microRNA-199a counteracts glucocorticoid inhibition of bone marrow mesenchymal stem cell osteogenic differentiation through regulation of Klotho expression in vitro.

Osteogenic differentiation (OD) of bone marrow mesenchymal stem cells (BMSCs) is critically important for mitigation of osteoporosis. Glucocorticoids (GCs) are extensively used for treating chronic inflammation, although long-term exposure to GCs is capable of triggering osteoporosis. microRNAs (miRNAs) have been reported to play a critical role in bone diseases. In the present study, we treated BMSCs with dexamethasone (DEX) during OD to stimulate GC-mediated osteoporosis. Microarray and quantitative polymerase chain reaction (Q-PCR) assays demonstrated that miR-199a was upregulated during OD of BMSCs, while DEX treatment caused a significant reduction in miR-199a. Alkaline phosphatase (ALP) activity, Alizarin red (AR) staining, and Q-PCR were applied to assess the role of miRNA-199a overexpression in DEX-triggered OD inhibition. miR-199a was able to rescue OD and ALP activity, which were inhibited by DEX. Additionally, we observed that ALP, BMP2, COL1A1, and Runx2 were increased after transfection of miRNA-199a mimics. Furthermore, we confirmed that miRNA-199a facilitates OD of BMSCs through direct inhibition of Klotho protein and messenger RNA expression affecting the downstream fibroblast growth factor receptor 1/extracellular-signal-regulated kinase and Janus kinase 1/signal transducer and activator of transcription 1 pathways. This study indicates that miR-199a plays a critical role in preventing GC-mediated osteoblast differentiation and may function as a promising miRNA biomarker for osteoporosis.