Fusobacterium Nucleatum Omvs Regulate Periodontal Inflammation Through Mitochondrial Dynamics Imbalance

The aim of this study was to investigate the underlying mechanisms by which Fusobacterium nucleatum (F. nucleatum) outer membrane vesicles (OMVs) regulate periodontal inflammation through mitochondrial dynamics imbalance. OMVs of F. nucleatum were isolated via ultracentrifugation and characterized. Rat periodontitis models were established using silk ligation and infected with either wild-type Fn, OMV secretion-inhibited Fn, or purified OMVs. Periodontal inflammation progression was assessed by micro-CT, HE staining, and immunohistochemistry. The intracellular trafficking of OMVs in periodontal ligament cells (PDLCs) was visualized by fluorescent labeling. RNA sequencing was performed to analyze alterations in mitochondrial-related genes. Mitochondrial morphology and function were evaluated by transmission electron microscopy, live-cell mitochondrial fluorescence staining, and Western blotting (WB). The expression and distribution of inflammasome components, inflammatory cytokines, and associated pathway proteins were detected via RT-qPCR, ELISA, WB, and immunofluorescence. First, we successfully isolated and characterized OMVs from F. nucleatum. In the ligature-induced periodontitis rat model, inhibition of OMV secretion attenuated Fn pathogenicity, whereas local injection of purified OMVs exacerbated periodontal inflammation. In vitro, internalized OMVs localized to mitochondria in PDLCs, inducing mitochondrial fragmentation. The expression of mitochondrial fission-related proteins increased, while fusion-related proteins decreased, accompanied by reduced mitochondrial membrane potential and elevated reactive oxygen species (ROS). Mitochondrial dysfunction triggered NLRP3 inflammasome activation and upregulated pro-inflammatory cytokine expression. This study elucidates the role and mechanism of F. nucleatum OMVs in periodontitis progression, deepening our understanding of their contribution to periodontal pathogenesis.