Oral Microenvironment Research Articles

Oral dysbiosis initiates periodontal disease in experimental kidney disease.

It is presently unclear why there is a high prevalence of periodontal disease in individuals living with chronic kidney disease (CKD). Whilst some have argued that periodontal disease causes CKD, we hypothesised that alterations in saliva and the oral microenvironment in organisms with kidney disease may initiate periodontal disease by causing dysbiosis of the oral microbiota. Experimental kidney disease was created using adenine feeding and subtotal nephrectomy in rats, and by adenine feeding in mice. Loss of periodontal bone height was assessed using a dissecting microscope supported by micro-CT, light, confocal and electron microscopy, and immunohistochemistry. Salivary biochemistry was assessed using NMR spectroscopy. The oral microbiome was evaluated using culture-based and molecular methods, and the transmissibility of dysbiosis was assessed using co-caging and microbial transfer experiments into previously germ-free recipient mice. We demonstrate that experimental kidney disease causes a reproducible reduction of alveolar bone height, without gingival inflammation or overt hyperparathyroidism but with evidence of failure of bone formation at the periodontal crest. We show that kidney disease alters the biochemical composition of saliva and induces progressive dysbiosis of the oral microbiota, with microbial samples from animals with kidney disease displaying reduced overall bacterial growth, increased alpha diversity, reduced abundance of key components of the healthy oral microbiota such as Streptococcus and Rothia, and an increase in minor taxa including those from gram-negative phyla Proteobacteria and Bacteroidetes. Co-housing diseased rats with healthy ones ameliorates the periodontal disease phenotype, whilst transfer of oral microbiota from mice with kidney disease causes periodontal disease in germ-free animals with normal kidney function. We advocate that periodontal disease should be regarded as a complication of kidney disease, initiated by oral dysbiosis through mechanisms independent of overt inflammation or hyperparathyroidism.

Enterococcus faecalis co-cultured with oral cancer cells exhibits higher virulence and promotes cancer cell survival, proliferation, and migration: an in vitro study.

Introduction. Enterococcus faecalis is a common pathogen associated with many oral diseases and is often isolated from oral cancer patients. However, limited information is available on its key virulence gene expression in oral cancer cell microenvironment and cancer cell behaviour in co-culture studies.Hypothesis. E. faecalis overexpresses virulence genes when co-cultured with oral cancer cells and possibly alters the tumour microenvironment, promoting oral cancer proliferation and survival.Aim. To investigate altered virulence gene expression in E. faecalis and oral cancer cell behaviour using in vitro co-culture experiments.Methodology. Cal27 cells were co-cultured with E. faecalis and assessed for their cell proliferation, apoptosis, migration and clonogenicity using standard cell culture assays. The levels of reactive oxygen species (ROS) and inflammatory cytokines, along with proliferative, angiogenic and apoptotic biomarker expressions, were also assessed. E. faecalis adherence to cancer cells was demonstrated by the gentamicin protection assay. Real time-PCR was used to analyse the expression of virulence genes.Results. Co-culture of Cal27 cells with E. faecalis showed significantly higher cell proliferation, migration and clonogenicity compared to the control (P<0.01). A significant increase in the levels of ROS and inflammatory cytokines and overexpression of Ki67, vascular endothelial growth factor, extracellular signal-regulated kinase 1/2, phosphoinositide 3 kinase and Akt was observed in the co-culture group. E. faecalis also downregulated p53 and Bax genes while upregulated Bcl-2. The virulence genes GelE, Asa and Ace were overexpressed in E. faecalis co-cultured with Cal27 cells.Conclusion. The results from this study indicate the possible risks of E. faecalis infection in oral cancer. An effective antibiotic strategy against E. faecalis to prevent complications associated with oral diseases, including cancer, is needed.

Wearable Multifunctional Hydrogel for Oral Microenvironment Visualized Sensing Coupled with Sonodynamic Bacterial Elimination and Tooth Whitening.

Bacterial-driven dental caries and tooth discoloration are growing concerns as the most common oral health problems. Current diagnostic methods and treatment strategies hardly allow simultaneous early detection and non-invasive treatment of these oral diseases. Herein, a wearable multifunctional double network hydrogel combined with polyaniline and barium titanate (PANI@BTO) nanoparticles is developed for oral microenvironment visualized sensing and sonodynamic therapy. Due to the colorimetric properties of polyaniline, the hydrogel displays a highly sensitive and selective response for visualized sensing of oral acidic microenvironment. Meanwhile, the barium titanate in the hydrogel efficiently generates reactive oxygen species (ROS) under ultrasound irradiation, realizing non-invasive treatment in the oral cavity. Through bacterial elimination experiments and tooth whitening studies, the hydrogel can achieve the dual effect of effectively inhibiting the growth of cariogenic bacteria and degrading tooth surface pigments. Owing to the visualized sensing of the oral acidic microenvironment and efficient sonodynamic therapy function, the proposed hydrogel system offers a solution for the prevention of caries and tooth whitening, which is promising in developing the biomedical system targeting the simultaneous sensing and therapy for oral diseases.

Construction of oral cancer microenvironment model using 3D culture technology and search for new therapeutic targets

There remains much to be discovered and understood about the subtypes of cancer associated-fibroblasts (CAFs) in oral cancer. At the Faculty of Dentistry, Niigata University in Japan, Dr Kenta Haga is investigating the tumour microenvironment and CAFs. To do this, he and his team are using 3D culture technology in their studies as 3D culture models are considered to be more useful and more faithful to the biological characteristics and drug resistance of cancer than 2D cultures. This is because cells are never in 2D in the human body; they are all placed in a 3D structural environment. In their latest study, the researchers utilised their experimental model to recreate the cancer microenvironment and evaluate the proliferation and invasion of cancer cells over time. They have incorporated CAFs into a collagen gel, seeded oral cancer cells and established the basic technology for a 3D culture model with a two-layered structure that has a tumour layer and an interstitial layer to mimic squamous cell carcinoma. The team has been able to investigate the interaction of CAFs with oral cancer cells by in vitro, in vivo and in human oral cancer specimens. In order to understand the complex tumour microenvironment they are seeking to analyse the effects of CAFs on the invasive and proliferative potential for cancer cells. If they can elucidate the intercellular network in the tumour microenvironment, this will lead to novel treatment strategies for cancer. Haga and the team have already demonstrated that the TGF-β/SOX9 pathway plays an important role in CAFs promoting epithelial mesenchymal transition (EMT) in oral cancer.

A 3D in vitro model of biphasic calcium phosphate (BCP) scaffold combined with human osteoblasts, osteoclasts, and endothelial cells as a platform to mimic the oral microenvironment for tissue regeneration

ObjectivesThis study aimed to develop an innovative 3D in vitro model based on the biphasic calcium phosphate (BCP) scaffold combined with human osteoblasts (hOBs), osteoclasts (hOCs), and endothelial cells to evaluate its effects on bone and vascular cells behavior. MethodsTo this end, an optimized mixture of hydroxyapatite (HA) and β-tricalcium phosphate (TCP) with a weight ratio of 30/70 was employed to develop a BCP scaffold using the computer-aided design (CAD) approach. The BCP scaffold was combined with primary cultures of hOBs, hOCs and human umbilical vein endothelial cells (HUVECs). ResultsMorphometric analyses using scanning electron microscopy (SEM) and X-ray micro-computed tomography, along with biomechanical testing, revealed that BCP scaffold exhibited a regular 3D structure with large interconnected internal pores (700 µm) and high mechanical strength. In terms of biological behavior, after 14 days of tri-culture with hOBs, hMCs and HUVECs, SEM, immunofluorescence, and histological analyses showed that all cell types were viable and adhered well to the entire surface of the scaffold. Interestingly, SEM and energy-dispersive X-ray spectroscopy analyses also revealed on the BCP scaffold the presence of mineralized matrix crystals of Ca, P, O and C within a tissue-like cell layer produced by the interaction of the three cell types. ConclusionsData confirmed the high performance of the BCP scaffold through biomechanical studies. Notably, for the first time, this study demonstrated the feasibility of combining BCP scaffold with hOBs, hOCs, and HUVEC, which remained viable and maintained their native phenotypes, creating also tissue-like cell layer. Clinical significanceAlthough further investigation is needed, these results underscore the potential to develop a 3D in vitro model that mimics the oral microenvironment, which could be valuable for BTE approaches in vivo studies.

Antibacterial periodontal ligament stem cells enhance periodontal regeneration and regulate the oral microbiome

BackgroundThe transplantation of periodontal ligament stem cells (PDLSCs) has been shown to enhance periodontal regeneration in animal models and clinical trials. However, it is not known whether PDLSCs are antibacterial and whether this affects oral microbiota and periodontal regeneration.MethodsWe isolated human PDLSCs from periodontal ligament of extracted teeth. Rats’ periodontal fenestration defects were prepared, and treated with PDLSC injections (Cell group), using saline injections (Saline group) as the control. The oral microbiota was explored by 16 S rDNA sequencing and compared with that before surgery (PRE group). The antibacterial property of PDLSCs and its underlying mechanism were tested in vitro.ResultsMicrobiome analyses reveal a decreased biodiversity, a changed community structure, and downregulated community functions of the oral microbiome in the Saline group. PDLSCs injections enhance periodontal regeneration, reverse the decrease in diversity, and increase the abundance of non-pathogenic bacterial Bifidobacterium sp. and Lactobacillus sp., making the oral microbiome similar to that of the PRE group. In vitro, PDLSCs inhibit the growth of Staphylococcus aureus, Escherichia coli, and Fusobacterium nucleatum. The main mechanism of action is postulated to involve production of the cationic antimicrobial peptide LL-37.ConclusionsOur findings reveal that PDLSC injections enhance periodontal regeneration and regulate the oral microbiome to foster an oral cavity microenvironment conducive to symbiotic microbiota associated with health.

Synergistic effects of bacteria, enzymes, and cyclic mechanical stresses on the bond strength of composite restorations

Predicting how tooth and dental material bonds perform in the mouth requires a deep understanding of degrading factors. Yet, this understanding is incomplete, leading to significant uncertainties in designing and evaluating new dental adhesives. The durability of dental bonding interfaces in the oral microenvironment is compromised by bacterial acids, salivary enzymes, and masticatory fatigue. These factors degrade the bond between dental resins and tooth surfaces, making the strength of these bonds difficult to predict. Traditionally studied separately, a combined kinetic analysis of these interactions could enhance our understanding and improvement of dental adhesive durability. To address this issue, we developed and validated an original model to evaluate the bond strength of dental restorations using realistic environments that consider the different mechanical, chemical, and biological degradative challenges working simultaneously: bacteria, salivary esterases, and cyclic loading. We herein describe a comprehensive investigation on dissociating the factors that degrade the bond strength of dental restorations. Our results showed that cariogenic bacteria are the number one factor contributing to the degradation of the bonded interface, followed by cyclic loading and salivary esterases. When tested in combinatorial mode, negative and positive synergies towards the degradation of the interface were observed. Masticatory loads (i.e., cycling loading) enhanced the lactic acid bacterial production and the area occupied by the biofilm at the bonding interface, resulting in more damage at the interface and a reduction of 73 % in bond strength compared to no-degraded samples. Salivary enzymes also produced bond degradation caused by changes in the chemical composition of the resin/adhesive. However, the degradation rates are slowed compared to the bacteria and cyclic loading. These results demonstrate that our synergetic model could guide the design of new dental adhesives for biological applications without laborious trial-and-error experimentation.

16S rRNA based metagenomic analysis unveils unique oral microbial signatures in oral squamous cell carcinoma cases from Coastal Karnataka, India.

Oral Squamous cell carcinoma (OSCC) is the 14th most frequent cancer with 300,000 new cases and 100,000 deaths reported annually. Even with advanced therapy, the treatment outcomes are poor at advanced stages of the disease. The diagnosis of early OSCC is of paramount clinical value given the high mortality rate associated with the late stages of the disease. Recently, the role of microbiome inthedisease manifestation, including oral cancer, has garnered considerable attention. But, to establish the role of bacteria in oral cancer, it is important to determine the differences in the colonization patternin non-tumour and tumour tissues. In this study, 16S rRNA based metagenomic analyses of 13tumorous and contralateral anatomically matched normal tissue biopsies, obtained from patients with advanced stage of OSCC were evaluated to understand the correlation between OSCC and oral microbiome. In this study we identified Fusobacterium, Prevotella, Capnocytophaga, Leptotrichia, Peptostreptococcus, Parvimonas and Bacteroidetes as the most significantly enriched taxa in OSCC lesions compared to the non-cancerous tissues. Further, PICRUSt2 analysis unveiled enhanced expression of metabolic pathways associated with L-lysine fermentation, pyruvate fermentation, and isoleucine biosynthesis in those microbes associated with OSCC tissues. These findings provide valuable insights into the distinctive microbial signatures associated with OSCC, offering potential biomarkers and metabolic pathways underlying OSCC pathogenesis. While our focus has primarily centred onmicrobial signatures, it is essential to recognize the pivotal role of host factors such as immune responses, genetic predisposition, and the oral microenvironment in shaping OSCC development and microbiome composition.

Areca nut-induced metabolic reprogramming and M2 differentiation promote OPMD malignant transformation

BackgroundBetel quid and its major ingredient, areca nut, are recognized by IARC as major risk factors in oral cancer development. Areca nut extract (ANE) exposure has been linked to OPMD progression and malignant transformation to OSCC. However, the detailed mechanism through which ANE acts on other cell types in the oral microenvironment to promote oral carcinogenesis remains elusive.MethodsImmunoprofiling of macrophages associated with OPMD and OSCC was carried out by immunohistochemical and immunofluorescence staining. Phosphokinase and cytokine arrays and western blotting were performed to determine the underlying mechanisms. Transwell assays were used to evaluate the migration-promoting effect of ANE. Hamster model was finally applied to confirm the in vivo effect of ANE.ResultsWe reported that M2 macrophages positively correlated with oral cancer progression. ANE induced M2 macrophage differentiation, CREB phosphorylation and VCAM-1 secretion and increased mitochondrial metabolism. Conditioned medium and VCAM-1 from ANE-treated macrophages promoted migration and mesenchymal phenotypes in oral precancer cells. In vivo studies showed that ANE enhanced M2 polarization and related signaling pathways in the oral buccal tissues of hamsters.ConclusionOur study provides novel mechanisms for areca nut-induced oral carcinogenesis, demonstrating that areca nut promotes M2 macrophage differentiation and secretion of oncogenic cytokines that critically activate malignant transformation of oral premalignant cells.

Exploring the interplay between antiretroviral therapy and the gut-oral microbiome axis in people living with HIV

The gut and oral microbiome is altered in people living with HIV (PLWH). While antiretroviral treatment (ART) is pivotal in restoring immune function in PLWH, several studies have identified an association between specific antiretrovirals, particularly integrase inhibitors (INSTI), and weight gain. In our study, we explored the differences in the oral and gut microbiota of PLWH under different ART regimens, and its correlation to Body Mass Index (BMI). Fecal and salivary samples were collected from PLWH (n = 69) and healthy controls (HC, n = 80). We performed taxonomy analysis to determine the microbial composition and relationship between microbial abundance and ART regimens, BMI, CD4+T-cell count, CD4/CD8 ratio, and ART duration. PLWH showed significantly lower richness compared to HC in both the oral and gut environment. The gut microbiome composition of INSTI-treated individuals was enriched with Faecalibacterium and Bifidobacterium, whereas non-nucleotide reverse transcriptase inhibitor (NNRTI)-treated individuals were enriched with Gordonibacter, Megasphaera, and Staphylococcus. In the oral microenvironment, Veillonella was significantly more abundant in INSTI-treated individuals and Fusobacterium and Alloprevotella in the NNRTI-treated individuals. Furthermore, Bifidobacterium and Dorea were enriched in gut milieu of PLWH with high BMI. Collectively, our findings identify distinct microbial profiles, which are associated with different ART regimens and BMI in PLWH on successful ART, thereby highlighting significant effects of specific antiretrovirals on the microbiome.

Characterizing oral dysplasia immune microenvironment (DIME) using imaging mass cytometry

Characterizing oral dysplasia immune microenvironment (DIME) using imaging mass cytometry

A Microenvironment-Responsive, Controlled Release Hydrogel Delivering Embelin to Promote Bone Repair of Periodontitis via Anti-Infection and Osteo-Immune Modulation.

Periodontitis, a prevalent chronic inflammatory disease, poses significant challenges for effective treatment due to its complex etiology involving specific bacteria and the inflammatory immune microenvironment. Here, this study presents a novel approach for the targeted treatment of periodontitis utilizing the immunomodulatory and antibacterial properties of Embelin, a plant-derived compound, within an injectable hydrogel system. The developed Carboxymethyl Chitosan-Oxidized Dextran (CMCS-OD) hydrogel formed via dynamic chemical bonds exhibited self-healing capabilities and pH-responsive behavior, thereby facilitating the controlled release of Embelin and enhancing its efficacy in a dynamic oral periodontitis microenvironment. This study demonstrates that this hydrogel system effectively prevents bacterial invasion and mitigates excessive immune response activation. Moreover, it precisely modulates macrophage M1/M2 phenotypes and suppresses inflammatory cytokine expression, thereby fostering a conducive environment for bone regeneration and addressing periodontitis-induced bone loss. These findings highlight the potential of the approach as a promising strategy for the clinical management of periodontitis-induced bone destruction.

Oral microbiota of patients with phenylketonuria: A nation-based cross-sectional study.

The oral microenvironment contributes to microbial composition and immune equilibrium. It is considered to be influenced by dietary habits. Phenylketonuria (PKU) patients, who follow a lifelong low-protein diet, exhibit higher prevalence of oral diseases such as periodontitis, offering a suitable model to explore the interplay between diet, oral microbiota and oral health. We conducted 16S rDNA sequencing on saliva and subgingival plaque from 109 PKU patients (ages 6-68 years) and 114 age-matched controls and correlated oral microbial composition and dental health. PKU patients exhibited worse dental health, reduced oral microbial diversity and a difference in the abundance of specific taxa, especially Actinobacteriota species, compared to controls. PKU patients with poor periodontal health exhibited higher alpha diversity than the orally healthy ones, marked by high abundance of the genus Tannerella. Notably, the observed taxonomic differences in PKU patients with normal indices of decayed/missing/filled teeth, plaque control record, gingival bleeding index and periodontal screening and recording index generally differed from microbial signatures of periodontitis. PKU patients' reduced microbial diversity may be due to their diet's metabolic challenges disrupting microbial and immune balance, thus increasing oral inflammation. Higher alpha diversity in PKU patients with oral inflammation is likely related to expanded microbial niches.

Tetracyclic homoisoflavanoid (+)-brazilin: a natural product inhibits c-di-AMP-producing enzyme and Streptococcus mutans biofilms.

The tenacious biofilms formed by Streptococcus mutans are resistant to conventional antibiotics and current treatments. There is a growing need for novel therapeutics that selectively inhibit S. mutans biofilms while preserving the normal oral microenvironment. Previous studies have shown that increased levels of cyclic di-AMP, an important secondary messenger synthesized by diadenylate cyclase (DAC), favored biofilm formation in S. mutans. Thus, targeting S. mutans DAC is a novel strategy to inhibit S. mutans biofilms. We screened a small NCI library of natural products using a fluorescence detection assay. (+)-Brazilin, a tetracyclic homoisoflavanoid found in the heartwood of Caesalpinia sappan, was identified as one of the 11 "hits," with the greatest reduction (>99%) in fluorescence at 100 µM. The smDAC inhibitory profiles of the 11 "hits" established by a quantitative high-performance liquid chromatography assay revealed that (+)-brazilin had the most enzymatic inhibitory activity (87% at 100 µM) and was further studied to determine its half maximal inhibitory concentration (IC50 = 25.1 ± 0.98 µM). (+)-Brazilin non-competitively inhibits smDAC's enzymatic activity (Ki = 140.0 ± 27.13 µM), as determined by a steady-state Michaelis-Menten kinetics assay. In addition, (+)-brazilin's binding profile with smDAC (Kd = 11.87 µM) was illustrated by a tyrosine intrinsic fluorescence quenching assay. Furthermore, at low micromolar concentrations, (+)-brazilin selectively inhibited the biofilm of S. mutans (IC50 = 21.0 ± 0.60 µM) and other oral bacteria. S. mutans biofilms were inhibited by a factor of 105 in colony-forming units when treated with 50 µM (+)-brazilin. In addition, a significant dose-dependent reduction in extracellular DNA and glucan levels was evident by fluorescence microscopy imaging of S. mutans biofilms exposed to different concentrations of (+)-brazilin. Furthermore, colonization of S. mutans on a representative model of enamel using suspended hydroxyapatite discs showed a >90% reduction with 50 µM (+)-brazilin. In summary, we have identified a drug-like natural product inhibitor of S. mutans biofilm that not only binds to smDAC but can also inhibit the function of smDAC. (+)-Brazilin could be a good candidate for further development as a potent therapeutic for the prevention and treatment of dental caries.IMPORTANCEThis study represents a significant advancement in our understanding of potential therapeutic options for combating cariogenic biofilms produced by Streptococcus mutans. The research delves into the use of (+)-brazilin, a natural product, as a potent inhibitor of Streptococcus mutans' diadenylate cyclase (smDAC), an enzyme crucial in the formation of biofilms. The study establishes (+)-brazilin as a non-competitive inhibitor of smDAC while providing initial insights into its binding mechanism. What makes this finding even more promising is that (+)-brazilin does not limit its inhibitory effects to S. mutans alone. Instead, it demonstrates efficacy in hindering biofilms in other oral bacteria as well. The broader spectrum of anti-biofilm activity suggests that (+)-brazilin could potentially serve as a versatile tool in a natural product-based treatment for combating a range of conditions caused by resilient biofilms.

Periodontal tissue regeneration: current therapeutic strategies and future directions in further research

Chronic and progressive destruction/damage of the periodontal tissues resulted from periodontitis is the leading cause of tooth loss in adults. Traditional periodontal therapies such as scaling and root planning or flap surgery have demonstrated effective in controlling local inflammation and in suppressing/arresting the disease progression of periodontitis. However, those infection control measures cannot help to regenerate lost periodontal tissues to a statistically or clinically significant degree. Although some successes regarding the reduction of the intrabony defect and maintenance of the periodontal homeostasis have been achieved in periodontal regenerative procedures, comprising but not limited to guided tissue regeneration (GTR) or bone grafting technique, the restorative effectiveness of the architecture and function of the lost or injured tissues is far from our clinical expectation. The use of the concept, technique, and method of tissue engineering for periodontal regeneration is a hotspot and animal studies have shown interesting outcomes in terms of functional regeneration of lost/damaged support tissues in the periodontium, including alveolar bone, periodontal ligament, and cementum. However, numerous issues need to be addressed before those regenerative approaches can be responsibly transformed to novel clinical therapies. Recently, paradigm that induces homing of host stem cells to site of the periodontium and encourage the body's innate capability to repair is a new research field termed endogenous regeneration. Given that endogenous regenerative technique avoids ex-vivo cell culture and transplantation, it should be relatively easier to be used in the treatment of clinical patients. Due to the limited oral microenvironment and harsh periodontal local condition for tissue regeneration, as well as poor understanding of periodontal regenerative biology, there is still a long way ahead to explore new effective, practical, and economical therapies to save and protect natural tooth and for combating highly prevalent periodontal disease.

Candida albicans-myeloid cells-T lymphocytes axis in the tumor microenvironment of oral tumor-bearing mice

Candida albicans (C. albicans) is associated with the development of oral cancer. Here, we report the altered tumor microenvironment in oral tumor-bearing mice caused by C. albicans infection. Single-cell RNA sequencing showed that C. albicans infection influenced the tumor microenvironment significantly. Specifically, C. albicans infection reduced the CD8+ T cells but increased the IL-17A+ CD4+ T cells and IL-17A+ γδ T cells in oral tumor. The neutralization of IL-17A or TCR γ/δ alleviated the tumor progression caused by C. albicans infection. Additionally, C. albicans infection promoted the infiltration of myeloid-derived suppressor cells (MDSCs) into tumor, especially polymorphonuclear (PMN)-MDSCs, which infiltration was reduced after the neutralization of CCL2. Thus, our findings reveal the myeloid cells-T lymphocytes axis in oral tumor microenvironment with C. albicans infection, which helps to understand the mechanisms for C. albicans promoting oral cancer from the perspective of immune microenvironment.

Quercetin in the Prevention of Induced Periodontal Disease in Animal Models: A Systematic Review and Meta-Analysis.

Periodontitis is an inflammatory condition initiated by oral bacteria and is associated with several systemic diseases. Quercetin is an anti-inflammatory and anti-bacterial poly-phenol present in various foods. The aim of this meta-analysis was the evaluation of the effects of quercetin administration in animal models of experimental periodontitis. A systematic search was performed in electronic databases using the following search terms: "periodontitis" or "periodontal disease" or "gingivitis" and "quercetin" or "cyanidanol" or "sophoretin" or "pentahydroxyflavone". In vivo preclinical animal models of experimental periodontal disease with a measurement of alveolar bone loss were included in the analysis. The risk of bias of the included studies was assessed using the SYRCLE tool. The systematic search yielded 335 results. Five studies were included, four of them qualified for a meta-analysis. The meta-analysis showed that quercetin administration decreased alveolar bone loss (τ2 = 0.31, 1.88 mm 95%CI: 1.09, 2.67) in experimental periodontal disease animal models. However, the risk of bias assessment indicated that four SYRCLE domains had a high risk of bias. Quercetin diminishes periodontal bone loss and prevents disease progression in animal models of experimental periodontal disease. Quercetin might facilitate periodontal tissue hemostasis by reducing senescent cells, decreasing oxidative stress via SIRT1-induced autophagy, limiting inflammation, and fostering an oral bacterial microenvironment of symbiotic microbiota associated with oral health. Future research will show whether and how the promising preclinical results can be translated into the clinical treatment of periodontal disease.

A comprehensive review of oral microenvironment changes and orofacial adverse reactions after COVID-19 vaccination: The good, the bad, and the ugly.

Anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines have the potential to alter several biological systems concurrently with remolding the immune system, most of which are related to immunization, while some others are known as adverse effects. This review aims to explore the potential effects of vaccination on the oral microenvironment and classifies them as good, bad, or ugly, with a brief review of facial diseases following coronavirus disease 2019 (COVID-19) vaccination. This study was a comprehensive review conducted through searching related articles in Medline, Scopus, and Google Scholar databases. On one side, the "Good" impacts of vaccination on the oro-nasal mucosa are explained as if the mucosal immune responses followed by SARS-CoV-2 vaccines are enough to provide immunity. On the other side, the possible "Bad" and "Ugly" effects of the vaccine, which manifest as orofacial adverse events and autoimmune reactivations, respectively, should be noted. Exacerbation of pre-existing autoimmune conditions such as lichen planus, pemphigus vulgaris, bullous pemphigoid, and Stevens-Johnson syndrome have been reported. COVID-19 vaccines could affect different biological systems alongside stimulating the immune system, and some of these effects are referred to as adverse effects. Nonetheless, these adverse effects are treatable, and healthcare professionals should not prevent patients from taking the first available vaccination.

New insights into the role of the oral leukoplakia microenvironment in malignant transformation.

Oral leukoplakia is the most frequent and potentially malignant lesion of the oral cavity. Although dysplasia grading remains the main factor for risk assessment, challenges persist in determining the exact risk of transformation, and the literature has focused on studying alternative biomarkers. The interaction between dysplastic epithelial cells and the microenvironment starts early, and the communication is mainly mediated by lymphocytes, inflammatory factors, fibroblasts, and the extracellular matrix, leading to dysplastic progression. Leukoplakia-infiltrating leukocytes (LILs) and leukoplakia-associated fibroblasts (LAFs) play crucial roles in the dysplastic microenvironment. The immune response is related to intraepithelial T lymphocyte infiltration, mechanisms of immunosuppression coordinated by regulatory T cells, M2 macrophage polarization, and increased numbers of Langerhans cells; in contrast, fibroblastic and extracellular matrix factors are associated with increased numbers of pro-tumorigenic myofibroblasts, increased expression of metalloproteinases vs. decreased expression of TIMPs, and increased expression of chemokines and other inflammatory mediators. The microenvironment offers insights into the progression of leukoplakia to carcinoma, and understanding the complexity of the oral microenvironment in potentially malignant diseases aids in determining the risk of malignant transformation and proposing new therapeutic alternatives.

P1204 Oral Streptococcus mutans isolates aggravated colitis in mice

Abstract Background The incidence of inflammatory bowel disease (IBD) is increasing year by year and the mechanism is unclear. A great number of studies have shown that the gut microbiota composition of IBD patients has changed and the diversity of gut microbiota decreases. The abundance of firmicutes decreases, and the abundance of Proteobacteria increases, which eventually leads to the immune disorders and intestinal inflammation. The mouth is the "gateway" of the digestive tract, which has various microbiota. The entry of extraneous microbiota from the mouth into the intestines play an important role in influencing the composition of the gut microbiota. The continuous disorder of the oral microenvironment (such as periodontitis and dental caries) are also closely related to intestinal inflammation. Methods A series of in vivo and in vitro experiments were conducted to investigate the effect and mechanism of S. mutans on colitis mice. Results S.mutans strain UA159 which is closely related to dental caries significantly aggravated colitis in DSS induced mice, as shown by body weight loss, shorter colon length, and increased inflammatory histological scores (Fig1A). UA159 up-regulated intestinal pro-inflammatory cytokines and inhibited the expression of barrier molecules in DSS mice (Fig1B). The proportion of adaptive immune cells (Th1, Th17) was up-regulated in intestinal lamina propria of UA159-administered mice (Fig1C-D).The fecal microbiota composition of UA159 mice was different from control group. The pro-inflammatory effects of UA159 on DSS mice disappeared when antibiotics were used to eliminate the intestinal microbiota. It is suggested that S.mutans may play a proinflammatory role by influencing the intestinal microbiota of mice (Fig1E). We followed 55 IBD patients for more than 1 year and found that IBD patients with poor control had a higher proportion of S.mutans in saliva (Fig1F). S.mutans strains were isolated from IBD saliva samples and were found to cluster in different branches in the phylogenetic tree (Fig1G). S.mutans isolates have different pro-inflammatory effects on colitis mice and intestinal epithelial cells (Fig1H-I). Subsequent experiments are under way to further explore the mechanism leading to the differences of the pro-inflammatory effects. Conclusion Our study were the first to find that oral S.mutans has aggravated intestinal inflammation. S.mutans UA159 aggravated colitis in mice through damaging intestinal mucosal barrier function, enhancing immune response and disrupting intestinal microbiota (Fig1J). The difference in pro-inflammatory effect of S.mutans derived from different IBD patients saliva may be related to the individual clinical outcome.