Intrinsic Phenotypic Differences, Not Hemodynamic Shear, Associate with Cusp-Specific Remodeling in Aortic Valve Disease

Abstract

Aortic valve disease (AVD) is asymmetric. Various clinical reports indicate that the non- coronary cusp (NCC) is disproportionally burdened by pathological remodeling like inflammation, fibrosis, and calcification. This has long been attributed to the resulting differences in hemodynamic load that arise from the presence, or lack thereof, of coronary ostia in respective sinuses. However, there is little to no empirical evidence to suggest that these differences in hemodynamic shear alone are enough to drive the difference in pathological remodeling that is observed. C57BL/6J mice exhibit a high variance in right coronary ostium (RCO) positioning with respect to the right coronary cusp (RCC). Through computational fluid dynamics (CFD) simulations of a mouse aortic valve (AoV) during end diastolic loading, we show negligible differences in wall shear stress (WSS) between a high RCO on the RCC and no ostium on the NCC. Also, though CFD analyses depict at least an order of magnitude difference in WSS through physiologically relevant ostia positions within the sinuses, ostium position does not correlate with calcification burden in a CKD mouse model of calcific AVD. Cusp dependent extracellular matrix (ECM) abundance analysis reveals asymmetric collagen and elastin content in healthy adult mice, but this does not follow the same trend as pathological remodeling. Instead, asymmetric abundance of elastin (P=0.034) and collagen (P=0.018) was mainly driven by an increase of these ECM proteins in the left coronary cusp (LCC) with no differences in leaflet thickness. Cusp dependent transcriptomic (spatial and bulk RNA sequencing) analyses reveal asymmetric phenotypic profiles between the three cusps in healthy adult mice. Of note, genes associated with vascular smooth muscle cell contraction and known modulators of AoV remodeling were upregulated in the NCC and downregulated in both the RCC and LCC. Together, these data suggest that the differences in shear resulting from the coronary ostia are not sufficient to explain the asymmetric onset of calcific AVD.