circNR3C2 promotes chondrogenic differentiation and cartilage repair of human adipose-derived stem cells via the hsa-miR-647/SOX9 pathway.

BACKGROUND: Human adipose-derived stem cells (hADSCs) are seed cells with application prospects in cartilage repair. However, the mechanism of hADSC chondrogenic differentiation is still unclear. This study identifies a novel circRNA, circNR3C2, which is significantly upregulated during the chondrogenic differentiation of hADSCs. METHODS: To analyze their role in hADSC chondrogenic differentiation, hADSCs were separated and identified by flow cytometry. Thereafter, we conducted Alcian Blue staining to assess chondrogenic differentiation levels. Additionally, RT-qPCR was carried out to detect levels of the cartilage-related genes COL2, Aggrecan and SOX9. Moreover, overlapping target SOX9 and circNR3C2 miRNAs were detected by bioinformatics and luciferase analyses. Finally, the role of circNR3C2 was confirmed in vivo using animal models. RESULTS: We confirmed that the cell surface receptors CD44, CD90 and CD105 were positively expressed on hADSCs, and their cartilage differentiation levels dramatically increased after 2 weeks. Expression of the cartilage-related genes COL2 and Aggrecan and circNR3C2 also markedly increased. CircNR3C2 overexpression enhanced cartilage differentiation of hADSCs, while up-regulating COL2, SOX9 and Aggrecan. Bioinformatics analysis identified hsa-miR-647 as the target miRNA of circNR3C2 and SOX9. Hsa-miR-647 overexpression in hADSCs can antagonize the effect of circNR3C2 on chondrogenic differentiation, and reverse its effect on regulating the expression of COL2, Aggrecan, and SOX9. We also showed that hADSCs overexpressing circNR3C2 promote cartilage repair in vivo. CONCLUSIONS: We show that circNR3C2 modulates SOX9 expression to promote hsa-miR-647-mediated hADSC chondrogenic differentiation; targeting circNR3C2 may help to develop new treatments to manage cartilage-related disorders.