Host-bacteria crosstalk at the dentogingival junction

Levels of matrix metalloproteinase-1 (MMP-1), MMP-2, MMP-3, osteopontin, pentraxin-3, and thymic stromal lymphopoietin in crevicular fluid samples from peri-implantitis, periodontitis, and healthy sites

AIM

Periodontitis and peri-implantitis are chronic inflammatory diseases characterized by the destruction of supporting tissues. Despite some similarities, it is essential to understand the differences in how these diseases elicit unique host responses within the oral tissues, including the production of selected matrix metalloproteinases (MMPs) and inflammatory mediators involved in tissue remodelling. The aim of this study was to evaluate the levels of proteolytic enzymes MMP-1, MMP-2, MMP-3, as well as the inflammatory mediators osteopontin (OPN), pentraxin-3 (PTX3), and thymic stromal lymphopoietin (TSLP) in crevicular fluid samples collected from healthy, periodontitis-affected, and peri-implantitis sites.

METHODS

Gingival crevicular fluid (GCF) and peri-implant crevicular fluid (PICF) samples were collected from healthy and diseased teeth and implant sites of 163 patients. The MMP-1, MMP-2, MMP-3, OPN, PTX3, and TSLP levels were determined using commercially available immunoassays. A linear mixed model procedure was adopted for multilevel analyses, using biomarker levels as the outcome variable to compare two types of sites. The diagnostic accuracy of the biomarkers was evaluated by Youden's index to estimate the sensitivity, specificity and the area under curve (AUC).

RESULTS

The levels of MMP-1, MMP-2, MMP-3, OPN, and TSLP were higher at sites with periodontitis and peri-implantitis compared to the levels at sites with healthy teeth and healthy implants. No significant differences were observed in the levels of the measured markers between the sites diagnosed with periodontitis and those diagnosed with peri-implantitis. The highest diagnostic potential at implant sites was found for MMP-2 (AUC = 0.74) and TSLP (AUC = 0.72). The highest AUC (0.82) at tooth sites was found for OPN.

CONCLUSIONS

The findings indicate that the proteolytic enzyme MMP-2 and the cytokine TSLP might be potential biomarkers for both periodontitis and peri-implantitis, whereas the proinflammatory cytokine OPN may serve as a biomarker for periodontitis. Further studies are required to confirm the utility of these biomarkers and explore their potential clinical applications.

Composition of subgingival microbiota associated with periodontitis and diagnosis of malignancy-a cross-sectional study

Periodontitis is one of the world's most prevalent infectious conditions, affecting between 25 and 40% of the adult population. It is a consequence of the complex interactions between periodontal pathogens and their products, which trigger the host inflammatory response, chronic inflammation, and tissue destruction. Chronic systemic low-grade inflammation is involved in numerous diseases, and it is also known that long-lasting inflammation and chronic infections predispose one to cancer. Here, we characterized and compared the subgingival microbiota associated with periodontitis and diagnosis of malignancy in a longitudinal 10-year follow-up study. The study was conducted on 50 patients with periodontitis and 40 periodontally healthy individuals. The recorded clinical oral health parameters were periodontal attachment loss (AL), bleeding on probing (BOP), gingival index (GI), probing depth (PD), and plaque index (PI). Subgingival plaque was collected from each participant, from which DNA was extracted, and 16S rRNA gene amplicon sequencing performed. Cancer diagnoses data were collected between the years 2008-2018 from the Swedish Cancer Registry. The participants were categorized based on having cancer at the time of sample collection (CSC), having developed cancer later (DCL), and controls without any cancer. The most abundant phyla across all 90 samples were Actinobacteria, Proteobacteria, Firmicutes, Bacteroidetes, and Fusobacteria. At the genus level, Treponema, Fretibacterium, and Prevotella were significantly more abundant in samples of periodontitis patients compared to non-periodontitis individuals. With regard to samples of cancer patients, Corynebacterium and Streptococcus were more abundant in the CSC group; Prevotella were more abundant in the DCL group; and Rothia, Neisseria, and Capnocytophaga were more abundant in the control group. In the CSC group, we also found that the presence of periodontal inflammation, in terms of BOP, GI, and PLI, significantly correlated with species belonging to the genera Prevotella, Treponema, and Mycoplasma. Our results revealed that several subgingival genera were differentially enriched among the studied groups. These findings underscore the need for further research to fully understand the role that oral pathogens may play in the development of cancer.

An SCPPPQ1/LAM332 protein complex enhances the adhesion and migration of oral epithelial cells: Implications for dentogingival regeneration

Common periodontal disease treatment procedures often fail to restore the structural integrity of the junctional epithelium (JE), the epithelial attachment of the gum to the tooth, leaving the tooth-gum interface prone to bacterial colonization. To address this issue, we introduced a novel bio-inspired protein complex comprised of a proline-rich enamel protein, SCPPPQ1, and laminin 332 (LAM332) to enhance the JE attachment. Using quartz crystal microbalance with dissipation monitoring (QCM-D), we showed that SCPPPQ1 and LAM332 interacted and assembled into a protein complex with high-affinity adsorption of 5.9e^-8 [M] for hydroxyapatite (HA), the main component of the mineralized tooth surfaces. We then designed a unique shear device to study the adhesion strength of the oral epithelial cells to HA. The SCPPPQ1/LAM332 complex resulted in a twofold enhancement in adhesion strength of the cells to HA compared to LAM332 (from 31 dyn/cm² to 63 dyn/cm²). In addition, using a modified wound-healing assay, we showed that gingival epithelial cells demonstrated a significantly high migration rate of 2.7 ± 0.24 µm/min over SCPPPQ1/LAM332-coated surfaces. Our collective data show that this protein complex has the potential to be further developed in designing a bioadhesive to enhance the JE attachment and protect the underlying connective tissue from bacterial invasion. However, its efficacy for wound healing requires further testing in vivo. STATEMENT OF SIGNIFICANCE: This work is the first functional study towards understanding the combined role of the enamel protein SCPPPQ1 and laminin 332 (LAM332) in the epithelial attachment of the gum, the junctional epithelium (JE), to the tooth hydroxyapatite surfaces. Such studies are essential for developing therapeutic approaches to restore the integrity of the JE in the destructive form of gum infection. We have developed a model system that provided the first evidence of the strong interaction between SCPPPQ1 and LAM332 on hydroxyapatite surfaces that favored protein adsorption and subsequently oral epithelial cell attachment and migration. Our collective data strongly suggested using the SCPPPQ1/LAM332 complex to accelerate the reestablishment of the JE after surgical gum removal to facilitate gum regeneration.

Salivary Microbiota and Host-Inflammatory Responses in Periodontitis Affected Individuals With and Without Rheumatoid Arthritis

Objectives

Periodontitis and rheumatoid arthritis (RA) are two widespread chronic inflammatory diseases with a previously suggested association. The objective of the current study was to compare the oral microbial composition and host´s inflammatory mediator profile of saliva samples obtained from subjects with periodontitis, with and without RA, as well as to predict biomarkers, of bacterial pathogens and/or inflammatory mediators, for classification of samples associated with periodontitis and RA.

Methods

Salivary samples were obtained from 53 patients with periodontitis and RA and 48 non-RA with chronic periodontitis. The microbial composition was identified using 16S rRNA gene sequencing and compared across periodontitis patients with and without RA. Levels of inflammatory mediators were determined using a multiplex bead assay, compared between the groups and correlated to the microbial profile. The achieved data was analysed using PCoA, DESeq2 and two machine learning algorithms, OPLS-DA and sPLS-DA.

Results

Differential abundance DESeq2 analyses showed that the four most highly enriched (log2 FC >20) amplicon sequence variants (ASVs) in the non-RA periodontitis group included Alloprevotella sp., Prevotella sp., Haemophilus sp., and Actinomyces sp. whereas Granulicatella sp., Veillonella sp., Megasphaera sp., and Fusobacterium nucleatum were the most highly enriched ASVs (log2 FC >20) in the RA group. OPLS-DA with log2 FC analyses demonstrated that the top ASVs with the highest importance included Vampirovibrio sp. having a positive correlation with non-RA group, and seven ASVs belonging to Sphingomonas insulae, Sphingobium sp., Novosphingobium aromaticivorans, Delftia acidovorans, Aquabacterium spp. and Sphingomonas echinoides with a positive correlation with RA group. Among the detected inflammatory mediators in saliva samples, TWEAK/TNFSF12, IL-35, IFN-α2, pentraxin-3, gp130/sIL6Rb, sIL-6Ra, IL-19 and sTNF-R1 were found to be significantly increased in patients with periodontitis and RA compared to non-RA group with periodontitis. Moreover, correlations between ASVs and inflammatory mediators using sPLS-DA analysis revealed that TWEAK/TNFSF12, pentraxin-3 and IL-19 were positively correlated with the ASVs Sphingobium sp., Acidovorax delafieldii, Novosphingobium sp., and Aquabacterium sp.

Conclusion

Our results suggest that the combination of microbes and host inflammatory mediators could be more efficient to be used as a predictable biomarker associated with periodontitis and RA, as compared to microbes and inflammatory mediators alone.

Impact of calorie restriction and intermittent fasting on periodontal health

The scientific evidence indicates that calorie restriction and intermittent fasting are among the appropriate strategies targeting factual causative factors of various inflammatory and lifestyle-related disorders. Periodontitis is a common oral inflammatory disease leading to bone loss that is associated with various systemic problems. Previous studies suggest that calorie restriction may dampen inflammation and concomitant tissue damage under inflammatory conditions, such as periodontal diseases in nonhuman primates. However, insufficient research has been carried out to assess the effects of a calorie-restricted diet on the initiation and progression of periodontal disease in humans. This review of the literature aims to describe the general concepts of calorie restriction, its clinical implications, and related therapeutic potential in controlling periodontal inflammation. The review shows that fasting regimen groups have shown lesser bone loss because of an increase in osteoprogenitor cells than non-fasting groups. Calorie restriction dampens the inflammatory response and reduces circulating inflammatory mediators like tumor necrosis factor-alpha, interleukin-6, matrix metalloproteinase-8, matrix metalloproteinase-9, and interleukin-1-beta in gingival crevicular fluid. However, the incorporation of this form of dietary intervention continues to be challenging in our current society, in which obesity is a major public concern. Calorie restriction and intermittent fasting can play a key role in the cost-effective resolution of periodontal inflammation as a primary prevention strategy for the management of chronic inflammatory diseases, including periodontal diseases.

Maintaining a protective state for human periodontal tissue

Periodontitis, caused by infection with periodontal pathogens, is primarily characterized by inflammatory bone resorption and destruction of connective tissue. Simply describing periodontitis as a specific bacterial infection cannot completely explain the various periodontal tissue destruction patterns observed. Periodontal tissue damage is thought to be caused by various factors. In recent years, research goals for periodontal pathogens have shifted from searching for specific pathogens to investigating mechanisms that damage periodontal tissues. Bacteria interact directly with the host in several ways, influencing expression and activity of molecules that evade host defenses, and destroying local tissues and inhibiting their repair. The host's innate and acquired immune systems are important defense mechanisms that protect periodontal tissues from attack and invasion of periodontal pathogens, thus preventing infection. Innate and acquired immunity have evolved to confront the microbial challenge, forming a seamless defense network in periodontal tissues. In the innate immune response, host cells quickly detect, via specialized receptors, macromolecules and nucleic acids present on bacterial cell walls, and this triggers a protective, inflammatory response. The work of this subsystem of host immunity is performed mainly by phagocytes, beta-defensin, and the complement system. In addition, the first line of defense in oral innate immunity is the junctional epithelium, which acts as a physical barrier to the entry of oral bacteria and other nonself substances. In the presence of a normal flora, junctional epithelial cells differentiate actively and proliferate apically, with concomitant increase in chemotactic factor expression recruiting neutrophils. These immune cells play an important role in maintaining homeostasis and the protective state in periodontal tissue because they eliminate unwanted bacteria over time. Previous studies indicate a mechanism for attracting immune cells to periodontal tissue with the purpose of maintaining a protective state; although this mechanism can function without bacteria, it is enhanced by the normal flora. A better understanding of the relationship between the protective state and its disruption in periodontal disease could lead to the development of new treatment strategies for periodontal disease.

Neutrophils defending the defenders

Neutrophils are the most abundant granulocytes which are involved in defense mechanism. As innate immune cells, they are first-line defenders and can perform different functions in the human body to maintain equilibrium. Neutrophils are the main leukocyte and their role in healthy oral cavity is to face pathological changes within oral environment. With regard to these, it has been observed that neutrophils are highly heterogeneous in their behavior. The aim of this review is to give an overview of the role of neutrophils in context of various physiological and pathological conditions.

Oral inflammatory load: Neutrophils as oral health biomarkers

Periodontal diseases present a significant challenge to our healthcare system in terms of morbidity from the disease itself as well as their putative and deleterious effects on systemic health. The current method of diagnosing periodontal disease utilizes clinical criteria solely. These are imprecise and are somewhat invasive. There is thus significant benefit to creating a non-invasive test as a method of screening for and monitoring of periodontal diseases, and, in particular, chronic periodontitis. Oral polymorphonuclear neutrophil (oPMN) counts have been found to correlate with extent of oral inflammation and the presence and severity of periodontal diseases. Potentially then, quantification of oPMNs might be used to identify and measure the severity of oral inflammation (oral inflammatory load; OIL) in subjects with healthy and inflamed periodontal tissues, demonstrating a positive correlation between higher oPMN counts and the extent/severity of OIL. These findings support the development and utilization of a non-invasive chair-side test enabling rapid, accurate, and objective screening of OIL based on measurement of oPMN numbers (similar to white blood cell levels in blood as used in medicine for assessment of infection). The use of such a test before, during, and after treatment of gingivitis and periodontitis could lead to improvements in timing of intervention (ie, when inflammation is active) thereby reducing long-term morbidity.

Commensal and pathogenic biofilms differently modulate peri-implant oral mucosa in an organotypic model

The impact of oral commensal and pathogenic bacteria on peri-implant mucosa is not well understood, despite the high prevalence of peri-implant infections. Hence, we investigated responses of the peri-implant mucosa to Streptococcus oralis or Aggregatibacter actinomycetemcomitans biofilms using a novel in vitro peri-implant mucosa-biofilm model. Our 3D model combined three components, organotypic oral mucosa, implant material, and oral biofilm, with structural assembly close to native situation. S. oralis induced a protective stress response in the peri-implant mucosa through upregulation of heat shock protein (HSP70) genes. Attenuated inflammatory response was indicated by reduced cytokine levels of interleukin-6 (IL-6), interleukin-8 (CXCL8), and monocyte chemoattractant protein-1 (CCL2). The inflammatory balance was preserved through increased levels of tumor necrosis factor-alpha (TNF-α). A. actinomycetemcomitans induced downregulation of genes important for cell survival and host inflammatory response. The reduced cytokine levels of chemokine ligand 1 (CXCL1), CXCL8, and CCL2 also indicated a diminished inflammatory response. The induced immune balance by S. oralis may support oral health, whereas the reduced inflammatory response to A. actinomycetemcomitans may provide colonisation advantage and facilitate later tissue invasion. The comprehensive characterisation of peri-implant mucosa-biofilm interactions using our 3D model can provide new knowledge to improve strategies for prevention and therapy of peri-implant disease.

Lactate Dehydrogenase and β-Glucuronidase as Salivary Biochemical Markers of Periodontitis Among Smokers and Non-Smokers

Objectives

This study aimed to establish lactate dehydrogenase (LDH) and β-glucuronidase as salivary biomarkers of periodontitis among smokers and non-smokers.

Methods

This cross-sectional case-control study was conducted at the Aligarh Muslim University, Aligarh, India, between January and June 2017. A total of 200 participants were divided into four groups based on their periodontal and smoking statuses. Unstimulated mixed saliva samples were collected to estimate LDH and β-glucuronidase levels. In addition, total protein was estimated using Lowry's method.

Results

There was a significant increase in enzyme activity in the periodontitis groups compared to the non-periodontitis groups (P <0.001). However, significantly lower enzyme activity was observed among smokers, irrespective of periodontal status (P <0.001). Nevertheless, a receiver operating characteristic curve analysis indicated the diagnostic potential of both enzymes to be fair-to-excellent.

Conclusion

Although smoking was found to significantly alter enzyme activity, LDH and β-glucuronidase were reliable salivary biomarkers of periodontitis among both smokers and non-smokers.

Porphyromonas gingivalis bypasses epithelial barrier and modulates fibroblastic inflammatory response in an in vitro 3D spheroid model

Porphyromonas gingivalis-induced inflammatory effects are mostly investigated in monolayer cultured cells. The aim of this study was to develop a 3D spheroid model of gingiva to take into account epithelio-fibroblastic interactions. Human gingival epithelial cells (ECs) and human oral fibroblasts (FBs) were cultured by hanging drop method to generate 3D microtissue (MT) whose structure was analyzed on histological sections and the cell-to-cell interactions were observed by scanning and transmission electron microscopy (SEM and TEM). MTs were infected by P. gingivalis and the impact on cell death (Apaf-1, caspase-3), inflammatory markers (TNF-α, IL-6, IL-8) and extracellular matrix components (Col-IV, E-cadherin, integrin β1) was evaluated by immunohistochemistry and RT-qPCR. Results were compared to those observed in situ in experimental periodontitis and in human gingival biopsies. MTs exhibited a well-defined spatial organization where ECs were organized in an external cellular multilayer, while, FBs constituted the core. The infection of MT demonstrated the ability of P. gingivalis to bypass the epithelial barrier in order to reach the fibroblastic core and induce disorganization of the spheroid structure. An increased cell death was observed in fibroblastic core. The development of such 3D model may be useful to define the role of EC–FB interactions on periodontal host-immune response and to assess the efficacy of new therapeutics.

Induction of IL-6 and IL-8 by activation of thermosensitive TRP channels in human PDL cells

OBJECTIVE

The oral cavity is often exposed to not only diverse external pathogens but also dramatic temperature changes. In this study, we investigated the effect of thermal stress on PDL cells with a focus on the inflammatory responses and bone homeostasis.

DESIGN

The PDL cells were isolated from healthy premolar extracted for orthodontic reasons, and examined using intracellular calcium concentration ([Ca(2+)]i) measurement and reverse transcription-polymerase chain reaction for pro-inflammatory cytokines and bone remodelling mediators.

RESULTS

We detected the expression of thermosensitive transient receptor potential (TRP) channels, such as TRPV1, TRPV2, TRPV3, TRPM8, and TRPA1. Functional activation of the channels by thermal stress and their specific agonists increased [Ca(2+)]i and interleukin (IL)-6 and IL-8 mRNA expression. A selective Ca(2+) chelator, BAPTA-AM, prevented TRP channel agonists-mediated IL-6 and IL-8 induction. Unlike pro-inflammatory cytokines, the expression of bone remodelling mediators, including receptor activator of nuclear factor-kappa B ligand and osteoprotegerin, was not altered by treatment with TRP channel agonists.

CONCLUSIONS

The activation of thermosensitive TRP channels induced IL-6 and IL-8 expression by increasing [Ca(2+)]i in human PDL cells. Therefore, thermal stress may play a critical role in the inflammatory responses of PDL cells.

The complement system and its role in the pathogenesis of periodontitis: current concepts

Periodontitis is a highly prevalent inflammatory disease in tooth supporting tissues, induced by bacteria growing in a biofilm on tooth surfaces. Components of the complement system are present in the periodontal tissue and the system is activated in periodontitis. Continuous complement activation and modulation by bacteria within the biofilm in periodontal pockets, however, may enhance local tissue destruction, providing the biofilm with both essential nutrients and space to grow. A more profound understanding of the mechanisms involved in complement-derived tissue degradation may facilitate the development of new treatment concepts for periodontitis. Further studies on the role of complement in periodontitis pathogenesis may also contribute to the understanding of why some individuals fail to resolve periodontitis. Here, we review evidence that links complement to the pathogenesis of periodontitis with an emphasis on interaction of complement with bacteria from periodontitis-associated biofilm.

Importance of Diversity in the Oral Microbiota including Candida Species Revealed by High-Throughput Technologies

Taking advantage of high-throughput technologies, deep sequencing of the human microbiome has revealed commensal bacteria independent of the ability to culture them. The composition of the commensal microbiome is dependent on bacterial diversity and the state of the host regulated by the immune system. Candida species are well known as components of the commensal oral microbiota. Candida species frequently colonize and develop biofilms on medical devices like dentures and catheters. Therefore, Candida biofilm on dentures leads to a decrease in the bacterial diversity and then to a change in the composition of the oral microbiota. A disturbance in the balance between commensal bacteria and the host immune system results in a switch from a healthy state to a diseased state even in the limited oral niche.

Transcription profiling reveals potential mechanisms of dysbiosis in the oral microbiome of rhesus macaques with chronic untreated SIV infection

A majority of individuals infected with human immunodeficiency virus (HIV) have inadequate access to antiretroviral therapy and ultimately develop debilitating oral infections that often correlate with disease progression. Due to the impracticalities of conducting host-microbe systems-based studies in HIV infected patients, we have evaluated the potential of simian immunodeficiency virus (SIV) infected rhesus macaques to serve as a non-human primate model for oral manifestations of HIV disease. We present the first description of the rhesus macaque oral microbiota and show that a mixture of human commensal bacteria and “macaque versions” of human commensals colonize the tongue dorsum and dental plaque. Our findings indicate that SIV infection results in chronic activation of antiviral and inflammatory responses in the tongue mucosa that may collectively lead to repression of epithelial development and impact the microbiome. In addition, we show that dysbiosis of the lingual microbiome in SIV infection is characterized by outgrowth of Gemella morbillorum that may result from impaired macrophage function. Finally, we provide evidence that the increased capacity of opportunistic pathogens (e.g. E. coli) to colonize the microbiome is associated with reduced production of antimicrobial peptides.