Role of Wnt/β-Catenin Pathway in the Arterial Medial Calcification and Its Effect on the OPG/RANKL System.

In this study, the hypothesis that Wnt/β-catenin pathway is involved in the arterial calcification by regulating the osteoprotegerin (OPG)/receptor activator of NF-κB ligand (RANKL) system was tested. The β-catenin expression was measured in the warfarin-induced calcified arteries and the osteoblast-like cells differentiating from smooth muscle cells (SMCs) by immunohistochemistry and Western blotting. The Wnt/β-catenin pathway was activated or inhibited by lithium chloride (LiCl) or dickkopf 1 (DKK1) in vitro and in vivo. Then the calcification level was determined by von Kossa staining, Ca2+ content assay, and alkaline phosphatase (ALP) activity assay. The expression levels of osteocalcin, OPG and RANKL were detected by Western blotting or real-time PCR. The results showed that in calcified arteries and OBL cells, the activation of Wnt/β-catenin pathway significantly enhanced the calcification as evidenced by increased von Kossa stains, Ca2+ contents, ALP activities, and osteocalcin expression levels (P<0.05), and it promoted the RANKL expression (P<0.05), but slightly affected the OPG expression. These results indicated that the activation of Wnt/β-catenin pathway worsens the arterial calcification, probably by promoting the RANKL expression.