Wnt Signaling Pathway Inhibitor Sclerostin Inhibits Angiotensin II-Induced Aortic Aneurysm and Atherosclerosis

Objective-Sclerostin (SOST) has been identified as an important regulator of bone formation; however, it has not been previously implicated in arterial disease. The aim of this study was to assess the role of SOST in aortic aneurysm (AA) and atherosclerosis using human samples, a mouse model, and in vitro investigations. Approach and Results-SOST protein was downregulated in human and mouse AA samples compared with controls. Transgenic introduction of human SOST in apolipoprotein E-deficient (ApoE(-/-)) mice (SOSTTg. ApoE(-/-)) and administration of recombinant mouse Sost inhibited angiotensin II-induced AA and atherosclerosis. Serum concentrations of several proinflammatory cytokines were significantly reduced in SOSTTg. ApoE(-/-) mice. Compared with controls, the aortas of mice receiving recombinant mouse Sost and SOSTTg. ApoE(-/-) mice showed reduced matrix degradation, reduced elastin breaks, and preserved collagen. Decreased inflammatory cell infiltration and a reduction in the expression of wingless-type mouse mammary virus integration site/beta-catenin responsive genes, including matrix metalloproteinase-9, osteoprotegerin, and osteopontin, were observed in the aortas of SOSTTg. ApoE(-/-) mice. SOST expression was downregulated and the winglesstype mouse mammary virus integration site/beta-catenin pathway was activated in human AA samples. The cytosinephosphate- guanine islands in the SOST gene promoter showed significantly higher methylation in human AA samples compared with controls. Incubation of vascular smooth muscle cells with the demethylating agent 5-azacytidine resulted in upregulation of SOST, suggesting that SOST is epigenetically regulated. Conclusions-This study identifies that SOST is expressed in the aorta and downregulated in human AA possibly because of epigenetic silencing. Upregulating SOST inhibits AA and atherosclerosis development, with potential important implications for treating these vascular diseases.