Effect of miR-21 on HIF-1α and osteogenic differentiation. (A) Transfection efficiency of miR-21 mimics. RT-qPCR confirmed that miR-21 mimics increased the expression of miR-21. (B) Transfection efficiency of miR-21 inhibitors. RT-qPCR confirmed that miR-21 inhibitors significantly decreased the expression of miR-21. (C) miR-21 mimics significantly increased the expression of HIF-1α by 3.9-fold, and miR-21 inhibitors decreased the expression of HIF-1α by 0.7-fold. (D) miR-21 mimics upregulated HIF-1α protein by 1.5-fold, and significantly increased the protein expression of osteogenic markers-OPN by 1.7-fold, RUNX-2 by 2.1-fold and ALP by 1.2-fold. (E) miR-21 inhibitors suppressed HIF-1α protein by 0.1-fold, and significantly decreased the protein expression of RUNX-2 by 0.6-fold and ALP by 0.7-fold. No significant difference was identified in OPN expression between the control and miR-21 inhibitors group (*P<0.05, **P<0.01 vs. the control group). miR, microRNA; HIF-1α, hypoxia-inducible factor-1α; OPN, osteopontin; RUNX-2, runt-related gene-2; ALP, alkaline phosphatase; RT-qPCR, reverse transcription-quantitative polymerase chain reaction.