Gm (23) allotypes and Fcgamma receptor genotypes as risk factors for various forms of periodontitis

The Genetic Aspects of Periodontitis Pathogenesis and the Regenerative Properties of Stem Cells

Periodontitis (PD) is a prevalent and chronic inflammatory disease with a complex pathogenesis, and it is associated with the presence of specific pathogens, such as Porphyromonas gingivalis. Dysbiosis and dysregulated immune responses ultimately lead to chronic inflammation as well as tooth and alveolar bone loss. Multiple studies have demonstrated that genetic polymorphisms may increase the susceptibility to PD. Furthermore, gene expression is modulated by various epigenetic mechanisms, such as DNA methylation, histone modifications, or the activity of non-coding RNA. These processes can also be induced by PD-associated pathogens. In this review, we try to summarize the genetic processes that are implicated in the pathogenesis of PD. Furthermore, we discuss the use of these mechanisms in diagnosis and therapeutic purposes. Importantly, novel treatment methods that could promote tissue regeneration are greatly needed in PD. In this paper, we also demonstrate current evidence on the potential use of stem cells and extracellular vesicles to stimulate tissue regeneration and suppress inflammation. The understanding of the molecular mechanisms involved in the pathogenesis of PD, as well as the impact of PD-associated bacteria and stem cells in these processes, may enhance future research and ultimately improve long-term treatment outcomes.

Functional consequences of allotypic polymorphisms in human immunoglobulin G subclasses

Heritable polymorphisms within the human IgG locus, collectively termed allotypes, have often been linked by statistical associations, but rarely mechanistically, to a wide range of disease states. One potential explanation for these associations is that IgG allotype alters host cell receptors' affinity for IgG, dampening or enhancing an immune response depending on the nature of the change and the receptors. In this work, a panel of allotypic antibody variants were evaluated using multiplexed, label-free biophysical methods and cell-based functional assays to determine what effect, if any, human IgG polymorphisms have on antibody function. While we observed several differences in FcγR affinity among allotypes, there was little evidence of dramatically altered FcγR-based effector function or antigen recognition activity associated with this aspect of genetic variability.

Polymorphic Regions in Fc Gamma Receptor and Tumor Necrosis Factor-α Genes and Susceptibility to Chronic Periodontitis in a Cohort From South India

BACKGROUND

Polymorphisms in the immunoglobulin G Fc receptor II (FcGR) and tumor necrosis factor-α (TNFA) genes are known to influence pathogenesis and severity of several inflammatory conditions. Association of FcGR and TNFA gene polymorphisms with chronic periodontitis (CP) susceptibility has been found to be diverse among different ethnic populations. Objectives of the present study are to determine association of functional single nucleotide polymorphisms (SNPs) in FcGR and TNF-α genes with CP susceptibility in a cohort from South India.

METHODS

Polymorphisms of: 1) FCGR2A 131His/Arg (rs1801274); 2) FCGR2B 232Ile/Thr (rs1050501); 3) TNFA -1031T/C (rs1799964); and 4) TNFA -863C/A (rs1800630) were analyzed among patients with healthy gingiva (n = 176) and patients with CP (n = 177). Genotyping was performed using allele-specific real-time polymerase chain reaction assay. Association between CP and SNPs was examined by multivariable logistic regression analysis with adjustment for: 1) age; 2) sex; and 3) oral hygiene index (OHI). Epistatic interaction between FcGR polymorphisms and interleukin 1B (IL1B) +3954C/T (rs1143634) was assessed using multifactorial dimensionality reduction analysis.

RESULTS

Among four SNPs analyzed, only FCGR2A 131His/Arg showed significant association with CP in a dominant model (odds ratio: 1.6; 95% confidence interval: 1.028 to 2.530). This significance disappeared after correcting for multiple comparisons using Bonferroni analysis, or after adjusting for age, sex, and OHI. A significant redundant interaction between IL1B +3954 C/T and FCGR2A 131His/Arg was observed.

CONCLUSION

Study results suggest the variant form of the SNP in FCGR2A 131His/Arg, FCGR2B 232Ile/Thr, TNFA -1031T/C, and TNFA -863C/A are not associated with CP susceptibility in the selected cohort from South India.

Association of Fc gamma-receptors IIa, IIIa, and IIIb genetic polymorphism with susceptibility to chronic periodontitis in South Indian population

BACKGROUND AND OBJECTIVE

Fc gamma receptors (FcγRs) are the members of the immunoglobulin superfamily and may play a role in the pathogenesis of periodontitis. Genetic variation in these receptors and its link with various forms of periodontitis is being studied in different populations. The aim of the present study is to determine whether specific FcγRIIa, FcγRIIIa, and FcγRIIIb alleles and/or genotypes are associated with risk for susceptibility to generalized chronic periodontitis (GCP) in South Indian population.

MATERIALS AND METHODS

The study population consisted of 120 South Indian subjects; 60 with GCP and 60 periodontally healthy. Deoxyribonucleic acid (DNA) was extracted from samples collected by scrapping buccal epithelium. FcγRIIa and FcγRIIIa genotyping were performed by polymerase chain reaction (PCR) amplification of DNA with allele-specific primers followed by allele-specific restriction digestion of the products. However, FcγRIIIb genotyping was done by allele-specific PCR.

RESULTS

No significant difference in the distribution of FcγRIIa H/R and FcγRIIIa NA1/NA2 genotypes or their respective alleles was observed in GCP patients and healthy subjects. For FcγRIIIa F/V genetic polymorphism, the homozygous V/V genotype and V allele were significantly overrepresented in GCP patients while F/F genotype and F allele in controls.

CONCLUSION

The present study demonstrates that FcγRIIIa V/V genotype, as well as V allele, could be a possible risk factor for chronic periodontitis in South Indian population.

Associations between FCGR2A rs1801274, FCGR3A rs396991, FCGR3B NA1/NA2 polymorphisms and periodontitis: a meta-analysis

The aim of this study was to determine whether the Fcγ receptors (FCGRs) polymorphisms confer susceptibility to periodontitis in ethnically different populations. We did a literature search using PubMed and Embase, and conducted a meta-analysis on the associations between the FCGR2A H131R (rs1801274), FCGR3A F158V (rs396991), and FCGR3B NA1/NA2 polymorphisms and periodontitis using allele contrast, the recessive model, the dominant model, and the homozygote contrast. A total of 17 separate comparisons with 1,421 patients with periodontitis and 1,454 controls, involving six Caucasian, six East Asian, two African and one South Asian population were considered in the meta-analysis. Meta-analysis of the FCGR2A H131R polymorphism showed no association between periodontitis and the FCGR2A R allele (OR=0.987, 95% CI=0.881-1.107, p=0.827). Stratification by ethnicity revealed an association between the RR+RH genotype with periodontitis in Caucasian population (OR=0.624, 95% CI=0.479-0.813, p=4.7×10(-5)), but not in East Asian, and African populations. Meta-analysis of the FCGR3A F158V polymorphism revealed an association between the FCGR3A V allele and periodontitis is in Caucasians (OR=1.457, 95% CI=1.014-2.092, p=0.042), but not in East Asians and Africans. In addition, analysis using the dominant model and homozygote contrast showed the same pattern for the FCGR3A V allele. Meta-analysis of the FCGR3B NA1/NA2 polymorphism using the recessive model revealed a significant association between the NA2/NA2 genotype and periodontitis in aggressive periodontitis (OR=2.853, 95% CI=1.673-4.863, 1.1×10(-5)). This meta-analysis demonstrates that the FCGR2A, and FCGR3A polymorphisms may confer susceptibility to periodontitis in Caucasians, and that the FCGR3B polymorphism may be associated with susceptibility to aggressive periodontitis.

Genetic polymorphism studies in periodontitis and Fcγ receptors

Periodontitis is a complex chronic subgingival plaque-induced inflammatory disease influenced by multiple factors, including genetics, behavior and the environment. Many genetic association studies have been conducted in periodontology. One of the most extensively investigated gene families is the Fcγ receptor gene family, which plays a key role in regulating host immune responses to bacteria. Unlike other genetic polymorphisms reported in periodontology, most Fcγ receptor polymorphisms reported not only have established biological functions but are reported to associate with other autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus. There are, however, few recent reviews summarizing the association of this gene family with periodontitis. This article critically reviews the current understanding of genetic polymorphism studies in periodontitis, then summarizes the research status of Fcγ receptor polymorphisms and periodontitis and also of other genes involved in the regulatory network of Fcγ receptors, with special reference to their anticipated biological roles. Moreover, some possible future research directions in the related area are discussed.

Fcgamma receptor polymorphisms and their association with periodontal disease: a meta-analysis

AIM

A systematic review and a meta-analysis were conducted in order to investigate the potential association of Fcgamma receptor (FcgammaR) polymorphisms with susceptibility to aggressive and chronic periodontal disease.

MATERIALS AND METHODS

A database search yielded a total of 17 studies involving 1685 cases and 1570 controls. Three polymorphisms were included in the meta-analysis: FcgammaRIIA H131R (rs1801274), FcgammaRIIIA F158V (rs396991) and FcgammaRIIIB NA1/NA2. Random-effect models were used in the analysis. Odds ratios (ORs) along with their 95% confidence intervals (CIs) were computed to compare the distribution of alleles and genotypes between cases and controls.

RESULTS AND CONCLUSIONS

The FcgammaRIIIB NA1/NA2 polymorphism was associated with both aggressive (per-allele OR 2.005, 95% CI: 1.044, 3.851) and chronic periodontitis (recessive contrast NA2NA2 versus NA1NA1+NA1NA2 OR 1.397, 95% CI: 1.039, 1.878). The analysis showed weak evidence for association between the FcgammaRIIA H131R polymorphism and aggressive periodontitis in Asians (R versus H allele OR 1.579, 95% CI: 1.025, 2.432). On the contrary, no relationship was identified between FcgammaRIIIA F158V and periodontal disease. Accumulating evidence from basic research makes the suggested association between FcgammaRIIIB NA1/NA2 polymorphism and periodontitis biologically plausible. Further research, however, is needed in order to assess possible gene-gene or gene-environment interactions (i.e. with smoking).

Gene polymorphisms in chronic periodontitis

We aimed to conduct a review of the literature for gene polymorphisms associated with chronic periodontitis (CP) susceptibility. A comprehensive search of the literature in English was performed using the keywords: periodontitis, periodontal disease, combined with the words genes, mutation, or polymorphism. Candidate gene polymorphism studies with a case-control design and reported genotype frequencies in CP patients were searched and reviewed. There is growing evidence that polymorphisms in the IL1, IL6, IL10, vitamin D receptor, and CD14 genes may be associated with CP in certain populations. However, carriage rates of the rare (R)-allele of any polymorphism varied considerably among studies and most of the studies appeared under-powered and did not correct for other risk factors. Larger cohorts, well-defined phenotypes, control for other risk factors, and analysis of multiple genes and polymorphisms within the same pathway are needed to get a more comprehensive insight into the contribution of gene polymorphisms in CP.

The association of Fcgamma receptor IIIb genetic polymorphism and susceptibility to periodontitis in Taiwanese individuals

AIM

The allelic polymorphism of FcgammaRIIIb, the neutrophil-specific receptor involved in the phagocytosis of immunoglobulin G-opsonized bacteria, has functionally distinct capacities that are important in host defence mediated by neutrophils. The aim of this study was to identify whether the polymorphism of FcgammaRIIIb is associated with periodontitis in Taiwanese individuals.

MATERIALS AND METHODS

This case-control study included of 93 aggressive periodontitis (AgP) patients, 372 chronic periodontitis (CP) patients and 158 healthy controls (HC). The FcgammaRIIIb genotypes were determined by PCR using allele-specific primers. The risk for periodontitis associated with genotypes was calculated as the odds ratio (OR).

RESULTS

A significant difference was observed in the distribution of the FcgammaRIIIb genotype between either AgP and HC, or AgP and CP, but not between CP and HC. The OR for carriage of the NA2 allele (NA1NA2+NA2NA2 versus NA1NA1) in AgP was 3.27 [95% confidence interval (CI)=1.57-7.51, p=0.0027] and 2.94 (95% CI=1.49-6.48, p=0.0037), as compared with HC and CP. After adjusting for possible confounding factors, the association was still significant.

CONCLUSIONS

The results of the present study suggest that subjects carrying at least one copy of the FcgammaRIIIb-NA2 allele might be associated with susceptibility to AgP. However, the clinical implications of the FcgammaRIIIb allelic polymorphism should be determined by further studies.

Low-affinity Fcgamma receptors, autoimmunity and infection

Low-affinity Fcgamma receptors (FcgammaRs) mediate the effects of immunoglobulin G (IgG) antibodies on leukocytes, including recruitment to inflammatory lesions, phagocytosis, antibody-dependent cellular cytotoxicity, release of inflammatory mediators and regulation of B cell activation. These functions are an important part of the mammalian response to infection, but if deployed inappropriately can cause autoimmune disease. Although most FcgammaRs are activatory, there is also an inhibitory FcgammaR that, when bound to IgG immune complexes, is able to downregulate the effects of both the activatory FcgammaRs and the B cell receptor. This review discusses the role of the low-affinity FcgammaRs in a balanced immune response and how perturbations in FcgammaR function result in susceptibility to infection or autoimmunity.

The FcgammaRIIa polymorphism influences production of interleukin-1 by mononuclear cells

The functional bi-allelic polymorphism of immunoglobulin G (IgG) Fc receptor (FcgammaR) IIa influences the efficiency of human IgG2 binding. Our previous study showed that the high affinity FcgammaRIIa genotype (-H/H131) was associated with periodontitis risk. As interleukin-1 (IL-1) is one of the major causes of periodontal tissue destruction, it is hypothesized that the FcgammaRIIa-H/H131cross-linking could induce an increased IL-1 release by mononuclear cells. In this study, we evaluated the intracellular expressions of IL-1beta in CD14 positive cells upon stimulation with human IgG2 by flow cytometry. FcgammaRIIa-H/H131 subjects exhibited a higher percentage of IL-1beta-producing cells than FcgammaRIIa-R/H131 and -R/R131 subjects (P < 0.05). These results support the concept that FcgammaRIIa genotype may affect IL-1beta production, possibly leading to interindividual differences in periodontitis risk.

Genetic susceptibility to infectious diseases: big is beautiful, but will bigger be even better?

Genetic epidemiology, including twin studies, provides robust evidence that genetic variation in human populations contributes to susceptibility to infectious disease. One of the major limitations of studies that attempt to identify the genes and mechanisms that underlie this susceptibility has been lack of power caused by small sample size. With the development of novel technologies, burgeoning information on the human genome, the HapMap project, and human genetic diversity, we are at the beginning of a new era in the study of the genetics of complex diseases. This review looks afresh at the epidemiological evidence that supports a role for genetics in susceptibility to infectious disease, examines the somewhat limited achievements to date, and discusses current advances in methodology and technology that will potentially lead to translational data in the future.

Distribution of FcγRIIa and FcγRIIIb Genotypes in Patients With Generalized Aggressive Periodontitis

BACKGROUND

Polymorphisms in FcgammaR have been associated with different forms of periodontitis. This study determined the frequency of FcgammaRIIa and FcgammaRIIIb alleles/genotypes in patients with generalized aggressive periodontitis (GAgP).

METHODS

Thirty-one GAgP and 49 periodontally healthy Brazilian subjects participated in the study. Full-mouth periodontal examinations were carried out, and mouthwash samples were collected for human DNA isolation. FcgammaR genotyping was performed by polymerase chain reaction and hybridization with allele-specific oligonucleotide probes. Significant differences between groups were sought by Mann-Whitney, chi2, and Fisher exact tests and configural frequency analysis.

RESULTS

FcgammaRIIa-H131 (53.8%) and FcgammaRIIIb-NA1 (75%) were the most prevalent alleles in this sample population. A significant overrepresentation of FcgammaRIIIb-NA2 was observed in the GAgP group, whereas FcgammaRIIIb-NA1 was detected more often in healthy individuals (odds ratio, 32.5; 95% confidence interval [CI], 10.6 to 99.8; P<0.001). No significant differences in the distribution of the FcgammaRIIa genotypes were observed between the groups. The prevalence of FcgammaRIIIb-NA2/NA2 was higher in GAgP patients, whereas FcgammaRIIIb-NA1/NA1 was predominant in the healthy group (chi2=45.1; P<0.001). The combination of the genotypes FcgammaRIIIb-NA2/NA2 plus FcgammaRIIa-H/H131 was observed more frequently in GAgP subjects than expected from marginal frequencies (chi2=12.5; P<0.001).

CONCLUSIONS

The data suggest that the FcgammaRIIIb-NA2 allele and/or FcgammaRIIIb-NA2/NA2 genotype and the composite genotype FcgammaRIIIb-NA2/NA2 plus FcgammaRIIa-H/H131 may be associated with GAgP, whereas FcgammaRIIIb-NA1 and/or FcgammaRIIIb-NA1/NA1 may be related to periodontal health in this sample of the Brazilian population.

Effect of genetic variability on the inflammatory response to periodontal infection

AIM

To review the association between genetic variability and the inflammatory response induced by periodontal infection.

MATERIAL AND METHODS

A search of MEDLINE-PubMed was performed from January 2000 up to and including March 2005. The search included all types of publications, published in English without other limitations. The following search terms were used: "cytokine polymorphism", "gene polymorphism", "periodontitis", "gingivitis", "inflammation" and "host-response". The papers resulting from the above search were used as an additional source for relevant articles.

RESULTS

Genetic variability was examined for the correlation to clinical indicators of inflammation such as bleeding on probing (BOP), gingival inflammation, cytokine in gingival crevicular fluid (GCF) and cytokine production by inflammatory cells. According to the current literature, most of the studies found no association between genetic variability and BOP, gingival inflammation or cytokine concentrations in the GCF. These studies were hampered by inappropriate study designs and the use of inflammatory parameters as secondary rather than primary outcome variables. The data suggest that the production of inflammatory mediators by inflammatory cells may be affected by different genetic traits but further studies are needed in order to establish this association.

CONCLUSIONS

To date, there is no clear correlation between any of the gene polymorphisms and clinical indicators of inflammation. The powering of studies to reveal associations between single or multiple nucleotide polymorphisms and inflammatory parameters will need to involve a much larger number of subjects than were used in the past. The available data (including the interleukin-1 composite genotype) do not currently support the utility of such tests in the diagnosis and prognostic assessments of periodontal diseases.

Identification of genetic risk factors for periodontitis and possible mechanisms of action

AIM

To review the literature for genetic risk factors associated with periodontitis.

METHODS

Computerized search of the literature in English using key words: Periodontitis; Genes; Mutation; Polymorphism; Risk.

RESULTS AND CONCLUSIONS

Mutations in the cathepsin C gene (CTSC) have been identified as causal for the Papillon-Lefèvre syndrome (PLS), which includes prepubertal periodontitis (PP). Some CTSC mutations are causal for PP without PLS. No relationship has been demonstrated between CTSC mutations and other forms of periodontitis. Genetic polymorphisms in a candidate gene approach have been explored as risk factors for periodontitis. There is limited evidence that some polymorphisms in the genes encoding interleukins (IL)-1, Fc gamma receptors (Fc gammaR), IL-10 and the vitamin D receptor, may be associated with periodontitis in certain ethnic groups. However relatively large variations in carriage rates of the Rare (R)-alleles among studies on any polymorphism were observed. The available studies appear under-powered and do not adequately take into account other pertinent risk factors for periodontitis. Future studies should include larger cohorts, should clearly define phenotypes and should adequately control for other risk factors. In addition to the candidate gene approach, alternative strategies need to be considered to elucidate the gene variations, which confer risk for periodontitis.

Analytical epidemiology of periodontitis

AIMS

To review the literature related to the analytical epidemiology of periodontitis generated over the past decade. This review does not deal with descriptive epidemiologic studies of the prevalence, extent and severity of periodontitis with respect to global geography, but focuses exclusively on analytical epidemiology issues, including the challenges posed by the use of different case definitions across studies, current theories and models of disease progression, and risk factors associated with the onset and progression of periodontitis.

METHODS

Relevant publications in the English language were identified after Medline and PubMed database searches.

FINDINGS AND CONCLUSIONS

There is a conspicuous lack of uniformity in the definition of periodontitis used in epidemiologic studies, and findings from different research groups are not readily interpretable. There is a lack of studies that specifically address the distinction between factors responsible for the onset of periodontitis versus those affecting its progression. Colonization by specific bacteria at high levels, smoking, and poorly controlled diabetes have been established as risk factors for periodontitis, while a number of putative factors, including specific gene polymorphisms, have been identified in association studies. There is a clear need for longitudinal prospective studies that address hypotheses emerging from the cross-sectional data and include established risk factors as covariates along with new exposures of interest. Intervention studies, fulfilling the "targeting" step of the risk assessment process, are particularly warranted. Obvious candidates in this context are studies of the efficacy of elimination of specific bacterial species and of smoking cessation interventions as an alternative to the traditional broad anti-plaque approach in the prevention and control of periodontitis. Ideally, such studies should have a randomized-controlled trial design.