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.

Advances in periodontal biomarkers.

Due to technologic advancements, periodontology has witnessed a boost in biomarker research over the past three decades. Indeed, with the aid of omics, our understanding of the healthy periodontium, pathogenesis of periodontal diseases, and healing after periodontal treatment has improved significantly. Yet, the traditional methods, periodontal probing and radiographies, remain the most common methods to diagnose periodontal disease and monitor treatment. Although these approaches can produce reliable diagnostic outcomes, they generally detect disease only after significant tissue degradation thus making treatment outcome highly uncertain. Accordingly, laboratories worldwide have collaborated with clinicians to design accurate, rapid and cost-effective biomarkers for periodontal disease diagnosis. Despite these efforts, biomarkers that can be widely used in early disease diagnosis and for treatment outcome prediction are far from daily use. The aim of this chapter is to give a general overview on periodontal health and diseases, and review recent advancements in periodontal biomarker research. A second aim will discuss the strengths and limitations of translating periodontal biomarker research to clinical practice. Genetic biomarkers of periodontitis are not discussed as the available confirmatory data is scarce.

Periodontal disease and risk of Alzheimer's disease: A two-sample Mendelian randomization.

BACKGROUND: Evidence from observational studies and clinical trials suggests an association between periodontal disease and Alzheimer's disease (AD). However, the causal relationship between periodontal disease and AD remains to be determined. METHODS: We obtained periodontal disease data from the FinnGen database and two sets of AD data from the IEU consortium and PGC databases. Subsequently, we conducted a two-sample Mendelian randomization (MR) analysis to investigate the causal relationship between periodontal disease and AD. RESULTS: The results of the random-effects IVW analysis revealed no evidence of a genetic causal relationship between periodontal disease and AD, regardless of whether the AD data from the IEU consortium or the AD data from the PGC database were utilized. No heterogeneity, multiple effects of levels, or outliers were observed in this study. CONCLUSIONS: Our findings indicate that there is no causal relationship between periodontal disease and AD at the genetic level.

Investigation of periodontal disease development and Porphyromonas gulae FimA genotype distribution in small dogs.

In dogs, Porphyromonas gulae is a major periodontal pathogen with 41-kDa proteins polymerizing to form a filamentous structure called fimbriae or pili, termed FimA. FimA is classified into three genotypes: A, B, and C, and there are combinations of types A, B, C, A/B, A/C, B/C, and A/B/C. Periodontal disease is the most common oral disease in small dogs, but the periodontal disease status and P. gulae colonization at each dog age and breed remain unclear. In this study, we stratified 665 small dogs and analyzed the periodontal status and distribution of P. gulae with each FimA genotype. Dogs with periodontal disease and FimA genotype tended to increase with age. The dogs with at least one FimA genotype had significantly more severe periodontal disease compared with P. gulae-negative dogs (P < 0.01). Additionally, periodontal status was significantly associated with specific FimA genotype distribution in Toy Poodles and Chihuahuas (P < 0.05), whereas there was no such association in Dachshunds. These results suggest that the onset of periodontal disease and P. gulae colonization are related and progress with age. The relationship between periodontal disease and FimA genotype may differ depending on the dog breeds.

Gene sequencing applications to combat oral-cavity related disorders: a systematic review with meta-analysis.

Gene sequencing (GS) has numerous applications in combatting oral-cavity related disorders, including identifying genetic risk factors for diseases, developing targeted therapies, and improving diagnostic methods. It can help identify specific genetic mutations or variations that increase the risk of developing oral-cavity related disorders, such as oral cancer, periodontal disease, and cleft lip and palate. By the means of the following investigation, our primary objective was to assess the impact of GS technique in diagnosing and potentially treating diseases of the oral cavity by the means of a systematic review and meta-analysis. We commenced by defining the terms "gene sequencing," "oral cavity," and "disorders" as the important elements in our investigation's subject. Next, relevant databases like PubMed, Scopus, Embase, Web of Science, and Google Scholar were searched using keywords and synonyms for each concept, such as "genomic sequencing," "DNA sequencing," "oral health," "oral diseases," "dental caries," "periodontal disease," "oral cancer," and "salivary gland disorders." We combined several search terms, such as "gene sequencing AND oral disorders AND periodontal disease" or "oral cancer OR genomic sequencing," to further hone your search results using Boolean operators like "AND" and "OR." The oral cavity analysis obtained by CS in the selected articles revealed that most of the disorders were, in fact, a direct causal event influenced by the oral microbiome. Moreover, each sampled oral cavity evidenced a different microbial community, which predicted the precipitation of benign as well as malignant conditions, though not on a definitive basis. In the last ten years, genomic sequencing had advanced remarkably as majority of our selected studies observed, making it possible to diagnose and treat a variety of oral and maxillofacial disorders, including cancer. It was also used to ascertain a person's genetic make-up as well as to spot numerous genetic abnormalities that can predispose individuals to diseases. Understanding the different sequencing techniques and the resulting genetic anomalies may help with their clinical application and lead to an improvement in illness diagnosis and prognosis as a whole in the field of dentistry.

Periodontal disease in patients with WHIM syndrome.

AIM: WHIM (warts, hypogammaglobulinaemia, infections and myelokathexis) syndrome is a rare combined primary immunodeficiency disease caused by gain-of-function (GOF) mutations in the chemokine receptor CXCR4 and includes severe neutropenia as a common feature. Neutropenia is a known risk factor for periodontitis; however, a detailed periodontal evaluation of a WHIM syndrome cohort is lacking. This study aimed to establish the evidence base for the periodontal status of patients with WHIM syndrome. MATERIALS AND METHODS: Twenty-two adult WHIM syndrome patients and 22 age- and gender-matched healthy volunteers (HVs) were evaluated through a comprehensive medical and periodontal examination. A mouse model of WHIM syndrome was assessed for susceptibility to naturally progressing or inducible periodontitis. RESULTS: Fourteen patients with WHIM syndrome (63.6%) and one HV (4.5%) were diagnosed with Stage III/IV periodontitis. No WHIM patient presented with the early onset, dramatic clinical phenotypes typically associated with genetic forms of neutropenia. Age, but not the specific CXCR4 mutation or absolute neutrophil count, was associated with periodontitis severity in the WHIM cohort. Mice with a Cxcr4 GOF mutation did not exhibit increased alveolar bone loss in spontaneous or ligature-induced periodontitis. CONCLUSIONS: Overall, WHIM syndrome patients presented with an increased severity of periodontitis despite past and ongoing neutrophil mobilization treatments. GOF mutations in CXCR4 may be a risk factor for periodontitis in humans.

Polymorphism of salivary proteins and risk of periodontal diseases: A systematic review and meta-analysis of clinical studies.

OBJECTIVES: The present systematic review and meta-analysis aimed to assess the association between salivary protein polymorphisms and the risk of periodontal diseases (PD). DATA: The review incorporated cross-sectional, case-control, retrospective/prospective cohort, and randomized controlled trials assessing the influence of salivary protein polymorphisms on the risk of PD development were included in this review. SOURCES: A thorough literature search was conducted across electronic databases, namely PubMed, Scopus, Embase, and Web of Science, without any restrictions on publication language and year. STUDY SELECTION: A total of 168 studies were identified, of which 19 were eligible for inclusion. The risk of bias (RoB) assessment of the included studies was conducted at the methodological level. RESULTS: A total of 16 studies were included. Polymorphism in the gene encoding TNF-α was found to be protective against gingivitis, while those encoding IL-1α and IL-1ß were associated with developing gingivitis. Of the 42 proteins investigated, various gene polymorphisms were identified as protective or risk factors for periodontitis. Protective genes include CFH, DNMT1, OPRM1, and TLR9. Conversely, certain salivary protein genes (e.g., CRP, ERN1, FAM5C, IDH2, LTA, TET2, MPA, NLRP3, TLR4) were associated with periodontitis risk. Notably, IL6, MMP9, and MUC7 genes showed no association with PD, while MMP13 was linked to early implant loss. Overall, the meta-analysis found a statistically significant association between salivary proteins' polymorphisms and risk of PD. CONCLUSIONS: Salivary protein polymorphisms significantly influence PD, revealing protective and risk-associated genotypes. Despite limitations, findings suggest therapeutic targets, emphasizing the complex genetics-periodontal health interplay. CLINICAL SIGNIFICANCE: This study unveils salivary protein polymorphisms as pivotal factors in PD. Protective genes including CFH and TLR9, and risk-associated genes including CRP and TLR4, indicate a genetic basis for PD susceptibility.

Molecular detection of oral Trichomonas tenax in periodontal disease patients by polymerase chain reaction -based 18S rRNA gene.

Trichomonas tenax, an oral flagellated protozoon found in humans, potentially associated with the inflammation of periodontal tissues and decreased immunity that causes the tissue damage and tooth loss from chronic infection. Currently, there is a lack of data regarding the prevalence of T. tenax infection in Thailand. Therefore, this study aimed to measure prevalence of T. tenax in periodontal disease patients by using polymerase chain reaction (PCR) to amplify the 18S ribosomal RNA (18S rRNA) gene and to determine the factors associated with the presence of this protozoan. A cross-sectional descriptive study was conducted among 230 patients with periodontal disease, who visited the oral health center of Suranaree University of Technology Hospital, Thailand from 2021 to 2022. Dental plaque specimens were collected and examined to identify the presence of T. tenax using the PCR-based 18S rRNA gene. The occurrence of factors associated with T. tenax infection was analyzed by the chi-square test and binary logistic regression. The prevalence of T. tenax infection was 13.48% (31/230), in patients, including 96.77% (30/31) and 3.23% (1/31) in periodontitis and gingivitis patients, respectively. The presence of T. tenax was associated with periodontal disease (p<0.001) and the Periodontal Screening and Record (PSR) index (p=0.001). The significant risk factors for T. tenax infection were periodontitis (ORadj=239.89, 95% CI=23.801-2417.746), no-underlying disease (ORadj=0.31, 95% CI=0.099-0.942), and male sex (ORadj=0.25, 95% CI=0.062-0.981). Dentists should be concerned about this oral protozoan in periodontitis patients. Furthermore, epidemiologic studies of T. tenax are still needed to investigate the mechanism of pathogenesis from T. tenax infection.

Oral Spirochete Treponema denticola Intraoral Infection Reveals Unique miR-133a, miR-486, miR-126-3p, miR-126-5p miRNA Expression Kinetics during Periodontitis.

miRNAs are major regulators of eukaryotic gene expression and host immunity, and play an important role in the inflammation-mediated pathways in periodontal disease (PD) pathogenesis. Expanding our previous observation with the global miRNA profiling using partial human mouth microbes, and lack of in vivo studies involving oral spirochete Treponema denticola-induced miRNAs, this study was designed to delineate the global miRNA expression kinetics during progression of periodontitis in mice infected with T. denticola by using NanoString nCounter® miRNA panels. All of the T. denticola-infected male and female mice at 8 and 16 weeks demonstrated bacterial colonization (100%) on the gingival surface, and an increase in alveolar bone resorption (p < 0.0001). A total of 70 miRNAs with at least 1.0-fold differential expression/regulation (DE) (26 upregulated and 44 downregulated) were identified. nCounter miRNA expression profiling identified 13 upregulated miRNAs (e.g., miR-133a, miR-378) and 25 downregulated miRNAs (e.g., miR-375, miR-34b-5p) in T. denticola-infected mouse mandibles during 8 weeks of infection, whereas 13 upregulated miRNAs (e.g., miR-486, miR-126-5p) and 19 downregulated miRNAs (miR-2135, miR-142-3p) were observed during 16 weeks of infection. One miRNA (miR-126-5p) showed significant difference between 8 and 16 weeks of infection. Interestingly, miR-126-5p has been presented as a potential biomarker in patients with periodontitis and coronary artery disease. Among the upregulated miRNAs, miR-486, miR-126-3p, miR-126-5p, miR-378a-3p, miR-22-3p, miR-151a-3p, miR-423-5p, and miR-221 were reported in human gingival plaques and saliva samples from periodontitis and with diabetes. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed various functional pathways of DE miRNAs, such as bacterial invasion of epithelial cells, Ras signaling, Fc gamma R-mediated phagocytosis, osteoclast differentiation, adherens signaling, and ubiquitin mediated proteolysis. This is the first study of DE miRNAs in mouse mandibles at different time-points of T. denticola infection; the combination of three specific miRNAs, miR-486, miR-126-3p, and miR-126-5p, may serve as an invasive biomarker of T. denticola in PD. These miRNAs may have a significant role in PD pathogenesis, and this research establishes a link between miRNA, periodontitis, and systemic diseases.

Epigenome-wide association study using peripheral blood leukocytes identifies genomic regions associated with periodontal disease and edentulism in the Atherosclerosis Risk in Communities study.

AIM: To investigate individual susceptibility to periodontitis by conducting an epigenome-wide association study using peripheral blood. MATERIALS AND METHODS: We included 1077 African American and 457 European American participants of the Atherosclerosis Risk in Communities (ARIC) study who had completed a dental examination or reported being edentulous at Visit 4 and had available data on DNA methylation from Visit 2 or 3. DNA methylation levels were compared by periodontal disease severity and edentulism through discovery analyses and subsequent testing of individual CpGs. RESULTS: Our discovery analysis replicated findings from a previous study reporting a region in gene ZFP57 (6p22.1) that was significantly hypomethylated in severe periodontal disease compared with no/mild periodontal disease in European American participants. Higher methylation levels in a separate region in an unknown gene (located in Chr10: 743,992-744,958) was associated with significantly higher odds of edentulism compared with no/mild periodontal disease in African American participants. In subsequent CpG testing, four CpGs in a region previously associated with periodontitis located within HOXA4 were significantly hypermethylated in severe periodontal disease compared with no/mild periodontal disease in African American participants (odds ratio per 1 SD increase in methylation level: cg11015251: 1.28 (1.02, 1.61); cg14359292: 1.24 (1.01, 1.54); cg07317062: 1.30 (1.05, 1.61); cg08657492: 1.25 (1.01, 1.55)). CONCLUSIONS: Our study highlights epigenetic variations in ZPF57 and HOXA4 that are significantly and reproducibly associated with periodontitis. Future studies should evaluate gene regulatory mechanisms in the candidate regions of these loci.

Hemin availability induces coordinated DNA methylation and gene expression changes in Porphyromonas gingivalis.

Periodontal disease is a chronic inflammatory disease in which the oral pathogen Porphyromonas gingivalis plays an important role. Porphyromonas gingivalis expresses virulence determinants in response to higher hemin concentrations, but the underlying regulatory processes remain unclear. Bacterial DNA methylation has the potential to fulfil this mechanistic role. We characterized the methylome of P. gingivalis, and compared its variation to transcriptome changes in response to hemin availability. Porphyromonas gingivalis W50 was grown in chemostat continuous culture with excess or limited hemin, prior to whole-methylome and transcriptome profiling using Nanopore and Illumina RNA-Seq. DNA methylation was quantified for Dam/Dcm motifs and all-context N6-methyladenine (6mA) and 5-methylcytosine (5mC). Of all 1,992 genes analyzed, 161 and 268 were respectively over- and under-expressed with excess hemin. Notably, we detected differential DNA methylation signatures for the Dam "GATC" motif and both all-context 6mA and 5mC in response to hemin availability. Joint analyses identified a subset of coordinated changes in gene expression, 6mA, and 5mC methylation that target genes involved in lactate utilization and ABC transporters. The results identify altered methylation and expression responses to hemin availability in P. gingivalis, with insights into mechanisms regulating its virulence in periodontal disease. IMPORTANCE DNA methylation has important roles in bacteria, including in the regulation of transcription. Porphyromonas gingivalis, an oral pathogen in periodontitis, exhibits well-established gene expression changes in response to hemin availability. However, the regulatory processes underlying these effects remain unknown. We profiled the novel P. gingivalis epigenome, and assessed epigenetic and transcriptome variation under limited and excess hemin conditions. As expected, multiple gene expression changes were detected in response to limited and excess hemin that reflect health and disease, respectively. Notably, we also detected differential DNA methylation signatures for the Dam "GATC" motif and both all-context 6mA and 5mC in response to hemin. Joint analyses identified coordinated changes in gene expression, 6mA, and 5mC methylation that target genes involved in lactate utilization and ABC transporters. The results identify novel regulatory processes underlying the mechanism of hemin regulated gene expression in P. gingivalis, with phenotypic impacts on its virulence in periodontal disease.

The Potential Role of Epigenetic Modifications on Different Facets in the Periodontal Pathogenesis.

Periodontitis is a chronic inflammatory disease that affects the supporting structures of teeth. In the literature, the association between the pathogenicity of bacteria and environmental factors in this regard have been extensively examined. In the present study, we will shed light on the potential role that epigenetic change can play on different facets of its process, more particularly the modifications concerning the genes involved in inflammation, defense, and immune systems. Since the 1960s, the role of genetic variants in the onset and severity of periodontal disease has been widely demonstrated. These make some people more susceptible to developing it than others. It has been documented that the wide variation in its frequency for various racial and ethnic populations is due primarily to the complex interplay among genetic factors with those affecting the environment and the demography. In molecular biology, epigenetic modifications are defined as any change in the promoter for the CpG islands, in the structure of the histone protein, as well as post-translational regulation by microRNAs (miRNAs), being known to contribute to the alteration in gene expression for complex multifactorial diseases such as periodontitis. The key role of epigenetic modification is to understand the mechanism involved in the gene-environment interaction, and the development of periodontitis is now the subject of more and more studies that attempt to identify which factors are stimulating it, but also affect the reduced response to therapy.

Retrospective Case-Control Study Genes Related to Bone Metabolism That Justify the Condition of Periodontal Disease and Failure of Dental Implants in Patients with down Syndrome.

Down syndrome patients show success rates in dental implants much lower than those observed in the general population. This retrospective case-control study aimed to identify possible genes that are related to the regulation of inflammatory responses and bone metabolism related to periimplantitis and implant loss, as well as genes related to bone quality. This process involved using the functional analysis of the gene expression software Transcriptome Analysis Console (TAC version 4.0 Applied BiosystemsTM, Thermo Fisher Scientific, Waltham, MA, USA) and a search for possible candidate genes involved. The focus was placed on the 93 genes related to periodontitis, periimplantitis, bone loss, implant loss, and genes related to bone quality and regulators underlying the establishment and maintenance of osseointegration. Five genes showed statistically significant results (p < 0.05) in our comparison. Four of them, IL1B (p = 0.023), IL1RN (p = 0.048), BGLAP (p = 0.0372) and PTK2 (p = 0.0075) were down-regulated in the periodontal disease and implant rejection group, and only one was overexpressed: FOXO1A (p = 0.0552). The genes with statistically significant alterations described in this article determine that the group of Down syndrome patients with periodontal disease and implant failure is a group of patients genetically susceptible to suffering from both conditions together.

Periodontal Disease Pathogens, Pathogenesis, and Therapeutics: The CRISPR-Cas Effect.

Periodontal disease (PD) is an immune-inflammatory disease affecting the supporting structures of the teeth, which results in progressive destruction of the hard and soft tissues surrounding teeth, ultimately resulting in tooth loss. The primary etiological factor for this disease is the presence of pathogenic microorganisms. Pathogenic bacteria face antagonistic conditions and foreign DNA components during the infection stage and depend on defense mechanisms such as clustered regularly interspaced short palindromic repeats (CRISPR)-Cas to counter them. Virulence genes regulated by the CRISPR-Cas system are often expressed by bacteria as part of the stress response to the presence of stress conditions and foreign elements. There is ever-growing evidence regarding the role of CRISPR-Cas in virulence of periodontal pathogens. The same CRISPR-Cas system may also be targeted to reduce bacterial virulence and it may also be utilized to develop diagnostic and therapeutic strategies for prevention and control of PD progression. This review article describes the CRISPR-Cas systems in the periodontal dysbiotic microbial communities, their role in the virulence of periodontal pathogens, and their potential role in understanding the pathogenesis of periodontitis and treatment of PD.

Pim-2 regulates bone resorptive activity of osteoclasts via V-ATPase a3 isoform expression in periodontal disease.

Cytoplasmic serine/threonine Pim kinases have emerged as important modulators of immune regulation and oncology. However, their regulatory roles in bone remodeling remain obscure. Here, we aimed to determine the roles of Pim kinases in periodontal disease (PD), focusing on the regulation of osteoclastogenesis and bone resorptive activity. We investigated Pim kinases expression in PD by analyzing data from the online Gene Expression Omnibus database and using ligature-induced periodontitis mouse model. The expression of Pim kinases during receptor activator of nuclear factor kB ligand (RANKL)-induced osteoclastogenesis was assessed in mouse bone marrow-derived macrophages (BMMs) using reverse transcription polymerase chain reaction. Osteoclast differentiation and bone resorption activity were respectively verified by tartrate-resistant acid phosphatase staining and dentin disc-based bone resorption assays. We silenced and overexpressed Pim-2 using small interfering RNA (siRNA) and retroviral vector, respectively, to investigate the molecular mechanisms underlying Pim-2 regulation in RANKL-induced osteoclastogenesis and bone resorption activity. Upregulated expression of Pim-2 was observed in both patients with PD and periodontitis-affected mouse gingival tissues. siRNA-mediated silencing of Pim-2 in BMMs diminished RANKL-induced resorptive activity without affecting osteoclastogenesis. Moreover, RANKL-triggered stimulation of a3 isoform, which is a subunit of vacuolar-type ATPase, was selectively attenuated in BMMs on silencing Pim-2. The overexpression of Pim-2 with a retroviral vector stimulated the a3 subunit, thus inducing bone resorption activity. Taken together, these results suggest that Pim-2 acts as a major modulator of osteoclastic activity by regulating a3 isoform expression in PD.

Genomic Medicine in Periodontal Disease: Old Issue, New Insights.

Genetic variability is the main cause of phenotypic variation. Some variants may be associated with several diseases and can be used as risk biomarkers, identifying animals with higher susceptibility to develop the pathology. Genomic medicine uses this genetic information for risk calculation, clinical diagnosis and prognosis, allowing the implementation of more effective preventive strategies and/or personalized therapies. Periodontal disease (PD) is the inflammation of the periodontium induced mainly by bacterial plaque and is the leading cause of tooth loss. Microbial factors are responsible for the PD initiation; however, several studies support the genetic influence on the PD progression. The main purpose of the present publication is to highlight the main steps involved in the genomic medicine applied to veterinary patients, describing the flowchart from the characterization of the genetic variants to the identification of potential associations with specific clinical data. After investigating which genes might potentially be implicated in canine PD, the RANK gene, involved in the regulation of osteoclastogenesis, was selected to illustrate this approach. A case-control study was performed using DNA samples from a population of 90 dogs - 50 being healthy and 40 with PD. This analysis allowed for the discovery of four new intronic variations that were banked in GenBank (g.85A>G, g.151G>T, g.268A>G and g.492T>C). The results of this study are not intended to be applied exclusively to PD. On the contrary, this genetic information is intended to be used by other researchers as a foundation for the development of multiple applications in the veterinary clinical field.

MicroRNAs: Harbingers and shapers of periodontal inflammation.

Periodontal disease is an inflammatory reaction of the periodontal tissues to oral pathogens. In the present review we discuss the intricate effects of a regulatory network of gene expression modulators, microRNAs (miRNAs), as they affect periodontal morphology, function and gene expression during periodontal disease. These miRNAs are small RNAs involved in RNA silencing and post-transcriptional regulation and affect all stages of periodontal disease, from the earliest signs of gingivitis to the regulation of periodontal homeostasis and immunity and to the involvement in periodontal tissue destruction. MiRNAs coordinate periodontal disease progression not only directly but also through long non-coding RNAs (lncRNAs), which have been demonstrated to act as endogenous sponges or decoys that regulate the expression and function of miRNAs, and which in turn suppress the targeting of mRNAs involved in the inflammatory response, cell proliferation, migration and differentiation. While the integrity of miRNA function is essential for periodontal health and immunity, miRNA sequence variations (genetic polymorphisms) contribute toward an enhanced risk for periodontal disease progression and severity. Several polymorphisms in miRNA genes have been linked to an increased risk of periodontitis, and among those, miR-146a, miR-196, and miR-499 polymorphisms have been identified as risk factors for periodontal disease. The role of miRNAs in periodontal disease progression is not limited to the host tissues but also extends to the viruses that reside in periodontal lesions, such as herpesviruses (human herpesvirus, HHV). In advanced periodontal lesions, HHV infections result in the release of cytokines from periodontal tissues and impair antibacterial immune mechanisms that promote bacterial overgrowth. In turn, controlling the exacerbation of periodontal disease by minimizing the effect of periodontal HHV in periodontal lesions may provide novel avenues for therapeutic intervention. In summary, this review highlights multiple levels of miRNA-mediated control of periodontal disease progression, (i) through their role in periodontal inflammation and the dysregulation of homeostasis, (ii) as a regulatory target of lncRNAs, (iii) by contributing toward periodontal disease susceptibility through miRNA polymorphism, and (iv) as periodontal microflora modulators via viral miRNAs.

Wnt signalling in oral and maxillofacial diseases.

Wnts include more than 19 types of secreted glycoproteins that are involved in a wide range of pathological processes in oral and maxillofacial diseases. The transmission of Wnt signalling from the extracellular matrix into the nucleus includes canonical pathways and noncanonical pathways, which play an important role in tooth development, alveolar bone regeneration, and related diseases. In recent years, with the in-depth study of Wnt signalling in oral and maxillofacial-related diseases, many new conclusions and perspectives have been reached, and there are also some controversies. This article aims to summarise the roles of Wnt signalling in various oral diseases, including periodontitis, dental pulp disease, jaw disease, cleft palate, and abnormal tooth development, to provide researchers with a better and more comprehensive understanding of Wnts in oral and maxillofacial diseases.

Candidate loci shared among periodontal disease, diabetes and bone density.

Introduction: While periodontal disease (PD) has been associated with type 2 diabetes (T2D) and osteoporosis, the underlying genetic mechanisms for these associations remain largely unknown. The aim of this study is to apply cross-trait genetic analyses to investigate the potentially shared biology among PD, T2D, and bone mineral density (BMD) by assessing pairwise genetic correlations and searching for shared polymorphisms. Methods: We applied cross-trait genetic analyses leveraging genome-wide association study (GWAS) summary statistics for: Periodontitis/loose teeth from the UKBB/GLIDE consortium (PerioLT, N=506594), T2D from the DIAGRAM consortium (Neff=228825), and BMD from the GEFOS consortium (N=426824). Among all three, pair-wise genetic correlations were estimated with linkage disequilibrium (LD) score regression. Multi-trait meta-analysis of GWAS (MTAG) and colocalization analyses were performed to discover shared genome-wide significant variants (pMTAG <5x10-8). For replication, we conducted independent genetic analyses in the Women's Genome Health Study (WGHS), a prospective cohort study of middle-aged women of whom 14711 provided self-reported periodontal disease diagnosis, oral health measures, and periodontal risk factor data including incident T2D. Results: Significant genetic correlations were identified between PerioLT/T2D (Rg=0.23; SE=0.04; p=7.4e-09) and T2D/BMD (Rg=0.09; SE=0.02; p=9.8e-06). Twenty-one independent pleiotropic variants were identified via MTAG (pMTAG<5x10-8 across all traits). Of these variants, genetic signals for PerioLT and T2D colocalized at one candidate variant (rs17522122; ProbH4 = 0.58), a 3'UTR variant of AKAP6. Colocalization between T2D/BMD and the original PerioLT GWAS p-values suggested 14 additional loci. In the independent WGHS sample, which includes responses to a validated oral health questionnaire for PD surveillance, the primary shared candidate (rs17522122) was associated with less frequent dental flossing [OR(95%CI)= 0.92 (0.87-0.98), p=0.007], a response that is correlated with worse PD status. Moreover, 4 additional candidate variants were indirectly supported by associations with less frequent dental flossing [rs75933965, 1.17(1.04-1.31), p=0.008], less frequent dental visits [rs77464186, 0.82(0.75-0.91), p=0.0002], less frequent dental prophylaxis [rs67111375, 0.91(0.83-0.99), p=0.03; rs77464186, 0.80(0.72-0.89), p=3.8e-05], or having bone loss around teeth [rs8047395, 1.09(1.03-1.15), p=0.005]. Discussion: This integrative approach identified one colocalized locus and 14 additional candidate loci that are shared between T2D and PD/oral health by comparing effects across PD, T2D and BMD. Future research is needed to independently validate our findings.