Periodontitis and periodontopathic bacteria as risk factors for rheumatoid arthritis: A review of the last 10 years.

Rheumatoid arthritis (RA) is characterized by chronic inflammatory destruction of joint tissue and is caused by an abnormal autoimmune response triggered by interactions between genetics, environmental factors, and epigenetic and posttranslational modifications. RA has been suggested to be interrelated with periodontitis, a serious form or stage of chronic inflammatory periodontal disease associated with periodontopathic bacterial infections, genetic predisposition, environmental factors, and epigenetic influences. Over the last decade, a number of animal and clinical studies have been conducted to assess whether or not periodontitis and associated periodontopathic bacteria constitute risk factors for RA. The present review introduces recent accumulating evidence to support the associations of periodontitis and periodontopathic bacteria with the risk of RA or the outcome of RA pharmacological treatment with disease-modifying antirheumatic drugs. In addition, the results from intervention studies have suggested an improvement in RA clinical parameters after nonsurgical periodontal treatment. Furthermore, the potential causal mechanisms underlying the link between periodontitis and periodontopathic bacteria and RA are summarized.

The role of foreign body response in peri-implantitis: What is the evidence?

Historically, there has been broad consensus that osseointegration represents a homeostasis between a titanium dental implant and the surrounding bone, and that the crestal bone loss characteristic of peri-implantitis is a plaque-induced inflammatory process. However, this notion has been challenged over the past decade by proponents of a theory that considers osseointegration an inflammatory process characterized by a foreign body reaction and peri-implant bone loss as an exacerbation of this inflammatory response. A key difference in these two schools of thought is the perception of the relative importance of dental plaque in the pathogenesis of crestal bone loss around implants, with obvious implications for treatment. This review investigates the evidence for a persistent foreign body reaction at osseointegrated dental implants and its possible role in crestal bone loss characteristic of peri-implantitis. Further, the role of implant-related material release within the surrounding tissue, particularly titanium particles and corrosion by-products, in the establishment and progression in peri-implantitis is explored. While it is acknowledged that these issues require further investigation, the available evidence suggests that osseointegration is a state of homeostasis between the titanium implant and surrounding tissues, with little evidence that a persistent foreign body reaction is responsible for peri-implant bone loss after osseointegration is established. Further, there is a lack of evidence for a unidirectional causative role of corrosion by-products and titanium particles as possible non-plaque related factors in the etiology of peri-implantitis.

Associations between inflammation-related LL-37 with subgingival microbial dysbiosis in rheumatoid arthritis patients.

OBJECTIVE: This study investigated the subgingival microbial profile of rheumatoid arthritis (RA) patients and its associations with disease parameters and the inflammation-related antimicrobial peptide, LL-37. METHODS: RA and non-RA (NRA) patients were assessed for periodontal status and divided into periodontitis (CP), gingivitis (G), and healthy (H) groups. Subgingival plaque 16s rRNA gene sequencing data was processed and analyzed using the CLC Genomic Workbench (Qiagen). Bacterial diversity and co-occurrence patterns were examined. Differential abundance between groups was also investigated. Associations between bacterial genera with disease parameters and LL-37 levels were explored qualitatively using canonical correlation analysis. RESULTS: Subgingival microbial community clustered in CP status. Co-occurrence network in NRA-H was dominated by health-associated genera, while the rest of the networks' key genera were both health- and disease-associated. RA-CP displayed highly inter-generic networks with a statistically significant increase in periodontal disease-associated genera (p<0.05). In NRA-H, disease parameters and LL-37 were correlated positively with disease-associated genera while negatively with health-associated genera. However, in the remaining groups, mixed positive and negative correlations were noted with genera. CONCLUSION: RA patients demonstrated subgingival microbial dysbiosis where the bacteria networks were dominated by health- and disease-associated genera. Mixed correlations with disease parameters and LL-37 levels were noted. CLINICAL RELEVANCE: The subgingival microbial dysbiosis in RA may predispose these patients to developing periodontal inflammation with an associated detrimental effect on host immune responses. Routine periodontal assessment may allow initiation of treatment strategies to minimize the effects of gingival inflammation on the existing heightened immune response present in RA patients.

The emerging role of small extracellular vesicles in saliva and gingival crevicular fluid as diagnostics for periodontitis.

Periodontitis is a highly prevalent multifactorial chronic inflammatory disease associated with a destructive host immune-inflammatory response to microbial dysbiosis. Current clinical diagnosis is reliant on measuring past periodontal tissue loss, with a lack of molecular biomarkers to accurately diagnose periodontitis activity in 'real-time'. Thus, discovery of new classes of diagnostic biomarkers is of critical importance in periodontology. Small extracellular vesicles (<200 nm in diameter; sEVs) from oral biofluids (saliva and gingival crevicular fluid-GCF) are lipid-encapsulated bilayered vesicles and have recently emerged as a potential source of biomarkers for periodontal disease (gingivitis and periodontitis), due to the cargo of protein, genetic material and lipids derived from their parent cells. There is limited information on the isolation and characterisation methods of saliva/GCF-sEVs or the characterisation of sEVs cargo as biomarkers for periodontitis. In this review, we detail the composition of sEVs and summarise their isolation and characterisation from saliva and GCF. The potential role of saliva and GCF-derived sEVs in periodontitis diagnosis is also explored. It is proposed that sEVs cargo, including protein, microRNA, message RNA and DNA methylation, are potential biomarkers for periodontitis with good diagnostic power (area under the curve-AUC > 0.9).

Periodontal and Dental Pulp Cell-Derived Small Extracellular Vesicles: A Review of the Current Status.

Extracellular vesicles (EVs) are membrane-bound lipid particles that are secreted by all cell types and function as cell-to-cell communicators through their cargos of protein, nucleic acid, lipids, and metabolites, which are derived from their parent cells. There is limited information on the isolation and the emerging therapeutic role of periodontal and dental pulp cell-derived small EVs (sEVs, <200 nm, or exosome). In this review, we discuss the biogenesis of three EV subtypes (sEVs, microvesicles and apoptotic bodies) and the emerging role of sEVs from periodontal ligament (stem) cells, gingival fibroblasts (or gingival mesenchymal stem cells) and dental pulp cells, and their therapeutic potential in vitro and in vivo. A review of the relevant methodology found that precipitation-based kits and ultracentrifugation are the two most common methods to isolate periodontal (dental pulp) cell sEVs. Periodontal (and pulp) cell sEVs range in size, from 40 nm to 2 µm, due to a lack of standardized isolation protocols. Nevertheless, our review found that these EVs possess anti-inflammatory, osteo/odontogenic, angiogenic and immunomodulatory functions in vitro and in vivo, via reported EV cargos of EV-miRNAs, EV-circRNAs, EV-mRNAs and EV-lncRNAs. This review highlights the considerable therapeutic potential of periodontal and dental pulp cell-derived sEVs in various regenerative applications.

Antibodies against citrullinated proteins in relation to periodontitis with or without rheumatoid arthritis: a cross-sectional study.

BACKGROUND: Previous studies have reported conflicting findings between serum anti-citrullinated protein antibodies (ACPA) levels in rheumatoid arthritis (RA) participants with and without periodontitis (Pd). This study aimed to analyse possible correlations between serum ACPA levels and clinical parameters in Pd and RA participants. METHODS: Full mouth periodontal examination (probing pocket depth, clinical attachment levels, gingival bleeding index, visual plaque index) was conducted and serum samples obtained from 80 participants comprising RA, Pd, both RA and Pd (RAPd) and healthy individuals (HC). Erythrocyte sedimentation rates (ESR) and periodontal inflamed surface area (PISA) were obtained. Serum samples were analysed for ACPA quantification using enzyme-linked immunosorbent assay (ELISA). RESULTS: Median levels (IU/mL) of ACPA (interquartile range, IQR) in RAPd, RA, Pd and HC groups were 118.58(274.51), 102.02(252.89), 78.48(132.6) and 51.67(91.31) respectively. ACPA levels were significantly higher in RAPd and RA as compared to HC group (p < 0.05). However, ACPA levels of any of the groups were not correlated with any clinical periodontal and RA parameters within the respective groups. CONCLUSIONS: At individual level, the amount of serum ACPA seem to have an increasing trend with the diseased condition in the order of RAPd > RA > Pd > HC. However, lack of any significant correlation between the serum ACPA levels with the clinical Pd and RA parameters warrants further studies to investigate the causal link between RA and Pd for such a trend. Further studies involving more inflammatory biomarkers might be useful to establish the causal link between Pd in the development and progression of RA or vice versa.

Salivary Outer Membrane Vesicles and DNA Methylation of Small Extracellular Vesicles as Biomarkers for Periodontal Status: A Pilot Study.

Periodontitis is an inflammatory disease, associated with a microbial dysbiosis. Early detection using salivary small extracellular vesicles (sEVs) biomarkers may facilitate timely prevention. sEVs derived from different species (i.e., humans, bacteria) are expected to circulate in saliva. This pilot study recruited 22 participants (seven periodontal healthy, seven gingivitis and eight periodontitis) and salivary sEVs were isolated using the size-exclusion chromatography (SEC) method. The healthy, gingivitis and periodontitis groups were compared in terms of salivary sEVs in the CD9+ sEV subpopulation, Gram-negative bacteria-enriched lipopolysaccharide (LPS+) outer membrane vesicles (OMVs) and global DNA methylation pattern of 5-methylcytosine (5mC), 5-hydroxymethylcytosine (5hmC) and N6-Methyladenosine (m6dA). It was found that LPS+ OMVs, global 5mC methylation and four periodontal pathogens (T. denticola, E. corrodens, P. gingivalis and F. nucleatum) that secreted OMVs were significantly increased in periodontitis sEVs compared to those from healthy groups. These differences were more pronounced in sEVs than the whole saliva and were more superior in distinguishing periodontitis than gingivitis, in comparison to healthy patients. Of note, global 5mC hypermethylation in salivary sEVs can distinguish periodontitis patients from both healthy controls and gingivitis patients with high sensitivity and specificity (AUC = 1). The research findings suggest that assessing global sEV methylation may be a useful biomarker for periodontitis.

Impact of periodontitis on quality of life among subjects with rheumatoid arthritis: a cross sectional study.

BACKGROUND: This study aimed to assess the impact of periodontitis (PD) on the health related quality of life (HRQoL) and oral health related QoL (OHRQoL) of subjects with rheumatoid arthritis (RA) and PD. METHODS: Subjects from dental and RA clinics were screened. Complete periodontal examinations were performed. Subjects were divided into 4 groups: RA-PD, RA, PD and healthy controls (HC). Questionnaires on characteristics and Malaysian versions of Oral Health Impact Profile (OHIP-14(M)) and Health Assessment Questionnaire (HAQ-DI)) were answered. RESULTS: A total of 187 subjects were included (29 RA-PD, 58 RA, 43 PD and 57 HC). OHIP-14(M) severity score was highest in the PD group (17.23 ± 10.36) but only significantly higher than the HC group (p < 0.05). The HAQ-DI scores of the RA group was significantly higher than the PD and HC groups (p < 0.05). The interaction between the effects of PD and RA on the OHRQoL and HRQoL was statistically significant (p < 0.05). CONCLUSION: PD and RA subjects both suffer impacts on their OHRQoL and HRQoL respectively. The interaction effect of both diseases significantly conferred impacts on their OHRQoL and HRQoL as measured by the OHIP-14(M) and HAQ-DI.

Periodontitis and rheumatoid arthritis: An update 2012-2017.

Rheumatoid arthritis and chronic periodontitis are both chronic inflammatory diseases characterized by an exacerbated inflammatory reaction that leads to destruction of bone and other connective tissue. Owing to these similarities, the relationship between these two diseases has been investigated for over two decades. In the 2013 proceedings from a workshop jointly held by the European Federation of Periodontology and American Academy of Periodontology in 2012 it was concluded that there was at least minimal evidence of an association between periodontitis and rheumatoid arthritis. In this review, we consider publications in the field over the past 5 years and determine whether the evidence for this relationship has increased.

Salivary Small Extracellular Vesicles Associated miRNAs in Periodontal Status-A Pilot Study.

This pilot study aims to investigate whether salivary small extracellular vesicle (sEV)-associated microRNAs could act as potential biomarkers for periodontal disease status. Twenty-nine participants (10 who were healthy, nine with gingivitis, 10 with stage III/IV periodontitis) were recruited and unstimulated whole saliva samples were collected. Salivary sEVs were isolated using the size-exclusion chromatography (SEC) method and characterised by morphology, EV-protein and size distribution using transmission electron microscopy (TEM), Western Blot and Nanoparticle Tracking Analysis (NTA), respectively. Ten mature microRNAs (miRNAs) in salivary sEVs and saliva were evaluated using RT-qPCR. The discriminatory power of miRNAs as biomarkers in gingivitis and periodontitis versus healthy controls was evaluated by Receiver Operating Characteristics (ROC) curves. Salivary sEVs were comparable to sEVs morphology, mode, size distribution and particle concentration in healthy, gingivitis and periodontitis patients. Compared to miRNAs in whole saliva, three significantly increased miRNAs (hsa-miR-140-5p, hsa-miR-146a-5p and hsa-miR-628-5p) were only detected in sEVs in periodontitis when compared to that of healthy controls, with a good discriminatory power (area under the curve (AUC) = 0.96) for periodontitis diagnosis. Our study demonstrated that salivary sEVs are a non-invasive source of miRNAs for periodontitis diagnosis. Three miRNAs that are selectively enriched in sEVs, but not whole saliva, could be potential biomarkers for periodontal disease status.

An appraisal of the role of specific bacteria in the initial pathogenesis of periodontitis.

BACKGROUND: Historically, inflammatory periodontal diseases (gingivitis and periodontitis) have been recognized as being primarily of bacterial origin. Bacteria are necessary for disease development, but the presence of specific bacteria does not guarantee progression to periodontitis. Periodontitis is a multifactorial disease; specific bacteria are associated with disease, but may not be the target of treatment. Gingivitis and periodontitis are inflammatory conditions associated with bacterial overgrowth. AIM: To analyse evidence for established thought that specific bacteria directly participate in the pathogenesis of periodontitis and question the long-held tenet that penetration of the periodontal connective tissues by bacteria and their products is a significant phase in the initial development of periodontitis. METHODS: The literature was searched for studies on initiation of gingivitis and periodontitis by specific pathogens. The search results were insufficient for a systematic review and have been summarized in a commentary instead. RESULTS: There is very little evidence in the literature to support the commonly held concept that specific bacteria initiate periodontitis. CONCLUSION: We present evidence for a paradigm supporting the central role of inflammation, rather than specific microbiota, in the early pathogenesis of periodontitis, and discuss whether controlling the inflammation can influence the character and composition of the periodontal infection.

Immunomodulatory Properties of Induced Pluripotent Stem Cell-Derived Mesenchymal Cells.

MSC-like populations derived from induced pluripotent stem cells (iPSC-MSC) serve as an alternative stem cell source due to their high proliferative capacity. In this study, we assessed the immunomodulatory potential of iPSC-MSC generated from periodontal ligament (PDL) and gingival (GF) tissue. The iPSC-MSC lines exhibited a similar level of suppression of mitogen-stimulated peripheral blood mononuclear cells (PBMNC) proliferation compared to their respective parental fibroblast populations in vitro. Moreover, iPSC-MSC demonstrated the ability to suppress T-cells effector cells, Th1/Th2/Th17 populations, and increase levels of Treg cells. In order to investigate the mechanisms involved, expression of common MSC-derived soluble factors known to supress lymphocyte proliferation were assessed in iPSC-MSC cultured with PBMNC with direct cell-cell contact or separated in transwells. Real-time PCR analysis of factors known to be involved in MSC mediated immune regulation, found a general trend of elevated IDO1 and IL6 transcript levels in iPSC-MSC lines and their respective primary cells co-cultured with activated PBMNC, with a wide range of gene expression levels between the different mesenchymal cell types. The results suggest that different iPSC-MSC may be useful as a potential alternative source of cells for future clinical use in therapeutic applications because of their potent immunosuppressive properties. J. Cell. Biochem. 117: 2844-2853, 2016. © 2016 Wiley Periodicals, Inc.

Semaphorin 3A induces mesenchymal-stem-like properties in human periodontal ligament cells.

Periodontal ligament stem cells (PDLSCs) have recently been proposed as a novel option in periodontal regenerative therapy. However, one of the issues is the difficulty of stably generating PDLSCs because of the variation of stem cell potential between donors. Here, we show that Semaphorin 3A (Sema3A) can induce mesenchymal-stem-like properties in human periodontal ligament (PDL) cells. Sema3A expression was specifically observed in the dental follicle during tooth development and in parts of mature PDL tissue in rodent tooth and periodontal tissue. Sema3A expression levels were found to be higher in multipotential human PDL cell clones compared with low-differentiation potential clones. Sema3A-overexpressing PDL cells exhibited an enhanced capacity to differentiate into both functional osteoblasts and adipocytes. Moreover, PDL cells treated with Sema3A only at the initiation of culture stimulated osteogenesis, while Sema3A treatment throughout the culture had no effect on osteogenic differentiation. Finally, Sema3A-overexpressing PDL cells upregulated the expression of embryonic stem cell markers (NANOG, OCT4, and E-cadherin) and mesenchymal stem cell markers (CD73, CD90, CD105, CD146, and CD166), and Sema3A promoted cell division activity of PDL cells. These results suggest that Sema3A may possess the function to convert PDL cells into mesenchymal-stem-like cells.

Human foreskin fibroblasts exert immunomodulatory properties by a different mechanism to bone marrow stromal/stem cells.

Human bone marrow mesenchymal stromal/stem cells (BMSCs) have been reported to possess immunomodulatory functions with the capacity to suppress immune reactions partly mediated by immunosuppressive factors, indoleamine 2,3-dioxygenase and nitric oxide, and suggested to be potentially applicable for therapeutic use. More recently, other fibroblast-like cells have been reported to possess similar properties. Here we demonstrate that human foreskin fibroblasts (HFFs) express an MSC-like immunophenotype and possess immunosuppressive properties similar to BMSCs but lack the capacity for osteogenic and adipogenic differentiation. HFFs suppressed human peripheral blood mononuclear cells (PBMC) proliferation stimulated with mitogen or in an allogeneic mixed lymphocyte reaction comparable to BMSCs. However, HFFs showed undetectable levels of indoleamine 2,3-dioxygenase and inducible nitric oxide synthase expression, in contrast to BMSCs when cocultured with activated PBMCs. To identify HFF specific immunosuppressive factors, we performed array profiling of common cytokines expressed by HFFs and BMSCs alone or when cocultured with activated PBMCs. Real-time polymerase chain reaction analysis confirmed that multiple factors were upregulated in HFFs cocultured with activated PBMCs compared with HFFs alone or BMSCs cultured under the same conditions. Functional assays identified interferon-α as the major immunosuppressive mediator expressed by HFFs. These results suggest that the HFFs possess immunosuppressive properties, which are mediated by alternate mechanisms to that reported for BMSCs.

Physical activity, inflammatory biomarkers in gingival crevicular fluid and periodontitis.

AIMS: To examine the associations of physical activity with interleukin 1-beta (IL-1beta), C-reactive protein (CRP) and periodontitis and to investigate whether any relationship between physical activity and inflammatory mediators differs between periodontitis cases and non-cases. MATERIAL AND METHODS: In this population-based case control study of Australians aged 18+ years, dentists conducted oral epidemiologic examinations identifying cases with moderate or severe periodontitis and periodontally healthy controls. Gingival crevicular fluid samples collected during examinations were analysed for inflammatory biomarkers. Subject-completed questionnaires assessed leisure-time physical activity. Exposure odds ratios (ORs) were estimated in multivariable logistic regression models adjusting for periodontitis risk indicators. RESULTS: Of 751 subjects (359 cases, 392 controls), those meeting a prescribed threshold for leisure-time physical activity had lower adjusted odds of elevated IL-1beta: OR=0.69, (95% CI=0.50-0.94) and detectable CRP: OR=0.70 (0.50-0.98) than less active adults. Physical activity was not associated with periodontitis: OR=1.14 (0.80-1.62). Periodontitis modified the association between levels of physical activity and detectable CRP. Increasing quartiles of physically activity were associated with decreasing probability of detectable CRP, but the effect was limited to periodontitis cases and was not apparent among non-cases. CONCLUSION: Leisure-time physical activity may protect against an excessive inflammatory response in periodontitis.

Periodontal ligament stem cell-mediated treatment for periodontitis in miniature swine.

Periodontitis is a periodontal tissue infectious disease and the most common cause for tooth loss in adults. It has been linked to many systemic disorders, such as coronary artery disease, stroke, and diabetes. At present, there is no ideal therapeutic approach to cure periodontitis and achieve optimal periodontal tissue regeneration. In this study, we explored the potential of using autologous periodontal ligament stem cells (PDLSCs) to treat periodontal defects in a porcine model of periodontitis. The periodontal lesion was generated in the first molars area of miniature pigs by the surgical removal of bone and subsequent silk ligament suture around the cervical portion of the tooth. Autologous PDLSCs were obtained from extracted teeth of the miniature pigs and then expanded ex vivo to enrich PDLSC numbers. When transplanted into the surgically created periodontal defect areas, PDLSCs were capable of regenerating periodontal tissues, leading to a favorable treatment for periodontitis. This study demonstrates the feasibility of using stem cell-mediated tissue engineering to treat periodontal diseases.

EphB/ephrin-B interaction mediates adult stem cell attachment, spreading, and migration: implications for dental tissue repair.

Human adult dental pulp stem cells (DPSCs) reside predominantly within the perivascular niche of dental pulp and are thought to originate from migrating neural crest cells during development. The Eph family of receptor tyrosine kinases and their ligands, the ephrin molecules, play an essential role in the migration of neural crest cells during development and stem cell niche maintenance. The present study examined the expression and function of the B-subclass Eph/ephrin molecules on DPSCs. Multiple receptors were primarily identified on DPSCs within the perivascular niche, whereas ephrin-B1 and ephrin-B3 were expressed by the surrounding pulp tissue. EphB/ephrin-B bidirectional signaling inhibited cell attachment and spreading, predominately via the mitogen-activated protein kinase (MAPK) pathway for forward signaling and phosphorylation of Src family tyrosine kinases via reverse ephrin-B signaling. DPSC migration was restricted through unidirectional ephrin-B1-activated EphB forward signaling, primarily signaling through the MAPK pathway. Furthermore, we observed that ephrin-B1 was downregulated in diseased adult teeth compared with paired uninjured controls. Collectively, these studies suggest that EphB/ephrin-B molecules play a role in restricting DPSC attachment and migration to maintain DPSCs within their stem cell niche under steady-state conditions. These results may have implications for dental pulp development and regeneration.

Investigation of multipotent postnatal stem cells from human periodontal ligament.

BACKGROUND: Periodontal diseases that lead to the destruction of periodontal tissues--including periodontal ligament (PDL), cementum, and bone--are a major cause of tooth loss in adults and are a substantial public-health burden worldwide. PDL is a specialised connective tissue that connects cementum and alveolar bone to maintain and support teeth in situ and preserve tissue homoeostasis. We investigated the notion that human PDL contains stem cells that could be used to regenerate periodontal tissue. METHODS: PDL tissue was obtained from 25 surgically extracted human third molars and used to isolate PDL stem cells (PDLSCs) by single-colony selection and magnetic activated cell sorting. Immunohistochemical staining, RT-PCR, and northern and western blot analyses were used to identify putative stem-cell markers. Human PDLSCs were transplanted into immunocompromised mice (n=12) and rats (n=6) to assess capacity for tissue regeneration and periodontal repair. Findings PDLSCs expressed the mesenchymal stem-cell markers STRO-1 and CD146/MUC18. Under defined culture conditions, PDLSCs differentiated into cementoblast-like cells, adipocytes, and collagen-forming cells. When transplanted into immunocompromised rodents, PDLSCs showed the capacity to generate a cementum/PDL-like structure and contribute to periodontal tissue repair. INTERPRETATION: Our findings suggest that PDL contains stem cells that have the potential to generate cementum/PDL-like tissue in vivo. Transplantation of these cells, which can be obtained from an easily accessible tissue resource and expanded ex vivo, might hold promise as a therapeutic approach for reconstruction of tissues destroyed by periodontal diseases.