Genome-wide association study of biologically informed periodontal complex traits offers novel insights into the genetic basis of periodontal disease

New approaches to the control of chronic inflammatory diseases with a focus on the endolysosomal system of immune cells

Chronic inflammation is implicated in many types of diseases, including cardiovascular, neurodegenerative, metabolic, and immune disorders. The search for therapeutic targets to control chronic inflammation often involves narrowing down the various molecules associated with pathology that have been discovered by various omics analyses. Herein, a different approach to identify therapeutic targets against chronic inflammation is proposed and one such target is discussed as an example. In chronically inflamed tissues, a large number of cells receive diverse proinflammatory signals, the intracellular signals are intricately integrated, and complicated intercellular interactions are orchestrated. This review focuses on effectively blocking this chaotic inflammatory signaling network via the endolysosomal system, which acts as a cellular signaling hub. In endolysosomes, the inflammatory signals mediated by pathogen sensors, such as Toll-like receptors, and the signals from nutrient and metabolic pathways are integrally regulated. Disruption of endolysosome signaling results in a strong anti-inflammatory effect by disrupting various signaling pathways, including pathogen sensor-mediated signals, in multiple immune cells. The endolysosome-resident amino acid transporter, solute carrier family 15 member 4 (SLC15A4), which plays an important role in the regulation of endolysosome-mediated signals, is a promising therapeutic target for several inflammatory diseases, including autoimmune diseases. The mechanisms by which SLC15A4 regulates inflammatory responses may provide a proof of concept for the efficacy of therapeutic strategies targeting immune cell endolysosomes.

The Role of Interleukin-8 in the Estimation of Responsiveness to Steps 1 and 2 of Periodontal Therapy

OBJECTIVE

To investigate the association between interleukin-8 (IL-8) levels in gingival crevicular fluid (GCF) and total oral fluid (TOF) and the responsiveness to steps 1 and 2 of periodontal therapy.

MATERIALS AND METHODS

One-hundred and fifty-nine patients affected by periodontitis received steps 1 and 2 of periodontal therapy. At baseline, TOF and GCF samples were collected and analysed for IL-8 (Il-8TOF/IL-8GCF) using flow cytometry. Therapy outcomes were relative proportions of residual periodontal pockets (PPD%), pocket closure (PC) rates and pocket probing depth (PPD) reductions; these were associated with IL-8TOF/IL-8GCF.

RESULTS

High IL-8TOF was significantly associated with higher residual PPD% (p = 0.044) and lower PPD reduction compared to low IL-8TOF (high 0.79 ± 1.20 mm vs. low 1.20 ± 1.20 mm, p < 0.001) in non-smokers, while in smokers high IL-8GCF was related to lower PPD reduction (high 0.62 ± 1.22 mm vs. low 0.84 ± 1.12 mm, p = 0.009). Furthermore, high baseline IL-8TOF was significantly associated with poorer PC rates compared to medium and low concentrations in both non-smokers (high 41% vs. medium 55% vs. low 58%, p < 0.001) and smokers (high 34% vs. medium 44% vs. low 46%, p < 0.001).

CONCLUSION

High IL-8 concentrations at baseline had a significant impact on residual PPD%, PC rates and PPD reduction. The findings suggest that, especially in non-smokers, baseline IL-8 levels collected from the TOF could serve as a component in the estimation of responsiveness to steps 1 and 2 of periodontal therapy.

Multiple PDT sessions with chlorin-e6 and LL-37 loaded-nanoemulsion provide limited benefits to periodontitis in rats

BACKGROUND

The combination of photodynamic therapy (PDT) and LL-37 has never been tested in an animal study and our research team background suggests this strategy might be a promising alternative to intensify periodontitis resolution. This study aimed to assess the effects of multiple sessions of PDT with chlorin-e6 conjugated to the antimicrobial peptide LL-37 loaded nanoemulsion, as adjunctive therapy in experimental periodontitis in rats.

METHODS

Experimental periodontitis was induced in 81 rats. After disease establishment, animals were assigned to three groups: SRP (scaling and root planning); SRP + 1PDT, SRP followed by a single PDT session; SRP + 4PDT (n = 27), SRP followed by four PDT sessions at 0, 24, 48 and 72 h after SRP. Animals were subjected to euthanasia at 7, 14 and 28 days, and samples were submitted to osteoclast quantification, immunological and microtomography analysis.

RESULTS

All treatments resulted in significant periodontal improvements and there was no significant difference between the groups in both local inflammatory response and healing process. Minimal adjunctive effects could be found for the combined therapy in terms of cytokine levels (IL-1β and IL-10), with no statistical significance. However, the number of TRAP-positive osteoclasts per mm of alveolar bone linear surface for the group treated with PDT sessions was significantly lower than those treated with SRP only.

CONCLUSIONS

Multiple PDT sessions with chlorin-e6 and LL-37 nanoemulsion as an adjunct to scaling and root planning reduced the presence of osteoclast in the local site but did not contribute towards bone regeneration and IL-1β and IL-10 levels.

Periodontitis and the risk of oral, gastric and esophageal cancers: a two-sample Mendelian randomization study

BACKGROUND

Periodontitis is a common oral disease and the chronic inflammation caused by it may influence the development of cancers in the upper gastrointestinal tract. Many observational studies have established a relationship between the two, but the results are not entirely consistent.

METHODS

Two-sample MR was performed using publicly available genome-wide association studies data for periodontitis, oral, gastric and oesophagal cancers. The Inverse Variance Weighting (IVW) method serves as the primary method, with MR Egger, Weighted Median, Simple Model and Weighted Model Algorithm methods as complementary methods to assess genetic causal associations. Cochran Q-test, MR-Egger regression and MR polytropic residuals and outliers were used to assess heterogeneity and horizontal pleiotropy.

RESULTS

IVW results did not support a causal association between periodontitis and oral (OR = 1.00, 95% CI: 1.00, 1.00) and oesophagal cancer (OR = 1.00, 95% CI: 1.00, 1.00). Similarly, there was again no causal association between periodontitis and gastric cancer, which was integrated with an OR of 1.04 (95% CI: 0.97, 1.12). Complementary method results were consistent with IVW and heterogeneity and horizontal pleiotropy were not found in most studies.

CONCLUSIONS

The findings of our MR study do not support a causal relationship between periodontitis and oral, gastric and oesophagal cancers.

Causal relationship between periodontal disease-related phenotype and knee osteoarthritis: A two-sample mendelian randomization analysis

OBJECTIVE

This study aimed to explore the bidirectional causal relationship between periodontal disease-related phenotype (PDRP) and knee osteoarthritis (KOA) in a European population using a two-sample Mendelian Randomization (MR) approach.

METHODS

We leveraged publicly available GWAS summary statistics for PDRP (n = 975) and KOA (n = 403,124), assessing their roles as both exposures and outcomes. Our comprehensive MR analysis employed various methods, including inverse variance weighting (IVW), weighted median, Egger regression, simple mode, and weighted mode, to enhance the robustness of our findings. To ensure the reliability of our instrumental variables, we implemented a rigorous screening process based on p-values and F-values, utilized Phenoscanner to investigate potential confounders, and conducted sensitivity analyses.

RESULTS

Our analysis identified five SNPs associated with PDRP and three SNPs with KOA, all surpassing the genome-wide significance threshold, as instrumental variables. The IVW method demonstrated a significant causal relationship from PDRP to KOA (beta = 0.013, SE = 0.007, P = 0.035), without evidence of directional pleiotropy (MR-Egger regression intercept = 0.021, P = 0.706). No support was found for reverse causality from KOA to PDRP, as further MR analyses yielded non-significant P-values. Additionally, funnel plots and Cochran's Q test detected no significant heterogeneity or directional pleiotropy, confirming the robustness of our results. In multivariate analysis, when considering smoking, alcohol consumption, BMI collectively no direct causal relationship between KOA and PDRP. Conversely, smoking and higher BMI were independently associated with an increased risk of KOA.

CONCLUSION

In conclusion, our analysis revealed no direct causal relationship from KOA to PDRP. However, a causal relationship from PDRP to KOA was observed. Notably, when adjusting for potential confounders like smoking, alcohol intake, and BMI, both the causal connection from PDRP to KOA and the inverse relationship were not substantiated.

Periodontal disease increases the severity of chronic obstructive pulmonary disease: a Mendelian randomization study

BACKGROUND

Recent research suggests that periodontitis can increase the risk of chronic obstructive pulmonary disease (COPD). In this study, we performed two-sample Mendelian randomization (MR) and investigated the causal effect of periodontitis (PD) on the genetic prediction of COPD. The study aimed to estimate how exposures affected outcomes.

METHODS

Published data from the Gene-Lifestyle Interaction in the Dental Endpoints (GLIDE) Consortium's genome-wide association studies (GWAS) for periodontitis (17,353 cases and 28,210 controls) and COPD (16,488 cases and 169,688 controls) from European ancestry were utilized. This study employed a two-sample MR analysis approach and applied several complementary methods, including weighted median, inverse variance weighted (IVW), and MR-Egger regression. Multivariable Mendelian randomization (MVMR) analysis was further conducted to mitigate the influence of smoking on COPD.

RESULTS

We chose five single-nucleotide polymorphisms (SNPs) as instrumental variables for periodontitis. A strong genetically predicted causal link between periodontitis and COPD, that is, periodontitis as an independent risk factor for COPD was detected. PD (OR = 1.102951, 95% CI: 1.005-1.211, p = 0.039) MR-Egger regression and weighted median analysis results were coincident with those of the IVW method. According to the sensitivity analysis, horizontal pleiotropy's effect on causal estimations seemed unlikely. However, reverse MR analysis revealed no significant genetic causal association between COPD and periodontitis. IVW (OR = 1.048 > 1, 95%CI: 0.973-1.128, p = 0.2082) MR Egger (OR = 0.826, 95%CI:0.658-1.037, p = 0.1104) and weighted median (OR = 1.043, 95%CI: 0.941-1.156, p = 0.4239). The results of multivariable Mendelian randomization (MVMR) analysis, after adjusting for the confounding effect of smoking, suggest a potential causal relationship between periodontitis and COPD (P = 0.035).

CONCLUSION

In this study, periodontitis was found to be independent of COPD and a significant risk factor, providing new insights into periodontitis-mediated mechanisms underlying COPD development.

Variants in interferon gamma inducible protein 16 (IFI16) and absent in melanoma 2 (AIM2) genes that modulate inflammatory response are associated with periodontitis

OBJECTIVE

Evaluate the association of genetic variants of the interferon gamma inducible protein 16 (IFI16) and absent in melanoma 2 (AIM2) genes with periodontitis.

METHODS

The study involved 117 individuals with periodontitis and 389 without periodontitis, all Brazilians, miscegenated. Individuals with periodontitis presented at least 4 teeth with ≥ 1 site with probing depth ≥ 4 mm; clinical attachment level ≥ 3 mm on the same site and bleeding upon stimulus. Genotyping was performed using the Infinium Multi-Ethnic AMR/AFR-8 Bead Chip focused on Hispanic and African American populations with approximately 2 million markers of the human genome. Multivariate logistic regression was performed to identify associations in additive, dominant and recessive models adjusted for covariates age, obesity, mouth breathing, flossing, asthma, and ancestry.

RESULTS

In IFI16, the rs75985579-A is positively associated with periodontitis in the additive (Odds Ratio adjusted (ORadjusted) 2.65, 95% confidence interval (CI):1.25-5.60, p value: 0.007) and dominant models (ORadjusted 2.56, 95%CI:1.13-5.81, p value: 0.017). In AIM2, the rs76457189-G, is associated negatively with periodontitis in two genetic models evaluated, additive (ORadjusted 0.21, 95%CI:0.05-0.94, p value: 0.022) and dominant (ORadjusted 0.21, 95%CI:0.05-0.94, p value: 0.022).

CONCLUSIONS

These results have shown that variants in the IFI16 and AIM2 genes are associated with periodontitis. Individuals with at least one A (adenine) allele of the rs75985579 (IFI16) are more than twice as likely to have periodontitis, while individuals with the G (guanine) allele of rs76457189 (AIM2) are less likely to be diagnosed with periodontitis, providing a negative association with periodontitis.

Association between periodontitis and COVID-19 infection: a two-sample Mendelian randomization study

Background and Objective

Epidemiological studies report associations between coronavirus disease 2019 (COVID-19) and periodontitis; however, causality has not been proven. The aim of this study is to assess the associations between COVID-19 susceptibility and periodontitis with two-sample Mendelian randomization (MR) analyses.

Methods

A two-sample summary MR analysis was performed using data for outcome and exposure from the OpenGWAS database on people of European descent. Periodontal complex traits (PCTs) were chosen as a proxy for the periodontitis phenotype. The causal association between PCT3 (Aggregatibacter actinomycetemcomitans), PCT5 (Porphyromonas gingivalis), and gingival crevicular fluid (GCF) interleukin-1β (IL-1β) and COVID-19 were considered. Genome-wide association study (GWAS) data with the two largest sample sizes were selected as COVID-19 outcomes (datasets ebi-a-GCST010776 and ebi-a-GCST010777). Single-nucleotide polymorphisms (SNPs) associated with PCT3, PCT5, and GCF IL-1β at statistical significance at genome-wide level (P < 5 × 10^-8) were identified as genetic instruments. We used two-sample summary MR methods and tested the existence of a pleiotropic effect with MR-Egger.

Results

Inverse-variance weighted (IVW) estimates showed that there was a positive association between COVID-19 risk and periodontitis (ebi-a-GCST010776: odds ratio [OR] = 1.02 (95% confidence interval (CI), 1.00-1.05), P = 0.0171; ebi-a-GCST010777: OR = 1.03 (95% CI, 1.00-1.05), P = 0.0397). The weighted median also showed directionally similar estimates. Exploration of the causal associations between other PCTs and COVID-19 identified a slight effect of local inflammatory response (GCF IL-1β) on COVID-19 risk across the two datasets (ebi-a-GCST010776: IVW OR = 1.02 (95% CI, [1.01-1.03]), P < 0.001; ebi-a-GCST010777: IVW OR = 1.03 (95% CI, [1.02-1.04]), P < 0.001). The intercepts of MR-Egger yielded no proof for significant directional pleiotropy for either dataset (ebi-a-GCST010776: P = 0.7660; ebi-a-GCST010777: P = 0.6017).

Conclusions

The findings suggests that periodontitis and the higher GCF IL-1β levels is causally related to increase susceptibility of COVID-19. However, given the limitations of our study, the well-designed randomized controlled trials are needed to confirm its findings, which may represent a new non-pharmaceutical intervention for preventing COVID-19.

TRAF3IP2-IL-17 Axis Strengthens the Gingival Defense against Pathogens

Recent genome-wide association studies have suggested novel risk loci associated with periodontitis, which is initiated by dysbiosis in subgingival plaque and leads to destruction of teeth-supporting structures. One such genetic locus was the tumor necrosis factor receptor-associated factor 3 interacting protein 2 (TRAF3IP2), a gene encoding the gate-keeping interleukin (IL)-17 receptor adaptor. In this study, we first determined that carriers of the lead exonic variant rs13190932 within the TRAF3IP2 locus combined with a high plaque microbial burden was associated with more severe periodontitis than noncarriers. We then demonstrated that TRAF3IP2 is essential in the IL-17-mediated CCL2 and IL-8 chemokine production in primary gingival epithelial cells. Further analysis suggested that rs13190932 may serve a surrogate variant for a genuine loss-of-function variant rs33980500 within the same gene. Traf3ip2 null mice (Traf3ip2^-/-) were more susceptible than wild-type (WT) mice to the Porphyromonas gingivalis-induced periodontal alveolar bone loss. Such bone loss was associated with a delayed P. gingivalis clearance and an attenuated neutrophil recruitment in the gingiva of Traf3ip2^-/- mice. Transcriptomic data showed decreased expression of antimicrobial genes, including Lcn2, S100a8, and Defb1, in the Traf3ip2^-/- mouse gingiva in comparison to WT mice prior to or upon P. gingivalis oral challenge. Further 16S ribosomal RNA sequencing analysis identified a distinct microbial community in the Traf3ip2^-/- mouse oral plaque, which was featured by a reduced microbial diversity and an overabundance of Streptococcus genus bacteria. More P. gingivalis was observed in the Traf3ip2^-/- mouse gingiva than WT control animals in a ligature-promoted P. gingivalis invasion model. In agreement, neutrophil depletion resulted in more local gingival tissue invasion by P. gingivalis. Thus, we identified a homeostatic IL-17-TRAF3IP2-neutrophil axis underpinning host defense against a keystone periodontal pathogen.

UBE3D Regulates mRNA 3'-End Processing and Maintains Adipogenic Potential in 3T3-L1 Cells

We have previously described the role of an essential Saccharomyces cerevisiae gene, important for cleavage and polyadenylation 1 (IPA1), in the regulation of gene expression through its interaction with Ysh1, the endonuclease subunit of the mRNA 3'-end processing complex. Through a similar mechanism, the mammalian homolog ubiquitin protein ligase E3D (UBE3D) promotes the migratory and invasive potential of breast cancer cells, but its role in the regulation of gene expression during normal cellular differentiation has not previously been described. In this study, we show that CRISPR/Cas9-mediated knockout of Ube3d in 3T3-L1 cells blocks their ability to differentiate into mature adipocytes. Consistent with previous studies in other cell types, Ube3d knockout leads to decreased levels of CPSF73 and global changes in cellular mRNAs indicative of a loss of 3'-end processing capacity. Ube3d knockout cells also display decreased expression of known preadipogenic markers. Overexpression of either UBE3D or CPSF73 rescues the differentiation defect and partially restores protein levels of these markers. These results support a model in which UBE3D is necessary for the maintenance of the adipocyte-committed state via its regulation of the mRNA 3'-end processing machinery.

Therapeutic and Metagenomic Potential of the Biomolecular Therapies against Periodontitis and the Oral Microbiome: Current Evidence and Future Perspectives

The principles of periodontal therapy are based on the control of microbial pathogens and host factors that contribute to biofilm dysbiosis, with the aim of modulating the progression of periodontitis and periodontal tissue destruction. It is currently known how differently each individual responds to periodontal treatment, depending on both the bacterial subtypes that make up the dysbiotic biofilm and interindividual variations in the host inflammatory response. This has allowed the current variety of approaches for the management of periodontitis to be updated by defining the goals of target strategies, which consist of reducing the periodontopathogenic microbial flora and/or modulating the host-mediated response. Therefore, this review aims to update the current variety of approaches for the management of periodontitis based on recent target therapies. Recently, encouraging results have been obtained from several studies exploring the effects of some targeted therapies in the medium- and long-term. Among the most promising target therapies analyzed and explored in this review include: cell-based periodontal regeneration, mediators against bone resorption, emdogain (EMD), platelet-rich plasma, and growth factors. The reviewed evidence supports the hypothesis that the therapeutic combination of epigenetic modifications of periodontal tissues, interacting with the dysbiotic biofilm, is a key step in significantly reducing the development and progression of disease in periodontal patients and improving the therapeutic response of periodontal patients. However, although studies indicate promising results, these need to be further expanded and studied to truly realize the benefits that targeted therapies could bring in the treatment of periodontitis.

Next-Generation Examination, Diagnosis, and Personalized Medicine in Periodontal Disease

Periodontal disease, a major cause of tooth loss, is an infectious disease caused by bacteria with the additional aspect of being a noncommunicable disease closely related to lifestyle. Tissue destruction based on chronic inflammation is influenced by host and environmental factors. The treatment of periodontal disease varies according to the condition of each individual patient. Although guidelines provide standardized treatment, optimization is difficult because of the wide range of treatment options and variations in the ideas and skills of the treating practitioner. The new medical concepts of “precision medicine” and “personalized medicine” can provide more predictive treatment than conventional methods by stratifying patients in detail and prescribing treatment methods accordingly. This requires a new diagnostic system that integrates information on individual patient backgrounds (biomarkers, genetics, environment, and lifestyle) with conventional medical examination information. Currently, various biomarkers and other new examination indices are being investigated, and studies on periodontal disease-related genes and the complexity of oral bacteria are underway. This review discusses the possibilities and future challenges of precision periodontics and describes the new generation of laboratory methods and advanced periodontal disease treatment approaches as the basis for this new field.

Role of RBMS3 Novel Potential Regulator of the EMT Phenomenon in Physiological and Pathological Processes

RNA-binding protein 3 (RBMS3) plays a significant role in embryonic development and the pathogenesis of many diseases, especially cancer initiation and progression. The multiple roles of RBMS3 are conditioned by its numerous alternative expression products. It has been proven that the main form of RBMS3 influences the regulation of microRNA expression or stabilization. The absence of RBMS3 activates the Wnt/β-catenin pathway. The expression of c-Myc, another target of the Wnt/β-catenin pathway, is correlated with the RBMS3 expression. Numerous studies have focused solely on the interaction of RBMS3 with the epithelial-mesenchymal transition (EMT) protein machinery. EMT plays a vital role in cancer progression, in which RBMS3 is a new potential regulator. It is also significant that RBMS3 may act as a prognostic factor of overall survival (OS) in different types of cancer. This review presents the current state of knowledge about the role of RBMS3 in physiological and pathological processes, with particular emphasis on carcinogenesis. The molecular mechanisms underlying the role of RBMS3 are not fully understood; hence, a broader explanation and understanding is still needed.

Interferon activated gene 204 protects against bone loss in experimental periodontitis

BACKGROUND

Periodontal destruction can be the result of different known and yet-to-be-discovered biological pathways. Recent human genetic association studies have implicated interferon-gamma inducible protein 16 (IFI16) and absent in melanoma 2 (AIM2) with high periodontal interleukin (IL)-1β levels and more destructive disease, but mechanistic evidence is lacking. Here, we sought to experimentally validate these observational associations and better understand IFI16 and AIM2's roles in periodontitis.

METHODS

Periodontitis was induced in Ifi204-/- (IFI16 murine homolog) and Aim2-/- mice using the ligature model. Chimeric mice were created to identify the main source cells of Ifi204 in the periodontium. IFI16-silenced human endothelial cells were treated with periodontal pathogens in vitro. Periodontal tissues from Ifi204-/- mice were evaluated for alveolar bone (micro-CT), cell inflammatory infiltration (MPO+ staining), Il1b (qRT-PCR), and osteoclast numbers (cathepsin K+ staining).

RESULTS

Ifi204-deficient mice> exhibited >20% higher alveolar bone loss than wild-type (WT) (P < 0.05), while no significant difference was found in Aim2-/- mice. Ifi204's effect on bone loss was primarily mediated by a nonbone marrow source and was independent of Aim2. Ifi204-deficient mice had greater neutrophil/macrophage trafficking into gingival tissues regardless of periodontitis development compared to WT. In human endothelial cells, IFI16 decreased the chemokine response to periodontal pathogens. In murine periodontitis, Ifi204 depletion elevated gingival Il1b and increased osteoclast numbers at diseased sites (P < 0.05).

CONCLUSIONS

These findings support IFI16's role as a novel regulator of inflammatory cell trafficking to the periodontium that protects against bone loss and offers potential targets for the development of new periodontal disease biomarkers and therapeutics.

Targeting the mRNA endonuclease CPSF73 inhibits breast cancer cell migration, invasion, and self-renewal

Cleavage by the endonuclease CPSF73 and polyadenylation of nascent RNA is an essential step in co-transcriptional mRNA maturation. Recent work has surprisingly identified CPSF73 as a promising drug target for inhibiting the growth of specific cancers, triggering further studies on understanding CPSF73 regulation and functions in cells. Here, we report that a HECT-like E3 ligase, UBE3D, participates in stabilizing CPFS73 protein by preventing its ubiquitin-mediated degradation by the proteasome. Depletion of UBE3D leads to CPSF73 downregulation, a pre-mRNA cleavage defect, and dysregulated gene expression in cells. UBE3D dysfunction or chemical inactivation of CPSF73 inhibited migration and invasion as well as stem cell renewal phenotypes in vitro in triple-negative breast cancer cells. In addition, genetic overexpression of CPSF73 promoted breast cancer stemness and knocking down CPSF73 inhibited stem cell renewal properties. Together, our findings indicate that targeting the pre-mRNA processing nuclease CPSF73 has potential for breast cancer therapy.

Covid-19 and SARS-CoV-2 infection in periodontology: A narrative review

The present review examined the available evidence on possible involvement of gingival tissues in SARS‐CoV‐2 infection. Gingival tissue possess SARS‐CoV‐2 entry and transmission factors, among them ACE2 (angiotensin‐converting enzyme 2) and TMPRSS2 (transmembrane protease serine 2), which are the principal mediators of the virus cell invasion. Clinical observations reveal SARS‐CoV‐2 RNA in periodontal tissues and crevicular fluid, suggesting that the periodontium may act as an entry point for the virus and/or as a dissemination site. The preliminary observations prove infection potential of gingival crevicular fluid and shed epithelial cells from the periodontium. There are also findings on potential associations between periodontitis and Covid‐19 (coronavirus disease 2019). PubMed and Scopus databases were used to search for suitable keywords such as: SARS‐CoV‐2, Covid‐19, oral virus infection, gingival crevicular fluid, oral mucosa, periodontium, gingiva, ACE2, TMPRSS2, Furin, diagnosis, topical treatment, vaccine and the related words for relevant publications. Data extraction and quality valuation of articles were performed by the author. The review addressed seven major domains: periodontal structures as SARS‐CoV‐2 infection site, the periodontal changes under SARS‐CoV‐2 infection, potential associations between periodontitis and Covid‐19, periodontal oral care in Covid‐19, crevicular fluid as potential transmission factor and preventive measures. The search process in PubMed and Scopus was updated up to 31 March 2022. Finally 68 articles were retrieved for the final analysis, from the initial database searches. According to the inclusion criteria articles in English language without any date restriction were included. The included studies were mostly original articles, and published in 2020 and 2021 with the aim to describe Covid‐19 and SARS‐CoV‐2 infection in periodontology. As a conclusion it can be stated that gingival tissues may play a role in SARS‐CoV‐2 infection.

Periodontitis and COVID-19: Biological Mechanisms and Meta-analyses of Epidemiological Evidence

Since the beginning of 2020, the entire global health care system has been severely challenged by the outbreak of coronavirus 2019 disease (COVID-19). Robust evidence has demonstrated a more severe course of COVID-19 in the presence of several comorbidities, such as cardiovascular diseases, diabetes mellitus, and obesity. Here, we critically appraise the recent research discoveries linking periodontitis to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and to severe COVID-19, with a special focus on the associated biological mechanisms and the available epidemiological evidence. SARS-CoV-2 main receptors and coreceptors (ACE2, TMPRSS2, furin, CD147) are overexpressed in periodontal tissues of periodontitis patients, with inflammation, periodontal pathogens, and damage-induced pyroptosis triggering a positive feedback loop. However, meta-analyses of epidemiological studies only indicated a nonstatistically significant tendency for an increased risk of SARS-CoV-2 infection in subjects with periodontitis (odds ratio [OR] = 1.69; 95% CI, 0.91-3.13, P = 0.09). Furthermore, periodontitis may worsen clinical COVID-19 courses through multiple direct and indirect pathways, including damage to lower airways due to aspiration of periodontal pathogens, exacerbation of the cytokine storm via the low-grade chronic systemic inflammation, and SARS-CoV-2 dissemination through the ulcerated gingival epithelium with consequent induced pulmonary vessels vasculopathy. Indeed, meta-analyses of epidemiological studies indicated that periodontitis subjects are more likely to experience a more severe course of COVID-19. Specifically, periodontitis was associated with a 4-fold increased odds of hospitalization (OR = 4.72; 95% CI, 1.11-20.03, P = 0.04), 6-fold of requiring assisted ventilation (OR = 6.24; 95% CI, 2.78-14.02, P = 0.00), and more than 7-fold of death due to COVID-19 complications (OR = 7.51; 95% CI, 2.16-26.10, P = 0.00). The breakthrough analyzed here emphasizes the relevance of the mouth-systemic connection as a target to mitigate the current COVID-19 emergency and the future predicted coronavirus pandemics.

Replication of gene polymorphisms associated with periodontitis-related traits in an elderly cohort: the Washington Heights/Inwood Community Aging Project Ancillary Study of Oral Health

AIM

We sought to replicate findings from published genome-wide association studies (GWAS), linking specific candidate gene loci with periodontitis-related clinical/microbial traits.

MATERIALS AND METHODS

In the published GWAS, a total of 2196 single nucleotide polymorphisms associated with periodontitis-related traits at a p ≤ 5 × 10^-6 and mapped to 136 gene loci. The replication cohort included 1124 individuals, 65-98 years old (67% female, 45% Hispanic, 30% Black, 23% White) with available genome-wide genotypes and full-mouth periodontal status. Microbial profiles using checkerboard DNA-DNA hybridization and 16SrRNA sequencing were available from 912 and 739 participants, respectively.

RESULTS

Using gene-specific p-values after linkage disequilibrium pruning, the following gene/phenotype associations replicated successfully: CLEC19A with edentulism and %teeth with pocket depth (PD) ≥4 mm; IL37, HPVC1, TRPS1, ABHD12B, LDLRAD4 (C180rF1), TGM3, and GRK5 with %teeth with PD ≥4 mm; DAB2IP with presence of PD ≥6 mm; KIAA1715(LNPK), ROBO2, RAB28, LINC01017, NELL1, LDLRAD4(C18orF1), and CRYBB2P1 with %teeth with clinical attachment level (CAL) ≥3 mm; RUNX2 and LAMA2 with %teeth with CAL ≥5 mm; and KIAA1715(LNPK) with high colonization by Aggregatibacter actinomycetemcomitans. In addition, CLEC19A, IQSEC1, and EMR1 associated with microbial abundance based on checkerboard data, LBP and NCR2 with abundance based on sequencing data, and NCR2 with microbial diversity based on sequencing data.

CONCLUSIONS

Several gene loci identified in published GWAS as associated with periodontitis-related phenotypes replicated successfully in an elderly cohort.

Systems Biology in Periodontitis

Systems biology is a promising scientific discipline that allows an integrated investigation of host factors, microbial composition, biomarkers, immune response and inflammatory mediators in many conditions such as chronic diseases, cancer, neurological disorders, and periodontitis. This concept utilizes genetic decoding, bioinformatic, flux-balance analysis in a comprehensive approach. The aim of this review is to better understand the current literature on systems biology and identify a clear applicability of it to periodontitis. We will mostly focus on the association between this condition and topics such as genomics, transcriptomics, proteomics, metabolomics, as well as contextualize delivery systems for periodontitis treatment, biomarker detection in oral fluids and associated systemic conditions.

Periodontal infectogenomics: a systematic review update of associations between host genetic variants and subgingival microbial detection

Objective

The aim of this study was to systematically update the evidence for associations between host genetic variants and subgingival microbial detection and counts.

Materials and methods

Following a previous systematic review (Nibali et al. J Clin Periodontol 43(11): 889-900, 15), an update of a systematic search of the literature was conducted in Ovid Medline, Embase, LILACS, and Cochrane Library for studies reporting data on host genetic variants and detection of microbes subgingivally published in the last 6 years.

Results

A total of 19 studies were included in the review, from an initial search of 2797 titles. Studies consisted mainly of candidate gene studies and of one genome-wide analysis. A total of 62 studies were considered for summary findings, including 43 identified in the previous systematic review of studies published up to 2015. Meta-analyses were done when appropriate including both papers in the original review and in the update. Meta-analyses revealed lack of associations between IL1 composite genotype and subgingival detection of Aggregatibacter acinomycetemcomitans, Poprhyromonas gingivalis, Tannerella forsythia, Treponema denticola, and Prevotella intermedia. Promising evidence is emerging from other genetic variants and from sub-analyses of data from genome-association studies. Among other studies with candidate-gene, target SNPs were mainly within the IL10, IL6, IL4, IL8, IL17A, and VDR gene.

Conclusions

IL1 composite genotype does not seem to be associated with subgingival microbial detection. Promising associations should be pursued by future studies, including studies employing -OMICS technologies.

Clinical relevance

A better knowledge of which host genetic variant predispose to subgingival microbial colonization and to the development of progression of periodontal disease could potentially help to better understand periodontal disease pathogenesis and help with its management.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00784-021-04233-8.

Effect of Dextranase and Dextranase-and-Nisin-Containing Mouthwashes on Oral Microbial Community of Healthy Adults—A Pilot Study

This study analyzed the alteration of oral microbial composition in healthy subjects after using dextranase-containing mouthwash (DMW; Mouthwash formulation I) and dextranase-and-nisin-containing mouthwash (DNMW; Mouthwash formulation II). Eighteen participants were recruited and were randomly allocated to two groups: G1 (DMW user; n = 8) and G2 (DNMW user; n = 10). The subjects were instructed to use the provided mouthwash regularly twice a day for 30 days. The bleeding on probing (BOP), plaque index (PI), probing depth (PBD), and gingival index (GI) were analyzed, and saliva samples were collected before (day 0) and after (day 30) the use of mouthwashes. The saliva metagenomic DNA was extracted and sequenced (next-generation sequencing, Miseq paired-end Illumina 2 × 250 bp platform). The oral microbial community in the pre-and post-treated samples were annotated using QIIME 2™. The results showed the PI and PBD values were significantly reduced in G2 samples. The BOP and GI values of both groups were not significantly altered. The post-treated samples of both groups yielded a reduced amount of microbial DNA. The computed phylogenetic diversity, species richness, and evenness were reduced significantly in the post-treated samples of G2 compared to the post-treated G1 samples. The mouthwash formulations also supported some pathogens’ growth, which indicated that formulations required further improvement. The study needs further experiments to conclude the results. The study suggested that the improved DNMW could be an adjuvant product to improve oral hygiene.

Periodontal disease increases the host susceptibility to COVID-19 and its severity: a Mendelian randomization study

Background

Emerging evidence shows that periodontal disease (PD) may increase the risk of Coronavirus disease 2019 (COVID-19) complications. Here, we undertook a two-sample Mendelian randomization (MR) study, and investigated for the first time the possible causal impact of PD on host susceptibility to COVID-19 and its severity.

Methods

Summary statistics of COVID-19 susceptibility and severity were retrieved from the COVID-19 Host Genetics Initiative and used as outcomes. Single nucleotide polymorphisms associated with PD in Genome-wide association study were included as exposure. Inverse-variance weighted (IVW) method was employed as the main approach to analyze the causal relationships between PD and COVID-19. Three additional methods were adopted, allowing the existence of horizontal pleiotropy, including MR-Egger regression, weighted median and weighted mode methods. Comprehensive sensitivity analyses were also conducted for estimating the robustness of the identified associations.

Results

The MR estimates showed that PD was significantly associated with significantly higher susceptibility to COVID-19 using IVW (OR = 1.024, P = 0.017, 95% CI 1.004–1.045) and weighted median method (OR = 1.029, P = 0.024, 95% CI 1.003–1.055). Furthermore, it revealed that PD was significantly linked to COVID-19 severity based on the comparison of hospitalization versus population controls (IVW, OR = 1.025, P = 0.039, 95% CI 1.001–1.049; weighted median, OR = 1.030, P = 0.027, 95% CI 1.003–1.058). No such association was observed in the cohort of highly severe cases confirmed versus those not hospitalized due to COVID-19.

Conclusions

We provide evidence on the possible causality of PD accounting for the susceptibility and severity of COVID-19, highlighting the importance of oral/periodontal healthcare for general wellbeing during the pandemic and beyond.

Oral Colonization by Entamoeba gingivalis and Trichomonas tenax: A PCR-Based Study in Health, Gingivitis, and Periodontitis

Background

The etiology of periodontitis remains unclear, as is the place of gingivitis in its pathophysiology. A few studies linked the colonization by oral parasites (Entamoeba gingivalis and Trichomonas tenax) to periodontal disease and its severity. The aim of the current study was to estimate the prevalence of these oral parasites among healthy individuals, and in patients with gingivitis and periodontitis in Jordan.

Methods

The study was conducted during July 2019–December 2019. Samples were composed of saliva and periodontal material including dental plaque sampled with probes. The detection of oral parasites was done using conventional polymerase chain reaction (PCR).

Results

The total number of study participants was 237: healthy (n=94), gingivitis (n=53) and periodontitis (n=90). The prevalence of E. gingivalis was 88.9% among the periodontitis patients, 84.9% among the gingivitis patients and 47.9% in the healthy group. For T. tenax, the prevalence was 25.6% among the periodontitis patients, 5.7% among the gingivitis patients and 3.2% in the heathy group. Positivity for E. gingivalis was significantly correlated with the presence of periodontal disease compared to the healthy group with odds ratio (OR) of 6.6. Periodontal disease was also correlated with lower monthly income (OR=8.2), lack of dental care (OR=4.8), and history of diabetes mellitus (OR=4.5). Colonization by E. gingivalis was correlated with gingivitis (OR=6.1) compared to the healthy group. Colonization by E. gingivalis and T. tenax were significantly correlated with periodontitis (OR=6.4 for E. gingivalis, and OR=4.7, for T. tenax) compared to the healthy group. T. tenax was only detected among individuals with generalized periodontal disease compared to its total absence among those with localized disease (19.6% vs. 0.0%; p=0.039). The co-infection rate by the two oral parasites was 11.0%.

Conclusions

The higher prevalence of human oral parasites in periodontal disease compared to healthy individuals appears to be more than a mere marker for the disease and might also be associated with disease severity and potential for progression. Thus, the dogmatic view of E. gingivalis and T. tenax as commensals needs to be re-evaluated and their contribution to pathophysiology of periodontal diseases cannot be neglected.

Impaired function of epithelial plakophilin-2 is associated with periodontal disease

BACKGROUND AND OBJECTIVES

Plakophilin-2 (PKP2) is an intracellular desmosomal anchoring protein that has been implicated in a genome-wide association study, in which genetic variants of PKP2 are associated with Porphyromonas gingivalis (P.gingivalis) -dominant periodontal dysbiosis. In this study, we compared the ex vivo PKP2 expression in periodontitis gingival biopsies to periodontitis-free subjects and assessed the in vitro role of PKP2 in gingival epithelial barrier function and the mechanism by which P.gingivalis modulates PKP2 expression.

MATERIAL AND METHODS

Using reverse transcription quantitative real-time PCR (RT-qPCR), we determined PKP2 mRNA expression levels in gingival biopsies collected from 11 periodontally healthy, 10 experimental gingivitis, and 10 chronic periodontitis subjects. PKP2 protein expression in gingival biopsies was detected by immunohistochemistry. We then challenged primary gingival epithelial cells with bacteria including P.gingivalis, Campylobacter rectus, and various Toll-like receptor agonists. Western blot and immunofluorescence staining were used to detect protein expression. Inhibitors blocking proteases pathways were tested for P.gingivalis-mediated PKP2 protein degradations. We also knocked down endogenous epithelial PKP2 using lentiviral short-hairpin RNA (shRNA) and evaluated cell proliferation, spreading, and barrier function.

RESULTS

Periodontitis gingival biopsies had approximately twofold less PKP2 mRNA than did healthy controls (p < .05). PKP2 protein was predominantly expressed in gingival epithelium. In primary gingival epithelial cells, P.gingivalis challenge increased PKP2 mRNA levels, while protein expression decreased, which suggests that P.gingivalis has a protein degradation mechanism. Cysteine proteases inhibitors greatly attenuated P.gingivalis-mediated PKP2 protein degradation. Epithelial cells with deficient PKP2 exhibited inhibited cell proliferation and spreading and failed to form monolayers. Finally, P.gingivalis impaired gingival epithelial barrier function.

CONCLUSIONS

PKP2 appears to be critical in maintaining gingival epithelial barrier function and is susceptible to degradation by cysteine proteases produced by P.gingivalis. Our findings have identified a mechanism by which P.gingivalis impairs epithelial barrier function by promoting PKP2 degradation.

Distinct Microbial Signatures between Periodontal Profile Classes

Precise classification of periodontal disease has been the objective of concerted efforts and has led to the introduction of new consensus-based and data-driven classifications. The purpose of this study was to characterize the microbiological signatures of a latent class analysis (LCA)-derived periodontal stratification system, the Periodontal Profile Class (PPC) taxonomy. We used demographic, microbial (subgingival biofilm composition), and immunological data (serum IgG antibody levels, obtained with checkerboard immunoblotting technique) for 1,450 adult participants of the Dental Atherosclerosis Risk in Communities (ARIC) study, with already generated PPC classifications. Analyses relied on t tests and generalized linear models with Bonferroni correction. Men and African Americans had higher systemic antibody levels against most microorganisms compared to women and Caucasians (P < 0.05). Healthy individuals (PPC-I) had low levels of biofilm bacteria and serum IgG levels against most periodontal pathogens (P < 0.05). Subjects with mild to moderate disease (PPC-II to PPC-III) showed mild/moderate colonization of multiple biofilm pathogens. Individuals with severe disease (PPC-IV) had moderate/high levels of biofilm pathogens and antibody levels for orange/red complexes. High gingival index individuals (PPC-V) showed moderate/high levels of biofilm Campylobacter rectus and Aggregatibacter actinomycetemcomitans. Biofilm composition in individuals with reduced periodontium (PPC-VI) was similar to health but showed moderate to high antibody responses. Those with severe tooth loss (PPC-VII) had significantly high levels of multiple biofilm pathogens, while the systemic antibody response to these microorganisms was comparable to health. The results support a biologic basis for elevated risk for periodontal disease in men and African Americans. Periodontally healthy individuals showed a low biofilm pathogen and low systemic antibody burden. In the presence of PPC disease, a microbial-host imbalance characterized by higher microbial biofilm colonization and/or systemic IgG responses was identified. These results support the notion that subgroups identified by the PPC system present distinct microbial profiles and may be useful in designing future precise biological treatment interventions.

Identification of novel genome-wide pleiotropic associations with oral inflammatory traits

Oral inflammatory diseases (OIDs) are a group of dental diseases with multiple clinical manifestations that impact the majority of the world's population. Many studies have investigated the associations between individual OID traits and genomic variants, but whether pleiotropic loci are shared by oral inflammatory traits remains poorly understood. Here, we conducted multitrait joint analyses based on the summary statistics of genome-wide association studies (GWASs) of five dental traits from the UK Biobank. Among these genome-wide significant loci, two were novel for both painful gums and toothache. We identified causal variants at each novel locus, and functional annotation based on multiomics data suggested IL10 and IL12A/TRIM59 as potential candidate genes at the novel pleiotropic loci. Subsequent analyses of pathway enrichment and protein-protein interaction networks suggested the involvement of the candidate genes in immune regulation. In conclusion, our results uncover novel pleiotropic loci for OID traits and highlight the importance of immune regulation in the pathogenesis of OIDs. These findings will enhance our understanding of the pathogenesis of OIDs and be beneficial for risk screening, prevention, and the development of novel drugs targeting the immune regulation of OIDs.

Human oral mucosa cell atlas reveals a stromal-neutrophil axis regulating tissue immunity

The oral mucosa remains an understudied barrier tissue. This is a site of rich exposure to antigens and commensals, and a tissue susceptible to one of the most prevalent human inflammatory diseases, periodontitis. To aid in understanding tissue-specific pathophysiology, we compile a single-cell transcriptome atlas of human oral mucosa in healthy individuals and patients with periodontitis. We uncover the complex cellular landscape of oral mucosal tissues and identify epithelial and stromal cell populations with inflammatory signatures that promote antimicrobial defenses and neutrophil recruitment. Our findings link exaggerated stromal cell responsiveness with enhanced neutrophil and leukocyte infiltration in periodontitis. Our work provides a resource characterizing the role of tissue stroma in regulating mucosal tissue homeostasis and disease pathogenesis.

Two-Sample Mendelian Randomization Analysis of Associations Between Periodontal Disease and Risk of Cancer

Background

Observational studies indicate that periodontal disease may increase the risk of colorectal, lung, and pancreatic cancers. Using a 2-sample Mendelian randomization (MR) analysis, we assessed whether a genetic predisposition index for periodontal disease was associated with colorectal, lung, or pancreatic cancer risks.

Methods

Our primary instrument included single nucleotide polymorphisms with strong genome-wide association study evidence for associations with chronic, aggressive, and/or severe periodontal disease (rs729876, rs1537415, rs2738058, rs12461706, rs16870060, rs2521634, rs3826782, and rs7762544). We used summary-level genetic data for colorectal cancer (n = 58 131 cases; Genetics and Epidemiology of Colorectal Cancer Consortium, Colon Cancer Family Registry, and Colorectal Transdisciplinary Study), lung cancer (n = 18 082 cases; International Lung Cancer Consortium), and pancreatic cancer (n = 9254 cases; Pancreatic Cancer Consortia). Four MR approaches were employed for this analysis: random-effects inverse-variance weighted (primary analyses), Mendelian Randomization-Pleiotropy RESidual Sum and Outlier, simple median, and weighted median. We conducted secondary analyses to determine if associations varied by cancer subtype (colorectal cancer location, lung cancer histology), sex (colorectal and pancreatic cancers), or smoking history (lung and pancreatic cancer). All statistical tests were 2-sided.

Results

The genetic predisposition index for chronic or aggressive periodontitis was statistically significantly associated with a 3% increased risk of colorectal cancer (per unit increase in genetic index of periodontal disease; P = .03), 3% increased risk of colon cancer (P = .02), 4% increased risk of proximal colon cancer (P = .01), and 3% increased risk of colorectal cancer among females (P = .04); however, it was not statistically significantly associated with the risk of lung cancer or pancreatic cancer, overall or within most subgroups.

Conclusions

Genetic predisposition to periodontitis may be associated with colorectal cancer risk. Further research should determine whether increased periodontitis prevention and increased cancer surveillance of patients with periodontitis is warranted.

Periodontitis and pulmonary function: a Mendelian randomization study

Objectives

Observational research suggests that periodontitis affects pulmonary function; however, observational studies are subject to confounding and reverse causation, making causal inference and the direction of these associations difficult. We used Mendelian randomization (MR) to assess the potential causal association between genetic liability to periodontitis and pulmonary function.

Materials and methods

We used six single-nucleotide polymorphisms (SNPs) associated with periodontitis (P < 5 × 10⁻⁶) from a genome-wide association study (GWAS) of 17,353 European descent periodontitis cases and 28,210 controls from the GeneLifestyle Interactions in Dental Endpoints consortium and the UK Biobank, and related these to SNPs from a lung function GWAS including 79,055 study participants of the SpiroMeta Consortium.

Results

MR analysis suggested no effect of periodontitis on the ratio of forced expiratory volume in one second to lower forced vital capacity (standard deviation increment in outcome per doubling of the odds of the exposure (95% confidence interval) =  − 0.004 (− 0.028; 0.020)). Replication analysis using genetic instruments from two different GWAS and sensitivity analyses to address potential pleiotropy led to no substantial changes in estimates.

Conclusions

Collectively, these findings do not support a relationship between genetic liability for periodontitis and pulmonary function.

Clinical relevance

Periodontitis does not seem to be a risk factor for worsening of pulmonary function.

Causal Association between Periodontitis and Parkinson's Disease: A Bidirectional Mendelian Randomization Study

The latest evidence revealed a possible association between periodontitis and Parkinson’s disease (PD). We explored the causal relationship of this bidirectional association through two-sample Mendelian randomization (MR) in European ancestry populations. To this end, we used openly accessible data of genome-wide association studies (GWAS) on periodontitis and PD. As instrumental variables for periodontitis, seventeen single-nucleotide polymorphisms (SNPs) from a GWAS of periodontitis (1817 periodontitis cases vs. 2215 controls) and eight non-overlapping SNPs of periodontitis from an additional GWAS for validation purposes. Instrumental variables to explore for the reverse causation included forty-five SNPs from a GWAS of PD (20,184 cases and 397,324 controls). Multiple approaches of MR were carried-out. There was no evidence of genetic liability of periodontitis being associated with a higher risk of PD (B = −0.0003, Standard Error [SE] 0.0003, p = 0.26). The eight independent SNPs (B = −0.0000, SE 0.0001, p = 0.99) validated this outcome. We also found no association of genetically primed PD towards periodontitis (B = −0.0001, SE 0.0001, p = 0.19). These MR study findings do not support a bidirectional causal genetic liability between periodontitis and PD. Further GWAS studies are needed to confirm the consistency of these results.

Genome-wide association study of stage III/IV grade C periodontitis (former aggressive periodontitis) in a Spanish population

AIM

To identify loci associated with stages III/IV, grade C periodontitis (PIII/IV-C) through a genome-wide association study (GWAS).

MATERIALS AND METHODS

441 Caucasian Spanish PIII/IV-C cases from the SEPA Network of Research Clinics and 1141 controls from the Banco Nacional de ADN were genotyped with "Axiom Spain Biobank Array," which contains 757836 markers, including rare and low-frequency Spanish variants. The analysis of the individual association and subsequently the gene-level analysis with Sequence Kernel Association Test (SKAT) were carried out adjusting for age, sex and PC1 covariates. Pathway Analysis was additionally performed with Ingenuity Pathway Analysis (IPA) software on the top associated genes.

RESULTS

In the individual analyses, no genome-wide significant signals were detected. However, 8 SNPs of 8 loci reached suggestive evidence of association with PIII/IV-C, including FAT3 rs35709256, CSNK1G2 rs4807188, MYH13 rs2074872, CNTN2 rs116611488, ANTXR1 rs4854545, 8p23.2 rs78672540, ANGPT1 rs13439823 and PLEC rs11993287 (p < 5 × 10^-6 ). SKAT analysis identified other interesting signals at CNTN2, FBXO44, AP1M2, RSPO4, KRI1, BPIFB1 and INMT, although their probability does not exceed the multiple-test correction. IPA indicated significant enrichment of pathways related to cAMP, IL-2, CD28, VDR/RXR and PI3K/Akt.  CONCLUSIONS: GWAS found no SNPs significantly associated with PIII/IV-C.

These Are the Genes You're Looking For: Finding Host Resistance Genes

Humanity's ongoing struggle with new, re-emerging and endemic infectious diseases serves as a frequent reminder of the need to understand host-pathogen interactions. Recent advances in genomics have dramatically advanced our understanding of how genetics contributes to host resistance or susceptibility to bacterial infection. Here we discuss current trends in defining host-bacterial interactions at the genome-wide level, including screens that harness CRISPR/Cas9 genome editing, natural genetic variation, proteomics, and transcriptomics. We report on the merits, limitations, and findings of these innovative screens and discuss their complementary nature. Finally, we speculate on future innovation as we continue to progress through the postgenomic era and towards deeper mechanistic insight and clinical applications.

Using national register data to estimate the heritability of periodontitis

AIM

To identify whether periodontal traits derived from electronic dental records are biologically informative and heritable.

MATERIALS AND METHODS

The study included 11,974 adult twins (aged 30-92 years) in the Swedish Twin Registry. Periodontal records from dental examinations were retrieved from a national register and used to derive continuous measures of periodontal health. A latent class approach was used to derive categorial measures of periodontal status. The correlation patterns in these traits were contrasted in monozygotic and dizygotic twin pairs using quantitative genetic models to estimate the heritability of the traits.

RESULTS

For continuous traits, heritability estimates ranged between 41.5% and 48.3% with the highest estimates for number of missing tooth surfaces and rate of change in number of deep periodontal pockets (≥6 mm). For categorial traits, the latent class approach identified three classes (good periodontal health, mild periodontitis signs and severe signs of periodontitis) and there was a clear difference in the hazard for subsequent tooth loss between these three classes. Despite this, the class allocations were only slightly more heritable than a conventional dichotomous disease definition (45.2% vs. 42.6%).

CONCLUSIONS

Periodontitis is a moderately heritable disease. Quantitative periodontal traits derived from electronic records are an attractive target for future genetic association studies.

Assessment of Bidirectional Relationships Between Polycystic Ovary Syndrome and Periodontitis: Insights From a Mendelian Randomization Analysis

Background

Observational studies have indicated an association between polycystic ovary syndrome (PCOS) and periodontitis, but it is unclear whether the association is cofounded or causal. We conducted a two-sample Mendelian randomization (MR) study to investigate the bidirectional relationship between genetically predicted PCOS and periodontitis.

Methods

From two genome-wide association studies we selected 13 and 7 single nucleotide polymorphisms associated with PCOS and periodontitis, respectively, as instrumental variables. We utilized publicly shared summary-level statistics from European-ancestry cohorts. To explore the causal effect of PCOS on periodontitis, 12,289 cases of periodontitis and 22,326 controls were incorporated, while 4,890 cases of PCOS and 20,405 controls in the reverse MR. Inverse-variance weighted method was employed in the primary MR analysis and multiple sensitivity analyses were implemented.

Results

Genetically determined PCOS was not causally associated with risk of periodontitis (odds ratio 0.97; 95% confidence interval 0.88-1.06; P = 0.50) per one-unit increase in the log-odds ratio of periodontitis. Similarly, no causal effect of periodontitis on PCOS was shown with the odds ratio for PCOS was 1.17 (95% confidence interval 0.91-1.49; P = 0.21) per one-unit increase in the log-odds ratio of periodontitis. Consistent results were yielded via additional MR methods. Sensitivity analyses demonstrated no presence of horizontal pleiotropy or heterogeneity.

Conclusion

The bidirectional MR study couldn't provide convincing evidence for the causal relationship between genetic liability to PCOS and periodontitis in the Europeans. Triangulating evidence across further observational and genetic-epidemiological studies is necessary.

Dysbiosis From a Microbial and Host Perspective Relative to Oral Health and Disease

The significance of microbiology and immunology with regard to caries and periodontal disease gained substantial clinical or research consideration in the mid 1960's. This enhanced emphasis related to several simple but elegant experiments illustrating the relevance of bacteria to oral infections. Since that point, the understanding of oral diseases has become increasingly sophisticated and many of the original hypotheses related to disease causality have either been abandoned or amplified. The COVID pandemic has reminded us of the importance of history relative to infectious diseases and in the words of Churchill "those who fail to learn from history are condemned to repeat it." This review is designed to present an overview of broad general directions of research over the last 60 years in oral microbiology and immunology, reviewing significant contributions, indicating emerging foci of interest, and proposing future directions based on technical advances and new understandings. Our goal is to review this rich history (standard microbiology and immunology) and point to potential directions in the future (omics) that can lead to a better understanding of disease. Over the years, research scientists have moved from a position of downplaying the role of bacteria in oral disease to one implicating bacteria as true pathogens that cause disease. More recently it has been proposed that bacteria form the ecological first line of defense against "foreign" invaders and also serve to train the immune system as an acquired host defensive stimulus. While early immunological research was focused on immunological exposure as a modulator of disease, the "hygiene hypothesis," and now the "old friends hypothesis" suggest that the immune response could be trained by bacteria for long-term health. Advanced "omics" technologies are currently being used to address changes that occur in the host and the microbiome in oral disease. The "omics" methodologies have shaped the detection of quantifiable biomarkers to define human physiology and pathologies. In summary, this review will emphasize the role that commensals and pathobionts play in their interaction with the immune status of the host, with a prediction that current "omic" technologies will allow researchers to better understand disease in the future.

Impact of systemic factors in shaping the periodontal microbiome

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

Biosensor and Lab-on-a-chip Biomarker-identifying Technologies for Oral and Periodontal Diseases

Periodontitis is a complex multifactorial disease that can lead to destruction of tooth supporting tissues and subsequent tooth loss. The most recent global burden of disease studies highlight that severe periodontitis is one of the most prevalent chronic inflammatory conditions affecting humans. Periodontitis risk is attributed to genetics, host-microbiome and environmental factors. Empirical diagnostic and prognostic systems have yet to be validated in the field of periodontics. Early diagnosis and intervention prevents periodontitis progression in most patients. Increased susceptibility and suboptimal control of modifiable risk factors can result in poor response to therapy, and relapse. The chronic immune-inflammatory response to microbial biofilms at the tooth or dental implant surface is associated with systemic conditions such as cardiovascular disease, diabetes or gastrointestinal diseases. Oral fluid-based biomarkers have demonstrated easy accessibility and potential as diagnostics for oral and systemic diseases, including the identification of SARS-CoV-2 in saliva. Advances in biotechnology have led to innovations in lab-on-a-chip and biosensors to interface with oral-based biomarker assessment. This review highlights new developments in oral biomarker discovery and their validation for clinical application to advance precision oral medicine through improved diagnosis, prognosis and patient stratification. Their potential to improve clinical outcomes of periodontitis and associated chronic conditions will benefit the dental and overall public health.

Current understanding of periodontal disease pathogenesis and targets for host-modulation therapy

Recent advances indicate that periodontitis is driven by reciprocally reinforced interactions between a dysbiotic microbiome and dysregulated inflammation. Inflammation is not only a consequence of dysbiosis but, via mediating tissue dysfunction and damage, fuels further growth of selectively dysbiotic communities of bacteria (inflammophiles), thereby generating a self-sustained feed-forward loop that perpetuates the disease. These considerations provide a strong rationale for developing adjunctive host-modulation therapies for the treatment of periodontitis. Such host-modulation approaches aim to inhibit harmful inflammation and promote its resolution or to interfere directly with downstream effectors of connective tissue and bone destruction. This paper reviews diverse strategies targeted to modulate the host periodontal response and discusses their mechanisms of action, perceived safety, and potential for clinical application.

Inflammasomes as contributors to periodontal disease

A genome‐wide association study of ≈2.5 million markers identified unique biologically informed periodontal complex traits with distinct microbial communities and interleukin‐1β (IL‐1β) levels. Each trait was associated with different single nucleotide polymorphisms. These variants include genes associated with immune responses, microbial colonization, and the epithelial barrier function. The specific set of variants leads to individual biological paths that converge into an overlapping clinical phenotype of periodontal tissue destruction. This concept suggests that periodontal disease is a group of distinct conditions. We identified polymorphisms in inflammasome genes interferon gamma inducible protein 16 (IFI16) and absent in melanoma 2 (AIM2) that were associated with increased severity of periodontal disease. Inflammasomes respond to pathogen or tissue “danger” signals and assemble into multiprotein “machineries” that are essential for the cleavage of proinflammatory mediator IL‐1β into an active form. Thus, understanding how variants of IFI16 and AIM2 contribute to periodontal disease pathogenesis may lead to treatment options that address individual biological variations and precision therapies for oral health.

Th2 cell regulatory and effector molecules single nucleotide polymorphisms and periodontitis

To investigate the association between T helper 2 (Th2) cell regulatory and effector molecules' genetic polymorphisms and periodontitis. Single nucleotide polymorphisms (SNPs) of 11 Th2 cell regulatory or effector molecules genes (CD28, CTLA4, IL4, IL5, IL6, IL9, IL10, IL13, IL4R, GATA3, STAT6, and rs1537415; total 130 SNPs) were studied in Chinese nonsmokers (163 periodontitis-free controls, 141 periodontitis patients) using Sequenom iPlex assays. SNPs potentially associated with periodontitis (adjusted allelic P < 0.1) in this cross-sectional study were further investigated via meta-analysis. Allele G of rs4553808 in promoter of CTLA4 was more frequently detected in periodontitis than controls (P < 0.005), but did not remain significant after age and gender adjustment. Haplotype (GTT) in a block of three CTLA4 SNPs (rs4553808, rs16840252, rs5742909) was significantly associated with periodontitis. Meta-analysis of SNPs identified indicated allele T of CTLA4 rs5742909 (3 studies; 461 control, 369 periodontitis) and allele G of IL6 rs1800796 (18 studies; 2760 control, 2442 periodontitis) were significantly associated with periodontitis (OR = 1.44 and OR = 1.30, respectively). Within limitations of this study, a haplotype of CTLA4 concerning Th2 cell regulation, may be associated with periodontitis in Chinese nonsmokers followed. Meta-analysis indicated rs5742909 of CTLA4 and rs1800796 of IL6 appeared significantly associated with periodontitis.

The role of inflammation and genetics in periodontal disease

Periodontitis is a complex disease: (a) various causative factors play a role simultaneously and interact with each other; and (b) the disease is episodic in nature, and bursts of disease activity can be recognized, ie, the disease develops and cycles in a nonlinear fashion. We recognize that various causative factors determine the immune blueprint and, consequently, the immune fitness of a subject. Normally, the host lives in a state of homeostasis or symbiosis with the oral microbiome; however, disturbances in homeostatic balance can occur, because of an aberrant host response (inherited and/or acquired during life). This imbalance results from hyper- or hyporesponsiveness and/or lack of sufficient resolution of inflammation, which in turn is responsible for much of the disease destruction seen in periodontitis. The control of this destruction by anti-inflammatory processes and proresolution processes limits the destruction to the tissues surrounding the teeth. The local inflammatory processes can also become systemic, which in turn affect organs such as the heart. Gingival inflammation also elicits changes in the ecology of the subgingival environment providing optimal conditions for the outgrowth of gram-negative, anaerobic species, which become pathobionts and can propagate periodontal inflammation and can further negatively impact immune fitness. The factors that determine immune fitness are often the same factors that determine the response to the resident biofilm, and are clustered as follows: (a) genetic and epigenetic factors; (b) lifestyle factors, such as smoking, diet, and psychosocial conditions; (c) comorbidities, such as diabetes; and (d) local and dental factors, as well as randomly determined factors (stochasticity). Of critical importance are the pathobionts in a dysbiotic biofilm that drive the viscious cycle. Focusing on genetic factors, currently variants in at least 65 genes have been suggested as being associated with periodontitis based on genome-wide association studies and candidate gene case control studies. These studies have found pleiotropy between periodontitis and cardiovascular diseases. Most of these studies point to potential pathways in the pathogenesis of periodontal disease. Also, most contribute to a small portion of the total risk profile of periodontitis, often limited to specific racial and ethnic groups. To date, 4 genetic loci are shared between atherosclerotic cardiovascular diseases and periodontitis, ie, CDKN2B-AS1(ANRIL), a conserved noncoding element within CAMTA1 upstream of VAMP3, PLG, and a haplotype block at the VAMP8 locus. The shared genes suggest that periodontitis is not causally related to atherosclerotic diseases, but rather both conditions are sequelae of similar (the same?) aberrant inflammatory pathways. In addition to variations in genomic sequences, epigenetic modifications of DNA can affect the genetic blueprint of the host responses. This emerging field will yield new valuable information about susceptibility to periodontitis and subsequent persisting inflammatory reactions in periodontitis. Further studies are required to verify and expand our knowledge base before final cause and effect conclusions about the role of inflammation and genetic factors in periodontitis can be made.

Biologically informed stratification of periodontal disease holds the key to achieving precision oral health

Medicine and dentistry need to treat the individual not the "average patient." This personalized or precision approach to health care involves correctly diagnosing and properly classifying people to effectively customize prevention, diagnosis, and treatment. This is not a trivial undertaking. Achieving precision health requires making sense of big data, both at the population level and at the molecular level. The latter can include genetic, epigenetic, transcriptomic, proteomic, metabolomic data, and microbiome data. This biological information can augment established clinical measurements and supplement data on socioeconomic status, lifestyle, behaviors, and environmental conditions. Here, the central thesis is that, with sufficient data and appropriate methods, it is possible to segregate symptom-based and phenotypically based categories of patients into clinically and biologically similar groups. These groups are likely to have different clinical trajectories and benefit from different treatments. Additionally, such groups are optimal for investigations seeking to unveil the genomic basis of periodontal disease susceptibility. Analysis of these complex data to produce actionable and replicable health and disease categories requires appropriately sophisticated bioinformatics approaches and thorough validation in diverse patient samples and populations. Successful research programs will need to consider both population-level and well-controlled deep phenotyping approaches. Biologically informed stratification of periodontal disease is both feasible and desirable. Ultimately, this approach can accelerate the development of precision health through improvements in research and clinical applications.

Microbial and Host Factors That Affect Bacterial Invasion of the Gingiva

Periodontitis is a chronic inflammation of the periodontium caused by the loss of homeostasis between subgingival biofilms and susceptible hosts. Bacterial invasion into the gingival tissue and persistent infection are major events that lead to chronic inflammation. The intratissue bacterial communities are as complex as the subgingival biofilms and can also form biofilm-like structures, which will serve as a reservoir for local and systemic infections. The epithelium forms physical, chemical, and immunological barriers against invading microbes. Nevertheless, many bacterial species can invade the gingival epithelium through transcellular and paracellular pathways. In addition, both genetic and environmental factors of the hosts can affect epithelial barrier functions and thus bacterial invasion of the gingiva. In this review, current evidence for the bacterial invasion of the gingival tissue in periodontitis has been summarized, and the microbial and host factors that determine bacterial invasion of the gingiva have been reviewed.

Regulation of the Ysh1 endonuclease of the mRNA cleavage/polyadenylation complex by ubiquitin-mediated degradation

Mutation of the essential yeast protein Ipa1 has previously been demonstrated to cause defects in pre-mRNA 3' end processing and growth, but the mechanism underlying these defects was not clear. In this study, we show that the ipa1-1 mutation causes a striking depletion of Ysh1, the evolutionarily conserved endonuclease subunit of the 19-subunit mRNA Cleavage/Polyadenylation (C/P) complex, but does not decrease other C/P subunits. YSH1 overexpression rescues both the growth and 3' end processing defects of the ipa1-1 mutant. YSH1 mRNA level is unchanged in ipa1-1 cells, and proteasome inactivation prevents Ysh1 loss and causes accumulation of ubiquitinated Ysh1. Ysh1 ubiquitination is mediated by the Ubc4 ubiquitin-conjugating enzyme and Mpe1, which in addition to its function in C/P, is also a RING ubiquitin ligase. In summary, Ipa1 affects mRNA processing by controlling the availability of the C/P endonuclease and may represent a regulatory mechanism that could be rapidly deployed to facilitate reprogramming of cellular responses.