Arthritis-induced alveolar bone loss is associated with changes in the composition of oral microbiota

Biology of tongue coating in different disease stages of RA and its value in disease progression

OBJECTIVE

To assess and compare the composition of tongue coating microbiota among patients at different stages of rheumatoid arthritis (RA).

METHODS

A total of 47 patients diagnosed with RA, as per the American College of Rheumatology criteria, and 10 healthy individuals were enrolled in this study. The RA patients were stratified considering their Disease Activity Score 28 (DAS28), a composite measure based on the 28 tender and swollen joint count and erythrocyte sedimentation rate (ESR). The study population was further categorized into active phase group (LMH group) and inactive phase group (RE group) according to their DAS28 values. DNA extraction was extracted from tongue coating samples. Subsequently, the V3-V4 16S rDNA region was selectively amplified and sequenced through high-throughput 16S rDNA analysis. The resulting data were then utilized to ascertain the microbial contents.

RESULTS

Significant variations were observed in the tongue coating microbiota of patients with RA during active and inactive phases, in comparison to healthy individuals (p < 0.05). At the genus level, the presence of Prevotellan, Veillonella, Rothia, and Neisseria in RA patients was notably more evident than in the healthy control (HC) group. These disparities find support in existing research on gut and oral microbiota. During the active phase of RA, the relative abundance of Veillonella, Rothia, and Neisseria in the tongue coating microbiota of patients was significantly higher than in those with inactive RA. These findings underscore the need for further and in-depth research on the potential impact of these microorganisms on the progression of RA disease.

CONCLUSION

The results substantiate the hypothesis that tongue coating microbes actively contribute to the progression of RA.

The impact of arthritogenic viruses in oral tissues

Arthritis and periodontitis are inflammatory diseases that share several immunopathogenic features. The expansion in the study of virus-induced arthritis has shed light on how this condition could impact other parts of the human body, including the mouth. Viral arthritis is an inflammatory joint disease caused by several viruses, most notably the alphaviruses Chikungunya virus (CHIKV), Sindbis virus (SINV), Ross River virus (RRV), Mayaro virus (MAYV), and O'nyong'nyong virus (ONNV). These viruses can induce an upsurge of matrix metalloproteinases and immune-inflammatory mediators such as Interleukin-6 (IL6), IL-1β, tumor necrosis factor, chemokine ligand 2, and receptor activator of nuclear factor kappa-B ligand in the joint and serum of infected individuals. This can lead to the influx of inflammatory cells to the joints and associated muscles as well as osteoclast activation and differentiation, culminating in clinical signs of swelling, pain, and bone resorption. Moreover, several data indicate that these viral infections can affect other sites of the body, including the mouth. The human oral cavity is a rich and diverse microbial ecosystem, and viral infection can disrupt the balance of microbial species, causing local dysbiosis. Such events can result in oral mucosal damage and gingival bleeding, which are indicative of periodontitis. Additionally, infection by RRV, CHIKV, SINV, MAYV, or ONNV can trigger the formation of osteoclasts and upregulate pro-osteoclastogenic inflammatory mediators, interfering with osteoclast activation. As a result, these viruses may be linked to systemic conditions, including oral manifestations. Therefore, this review focuses on the involvement of alphavirus infections in joint and oral health, acting as potential agents associated with oral mucosal inflammation and alveolar bone loss. The findings of this review demonstrate how alphavirus infections could be linked to the comorbidity between arthritis and periodontitis and may provide a better understanding of potential therapeutic management for both conditions.

Can metagenomics unravel the impact of oral bacteriome in human diseases?

Oral microbial ecosystems are vital in maintaining the health of the oral cavity and the entire body. Oral microbiota is associated with the progression of oral diseases such as dental caries, periodontal diseases, head and neck cancer, and several systemic diseases such as cardiovascular disease, rheumatoid arthritis, adverse pregnancy outcomes, diabetes, lung infection, colorectal cancer, and pancreatic cancer. Buccal mucosa, tongue dorsum, hard palate, saliva, palatine tonsils, throat, keratinized gingiva, supra-gingival plaque, subgingival plaque, dentures, and lips are microbial habitats of the oral cavity. Porphyromonas gingivalis may have a role in the development of periodontal diseases, oral cancer, diabetes, and atherosclerotic disease. Fusobacterium nucleatum showed a higher abundance in periodontal diseases, oral and colon cancer, adverse pregnancy outcomes, diabetes, and rheumatoid arthritis. The higher abundance of Prevotella intermedia is typical in periodontal diseases, rheumatoid arthritis, and adverse pregnancy outcome. S. salivarius displayed higher abundance in both dental caries and OSCC. Oral bacteria may influence systemic diseases through inflammation by releasing pro inflammatory cytokines. Identification of oral bacteria using culture-dependent approaches and next-generation sequencing-based metagenomic approaches is believed to significantly identify the therapeutic targets and non-invasive diagnostic indicators in different human diseases. Oral bacteria in saliva could be exploited as a non-invasive diagnostic indicator for the early detection of oral and systemic disorders. Other therapeutic approaches such as the use of probiotics, green tea polyphenol, cold atmospheric plasma (CAP) therapy, antimicrobial photodynamic therapy, and antimicrobial peptides are used to inhibit the growth of biofilm formation by oral bacteria.

Methotrexate promotes recovery of arthritis-induced alveolar bone loss and modifies the composition of the oral-gut microbiota

OBJECTIVES

The impact of rheumatoid arthritis (RA) on the shaping of the oral and gut microbiome raises the question of whether and how RA treatment modifies microbial communities. We examined changes in the oral and gut microbiota in a mouse model of antigen-induced arthritis (AIA) treated or not with methotrexate (MTX).

METHODS

Maxillae and stools were evaluated by the MiSeq platform of the V4 region of the 16S rRNA gene. Alveolar bone parameters were analysed by micro-computed tomography. Moreover, arthritis-induced changes in hyperalgesia and oedema were assessed, along with the impact on periodontal bone health.

RESULTS

Microbial communities in MTX-treated AIA mice revealed distinct clusters compared to the control and AIA groups. Overall, MTX impacted the richness and variability of microorganisms in the oral-gut axis microbiome at the phylum level. Regarding the oral microbiome, while in the control group the most dominant phylum was Firmicutes, in the AIA group there was a shift towards the predominance of Campilobacteriota and Bacteroidetes associated with the disease. MTX treatment led to greater dominance of the health-associated phylum Proteobacteria. In the gut microbiome, AIA induction resulted in increased abundance of the Verrucomicrobiota phylum, and MTX treatment restored its levels compared to control. Importantly, the MTX-treated AIA animals had significantly less periodontal bone loss, as well as decreased hyperalgesia and joint oedema compared to the AIA animals.

CONCLUSION

Data suggest the benefit of MTX treatment in protecting alveolar bone, in addition to providing new insights on the drug-microbiome interaction in the course of RA.

Periodontitis and rheumatoid arthritis: What have we learned about their connection and their treatment?

Rheumatoid arthritis and periodontitis are chronic inflammatory diseases defined respectively by the destruction of the articular cartilage and tooth-supporting periodontal tissues. Although the epidemiologic evidence for an association between these two diseases is still scarce, there is emerging scientific information linking specific bacterial periodontal pathogens, such as Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, in the citrullination process, leading to autoantibody formation and compromised immunotolerance of the susceptible patient to rheumatoid arthritis. In this review, we update the existing information on the evidence, not only regarding the epidemiologic association, but also the biologic mechanisms linking these two diseases. Finally, we review information emerging from intervention studies evaluating whether periodontal treatment could influence the initiation and progression of rheumatoid arthritis.

Exploring the Oral Microbiome in Rheumatic Diseases, State of Art and Future Prospective in Personalized Medicine with an AI Approach

The oral microbiome is receiving growing interest from the scientific community, as the mouth is the gateway for numerous potential etiopathogenetic factors in different diseases. In addition, the progression of niches from the mouth to the gut, defined as "oral-gut microbiome axis", affects several pathologies, as rheumatic diseases. Notably, rheumatic disorders (RDs) are conditions causing chronic, often intermittent pain affecting the joints or connective tissue. In this review, we examine evidence which supports a role for the oral microbiome in the etiology and progression of various RDs, including rheumatoid arthritis (RA), Sjogren's syndrome (SS), and systemic lupus erythematosus (SLE). In addition, we address the most recent studies endorsing the oral microbiome as promising diagnostic biomarkers for RDs. Lastly, we introduce the concepts of artificial intelligence (AI), in particular, machine learning (ML) and their general application for understanding the link between oral microbiota and rheumatic diseases, speculating the application of a possible AI approach-based that can be applied to personalized medicine in the future.

Impact of systemic factors in shaping the periodontal microbiome

Since 2010, next-generation sequencing platforms have laid the foundation to an exciting phase of discovery in oral microbiology as it relates to oral and systemic health and disease. Next-generation sequencing has allowed large-scale oral microbial surveys, based on informative marker genes, such as 16S ribosomal RNA, community gene inventories (metagenomics), and functional analyses (metatranscriptomics), to be undertaken. More specifically, the availability of next-generation sequencing has also paved the way for studying, in greater depth and breadth, the effect of systemic factors on the periodontal microbiome. It was natural to investigate systemic diseases, such as diabetes, in such studies, along with systemic conditions or states, , pregnancy, menopause, stress, rheumatoid arthritis, and systemic lupus erythematosus. In addition, in recent years, the relevance of systemic "variables" (ie, factors that are not necessarily diseases or conditions, but may modulate the periodontal microbiome) has been explored in detail. These include ethnicity and genetics. In the present manuscript, we describe and elaborate on the new and confirmatory findings unveiled by next-generation sequencing as it pertains to systemic factors that may shape the periodontal microbiome. We also explore the systemic and mechanistic basis for such modulation and highlight the importance of those relationships in the management and treatment of patients.

Structural and functional changes of gut microbiota in ovariectomized rats and their correlations with altered bone mass

As a critical factor involved in the maintenance of physiological homeostasis, the gut microbiota (GM) reportedly plays a key role in bone development. To date, the association between the GM and steroid deficiency-induced osteoporosis remains poorly understood. Forty female Sprague Dawley rats were divided into an ovariectomy (OVX) or control group. We performed 16S rRNA and metagenome sequencing, to compare diversity, taxonomic differences, and functional genes. The GM composition did not change in the control group and the number of operational taxonomic units increased significantly following ovariectomy. Alpha diversity, determined by ACE estimator, CHAO estimator, the Shannon index, and the Simpson index showed an increasing trend after ovariectomy. Samples in the OVX group were well clustered both pre- and post-ovariectomy, as demonstrated by principal coordinate 1 (PC1) and PC2. Functional genes of GM, including those involved in synthesis and metabolism of carbohydrates and nucleotides, microbial structure, and heme, as well as hemin uptake and utilization, increased at the early stage of osteoporosis. We observed that Ruminococcus flavefaciens exhibited the greatest variation in abundance among the GM and this was also associated with osteoclastic indicators and the estrobolome. Specific changes in fecal microbiota are associated with the pathogenesis of steroid deficiency-induced osteoporosis.

Salivary microbiota and inflammation-related proteins in patients with psoriasis

Objective

The purpose of the present study was to characterize the composition of the salivary microbiota and quantify salivary levels of inflammation‐related proteins (neutrophil gelatinase‐associated lipocalin [NGAL] and transferrin) in patients with psoriasis and compare data to those obtained in patients with periodontitis and orally healthy controls, respectively.

Materials and methods

Stimulated saliva samples from patients with psoriasis (n = 27), patients with periodontitis (n = 58), and orally healthy controls (n = 52) were characterized by means of next‐generation sequencing of the 16S rRNA gene. Salivary levels of NGAL and transferrin were quantified using immunoassays.

Results

Linear discriminant effect size analysis showed that 52 (22 psoriasis‐associated and 30 periodontitis‐associated) and 21 (8 psoriasis‐associated and 13 orally healthy control‐associated) bacterial taxa differentiated the salivary microbiota in patients with psoriasis from that of patients with periodontitis and orally healthy controls, respectively. Significantly lower mean salivary levels of NGAL (psoriasis: 996 [std. error 320], periodontitis: 2,072 [295], orally healthy controls: 2,551 [345] ng/ml, p < .0001) and transferrin (psoriasis: 4.37 [0.92], periodontitis: 7.25 [0.88], orally healthy controls: 10.02 [0.94] ng/ml, p < .0001) were identified in patients with psoriasis.

Conclusions

Psoriasis associates with characteristics of the salivary microbiota and salivary levels of inflammation‐related proteins, which are different from characteristics in patients with periodontitis and orally healthy controls, respectively.

Host-Microbial Interactions in Systemic Lupus Erythematosus and Periodontitis

Background: Systemic lupus erythematosus (SLE) is a potentially fatal complex autoimmune disease, that is characterized by widespread inflammation manifesting tissue damage and comorbidities across the human body including heart, blood vessels, joints, skin, liver, kidneys, and periodontal tissues. The etiology of SLE is partially attributed to a deregulated inflammatory response to microbial dysbiosis and environmental changes. In the mouth, periodontal environment provides an optimal niche for local and systemic inflammation. Our aim was to evaluate the reciprocal impact of periodontal subgingival microbiome on SLE systemic inflammation. Methods: Ninety-one female subjects were recruited, including healthy (n = 31), SLE-inactive (n = 29), and SLE-active (n = 31). Patients were screened for probing depth, bleeding on probing, clinical attachment level, and classified according to CDC/AAP criteria with or without periodontal dysbiosis. Serum inflammatory cytokines were measured by human cytokine panel and a targeted pathogenic subgingival biofilm panel was examined by DNA-DNA checkerboard from subgingival plaque samples. Results: The results showed significant upregulation of serum proinflammatory cytokines in individuals with SLE when compared to controls. Stratification of subject's into SLE-inactive (I) and SLE-active (A) phenotypes or periodontitis and non-periodontitis groups provided new insights into SLE pathophysiology. Ten proinflammatory cytokines were upregulated in serum of SLE-I only and one in SLE-A only. Four molecules overlapped in SLE-A and SLE-I. Anti-inflammatory cytokines included IL-4 IL-10, which were upregulated in SLE-I sera (but not SLE-A), controlling clinical phenotypes. Out of 24 significant differential oral microbial abundances found in SLE, 14 unique subgingival bacteria profiles were found to be elevated in SLE. The most severe oral pathogens (Treponema denticola and Tannerella forsythia) showed increase abundances on SLE-A periodontal sites when compared to SLE-I and healthy controls. Inflammation as measured by cytokine-microbial correlations showed that periodontal pathogens dominating the environment increased proinflammatory cytokines systemically. Conclusions: Altogether, low-grade systemic inflammation that influenced SLE disease activity and severity was correlated to dysbiotic changes of the oral microbiota present in periodontal diseases.

Linkage of Periodontitis and Rheumatoid Arthritis: Current Evidence and Potential Biological Interactions

The association between rheumatoid arthritis (RA) and periodontal disease (PD) has been the focus of numerous investigations driven by their common pathological features. RA is an autoimmune disease characterized by chronic inflammation, the production of anti-citrullinated proteins antibodies (ACPA) leading to synovial joint inflammation and destruction. PD is a chronic inflammatory condition associated with a dysbiotic microbial biofilm affecting the supporting tissues around the teeth leading to the destruction of mineralized and non-mineralized connective tissues. Chronic inflammation associated with both RA and PD is similar in the predominant adaptive immune phenotype, in the imbalance between pro- and anti-inflammatory cytokines and in the role of smoking and genetic background as risk factors. Structural damage that occurs in consequence of chronic inflammation is the ultimate cause of loss of function and disability observed with the progression of RA and PD. Interestingly, the periodontal pathogen Porphyromonas gingivalis has been implicated in the generation of ACPA in RA patients, suggesting a direct biological intersection between PD and RA. However, more studies are warranted to confirm this link, elucidate potential mechanisms involved, and ascertain temporal associations between RA and PD. This review is mainly focused on recent clinical and translational research intends to discuss and provide an overview of the relationship between RA and PD, exploring the similarities in the immune-pathological aspects and the possible mechanisms linking the development and progression of both diseases. In addition, the current available treatments targeting both RA and PD were revised.

Oral microbial dysbiosis linked to worsened periodontal condition in rheumatoid arthritis patients

Rheumatoid arthritis (RA) is an autoimmune disease characterized by joint inflammation. Individuals with RA have a higher risk of periodontitis and periodontitis has been linked to RA through the production of enzymes by periodontal pathogens that citrullinate proteins. This linkage is supported by findings that periodontitis is associated with increased RA severity and treatment of periodontitis can improve the symptoms of RA. The possible mechanism for this association is through dysbiosis of the oral microbiota triggered by RA-induced systemic inflammation. We examined the RA status of subjects by measuring the number of tender and swollen joints, anti-citrullinated protein antibody and rheumatoid factor. Periodontal disease status and salivary cytokine levels were measured, and dental plaque analyzed by 16S rRNA high throughput sequencing. RA patients had a higher bacterial load, a more diverse microbiota, an increase in bacterial species associated with periodontal disease, more clinical attachment loss, and increased production of inflammatory mediators including IL-17, IL-2, TNF, and IFN-γ. Furthermore, changes in the oral microbiota were linked to worse RA conditions. Our study provides new insights into the bi-directional relationship between periodontitis and RA and suggest that monitoring the periodontal health of RA patients is particularly important.

The Oral Microbiota Is Modified by Systemic Diseases

Periodontal diseases are initiated by bacteria that accumulate in a biofilm on the tooth surface and affect the adjacent periodontal tissue. Systemic diseases such as diabetes, rheumatoid arthritis (RA), and systemic lupus erythematosus (SLE) increase susceptibility to destructive periodontal diseases. In human studies and in animal models, these diseases have been shown to enhance inflammation in the periodontium and increase the risk or severity of periodontitis. All 3 systemic diseases are linked to a decrease in bacterial taxa associated with health and an increase in taxa associated with disease. Although there is controversy regarding the specific oral bacterial changes associated with each disease, it has been reported that diabetes increases the levels of Capnocytophaga, Porphyromonas, and Pseudomonas, while Prevotella and Selenomonas are increased in RA and Selenomonas, Leptotrichia, and Prevotella in SLE. In an animal model, diabetes increased the pathogenicity of the oral microbiome, as shown by increased inflammation, osteoclastogenesis, and periodontal bone loss when transferred to normal germ-free hosts. Moreover, in diabetic animals, the increased pathogenicity could be substantially reversed by inhibition of IL-17, indicating that host inflammation altered the microbial pathogenicity. Increased IL-17 has also been shown in SLE, RA, and leukocyte adhesion deficiency and may contribute to oral microbial changes in these diseases. Successful RA treatment with anti-inflammatory drugs partially reverses the oral microbial dysbiosis. Together, these data demonstrate that systemic diseases characterized by enhanced inflammation disturb the oral microbiota and point to IL-17 as key mediator in this process.

The aggravation of arthritis by periodontitis is dependent of IL-17 receptor A activation

AIM

To evaluate whether Porphyromonas gingivalis-induced periodontitis aggravates the antigen-induced arthritis (AIA) model, and whether this effect is dependent on the Th17/IL-17 signalling pathway.

MATERIALS AND METHODS

Antigen-induced arthritis was triggered by local injection of methylated bovine serum albumin into the knee joint of previously immunized C57BL/6 wild-type (WT) and IL-17 receptor A (IL-17RA)-knockout mice. Periodontal disease in naïve or arthritic mice was induced by oral infection with P. gingivalis. Animals were sacrificed 7, 15 and 30 days after infection. Alveolar bone loss, joint histopathology, articular hyperalgesia and joint cytokine production were assessed, in addition to the proportion of Th17 and Treg cells isolated from the inguinal lymph nodes.

RESULTS

No influence of experimentally-induced arthritis was found on the alveolar bone resorption induced by P. gingivalis. However, mice with experimentally-induced arthritis that were exposed to P. gingivalis presented higher joint damage and Th17 frequencies when compared to non-infected mice. The aggravation of arthritis by periodontitis was accompanied by increased TNF and IL-17 production and articular neutrophil infiltration, whereas arthritis aggravation and changes in neutrophil infiltration were absent in IL-17RA-deficient mice.

CONCLUSION

The effects of P. gingivalis-induced periodontitis on arthritis are dependent on Th17 expansion and IL-17RA signalling, which lead to increased neutrophil infiltration into the joints.

Subgingival microbiota dysbiosis in systemic lupus erythematosus: association with periodontal status

BACKGROUND

Periodontitis results from the interaction between a subgingival biofilm and host immune response. Changes in biofilm composition are thought to disrupt homeostasis between the host and subgingival bacteria resulting in periodontal damage. Chronic systemic inflammatory disorders have been shown to affect the subgingival microbiota and clinical periodontal status. However, this relationship has not been examined in subjects with systemic lupus erythematosus (SLE). The objective of our study was to investigate the influence of SLE on the subgingival microbiota and its connection with periodontal disease and SLE activity.

METHODS

We evaluated 52 patients with SLE compared to 52 subjects without SLE (control group). Subjects were classified as without periodontitis and with periodontitis. Oral microbiota composition was assessed by amplifying the V4 region of 16S rRNA gene from subgingival dental plaque DNA extracts. These amplicons were examined by Illumina MiSeq sequencing.

RESULTS

SLE patients exhibited higher prevalence of periodontitis which occurred at a younger age compared to subjects of the control group. More severe forms of periodontitis were found in SLE subjects that had higher bacterial loads and decreased microbial diversity. Bacterial species frequently detected in periodontal disease were observed in higher proportions in SLE patients, even in periodontal healthy sites such as Fretibacterium, Prevotella nigrescens, and Selenomonas. Changes in the oral microbiota were linked to increased local inflammation, as demonstrated by higher concentrations of IL-6, IL-17, and IL-33 in SLE patients with periodontitis.

CONCLUSIONS

SLE is associated with differences in the composition of the microbiota, independently of periodontal status.