Roles of B-cell lymphoma 6 in orthodontic tooth movement of rat molars.

INTRODUCTION: B-cell lymphoma 6 (Bcl6) inhibits osteoclast differentiation in vitro; however, its role in orthodontic tooth movement (OTM) remains unclear. This study aimed to investigate the role of Bcl6 in OTM of rat molars. MATERIALS AND METHODS: OTM was performed on the maxillary first molars of male rats using nickel-titanium coil springs (25 gf) for 14 days with or without local injection of FX1 (50 mg/kg), a Bcl6 inhibitor (n = 10 per group). Micro-computed tomography (CT) images were used to analyse OTM distance and bone morphometric parameters. Immunohistochemistry (IHC) determined Bcl6 expression and tartrate-resistant acid phosphatase staining (TRAP) staining assessed osteoclast differentiation. TRAP staining, and reverse transcription-quantitative polymerase chain reaction determined the effect of FX1 (1 muM) on in vitro rat osteoclast differentiation. The effect of FX1 on cell proliferation and Smad4 expression in periodontal ligament (PDL) cells was determined. RESULTS: Administration of FX1 significantly increased OTM distance and decreased the bone/tissue volume compared with vehicle treatment. IHC staining showed that the vehicle-OTM group had higher expression of Bcl6 than the FX1-OTM group. The number of osteoclasts on the compression side was significantly higher in the FX1-OTM group than that in the vehicle-OTM group. FX1 enhanced osteoclast differentiation and expression of Nfatc1, Dc-stamp, and Ctsk mRNA in osteoclasts in vitro. FX1 significantly promotes PDL cell proliferation in vivo and in vitro. LIMITATIONS: We evaluated only 14 days of OTM. CONCLUSIONS: Bcl6 may play an important role in OTM via modulation of osteoclast differentiation and PDL cell proliferation.