MicroRNA-125a-5p modulates macrophage polarization by targeting E26 transformation-specific variant 6 gene during orthodontic tooth movement

•MiR-125a-5p is upregulated under orthodontic force.•MiR-125a-5p is a negative regulator of M1 macrophage polarization.•MiR-125a-5p facilitates the generation of M2 macrophage polarization.•E26 transformation-specific variant 6 is a target of miR-125a-5p.•MiR-125a-5p affects macrophage polarization by E26 transformation-specific variant 6. The aim of this study was to investigate the role of microRNA-125a-5p (miR-125a-5p) in macrophages during orthodontic tooth movement (OTM). Periodontal ligament tissues were collected from patients underwent OTM. Periodontal ligament cells were isolated from periodontal ligament tissues. Periodontal ligament stem cells were isolated from normal human impacted third molars. The miR-125-5p levels were measured by real-time quantitative polymerase chain reaction. The impact of miR-125-5p on macrophage polarization was tested by alizarin red staining assay. The effects of miR-125-5p and E26 transformation-specific variant 6 gene (ETV6) on M1/M2 macrophages phenotype markers were determined by real-time quantitative polymerase chain reaction, western blot, and flow cytometry analyses. The interaction between miR-125-5p and ETV6 was verified using luciferase reporter and RNA immunoprecipitation assays. Periodontal miR-125a-5p was upregulated under the force. Macrophage polarization facilitated osteogenesis by cocultured system. Moreover, miR-125a-5p was upregulated in macrophages polarized with M2 conditions. MiR-125a-5p downregulation promoted the expression of M1 phenotype markers, while suppressed the expression of M2 markers. Mechanistically, ETV6 was confirmed to be a target of miR-125a-5p. ETV6 overexpression increased the expression of M1 polarized markers, while decreased the expression of M2 polarized markers. Furthermore, ETV6 knockdown reversed the effects of miR-125a-5p inhibitor on both M1 macrophages and M2 macrophages. Overall, miR-125a-5p facilitates bone healing by targeting ETV6 to promote macrophage M2 polarization.