Implication of Receptor Activator of NF-κB Ligand in Wnt/β-Catenin Pathway Promoting Osteoblast-like Cell Differentiation

Recent studies showed that activation of Wnt/β-catenin pathway promoted the differentiation of osteoblast-like cells in the arterial calcification, but its mechanism remains unknown. In this study, the hypothesis that Wnt/β-catenin pathway promotes the differentiation of osteoblast-like cells by upregulating the expression of receptor activator of NF-κB ligand (RANKL) was examined. LiCl was used to activate the Wnt/β-catenin pathway. The differentiation of osteoblast-like cells was observed by Von Kossa staining, calcium content assay, alkaline phosphatase (ALP) activity assay, and detection of osteocalcin expression. Real-time PCR was performed to detect the expression of RANKL and osteoprotegerin (OPG, the decoy receptor of RANKL) during the osteoblast-like cell differentiation. Different concentrations of OPG were added to the culture media respectively to inhibit the function of RANKL, and the change in the differentiation of osteoblast-like cells was evaluated. The results showed that when the Wnt/β-catenin pathway was activated by LiCl, the expression of RANKL was significantly in-creased, which coincided with the differentiation of osteoblast-like cells (P<0.05), and the OPG treatment could partly attenuate the promoting effect of Wnt/β-catenin pathway on the differentiation of osteoblast-like cells (P<0.05), but it failed to completely abolish such effect. It was concluded that activation of Wnt/β-catenin pathway promotes the differentiation of osteoblast-like cells by both RANKL-dependent and RANKL-independent mechanisms.     

大鼠主动脉钙化过程中骨保护素/NF-κB配体的受体变化及意义

目的:研究大鼠主动脉钙化过程中骨保护素(OPG)/NF-κB配体的受体(RANKL)变化及意义。方法:60只SD大鼠随机分为钙化组、他汀组和对照组,每组再分早、晚期两个亚组。钙化组给予华法林灌胃,他汀组给予华法林和阿托伐他汀灌胃。早期亚组在第17天、晚期亚组在第34天取大鼠主动脉,用Von Kossa染色,以碱性磷酸酶(ALP)活性检测与骨钙素Western Blot检测来判定钙化情况,用实时定量PCR检测OPG和RANKL的表达情况。结果:对照组无论早晚期都有大量的OPG表达,但没有RANKL表达。钙化组和他汀组早期OPG表达上升,晚期下降,而RANKL表达在钙化过程中一直呈升高趋势;对照组、他汀组、钙化组随着钙化程度的加重,OPG/RANKL比值呈逐步下降趋势(均P<0.05);同一组中,晚期亚组随着钙化的加重,OPG/RANKL比值也较早期明显下降(均P<0.05)。结论:OPG/RANKL的比值与主动脉钙化程度呈负相关,且阿托伐他汀具有抑制钙化的作用。