The oral microbiome of patients with axial spondyloarthritis compared to healthy individuals

The role of the gastrointestinal microbiome on rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis and reactive arthritis: A systematic review

BACKGROUND

There is an increasing body of literature observing a state of dysbiosis in the gut microbiome in different autoimmune conditions including inflammatory arthritis. It is unknown whether the microbiome can be a biomarker for prognostication purposes or for stratification of treatment strategies. This review aims to evaluate the existing evidence on the association between the microbiome and inflammatory arthritis, including rheumatoid arthritis (RA), psoriatic arthritis (PsA) and ankylosing spondylitis (AS) and reactive arthritis (ReA) population groups.

METHODS

This systematic review was performed based on methods from the Cochrane guidelines and reported based on PRISMA criteria. Studies exploring the microbiome of patients with RA, AS, PsA or ReA compared with controls via 16s rRNA or shotgun sequencing were evaluated. The outcomes of interest include alpha and beta diversity, abundance or depletion of organisms and functional analysis. Literature up to August 2024 was retrieved searching the databases PubMed, Medline, ScienceDirect, Scopus, Web of Science, Cochrane, EMBASE and CINAHL. All references were systematically evaluated by two reviewers. Quality of the studies were evaluated by the Newcastle-Ottawa Scale.

FINDINGS

The review yielded 25,794 search results, of which 53 studies were included for the RA group, 34 studies for the AS group, 6 studies for the PsA group and 2 studies for the ReA group. Reduced diversity has been observed in disease groups and in patients with higher disease activity.

INTERPRETATION

There are limited longitudinal studies on the role of the microbiome in inflammatory arthritis, in particular PsA. Existing cross-sectional studies suggest altered microbiome in disease states compared with controls. Further studies are required to understand the utility of the microbiome as a biomarker to better understand prognosis and tailor treatments.

Pro-Inflammatory Oral Microbiota in Juvenile Spondyloarthritis: A Pilot Study

The role of the microbiota in the pathogenesis of arthritis is gaining increasing attention. While multiple studies have queried the intestinal microbiota, very few have analyzed the contents of the oral microbiota. In this pilot study, we obtained salivary and sub-gingival specimens from a cohort of six healthy controls and five children with well-controlled spondyloarthritis (SpA) and performed 16S sequencing on bacteria obtained from both habitats. The Quantitative Insight into Microbial Ecology tool suite was used to generate operational taxonomic units, Phyloseq was used for diversity analyses, and DeSeq2 was used to compare abundances while adjusting for multiple comparisons. A repeat specimen was obtained from one subject during a flare. Clustering based upon diagnosis was observed from both habitats, with decreased alpha diversity seen within the plaque obtained from the patients vs. controls. Among the differentially abundant taxa were statistically significantly increased plaque Fusobacterium and salivary Rothia mucilaginosa among the patients compared to the controls. Additionally, the abundance of plaque Fusobacterium increased in one patient at the time of a flare. Our data suggest that the oral cavity may harbor bacteria involved in the pathogenesis of spondyloarthritis; additional studies are warranted.

Axial spondyloarthritis patients have altered mucosal IgA response to oral and fecal microbiota

Axial spondyloarthritis (axSpA) is an inflammatory arthritis involving the spine and the sacroiliac joint with extra-articular manifestations in the eye, gut, and skin. The intestinal microbiota has been implicated as a central environmental component in the pathogenesis of various types of spondyloarthritis including axSpA. Additionally, alterations in the oral microbiota have been shown in various rheumatological conditions, such as rheumatoid arthritis (RA). Therefore, the aim of this study was to investigate whether axSpA patients have an altered immunoglobulin A (IgA) response in the gut and oral microbial communities. We performed 16S rRNA gene (16S) sequencing on IgA positive (IgA⁺) and IgA negative (IgA^-) fractions (IgA-SEQ) from feces (n=17 axSpA; n=14 healthy) and saliva (n=14 axSpA; n=12 healthy), as well as on IgA-unsorted fecal and salivary samples. PICRUSt2 was used to predict microbial metabolic potential in axSpA patients and healthy controls (HCs). IgA-SEQ analyses revealed enrichment of several microbes in the fecal (Akkermansia, Ruminococcaceae, Lachnospira) and salivary (Prevotellaceae, Actinobacillus) microbiome in axSpA patients as compared with HCs. Fecal microbiome from axSpA patients showed a tendency towards increased alpha diversity in IgA⁺ fraction and decreased diversity in IgA^- fraction in comparison with HCs, while the salivary microbiome exhibits a significant decrease in alpha diversity in both IgA⁺ and IgA^- fractions. Increased IgA coating of Clostridiales Family XIII in feces correlated with disease severity. Inferred metagenomic analysis suggests perturbation of metabolites and metabolic pathways for inflammation (oxidative stress, amino acid degradation) and metabolism (propanoate and butanoate) in axSpA patients. Analyses of fecal and salivary microbes from axSpA patients reveal distinct populations of immunoreactive microbes compared to HCs using the IgA-SEQ approach. These bacteria were not identified by comparing their relative abundance alone. Predictive metagenomic analysis revealed perturbation of metabolites/metabolic pathways in axSpA patients. Future studies on these immunoreactive microbes may lead to better understanding of the functional role of IgA in maintaining microbial structure and human health.

Oral Microbiome: Getting to Know and Befriend Neighbors, a Biological Approach

The oral microbiome, forming a biofilm that covers the oral structures, contains a high number of microorganisms. Biofilm formation starts from the salivary pellicle that allows bacterial adhesion-colonization-proliferation, co-aggregation and biofilm maturation in a complex microbial community. There is a constant bidirectional crosstalk between human host and its oral microbiome. The paper presents the fundamentals regarding the oral microbiome and its relationship to modulator factors, oral and systemic health. The modern studies of oral microorganisms and relationships with the host benefits are based on genomics, transcriptomics, proteomics and metabolomics. Pharmaceuticals such as antimicrobials, prebiotics, probiotics, surface active or abrasive agents and plant-derived ingredients may influence the oral microbiome. Many studies found associations between oral dysbiosis and systemic disorders, including autoimmune diseases, cardiovascular, diabetes, cancers and neurodegenerative disorders. We outline the general and individual factors influencing the host-microbial balance and the possibility to use the analysis of the oral microbiome in prevention, diagnosis and treatment in personalized medicine. Future therapies should take in account the restoration of the normal symbiotic relation with the oral microbiome.

No Genetic Causal Association Between Periodontitis and Arthritis: A Bidirectional Two-Sample Mendelian Randomization Analysis

Objectives

Periodontitis (PD) has been linked to arthritis in previous epidemiological observational studies; however, the results are inconclusive. It remains unclear whether the association between PD and arthritis is causal. The purpose of this study was to investigate the causal association of PD with arthritis, including rheumatoid arthritis (RA) and osteoarthritis (OA).

Methods

We performed a two-sample bidirectional Mendelian randomization (MR) analysis using publicly released genome-wide association studies (GWAS) statistics. The inverse-variance weighted (IVW) method was used as the primary analysis. We applied four complementary methods, including weighted median, weighted mode, MR-Egger regression and MR pleiotropy residual sum and outlier (MR-PRESSO) to detect and correct for the effect of horizontal pleiotropy.

Results

Genetically determined PD did not have a causal effect on OA (OR = 1.06, 95% CI: 0.99-1.15, P = 0.09) and RA (OR = 0.99, 95% CI: 0.87-1.13, P = 0.89). Furthermore, we did not find a significant causal effect of arthritis on PD in the reverse MR analysis. The results of MR-Egger regression, Weighted Median, and Weighted Mode methods were consistent with those of the IVW method. Horizontal pleiotropy was unlikely to distort the causal estimates according to the sensitivity analysis.

Conclusions

Our MR analysis reveals non-causal association of PD with arthritis, despite observational studies reporting an association between PD and arthritis.

Periodontal diseases and its association with disease activity in ankylosing spondylitis/SpA: A systematic review

A close association between periodontal disease (PD) and ankylosing spondylitis (AS) has long been speculated. Both diseases are characterized by dysregulation of the host inflammatory response, leading to further destruction of the soft and hard connective tissue. There is evidence of increased levels of tumor necrosis factor-alpha and various interleukins in both patients of AS and periodontitis. This study aimed to conduct a systematic review exploring the relationship between AS and PD. We searched MEDLINE - Embase databases (from their inception till October 2019) using appropriate combinations of the following search items with limits '(English, Human)': Ankylosing spondylitis, spondyloarthritis, spondyloarthropathies, spondyloarthritides, spinal disease, musculoskeletal disease, rheumatic disease and periodontitis, PD, periodontoses, parodontoses, chronic periodontitis, gum disease, gingivitis, oral health, dental health, plaque index (PI), bleeding on probing (BOP), probing pocket depth (PPD), and clinical attachment loss (CAL). This search was supplemented by the manual search of bibliographies of the selected articles and conference proceedings of the European League against Rheumatism. Only the reviews and observational studies of cross-sectional, cohort, or case-control type on adult patients with AS were selected. Data were extracted from a predesigned PROforma. A total of 984 articles were identified, and 12 were selected for a detailed appraisal. All the identified studies were of the case-control type. The prevalence of periodontitis ranged from 38% to 88% in patients with AS and 26% to 71% in the control group. Of the 12 studies, 2 showed significant changes in PI, 2 showed altered PPD, 3 showed significantly increased CAL, and 2 showed increased BOP. In 7 studies, periodontitis was seen in a significant number of patients with AS (p<0.05). All the studies reported that the prevalence of PD in patients with AS was higher than that in patients without AS. Our systematic review found an association between AS and PD. Patients with AS show a higher prevalence of periodontitis and poor oral hygiene than the healthy controls.

Relationship between periodontal status and disease activity in patients with ankylosing spondylitis

Objectives

Ankylosing spondylitis (AS) is a chronic inflammatory disease mainly affecting the spine and sacroiliac joints, characterized by enthesitis. Recent studies have investigated the relationship between AS and periodontitis. The aim of this study was to evaluate the periodontal status of patients with AS and to determine the factors affecting this.

Material and methods

The study included 200 AS patients, of which 129 were taking anti-tumour necrosis factor (TNF) drugs and 71 were taking non-steroid anti-inflammatory drugs (NSAID). Patients did not change their medication during the study. Disease activity was evaluated with the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), mobility with the Bath Ankylosing Spondylitis Metrology Index (BASMI), functional status with the Bath Ankylosing Spondylitis Functional Index (BASFI), enthesitis with the integrated Maastricht Ankylosing Spondylitis Enthesitis Score (MASES), and quality of life with the Ankylosing Spondylitis Quality of Life (ASQoL) scale. Data related to erythrocyte sedimentation rate, and C-reactive protein were recorded from the hospital information system. The plaque index (PI), gingival index (GI), pocket depth (PD), attachment level (CAL) measurements, and bleeding index (BOP) were measured.

Results

The results showed that 35.5% of the AS patients had periodontitis, at a lower rate in the anti-TNF group than in the NSAID group, but the difference was not statistically significant. Periodontitis-related factors were found to be age, BASFI and BASMI. A significant relationship was found between MASES and BOP and GI.

Conclusions

This suggests that periodontitis may be an enthesis in AS. Nevertheless, further studies are needed to explain the mechanism of periodontitis in AS patients.

Gut Microbiome and Its Interaction with Immune System in Spondyloarthritis

Emerging evidence suggests there is a gut-joint axis in spondyloarthritis (SpA). In a study, subclinical gut inflammation occurred in nearly 50% of SpA. Chronic gut inflammation also correlated with disease activity in SpA. Trillions of microorganisms reside in the human gut and interact with the human immune system. Dysbiosis affects gut immune homeostasis and triggers different autoimmune diseases including SpA. The absence of arthritis in HLA-B27 germ-free mice and the development of arthritis after the introduction of commensal bacteria to HLA-B27 germ-free mice proved to be the important role of gut bacteria in shaping SpA, other than the genetic factor. The recent advance in gene sequencing technology promotes the identification of microorganisms. In this review, we highlighted current evidence supporting the link between gut and axial SpA (axSpA). We also summarized available findings of gut microbiota and its interaction with the immune system in axSpA. Future research may explore the way to modulate gut microorganisms in axSpA and bring gut microbiome discoveries towards application.

Oral microbiome-systemic link studies: perspectives on current limitations and future artificial intelligence-based approaches

In the past decade, there has been a tremendous increase in studies on the link between oral microbiome and systemic diseases. However, variations in study design and confounding variables across studies often lead to inconsistent observations. In this narrative review, we have discussed the potential influence of study design and confounding variables on the current sequencing-based oral microbiome-systemic disease link studies. The current limitations of oral microbiome-systemic link studies on type 2 diabetes mellitus, rheumatoid arthritis, pregnancy, atherosclerosis, and pancreatic cancer are discussed in this review, followed by our perspective on how artificial intelligence (AI), particularly machine learning and deep learning approaches, can be employed for predicting systemic disease and host metadata from the oral microbiome. The application of AI for predicting systemic disease as well as host metadata requires the establishment of a global database repository with microbiome sequences and annotated host metadata. However, this task requires collective efforts from researchers working in the field of oral microbiome to establish more comprehensive datasets with appropriate host metadata. Development of AI-based models by incorporating consistent host metadata will allow prediction of systemic diseases with higher accuracies, bringing considerable clinical benefits.

Microbial and metabolomic analysis of gingival crevicular fluid in general chronic periodontitis patients: lessons for a predictive, preventive, and personalized medical approach

Objectives

General chronic periodontitis (GCP) is a bacterial inflammatory disease with complex pathology. Despite extensive studies published on the variation in the oral microbiota and metabolic profiles of GCP patients, information is lacking regarding the correlation between host-bacterial interactions and biochemical metabolism. This study aimed to analyze the oral microbiome, the oral metabolome, and the link between them and to identify potential molecules as useful biomarkers for predictive, preventive, and personalized medicine (PPPM) in GCP.

Methods

In this study, gingival crevicular fluid (GCF) samples were collected from patients with GCP (n = 30) and healthy controls (n = 28). The abundance of oral microbiota constituents was obtained by Illumina sequencing, and the relative level of metabolites was measured by gas chromatography-mass spectrometry. Full-mouth probing depth, clinical attachment loss, and bleeding on probing were recorded as indices of periodontal disease.

Results

The relative abundances of 7 phyla and 82 genera differed significantly between the GCP and healthy groups. Seventeen differential metabolites involved in different metabolism pathways were selected based on variable influence on projection values (VIP > 1) and P values (P < 0.05). Through Spearman's correlation analysis, microorganisms, metabolites in GCF, and clinical data together showed a clear trend, and clinical data regarding periodontitis can be reflected in the shift of the oral microbial community and the change in metabolites in GCF. A combination of citramalic acid and N-carbamylglutamate yielded satisfactory accuracy (AUC = 0.876) for the predictive diagnosis of GCP.

Conclusions

Dysbiosis in the polymicrobial community structure and changes in metabolism could be mechanisms underlying periodontitis. The differential microorganisms and metabolites in GCF between periodontitis patients and healthy individuals are possibly biomarkers, pointing to a potential strategy for the prediction, diagnosis, prognosis, and management of personalized periodontal therapy.

Periodontal disease and influence of periodontal treatment on disease activity in patients with rheumatoid arthritis and spondyloarthritis

The aim of this study was to assess the prevalence of periodontal disease and the effect of periodontal treatment in patients with rheumatoid arthritis (RA) and spondyloarthritis (SpA). Forty-four RA patients, thirty SpA patients and thirty-nine healthy volunteers were recruited to the study. Periodontal examination included the approximal plaque index (API), bleeding on probing (BoP), probing depth (PD) and number of teeth. Samples from the deepest periodontal pockets were taken for the detection of Porphyromonas gingivalis DNA with the use of the polymerase chain reaction. All subjects with periodontitis, who completed the study, received periodontal treatment consisting of scaling/root planing and oral hygiene instructions. Disease activity scores, clinical and laboratory parameters were assessed before and 4-6 weeks after periodontal treatment. No significant difference in the prevalence of periodontal disease and the presence of P. gingivalis DNA were found in RA and SpA patients compared to healthy controls. Significantly higher API (80% vs 63%; p = 0.01) and a lower number of teeth (20 vs 25, p = 0.001) were found in RA patients. BoP was significantly elevated in SpA patients (51% vs 33%, p = 0.02). Disease activity measured by the DAS28(CRP) was significantly reduced in RA patients after periodontal treatment (p = 0.002). Clinical and biochemical parameters were not improved in SpA patients. Nonsurgical periodontal treatment had an impact on the decrease in RA activity. Periodontal examination is necessary in patients with RA to detect and treat periodontitis at an early stage.

[Pathogenesis of spondylarthritis : Relevance for treatment]

Although the pathogenesis of spondylarthritis (SpA) has been the subject of intensive research in recent years, the consequences for treatment are relatively minor. Basic research studies indicated a potentially important role of the cytokines tumor necrosis factor (TNF) alpha and interleukin (IL)-17 for the pathogenesis of SpA but their outstanding role could then only be demonstrated by their inhibition in clinical studies, while other promising targets, such as IL‑23 and IL‑6 could not be shown to be relevant (at least against axial manifestations) in clinical studies. The intestinal microbiota probably plays an important role in the pathogenesis but not yet for the treatment of SpA. Ultimately, early effective and long-term suppression of inflammation is currently the best method to prevent ankylosis in the long run.

Periodontal condition is associated with disease duration and motoric disabilities in patients with ankylosing spondylitis: results of a cross-sectional study

OBJECTIVE

Recent literature reveals worse periodontal health condition in ankylosing spondylitis (AS). However, roles of AS-related parameters, periodontal condition, and their association appear unclear. This cross-sectional study aimed at investigating dental and periodontal health as well as potentially periodontal pathogenic bacteria in patients with AS compared to healthy control subjects (HC).

METHODS

Dental examination comprised dental findings (DMF-T), periodontal probing depth (PPD), bleeding on probing, clinical attachment loss (CAL), papillary bleeding index, and microbiological analysis based on polymerase chain reaction of selected potentially periodontal pathogenic bacteria. Classification of periodontitis severity was based on PPD and/or CAL and divided into no/mild, moderate, and severe periodontitis.

RESULTS

52 participants with AS and 52 HC were included. 96% of the AS group and 75% of HC had moderate to severe periodontitis (moderate: AS = 26, HC = 34; severe: AS = 23, HC = 5; p < 0.01). Furthermore, a higher number of decayed teeth (D-T) were found in AS compared to HC (p = 0.02). A significant difference between AS und HC was detected for the prevalences of Parvimonas micra (AS = 92%, HC = 71%; p = 0.01), Eubacterium nodatum (AS = 35%, HC = 17%; p = 0.05), and Eikenella corrodens (AS = 96%, HC = 77%; p = 0.01). Bath Ankylosing Spondylitis Metrology Index (BASMI) and disease duration showed significant associations to PPD and CAL (p < 0.01).

CONCLUSION

Patients with AS show worse dental and periodontal conditions compared to HC. Thereby, prevalence of bacteria related to insufficient oral hygiene was higher in AS. BASMI and duration of AS affect periodontal burden. Accordingly, particular attention considering dental care and oral hygiene in AS patients seems to be reasonable.

Efficacy of nanoceria for periodontal tissues alteration in glutamate-induced obese rats-multidisciplinary considerations for personalized dentistry and prevention

BACKGROUND

Nowadays, we face the global epidemic of obesity, that is known to contribute to the development of many diseases, such as the oral cavity pathologies. Dental and oral pathologies are frequently caused by and overlapped with systemic multifactorial diseases such as obesity being its early indicators and risk factors. The aim was to study the influence of nanoceria on periodontal tissues alteration in glutamate (MSG)-induced obese rats.

METHODS

We included 52 Wistar rats of both genders and divided into four groups: newborn rats in group 1 (control) received subcutaneously 8 μl/g saline. Group 2 received 3 to 4 mg/g MSG subcutaneously on the second, fourth, sixth, eighth, and tenth day of life; group 3-intragastric administration of nanocrystalline cerium dioxide at a dose of 1 mg/kg volume of 2.9 ml/kg against the background of glutamate-induced obesity; the fourth group of animals was treated with a solution of sodium citrate intragastric volume of 2.9 ml/kg (solvent of nanocrystalline cerium). We determined the total proteolytic activity, the total antitrypsin activity, the content-free fucose and glycosaminoglycanes (GAG), content of TBA-active of products, the content of oxidation-modified proteins (OMB), and catalase activity in the homogenate of soft periodontal tissues of rats.

RESULTS

Intragastric injection of nanoceria prevents activation of proteolytic processes, reducing the catabolism of glycoproteins and proteoglycans of periodontal tissue in MSG-induced obese rats. Injection of nanoceria prevents activation of proteolytic processes, significantly decreases the total proteolytic activity, and inhibits the activation of free radical oxidation in periodontal tissues of rats compared with MSG-induced obesity model without corrections. Further, it significantly increases the total antitrypsin activity in periodontal tissues by 1.7 times, TBA-reagents by 1.7 times, and content of OMB by 1.4 times compared with glutamate-induced obese animals.

CONCLUSIONS

MSG-induced obesity triggers periodontal tissue alterations in the rat model. Nanoceria contributes to the corrections of pathological changes in periodontal tissues in glutamate-induced obese rats via balancing protein-inhibitory capacity and reducing the depolymerization of fucosylated proteins and proteoglycans and antioxidative activity.

A Possible Role of Intestinal Microbiota in the Pathogenesis of Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory disease primarily affecting the sacroiliac joints and the spine, for which the pathogenesis is thought to be a result of the combination of host genetic factors and environmental triggers. However, the precise factors that determine one’s susceptibility to AS remain to be unraveled. With 100 trillion bacteria residing in the mammalian gut having established a symbiotic relation with their host influencing many aspects of host metabolism, physiology, and immunity, a growing body of evidence suggests that intestinal microbiota may play an important role in AS. Several mechanisms have been suggested to explain the potential role of the microbiome in the etiology of AS, such as alterations of intestinal permeability, stimulation of immune responses, and molecular mimicry. In this review, the existing evidence for the involvement of the microbiome in AS pathogenesis was discussed and the potential of intestinal microbiome-targeting strategies in the prevention and treatment of AS was evaluated.