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, Ca 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, Ca 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.