MicroRNA‐21 Promotes Orthodontic Tooth Movement by Modulating the RANKL/OPG Balance in T Cells

OBJECTIVES: The present study was designed to investigate the effects of microRNA-21 (miR-21) on orthodontic tooth movement. METHODS: The orthodontic tooth movement model was established in C57BL/6 and miR-21(-/-) mice with or without implantation of activated T cells. Histological and histomorphometrical analyses were performed by hematoxylin-eosin staining. Tartrate-resistant acid phosphate staining was used to analyze the osteoclast numbers during tooth movement. Enzyme-linked immunosorbent assay, reverse transcription polymerase chain reaction, and immunohistochemistry analysis were used to examine the expression of RANKL and OPG. RESULTS: In miR-21(-/-) mice, the distance of tooth movement was retarded, the osteoclast number was decreased, and serum RANKL expression was strongly reduced. MiR-21 promoted the secretion of RANKL from activated T cells. Furthermore, activated T cells could partially rescue the decreased orthodontic tooth movement distance in miR-21(-/-) mice. MiR-21 was shown to promote orthodontic tooth movement by modulating the RANKL/OPG balance in T cells. CONCLUSIONS: The impact of miR-21 on tooth movement was better elucidated, furthering our understanding of its role and clinical applications in orthodontics.