LAUSR

The influence of miRNA‐1225‐5p (miR‐1225) and Keap1‐Nrf2 signalling on in vitro osteoclast differentiation in mouse models was studied along with the underlying mechanism. In differentiated bone marrow–derived macrophages (BMMs), downregulated miR‐1225 and upregulated Keap1 were observed in the course of receptor activator of nuclear factor kappa‐Β ligand (RANKL)–mediated osteoclastogenesis. Bioinformatic analysis and dual‐luciferase reporter assay showed that miR‐1225 targeted the three prime untranslated region (3′‐UTR) of Keap1 mRNA and caused its degradation. Transfection of a miR‐1225 mimic or Keap1 silencing was found to inhibit osteoclastogenesis as evidenced by loss of activity and tartrate‐resistant acid phosphatase (TRAP) staining, decreased expression of osteoclast markers, and associated genes and reduced number of multinuclear cells; in contrast, a miR‐1225 inhibitor or Keap1 overexpression increased this process. In addition, transfection with the miR‐1225 mimic or Keap1 silencing decreased the level of tumour necrosis factor (TNF)α, which was increased after miR‐1225 inhibition and Keap1 overexpression. TNFα overexpression promoted Keap1 depletion–inhibited BMM osteoclastogenesis. Furthermore, reactive oxygen species (ROS) generation that is related to osteoclastogenesis and the Keap‐Nrf2 axis was impaired by the miR‐1225 mimic and Keap1 silencing, whereas it was increased following miR inhibition and overexpression of Keap1 and TNFα. Thus, miR‐1225 inhibits osteoclastogenesis by directly activating the Keap1‐Nrf2‐HO‐1 axis to repress TNFα‐mediated ROS generation.