miR-124 Negatively Regulates Osteogenic Differentiation and In vivo Bone Formation of Mesenchymal Stem Cells

• DOI: 10.1002/jcb.25026
• Publication Date: 2014-11-25T21:06:00Z
• Authors: Abdul S. Qadir; Soyoun Um; Heesu Lee; Kyunghwa Baek; Byoung Moo Seo; Gene Lee; Gwan-Shik Kim; Kyung Mi Woo; Hyun-Mo Ryoo; Jeong-Hwa Baek
• Keywords: Homeodomain Proteins; 0301 basic medicine; Osteoblasts; Bone Morphogenetic Protein 2; Mice, Nude; Cell Differentiation; Mesenchymal Stem Cells; Bone and Bones; Mice, Inbred C57BL; MicroRNAs; 03 medical and health sciences; Osteogenesis; Gene Knockdown Techniques; Antigens, Surface; Adipocytes; Animals; Humans; 3' Untranslated Regions; Cells, Cultured; Transcription Factors

MicroRNAs are novel key regulators of cellular differentiation. Dlx transcription factors play an important role in osteoblast differentiation, and Dlx5 and Dlx2 are known targets of miR-124. Therefore, in the present study, we investigated the regulatory effects of miR-124 on the osteogenic differentiation and in vivo bone formation of mesenchymal stem cells (MSCs). During osteogenic induction by BMP2, the expression levels of miR-124 were inversely correlated with those of osteogenic differentiation marker genes in human and mouse bone marrow-derived MSCs, MC3T3-E1 cells and C2C12 cells. The overexpression of a miR-124 mimic significantly decreased the expression levels of Dlx5, Dlx3, and Dlx2, whereas the silencing of miR-124 with hairpin inhibitors significantly increased the expression of these Dlx genes. Luciferase reporter assays demonstrated that miR-124 directly targets the 3'UTRs of Dlx3, Dlx5, and Dlx2. The overexpression of a miR-124 mimic suppressed the osteogenic marker gene expression levels, alkaline phosphatase activity and matrix mineralization, which were all significantly increased by the overexpression of a miR-124 inhibitor. When ectopic bone formation was induced by the subcutaneous transplantation of human bone marrow-derived MSCs in nude mice, MSCs overexpressing a miR-124 inhibitor significantly enhanced woven bone formation compared with control MSCs. However, MSCs overexpressing a miR-124 mimic exhibited increased adipocyte differentiation at the expense of ectopic bone formation. These results suggest that miR-124 is a negative regulator of osteogenic differentiation and in vivo bone formation and that the targeting of Dlx5, Dlx3, and Dlx2 genes partly contributes to this inhibitory effect exerted by miR-124.