Promotive Role of CircATRNL1 on Chondrogenic Differentiation of BMSCs Mediated by miR-338-3p

Bone marrow mesenchymal stem cells (BMSCs) are ideal seed cells for tissue engineering cartilage construction. However, the underlying mechanism of it has not been illuminate well. In this study, the effects of circATRNL1 (hsa_circ_0020093) on the differentiation of BMSCs into chondrocytes were investigated. The degrees of chondrogenic differentiation of BMSCs on day 0, 14 and 21 mediums were detected by Alcian blue staining. Expressions of cartilage differentiation related factors SOX9, COL2 and Aggrecan, and circATRNL1 in BMSCs under differentiation were determined by western blot and quantitative real-time polymerase chain reaction (qRT-PCR) as needed. circATRNL1 knockdown or overexpression was performed in BMSCs. Then the viability of BMSCs and cartilage differentiation related factors were separately investigated through MTT assay, qRT-PCR, and western blot. Target gene of circATRNL1 and binding site were predicted using starbase and validated it by dual luciferase reporter. The effect of circATRNL1 and its target gene on chondrogenic differentiation of BMSCs was assessed using Alcian blue staining further. The degrees of chondrogenic differentiation of BMSCs were increased with time. Expressions of SOX9, COL2 and Aggrecan as well as circATRNL1 were enhanced during chondrogenic differentiation. Furthermore, overexpression of circATRNL1 enhanced BMSCs proliferation, SOX9, COL2 and Aggrecan expressions and the degree of chondrogenic differentiation of BMSCs. Further research showed that circATRNL1 targeted miR-338-3p. MiR-338-3p inhibited differentiation of BMSCs into cartilage but overexpression of circATRNL1 reversed it. CircATRNL1 is beneficial to BMSCs differentiation into cartilage by regulating miR-338-3p, which may be a new mechanism of action in the treatment of cartilage repair.