MicroRNA-21 from bone marrow mesenchymal stem cell-derived extracellular vesicles targets TET1 to suppress KLF4 and alleviate rheumatoid arthritis

BACKGROUND: Accumulating evidence has demonstrated that bone marrow mesenchymal stem cells (BMSCs)-derived extracellular vesicles (EVs) can be used effectively to transfer drugs and biomolecules to target lesions. Meanwhile, BMSCs have been reported to be beneficial in the treatment of rheumatoid arthritis (RA). In this study, we employ gain- and loss-of-function experiments to determine how BMSCs-derived EVs alleviate RA in vitro and in vivo. METHODS: We isolated EVs from BMSCs and characterized them by transmission electron microscopy and western blot analysis. The regulatory relationship between miR-21 and TET1 was predicted by bioinformatics analysis and validated by dual luciferase assay. Next, we utilized bisulfite sequencing PCR to decipher how TET1 promoted KLF4 transcription. Then, we established an RA mouse model and determined the role of miR-21 in RA progression. Functional assays were used to validate the role the miR-21-TET1-KLF4 regulatory axis in controlling mouse fibroblast-like synoviocytes (mFLS) cell proliferation and inflammatory cytokines secretion in vitro. RESULTS: RT-qPCR results revealed that miR-21 was highly expressed in BMSCs-derived EVs, and confirmed that BMSCs-derived EVs transferred miR-21 into mFLS cells. Bioinformatic analysis predicted that TET1 was the directly downstream target of miR-21, which was further validated by dual luciferase assay. TET1 promoted KLF4 promoter methylation to increase its expression. Collectively, BMSCs-derived EVs relieved RA by delivering miR-21, while the exosomal miR-21 alleviated RA through targeting the TET1/KLF4 regulatory axis. CONCLUSION: miR-21 from BMSCs-derived EVs suppresses KLF4 to relive RA by targeting TET1.