Circ_FBLN1 promotes the proliferation and osteogenic differentiation of human bone marrow-derived mesenchymal stem cells by regulating let-7i-5p/FZD4 axis and Wnt/ß-catenin pathway.

BACKGROUND: Recently, more and more circular RNAs (circRNAs) have been identified in osteogenesis. In this study, we aimed to explore the effect of circ_FBLN1 on the osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (hBMSCs). METHODS: The protein levels of osteogenesis-related genes, let-7i-5p, frizzled class receptor 4 (FZD4), Ki67, Wnt6 and ß-catenin were measured by western blot assay. The levels of circ_FBLN1, FBLN1 mRNA and FZD4 mRNA were determined by quantitative real-time polymerase chain reaction (qRT-PCR) assay. The feature of circ_FBLN1 was investigated by RNase R and Actinomycin D assays. Cell proliferation ability was evaluated by colony formation assay and 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay. The targeting relationship between let-7i-5p and circ_FBLN1 or FZD4 was verified by dual-luciferase reporter assay. RESULTS: Circ_FBLN1 level was enhanced during the osteogenic differentiation of hBMSCs. Silencing of circ_FBLN1 repressed cell proliferation and osteogenic differentiation in hBMSCs. For mechanism analysis, circ_FBLN1 was found to act as a sponge for let-7i-5p and FZD4 served as a direct target gene of let-7i-5p. Let-7i-5p was downregulated during the osteogenic differentiation of hBMSCs and let-7i-5p inhibition restored the effects of circ_FBLN1 knockdown on the proliferation and osteogenesis of hBMSCs. Moreover, let-7i-5p overexpression suppressed cell proliferation and osteogenesis in hBMSCs through targeting FZD4. In addition, circ_FBLN1 knockdown reduced the levels of Wnt6 and ß-catenin in hBMSCs, indicating the inactivation of Wnt/ß-catenin pathway. CONCLUSION: Knockdown of circ_FBLN1 inhibited the proliferation and osteogenesis of hBMSCs by regulating let-7i-5p/FZD4 axis and repressing Wnt/ß-catenin pathway.

A new approach for risk assessment of aggregate dermal exposure to banned azo dyes in textiles.

A semi-quantitative risk assessment of banned azo dyes in textiles was performed to assess the health risk when consumers have direct dermal contact with these products. A novel model, which includes three exposure scenarios, was proposed to estimate the absorption of leachable azo dyes from twenty textiles samples. The effective daily uptakes of benzidine from sample 1 and sample 19 in chronic exposure model were 0.318 ng/kg-day and 0.011 ng/kg-day, respectively. Compared to virtually safe dose (VSD), the corresponding cancer risks were 7.42 × 10-5 (Sample 1) and 2.56 × 10-6 (Sample 19). As noted by nomograph assessment, the health risk induced by long-term exposure of banned azo dyes from textiles was at the range of "very low" to "low". In short-term exposure cases, the risks were acceptable though the amount of detected aromatic amines was relatively high in particular samples. The amount of exposure and the risk level might be overestimated as a series of assumptions were made under extreme conditions.