared to the pulmonary valve (PV). We further noted that VICs exhibited larger deformations with increasing TVP in the collagen rich fibrosa layer, with substantially smaller changes in the spongiosa and ventricularis layers. While the VIC–collagen micromechanical coupling varied considerably between the semilunar valves, we observed that the VIC deformations in the fibrosa layer were similar at each valve’s respective peak TVP. This result suggests that each semilunar heart valve’s collagen fiber microstructure is organized to induce a consistent VIC deformation under its respective diastolic TVP. Collectively, our results are consistent with higher collagen biosynthetic demands for the AV compared to the PV, and that the valvular collagen microenvironment may play a significant role in regulating VIC function.
KeywordsValve morphology Extracellular matrix Microstructure Cellular deformations Mechanobiology Heart valve remodeling Tissue engineered heart valve
We thank Greg Gibson for training and assistance on the multi-photon microscope. Funding for this work was provided by NIH Grants R01 HL068816, R01 HL089750, and U54 RR022241. Christopher Carruthers was partially supported by NIH T32 EB003392 and a National Science Foundation Graduate Research Fellowship.
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