The immunopathogenesis of periodontal disease

Comparison of growth factor levels in injectable platelet-rich fibrin obtained from healthy individuals and patients with chronic periodontitis: a pilot study

BACKGROUND

This study aimed to assess and compare the concentrations of growth factors, white blood cells (WBCs), and platelets in injectable platelet-rich fibrin (i-PRF) derived from people with healthy periodontal conditions and those with chronic periodontitis.

METHODS

Venous blood samples were obtained from 30 patients diagnosed with chronic periodontitis (test group) and 30 participants with healthy periodontal conditions (control group). The i-PRF was then acquired from centrifuged blood. The growth factors (VEGF, IGF-1, TGF-β1, PDGF-BB and EGF) released from the i-PRF samples were compared between groups with ELISA testing. The amounts of WBCs and platelets were also compared.

RESULTS

No significant differences in the concentrations of growth factors were found between the groups (the mean values for the control and test groups were, respectively: IGF: 38.82, 42.46; PDGF: 414.25, 466.28; VEGF: 375.69, 412.18; TGF-β1: 21.50, 26.21; EGF: 138.62, 154.82). The test group exhibited a significantly higher WBC count than the control group (8.80 vs. 6.60, respectively). However, the platelet count did not show a statistically significant difference between the groups (control group 242.0 vs. test group 262.50). No significant correlation was observed between WBC count and growth factor level in either group.

CONCLUSIONS

The growth factor levels in i-PRFs did not exhibit significant difference between the two groups. This suggests that the levels of these growth factors may be unaffected by the periodontal disease.

Analysis of inflammation and bone remodeling of atmospheric plasma therapy in experimental periodontitis

BACKGROUND AND OBJECTIVE

The biological effects of atmospheric plasma (cold plasma) show its applicability for controlling the etiological factors that involve tissue repair. Thus, the study evaluated the effect of atmospheric plasma therapy in the control of tissue inflammation and bone remodeling in experimental periodontitis.

METHODS

Fifty-six rats were subjected to ligation in the cervical region of the first maxillary molars (8 weeks). The animals were divided into two groups (n = 28): periodontitis without treatment group (P group), and periodontitis with atmospheric plasma treatment group (P + AP group). Tissue samples were collected at 2 and 4 weeks after treatment to analyze the inflammation and bone remodeling by biochemical, histomorphometric, and immunohistochemical analyses.

RESULTS

Inflammatory infiltration in the gingival and periodontal ligament was lower in the P + AP group than in the P group (p < .05). The MPO and NAG levels were higher in the P + AP group compared to P group (p < .05). At 4 weeks, the TNF-α level was lower and the IL-10 level was higher in the P + AP group compared to P group (p < .05). In the P + AP group, the IL-1β level increased in the second week and decreased in the fourth week (p < .05), the number of blood vessels was high in the gingival and periodontal ligament in the second and fourth week (p < .05); and the number of fibroblasts in the gingival tissue was low in the fourth week, and higher in the periodontal tissue in both period (p < .05). Regarding bone remodeling, the RANK and RANKL levels decreased in the P + AP group (p < .05). The OPG level did not differ between the P and P + AP groups (p > .05), but decreased from the second to the fourth experimental week in P + AP group (p < .05).

CONCLUSIONS

The treatment of experimental periodontitis with atmospheric plasma for 4 weeks modulated the inflammatory response to favor the repair process and decreased the bone resorption biomarkers, indicating a better control of bone remodeling in periodontal disease.

The impacts of oral and gut microbiota on alveolar bone loss in periodontitis

Periodontitis, a chronic infectious disease, primarily arises from infections and the invasion of periodontal pathogens. This condition is typified by alveolar bone loss resulting from host immune responses and inflammatory reactions. Periodontal pathogens trigger aberrant inflammatory reactions within periodontal tissues, thereby exacerbating the progression of periodontitis. Simultaneously, these pathogens and metabolites stimulate osteoclast differentiation, which leads to alveolar bone resorption. Moreover, a range of systemic diseases, including diabetes, postmenopausal osteoporosis, obesity and inflammatory bowel disease, can contribute to the development and progression of periodontitis. Many studies have underscored the pivotal role of gut microbiota in bone health through the gut-alveolar bone axis. The circulation may facilitate the transfer of gut pathogens or metabolites to distant alveolar bone, which in turn regulates bone homeostasis. Additionally, gut pathogens can elicit gut immune responses and direct immune cells to remote organs, potentially exacerbating periodontitis. This review summarizes the influence of oral microbiota on the development of periodontitis as well as the association between gut microbiota and periodontitis. By uncovering potential mechanisms of the gut-bone axis, this analysis provides novel insights for the targeted treatment of pathogenic bacteria in periodontitis.

Ageing and Inflammation: What Happens in Periodontium?

Periodontitis is a chronic inflammatory disease with a high incidence and severity in the elderly population, making it a significant public health concern. Ageing is a primary risk factor for the development of periodontitis, exacerbating alveolar bone loss and leading to tooth loss in the geriatric population. Despite extensive research, the precise molecular mechanisms underlying the relationship between ageing and periodontitis remain elusive. Understanding the intricate mechanisms that connect ageing and inflammation may help reveal new therapeutic targets and provide valuable options to tackle the challenges encountered by the rapidly expanding global ageing population. In this review, we highlight the latest scientific breakthroughs in the pathways by which inflammaging mediates the decline in periodontal function and triggers the onset of periodontitis. We also provide a comprehensive overview of the latest findings and discuss potential avenues for future research in this critical area of investigation.

New insights into inflammatory osteoclast precursors as therapeutic targets for rheumatoid arthritis and periodontitis

Rheumatoid arthritis (RA) and periodontitis are chronic inflammatory diseases leading to increased bone resorption. Preventing this inflammatory bone resorption is a major health challenge. Both diseases share immunopathogenic similarities and a common inflammatory environment. The autoimmune response or periodontal infection stimulates certain immune actors, leading in both cases to chronic inflammation that perpetuates bone resorption. Moreover, RA and periodontitis have a strong epidemiological association that could be explained by periodontal microbial dysbiosis. This dysbiosis is believed to be involved in the initiation of RA via three mechanisms. (i) The dissemination of periodontal pathogens triggers systemic inflammation. (ii) Periodontal pathogens can induce the generation of citrullinated neoepitopes, leading to the generation of anti-citrullinated peptide autoantibodies. (iii) Intracellular danger-associated molecular patterns accelerate local and systemic inflammation. Therefore, periodontal dysbiosis could promote or sustain bone resorption in distant inflamed joints. Interestingly, in inflammatory conditions, the existence of osteoclasts distinct from "classical osteoclasts" has recently been reported. They have proinflammatory origins and functions. Several populations of osteoclast precursors have been described in RA, such as classical monocytes, a dendritic cell subtype, and arthritis-associated osteoclastogenic macrophages. The aim of this review is to synthesize knowledge on osteoclasts and their precursors in inflammatory conditions, especially in RA and periodontitis. Special attention will be given to recent data related to RA that could be of potential value in periodontitis due to the immunopathogenic similarities between the two diseases. Improving our understanding of these pathogenic mechanisms should lead to the identification of new therapeutic targets involved in the pathological inflammatory bone resorption associated with these diseases.

Unique inverse association between allergic rhinitis and periodontitis: a nationwide population-based study

The increase in fine dust levels in the atmosphere has been associated with a growth in the incidence of environmental diseases, including allergic rhinitis (AR). Nasal obstruction caused by AR can impact the conditions in the oral cavity. The aim of this study was to determine the association between AR and periodontitis in the Republic of Korea. This study was based on data from the Seventh Korea National Health and Nutrition Examination Survey (KNHANES VII-1, 2016), which was conducted by the Korea Centers for Disease Control and Prevention. The study included 6129 adults older than 19 years. Sociodemographic information and medical variables including history of treatment of periodontitis (HTP) reflecting diagnosis of periodontitis and diagnosis of diseases such as AR were extracted from the data. HTP and AR were reported for 22.81 ± 0.84% (weighted percentage ± standard error) and 15.32 ± 0.63% of the studied population, respectively. A diagnosis of AR was reported for 11.07 ± 1.28% of those with HTP and for 17.55 ± 1.84% of those without HTP. From these, it was inferred that the prevalence of HTP was 1.536-fold higher in the non-AR group than in their counterparts with AR. Significant association was found between AR and HTP among those aged ≤ 64 years and the odds ratio (OR) of AR group for HTP was 0.62 (95% confidence interval:0.44-0.87; P = 0.0057). From this result, it can be inferred that patients diagnosed AR have lower risk of periodontitis.

Protective effect of Chromobacterium violaceum and violacein against bone resorption by periodontitis

OBJECTIVES

The aim of this study was to evaluate the potential protective effect of Chromobacterium violaceum and violacein against periodontitis, in experimental models.

MATERIALS AND METHODS

A double-blind experimental study on the exposure to C. violaceum or violacein in experimentally ligature-induced periodontitis, as preventive factors against alveolar bone loss by periodontitis. Bone resorption was assessed by morphometry. Antibacterial potential of violacein was assessed in an in vitro assay. Its cytotoxicity and genotoxicity were evaluated using the Ames test and SOS Chromotest assay, respectively.

RESULTS

The potential of C. violaceum to prevent/limit bone resorption by periodontitis was confirmed. Daily exposure to 106 cells/ml in water intake since birth and only during the first 30 days of life significantly reduced bone loss from periodontitis in teeth with ligature. Violacein extracted from C. violaceum was efficient in inhibiting or limiting bone resorption and had a bactericidal effect against Porphyromonas gingivalis in the in vitro assay.

CONCLUSIONS

We conclude that C. violaceum and violacein have the potential to prevent or limit the progression of periodontal diseases, in an experimental model.

CLINICAL RELEVANCE

The effect of an environmental microorganism with potential action against bone loss in animal models with ligature-induced periodontitis represents the possibility of understanding the etiopathogenesis of periodontal diseases in populations exposed to C. violaceum and the possibility of new probiotics and antimicrobials. This would imply new preventive and therapeutic possibilities.

Oral Health of Patients Undergoing Percutaneous Coronary Intervention-A Possible Link between Periodontal Disease and In-Stent Restenosis

Introduction: There is a well-documented association between coronary artery disease (CHD) and periodontal disease (PD) mediated by common inflammatory pathways. This association, however, has not been investigated extensively in the special context of in-stent restenosis. This study aimed to investigate the periodontal status of patients undergoing percutaneous coronary intervention (PCI) for restenotic lesions. Methods and Results: We enrolled 90 patients undergoing percutaneous coronary intervention and 90 age- and gender-matched healthy controls in the present study. All subjects received a full-mouth examination by a periodontist. Plaque index, periodontal status, and tooth loss were determined. The periodontal state was significantly worse (p < 0.0001) in the PCI group, and each periodontal stage increased the odds of belonging to the PCI group. This effect of PD was independent of diabetes mellitus, another strong risk factor for CAD. The PCI group was further divided into two subgroups: PCI for restenotic lesions (n = 39) and PCI for de novo lesions (n = 51). Baseline clinical and procedural characteristics were comparable between the two PCI subgroups. A significant (p < 0.001) association was found between the PCI subgroup and the severity of periodontal disease, with the incidence of severe PD reaching 64.1%. Conclusions: Patients undergoing PCI for in-stent restenosis exhibit more severe forms of periodontal disease not only as compared to healthy controls but also as compared to patients stented for de novo lesions. The potential causality between PD and restenosis must be studied in larger prospective studies.

Porphyromonas gingivalis-induced periodontitis could contribute to cognitive impairment in Sprague–Dawley rats via the P38 MAPK signaling pathway

Background

Periodontitis is one of the most common oral diseases and has been shown to be a risk factor for systemic diseases. Our aim was to investigate the relationship between periodontitis and cognitive impairment and to explore the role of the P38 MAPK signaling pathway in this process.

Methods

We established a periodontitis model by ligating the first molars of SD rats with silk thread and injecting Porphyromonas gingivalis (P. gingivalis) or P. gingivalis plus the P38 MAPK inhibitor SB203580 at the same time for ten weeks. We assessed alveolar bone resorption and spatial learning and memory using microcomputed tomography and the Morris water maze test, respectively. We used transcriptome sequencing to explore the genetic differences between the groups. The gingival tissue, peripheral blood and hippocampal tissue were assessed for the cytokines TNF-α, IL-1β, IL-6, IL-8 and C reactive protein (CRP) with enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT–PCR). We observed the presence of P. gingivalis in the hippocampus of rats by paraffin-fluorescence in situ hybridization (FISH). We determined the activation of microglia by immunofluorescence. Finally, Western blot analysis was employed to determine the expression of amyloid precursor protein (APP), β-site APP-cleaving enzyme 1 (BACE1) and P38MAPK pathway activation.

Results

We demonstrated that silk ligature-induced periodontitis plus injection of P. gingivalis into subgingival tissue could lead to memory and cognitive impairment. Transcriptome sequencing results suggested that there were neurodegenerative diseases in the P. gingivalis group, and the MWM test showed that periodontitis reduced the spatial learning and memory ability of mild cognitive impairment (MCI) model rats. We found high levels of inflammatory factors (TNF-α, IL-1β, IL-6, and IL-8) and CRP in the gingiva, peripheral blood and hippocampus, and the expression of APP and BACE1 was upregulated, as was the P38 MAPK pathway activation. Activated microglia and the presence of P. gingivalis were also found in the hippocampus. P38 MAPK inhibitors mitigated all of these changes.

Conclusion

Our findings strongly suggest that topical application of P. gingivalis increases the inflammatory burden in the peripheral and central nervous systems (CNS) and that neuroinflammation induced by activation of P38 MAPK leads to impaired learning and memory in SD rats. It can also modulate APP processing. Therefore, P38 MAPK may serve as a linking pathway between periodontitis and cognitive impairment.

Could AMPs and B-cells be the missing link in understanding periodontitis?

Periodontal diseases are common inflammatory conditions characterized by bone loss in response to simultaneous bacterial aggression and host defenses. The etiology of such diseases is still not completely understood, however. It has been shown that specific pathogens involved in the build-up of dysbiotic biofilms participate actively in the establishment of periodontitis. This multifactorial pathology also depends on environmental factors and host characteristics, especially defenses. The immune response to the pathogens seems to be critical in preventing the disease from starting but also contributes to tissue damage. It is known that small molecules known as antimicrobial peptides (AMPs) are key actors in the innate immune response. They not only target microbes, but also act as immuno-modulators. They can help to recruit or activate cells such as neutrophils, monocytes, dendritic cells, or lymphocytes. AMPs have already been described in the periodontium, and their expression seems to be connected to disease activity. Alpha and beta defensins and LL37 are the AMPs most frequently linked to periodontitis. Additionally, leukocyte infiltrates, especially B-cells, have also been linked to the severity of periodontitis. Indeed, the particular subpopulations of B-cells in these infiltrates have been linked to inflammation and bone resorption. A link between B-cells and AMP could be relevant to understanding B-cells' action. Some AMP receptors, such as chemokines receptors, toll-like receptors, or purinergic receptors, have been shown to be expressed by B-cells. Consequently, the action of AMPs on B-cell subpopulations could participate to B-cell recruitment, their differentiation, and their implication in both periodontal defense and destruction.

Gingival tissue antibody gene utilization in aging and periodontitis

OBJECTIVE

This study used a nonhuman primate model of ligature-induced periodontitis to document the characteristics of immunoglobulin (Ig) gene usage in gingival tissues with disease and affected by age.

BACKGROUND

Adaptive immune responses to an array of oral bacteria are routinely detected in local gingival tissues and the systemic circulation across the human population. The level and diversity of antibody increases with periodontitis, reflecting the increased quantity of B cells and plasmacytes in the tissues at sites of periodontal lesions.

METHODS

Macaca mulatta (n = 36) in four groups (young - ≤3 years; adolescent >3-7 years; adult - 12-15 years; aged - 17-23 years) were used in this study. Gingival tissues were sampled at baseline (health), 2 weeks (initiation), 1 and 3 months (progression), and 5 months (resolution) of the lesion development and transcriptomic analysis included 78 Ig-related genes.

RESULTS

The results demonstrated extensive variation in Ig gene usage patterns and changes with the disease process that was substantially affected by the age of the animal. Of note was that the aged animals generally demonstrated elevated expression on multiple Ig genes even in the baseline/healthy gingival tissues. The expression levels revealed 5 aggregates of Ig gene change profiles across the age groups. The number of gene changes were greatly increased in adult animals with the initiation of disease, while the young and adolescent animals showed extensive changes with disease progression. Elevated Ig gene transcripts remained with disease resolution except in the aged animals. The response profiles demonstrated selective heavy/light change gene transcripts that differed with age and clustering of the transcript expression was dominated by the age of the animals.

CONCLUSIONS

The results suggested potential critical variations in the molecular aspects of Ig gene expression in gingival tissues that can contribute to understanding the kinetics of periodontal lesions, as well as the variation in episodes, rapidity of progression, and role in resolution that are impacted by age.

Gut-Bone Axis: A Non-Negligible Contributor to Periodontitis

Periodontitis is a polymicrobial infectious disease characterized by alveolar bone loss. Systemic diseases or local infections, such as diabetes, postmenopausal osteoporosis, obesity, and inflammatory bowel disease, promote the development and progression of periodontitis. Accumulating evidences have revealed the pivotal effects of gut microbiota on bone health via gut-alveolar-bone axis. Gut pathogens or metabolites may translocate to distant alveolar bone via circulation and regulate bone homeostasis. In addition, gut pathogens can induce aberrant gut immune responses and subsequent homing of immunocytes to distant organs, contributing to pathological bone loss. Gut microbial translocation also enhances systemic inflammation and induces trained myelopoiesis in the bone marrow, which potentially aggravates periodontitis. Furthermore, gut microbiota possibly affects bone health via regulating the production of hormone or hormone-like substances. In this review, we discussed the links between gut microbiota and periodontitis, with a particular focus on the underlying mechanisms of gut-bone axis by which systemic diseases or local infections contribute to the pathogenesis of periodontitis.

Molecular Basis of Accelerated Aging with Immune Dysfunction-Mediated Inflammation (Inflamm-Aging) in Patients with Systemic Sclerosis

Systemic sclerosis (SSc) is a chronic connective tissue disorder characterized by immune dysregulation, chronic inflammation, vascular endothelial cell dysfunction, and progressive tissue fibrosis of the skin and internal organs. Moreover, increased cancer incidence and accelerated aging are also found. The increased cancer incidence is believed to be a result of chromosome instability. Accelerated cellular senescence has been confirmed by the shortening of telomere length due to increased DNA breakage, abnormal DNA repair response, and telomerase deficiency mediated by enhanced oxidative/nitrative stresses. The immune dysfunctions of SSc patients are manifested by excessive production of proinflammatory cytokines IL-1, IL-6, IL-17, IFN-α, and TNF-α, which can elicit potent tissue inflammation followed by tissue fibrosis. Furthermore, a number of autoantibodies including anti-topoisomerase 1 (anti-TOPO-1), anti-centromere (ACA or anti-CENP-B), anti-RNA polymerase enzyme (anti-RNAP III), anti-ribonuclear proteins (anti-U1, U2, and U11/U12 RNP), anti-nucleolar antigens (anti-Th/T0, anti-NOR90, anti-Ku, anti-RuvBL1/2, and anti-PM/Scl), and anti-telomere-associated proteins were also found. Based on these data, inflamm-aging caused by immune dysfunction-mediated inflammation exists in patients with SSc. Hence, increased cellular senescence is elicited by the interactions among excessive oxidative stress, pro-inflammatory cytokines, and autoantibodies. In the present review, we will discuss in detail the molecular basis of chromosome instability, increased oxidative stress, and functional adaptation by deranged immunome, which are related to inflamm-aging in patients with SSc.

Vascular Changes and Hypoxia in Periodontal Disease as a Link to Systemic Complications

The hypoxic microenvironment caused by oral pathogens is the most important cause of the disruption of dynamic hemostasis between the oral microbiome and the immune system. Periodontal infection exacerbates the inflammatory response with increased hypoxia and causes vascular changes. The chronicity of inflammation becomes systemic as a link between oral and systemic diseases. The vascular network plays a central role in controlling infection and regulating the immune response. In this review, we focus on the local and systemic vascular network change mechanisms of periodontal inflammation and the pathological processes of inflammatory diseases. Understanding how the vascular network influences the pathology of periodontal diseases and the systemic complication associated with this pathology is essential for the discovery of both local and systemic proactive control mechanisms.

Inflamm-Aging-Related Cytokines of IL-17 and IFN-γ Accelerate Osteoclastogenesis and Periodontal Destruction

Periodontal disease (PD), as an age-related disease, prevalent in middle-aged and elderly population, is characterized as inflammatory periodontal tissue loss, including gingival inflammation and alveolar bone resorption. However, the definite mechanism of aging-related inflammation in PD pathology needs further investigation. Our study is aimed at exploring the effect of inflamm-aging-related cytokines of interleukin-17 (IL-17) and interferon-γ (IFN-γ) on osteoclastogenesis in vitro and periodontal destruction in vivo. For receptor activator of nuclear factor-κB ligand- (RANKL-) primed bone marrow macrophages (BMMs), IL-17 and IFN-γ enhanced osteoclastogenesis, with the expression of osteoclastogenic mRNA (TRAP, c-Fos, MMP-9, Ctsk, and NFATc1) and protein (c-Fos and MMP-9) upregulated. Ligament-induced rat models were established to investigate the role of IL-17 and IFN-γ on experimental periodontitis. Both IL-17 and IFN-γ could enhance the local inflammation in gingival tissues. Although there might be an antagonistic interaction between IL-17 and IFN-γ, IL-17 and IFN-γ could facilitate alveolar bone loss and osteoclast differentiation.

Metabolic Disturbance and Th17/Treg Imbalance Are Associated With Progression of Gingivitis

Objective

This study sought to explore the role of metabolic disturbance in immunoregulation of gingivitis targeting T helper 17 cells (Th17)/regulatory T cell (Treg).

Materials and Methods

A total of 20 gingivitis patients and 19 healthy volunteers were recruited. Quantitative real time polymerase chain reaction (qRT-PCR) was used to evaluate expression patterns of Forkhead box protein P3 (Foxp3), transforming growth factor-β (TGF-β), retinoid-related orphan receptor-gammat (RORγt) and interleukin 17A (IL-17A) in the peripheral blood lymphocytes of subjects across the two groups. Moreover, the enzyme-linked immunosorbent assay (ELISA) technique was used to detect levels of TGF-β, IL-4, IL-6,TL-10 and L-17A secreted in the plasma as well as the SIgA secreted in saliva. Flow cytometry was used to detect the percentage of CD4⁺CD25⁺ Foxp3⁺Treg cells and the percentage of CD4⁺IL-17A⁺ Th17 cells in whole blood of subjects in both groups. Gas chromatography-mass spectrometry (GC-MS) was employed to analyze the plasma metabolites in the gingivitis patient group. Statistical analysis was applied to determine whether the plasma metabolites and related metabolic pathways significantly differed between gingivitis patients and healthy controls. Ingenuity pathway analysis (IPA) was employed to identify the potential relation between the metabolites and the Th17 and Treg related pathway.

Results

The percentages of CD4⁺IL17A⁺Th17 cells and IL-17 significantly increased in the peripheral blood in the gingivitis group. Moreover, the upregulation of IL-17A mRNA and RORγt mRNA were also found in the gingivitis group. However, the percentage of CD4⁺CD25⁺ Foxp3⁺Treg cells and Foxp3 mRNA in the whole blood did not significantly change. However, TGF-β mRNA as well as TGF-β, IL-4, IL-6, IL-10 in the periperial blood and SIgA in the saliva were higher in the gingivitis group. Notably, that the ratio of Th17/Treg cells was significantly increased during peripheral circulation. Furthermore, we identified 18 different metabolites which were differentially expressed in plasma between the gingivitis and healthy control groups. Notably, the levels of cholesterol, glycerol 1-octadecanoate, d-glucose, uric acid, cyclohexaneacetic acid, 3-pyridine, tryptophan, and undecane 2,4-dimethyl were significantly up-regulated. whereas the levels of lactic acid, glycine, linoleic acid, monopalmitic acid, glycerol, palmitic acid, pyruvate, 1-(3-methylbutyl)-2,3,4,6-tetramethylbenzene, 1 5-anhydro d-altrol, and boric acid were down-regulated in the gingivitis group, relative to healthy controls. IPA showed that these metabolites are connected to IL17 signaling, TGF-B signaling, and IL10 signaling, which are related closely to Th17 and Treg pathway.

Conclusion

Overall, these results showed that disturbance to glycolysis as well as amino and fatty acid metabolism are associated with Th17/Treg balance in gingivitis. Impaired immunometabolism may influence some periodontally involved systemic diseases, hence it is a promising strategy in targeted development of treatment therapies.

Adjuvant Transgingival Therapy with Visible Light Plus Water-Filtered Infrared-A (VIS + wIRA) in Periodontal Therapy-A Randomized, Controlled, Stratified, Double-Blinded Clinical Trial

The aim of this randomized, controlled, double-blinded clinical trial was to examine the additional healing effect of transgingival visible light and water-filtered infrared-A (VIS + wIRA) in the treatment of periodontitis patients compared with the standard therapy by subgingival instrumentation (SI). Therefore, forty patients with untreated periodontitis received a non-surgical periodontal treatment. Using a split-mouth study design, one quadrant of the upper jaw was randomly either exposed to VIS + wIRA four times for 20 min within two weeks in addition to SI or received only SI. Three and 6 months after intervention, clinical parameters (probing depths (PDs), clinical attachment level, bleeding on probing (BOP), furcation, tooth mobility, plaque control record, and papilla bleeding index) were re-evaluated. In the presence of PD of 4 mm and positive BOP or PD > 4 mm, SI was performed again. Moreover, the patients were asked about their discomfort using a visual analog scale from 1 to 10 for each side of the maxilla. Statistical analysis demonstrated no differences between quadrants at re-evaluation for clinical parameters (p > 0.05) after 3 and 6 months. Concerning pain perception, patients described less pain on the irradiated side (p = 0.016). In the treatment of patients with periodontitis, VIS + wIRA did not show an additional effect on the clinical outcome after 3 and 6 months. Patients described less pain on the irradiated quadrant after treatment.

LuxS quorum sensing system and biofilm formation of oral microflora: A short review article

The LuxS quorum sensing system is considered as the main system that most of the oral bacteria use to communicate in order to create biofilms. Here we identified 11 of the most important biofilm formers that utilize the LuxS system and presented current and recent information regarding this system. Though different bacterial species are able to communicate thorough the LuxS system, it was also found that cross kingdom communication can occur between bacteria and fungi and bacteria and epithelial cells. Immune response also plays and important role in mitigating the effects of biofilms. Here we identified 6 of the most important molecules that are involved in the immune response to biofilms. These immune molecules maintain the stability in the oral cavity by preventing bacteria from overwhelming the space and simultaneously minimizing the immune response in order not to cause tissue damage. Here we also discuss current research being done in order to maintain the balance in the oral cavity via inhibiting biofilm formation without eradicating oral bacteria in order to prevent the overgrowth of other organisms such as Candida albicans. One approach being used is inhibiting AI-2 intermediates which leads to lack of quorum sensing communication between bacteria through the use of intermediate analogues. Another approach that found success is the utilization of D forms of sugars where D-ribose and D-galactose have been proven to inhibit the LuxS system and subsequently preventing the process of quorum sensing leading to the reduction in biofilm formation.

The possible role of oral microbiome in autoimmunity

OBJECTIVE

The human microbiome refers to the entire habitat, including microorganisms, their genomes and the surrounding environmental conditions of the microbial ecosystem. When the equilibrium between microbial habitats and host is disturbed, dysbiosis is caused. The oral microbiome (OMB) has been implicated in the manifestation of many intra- and extraoral diseases. Lately, there has been an intense effort to investigate and specify the relationship between microbial complexes, especially that of the oral cavity and intestine and autoimmunity. This study aimed to review the current literature about the possible role of the OMB in the pathogenesis of autoimmune diseases.

METHODS

We searched for published articles in English indexed in PubMed, Medline, Research Gate and Google Scholar using a search strategy that included terms for oral microbiome, autoimmune diseases, dysbiosis and next-generation sequencing.

RESULTS

An important number of articles were gathered and used for the description of the possible impact of dysbiosis of OMB in the pathogenesis of Sjögren's syndrome, systemic lupus erythematosus, rheumatoid arthritis, Behcet's disease, Crohn's disease and psoriasis.

CONCLUSION

This review article draws attention to the relationship between OMB and the triggering of a number of autoimmune diseases. Although this specific topic has been previously reviewed, herein, the authors review recent literature regarding the full list of nosological entities related to the OMB, point out the interaction between the microbiome and sex hormones with regard to their role in autoimmunity and discuss novel and promising therapeutic approaches for systemic autoimmune diseases. Furthermore, the question arises of whether the OMB is associated with oral bullous autoimmune diseases.

Immunopathogenesis of canine chronic ulcerative stomatitis

Canine Chronic Ulcerative Stomatitis is a spontaneously occurring inflammatory disease of the oral mucosa. An immune-mediated pathogenesis is suspected though not yet proven. We have recently reported on the clinical and histologic features, and identification of select leukocyte cell populations within the lesion. A clinical and histologic similarity to oral lichen planus of people was proposed. In the present study, these initial observations are extended by examining lesions from 24 dogs with clinical evidence of chronic ulcerative stomatitis. Because dogs with chronic ulcerative stomatitis often have concurrent periodontal disease, we wondered if dental plaque/biofilm may be a common instigator of inflammation in both lesions. We hypothesized that dogs with chronic ulcerative stomatitis would exhibit a spectrum of pathologic changes and phenotype of infiltrating leukocytes that would inform lesion pathogenesis and that these changes would differ from inflammatory phenotypes in periodontitis. Previously we identified chronic ulcerative stomatitis lesions to be rich in FoxP3+ and IL17+ cells. As such, we suspect that these leukocytes play an important role in lesion pathogenesis. The current study confirms the presence of moderate to large numbers of FoxP3+ T cells and IL17+ cells in all ulcerative stomatitis lesions using confocal immunofluorescence. Interestingly, the majority of IL17+ cells were determined to be non-T cells and IL17+ cell frequencies were negatively correlated with severity on the clinical scoring system. Three histologic subtypes of ulcerative stomatitis were determined; lichenoid, deep stomatitis and granulomatous. Periodontitis lesions, like stomatitis lesions, were B cell and plasma cell rich, but otherwise differed from the stomatitis lesions. Direct immunofluorescence results did not support an autoantibody-mediated autoimmune disease process. This investigation contributes to the body of literature regarding leukocyte involvement in canine idiopathic inflammatory disease pathogenesis.

Levels of pro- and anti-inflammatory cytokines in cystic fibrosis patients with or without gingivitis

BACKGROUND

Inflammatory periodontal diseases are caused by interaction between gram negative, anaerobic bacteria and host response. Persistent infection of Pseudomonas aeruginosa in cystic fibrosis (CF) patients also cause increased pro-inflammatory response and the imbalance of pro- and anti-inflammatory response in brochoalveolar lavage fluid which leads to destruction of lungs. The aim of this study is to evaluate periodontal status of CF patients, to measure level of cytokines and biochemical molecules in gingival crevicular fluid (GCF), and to detect presence of P. aeruginosa in dental plaque samples.

MATERIALS AND METHODS

GCF samples were collected from 41 CF patients and 39 healthy (non-CF) subjects. Interleukin (IL)-1ß, IL-17, IL-10, human neutrophil elastase (HNE), cystic fibrosis transmembrane regulator (CFTR) protein, and human β-defensin-1 (HBD1) in GCF were evaluated by ELISA method. Dental plaque samples were collected from 18 CF patients with history of P. aeruginosa colonization and 15 non-CF subjects. Presence of P. aeruginosa was evaluated by using conventional culture methods and molecular methods.

RESULTS

Levels of IL-1ß, HNE, and HBD1 in CF patients were significantly higher than non-CF subjects. However, IL-10 level was significantly lower in CF patients. Increased pro-inflammatory (IL-1ß) and decreased anti-inflammatory (IL-10) cytokine levels were observed in GCF samples from CF patients, irrespective of their periodontal status. P. aeruginosa were detected in four samples of 18 CF patients, and all were negative in non-CF group.

CONCLUSIONS

As a result of this study, CF coexists increasing pro-inflammatory and decreasing anti-inflammatory response locally. Due to increasing pro-inflammation, CF patients should be followed-up more often than non-CF children.

FOXP3+ and CD25+ cells are reduced in patients with stage IV, grade C periodontitis: A comparative clinical study

BACKGROUND AND OBJECTIVE

Some studies suggest that regulatory T cells (Tregs) have suppressive effects on inflammatory osteolysis. The aim of this study was to evaluate Treg immunomarkers in periodontitis-affected tissues from patients with periodontitis and clinically healthy gingiva (control).

MATERIAL AND METHODS

The presence and distribution of positive cells for CD4, CD25 and FOXP3 (Treg immunomarkers) in periodontitis-affected tissues (epithelium and lamina propria) of 30 patients (ten per group) with a diagnosis of stage IV, grade C periodontitis (IV-C), stage III, grade B periodontitis (III-B) and the control were evaluated. A two-way ANOVA followed by Fisher's LSD test was used to demonstrate differences between the groups and immunomarkers; Student's t test was used to demonstrate differences between the epithelium and the lamina propria.

RESULTS

Both IV-C and III-B periodontitis presented a significantly high proportion of immune-stained cells for all immunomarkers when compared to the control group. Notably, CD25+ and FOXP3+ cells were detected in a significantly higher number in III-B than IV-C periodontitis (P < .05).

CONCLUSION

Our results suggest the participation of Tregs on the osteoimmunological mechanisms in IV-C and III-B periodontitis patients, notably contributing to strategies for alveolar bone regeneration in clinical treatment decisions.

Calcitriol suppresses lipopolysaccharide-induced alveolar bone damage in rats by regulating T helper cell subset polarization

BACKGROUND

Although the immunomodulatory properties of calcitriol in bone metabolism have been documented for decades, its therapeutic role in the management of periodontitis remains largely unexplored. In this study, we hypothesized that calcitriol suppresses lipopolysaccharide (LPS)-induced alveolar bone loss by regulating T helper (Th) cell subset polarization.

METHODS

To test this hypothesis, we determined the effect of calcitriol intervention on the development of LPS-induced periodontitis in rats in terms of bone loss (micro-CT analysis), local inflammatory infiltration levels, the number of osteoclasts (hematoxylin and eosin staining) and the level of osteoclastogenesis (tartrate-resistant acid phosphatase method). Furthermore, immunohistochemistry was used to assess the expression levels of the receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG) as well as the cytokine levels of interferon-γ (IFN-γ), interleukin-4 (IL-4), IL-17, and IL-10 throughout the LPS-injected region. Finally, the polarization potential of Th cells in peripheral blood was analyzed using flow cytometry.

RESULTS

Calcitriol intervention decreased alveolar bone loss in response to LPS injection and inflammatory cell infiltration. Analysis of osteoclast number and RANKL and OPG expression showed that bone resorption activity was largely suppressed in response to calcitriol administration, along with decreased IL-17 levels but increased IL-4 and IL-10 levels in periodontal tissues (the LPS-injected region). Similarly, the percentages of Th2 and Treg cells in peripheral blood increased, but the percentages of Th1 and Th17 cells decreased in rats receiving calcitriol.

CONCLUSION

Our findings suggest that calcitriol can be used to inhibit bone loss in experimental periodontitis, likely via the regulation of local and systemic Th cell polarization.

N-WASP knockdown upregulates inflammatory cytokines expression in human gingival fibroblasts

OBJECTIVE

The neuronal wiskott-aldrich syndrome protein (N-WASP) is a member of the wiskott-aldrich syndrome protein (WASP) family. N-WASP plays a vital role in promoting cell migration, receptor signaling and immune inflammatory responses. This study aimed to observe the changes in the expression of inflammatory factors and involving pathways after N-WASP knockdown in human gingival fibroblasts (HGFs).

DESIGN

Gingival inflammatory condition of N-WASP knockout mice was evaluated by H&E staining. N-WASP in HGFs was knockdown by siRNA and the best knockdown efficiency was determined by qRT-PCR and immunofluorescence. The mRNA levels of interleukin (IL)-6, IL-8, C-C motif ligand 2 (CCL2), superoxide dismutase 2 (SOD2) and prostaglandin endoperoxide synthase 2 (PTGS2) were evaluated by qRT-PCR after N-WASP knockdown with or without mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) inhibitors. The protein levels of IL-6, IL-8 and CCL2 were assessed by ELISA. Western blotting was used to detect the activation of NF-κB and MAPK signaling pathways.

RESULTS

Gingival tissue from N-WASP knockout mice exhibited an inflammatory reaction. The expression of IL-6, IL-8, CCL2, SOD2 and PTGS2 was significantly upregulated after N-WASP knockdown in HGFs for 6, 24 and 48 h, except for the SOD2 at 6 h. N-WASP knockdown significantly activated the signaling pathways of NF-κB and MAPK. The inhibitors of p65, p38, ERK and JNK clearly decreased IL-6, IL-8, CCL2, SOD2 and PTGS2 expression after N-WASP knockdown.

CONCLUSION

These data indicated that N-WASP deficiency in HGFs increases the production of inflammatory cytokine and is regulated via NF-κB and MAPK signaling pathways.

Candida spp. Determination and Th1/Th2 Mixed Cytokine Profile in Oral Samples From HIV+ Patients With Chronic Periodontitis

Background: Chronic periodontitis (CP), caused by bacteria and fungi, appears in up to 66% of HIV-patients. The impact and association of HIV-treatment (HAART) and Candida itself has not been properly evaluated in the development and progression of CP. The immunopathogenesis is characterized by CD4⁺ T-cells activation and the balance between the T-helper 1 (Th1) and T-helper 2 (Th2) or a mixed cytokine profile. Currently, the associated causes of an immune response in HIV-patients with CP is controversial. Our aims were the determination of Candida spp. and cytokine profile in oral samples from HIV-positive patients with CP, considering the CD4⁺ T cells levels and HAART use.

Methods: From 500 HIV-positive patients evaluated, 228 patients were enrolled. Patients were separated in groups: (A) n = 53 (≤200 CD4⁺ T-cells on HAART); (B) n = 57 (≤200 CD4⁺ T-cells without HAART); (C) n = 50 (>200 CD4⁺ T-cells without HAART); (D) n = 68 (>200 CD4⁺ T-cells on HAART). Candida spp. were isolated from the oral biofilm and crevicular fluid in CHROMagar and confirmed by endpoint PCR. Cytokine levels were measured by beads-based immunoassay in saliva by flow cytometry.

Results: 147 patients (64.5%) were positive to Candida spp. and 204 strains were isolated; 138 (67.6%) were C. albicans and the remaining C. non-albicans species (C. glabrata>C. tropicalis>C. krusei>C. dubliniensis). In this study, CHROMagar showed good sensitivity (95%) but poor specificity (68%); since of the 152 samples identified as C. albicans, only 131 were confirmed by PCR; from the 10 samples identified as C. glabrata, only six were confirmed. Finally, of the 42 samples detected as C. tropicalis, only five were confirmed. When evaluating Candida spp. presence, group A and D had higher isolation, while group B had the highest species diversity. Whereas, group C had a significant reduction of Candida spp. Despite the presence of Candida and HAART, we found a Th1/Th2 hybrid profile in the saliva of patients with low CD4⁺ T-cell count (group A).

Conclusion: Abundance and diversity of the Candida spp. detected in HIV-patients with CP could be related to HAART and low CD4⁺ T-cells levels. Also, the immunosuppression might promote a local Th1/Th2 hybrid cytokine profile.

Periodontal treatment prevents arthritis in mice and methotrexate ameliorates periodontal bone loss

Recent studies indicate a causal relationship between the periodontal pathogen P. gingivalis and rheumatoid arthritis involving the production of autoantibodies against citrullinated peptides. We therefore postulated that therapeutic eradication P. gingivalis may ameliorate rheumatoid arthritis development and here turned to a mouse model in order to challenge our hypothesis. F1 (DBA/1 x B10.Q) mice were orally inoculated with P. gingivalis before collagen-induced arthritis was provoked. Chlorhexidine or metronidazole were orally administered either before or during the induction phase of arthritis and their effects on arthritis progression and alveolar bone loss were compared to intraperitoneally injected methotrexate. Arthritis incidence and severity were macroscopically scored and alveolar bone loss was evaluated via microcomputed tomography. Serum antibody titres against P. gingivalis were quantified by ELISA and microbial dysbiosis following oral inoculation was monitored in stool samples via microbiome analyses. Both, oral chlorhexidine and metronidazole reduced the incidence and ameliorated the severity of collagen-induced arthritis comparable to methotrexate. Likewise, all three therapies attenuated alveolar bone loss. Relative abundance of Porphyromonadaceae was increased after oral inoculation with P. gingivalis and decreased after treatment. This is the first study to describe beneficial effects of non-surgical periodontal treatment on collagen-induced arthritis in mice and suggests that mouthwash with chlorhexidine or metronidazole may also be beneficial for patients with rheumatoid arthritis and a coexisting periodontitis. Methotrexate ameliorated periodontitis in mice, further raising the possibility that methotrexate may also positively impact on the tooth supporting tissues of patients with rheumatoid arthritis.

Osteoimmunology of tumor necrosis factor-alpha, IL-6, and RANTES/CCL5: a review of known and poorly understood inflammatory patterns in osteonecrosis

Background

The immune and bone systems are closely linked via cytokine cross-talk. This interdisciplinary field of research is referred to as osteoimmunology and pertains to inflammatory and osteoarticular diseases that feature the primary expression of tumor necrosis factor-alpha (TNF-α) and IL-6.

Objective

Are there bone resorptive processes wherein chronic inflammatory conditions are not linked to TNF-α and IL-6 expression, but rather to the expression of other cytokines?

Materials and methods

A comprehensive literature search was performed in PubMed Central.

Discussion

Although all diseases with cytokines involved in bone resorption (TNF-α and IL-6) are at the forefront of destructive inflammatory processes, there is one exception in the literature: fatty oxide osteoporosis/osteolysis in the jawbone (FDOJ), which is associated with significant bone softening. However, it should be noted that TNF-α and IL-6 fall below the levels found in a healthy jawbone in this condition. Another conspicuous finding is that there is a nearly 35-fold overexpression of the chemokine RANTES/CCL5 (R/C) in all FDOJ cases studied thus far in the literature.

Conclusion

FDOJ appears to represent a unique cytokine and inflammatory pattern from osteolysis in the body. R/C can be defined as the dominant carrier of a “maxillomandibular osteoimmunology”.

Reduced ADAM8 levels upon non-surgical periodontal therapy in patients with chronic periodontitis

OBJECTIVE

To determine effect of non-surgical periodontal treatment on a disintegrin and metalloproteinase 8 (ADAM8) levels in gingival crevicular fluid (GCF) of patients with chronic periodontitis (CP) in comparison with those of patients with gingivitis and to find correlations between ADAM8 levels and clinical parameters.

DESIGN

Twenty-two and eleven patients with CP and gingivitis, respectively, were examined for four clinical parameters, probing depth, clinical attachment level, gingival and plaque indices. GCF from the selected gingivitis or periodontitis sites with distinct severities was sampled by Periopaper strips. The non-surgical treatments, including scaling and/or root planing and oral hygiene instruction, were provided for all patients. Clinical measurements and GCF sampling were repeated at three months after the treatments. ADAM8 concentrations were analyzed by ELISA and normalized by GCF volumes or total protein amounts.

RESULTS

All patients exhibited significant improvement of almost every clinical parameter after treatment, whereas the median ADAM8 concentrations were significantly decreased at the moderate and severe periodontitis sites of patients with CP (p < 0.05). Moreover, the significantly positive correlations between ADAM8 concentrations and four clinical parameters were found in both moderate and severe groups (p < 0.05).

CONCLUSION

ADAM8 concentrations were decreased by non-surgical periodontal therapy in patients with chronic periodontitis at the moderate and severe sites and were correlated with four clinical parameters, implying that GCF ADAM8 levels reflect inflammatory and bone-resorbing activities in the periodontal pocket.

Interplay between P. gingivalis, F. nucleatum and A. actinomycetemcomitans in murine alveolar bone loss, arthritis onset and progression

Increasing evidence supports the association of periodontitis with rheumatoid arthritis. Even though a prominent role has been postulated for Porphyromonas gingivalis, many bacterial species contribute to the pathogenesis of periodontal disease. We therefore investigated the impact of Porphyromonas gingivalis as well as other major pathobionts on the development of both, periodontitis and arthritis in the mouse. Pathobionts used - either alone or in combination - were Porphyromonas gingivalis, Fusobacterium nucleatum and Aggregatibacter actinomycetemcomintans. Periodontitis was induced via oral gavage in SKG, DBA/1 and F1 (DBA/1 × B10.Q) mice and collagen-induced arthritis was provoked via immunization and boost with bovine collagen type II. Alveolar bone loss was quantified via micro computed tomography, arthritis was evaluated macroscopically and histologically and serum antibodies were assessed. Among the strains tested, only F1 mice were susceptible to P. gingivalis induced periodontitis and showed significant alveolar bone loss. Bone loss was paralleled by antibody titers against P. gingivalis. Of note, mice inoculated with the mix of all three pathobionts showed less alveolar bone loss than mice inoculated with P. gingivalis alone. However, oral inoculation with either F. nucleatum or A. actinomycetemcomintans alone accelerated subsequent arthritis onset and progression. This is the first report of a triple oral inoculation of pathobionts combined with collagen-induced arthritis in the mouse. In this interplay and this particular genetic setting, F. nucleatum and A. actinomycetemcomitans exerted a protective impact on P. gingivalis induced alveolar bone loss. By themselves they did not induce periodontitis yet accelerated arthritis onset and progression.

An observation on the severity of periodontal disease in past cigarette smokers suffering from rheumatoid arthritis- evidence for a long-term effect of cigarette smoke exposure?

Background

Rheumatoid arthritis (RA) and cigarette smoking are both risk factors for periodontal disease (PD). Previous research suggests that systemic inflammatory conditions and cigarette smoking may act in synergy, and their co-occurrence leads to a much higher risk of developing severe stage PD than what the combination of their individual risks would suggest. We originally sought to test this in the case of RA, but it turned out that the majority of our patients were former smokers, who smoked for prolonged periods in the past. For that reason, we decided to shift our focus toward the possible effects of past chronic cigarette smoke exposure.

Methods

The data of 73 RA patients and 77 healthy controls were analyzed. The participants received a full-mouth periodontal examination to determine their periodontal status. Rheumatological indices and data on past tobacco use were also recorded. Both the patient and the control groups were divided into former smoker and non-smoker subgroups for the analyses. Non-smoker controls were used as the reference group.

Results

In the control group, smoking in history increased the odds of developing both the moderate and the severe stages of PD, but the change was not statistically significant. RA significantly, increased the odds of developing both stages in itself, but the highest odds were seen in the former smoker RA group.

Conclusion

Based on this surprising observation of ours, we hypothesize that chronic cigarette smoke might bring about permanent changes in the periodontal tissues, leading to their hypersensitivity to inflammatory challenges.

Chronic biofilm-based infections: skewing of the immune response

Many of the deadliest bacterial diseases that plague humanity in the modern age are caused by bacterial biofilms that produce chronic infections. However, most of our knowledge of the host immune response comes from the study of planktonic pathogens. While there are similarities in the host response to planktonic and biofilm bacteria, specific immune responses toward biofilms have not been well studied; the only apparent difference is the inability to clear the bacteria allowing the biofilm infection to become chronic. In some cases, the biofilms skew T-cell response toward a balance that allows a stalemate between the host and the pathogen, in which the infection can become persistent. In this minireview, we will summarize well-known examples of this phenomena as well as some emerging studies that may indicate that this situation is much more common than initially thought.

Insights into the Evolution of Host Association through the Isolation and Characterization of a Novel Human Periodontal Pathobiont, Desulfobulbus oralis

The human oral microbiota encompasses representatives of many bacterial lineages that have not yet been cultured. Here we describe the isolation and characterization of previously uncultured Desulfobulbus oralis, the first human-associated representative of its genus. As mammalian-associated microbes rarely have free-living close relatives, D. oralis provides opportunities to study how bacteria adapt and evolve within a host. This sulfate-reducing deltaproteobacterium has adapted to the human oral subgingival niche by curtailing its physiological repertoire, losing some biosynthetic abilities and metabolic independence, and by dramatically reducing environmental sensing and signaling capabilities. The genes that enable free-living Desulfobulbus to synthesize the potent neurotoxin methylmercury were also lost by D. oralis, a notably positive outcome of host association. However, horizontal gene acquisitions from other members of the microbiota provided novel mechanisms of interaction with the human host, including toxins like leukotoxin and hemolysins. Proteomic and transcriptomic analysis revealed that most of those factors are actively expressed, including in the subgingival environment, and some are secreted. Similar to other known oral pathobionts, D. oralis can trigger a proinflammatory response in oral epithelial cells, suggesting a direct role in the development of periodontal disease.

Animal-associated microbiota likely assembled as a result of numerous independent colonization events by free-living microbes followed by coevolution with their host and other microbes. Through specific adaptation to various body sites and physiological niches, microbes have a wide range of contributions, from beneficial to disease causing. Desulfobulbus oralis provides insights into genomic and physiological transformations associated with transition from an open environment to a host-dependent lifestyle and the emergence of pathogenicity. Through a multifaceted mechanism triggering a proinflammatory response, D. oralis is a novel periodontal pathobiont. Even though culture-independent approaches can provide insights into the potential role of the human microbiome “dark matter,” cultivation and experimental characterization remain important to studying the roles of individual organisms in health and disease.

Oral Biofilms from Symbiotic to Pathogenic Interactions and Associated Disease -Connection of Periodontitis and Rheumatic Arthritis by Peptidylarginine Deiminase

A wide range of bacterial species are harbored in the oral cavity, with the resulting complex network of interactions between the microbiome and host contributing to physiological as well as pathological conditions at both local and systemic levels. Bacterial communities inhabit the oral cavity as primary niches in a symbiotic manner and form dental biofilm in a stepwise process. However, excessive formation of biofilm in combination with a corresponding deregulated immune response leads to intra-oral diseases, such as dental caries, gingivitis, and periodontitis. Moreover, oral commensal bacteria, which are classified as so-called “pathobionts” according to a now widely accepted terminology, were recently shown to be present in extra-oral lesions with distinct bacterial species found to be involved in the onset of various pathophysiological conditions, including cancer, atherosclerosis, chronic infective endocarditis, and rheumatoid arthritis. The present review focuses on oral pathobionts as commensal and healthy members of oral biofilms that can turn into initiators of disease. We will shed light on the processes involved in dental biofilm formation and also provide an overview of the interactions of P. gingivalis, as one of the most prominent oral pathobionts, with host cells, including epithelial cells, phagocytes, and dental stem cells present in dental tissues. Notably, a previously unknown interaction of P. gingivalis bacteria with human stem cells that has impact on human immune response is discussed. In addition to this very specific interaction, the present review summarizes current knowledge regarding the immunomodulatory effect of P. gingivalis and other oral pathobionts, members of the oral microbiome, that pave the way for systemic and chronic diseases, thereby showing a link between periodontitis and rheumatoid arthritis.

The innate host response in caries and periodontitis

INTRODUCTION

Innate immunity rapidly defends the host against infectious insults. These reactions are of limited specificity and exhaust without providing long-term protection. Functional fluids and effector molecules contribute to the defence against infectious agents, drive the immune response, and direct the cellular players.

AIM

To review the literature and present a summary of current knowledge about the function of tissues, cellular players and soluble mediators of innate immunity relevant to caries and periodontitis.

METHODS

Historical and recent literature was critically reviewed based on publications in peer-reviewed scientific journals.

RESULTS

The innate immune response is vital to resistance against caries and periodontitis and rapidly attempts to protect against infectious agents in the dental hard and soft tissues. Soluble mediators include specialized proteins and lipids. They function to signal to immune and inflammatory cells, provide antimicrobial resistance, and also induce mechanisms for potential repair of damaged tissues.

CONCLUSIONS

Far less investigated than adaptive immunity, innate immune responses are an emerging scientific and therapeutic frontier. Soluble mediators of the innate response provide a network of signals to organize the near immediate molecular and cellular response to infection, including direct and immediate antimicrobial activity. Further studies in human disease and animal models are generally needed.

IL-35 may maintain homeostasis of the immune microenvironment in periodontitis

T lymphocyte cells, including regulatory T (Treg) and T helper 17 cells, have important roles in the human periodontium. However, the basis for Treg cytokine expression in various compartments of the periodontium remains unclear. The aim of the present study was to investigate the expression of interleukin (IL)-35 in the peripheral blood mononuclear cells (PBMCs) and periodontal tissues of patients with chronic periodontitis (CP), with a view to understanding its role in this disease, and ultimately providing improved treatments. Peripheral blood, periodontal tissues and gingival crevicular fluids (GCFs) were collected from patients with CP or impacted teeth, the latter serving as healthy controls. The expression levels of IL-35 subunit mRNAs in PBMCs and periodontal tissues were determined using reverse transcription-quantitative polymerase chain reaction, while the IL-35 protein expression in GCFs and sera was quantified by ELISA. The relative expression of IL-35 subunit mRNAs in the affected tissues of patients with CP was significantly higher compared with that in samples from healthy controls (P<0.05). The mean concentration of IL-35 protein in the GCFs and sera of patients with periodontitis was also significantly higher compared with that in samples from healthy controls (P<0.001). IL-35 protein and periodontal clinical indicators were negatively correlated. It was hypothesized that the increased level of IL-35 plays a protective role in periodontal disease by maintaining immune system homeostasis and dampening the inflammatory response, and highlights IL-35 as a potential new therapy for the treatment of periodontitis.

Quantitative Parameters of Interdental Gingiva in Chronic Periodontitis Patients with IFN-γ Gene Polymorphism

Chronic periodontitis (CP), an infectious disease resulting in inflammation within the periodontal tissue, is the main cause of adult tooth loss. CP is a multi-factorial disorder and the interaction between multiple genetic and environmental factors results in the manifestation of this disease. Recent researches in periodontitis has focused on cytokine gene polymorphisms that play important role in periodontal inflammation, but few studies investigated histological change that occur during CP in the supporting tissue of teeth. The aims of this study were to investigate the association of IFN-γ +874 A/T polymorphisms and quantitative parameters of interdental gingiva in CP patients. The study samples were interdental gingiva biopsies from 60 individuals including 38 patients and 22 healthy subjects. After determination of IFN-γ +874 A/T gene polymorphism by amplification refractory mutation system-polymerase chain reaction (ARMS-PCR), patients were divided in three subgroups: 10 AA, 18 AT and 10 TT. After slides preparation, quantitative parameters were estimated by Cavalieri's point-counting method. Statistical analyses were performed using Mann-Whitney and Kruskal-Wallis test to compare differences between groups. The volume density (Vv) of epithelium, connective tissue and its components were significantly different between the control and CP groups (P&lt;0.05). Statistically significant differences in the Vv of collagenous and non-collagenous matrix of interdental gingiva between AA, AT and TT groups were found (P&lt;0.05). Result of present study shows that IFN-γ +874 A/T is strongly associated with some quantitative parameters of connective tissue constituents of interdental papilla in CP patients.

Effect of 1.2% of simvastatin gel as a local drug delivery system on Gingival Crevicular Fluid interleukin-6 & interleukin-8 levels in non surgical treatment of chronic periodontitis patients

AIM

The present study was carried out to evaluate the effect of 1.2% simvastatin gel as local drug delivery (LDD) system on Gingival Crevicular Fluid (GCF) Interleukin -6 (IL-6) and Interleukin-8 (IL-8) levels in chronic periodontitis patients, in addition to scaling and root planing (SRP).

METHODS

A total of 46 chronic periodontitis patients were equally divided into two groups. Group I patients were treated by SRP; Group II patients were treated by SRP followed by LDD of 1.2% simvastatin (SMV) gel. Plaque index (PI), Gingival index(GI), Sulcus Bleeding Index (SBI), Probing pocket depth (PPD) and Relative clinical attachment level (CAL) were recorded & GCF samples were collected at baseline (0day) and at 45th day from both the groups. The collected GCF samples were analysed for IL-6 and IL-8 levels with enzyme-linked immunosorbent assay (ELISA).

RESULTS

Both the groups showed significant reduction in all the clinical parameters scores and IL-6 and IL-8 levels after non-surgical periodontal therapy (SRP for group I/SRP+1.2% SMV gel for group II) in contrast to baseline values. However, a greater reduction was observed in group II. A non-significant positive correlation was observed between clinical parameters and IL-6 and IL-8 levels except at baseline, a significant correlation was observed between PPD &IL 6 levels in group II.

CONCLUSIONS

In adjunct to SRP, 1.2% Simvastatin gel acts as an effective local drug delivery agent for the management of chronic periodontitis.

Periodontal disease and FAM20A mutations

Enamel-renal-gingival syndrome (ERGS; OMIM #204690), a rare autosomal recessive disorder caused by mutations in FAM20A, is characterized by nephrocalcinosis, nephrolithiasis, amelogenesis imperfecta, hypoplastic type, gingival fibromatosis and other dental abnormalities, including hypodontia and unerupted teeth with large dental follicles. We report three patients and their families with findings suggestive of ERGS. Mutation analysis of FAM20A was performed in all patients and their family members. Patients with homozygous frameshift and compound heterozygous mutations in FAM20A had typical clinical findings along with periodontitis. The other had a novel homozygous missense mutation in exon 10, mild gingival fibromatosis and renal calcifications. The periodontitis in our patients may be a syndrome component, and similar findings in previous reports suggest more than coincidence. Fam20a is an allosteric activator that increases Fam20c kinase activity. It is hypothesized that lack of FAM20A activation of FAM20C in our patients with FAM20A mutations might have caused amelogenesis imperfecta, abnormal bone remodeling and periodontitis. Nephrocalcinosis appears not to be a consistent finding of the syndrome and the missense mutation may correlate with mild gingival fibromatosis. Here we report three patients with homozygous or compound heterozygous mutations in FAM20A and findings that extend the phenotypic spectrum of this disorder, showing that protein truncation is associated with greater clinical severity.

Role of Porphyromonas gingivalis HmuY in Immunopathogenesis of Chronic Periodontitis

Periodontitis is a multifactorial disease, with participation of bacterial, environmental, and host factors. It results from synergistic and dysbiotic multispecies microorganisms, critical "keystone pathogens," affecting the whole bacterial community. The purpose of this study was to review the role of Porphyromonas gingivalis in the immunopathogenesis of chronic periodontitis, with special attention paid to HmuY. The host response during periodontitis involves the innate and adaptive immune system, leading to chronic inflammation and progressive destruction of tooth-supporting tissues. In this proinflammatory process, the ability of P. gingivalis to evade the host immune response and access nutrients in the microenvironment is directly related to its survival, proliferation, and infection. Furthermore, heme is an essential nutrient for development of these bacteria, and HmuY is responsible for its capture from host heme-binding proteins. The inflammatory potential of P. gingivalis HmuY has been shown, including induction of high levels of proinflammatory cytokines and CCL2, decreased levels of IL-8, and increased levels of anti-HmuY IgG and IgG1 antibodies in individuals with chronic periodontitis. Therefore, the HmuY protein might be a promising target for therapeutic strategies and for development of diagnostic methods in chronic periodontitis, especially in the case of patients with chronic periodontitis not responding to treatment, monitoring, and maintenance therapy.

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

Background. A loss of mucosal tolerance to the resident microbiome has been postulated in the aetiopathogenesis of spondyloarthritis, thus the purpose of these studies was to investigate microbial communities that colonise the oral cavity of patients with axial spondyloarthritis (AxSpA) and to compare these with microbial profiles of a matched healthy population.

Methods. Thirty-nine participants, 17 patients with AxSpA and 22 age and gender-matched disease-free controls were recruited to the study. For patients with AxSpA, disease activity was assessed using the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI). All participants underwent a detailed dental examination to assess oral health, including the presence of periodontal disease assessed using probing pocket depth (PPD). Plaque samples were obtained and their bacterial populations were profiled using Ion Torrent sequencing of the V6 region of the 16S rRNA gene.

Results.Patients with AxSpA had active disease (BASDAI 4.1 ± 2.1 [mean ± SD]), and a significantly greater prevalence of periodontitis (PPD ≥ 4 mm at ≥4 sites) than controls. Bacterial communities did not differ between the two groups with multiple metrics of α and β diversity considered. Analysis of operational taxonomic units (OTUs) and higher levels of taxonomic assignment did not provide strong evidence of any single taxa associated with AxSpA in the subgingival plaque.

Discussion. Although 16S rRNA gene sequencing did not identify specific bacterial profiles associated with AxSpA, there remains the potential for the microbiota to exert functional and metabolic influences in the oral cavity which could be involved in the pathogenesis of AxSpA.

No association between periodontitis, preterm birth, or intrauterine growth restriction: experimental study in Wistar rats

BACKGROUND

The biologic plausibility of the possible association between periodontitis and adverse pregnancy outcomes has been assessed with the use of different experimental models. However, most experimental studies did not induce periodontitis in the animals but promoted an acute microbial challenge with selected periodontal pathogens or their products subcutaneous or intravenous or intraamniotic. The present study was then conducted to verify the biologic plausibility of such association by experimentally inducing periodontitis in Wistar rats.

OBJECTIVE

An experimental study on an animal model by the induction of periodontitis in 50% of sites and assessment of the presence of cytokines in the gingival tissue, serum, placenta, cord, and amniotic fluid was designed to test the null hypothesis that experimental periodontitis that is induced on rats does not result in adverse pregnancy outcomes.

STUDY DESIGN

Forty female Wistar rats were included in 2 groups: a periodontally healthy (without ligatures) and an experimentally induced periodontitis group (test, with ligatures). Forty-five days after the induction, the mating was initiated. Males were placed with females in the ratio of 1:2 for a period of 12 hours. The bodyweight of the female, from then on, was recorded daily. When the pregnancy was confirmed on day 20, laparotomy was performed. The amniotic fluid, placenta, umbilical cord, blood (serum) and maternal and gingival tissue samples were subjected to quantitative analysis for interleukin 1α, -6, -10, -4, -12p70, and -17a, tumor necrosis factor-α, and interferon-γ by multiplex methods. Mean scores, standard deviations, and standard errors for estimated measures were calculated. For cytokines analyses, the Mann-Whitney test was conducted to compare the concentration of the analytes from control and test groups in the different tissues samples. For comparison of cytokines reduction from gingival tissue to serum and from serum to placenta, the Wilcoxon Test was performed. Spearman's correlation was conducted among cytokines in the 5 different tissues that were evaluated.

RESULTS

The induced periodontitis in Wistar rats did not result in adverse outcomes of pregnancy. There were no statistically significant differences between groups in relation to prematurity, fetal, or birth weight. Regarding cytokines, there were no statistically significant differences in concentrations that were measured in each tissue between the groups with periodontitis and controls. Furthermore, all cytokine levels in the placenta, except interleukin-6, were diminished compared with the amniotic fluid or maternal serum, which suggested that the cytokines cannot easily be transferred via this tissue in maternal-fetal or fetomaternal direction. The fertility rate was reduced significantly in the group with periodontitis.

CONCLUSION

Periodontitis that is induced in rats is not a risk factor for preterm birth or low birthweight.

Human Periodontal Stem Cells Release Specialized Proresolving Mediators and Carry Immunomodulatory and Prohealing Properties Regulated by Lipoxins

The actions of human periodontal ligament stem cells (hPDLSCs) on polymorphonuclear neutrophil (PMN) apoptosis and antimicrobial functions, and the impact of lipoxin A₄ (LXA₄) on hPDLSCs were investigated. hPDLSCs significantly reduced apoptosis and stimulated microbicidal activity of human PMNs, via both cell-cell interactions and paracrine mechanisms. hPDLSCs also were found to biosynthesize proresolving lipid mediators and prostaglandins. This study also demonstrated that the LXA₄-ALX/FPR2 axis regulates regenerative functions of hPDLSCs by a novel receptor-mediated mechanism.

Unresolved inflammation and tissue destruction are underlying mechanisms of periodontitis, which is linked to dysregulated polymorphonuclear neutrophil (PMN) functions. Lipoxin A₄ (LXA₄) is a specialized proresolving lipid mediator (SPM) that dampens excessive inflammation, promotes resolution, and protects from leukocyte-mediated tissue damage. Human periodontal ligament stem cells (hPDLSCs) represent key players during tissue regeneration and may contribute to resolution of inflammation; thus, they may represent a promising tool in regenerative dentistry. In the present study, we investigated the actions of hPDLSCs on PMN apoptosis and antimicrobial functions, and determined the impact of LXA₄ on hPDLSCs. hPDLSCs significantly reduced apoptosis and stimulated microbicidal activity of human PMNs, via both cell-cell interactions and paracrine mechanisms. Lipid mediator metabololipidomics analysis demonstrated that hPDLSCs biosynthesize SPMs, including resolvin D1, D2, D5, and D6; protectin D1; maresins; and LXB₄; as well as prostaglandins D₂, E₂, and F_2α. LXA₄ significantly enhanced proliferation, migration, and wound healing capacity of hPDLSCs through the activation of its cognate receptor ALX/FPR2, expressed on hPDLSCs. Together, these results demonstrate that hPDLSCs modulate PMN functions, and provide the first evidence that stem cells generate SPM and that the LXA₄-ALX/FPR2 axis regulates regenerative functions of hPDLSCs by a novel receptor-mediated mechanism.

Significance

These findings uncovered unappreciated features of stem cells from the periodontal ligament, supporting the notion that these cells may act as master regulators of pathophysiological events through the release of mediators that promote the resolution of inflammation and bacterial killing. The study also demonstrated that it is possible to modulate important functions of periodontal stem cells using lipoxin A₄, a potent endogenous stop signal of inflammation. Thus, this study revealed an unappreciated anti-inflammatory proregenerative circuit that may be exploited to combat periodontal pathologies using resident stem cells. Moreover, the data may represent a more general template to explain the immunomodulatory functions of stem cells.

Proteomic profiling of host-biofilm interactions in an oral infection model resembling the periodontal pocket

Periodontal infections cause inflammatory destruction of the tooth supporting tissues. We recently developed a dynamic, in vitro periodontal organotypic tissue model in a perfusion bioreactor system, in co-culture with an 11-species subgingival biofilm, which may recapitulate early events during the establishment of periodontal infections. This study aimed to characterize the global proteome regulations in this host-biofilm interaction model. Semi-quantitative shotgun proteomics were applied for protein identification and quantification in the co-culture supernatants (human and bacterial) and the biofilm lysates (bacterial). A total of 896 and 3363 proteins were identified as secreted in the supernatant and expressed in the biofilm lysate, respectively. Enriched gene ontology analysis revealed that the regulated secreted human tissue proteins were related to processes of cytoskeletal rearrangement, stress responses, apoptosis, and antigen presentation, all of which are commensurate with deregulated host responses. Most secreted bacterial biofilm proteins derived from their cytoplasmic domain. In the presence of the tissue, the levels of Fusobacterium nucleatum, Actinomyces oris and Campylobacter rectus proteins were significantly regulated. The functions of the up-regulated intracellular (biofilm lysate) proteins were associated with cytokinesis. In conclusion, the proteomic overview of regulated pathways in this host-biofilm interaction model provides insights to the early events of periodontal pathogenesis.