The circ_0054633/miR-590-3p/RUNX2 positive feedback loop promotes the osteogenic differentiation of BMSCs.

Background: Mandibular bone marrow stem cells (BMSCs) from patients with type 2 diabetes mellitus (T2DM) have poor osteogenic differentiation capacity. Elucidating the molecular mechanisms by which circular RNAs (circRNAs) play specific roles in T2DM will reveal new diagnostic biomarkers and therapeutic targets.

Methods: BMSCs with different circ_0054633 expression levels were generated. Furthermore, alkaline phosphatase (ALP) activity, alizarin red staining (ARS), and transplantation of HA/tricalcium phosphate into BMSCs were performed to detect the osteogenic effects of different levels of circ_0054633 expression in BMSCs in vivo and in vitro.

Results: In this study, we identified 80 differentially expressed circRNAs in jawbone-derived BMSCs from patients with T2DM. Notably, significant downregulation of circ_0054633 promoted the osteogenic differentiation of these cells in vitro and in vivo. Mechanistically, circ_0054633 acts as a miRNA sponge; specifically, it actively regulates the expression of RUNX2 by sponging miR-590-3p and thus promoting the osteogenic differentiation of the BMSCs. In addition, we found that circ_0054633 was a direct transcriptional target of RUNX2. RUNX2 overexpression activated the circ_0054633 promoter and promoted the generation of nuclear circ_0054633, whereas RUNX2 knockdown abrogated the osteogenic role of circ_0054633 and formed a circ_005463/miR-590-3p/RUNX2 positive feedback loop.

Conclusions: Our results suggest that the circ_0054633/miR-590-3p/RUNX2 positive feedback loop promotes the osteogenic differentiation of BMSCs and is expected to be a potential biomarker and therapeutic target for bone regeneration in T2DM.