miR-365 promotes HOXA9-mediated differentiation of mesenchymal stem cells to nucleus pulposus cells by interacting with HIF-1α.

Abstract

Background: Degenerative disc disease (DDD) is characterized by the loss of nucleus pulposus cells (NPCs). Inducing differentiation of bone marrow mesenchymal stem cells (MSCs) into NPCs has emerged as a novel therapeutic strategy for DDD. However, the efficiency of MSC differentiation and the underlying mechanisms remain to be fully elucidated.

Aim: To investigate the role and mechanism of miR-365 in promoting the differentiation of MSCs into NPCs for DDD treatment.

Methods: In vitro, the effects of miR-365 on MSC proliferation, apoptosis, and differentiation were assessed by cell counting kit-8 assay, flow cytometry, and quantitative real-time polymerase chain reaction (qRT-PCR). In vivo, the expression levels of miR-365, HIF-1α, Sox9, Kdm6a, and HOXA9 in the spinal cord of rats with spinal cord injury were determined by qRT-PCR and Western blot.

Results: In vitro, miR-365 significantly promoted MSC proliferation and inhibited MSC apoptosis. The expression levels of glycosaminoglycans, proteoglycan, and type 2 collagen were significantly increased with miR-365 ectopic expression. In vivo, the expression levels of miR-365, HIF-1α, Sox9, and Kdm6a were significantly increased, whereas HOXA9 was remarkably decreased. Mechanically, miR-365 inhibited HOXA9 expression by directly binding to its 3' untranslated region. HOXA9 could inhibit HIF-1α expression by binding to the Hif-1α promoter, thereby affecting the expression levels of Sox9 and Kdm6a. Moreover, HOXA9 knockdown significantly reversed the differentiation of MSCs into NPCs induced by miR-365.

Conclusion: miR-365 promotes HOXA9-mediated differentiation of MSCs into NPCs by interacting with HIF-1α and may serve as a potential target for DDD treatment.