Differential miRNA profiles in fluoride-exposed rBMSCs-EVs and the influence of miR-320-3p transfer on osteogenic differentiation.

Long-term excessive fluoride ingestion may lead to skeletal fluorosis, a disease characterized by unclear pathogenesis and lack of effective cure. Bone marrow mesenchymal stem cell-derived extracellular vesicles (BMSCs-EVs) exert a crucial regulatory effect on bone remodeling and have broad clinical application prospects. Whether BMSCs-EVs can participate in the occurrence and development of skeletal fluorosis by transferring miRNAs is a scientific question worth exploring. In this study, miRNA sequencing was used to screen for differentially expressed miRNAs in fluoride-exposed rBMSCs-EVs (F-EVs). The top 15 differentially expressed miRNAs were subjected to target gene prediction, and GO and KEGG analyses as well as PPI network construction were performed. On this basis, miR-320-3p was selected for in-depth study. First, our data revealed that miR-320-3p was upregulated in fluoride-exposed osteoblasts and was involved in the enhancement of fluoride-induced osteogenic differentiation. Subsequently, a tracing experiment confirmed that rBMSCs-EVs and their miR-320-3p could be successfully taken up by fluoride-exposed osteoblasts. Then, elevated levels of miR-320-3p in F-EVs could further promote the enhancement of fluoride-induced osteogenic differentiation, while EVs with inhibited miR-320-3p exerted a significant inhibitory effect. Mechanism studies revealed that under fluoride exposure, rBMSCs-EVs could regulate Igf1r/ERK1/2/MAPK by transferring miR-320-3p, thereby affecting osteogenic differentiation. This study is the first to elucidate the pathogenesis of skeletal fluorosis from the rBMSCs-EVs miRNAs and provides new ideas for the clinical management of skeletal fluorosis.