Outer membrane vesicles of Porphyromonas gingivalis impede bone regeneration by inducing ferroptosis via the Hippo-YAP signaling pathway

Abstract

BACKGROUND: Although increasing evidence confirms that oral microbiota imbalance is a critical factor inhibiting bone regeneration, the specific mechanisms have remained unexplored. This study aims to use periodontitis as a model of oral microbiota imbalance to investigate the specific mechanisms that inhibit bone regeneration in extraction sockets. METHODS: Cone Beam Computed Tomography (CBCT) data of extraction sockets were collected from patients with and without periodontitis to confirm the influence of the periodontitis microenvironment on bone regeneration in extraction sockets. Furthermore, GW4869-pretreated Porphyromonas gingivalis (Pg) and normal Pg were used to build a periodontitis model, and then the bone regeneration in extraction sockets under these conditions was detected by H&E staining, Masson's staining and micro-CT analysis. In vitro, the effect of Pg-derived OMVs on osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) was examined. RNA sequencing, FerroOrange, malondialdehyde assay, transmission electron microscopy, qRT‒PCR, and western blotting analysis were performed. RESULTS: CBCT analysis showed that periodontitis significantly inhibited new bone formation in the extraction sockets in patients. Micro-CT and Histological analysis revealed that inhibiting OMVs released from Pg alleviated the inhibition of bone regeneration in extraction sockets under Pg imbalance. Moreover, Pg-derived OMVs treatment deteriorated bone regeneration in extraction sockets. In vitro, results showed that Pg-derived OMVs inhibited osteogenic differentiation of BMSCs. Furthermore, the results indicated a significant upregulation of ferroptosis in OMVs-treated BMSCs. Notably, targeting ferroptosis promoted osteogenic differentiation of BMSCs and bone regeneration in extraction sockets, as compared with the OMVs-treated group. Mechanistic studies have shown that Pg-derived OMVs promoted BMSCs ferroptosis via the Hippo- Yes-associated protein (YAP) pathway. CONCLUSION: This study shows that a Pg microbiota imbalance inhibits bone regeneration by secreting OMVs from Pg to induce ferroptosis in BMSCs. Mechanically, we illustrated that OMVs induce ferroptosis through the Hippo-YAP pathway. These findings might provide a new insight and potential therapeutic target to promote bone regeneration under oral microbiota imbalance.