Fluoride induces hypomethylation of BMP2 and activates osteoblasts through the Wnt/β-catenin signaling pathway

Skeletal fluorosis has become a public health issue in recent years as its serious impact on patients' life expectancy. Bone morphogenetic protein 2 (BMP2) plays a key role in promoting osteogenesis. However, the mechanism of BMP2-Wnt/β-catenin axis in skeletal fluorosis needs further exploration.The RT-qPCR and western blot assay were carried out to examine the mRNA and protein levels. Cell viability was measured by MTT assay. A commercial ALP assay kit was used to detect ALP activities. Alizarin Red staining was performed to measure the formation of mineralized nodules. Methylation-specific PCR (MSP) was performed to measure the methylation level of BMP2.Fluoride promoted the expression of osteogenic marker genes (OPN, OCN, OSX and RUNX2) and induced the proliferation and differentiation of MC3T3-E1 cells. Fluoride induced hypomethylation and high expression of BMP2. Furthermore, knockdown of BMP2 reversed the promoting effect of fluoride on osteogenic differentiation of MC3T3-E1. The expression of β-catenin, glycogen synthase kinase 3β (GSK3β), wingless/integrated 3α (Wnt3α), low-density lipoprotein receptor-related protein 5 (LRP5) and dishevelled 1 (Dv1) were increased in osteoblasts treated with fluoride, however, knockdown of BMP2 reversed this phenomenon. Simultaneous knockdown of BMP2 and β-catenin significantly inhibited the differentiation of osteoblasts induced by fluoride.Fluoride contributed to proliferation and differentiation of osteoblasts through BMP2-Wnt/β-catenin axis, providing a feasible theoretical basis for the treatment of skeletal fluorosis.