Boyin Jia ^1* Xintong Han ^1* Xinyi Li ^1* Linlin Zhang ^1* Fuquan Ma ^1* Yusu Wang ¹ Xue Wang ^1* Yaru Yan ^1* Yaxin Li ^1* Junnan Shen ^1* Xinran Chen ^1* Xinyi Li ^1* Qianzhen Zhang ^1* Pengfei Hu ^2* Rui Du ^1*

• ¹ Jilin Agriculture University, Changchun, China
• ² Changchun Sci-Tech University, changchun, China

Deer antler-derived reserve mesenchyme cells (RMCs) are a promising source of cells for cartilage regeneration therapy due to their chondrogenic differentiation potential. However, the regulatory mechanism has not yet been elucidated. microRNAs (miRNAs) have been shown to regulate the differentiation of various mesenchymal stem cells (MSCs) and play an important role in the post-transcriptional regulation of chondrogenesis and hypertrophic differentiation. In this study, we demonstrated that the RMCs showed typical MSCs differentiation potentials. During chondrogenic differentiation, we obtained the expression profile of miRNAs, among which miR-145 was the most prominent candidate as key microRNA involved in the balance of chondral and endochondral differentiation. Knockdown of miR-145 promoted chondrogenesis and inhibits hypertrophy differentiation in RMCs. Mechanically, by online databases prediction combined with dual-luciferase reporter assay, SOX9 was suggested as a target of miR-145. Further validation experiments confirmed that knockdown of miR-145 contributed to the balance between endochondral versus chondral differentiation of RMCs by targeting SOX9. Additionally, RMCs transfected with the miR-145 knockdown mediated of lentiviral vector successfully promoted cartilage regeneration in vivo. In summary, our study suggested that the reciprocal negative feedback between SOX9 and miR-145 was essential for balancing between endochondral versus chondral differentiation of RMCs. Our study suggested that modification of RMCs using miRNAs transduction might be an effective treatment for cartilage defects.