Effect of Porphyromonas gingivalis outer membrane vesicles on renal tubule epithelial-mesenchymal transition.

BACKGROUND Studies have shown that Porphyromonas gingivalis (P. gingivalis) can promote the development of chronic kidney disease (CKD). In this study, we explored the epithelial-mesenchymal transition (EMT) process promoted by P. gingivalis outer membrane vesicles (OMVs) in renal interstitial fibrosis (RIF), thereby providing new ideas for the study of the relationship between periodontitis and CKD. METHODS For in vivo experiments, RIF models induced by unilateral ureteral obstruction (UUO) were constructed in 6-week-old C57BL/6 mice, followed by administration of P. gingivalis OMVs (100 µg) through the tail vein once every other day for 2 weeks. For in vitro experiments, the RIF model was established by transforming growth factor-beta (TGF-β)1-induced mouse renal tubular epithelial cells (RTECs), followed by the administration of 100 µg P. gingivalis OMVs. In vivo imaging system (IVIS) imaging and immunofluorescence were used to detect whether peripheral injection of P. gingivalis OMVs through the tail vein could enter mouse kidney tissue. Serum biochemical assays were performed to detect the renal function of the injected mice. Hematoxylin-eosin (HE) staining and Masson's trichrome staining were used to assess tubulointerstitial lesions and fibrosis. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to detect gene expression levels of cytokines related to renal inflammation and fibrosis. The expression levels of EMT-related proteins in kidney tissue and RTECs were evaluated by immunofluorescence and Western blotting. The expression levels of EMT-related regulatory factors Snail1 and β-catenin in the renal tissues of mice in each group were detected by qRT-PCR and Western blotting. RESULTS P. gingivalis OMVs successfully entered the kidney tissue of the mice via circulation. P. gingivalis OMVs aggravated renal dysfunction, renal tubulointerstitial lesions, and fibrosis in UUO mice. P. gingivalis OMVs upregulated the gene expression of inflammatory and fibrosis-related factors. P. gingivalis OMVs induced renal tubular EMT exacerbation both in vivo and in vitro. P. gingivalis OMVs upregulated gene and protein expression levels of EMT-related regulatory factors such as β-catenin and Snail1. CONCLUSION P. gingivalis OMVs can aggravate renal dysfunction, tubulointerstitial disease, and RIF and may further aggravate EMT by regulating the expression of β-catenin and Snail1. PLAIN LANGUAGE SUMMARY Porphyromonas gingivalis is the main pathogenic factor of periodontitis. Chronic kidney disease (CKD) is a global epidemic that affects about 10% of the world's population. Renal interstitial fibrosis (RIF) is the common pathway of progression from CKD to end-stage kidney disease (ESKD). During the development of RIF, renal tubular epithelial cells (RTECs), as the most vulnerable intrinsic cells of the kidney, can be transformed into myofibroblasts through epithelial-mesenchymal transition (EMT). P. gingivalis outer membrane vesicles (OMVs) can reach deep tissues and activate host inflammatory response. Several studies have shown that P. gingivalis can increase kidney inflammation and immunosuppression through complex mechanisms, induce renal insufficiency, and affect CKD development. However, there are few reports about P. gingivalis OMVs and EMT. Our study found that P. gingivalis OMVs can aggravate renal dysfunction, tubulointerstitial disease, and RIF and may further aggravate EMT by regulating the expression of β-catenin and Snail1. Therefore, this finding provides a new strategy for preventing CKD/EMT from the perspective of treating periodontitis.