These findings suggest a potential role for noncanonical Wnt signaling in the pathogenesis of aortic valve calcification.

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Introduction: The mechanisms underlying the pathogenesis of aortic valve calcification remain unclear. With accumulating evidence demonstrating that valve calcification recapitulates bone development, the crucial roles of non-canonical Wnt ligands Wnt5b and Wnt11 in osteogenesis make them critical targets in the study of aortic valve calcification. Hypothesis: We hypothesized that Wnt signaling mediated by ligands Wnt5b and Wnt11 is upregulated and the expression of these molecules may be associated with the pathological calcium deposition in aortic valves. Methods and Results: Mitral, non-calcified and calcified aortic valves were collected from patients with valve replacement. Total RNA was isolated, first strand cDNAs were synthesized and gene specific qPCRs were performed. The relative mRNA expression of Wnt5b and Wnt11 were calculated using the ΔΔCT method against GAPDH control and are expressed as fold change ± SEM compared to expression in non-calcified valves. We found significant increases in both Wnt5b (15.14±4.08) and Wnt11 (4.09±0.63) expression in calcified compared to non-calcified aortic or mitral valves (P<0.05). We also examined Wnt5b and Wnt11 protein expression in 73 mitral, non-calcified and calcified aortic valves by immunohistochemistry. There was little expression of Wnt11 or Wnt5b in normal aortic valves, normal segments of calcified valves or mitral valves. Wnt11 staining intensity was significantly elevated in areas of calcification, inflammation and in activated myointimal cells compared to normal aortic and mitral valves (P<0.05). Immunostaining for Wnt5b was expressed in similar cellular compartments as well as areas of fibrosis. Multivariant Spearman correlation analyses revealed significant positive correlations between Wnt5b and Wnt11 overall staining with calcification, lipid score, fibrosis, valve remodeling and microvessels (P<0.05). We are currently evaluating the tissue expression of these two molecules with clinical parameters of the disease. Conclusion: The upregulated Wnt5b and Wnt11 expression in calcified aortic valves, particularly in areas of calcification, fibrosis and activated myointimal cells suggests a potential involvement in the pathogenesis of aortic calcification.

Introduction: Atherosclerosis is a leading cause of death in Western societies. Vasoactive peptide urotensin II (UII) is upregulated in atherosclerosis and several other cardiovascular diseases however further research is required to develop a complete understanding of UII’s role in the pathogenesis of atherosclerosis. Hypothesis: We hypothesized that UII stimulates calcification in vascular smooth muscle cells and that UII, urotensin II related peptide (URP) and UT receptor expression are upregulated in calcified aortic valves. Methods and Results: Human aortic smooth muscle cells (HASMC) were cultured in phosphate media (2.6mmol/L) for 13 days in the presence of varying concentrations of UII (0, 10, 50, 100nm) and the amount of calcium was measured with a calcium assay kit. Protein was extracted and measured with a protein assay kit. HASMC calcification was assessed as the ratio of calcium (μg)/protein (mg). HASMC calcification increased with increasing UII concentration and was significantly elevated in 100nm of UII (N=6, P<0.05) 13 days after incubation. We also examined UII, URP and UT protein expression in 90 carotid endarterectomies and 87 mitral, non-calcified and calcified aortic valves by immunohistochemistry. Multivariant Spearman correlation analyses in carotids revealed significant positive correlations between UII, URP and UT overall staining with calcification, remodeling and inflammation (P<0.05). In valves there was significant positive correlations between UII, URP and UT overall staining with calcification, fibrosis, remodeling, inflammation, lipid score and microvessels (P<0.05). Conclusion: The stimulatory effect of UII on vascular smooth muscle cell calcification as well as the upregulated expression of UII, URP and UT in calcified aortic valves suggests that the UT receptor system plays a key role in the pathogenesis of atherosclerosis and valve calcification.