Abstract 443: The Role of Wnt5b and Wnt11 in Aortic Valve Calcification

Abstract

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.