Role of the Wnt/β-catenin signaling pathway in regulating the phenotypic transformation of aortic valvular myofibroblasts to osteoblast-like cells

Abstract

Objective To elucidate the role of the Wnt/ -catenin signaling pathway in regulating the phenotypic transformation of aortic valvular myofibroblasts to osteoblast-like cells. Methods Cultured primary valvular myofibroblastes isolated from porcine aortic valve leaflets were treated with oxidized low-density lipoprotein (ox-LDL) for different lengths of time: 24 h, 48 h and 72 h. The Wnt signaling pathway inhibitor Dickkopf-1 (DDK-1) was co-incubated with ox-LDL for 72 h. After cells harvest, the expression of myofibroblastic or osteoblast-like phenotype related markers, α-smooth muscle actin (α-SMA), bone morphogenetic protein 2 (BMP2), alkaline phosphatase (ALP) and core-binding factorα-1 (Cbfα-1), was detected by Western blotting. The expression and sub-cellular localization of β-catenin was assessed by immunocytochemistry. Changes of the Wnt/β-catenin signaling pathway and the transformation of aortic valvular myofibroblast to osteoblast-like cells were monitored. Results BMP2, ALP and Cbfa-1 protein expression was not or barely detectable in the control group. However, after ox-LDL treatment, the expression of α-SMA, BMP2, ALP and Cbfa-1 increased significantly (each P<0.01) in a time-dependent manner (each P<0.05). Besides, ox-LDL was also able to up-regulate the protein expression of β-catenin in a time-dependent manner (P<0.05) and promoted its nuclear translocation. After DKK-1 treatment, the protein expression of β-catenin and osteogenesis-related markers was down-regulated (P<0.05). Conclusions The Wnt/β-catenin signaling pathway may play a crucial role in regulating the transformation of aortic valvular myofibroblasts to an osteoblast-like phenotype. Key words: Heart Valves; Fibroblasts; Wnt/ -catenin; Osteoblasts