Down-regulation of miR-339 promotes differentiation of BMSCs and alleviates osteoporosis by targeting DLX5

J. Zhou, H. Nie, P. Liu, Z. Wang, B. Yao, L. Yang

Department of Orthopedic, East Campus of Sichuan Provincial People’s Hospital, Chengdu, China. doctorzhouji@163.com

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• Orthopedics

OBJECTIVE: It was the aim of this study to investigate whether miR-339 may affect osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) by targeting DLX5, thereby alleviating osteoporosis.

MATERIALS AND METHODS: BMSCs were isolated from the bone marrow of mice. The expression levels of miR-339 and DLX5 during the process of osteogenesis was detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). Meanwhile, the expression of downstream osteogenesis-associated proteins, such as runt-related transcription factor 2 (RUNX2) and osteopontin (OPN), were also detected after overexpression or inhibition of miR-339. The alkaline phosphatase (ALP) activity was measured in cells by ALP activity assay kit. Alizarin red staining was performed to reveal the cell mineralization ability. The luciferase reporter gene assay was used to identify the targeted pairings of miR-339 and DLX5 genes. In addition, the expression of DLX5 was detected by Western blot analysis after overexpression or knockdown of miR-339. Rescue test was applied to evaluate whether miR-339 could affect the differentiation of BMSCs by inhibiting the expression of DLX5.

RESULTS: QRT-PCR showed that miR-339 expression gradually decreased while the expression of DLX5 increased during the induction culture of BMSCs. After overexpression of miR-339 in BMSCs, the expression levels of ALP, RUNX2, and OPN were reduced. Besides, ALP activity assay showed a decreased cell ALP activity. RUNX2 protein expression was also decreased. In addition, Alizarin red staining detected a significant increase in cell mineralization, whereas silencing miR-339 resulted in an opposite result. These results indicated that miR-339 could regulate the osteogenic differentiation of BMSCs. Subsequently, we predicted using bioinformatics software that miR-339 might target DLX5, and validated this hypothesis by luciferase reporter assay. Finally, Western blot and ALP activity assay revealed that DLX5 could reverse the inhibitory effect of overexpression of miR-339 on osteogenic differentiation of BMSCs.

CONCLUSIONS: Down-regulation of miR-339 can promote osteogenic differentiation of BMSCs by targeting DLX5, thereby relieving osteoporosis.

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