miR‑21 promotes osteoclastogenesis through activation of PI3K/Akt signaling by targeting Pten in RAW264.7 cells.

The present study aimed to investigate the effects of microRNA (miR)‑21 on osteoclastogenesis and its underlying molecular mechanisms. The expression levels of tartrate‑resistant acid phosphatase (TRAP) and miR‑21 were detected during osteoclastogenesis in receptor activator of NF‑κB ligand (RANKL)‑induced RAW264.7 cells via reverse transcription‑quantitative PCR. Bioinformatics and dual luciferase reporter assays were performed to analyze the association between miR‑21 and Pten. RANKL‑induced RAW264.7 cells were divided into the following groups: MiR‑negative control (NC), miR‑21 mimic, miR‑21 inhibitor and miR‑21 mimic + LY294002. The effects of miR‑21 on osteoclastogenesis and bone resorption were then detected using TRAP staining and a bone resorption assay. Pten, phosphorylated‑Akt and nuclear factor of activated T cell (NFATc1) expression levels were measured by western blotting to analyze the effects of miR‑21 on the PI3K/Akt signaling pathway. The present study revealed that miR‑21 was upregulated during osteoclastogenesis in RANKL‑induced RAW264.7 cells. Furthermore, miR‑21 negatively regulated Pten. Compared with the miR‑negative control (NC) group, the number of osteoclasts and the percentage of bone resorption were increased in the miR‑21 mimic group, whereas they were decreased in the miR‑21 inhibitor group. The number of osteoclasts and the percentage of bone resorption in the miR‑21 mimic + LY294002 group were lower than in the miR‑21 mimic group. Compared with the miR‑NC group, the protein expression levels of Pten were decreased, whereas p‑Akt and NFATc1 were increased in the miR‑21 mimic group. Conversely, Pten protein expression was increased, whereas p‑Akt and NFATc1 were decreased in the miR‑21 inhibitor group. In the miR‑21 mimic + LY294002 group, Pten protein expression was higher, and p‑Akt and NFATc1 were lower than in the miR‑21 mimic group. In conclusion, miR‑21 is upregulated during osteoclastogenesis, and may promote osteoclastogenesis and bone resorption through activating the PI3K/Akt signaling pathway via targeting Pten.