Enterococcus faecalis promotes orthodontic tooth movement in mice by M1-like macrophage polarization

Abstract Probiotic-mediated therapy has garnered increasing attention for its potential role in influencing bone remodeling. Recent studies have consistently shown that the microorganisms can play a role in modulating bone reconstruction. In this study, we aim to explore the impact of probiotics on accelerating orthodontic tooth movement (OTM). Potential probiotic candidates will be identified through 16S rRNA gene sequencing in a mouse model of OTM. The relative abundance of Enterococcus faecalis (E. faecalis) increased in the move group. To investigate the osteoimmunomodulatory impact, primary periodontal ligament cells (PDLCs) were obtained from mouse periodontal ligaments and cultured with or without conditioned media (CM) derived from macrophages post-incubation with E. faecalis. The results demonstrated that E. faecalis increased the number of M1-polarized macrophages, and a decreased osteogenic level in PDLCs treated with CM E. faecalis group. Subsequently, the microbiota of the mice has be depleted using broad-spectrum antibiotic mixture (ABX) before being administered with E. faecalis. The distance of OTM have been measured, and the alveolar bone have been analyzed using micro-CT and immunohistochemical staining. This study has explored the potential effects of E. faecalis administration on the OTM process through immunomodulation. We assessed the efficacy of E. faecalis in accelerating tooth movement, and elucidated the mechanisms by which E. faecalis modulate M1-like macrophage polarization to enhance OTM. This research will lead to an acceleration in the duration of orthodontic treatment with minimal interventions, thereby offering significant value and pioneering advancements in orthodontic treatment.