CircTTC3 regulates the osteogenic differentiation of adipose-derived mesenchymal stem cells via miR-205/Smad3 axis

Adipose-derived mesenchymal stem cells (ADSCs) hold great promise for bone tissue repair and regeneration. Circular RNAs (circRNAs) play a crucial role in regulating the osteogenic differentiation and bone remodeling of ADSCs; however, the underlying molecular mechanisms remain unclear. In this study, we conducted whole transcriptome sequencing (WTS) on ADSCs and constructed a competing endogenous RNA (ceRNA) regulatory network to identify the circTTC3/miR-205/mothers against decapentaplegic homolog 3 (Smad3) signaling axis. Subsequently, we used Sanger sequencing and agarose gel electrophoresis to verify the cyclization of circTTC3. We confirmed that circTTC3 promotes the osteogenic differentiation of ADSCs and demonstrated that circTTC3 co-localizes with miR-205 in the cytoplasm. Additionally, we showed that circTTC3 sponges miR-205 using dual-luciferase reporter assays and fluorescent in situ hybridization (FISH) experiments. Moreover, miR-205 targets the 3' untranslated region (UTR) of Smad3. Rescue experiments further verified that circTTC3 mediates the osteogenic differentiation of ADSCs through the miR-205/Smad3 pathway. Finally, in vivo, animal studies revealed that circTTC3 overexpression enhances cranial defect repair while silencing circTTC3 disrupts new bone formation.