Genomewide Association Study Identifies Cxcl Family Members as Partial Mediators of LPS-Induced Periodontitis

Blocking CXCR1/2 attenuates experimental periodontitis by suppressing neutrophils recruitment

Periodontitis (PD) is a common chronic oral inflammatory disease that cause alveolar bone loss. Current strategies for bone regeneration achieve limited results in PD. The aberrant host osteoimmunity to pathogenic bacteria is responsible for the destruction of alveolar bone in PD. We aimed to investigate the distinctive activity of immune cells in PD to create more effective and precise therapeutic approaches for treating PD. In this study, we revealed that neutrophils in the inflamed alveolar bone of PD patients expressed higher levels of CXCR1/2 and had a stronger pro-inflammatory capacity and chemotactic ability than that in healthy individuals. Suppressing the recruitment of neutrophils to inflamed sites with the CXCR1/2 inhibitor reparixin reduced alveolar bone loss in PD mice. In this study, we not only revealed that neutrophils exhibit a heterogeneously stronger pro-inflammatory capacity in the inflamed alveolar bone of PD patients but also provided a precise therapeutic treatment for PD involving the suppression of neutrophil recruitment.

New insights into nanotherapeutics for periodontitis: a triple concerto of antimicrobial activity, immunomodulation and periodontium regeneration

Periodontitis is a chronic inflammatory disease caused by the local microbiome and the host immune response, resulting in periodontal structure damage and even tooth loss. Scaling and root planning combined with antibiotics are the conventional means of nonsurgical treatment of periodontitis, but they are insufficient to fully heal periodontitis due to intractable bacterial attachment and drug resistance. Novel and effective therapeutic options in clinical drug therapy remain scarce. Nanotherapeutics achieve stable cell targeting, oral retention and smart release by great flexibility in changing the chemical composition or physical characteristics of nanoparticles. Meanwhile, the protectiveness and high surface area to volume ratio of nanoparticles enable high drug loading, ensuring a remarkable therapeutic efficacy. Currently, the combination of advanced nanoparticles and novel therapeutic strategies is the most active research area in periodontitis treatment. In this review, we first introduce the pathogenesis of periodontitis, and then summarize the state-of-the-art nanotherapeutic strategies based on the triple concerto of antibacterial activity, immunomodulation and periodontium regeneration, particularly focusing on the therapeutic mechanism and ingenious design of nanomedicines. Finally, the challenges and prospects of nano therapy for periodontitis are discussed from the perspective of current treatment problems and future development trends.

Local delivery of a CXCR3 antagonist decreases the progression of bone resorption induced by LPS injection in a murine model

OBJECTIVES

This experimental study was carried out to investigate the effects of locally delivered nanoparticles (AMG-487 NP) containing a CXCR3 antagonist in inhibiting the progression of LPS-induced inflammation, osteoclastic activity, and bone resorption on a murine model.

MATERIALS AND METHODS

Thirty, 7-week-old C57BL/6 J male mice were used. Inflammatory bone loss was induced by Porphyromonas gingivalis-lipopolysaccharide (P.g.-LPS) injections between the first and second maxillary molars, bilaterally, twice a week for 6 weeks (n = 20). AMG-487 NP were incorporated into a liposome carrier and locally delivered on sites where P.g.-LPS was injected. Control mice (n = 10) were injected with vehicle only. Experimental groups included (1) control, (2) LPS, and (3) LPS + NP. At the end of 1 and 6 weeks, mice were euthanized, maxillae harvested, fixed, and stored for further analysis.

RESULTS

Volumetric bone loss analysis revealed, at 1 week, an increase in bone loss in the LPS group (47.9%) compared to control (27.4%) and LPS + NP (27.8%) groups. H&E staining demonstrated reduced inflammatory infiltrate in the LPS + NP group compared to LPS group. At 6 weeks, volumetric bone loss increased in all groups; however, treatment with the CXCR3 antagonist (LPS + NP) significantly reduced bone loss compared to the LPS group. CXCR3 antagonist treatment significantly reduced osteoclast numbers when compared to LPS group at 1 and 6 weeks.

CONCLUSIONS

This study showed that local delivery of a CXCR antagonist, via nanoparticles, in a bone resorption model, induced by LPS injection, was effective in reducing inflammation, osteoclast numbers, and bone loss.

CLINICAL RELEVANCE

CXCR3 blockade can be regarded as a novel target for therapeutic intervention of bone loss. It can be a safe and convenient method for periodontitis treatment or prevention applicable in clinical practice.

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.

Evaluation of Neutrophilic Receptors; CXCL8 and CXCR2 in Patients with Chronic Periodontitis Compared to Healthy Subjects by Real Time PCR Method

Objective:

This study aimed to evaluate the levels of CXCL8 and its receptor (CXCR2) in gingival tissue neutrophils from patients with chronic periodontitis compared to periodontal healthy subjects using Real Time PCR method.

Methods:

The test group consisted of 21 patients with chronic periodontitis and the control group consisted of 18 healthy individuals. In both groups, gingival tissue samples were obtained during periodontal surgery.CXCL8 and CXCR2 RNA in tissue samples were examined by PCR method, and then the levels of genes expression were measured. Mann-Whitney U nonparametric test was used for statistical analysis.

Results:

CXCL8 gene expression in the gingival tissue of the test group with chronic periodontitis was significantly higher than the control group (p=0.028). CXCR2 gene expression in the gingival tissue of the test group with chronic periodontitis was significantly lower than the control group (p=0.043). In both test and control groups, there was a negative correlation between CXCL8 and CXCR2 gene expression. This correlation was statistically significant in the test group (p=0.001), but there was no significant correlation in the control group (p=0.431).

Conclusion:

The results of this present study suggested that the level of gene expression for CXCL8 was greater in patients with chronic periodontitis and CXCR2 was greater in healthy individuals. Although in people with chronic periodontitis, CXCR2 decreases slightly as CXCL8 levels increase.

Polarization of human gingival fibroblasts by Th1-, Th2-, Th17-, and Treg-derived cytokines

BACKGROUND AND OBJECTIVE

The purpose of this study was to evaluate whether gingival fibroblasts (GFs) can be differently activated and polarized into distinct functional subtypes by T-helper (Th) cytokines.

METHODS

Gingival fibroblasts were stimulated with interferon (IFN)-γ, interleukin (IL)-4, IL-17, and transforming growth factor (TGF)-β, representative cytokines of Th1, Th2, Th17, and regulatory T cells, respectively, and the gene expression profiles were analyzed by microarray. Differentially expressed genes (DEGs) in GFs stimulated by 4 cytokines were screened, and a gene ontology (GO) analysis of the DEGs was conducted. To confirm the reliability of the microarray results, the DEGs that showed the largest differences compared with non-stimulated GFs were further analyzed by RT-PCR. To evaluate the effect of polarization on GFs responses to lipopolysaccharide (LPS), GFs stimulated by 4 cytokines were further stimulated with Escherichia coli LPS and mRNA levels of several genes were analyzed using RT-PCR.

RESULTS

Differentially expressed genes by 4 Th cytokines were enriched in different GO terms, and the patterns of gene expression on GFs were shown functionally different. GFs stimulated with IFN-γ (GF(IFN-γ)) up-regulated the expression of chemokines (chemokine (C-X-C motif) ligand (CXCL)9, -10, -11, chemokine (C-C motif) ligand (CCL)8), molecules involved in antigen presentation, complement component 3 (C3), and other immune response-related molecules, whereas they down-regulated the expression of several types of collagen, extracellular matrix (ECM) components, and DNA replication and nuclear protein-related molecules. By contrast, GF(IL-4) up-regulated the expression of ECM components, cell adhesion molecules, and tissue development-related molecules and down-regulated the expression of chemokines (CXCL10 and CXCL8) and adaptive immune response-related molecules. GF(IL-17) up-regulated the expression of chemokines and other molecules for neutrophil infiltration and activation, the pro-inflammatory cytokine IL-6, and C3. GF(TGF-β) up-regulated the expression of cell growth-related molecules, ECM components, several types of collagen, and cell adhesion molecules and down-regulated the expression of molecules related to complement activation and bacterial recognition. GFs stimulated by 4 cytokines responded differently to LPS.

CONCLUSION

These results show that Th cytokines can polarize GFs into cells with functionally distinct features: immune-activating but tissue-destructive GF(IFN-γ), tissue-reparative, and immune-inhibiting GF(IL-4), highly pro-inflammatory GF(IL-17), and potent tissue-reparative GF(TGF-β).

Role of enhancer of zeste homolog 2 in osteoclast formation and periodontitis development by downregulating microRNA-101-regulated VCAM-1

The enhancer of zeste homolog 2 (EZH2) represents a potential target for periodontitis treatment; however, its role in the development of periodontitis remains unclear. The current study aimed to elucidate the role of EZH2 in osteoclasts (OCs) growth as well as the mechanism underpinning the related process. The potential interaction among EZH2, microRNA-101 (miR-101), and vascular cell adhesion molecule 1 (VCAM-1) was evaluated using chromatin immunoprecipitation and dual-luciferase reporter gene assay. The expressions of EZH2 and miR-101 in OCs were examined by Western blot analysis and reverse transcription squantitative polymerase chain reaction. Loss- and gain-function assays were then performed to determine the role of EZH2/miR-101/VCAM-1 in periodontitis and OCs proliferation, followed by OC growth and proliferation detected using tartrate resistant acid phosphatase (TRAP) and 5-ethynyl-2'-deoxyuridine staining. Enzyme-linked immunoassay was conducted to determine the expression of interleukin 1β (IL-1β) and tumor necrosis factor-α (TNF-α). A periodontitis rat model was established to investigate the effect of EZH2 and VCAM-1 in vivo. EZH2 was overexpressed, while miR-101 was downregulated in the OCs of periodontitis. Silencing of EZH2, VCAM-1 repression, or miR-101 elevation suppressed the growth and proliferation of OC while acting to encumber the release of IL-1β and TNF-α. EZH2 negatively targeted miR-101, while miR-101 negatively targeted VCAM-1. Moreover, silencing of EZH2 or VCAM-1 was observed to attenuate periodontitis which was evidenced by an increase in BMD, BV/TV, and BS/BV as well as reduction in TRAP and cathepsin K in vivo. Taken together, the key findings of the current study demonstrate that EZH2 knockdown inhibited OC formation by elevating the expression of miR-101 via suppression of VCAM-1, ultimately attenuating periodontitis.

mRNA Transcriptome Analysis of Bone in a Mouse Model of Implant-Associated Staphylococcus aureus Osteomyelitis

To investigate the molecular pathogenesis of bone with osteomyelitis, we developed implant-associated osteomyelitis (IAOM) models in mice. An orthopedic stainless pin was surgically placed in the right femoral midshaft of mice, followed by an inoculation of Staphylococcus aureus into the medullary cavity. Typical characteristics of IAOM, like periosteal reaction and intraosseous abscess, occurred by day 14 postinfection. By day 28 postinfection, necrotic abscess, sequestrum formation, and deformity of the whole femur were observed. Transcriptional analysis identified 101 and 1,702 differentially expressed genes (DEGs) between groups by days 3 and 14 postinfection, respectively. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses revealed the enrichment of pathways in response to the bacterium, receptor-ligand activity, and chemokine signaling by day 3 postinfection. However, by day 14 postinfection, the enrichment switched to angiogenesis, positive regulation of cell motility and migration, skeletal system development, and cytokine-cytokine receptor interaction. Furthermore, protein-protein interaction network analysis identified 4 cytokines (interleukin 6 [IL-6], Cxcl10, gamma interferon [IFN-γ], and Cxcl9) associated with IAOM at an early stage of infection. Overall, as the pathological changes in this mouse model were consistent with those in human IAOM, our model may be used to investigate the mechanism and treatment of IAOM. Furthermore, the data for transcriptome sequencing and bioinformatic analysis will be an important resource for dissecting the molecular pathogenesis of bone with IAOM.

Intermediate monocytes correlate with CXCR3+ Th17 cells but not with bone characteristics in untreated early rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) is associated with development of generalized osteoporosis. Bone-degrading osteoclasts are derived from circulating precursor cells of monocytic lineage, and the intermediate monocyte population is important as osteoclast precursors in inflammatory conditions. T cells of various subsets are critical in the pathogenesis of both RA and associated osteoporosis, but so far, no studies have examined associations between circulating intermediate monocytes, T cell subsets and bone characteristics in patients with RA. The aim of this study was to investigate the frequency of intermediate monocytes in patients with untreated early rheumatoid arthritis (ueRA) compared to healthy controls (HC), and to explore the correlation between intermediate monocytes and a comprehensive panel of T helper cell subsets, bone density and bone microarchitecture in ueRA patients.

METHODS

78 patients with ueRA fulfilling the ACR/EULAR 2010 criteria were included and compared to 29 age- and sex-matched HC. Peripheral blood samples were obtained before start of treatment and proportions of monocyte subsets and CD4+ helper and regulatory T cell subsets were analyzed by flow cytometry. Bone densitometry was performed on 46 of the ueRA patients at inclusion using DXA and HR-pQCT.

RESULTS

Flow cytometric analyses showed that the majority of ueRA patients had frequencies of intermediate monocytes comparable to HC. The intermediate monocyte population correlated positively with CXCR3+ Th17 cells in ueRA patients but not in HC. However, neither the proportions of intermediate monocytes nor CXCR3+ Th17 cells were associated with bone density or bone microarchitecture measurements.

CONCLUSIONS

Our findings suggest that in early RA, the intermediate monocytes do not correlate with bone characteristics, despite positive correlation with circulating CXCR3+ Th17 cells. Future longitudinal studies in patients with longer disease duration are required to fully explore the potential of intermediate monocytes to drive bone loss in RA.

Inhibition of the CXCL9-CXCR3 axis suppresses the progression of experimental apical periodontitis by blocking macrophage migration and activation

Apical periodontitis (AP) is an acute or chronic inflammatory disease caused by complex interactions between infected root canal and host immune system. It results in the induction of inflammatory mediators such as chemokines and cytokines leading to periapical tissue destruction. To understand the molecular pathogenesis of AP, we have investigated inflammatory-related genes that regulate AP development. We found here that macrophage-derived CXCL9, which acts through CXCR3, is recruited by progressed AP. The inhibition of CXCL9 by a CXCR3 antagonist reduced the lesion size in a mouse AP model with decreasing IL-1β, IL-6 and TNFα expression. The treatment of peritoneal macrophages with CXCL9 and LPS induced the transmigration and upregulation of osteoclastogenic cytokines such as IL-1β, IL-6 and matrix metalloprotease 2, a marker of activated macrophages. This suggests that the CXCL9-CXCR3 axis plays a crucial role in the development of AP, mediated by the migration and activation of macrophages for periapical tissue destruction. Our data thus show that CXCL9 regulates the functions of macrophages which contribute to AP pathogenesis, and that blocking CXCL9 suppresses AP progression. Knowledge of the principal factors involved in the progression of AP, and the identification of related inflammatory markers, may help to establish new therapeutic strategies.

The Complex Molecular Picture of Gut and Oral Microbiota-Brain-Depression System: What We Know and What We Need to Know

Major depressive disorder (MDD) is a complex mental disorder where the neurochemical, neuroendocrine, immune, and metabolic systems are impaired. The microbiota-gut-brain axis is a bidirectional network where the central and enteric nervous systems are linked through the same endocrine, immune, neural, and metabolic routes dysregulated in MDD. Thus, gut-brain axis abnormalities in MDD patients may, at least in part, account for the symptomatic features associated with MDD. Recent investigations have suggested that the oral microbiome also plays a key role in this complex molecular picture of relationships. As on one hand there is a lot of what we know and on the other hand little of what we still need to know, we structured this review focusing, in the first place, on putting all pieces of this complex puzzle together, underlying the endocrine, immune, oxidative stress, neural, microbial neurotransmitters, and metabolites molecular interactions and systems lying at the base of gut microbiota (GM)-brain-depression interphase. Then, we focused on promising but still under-explored areas of research strictly linked to the GM and potentially involved in MDD development: (i) the interconnection of GM with oral microbiome that can influence the neuroinflammation-related processes and (ii) gut phageome (bacteria-infecting viruses). As conclusions and future directions, we discussed potentiality but also pitfalls, roadblocks, and the gaps to be bridged in this exciting field of research. By the development of a broader knowledge of the biology associated with MDD, with the inclusion of the gut/oral microbiome, we can accelerate the growth toward a better global health based on precision medicine.

Evaluating the Role of CXCR3 in Pain Modulation: A Literature Review

CXCR3 is a well-known receptor involved in immune cell recruitment and inflammation. Pathological inflammation leads to pain stimulation and hence nociception. Therefore, we decided to review the recent research on CXCR3 to identify its precise role in the modulation of pain in a variety of clinical conditions targeting various regions of the body. Studies were selected from PubMed Medline, which relate CXCR3 to the progression of diseases with either bone cancer pain, neuropathic pain, cystitis pain, osteoarthritis and rheumatoid arthritis pain, dental pain, in particular, periodontitis and pulpitis. In all the diseases studied, a high prevalence of CXCR3 and/or its ligand were identified where CXCR3 is a key player in the pathophysiological process of many inflammatory conditions. CXCR3 and its ligands, particularly CXCL10, modulate nociception via actions in the dorsal root ganglia and dorsal horn of the spinal cord, in cases of bone cancer pain, neuropathic, and joint pain. However, with the other studied disease, no direct link to pain has been made, although it contributes to the pathological progression of the diseases and hence would be a causal factor for the pain. Furthermore, CXCR3 appears to play a role in desensitizing the opioid receptor in the descending modulatory pathway within the brain stem as well as modulating opioid-induced hyperalgesia in the dorsal horn of the spinal cord. Further research is required for understanding the exact mechanisms of CXCR3 in pain modulation centrally and peripherally. A greater understanding of the immunological activities and pharmacological consequence of CXCR3 and its ligands could help in the discovery of newer drugs for modulating pain arising from pathogenic or inflammatory sources. Given the significance of the CXCR3 for nociception, its utilization may prove to be beneficial as a target for analgesia.

Cxcl9l and Cxcr3.2 regulate recruitment of osteoclast progenitors to bone matrix in a medaka osteoporosis model

Bone remodeling requires a balanced interplay of osteoblasts and osteoclasts. While the intercellular signaling that triggers bone cell differentiation is well understood, it remains unclear how bone progenitor cells are recruited to remodeling sites. Various chemokines are upregulated under osteoporotic conditions. However, whether they are involved in progenitor recruitment or instead have inflammatory roles is unknown. Here we used a medaka fish osteoporosis model to identify the chemokine ligand Cxcl9l and receptor Cxcr3.2 as essential to control osteoclast progenitor recruitment and differentiation at bone resorption sites. Cxcr3.2 activity can be blocked by small-molecule inhibitors that protect bone from osteoporotic insult. Our study demonstrates the potential of fish for osteoporosis drug discovery and opens avenues for future osteoporosis therapy.

Bone homeostasis requires continuous remodeling of bone matrix to maintain structural integrity. This involves extensive communication between bone-forming osteoblasts and bone-resorbing osteoclasts to orchestrate balanced progenitor cell recruitment and activation. Only a few mediators controlling progenitor activation are known to date and have been targeted for intervention of bone disorders such as osteoporosis. To identify druggable pathways, we generated a medaka (Oryzias latipes) osteoporosis model, where inducible expression of receptor-activator of nuclear factor kappa-Β ligand (Rankl) leads to ectopic formation of osteoclasts and excessive bone resorption, which can be assessed by live imaging. Here we show that upon Rankl induction, osteoblast progenitors up-regulate expression of the chemokine ligand Cxcl9l. Ectopic expression of Cxcl9l recruits mpeg1-positive macrophages to bone matrix and triggers their differentiation into osteoclasts. We also demonstrate that the chemokine receptor Cxcr3.2 is expressed in a distinct subset of macrophages in the aorta-gonad-mesonephros (AGM). Live imaging revealed that upon Rankl induction, Cxcr3.2-positive macrophages get activated, migrate to bone matrix, and differentiate into osteoclasts. Importantly, mutations in cxcr3.2 prevent macrophage recruitment and osteoclast differentiation. Furthermore, Cxcr3.2 inhibition by the chemical antagonists AMG487 and NBI-74330 also reduced osteoclast recruitment and protected bone integrity against osteoporotic insult. Our data identify a mechanism for progenitor recruitment to bone resorption sites and Cxcl9l and Cxcr3.2 as potential druggable regulators of bone homeostasis and osteoporosis.

An Evidence-Based Update on the Molecular Mechanisms Underlying Periodontal Diseases

Several investigators have reported about the intricate molecular mechanism underlying periodontal diseases (PD). Nevertheless, the role of specific genes, cells, or cellular mechanisms involved in the pathogenesis of periodontitis are still unclear. Although periodontitis is one of the most prevalent oral diseases globally, there are no pre-diagnostic markers or therapeutic targets available for such inflammatory lesions. A pivotal role is played by pro- and anti-inflammatory markers in modulating pathophysiological and physiological processes in repairing damaged tissues. In addition, effects on osteoimmunology is ever evolving due to the ongoing research in understanding the molecular mechanism lying beneath periodontal diseases. The aim of the current review is to deliver an evidence-based update on the molecular mechanism of periodontitis with a particular focus on recent developments. Reports regarding the molecular mechanism of these diseases have revealed unforeseen results indicative of the fact that significant advances have been made to the periodontal medicine over the past decade. There is integrated hypothesis-driven research going on. Although a wide picture of association of periodontal diseases with immune response has been further clarified with present ongoing research, small parts of the puzzle remain a mystery and require further investigations.

Genomics of periodontal disease and tooth morbidity

In this review we critically summarize the evidence base and the progress to date regarding the genomic basis of periodontal disease and tooth morbidity (ie, dental caries and tooth loss), and discuss future applications and research directions in the context of precision oral health and care. Evidence for these oral/dental traits from genome-wide association studies first emerged less than a decade ago. Basic and translational research activities in this domain are now under way by multiple groups around the world. Key departure points in the oral health genomics discourse are: (a) some heritable variation exists for periodontal and dental diseases; (b) the environmental component (eg, social determinants of health and behavioral risk factors) has a major influence on the population distribution but probably interacts with factors of innate susceptibility at the person-level; (c) sizeable, multi-ethnic, well-characterized samples or cohorts with high-quality measures on oral health outcomes and genomics information are required to make decisive discoveries; (d) challenges remain in the measurement of oral health and disease, with current periodontitis and dental caries traits capturing only a part of the health-disease continuum, and are little or not informed by the underlying biology; (e) the substantial individual heterogeneity that exists in the clinical presentation and lifetime trajectory of oral disease can be identified and leveraged in a precision medicine framework or, if unappreciated, can hamper translational efforts. In this review we discuss how composite or biologically informed traits may offer improvements over clinically defined ones for the genomic interrogation of oral diseases. We demonstrate the utility of the results of genome-wide association studies for the development and testing of a genetic risk score for severe periodontitis. We conclude that exciting opportunities lie ahead for improvements in the oral health of individual patients and populations via advances in our understanding of the genomic basis of oral health and disease. The pace of new discoveries and their equitable translation to practice will largely depend on investments in the education and training of the oral health care workforce, basic and population research, and sustained collaborative efforts..

A GWAS approach identifies Dapp1 as a determinant of air pollution-induced airway hyperreactivity

Asthma is a chronic inflammatory disease of the airways with contributions from genes, environmental exposures, and their interactions. While genome-wide association studies (GWAS) in humans have identified ~200 susceptibility loci, the genetic factors that modulate risk of asthma through gene-environment (GxE) interactions remain poorly understood. Using the Hybrid Mouse Diversity Panel (HMDP), we sought to identify the genetic determinants of airway hyperreactivity (AHR) in response to diesel exhaust particles (DEP), a model traffic-related air pollutant. As measured by invasive plethysmography, AHR under control and DEP-exposed conditions varied 3-4-fold in over 100 inbred strains from the HMDP. A GWAS with linear mixed models mapped two loci significantly associated with lung resistance under control exposure to chromosomes 2 (p = 3.0x10^-6) and 19 (p = 5.6x10^-7). The chromosome 19 locus harbors Il33 and is syntenic to asthma association signals observed at the IL33 locus in humans. A GxE GWAS for post-DEP exposure lung resistance identified a significantly associated locus on chromosome 3 (p = 2.5x10^-6). Among the genes at this locus is Dapp1, an adaptor molecule expressed in immune-related and mucosal tissues, including the lung. Dapp1-deficient mice exhibited significantly lower AHR than control mice but only after DEP exposure, thus functionally validating Dapp1 as one of the genes underlying the GxE association at this locus. In summary, our results indicate that some of the genetic determinants for asthma-related phenotypes may be shared between mice and humans, as well as the existence of GxE interactions in mice that modulate lung function in response to air pollution exposures relevant to humans.

The genetic factors that modulate risk of asthma through gene-environment (GxE) interactions are poorly understood, due in large part to the inherent difficulties in carrying out such studies in humans. To address these challenges, we used the Hybrid Mouse Diversity Panel to elucidate the genetic architecture of asthma-related phenotypes in mice and identify loci that are associated with airway hyperreactivity (AHR) under control exposure conditions and in response to diesel exhaust particles (DEP), as a model traffic-related air pollutant. In the absence of exposure, we identified two loci on chromosomes 2 and 19 for AHR. The locus on chromosome 19 harbors Il33 and is syntenic to association signals observed for asthma at the IL33 locus in humans. In response to DEP exposure, we mapped AHR to a region on chromosome 3 and used a genetically modified mouse model to functionally demonstrate that Dapp1 is one of the genes underlying the GxE association at this locus. Collectively, our results support the concept that some of the genetic determinants for asthma-related phenotypes may be shared between mice and humans as well as the existence of GxE interactions in mice that modulate lung function in response to air pollution exposures relevant to humans.

RNA sequencing for ligature induced periodontitis in mice revealed important role of S100A8 and S100A9 for periodontal destruction

Periodontitis is an inflammatory disease caused by pathogenic oral microorganisms that induce the destruction of periodontal tissue. We sought to identify the relevant differentially expressed genes (DEGs) and clarify the mechanism underlying the rapid alveolar bone loss by using ligature-induced periodontitis in mice. A silk ligature was tied around the maxillary left second molar in 9-week-old C57BL/6 J male mice. In-vivo micro-CT analysis revealed that ligation induced severe bone loss. RNA-sequencing analysis, to examine host responses at 3 days post-ligation, detected 12,853 genes with fragments per kilobase of exon per million mapped reads ≥ 1, and 78 DEGs. Gene ontology term enrichment analysis revealed the expression profiles related to neutrophil chemotaxis and inflammatory responses were significantly enriched in the ligated gingiva. The expression levels of innate immune response-related genes, including S100a8 and S100a9, were significantly higher in the ligated side. S100A8 was strongly detected by immunohistochemistry at the attached epithelium in ligated sites. Inhibition of S100A8 and S100A9 expression revealed that they regulated IL1B and CTSK expression in Ca9-22 cells. Thus, innate immune response-related molecules might be associated with the burst-destruction of periodontal tissue in ligature-induced periodontitis. Especially, S100A8 and S100A9 may play an important role in alveolar bone resorption.

The Osteocyte as a Novel Key Player in Understanding Periodontitis Through its Expression of RANKL and Sclerostin: a Review

PURPOSE OF REVIEW

Periodontitis is the inflammation-associated bone loss disease of the alveolar bone that surrounds teeth. Classically, the emphasis on the etiology of periodontitis has been on the products of periodontal pathogens that lead to an inflammatory response of the soft tissues of the periodontium, eventually leading to activation of osteoclasts that degrade the alveolar bone. Until recently, the response of osteocytes that populate the alveolar bone, and that are known for their regulatory role in bone anabolism and catabolism, has not been addressed.

RECENT FINDINGS

This review demonstrates that osteocytes play a key contributing role in periodontitis progression in various experimental mouse and rat periodontitis models. Osteocytes are the key expressing cells of both osteoclast differentiation factor RANKL as well as osteoblast activity regulator sclerostin. Targeted deletion of RANKL in osteocytes prevents osteoclast formation, thereby impairing periodontitis, despite the pressure of periodontitis-associated bacteria. Antibodies against the osteocyte-derived protein sclerostin inhibit and partially revert periodontitis by stimulating bone formation. Experimental mouse and rat periodontitis models strongly indicate a key role for the bone-encapsulated osteocyte in understanding periodontitis etiology.

Evaluation of chemokine CXCL10 in human gingival crevicular fluid, saliva, and serum as periodontitis biomarker

Purpose

The aim of this study was to evaluate CXCL10 as a biomarker for periodontitis by determining the CXCL10 levels in saliva, serum, and gingival crevicular fluid (GCF) samples from periodontally healthy control subjects and adult subjects with chronic periodontitis.

Patients and methods

Adult patients seeking dental treatment at Umm Al-Qura University dental clinic underwent a complete periodontal examination, and saliva, serum, and GCF samples were collected. Subjects were classified as chronic periodontitis patients (n=31) if they have a periodontal probing depth (PD) of ≥4 mm and/or clinical attachment level (CAL) of ≥3 mm in >30% of the teeth. The control group (n=25) had PD ≤3 mm and/or CAL ≤2 mm. ELISA was performed to determine the concentration of CXCL10 in saliva, serum, and GCF samples. Student’s t-test was carried out to evaluate the significant difference between different groups. Spearman’s correlation test was used to analyze the relationship between the levels of CXCL10 and the clinical periodontal parameters. P-value of ≤0.05 was considered significant.

Results

Significantly higher concentrations of CXCL10 were found in saliva and serum in chronic periodontitis patients as compared with the controls (272±60.4 pg/mL and 72±13.4 pg/mL vs 130±22.2 pg/mL and 44.08±4.5 pg/mL, P≤0.05). The CXCL10 levels in GCF were higher in the periodontitis group as compared with the control group (66.36±32.0 pg/mL and 44.56±17.5 pg/mL, respectively); the difference did not reach statistical significance (P≥0.05). Moreover, serum CXCL10 level was significantly higher in periodontitis patients with moderate to severe bone loss as compared with those with mild bone loss (71.05±4.7 pg/mL vs 54.8±7.7 pg/mL, P≤0.05). The serum CXCL10 levels were found to be related to CAL measurements (r=0.3, P=0.026), while the saliva CXCL10 levels were related to PD measurements (r=0.8, P=0.0007).

Conclusion

CXCL10 is significantly increased in periodontitis subjects as compared with controls and could be used as a marker for periodontal disease.