RANKL expression in periodontal disease: where does RANKL come from?

The role of MIF in periodontitis: A potential pathogenic driver, biomarker, and therapeutic target

OBJECTIVE

Periodontitis is an inflammatory disease that involves an imbalance in the oral microbiota, activation of inflammatory and immune responses, and alveolar bone destruction. Macrophage migration inhibitory factor (MIF) is a versatile cytokine involved in several pathological reactions, including inflammatory processes and bone destruction, both of which are characteristics of periodontitis. While the roles of MIF in cancer and other immune diseases have been extensively characterized, its role in periodontitis remains inconclusive.

RESULTS

In this review, we describe a comprehensive analysis of the potential roles of MIF in periodontitis from the perspective of immune response and bone regulation at the cellular and molecular levels. Moreover, we discuss its potential reliability as a novel diagnostic and therapeutic target for periodontitis.

CONCLUSION

This review can aid dental researchers and clinicians in understanding the current state of MIF-related pathogenesis, diagnosis, and treatment of periodontitis.

Overview, Trends, and Collaboration on Immunization, Vaccination, and Immunomodulation Therapies for Periodontitis: A Scientometric Study

AIM

To identify patterns and trends in the field of immunization, vaccination, and immunomodulation therapies for periodontitis.

MATERIALS AND METHODS

Metadata were collected from the Scopus database on publications related to these topics from January 1986 to February 2024. Several types of papers were included in this study, a total of 22 publications. Data were extracted from relevant publications and loaded into SciVal for analysis that were used to identify trends and patterns in the data, including cross-country collaboration, thematic evolution, and keyword distribution.

RESULTS

Mohsen Amin of Tehran University of Medical Sciences in Iran and S. Aadil Ahamed and Annie Kitty George of Saveetha Institute of Medical and Technical Sciences in India were found to be notable contributors in this field. India leads in terms of academic paper production, followed by Iran and China. The journals Expert Review of Vaccines and International Immunopharmacology have published significant papers in this field.

CONCLUSIONS

According to Lotka's Law, most authors have written only one paper, reflecting the distribution of productivity in many academic and scientific fields. Collaborations were observed between Iran and Canada, Korea and New Zealand, and the United States and Belgium. This study provides useful insight into the predominant trends and patterns in the scientific literature in the field of immunization, vaccination, and immunomodulation therapies for periodontitis.

CLINICAL SIGNIFICANCE

The findings of this study may help to understand the dynamics of the production on immunization, vaccination, and immunomodulation therapies could reduce the inflammation and progression of periodontitis, thus improving the patient's oral and overall health. How to cite this article: Mauricio F, Mendoza R, Silva H, et al. Overview, Trends, and Collaboration on Immunization, Vaccination, and Immunomodulation Therapies for Periodontitis: A Scientometric Study. J Contemp Dent Pract 2024;25(2):128-133.

Ebi3 knockout aggravates experimental periodontitis via Th17 polarization

AIM

To investigate the role of Ebi3-related cytokines (i.e., interleukin [IL]-35 and/or IL-27) in experimental periodontitis using Ebi3 knockout (KO) mice.

MATERIALS AND METHODS

The maxillary right second molar teeth of Ebi3 KO mice and C57BL/6 mice were tied with a silk ligature to induce periodontitis. Three days after ligation, gingival tissues were collected for gene expression analyses. Five days after ligation, the maxillae were removed for haematoxylin and eosin staining and immunohistochemistry. Seven days after ligation, the maxillae were removed for micro-computed tomography.

RESULTS

The ligated side of Ebi3 KO mice showed intense alveolar bone resorption, which was substantially more pronounced than in wild-type (WT) mice. IL-17A expression was significantly higher in the gingiva of the ligated side of Ebi3 KO mice compared with WT mice. IL-10 expression was significantly lower in Ebi3 KO mice than in WT mice. The ligature-induced alveolar bone resorption in Ebi3 KO mice that received recombinant IL-35 injection was significantly less compared with that in Ebi3 KO mice that received control injection.

CONCLUSIONS

Together, these findings suggest that Th17 cells exacerbate experimental periodontitis in mice lacking Ebi3 and that IL-35 may play a critical role in inhibiting periodontal tissue destruction.

Macrophages immunomodulation induced by Porphyromonas gingivalis and oral antimicrobial peptides

Porphyromonas gingivalis is a keystone pathogen associated with periodontitis development, a chronic inflammatory pathology characterized by the destruction of the supporting teeth structure. Macrophages are recruited cells in the inflammatory infiltrate from patients with periodontitis. They are activated by the P. gingivalis virulence factors arsenal, promoting an inflammatory microenvironment characterized by cytokine production (TNF-α, IL-1β, IL-6), prostaglandins, and metalloproteinases (MMPs) that foster the tissular destruction characteristic of periodontitis. Furthermore, P. gingivalis suppresses the generation of nitric oxide, a potent antimicrobial molecule, through its degradation, and incorporating its byproducts as a source of energy. Oral antimicrobial peptides can contribute to controlling the disease due to their antimicrobial and immunoregulatory activity, which allows them to maintain homeostasis in the oral cavity. This study aimed to analyze the immunopathological role of macrophages activated by P. gingivalis in periodontitis and suggested using antimicrobial peptides as therapeutic agents to treat the disease.

miR-1260b inhibits periodontal bone loss by targeting ATF6β mediated regulation of ER stress

The expression profiles of exosomal microRNAs (miRNAs) are regulated by the microenvironment, and appropriate priming with mesenchymal stem cells (MSCs) is one of the strategies to enhance the paracrine potency of MSCs. Our previous work demonstrated that exosomes from tumor necrosis factor (TNF)-α-primed human gingiva-derived MSCs (GMSCs) could be a therapeutic tool against periodontitis, and that TNFα-inducible exosomal miR-1260b is essential for the inhibition of alveolar bone loss. However, the precise molecular mechanism underlying miR-1260b-mediated inhibition of osteoclastogenesis is not yet fully understood. Here, we found that the activating transcription factor (ATF)-6β, a novel miR-1260b-targeting gene, is critical for the regulation of osteoclastogenesis under endoplasmic reticulum (ER) stress. An experimental periodontal mouse model demonstrated that induction of ER stress was accompanied by enhanced ATF6β expression, and local administration of miR-1260b and ATF6β siRNA using polyethylenimine nanoparticles (PEI-NPs) significantly suppressed the periodontal bone resorption. In periodontal ligament (PDL) cells, the ER stress inducer, tunicamycin, enhanced the expression of the receptor activator of NF-κB ligand (RANKL), while miR-1260b-mediated downregulation of ATF6β caused RANKL inhibition. Furthermore, the secretome from miR-1260b/ATF6β-axis-activated PDL cells inhibited osteoclastogenesis in human CD14+ peripheral blood-derived monocytes. These results indicate that the miR-1260b/ATF6β axis mediates the regulation of ER stress, which may be used as a novel therapeutic strategy to treat periodontal disease.

Excessive inflammatory response to infection in experimental peri-implantitis: Resolution by Resolvin D2

AIM

The aetiology and pathogenesis of peri-implantitis are currently under active research. This study aimed to dissect the pathogenesis of murine experimental peri-implantitis and assess Resolvin D2 (RvD2) as a new treatment modality.

MATERIALS AND METHODS

Four weeks following titanium implant insertion, mice were infected with Porphyromonas gingivalis using single or multiple oral lavages. RvD2 was administrated following infection, and tissues were analysed using flow cytometry, quantitative RT-PCR, taxonomic profiling, and micro-computed tomography.

RESULTS

Repeated infections with Pg resulted in microbial dysbiosis and a higher influx of innate and adaptive leukocytes to the peri-implant mucosa (PIM) than to gingiva surrounding the teeth. This was accompanied by increased expression levels of IFN-α, IL-1β, and RANKL\OPG ratio. Interestingly, whereas repetitive infections resulted in bone loss around implants and teeth, a single infection induced bone loss only around implants, suggesting a higher susceptibility of the implants to infection. Treatment with RvD2 prevented Pg-driven bone loss and reduced leukocyte infiltration to the PIM.

CONCLUSIONS

Murine dental implants are associated with dysregulated local immunity and increase susceptibility to pathogen-induced peri-implantitis. However, the disease can be prevented by RvD2 treatment, highlighting the promising therapeutic potential of this treatment modality.

Development of an Orally Active Small-Molecule Inhibitor of Receptor Activator of Nuclear Factor-κB Ligand

Receptor activator of nuclear factor-κB (RANK) and its ligand, RANKL, play pivotal roles in bone remodeling. The monoclonal antibody denosumab successfully inhibited the maturation of osteoclasts (OCs) by binding to RANKL in the clinic. We continued our efforts to develop small-molecule inhibitors of RANKL. In this work, 41 β-carboline derivatives were synthesized based on previously synthesized compound Y1599 to improve its drug-like properties. Compound Y1693 was identified as a potent RANKL inhibitor that improved absorption-distribution-metabolism-excretion properties and effectively prevented RANKL-induced osteoclastogenesis and bone resorption. Furthermore, Y1693 also suppressed the expression of OC marker genes. Moreover, Y1693 demonstrated good tolerability and efficacy in an orally administered mouse model of osteoporosis as well as the ability to rescue alveolar bone loss in vivo caused by periodontal disease. Collectively, the above findings may provide a valuable direction for the development of novel antiresorptive therapies that target RANKL.

The Influence of Periodontal Diseases and the Stimulation of Saliva Secretion on the Course of the Acute Phase of Ischemic Stroke

Background and purpose: The course of an ischemic stroke depends on many factors. The influence of periodontal diseases and the stimulation of salivation on the course and severity of stroke remains unresolved. Therefore, the aim of the study was to analyze the severity of ischemic stroke depending on the occurrence of periodontal diseases and saliva stimulation. Methods: The severity of the neurological condition was assessed using the NIHSS scale on days one, three and seven of stroke. The incidence of periodontal diseases was classified using the Hall’s scale in the first day of stroke. On days one and seven of stroke, the concentration of IL-1β, MMP-8, OPG and RANKL in the patients’ saliva was assessed using the Elisa technique. At the same time, the level of CRP and the number of leukocytes in the peripheral blood were tested on days one, three and seven of the stroke, and the incidence of upper respiratory and urinary tract infections was assessed. Results:100 consecutive patients with their first ever ischemic stroke were enrolled in the study. 56 randomly selected patients were subjected to the stimulation of salivation, the remaining patients were not stimulated. In the study of the severity of the neurological condition using the NIHS scale on days three and seven of stroke, the degree of deficit in patients without periodontal disease significantly improved compared to patients with periodontal disease, respectively (p < 0.01 and p = 0.01). Patients from the stimulated group had more severe neurological deficit at baseline (p = 0.04). On days three and seven of neurological follow-up, the condition of patients from both groups improved with a further distinct advantage of the unstimulated group over the stimulated group, respectively (p = 0.03 and p < 0.001). In patients from both groups, a statistically significant decrease in CRP and lymphocyte levels was observed on day seven in relation to day one. Conclusions: The occurrence of periodontal disease in a patient with stroke affects the severity of stroke. Stimulation of the mouth and salivary glands in these patients may have a positive effect on the course of stroke, taking into account the dynamics of neurological symptoms.

A vitronectin-derived peptide prevents and restores alveolar bone loss by modulating bone re-modelling and expression of RANKL and IL-17A

AIM

This study investigated whether a vitronectin-derived peptide (VnP-16) prevents and/or reverses alveolar bone resorption induced by ligature-induced periodontitis in rodents and identified the underlying mechanism.

MATERIALS AND METHODS

We evaluated the effects of VnP-16 on osteogenic differentiation in human periodontal ligament cells (hPDLCs), lipopolysaccharide-induced inflammatory responses in gingival fibroblasts, and immune response in T lymphocytes. Ligature-induced periodontitis was induced by ligating the bilateral mandibular first molars for 14 days in rats and for 7 days in mice (n = 10/group). VnP-16 (100 μg/10 μl) was applied topically into the gingival sulcus of rats via intra-sulcular injection, whereas the peptide (50 μg/5 μl) was administered directly into the gingiva of mice via intra-gingival injection. To evaluate the preventive and therapeutic effects of VnP-16, micro-computed tomography analysis and histological staining were then performed.

RESULTS

VnP-16 promoted osteogenic differentiation of periodontal ligament cells and inhibited the production of lipopolysaccharide-induced inflammatory mediators in gingival fibroblasts. Concomitantly, VnP-16 modulated the host immune response by reducing the number of receptor activator of NF-κB ligand (RANKL)-expressing lipopolysaccharide-stimulated CD4⁺ and CD8⁺ T cells, and by suppressing RANKL and interleukin (IL)-17A production. Furthermore, local administration of VnP-16 in rats and mice significantly prevented and reversed alveolar bone loss induced by ligature-induced periodontitis. VnP-16 enhanced osteoblastogenesis and simultaneously inhibited osteoclastogenesis and suppressed RANKL and IL-17A expression in vivo.

CONCLUSIONS

Our findings suggest that VnP-16 acts as a potent therapeutic agent for preventing and treating periodontitis by regulating bone re-modelling and immune and inflammatory responses.

Physiological and histological studies of dental response of Luxate tooth with application of VEGF

Background During luxate injury many dental tissue will be involved including pulp, periodontal ligament ,mucosa, hard dental tissue and alveolar bone with affecting the nerve and dental blood supplement. Growth factors may involved in healing process after replantation of tooth in its socket and the  Vascular endothelial factor (VEGF )  is a potent one that increase angiogenesis and accelerate repairing  and healing of dental pulp and the supporting tissues. The study was designed to illustrate the effect of application of growth factor on healing process of luxate molar tooth of rat. Materials & Methods Twenty male Wistar rats with luxate lower right first molar teeth were included in this study. The control were injected  with normal saline (0.5μl ) around the apex of mesial root .Experimental  group injected with  VEGF (0.5μl ). Histological assessment of  physiological responses of (dental pulp, cementum, periodontal ligament (PDL) and alveolar bone in both control and experimental groups with Receptor activator of nuclear factor kappa-Β ligand (RANKL) expression  evaluation were recorded during the healing period in the examined tissue.

Extracellular Vesicles Derived From Murine Cementoblasts Possess the Potential to Increase Receptor Activator of Nuclear Factor-κB Ligand-Induced Osteoclastogenesis

Cementum resorption, unlike bone resorption, is clinically known to occur only with limited pathological stimuli, such as trauma, orthodontic forces, and large apical periodontitis; however, the molecular mechanisms that control osteoclast formation on the cementum surface remain unclear. In this study, we focused on extracellular vesicles (EVs) secreted by cementoblasts and analyzed their effects on osteoclast differentiation. EVs were extracted from the conditioned medium (CM) of the mouse cementoblast cell line OCCM-30. Transmission electron microscopy (TEM) analysis confirmed the presence of EVs with a diameter of approximately 50–200 nm. The effect of the EVs on osteoclast differentiation was examined using the mouse osteoclast progenitor cell line RAW 264.7 with recombinant receptor activator of nuclear factor (NF)-κB ligand (rRANKL) stimulation. EVs enhanced the formation of tartrate-resistant acid phosphatase (TRAP) activity-positive cells upon rRANKL stimulation. EVs also enhanced the induction of osteoclast-associated gene and protein expression in this condition, as determined by real-time PCR and Western blotting, respectively. On the other hand, no enhancing effect of EVs was observed without rRANKL stimulation. A Western blot analysis revealed no expression of receptor activator of NF-κB ligand (RANKL) in EVs themselves. The effect on rRANKL-induced osteoclast differentiation was examined using the CM of cementoblasts in terms of TRAP activity-positive cell formation and osteoclast-associated gene expression. The conditioned medium partly inhibited rRANKL-induced osteoclast differentiation and almost completely suppressed its enhancing effect by EVs. These results indicate that cementoblasts secreted EVs, which enhanced RANKL-induced osteoclast differentiation, and simultaneously produced soluble factors that neutralized this enhancing effect of EVs, implicating this balance in the regulation of cementum absorption. A more detailed understanding of this crosstalk between cementoblasts and osteoclasts will contribute to the development of new therapies for pathological root resorption.

The Crossroads of Periodontitis and Oral Squamous Cell Carcinoma: Immune Implications and Tumor Promoting Capacities

Periodontitis (PD) is increasingly considered to interact with and promote a number of inflammatory diseases, including cancer. In the case of oral squamous cell carcinoma (OSCC) the local inflammatory response associated with PD is capable of triggering altered cellular events that can promote cancer cell invasion and proliferation of existing primary oral carcinomas as well as supporting the seeding of metastatic tumor cells into the gingival tissue giving rise to secondary tumors. Both the immune and stromal components of the periodontium exhibit phenotypic alterations and functional differences during PD that result in a microenvironment that favors cancer progression. The inflammatory milieu in PD is ideal for cancer cell seeding, migration, proliferation and immune escape. Understanding the interactions governing this attenuated anti-tumor immune response is vital to unveil unexplored preventive or therapeutic possibilities. Here we review the many commonalities between the oral-inflammatory microenvironment in PD and oral-inflammatory responses that are associated with OSCC progression, and how these conditions can act to promote and sustain the hallmarks of cancer.

Can Plant Materials Be Valuable in the Treatment of Periodontal Diseases? Practical Review

Periodontal diseases are one of the most significant challenges in dental health. It is estimated that only a few percent of the worldwide population have entirely healthy teeth, and according to WHO, oral diseases may affect up to 3.5 billion people worldwide. One of the most serious oral diseases is periodontitis, an inflammatory disease affecting periodontal tissues, caused by pathogenic bacteria and environmental factors such as the ageing population, abuse of tobacco products, and lack of adequate oral hygiene due low public awareness. Plant materials are widely and successfully used in the management of many conditions, including periodontitis. Plant materials for periodontitis exhibit antibacterial, anti-inflammatory, antioxidant activities and affect the periodontium structure. Numerous studies demonstrate the advantages of phytotherapy for periodontitis relief and indicate the usefulness of Baikal skullcap root, Pomegranate fruit peel and root cortex, Tea leaves, Chamomile flowers, Magnolia bark, Blackberry leaves and fruits, Cranberry fruits and Lippia sidoides essential oil. This review aims to analyze the use and applicability of selected plant materials in periodontitis management since it is of paramount importance to evaluate the evidence of the traditionally used plant materials in light of continuously growing interest in phytotherapy and its adjuvant role in the treatment of periodontitis.

Differential involvement of the canonical and noncanonical inflammasomes in the immune response against infection by the periodontal bacteria Porphyromonas gingivalis and Fusobacterium nucleatum

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The canonical P2 × 7-Caspase-1 pathway is necessary for secretion of IL-1β in oral tissues and macrophages infected with P. gingivalis.

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P2 × 7 receptor controls bacterial load of F. nucleatum and P. gingivalis in macrophages and in mice.

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Caspase-11 is essential for F. nucleatum-induced secretion of IL-1β in macrophages, limits F. nucleatum infection in macrophages and in mice, and is required for cell death induced by F. nucleatum infection.

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The canonical inflammasome is activated preferentially in response to P. gingivalis infection, while the noncanonical inflammasome plays a predominant role during F. nucleatum infection.

We examined the involvement of the P2 × 7 receptor and the canonical and noncanonical inflammasomes in the control of single-species or dual-species infection by the periodontal bacteria Porphyromonas gingivalis and Fusobacterium nucleatum in cells and mice. Stimulation of the P2 × 7 receptor leads to activation of the canonical NLRP3 inflammasome and activation of caspase-1, which leads to cleavage of pro-IL-1β to IL-1β, a key cytokine in the host inflammatory response in periodontal disease. The non-canonical inflammasome pathway involves caspase-11. Thus, wildtype (WT), P2 × 7^−/−, caspase-11^−/− and caspase-1/11^−/− mice were co-infected with both bacterial species. In parallel, bone marrow-derived macrophages (BMDMs) from WT mice and the different knockout mice were infected with P. gingivalis and/or F. nucleatum, and treated or not with extracellular ATP, which is recognized by P2 × 7. F. nucleatum infection alone promoted secretion of IL-1β in BMDMs. Conversely, the canonical pathway involving P2 × 7 and caspase-1 was necessary for secretion of IL-1β in BMDMs infected with P. gingivalis and in the mandible of mice coinfected with P. gingivalis and F. nucleatum. The P2 × 7 pathway can limit bacterial load in single-species and dual-species infection with P. gingivalis and F. nucleatum in BMDMs and in mice. The non-canonical pathway involving caspase-11 was required for secretion of IL-1β induced by F. nucleatum infection in BMDMs, without treatment with ATP. Caspase-11 was also required for induction of cell death during infection with F. nucleatum and contributed to limiting bacterial load during F. nucleatum infection in BMDMs and in the gingival tissue of mice coinfected with P. gingivalis and F. nucleatum. Together, these data suggest that the P2 × 7-caspase-1 and caspase-11 pathways are involved in the immune response against infection by P. gingivalis and F. nucleatum, respectively.

The expression levels of MicroRNA-146a, RANKL and OPG after non-surgical periodontal treatment

Objective

MicroRNA-146a (miR-146a) is a regulator of inflammatory response. Periodontitis is a disease with immune pathophysiology of the periodontium in which the inflammation results in the destruction of the soft tissues and alveolar bone. Therefore, the aim of this study was to investigate the expressions of miR-146a, OPG, and RANKL in diseased and healthy periodontal tissues to understand whether miR-146a expression level may associate with OPG and RANKL mRNA levels and OPG/RANKL ratio after non-surgical periodontal treatment.

Methods

The levels of miR-146a, RANKL, and OPG in gingival tissues from patients with generalized periodontitis stages II and III and grades A and B (n = 15, group A), patients with generalized periodontitis stages III and IV and grade C (n = 15, group B), and healthy individuals (n = 10) were determined by real-time PCR. The associations of miR-146a expression with OPG and RANKL levels were evaluated.

Results

The levels of miR-146a in two subgroups within periodontitis patients were significantly higher than healthy subjects (P < 0.0001). MiR-146a showed the increased level in group A of patients compared with group B (P < 0.05). Clinical parameters such as probing depth (PD) and clinical attachment loss (CAL) were significantly higher in patients than control group (P < 0.05). The levels of OPG and RANKL were increased in patients compared with healthy subjects, although the elevated levels were not statistically significant. MiR-146a was not associated with OPG and RANKL levels and OPG/RANKL ratio.

Conclusions

The results of this study failed to show the associations of miR-146a level with OPG and RANKL levels and OPG/RANKL ratio in periodontitis after non-surgical periodontal treatment.

Association of NFKB1, NKX2-5, GATA4 and RANKL Gene Polymorphisms with Sporadic Congenital Heart Disease in Greek Patients

Congenital heart disease (CHD) is a group of structural defects of the heart and the great vessels, and one of the leading causes of death among infants and young adults. Several gene variants are involved in diverse mechanisms of cardiac and vessel development and could thus be considered candidate mutated genes for a congenital heart defect or a specific variant could predispose a person to CHD. In the present study, variants in four such genes are investigated for the first time in a group of young Greek CHD patients: the NFKB1 gene polymorphism (-94ins/ delATTG), rs28362491, NKX2-5 gene polymorphism rs2277923, GATA4 gene polymorphism rs11785481 and RANKL gene polymorphism rs4531631. A total of 43 CHD patients and 100 healthy adults were included in the study. The polymerase chain reaction-restriction fragment length polymorphism (PRC-RFLP) method was used to genotype the aforementioned polymorphisms of NFKB1, NKX2-5, GATA4 and RANKL. The association analysis identified that there was a protective association between CHD and the A allele of rs2277923 polymorphism (p = 0.004). The D allele of the rs28362491 polymorphism is also a likely risk factor for causing CHD (p = 0.006). The differences of the rs4531631 and rs11785481 variant contribution had no statistical significance between the groups (p >0.05). In conclusion, our results revealed that the rs28362491 and rs2277923 gene polymorphisms, but not the rs4531631 and rs11785481 polymorphisms, may contribute to CHD risk in a cohort of Greek CHD patients.

CpG immunostimulatory oligodeoxynucleotide 1826 as a novel nasal ODN adjuvant enhanced the protective efficacy of the periodontitis gene vaccine in a periodontitis model in SD rats

BACKGROUND

We previously demonstrated that nasal administration of periodontitis gene vaccine (pVAX1-HA2-fimA) or pVAX1-HA2-fimA plus IL-15 as adjuvant provoked protective immunity in the periodontal tissue of SD rats. This study evaluated the immune effect of pVAX1-HA2-fimA plus CpG-ODN 1826 as an adjuvant in the SD rat periodontitis models to improve the efficacy of the previously used vaccine.

METHODS

Periodontitis was induced in maxillary second molars in SD rats receiving a ligature and infected with Porphyromonas gingivalis. Forty-two SD rats were randomly assigned to six groups: A, control without P. gingivalis; B, P. gingivalis with saline; C, P. gingivalis with pVAX1; D, P. gingivalis with pVAX1-HA2-fimA; E, P. gingivalis with pVAX1-HA2-fimA/IL-15; F, P. gingivalis with pVAX1-HA2-fimA+CpG ODN 1826 (30 µg). The levels of FimA-specific and HA2-specific secretory IgA antibodies in the saliva of rats were measured by ELISA. The levels of COX-2 and RANKL were detected by immunohistochemical assay. Morphometric analysis was used to evaluate alveolar bone loss. Major organs were observed by HE staining.

RESULTS

30 μg could be the optimal immunization dose for CpG-ODN 1826 and the levels of SIgA antibody were consistently higher in the pVAX1-HA2-fimA+CpG-ODN 1826 (30 µg) group than in the other groups during weeks 1-8 (P < 0.05, except week 1 or 2). Morphometric analysis demonstrated that pVAX1-HA2-fimA+CpG-ODN 1826 (30 µg) significantly reduced alveolar bone loss in ligated maxillary molars in group F compared with groups B-E (P < 0.05). Immunohistochemical assays revealed that the levels of COX-2 and RANKL were significantly lower in group F compared with groups B-E (P < 0.05). HE staining results of the major organs indicated that pVAX1-HA2-fimA with or without CpG-ODN 1826 was not toxic for in vivo use.

CONCLUSIONS

These results indicated that CpG-ODN 1826 (30 µg) could be used as an effective and safe mucosal adjuvant for pVAX1-HA2-fimA in SD rats since it could elicit mucosal SIgA responses and modulate COX-2 and RANKL production during weeks 1-8, thereby inhibiting inflammation and decreasing bone loss.

RANKL and osteoimmunology in periodontitis

Periodontitis, one of the most common infectious diseases in humans, is characterized by inflammation of the periodontal tissue and subsequent destruction of the alveolar bone, which ultimately leads to tooth loss. Recently, it was revealed that the osteoclastic bone damage that occurs during periodontitis is dependent on the receptor activator of NF-kB ligand (RANKL) produced by osteoblastic cells and periodontal ligament cells. Immune cells provide essential cues for the RANKL induction that takes place during periodontal inflammation. The knowledge accumulated and experimental tools established in the field of "osteoimmunology" have made crucial contributions to a better understanding of periodontitis pathogenesis and, reciprocally, the investigation of periodontitis has provided important insights into the field. This review discusses the molecular mechanisms underlying periodontal bone loss by focusing on the osteoimmune interactions and RANKL.

Treatment of localized aggressive periodontitis alters local host immunoinflammatory profiles: A long-term evaluation

AIM

To evaluate the local immunoinflammatory profiles in localized aggressive periodontitis patients (LAP) before and after periodontal treatment and maintenance.

METHODS

Sixty-six African-Americans with LAP (7-21 years old) were included. After periodontal examination, all patients received periodontal treatment with mechanical debridement plus systemic amoxicillin/metronidazole for 7 days. Gingival crevicular fluid was collected from diseased and healthy sites at baseline and 3, 6, 12, and 24 months following treatment. Levels of 16 inflammatory/bone resorption markers were determined using Milliplex^® . Univariate and correlation analyses were performed among all parameters/biomarkers. Discriminant analyses (DA) evaluated profile differences between LAP diseased and healthy sites at each time point as compared to the baseline.

RESULTS

Reductions in the clinical parameters (except for visible plaque) were observed at all time points compared to the baseline. Levels of IL-12p70, IL-2, IL-6, MIP-1α, RANKL, and OPG were reduced after treatment, and several cytokines/chemokines were correlated with clinical parameters reductions. DA showed that differences in the immunoinflammatory profiles between LAP diseased and healthy sites decreased after periodontal treatment compared to the baseline.

CONCLUSIONS

Periodontal treatment modified the local immunoinflammatory profile of LAP sites in the long term, as suggested by changes in biomarkers from baseline, along with clinical stability of the disease. (Clinicaltrials.gov number, NCT01330719).

RANK/RANKL/OPG Signaling in the Brain: A Systematic Review of the Literature

Together with its dominant immunological and bone remodeling involvement, RRO axis, comprising of receptor activator of nuclear factor-κB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) signaling, is as well-implicated in CNS functioning and corresponding pathologies. The CNS aspects of RANKL/RANK/OPG (RRO) axis were systematically reviewed. With search 10 databases, and 7 additional resources from first article publication to July 2019, resulted in total 2,222 hits, from which 33 relevant articles were selected. The elements of RRO axis in CNS include cells involved in neuroinflammation, predominantly in microglia, but as well in resident macrophages and inflammatory cells migrating across the blood-brain barrier. The expression in neurons and oligodendrocytes is mainly confined to processes of differentiation and cell death. RRO axis tunes the neuroinflammatory response, depending on the molecular, cellular and pathological context. RANK/RANKL signaling is neuroprotective in TLR-mediated inflammation, while OPG seems detrimental in stroke, but beneficial in multiple sclerosis. The levels of RRO axis elements can serve as biomarkers in the blood and cerebrospinal fluid. They act as neuroprotectant after brain damage even being implicated in body weight- and thermo-regulation. As derivatives of RRO axis already exist as therapeutic agents in bone remodeling, it would be intriquing to see if these or new RRO-based pharmaceuticals would appear effective in CNS therapies.

Aging-Affected MSC Functions and Severity of Periodontal Tissue Destruction in a Ligature-Induced Mouse Periodontitis Model

Mesenchymal stem cells (MSCs) are known to play important roles in the repair of lost or damaged tissues and immunotolerance. On the other hand, aging is known to impair MSC function. However, little is currently known about how aged MSCs affect the host response to the local inflammatory condition and tissue deterioration in periodontitis, which is a progressive destructive disease of the periodontal tissue potentially leading to multiple tooth loss. In this study, we examined the relationship between aging-induced impairment of MSC function and the severity of periodontal tissue destruction associated with the decrease in host immunomodulatory response using a ligature-induced periodontitis model in young and aged mice. The results of micro computerized tomography (micro-CT) and histological analysis revealed a more severe bone loss associated with increased osteoclast activity in aged (50-week-old) mice compared to young (5-week-old) mice. Immunostaining analysis revealed that, in aged mice, the accumulation of inflammatory T and B cells was higher, whereas the percentage of platelet-derived growth factor receptor α (PDGFRα)⁺ MSCs, which are known to modulate the apoptosis of T cells, was significantly lower than in young mice. In vitro analysis of MSC function showed that the expression of surface antigen markers for MSCs (Sca-1, CD90, CD146), colony formation, migration, and osteogenic differentiation of aged MSCs were significantly declined compared to those of young MSCs. Moreover, a significantly higher proportion of aged MSCs were positive for the senescence-associated β galactosidase activity. Importantly, aged MSCs presented a decreased expression of FAS-L, which was associated with a lower immunomodulatory property of aged MSCs to induce T cell apoptosis in co-cultures compared with young MSCs. In summary, this is the first study showing that aging-induced impairment of MSC function, including immunomodulatory response, is potentially correlated with progressive periodontal tissue deterioration.

Vitamin D3 and Dental Mesenchymal Stromal Cells

Vitamin D3 is a hormone involved in the regulation of bone metabolism, mineral homeostasis, and immune response. Almost all dental tissues contain resident mesenchymal stromal cells (MSCs), which are largely similar to bone marrow-derived MSCs. In this narrative review, we summarized the current findings concerning the physiological effects of vitamin D3 on dental MSCs. The existing literature suggests that dental MSCs possess the ability to convert vitamin D3 into 25(OH)D3 and subsequently to the biologically active 1,25(OH)2D3. The vitamin D3 metabolites 25(OH)D3 and 1,25(OH)2D3 stimulate osteogenic differentiation and diminish the inflammatory response of dental MSCs. In addition, 1,25(OH)2D3 influences the immunomodulatory properties of MSCs in different dental tissues. Thus, dental MSCs are both producers and targets of 1,25(OH)2D3 and might regulate the local vitamin D3-dependent processes in an autocrine/paracrine manner. The local vitamin D3 metabolism is assumed to play an essential role in the local physiological processes, but the mechanisms of its regulation in dental MSCs are mostly unknown. The alteration of the local vitamin D3 metabolism may unravel novel therapeutic modalities for the treatment of periodontitis as well as new strategies for dental tissue regeneration.

Changes of Radiographic Trabecular Bone Density and Peri-Implant Marginal Bone Vertical Dimensions Around Non-Submerged Dental Implants with a Laser-Microtextured Collar after 5 Years of Functional Loading

Objectives:

The progressive peri-implant bone remodeling caused by dynamic cycles of microdamage may change peri-implant bone characteristics and volume after the functional loading.

This prospective study was designed to evaluate the radiographic trabecular bone density and peri-implant vertical dimensional changes around the non submerged dental implant with a laser-microtextured collar (NSLI)s after 5 years of functional loading.

Methods:

Digital periapical radiographs of 58 NSLIs supported fixed single crowns and fixed partial dentures in 26 patients (14 men, mean age of 52 ± 3.8 years) were used for comparative evaluation between the implant placement [Baseline (BSL)], the definitive Crowns Delivery (CD) and the 5 years post-functional loading examination (T5). Regions of interest (ROI) were taken into consideration for the measurement of mean gray levels, standard deviation, and variation coefficient. The texture parameters, such as contrast, correlation, angular second moment and entropy, were investigated by using the software ImageJ (v.1.50i), by means of the Gray-level Co-occurrence Matrix (GLCM) Texture Tool plugin. Vertical Peri-implant Marginal Bone Level (VPMBL) was assessed at the mesial and the distal sides of each implant by subtracting the measure at BSL from the measure at T5 by means of dedicate software (VixWin Platinum Imaging Software). Mixed regression models were adopted to analyze data. The possible effects of some variables, such as the use of provisional denture, location, crown/implant ratio, type of prosthetic design (single or splinted), on radiographic dimensional vertical changes, gray levels and texture analysis variables were also evaluated.

Results:

From BSL to T5, mesial and distal VPMBL showed a statistically significant gain of 0.9 ±0.5, and 0.10 mm ±0.6, respectively (P<0.05). From CD to T5, mean gray levels increased from 94.4±26.8) to 111.8±27.1 (P<0.05), while the coefficient of variation decreased from 0.08±0,03 to 0.05±0.04) (P<0.05). Variables showed no statistically significant correlation with texture parameters (P > 0.05).

Conclusion:

NSLIs showed an increase in radiographic vertical peri-implant marginal bone levels and bone density up to 5 years of loading.

Toll-Like Receptor Signaling and Immune Regulatory Lymphocytes in Periodontal Disease

Periodontitis is known to be initiated by periodontal microbiota derived from biofilm formation. The microbial dysbiotic changes in the biofilm trigger the host immune and inflammatory responses that can be both beneficial for the protection of the host from infection, and detrimental to the host, causing tissue destruction. During this process, recognition of Pathogen-Associated Molecular Patterns (PAMPs) by the host Pattern Recognition Receptors (PRRs) such as Toll-like receptors (TLRs) play an essential role in the host–microbe interaction and the subsequent innate as well as adaptive responses. If persistent, the adverse interaction triggered by the host immune response to the microorganisms associated with periodontal biofilms is a direct cause of periodontal inflammation and bone loss. A large number of T and B lymphocytes are infiltrated in the diseased gingival tissues, which can secrete inflammatory mediators and activate the osteolytic pathways, promoting periodontal inflammation and bone resorption. On the other hand, there is evidence showing that immune regulatory T and B cells are present in the diseased tissue and can be induced for the enhancement of their anti-inflammatory effects. Changes and distribution of the T/B lymphocytes phenotype seem to be a key determinant of the periodontal disease outcome, as the functional activities of these cells not only shape up the overall immune response pattern, but may directly regulate the osteoimmunological balance. Therefore, interventional strategies targeting TLR signaling and immune regulatory T/B cells may be a promising approach to rebalance the immune response and alleviate bone loss in periodontal disease. In this review, we will examine the etiological role of TLR signaling and immune cell osteoclastogenic activity in the pathogenesis of periodontitis. More importantly, the protective effects of immune regulatory lymphocytes, particularly the activation and functional role of IL-10 expressing regulatory B cells, will be discussed.

HIV-1-Infected Human Macrophages, by Secreting RANK-L, Contribute to Enhanced Osteoclast Recruitment

HIV-1 infection is frequently associated with low bone density, which can progress to osteoporosis leading to a high risk of fractures. Only a few mechanisms have been proposed to explain the enhanced osteolysis in the context of HIV-1 infection. As macrophages are involved in bone homeostasis and are critical host cells for HIV-1, we asked whether HIV-1-infected macrophages could participate in bone degradation. Upon infection, human macrophages acquired some osteoclast features: they became multinucleated, upregulated the osteoclast markers RhoE and β3 integrin, and organized their podosomes as ring superstructures resembling osteoclast sealing zones. However, HIV-1-infected macrophages were not fully differentiated in osteoclasts as they did not upregulate NFATc-1 transcription factor and were unable to degrade bone. Investigating whether infected macrophages participate indirectly to virus-induced osteolysis, we showed that they produce RANK-L, the key osteoclastogenic cytokine. RANK-L secreted by HIV-1-infected macrophages was not sufficient to stimulate multinucleation, but promoted the protease-dependent migration of osteoclast precursors. In conclusion, we propose that, by stimulating RANK-L secretion, HIV-1-infected macrophages contribute to create a microenvironment that favors the recruitment of osteoclasts, participating in bone disorders observed in HIV-1 infected patients.

S100A9 Increases IL-6 and RANKL Expressions through MAPKs and STAT3 Signaling Pathways in Osteocyte-Like Cells

Objective

Calprotectin is a heterocomplex of S100A8 and S100A9 and is mainly secreted from neutrophils, monocytes, and chondrocytes in inflammatory condition. Calprotectin binds to RAGE and TLR4 and induces the expression of proinflammatory chemokines and cytokines in various cells. Periodontitis is a chronic inflammatory disease that leads to gingival inflammation and alveolar bone resorption. Calprotectin levels in gingival crevicular fluid of periodontitis patients are higher than healthy patients. In the present study, the effects of S100A8 and S100A9 on the expressions of proinflammatory cytokines and bone metabolism-related factors in mouse osteocyte-like cells (MLO-Y4-A2) were investigated.

Design

MLO-Y4-A2 cells were treated with S100A8 and S100A9, and the expressions of RAGE, TLR4, RANKL, and several inflammatory cytokines were analyzed by PCR and Western blotting or ELISA methods. To investigate the intracellular signaling pathways, phosphorylation of MAPK and STAT3 was determined by Western blotting, and chemical specific inhibitors and siRNAs were used.

Results

Expressions of IL-6 and RANKL were increased by treatment with S100A9 but not S100A8. However, both S100A8 and S100A9 did not change expression of IL-1β, IL-8, and TNF-α. Although RAGE and TLR4 expressions were not upregulated by S100A9 treatment, transfection of siRNA for RAGE and TLR4 significantly decreased IL-6 and RANKL expressions. In addition, S100A9 activated p38, ERK, and STAT3 signaling pathways, and inhibitors for these factors significantly decreased S100A9-induced IL-6 and RANKL expressions.

Conclusions

These results indicated that S100A9 induces IL-6 and RANKL production via engagement with RAGE and TLR4 signalings in osteocytes and suggested that S100A9 may play important roles in the periodontal alveolar bone destruction.

Assessment of Salivary Levels of RANKL and OPG in Aggressive versus Chronic Periodontitis

RANKL (receptor activator of nuclear factor kappa-β ligand) and OPG (osteoprotegerin) are two proteins involved in bone remodelling. During the active phase of periodontal disease, an imbalance between the ratios of the two elements can be noticed. While the expression of RANKL is elevated compared with that of OPG, the RANKL is available to bond with RANK (receptor activator of nuclear factor kappa-β). This study was conducted on 41 patients: 19 with generalized aggressive periodontitis, 18 with severe chronic periodontitis, and 4 periodontal healthy subjects. For each patient included, we determined the salivary levels of RANKL and OPG with the help of two Human ELISA kits. The results show that the patients affected by periodontitis, either aggressive or chronic, have significant higher values of RANKL and RANKL/OPG ratio. This values correlate with the local inflammation status.

Antiperiodontitis Effects of Magnolia biondii Extract on Ligature-Induced Periodontitis in Rats

Over the past decades, periodontitis has become a rising health problem and caused various diseases. In the many studies shows that some extracts and compound to the prevention and treatment of periodontitis. This study focuses on the effects of inhibition of gingival damage and alveolar bone loss. The aim of this study was to evaluate the protective effects of Magnolia biondii extract (MBE) against ligature-induced periodontitis in rats. A ligature was placed around the molar teeth for 8 weeks, and MBE was administered for 8 weeks. Gingival tissue damage and alveolar bone loss were measured by microcomputed tomography (CT) analysis and histopathological examination. Serum Interluekin-1 β (IL-1β), tumor necrosis factor-α (TNF-α), cyclooxygenases-2 (COX-2), and receptor activator of nuclear factor-κB ligand (RANKL) levels were investigated using commercial kits to confirm the antiperiodontitis effects of MBE. We confirmed that ligature-induced periodontitis resulted in gingival tissue damage and alveolar bone loss. However, treatment for 8 weeks with MBE protected from periodontal tissue damage and downregulated serum inflammatory cytokine factors and RANKL levels. These results suggest that MBE exerts antiperiodontitis effects by inhibiting gingival tissue destruction and alveolar bone loss through regulation of anti-inflammatory cytokines in periodontitis-induced rats.

Production of Soluble Receptor Activator of Nuclear Factor Kappa-Β Ligand and Osteoprotegerin by Apical Periodontitis Cells in Culture and Their Modulation by Cytokines

RANKL, a bone-destructive cytokine, and OPG, its osteoprotective counterpart, are expressed in periapical lesions (PLs), which represent hystopatological manifestations of apical periodontitis. However, their regulation in PLs has not been elucidated yet. Therefore, our aim was to study the production of RANKL and OPG and their modulation by pro- and anti-inflammatory cytokines in PL cell cultures. Isolated PL cells were cultured alone or with addition of TNF-α, IFN-ϒ, IL-17, IL-4, IL-10, and IL- 33, respectively. The levels of RANKL and OPG in supernatants were measured by ELISA. The proportion of CD3⁺ (T cells) and CD19+/CD138+ (B cells/plasma cells) within isolated PLs was determined by immunocytochemistry. The levels of RANKL were higher in cultures of symptomatic PLs compared to asymptomatic PLs and PLs with the dominance of T cells (T-type lesions) over B cells/plasma cells (B-type lesions). A higher proportion of osteodestructive processes (RANKL/OPG ratio > 1.0) were detected in symptomatic PLs. The production of RANKL was upregulated by IFN-ϒ and IL-17 and higher concentrations of IL-33. IL-10 and lower concentrations of IL-33 augmented the production of OPG. The addition of either RANKL or anti-RANKL antibody to the cultures did not modify significantly the production of OPG. In conclusion, this original PL cell culture model suggests that increased bone destruction through upregulated production of RANKL could be associated with exacerbation of inflammation in PLs with the predominance of Th1 and Th17 responses and increased secretion of IL-33. In contrast, IL-10 and lower levels of IL-33, through upregulation of OPG, may suppress osteolytic processes.

Host defense against oral microbiota by bone-damaging T cells

The immune system evolved to efficiently eradicate invading bacteria and terminate inflammation through balancing inflammatory and regulatory T-cell responses. In autoimmune arthritis, pathogenic T_H17 cells induce bone destruction and autoimmune inflammation. However, whether a beneficial function of T-cell-induced bone damage exists is unclear. Here, we show that bone-damaging T cells have a critical function in the eradication of bacteria in a mouse model of periodontitis, which is the most common infectious disease. Bacterial invasion leads to the generation of specialized T_H17 cells that protect against bacteria by evoking mucosal immune responses as well as inducing bone damage, the latter of which also inhibits infection by removing the tooth. Thus, bone-damaging T cells, which may have developed to stop local infection by inducing tooth loss, function as a double-edged sword by protecting against pathogens while also inducing skeletal tissue degradation.

Tumor necrosis factor-α antagonist diminishes osteocytic RANKL and sclerostin expression in diabetes rats with periodontitis

Type 1 diabetes with periodontitis shows elevated TNF-α expression. Tumor necrosis factor (TNF)-α stimulates the expression of receptor activator of nuclear factor-κB ligand (RANKL) and sclerostin. The objective of this study was to determine the effect of TNF-α expression of osteocytic RANKL and sclerostin in type 1 diabetes rats with periodontitis using infliximab (IFX), a TNF-α antagonist. Rats were divided into two timepoint groups: day 3 and day 20. Each timepoint group was then divided into four subgroups: 1) control (C, n = 6 for each time point); 2) periodontitis (P, n = 6 for each time point); 3) diabetes with periodontitis (DP, n = 8 for each time point); and 4) diabetes with periodontitis treated with IFX (DP+IFX, n = 8 for each time point). To induce type 1 diabetes, rats were injected with streptozotocin (50 mg/kg dissolved in 0.1 M citrate buffer). Periodontitis was then induced by ligature of the mandibular first molars at day 7 after STZ injection (day 0). IFX was administered once for the 3 day group (on day 0) and twice for the 20 day group (on days 7 and 14). The DP group showed greater alveolar bone loss than the P group on day 20 (P = 0.020). On day 3, higher osteoclast formation and RANKL-positive osteocytes in P group (P = 0.000 and P = 0.011, respectively) and DP group (P = 0.006 and P = 0.017, respectively) than those in C group were observed. However, there was no significant difference in osteoclast formation or RANKL-positive osteocytes between P and DP groups. The DP+IFX group exhibited lower alveolar bone loss (P = 0.041), osteoclast formation (P = 0.019), and RANKL-positive osteocytes (P = 0.009) than that of the DP group. On day 20, DP group showed a lower osteoid area (P = 0.001) and more sclerostin-positive osteocytes (P = 0.000) than P group. On days 3 and 20, the DP+IFX group showed more osteoid area (P = 0.048 and 0.040, respectively) but lower sclerostin-positive osteocytes (both P = 0.000) than DP group. Taken together, these results suggest that TNF-α antagonist can diminish osteocytic RANKL/sclerostin expression and osteoclast formation, eventually recovering osteoid formation. Therefore, TNF-α might mediate alveolar bone loss via inducing expression of osteocytic RANKL and sclerostin in type 1 diabetes rats with periodontitis.

Kava-241 reduced periodontal destruction in a collagen antibody primed Porphyromonas gingivalis model of periodontitis

AIM

The aim of this study was to evaluate the effect of Kava-241, an optimized Piper methysticum Kava compound, on periodontal destruction in a collagen antibody primed oral gavage model of periodontitis.

METHODS

Experimental periodontitis was induced by oral gavage of Porphyromonas gingivalis (P. gingivalis) + type II collagen antibody (AB) in mice during 15 days. Mice were treated with Kava-241 concomitantly or prior to P. gingivalis gavage and compared to untreated mice. Comprehensive histomorphometric analyses were performed.

RESULTS

Oral gavage with P. gingivalis induced mild epithelial down-growth and alveolar bone loss, while oral gavage with additional AB priming had greater tissular destruction in comparison with gavage alone (p < .05). Kava-241 treatment significantly (p < .05) reduced epithelial down-growth (72%) and alveolar bone loss (36%) in P. gingivalis+AB group. This Kava-241 effect was associated to a reduction in inflammatory cell counts within soft tissues and an increase in fibroblasts (p < .05).

CONCLUSION

Priming with type II collagen antibody with oral gavage is a fast and reproducible model of periodontal destruction adequate for the evaluation of novel therapeutics. The effect of Kava-241 shows promise in the prevention and treatment of inflammation and alveolar bone loss associated with periodontitis. Further experiments are required to determine molecular pathways targeted by this therapeutic agent.

The Cell Surface Markers Expression in Postmenopausal Women and Relation to Obesity and Bone Status

The age-related changes and hormonal deprivation in postmenopausal women are associated with the immune response alteration. The excessive fat accumulation, local and systemic inflammation may lead to dysregulation in immune function and relevant health problems, including obesity and osteoporosis. We analyzed the expression of cell surface markers in the venous blood specimens, stained with fluorophores-conjugated monoclonal antibodies and analysed by multicolour flow cytometry. The significant changes of cytotoxic, naive, and memory T-lymphocytes, plasmacytoid dendritic cells (DCs) were in postmenopausal women versus fertile women. Body mass index (BMI) affected markedly the cell surface expression of CD265/RANK. Osteoporosis is linked to reduced percentage of plasmacytoid DCs, and elevated natural Treg cells (p < 0.05). The confounding factors such as women age, BMI, bone mineral density (BMD), waist size and tissue fat affect the expression of RANK on myeloid DCs and CD40L on T-lymphocytes that might be the immunophenotypic modulators after menopause.

OCLI-023, a Novel Pyrimidine Compound, Suppresses Osteoclastogenesis In Vitro and Alveolar Bone Resorption In Vivo

An abnormal increase in osteoclast differentiation and activation results in various bone-resorptive diseases, including periodontitis, rheumatoid arthritis, and osteoporosis. Chemical compounds containing pyrimidine ring have been shown to regulate a variety of biological processes. Therefore, in order to identify an antiresorptive agent, we synthesized a series of pyrimidine ring-containing chemical compounds, and found that OCLI-023 suppressed the differentiation and activation of osteoclasts in vitro. OCLI-023 directly inhibited receptor activator of nuclear factor-κB ligand (RANKL)-induced differentiation of bone marrow macrophages into osteoclasts, without a cytotoxic response. OCLI-023 also downregulated the RANKL-induced mRNA expression of osteoclast markers as well as inhibited the formation of actin rings and resorption pits. OCLI-023 attenuated the RANKL-induced activation of c-Jun N-terminal kinase and nuclear factor kappa-light-chain-enhancer of activated B cell signaling pathways. In a mouse model of periodontitis, ligature induced an increase of distance between cementoenamel junction (CEJ) and alveolar bone crest (ABC) in the second molar, and OCLI-023 significantly reduced it. Histological analysis showed ligature-induced increase of osteoclast numbers was also significantly reduced by OCLI-023. These data demonstrated the inhibitory effect of OCLI-023 on osteoclast differentiation and activity of osteoclasts in vitro, as well as on ligature-induced bone loss in vivo, and OCLI-023 can be proposed as a novel anti-resorptive compound.

A Modified Glycosaminoglycan, GM-0111, Inhibits Molecular Signaling Involved in Periodontitis

Background

Periodontitis is characterized by microbial infection, inflammation, tissue breakdown, and accelerated loss of alveolar bone matrix. Treatment targeting these multiple stages of the disease provides ways to treat or prevent periodontitis. Certain glycosaminoglycans (GAGs) block multiple inflammatory mediators as well as suppress bacterial growth, suggesting that these GAGs may be exploited as a therapeutic for periodontitis.

Methods

We investigated the effects of a synthetic GAG, GM-0111, on various molecular events associated with periodontitis: growth of Porphyromonas gingivalis (P. gingivalis) and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) pathogenic bacteria associated with periodontitis; activation of pro-inflammatory signaling through TLR2 and TLR4 in mouse macrophage RAW 264.7 cells and heterologously expressed HEK 293 cells; osteoclast formation and bone matrix resorption in cultured mouse pre-osteoclasts.

Results

(1) GM-0111 suppressed the growth of P. gingivalis and A. actinomycetemcomitans even at 1% (w/v) solution. The antibacterial effects of GM-0111 were stronger than hyaluronic acid (HA) or xylitol in P. gingivalis at all concentrations and comparable to xylitol in A. actinomycetemcomitans at ≥2% (w/v) solution. We also observed that GM-0111 suppressed biofilm formation of P. gingivalis and these effects were much stronger than HA. (2) GM-0111 inhibited TLR-mediated pro-inflammatory cellular signaling both in macrophage and HEK 293 cells with higher selectivity for TLR2 than TLR4 (IC₅₀ of 1–10 ng/mL vs. > 100 μg/mL, respectively). (3) GM-0111 blocked RANKL-induced osteoclast formation (as low as 300 ng/mL) and bone matrix resorption. While GM-0111 showed high affinity binding to RANKL, it did not interfere with RANKL/RANK/NF-κB signaling, suggesting that GM-0111 inhibits osteoclast formation by a RANKL-RANK-independent mechanism.

Conclusions

We report that GM-0111 inhibits multiple molecular events involved in periodontitis, spanning from the early pro-inflammatory TLR signaling, to pathways activated at the later stage component of bone loss.

Osteoclasts-Key Players in Skeletal Health and Disease

The differentiation of osteoclasts (OCs) from early myeloid progenitors is a tightly regulated process that is modulated by a variety of mediators present in the bone microenvironment. Once generated, the function of mature OCs depends on cytoskeletal features controlled by an αvβ3-containing complex at the bone-apposed membrane and the secretion of protons and acid-protease cathepsin K. OCs also have important interactions with other cells in the bone microenvironment, including osteoblasts and immune cells. Dysregulation of OC differentiation and/or function can cause bone pathology. In fact, many components of OC differentiation and activation have been targeted therapeutically with great success. However, questions remain about the identity and plasticity of OC precursors and the interplay between essential networks that control OC fate. In this review, we summarize the key principles of OC biology and highlight recently uncovered mechanisms regulating OC development and function in homeostatic and disease states.

Expression of SOFAT by T- and B-lineage cells may contribute to bone loss

A novel T cell-secreted cytokine, termed secreted osteoclastogenic factor of activated T cells (SOFAT) that induces osteoclastic bone resorption in a RANKL-independent manner, has been described. Our group have previously reported that SOFAT is highly expressed in gingival tissues of patients with chronic periodontitis suggesting a putative role in the bone loss associated with periodontal disease. The aim of the present study was to identify other potential cellular sources of SOFAT in the bone resorptive lesions of patients with periodontal disease. Gingival tissues were biopsied from systemically healthy subjects without periodontal disease (n=5) and patients with chronic periodontitis (n=5), and the presence of SOFAT was analyzed by immunohistochemistry and immunofluorescence staining. The present data demonstrated marked SOFAT staining in diseased periodontal tissues that was predominantly associated with the lymphocytic infiltration of gingival tissues. Notably, in addition to CD3+ T cells, B‑lineage cells including plasma cells also exhibited strong staining for SOFAT. As SOFAT has not previously been reported in B‑lineage cells, splenic T cells and B cells were further purified from BALB/c mice and activated using CD3/CD28 and lipopolysaccharide, respectively. SOFAT was quantified by reverse transcription‑quantitative polymerase chain reaction and was shown to be significantly expressed (P<0.05) in both activated T cells and B cells compared with unstimulated cells. These data support a putative role of SOFAT in the bone loss associated with chronic periodontal disease. In addition, to the best of our knowledge, this study demonstrates for the first time that in addition to T cells, B-lineage cells may also be a significant source of SOFAT in inflammatory states.

Influence of Type 2 Diabetes on Prevalence of Key Periodontal Pathogens, Salivary Matrix Metalloproteinases, and Bone Remodeling Markers in Sudanese Adults with and without Chronic Periodontitis

This study compared the influence of type 2 diabetes on the occurrence of six periodontal pathogens in plaque samples of patients with and without chronic periodontitis. Levels of salivary MMP-8, MMP-9, RANKL, and OPG were also investigated. The study enrolled 31 patients with type 2 diabetes and chronic periodontitis (DM + CP), 29 with chronic periodontitis (CP), and 20 with type 2 diabetes (DM). Questionnaire-guided interviews were conducted and plaque index, bleeding on probing, and pocket depth were recorded. Polymerase chain reaction (PCR) was utilized to determine the prevalence of the bacteria. The levels of salivary molecules were determined by enzyme immunosorbent assay (ELISA). The CP group had the highest prevalence of P. gingivalis (81.5%), followed by the DM + CP (59.3%) and DM (55.0%) groups (P > 0.05). Similar trends were observed for P. intermedia and T. denticola. The prevalence of T. forsythia was 100% in both periodontitis groups compared to 90% in the DM group. There were no significant differences between the groups regarding the concentrations of MMP-8, MMP-9, or OPG. RANKL concentrations were below the detection limit. Our data show that type 2 diabetes has no significant influence on the prevalence of the investigated periodontal pathogens, or the levels of salivary MMP-8, MMP-9, and OPG.

Thymosin Beta-4 Suppresses Osteoclastic Differentiation and Inflammatory Responses in Human Periodontal Ligament Cells

Background

Recent reports suggest that thymosin beta-4 (Tβ4) is a key regulator for wound healing and anti-inflammation. However, the role of Tβ4 in osteoclast differentiation remains unclear.

Purpose

The purpose of this study was to evaluate Tβ4 expression in H₂O₂-stimulated human periodontal ligament cells (PDLCs), the effects of Tβ4 activation on inflammatory response in PDLCs and osteoclastic differentiation in mouse bone marrow-derived macrophages (BMMs), and identify the underlying mechanism.

Methods

Reverse transcription-polymerase chain reactions and Western blot analyses were used to measure mRNA and protein levels, respectively. Osteoclastic differentiation was assessed in mouse bone marrow-derived macrophages (BMMs) using conditioned medium (CM) from H₂O₂-treated PDLCs.

Results

Tβ4 was down-regulated in H₂O₂-exposed PDLCs in dose- and time-dependent manners. Tβ4 activation with a Tβ4 peptide attenuated the H₂O₂-induced production of NO and PGE₂ and up-regulated iNOS, COX-2, and osteoclastogenic cytokines (TNF-α, IL-1β, IL-6, IL-8, and IL-17) as well as reversed the effect on RANKL and OPG in PDLCs. Tβ4 peptide inhibited the effects of H₂O₂ on the activation of ERK and JNK MAPK, and NF-κB in PDLCs. Furthermore, Tβ4 peptide inhibited osteoclast differentiation, osteoclast-specific gene expression, and p38, ERK, and JNK phosphorylation and NF-κB activation in RANKL-stimulated BMMs. In addition, H₂O₂ up-regulated Wnt5a and its cell surface receptors, Frizzled and Ror2 in PDLCs. Wnt5a inhibition by Wnt5a siRNA enhanced the effects of Tβ4 on H₂O₂-mediated induction of pro-inflammatory cytokines and osteoclastogenic cytokines as well as helping osteoclastic differentiation whereas Wnt5a activation by Wnt5a peptide reversed it.

Conclusion

In conclusion, this study demonstrated, for the first time, that Tβ4 was down-regulated in ROS-stimulated PDLCs as well as Tβ4 activation exhibited anti-inflammatory effects and anti-osteoclastogenesis in vitro. Thus, Tβ4 activation might be a therapeutic target for inflammatory osteolytic disease, such as periodontitis.

Osteoblast Lineage Cells Play an Essential Role in Periodontal Bone Loss Through Activation of Nuclear Factor-Kappa B

Bacterial pathogens stimulate periodontitis, the most common osteolytic disease in humans and the most common cause of tooth loss in adults. Previous studies identified leukocytes and their products as key factors in this process. We demonstrate for the first time that osteoblast lineage cells play a critical role in periodontal disease. Oral infection stimulated nuclear localization of NF-κB in osteoblasts and osteocytes in the periodontium of wild type but not transgenic mice that expressed a lineage specific dominant negative mutant of IKK (IKK-DN) in osteoblast lineage cells. Wild-type mice were also susceptible to bacteria induced periodontal bone loss but transgenic mice were not. The lack of bone loss in the experimental group was linked to reduced RANKL expression by osteoblast lineage cells that led to diminished osteoclast mediated bone resorption and greater coupled new bone formation. The results demonstrate that osteoblast lineage cells are key contributors to periodontal bone loss through an NF-κB mediated mechanism.

Genes related to inflammation and bone loss process in periodontitis suggested by bioinformatics methods

BACKGROUND

Despite of numerous studies on periodontitis, the mechanism underlying the progression of periodontitis still remains largely unknown. This study aimed to have an expression profiling comparison between periodontitis and normal control and to identify more candidate genes involved in periodontitis and to gain more insights into the molecular mechanisms of periodontitis progression.

METHODS

The gene expression profile of GSE16134, comprising 241 gingival tissue specimens and 69 healthy samples as control which were obtained from 120 systemically healthy patients with periodontitis (65 with chronic and 55 with aggressive periodontitis), was downloaded from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) in periodontitis samples were screened using the limma package in R compared with control samples. Gene Ontology (GO) and pathway enrichment analysis upon the DEGs were carried out using Hypergeometric Distribution test. Protein-protein interaction (PPI) network of the DEGs was constructed using Cytoscape, followed by module selection from the PPI network using MCODE plugin. Moreover, transcription factors (TFs) of these DEGs were identified based on TRANSFAC database and then a regulatory network was constructed.

RESULTS

Totally, 762 DEGs (507 up- and 255 down-regulated) in periodontitis samples were identified. DEGs were enriched in different GO terms and pathways, such as immune system process, cell activation biological processes, cytokine-cytokine receptor interaction, and metabolic pathways. Cathepsin S (CTSS) and pleckstrin (PLEK) were the hub proteins in the PPI network and 3 significant modules were selected. Moreover, 19 TFs were identified including interferon regulatory factor 8 (IRF8), and FBJ murine osteosarcoma viral oncogene homolog B (FOSB).

CONCLUSION

This study identified genes (CTSS, PLEK, IRF-8, PTGS2, and FOSB) that may be involved in the development and progression of periodontitis.