Review of osteoimmunology and the host response in endodontic and periodontal lesions

Osteoimmunology of tumor necrosis factor-alpha, IL-6, and RANTES/CCL5: a review of known and poorly understood inflammatory patterns in osteonecrosis

Background

The immune and bone systems are closely linked via cytokine cross-talk. This interdisciplinary field of research is referred to as osteoimmunology and pertains to inflammatory and osteoarticular diseases that feature the primary expression of tumor necrosis factor-alpha (TNF-α) and IL-6.

Objective

Are there bone resorptive processes wherein chronic inflammatory conditions are not linked to TNF-α and IL-6 expression, but rather to the expression of other cytokines?

Materials and methods

A comprehensive literature search was performed in PubMed Central.

Discussion

Although all diseases with cytokines involved in bone resorption (TNF-α and IL-6) are at the forefront of destructive inflammatory processes, there is one exception in the literature: fatty oxide osteoporosis/osteolysis in the jawbone (FDOJ), which is associated with significant bone softening. However, it should be noted that TNF-α and IL-6 fall below the levels found in a healthy jawbone in this condition. Another conspicuous finding is that there is a nearly 35-fold overexpression of the chemokine RANTES/CCL5 (R/C) in all FDOJ cases studied thus far in the literature.

Conclusion

FDOJ appears to represent a unique cytokine and inflammatory pattern from osteolysis in the body. R/C can be defined as the dominant carrier of a “maxillomandibular osteoimmunology”.

Streptococcus gordonii induces bone resorption by increasing osteoclast differentiation and reducing osteoblast differentiation

Streptococcus gordonii is commonly found in the periapical endodontic lesions of patients with apical periodontitis, a condition characterized by inflammation and periapical bone loss. Since bone metabolism is controlled by osteoclastic bone resorption and osteoblastic bone formation, we investigated the effects of S. gordonii on the differentiation and function of osteoclasts and osteoblasts. For the determination of bone resorption activity in vivo, collagen sheets soaked with heat-killed S. gordonii were implanted on mouse calvaria, and the calvarial bones were scanned by micro-computed tomography. Mouse bone marrow-derived macrophages (BMMs) were stimulated with M-CSF and RANKL for 2 days and then differentiated into osteoclasts in the presence or absence of heat-killed S. gordonii. Tartrate-resistant acid phosphatase staining was performed to determine osteoclast differentiation. Primary osteoblast precursors were differentiated into osteoblasts with ascorbic acid and β-glycerophosphate in the presence or absence of heat-killed S. gordonii. Alkaline phosphatase staining and alizarin red S staining were conducted to determine osteoblast differentiation. Western blotting was performed to examine the expression of transcription factors including c-Fos, NFATc1, and Runx2. Heat-killed S. gordonii induced bone destruction in a mouse calvarial implantation model. The differentiation of RANKL-primed BMMs into osteoclasts was enhanced in the presence of heat-killed S. gordonii. Heat-killed S. gordonii increased the expression of c-Fos and NFATc1, which are essential transcription factors for osteoclast differentiation. On the other hand, heat-killed S. gordonii inhibited osteoblast differentiation and reduced the expression of Runx2, an essential transcription factor for osteoblast differentiation. S. gordonii exerts bone resorptive activity by increasing osteoclast differentiation and reducing osteoblast differentiation, which may be involved in periapical bone resorption.

Effect of root canal debridement on inflammatory cytokine levels

In endodontic infections, inflammatory mediators such as cytokines are released, recruited and retained until the infection is eradicated. Root canal therapy is performed to prevent the spread of infection. The aim of this study was to investigate the effects of root canal debridement (cleaning and shaping) on periapical inflammation by measuring the levels of inflammatory cytokines, Interleukin-8 (IL-8) and Interleukin-10 (IL-10). The study includes twenty patients with pulp necrosis and asymptomatic apical periodontitis. Periradicular sample was collected using paper points before and after root canal debridement. Cytokine levels were determined by Sandwich Enzyme-Linked Immunosorbent Assay (ELISA). Data were analysed using paired t-test (PASW Statistics 18) (P = 0.05). All samples showed the presence of IL-8 and IL-10 prior to root canal debridement. Significantly reduced levels (P < 0.05) of IL-8 and IL-10 were detected after root canal debridement. In conclusion, root canal debridement significantly decreased the levels of the tested pro- and anti-inflammatory cytokine in the periradicular interstitial fluid.

Immune response mediated by Th1 / IL-17 / caspase-9 promotes evolution of periodontal disease

INTRODUCTION

Periodontitis is characterized by inflammatory mediators beyond T lymphocyte function and phenotype (Th1/Th2/Th17). The clinical diversity in periodontitis makes it difficult to characterize the immune response in patients. This study evaluated the profile of the adaptive immune response in the periodontal disease model.

METHODS

72 rats (Wistar) were divided into a control group (CTL/day 0) and periodontitis (PD15/15 days and PD60/60 days). In the PD15 and PD60 groups, periodontal disease was induced by ligature with a silk thread placed in the cervical region of the upper first molar. After euthanasia, the periodontal tissue was analyzed by flow cytometry (CD4, CD8, CD25, CD44), semi-quantitative RT-PCR (T-bet, GATA-3, RORγt), semi-quantitative RT-PCR and ELISA IFN-γ, TNF-α, IFN-γ, IL-4, IL-6, IL-10, IL-17) and by Western blotting (Caspase-9, PCNA).

RESULTS

The number of CD4⁺CD25⁺, CD4⁺CD44⁺, CD8⁺CD25⁺ and CD8⁺CD44⁺ cells and expression levels of T-bet and GATA-3 are increased in the PD60 group compared to PD15 and CTL. The RORγ-t gene transcript increased in the PD15 group in relation to PD60 and CTL. The cytokines IFN-γ, TNF-α and IL-17 increased in the PD60 group in relation to PD15. The expression of Caspase-9 was higher in the PD60 group than in PD15.

CONCLUSIONS

The results suggest that the evolution of gingivitis to periodontitis is related to the accumulation of activated Th1 cells (IFN-γ and TNF-α) associated with the presence of increased IL-17. Studies with inhibitors of these cytokines in periodontal disease may lead to therapy directed at blocking the inflammatory process in this pathology, interrupting bone loss.

Sexual Dimorphism in Immunity to Oral Bacterial Diseases: Intersection of Neutrophil and Osteoclast Pathobiology

Sex is a biological variable that affects immune responses to bacterial and other types of infectious agents. Males and females are known to have differential oral bacterial disease burden in periodontal and endodontic disease. Understanding that there is a contribution from both sex and gender to these oral diseases, we discuss in this review recent sex-based findings that provide a pathobiological basis for differences observed between males and females. Sexual dimorphism of immune responses with respect to neutrophil trafficking and osteoclast differentiation and formation is presented as a plausible mechanism to explain the sexual differences. We also emphasize that sex, as a biological variable, should be considered in these types of oral immunologic studies.

Evolution of Periodontal Disease: Immune Response and RANK/RANKL/OPG System

The aim of this study was to evaluate markers of bone loss and immune response present in evolution of periodontal disease. One hundred and two Wistar rats were divided into three animals groups: PD0, without ligation and PD15 days and PD60 days, submitted to ligation placement with a sterile 3-0 silk cord in the cervical region of the upper first molar on both sides. Samples were obtained from the gingival tissue for histomorphometric analysis, immunohistochemical analysis of RANK, RANKL, OPG, characterization of the inflammatory infiltrate, quantification of nitric oxide, MCP-1, RANTES, IP10 chemokines, and expression of the TGF-b1, VEG, and bFGF. The number of inflammatory cells in gingival tissue was higher in PD60 samples. The collagen content and the area occupied by birefringent collagen fibers were lower for PD60. Differential leukocyte counting showed that there was a significantly higher polymorphonuclear influx in group PD15, while PD60 showed a greater number of lymphocytes. PD60 showed higher RANTES, IP-10, MCP-1 gene transcripts, as well as a higher nitric oxide concentration. Clinical evaluation revealed that the PD60 group presented an increase in furcal area. In conclusion, in this animal model the increase of RANK/RANKL and HGF markers is related to a specific immune response, and probably contributed to the evolution of periodontal disease. Investigating the effect of these biomarkers can help in targeted therapy for bone resorption, since blocking these can inhibit bone loss.

The Effect of Cyanobacterial LPS Antagonist (CyP) on Cytokines and Micro-RNA Expression Induced by Porphyromonas gingivalis LPS

Lipopolysaccharide (LPS) from Porphyromonas gingivalis (Pg-LPS) is a key bacterial structure involved in the maintenance of a chronic pro-inflammatory environment during periodontitis. Similar to other gram-negative LPS, Pg-LPS induces the release of pro-inflammatory cytokines through interaction with Toll-Like Receptor 4 (TLR4) and is able to stimulate negative TLR4 regulatory pathways, such as those involving microRNA (miRNA). In this work, we employed CyP, an LPS with TLR4-MD2 antagonist activity obtained from the cyanobacterium Oscillatoria planktothrix FP1, to study the effects on pro-inflammatory cytokine production and miRNA expression in human monocytic THP-1 cells stimulated with Pg-LPS or E. coli LPS (Ec-LPS). Results showed that CyP inhibited TNF-α, IL-1β and IL-8 expression more efficiently when co-incubated with Pg-LPS rather than with Ec-LPS. The inhibition of pro-inflammatory cytokine production was maintained even when CyP was added 2 h after LPS. The analysis of the effects of CyP on miRNA expression showed that, although being an antagonist, CyP did not inhibit miR-146a induced by Pg-LPS or Ec-LPS, whereas it significantly inhibited miR-155 only in the cultures stimulated with Ec-LPS. These results suggest that CyP may modulate the pro-inflammatory response induced by Pg-LPS, not only by blocking TLR4-MD2 complex, but also by preserving miR-146a expression.

DNA methylation profiles of immune response-related genes in apical periodontitis

AIM

To investigate the DNA methylation profiles of immune response-related genes in apical periodontitis (AP) lesions.

METHODOLOGY

The methylation profiles on the cytosine-phosphate-guanine (CpG) regions of 22 gene promoters involved in inflammation and autoimmunity were assessed in 60 human AP lesions and 24 healthy periodontal ligaments (controls) using a pathway-specific real-time polymerase chain reaction array (EpiTect® Methyl Signature PCR Array Human Inflammatory Response). Differentially methylated genes were subsequently assessed for their mRNA expression. Data analyses (One-way anova, Tukey's multiple comparisons tests and Mann-Whitney tests) were performed using GraphPad Prism 6 software. P values ≤ 0.05 were considered statistically significant.

RESULTS

Significant DNA hypermethylation was observed for CXCL3 and FADD gene promoters in AP lesions when compared to control tissues (P < 0.001) and among other genes (P < 0.05). In contrast, IL12B and IL4R were associated with significant hypomethylation in comparison to other genes (P < 0.05). IL12B, IL4R, CXCL3 and FADD had differential mRNA expression in AP lesions and controls (P < 0.001).

CONCLUSIONS

Differential methylation profiles of immune response-related genes, such as FADD, CXCL3, IL12B and IL4R, may have an influence on individual AP susceptibility and patient treatment outcomes, through their potential contributions to altered expression of disease-relevant genes. Methylation and/or genetic variations in additional genes may also contribute to the dynamics of AP development and should be considered in future studies.

RANKL Triggers Treg-Mediated Immunoregulation in Inflammatory Osteolysis

The chronic inflammatory immune response triggered by the infection of the tooth root canal system results in the local upregulation of RANKL, resulting in periapical bone loss. While RANKL has a well-characterized role in the control of bone homeostasis/pathology, it can play important roles in the regulation of the immune system, although its possible immunoregulatory role in infectious inflammatory osteolytic conditions remains largely unknown. Here, we used a mouse model of infectious inflammatory periapical lesions subjected to continuous or transitory anti-RANKL inhibition, followed by the analysis of lesion outcome and multiple host response parameters. Anti-RANKL administration resulted in arrest of bone loss but interfered in the natural immunoregulation of the lesions observed in the untreated group. RANKL inhibition resulted in an unremitting proinflammatory response, persistent high proinflammatory and effector CD4 response, decreased regulatory T-cell (Treg) migration, and lower levels of Treg-related cytokines IL-10 and TGFb. Anti-RANKL blockade impaired the immunoregulatory process only in early disease stages, while the late administration of anti-RANKL did not interfere with the stablished immunoregulation. The impaired immunoregulation due to RANKL inhibition is characterized by increased delayed-type hypersensitivity in vivo and T-cell proliferation in vitro to the infecting bacteria, which mimic the effects of Treg inhibition, reinforcing a possible influence of RANKL on Treg-mediated suppressive response. The adoptive transfer of CD4+FOXp3+ Tregs to mice receiving anti-RANKL therapy restored the immunoregulatory capacity, attenuating the inflammatory response in the lesions, reestablishing normal T-cell response in vivo and in vitro, and preventing lesion relapse upon anti-RANKL therapy cessation. Therefore, while RANKL inhibition efficiently limited the periapical bone loss, it promoted an unremitting host inflammatory response by interfering with Treg activity, suggesting that this classic osteoclastogenic mediator plays a role in immunoregulation.

Jumonji domain-containing protein 3 regulates the early inflammatory response epigenetically in human periodontal ligament cells

OBJECTIVE

To investigate the role of the histone 3 lysine 27 trimethylation (H3K27me3) demethylase Jumonji domain-containing protein 3 (Jmjd3) in the epigenetic regulation of the inflammatory response in human periodontal ligament cells (HPDLs).

DESIGN

HPDLs were stimulated with lipopolysaccharide from E. coli. The expression of Jmjd3 in HPDLs was examined by quantitative real-time polymerase chain reaction (Q-PCR), Western Blot and immunofluorescent staining. Potential target genes were selected by silencing Jmjd3 and were confirmed by Chromatin Immunoprecipitation (ChIP).

RESULTS

Q-PCR, Western Blot and immunofluorescent staining revealed that the expression of Jmjd3 was increased in inflamed HPDLs. Knockdown of Jmjd3 led to the suppression of inflammation-induced up-regulation of interleukin-6 and interleukin-12. Moreover, ChIP assays demonstrated that Jmjd3 was recruited to the promoters of interleukin-6 and interleukin-12b and this recruitment was associated with decreased levels of trimethylated histone 3 lysine 27 (H3K27).

CONCLUSIONS

It was concluded that Jmjd3 regulated the activation of interleukin-6 and interleukin-12b in the early inflammatory response of HPDLs via demethylation of H3K27me3 at promoters. This molecular event may play an important role in the regulation of the inflammatory response in HPDLs.

Genetic Association with Subgingival Bacterial Colonization in Chronic Periodontitis

Chronic periodontitis is the most prevalent form of inflammatory destructive bone disease and has been affecting humans since antiquity. Evidence suggest that genetic factors can highly influence periodontitis risk, modulating disease elements such as the susceptibility to microbial colonization and the nature of subsequent host-microbe interaction. Several single-nucleotide polymorphisms (SNPs) have been associated with the occurrence of periodontitis, but the full range of genetic influence in periodontitis outcomes remains to be determined. In this context, this study comprises an analysis of possible correlation between periodontitis-related genetic variants with changes in the subgingival microbiological pattern performed in a Brazilian population (n = 167, comprising 76 chronic periodontitis patients and 91 healthy subjects). For the genetic characterization, 19 candidate SNPs were selected based on the top hits of previous large genome wide association studies (GWAS), while the subgingival microbiota was characterized for the presence and relative quantity of 40 bacterial species by DNA-DNA checkerboard. The case/control association test did not demonstrate a significant effect of the target SNPs with the disease phenotype. The polymorphism rs2521634 proved significantly associated with Tannerella forsythia, Actinomyces gerencseriae, Fusobacterium periodonticum, and Prevotella nigrescens; rs10010758 and rs6667202 were associated with increased counts of Porphyromonas gingivalis; and rs10043775 proved significantly associated with decreased counts of Prevotella intermedia. In conclusion, we present strong evidence supporting a direct connection between the host’s genetic profile, specifically rs2521634, rs10010758, rs6667202, and rs10043775 polymorphisms, and the occurrence of chronic periodontitis-associated bacteria.

Diabetes Activates Periodontal Ligament Fibroblasts via NF-κB In Vivo

Diabetes mellitus increases periodontitis and pathogenicity of the oral microbiome. To further understand mechanisms through which diabetes affects periodontitis, we examined its impact on periodontal ligament fibroblasts in vivo and in vitro. Periodontitis was induced by inoculation of Porphyromonas gingivalis and Fusobacterium nucleatum in normoglycemic and diabetic mice. Diabetes, induced by multiple low-dose injections of streptozotocin increased osteoclast numbers and recruitment of neutrophils to the periodontal ligament, which could be accounted for by increased CXC motif chemokine 2 (CXCL2) and receptor activator of nuclear factor kappa B ligand (RANKL) expression by these cells. Diabetes also stimulated a significant increase in nuclear factor kappa B (NF-κB) expression and activation in periodontal ligament (PDL) fibroblasts. Surprisingly, we found that PDL fibroblasts express a 2.3-kb regulatory unit of Col1α1 (collagen type 1, alpha 1) promoter typical of osteoblasts. Diabetes-enhanced CXCL2 and RANKL expression in PDL fibroblasts was rescued in transgenic mice with lineage-specific NF-κB inhibition controlled by this regulatory element. In vitro, high glucose increased NF-κB transcriptional activity, NF-κB nuclear localization, and RANKL expression in PDL fibroblasts, which was reduced by NF-κB inhibition. Thus, diabetes induces changes in PDL fibroblast gene expression that can enhance neutrophil recruitment and bone resorption, which may be explained by high glucose-induced NF-κB activation. Furthermore, PDL fibroblasts express a regulatory element in vivo that is typical of committed osteoblasts.

Simvastatin and nanofibrous poly(l-lactic acid) scaffolds to promote the odontogenic potential of dental pulp cells in an inflammatory environment

In this study, we investigated the anti-inflammatory, odontogenic and pro-angiogenic effects of integrating simvastatin and nanofibrous poly(l-lactic acid) (NF-PLLA) scaffolds on dental pulp cells (DPCs). Highly porous NF-PLLA scaffolds that mimic the nanofibrous architecture of extracellular matrix were first fabricated, then seeded with human DPCs and cultured with 0.1 μM simvastatin and/or 10 μg/mL pro-inflammatory stimulator lipopolysaccharide (LPS). The gene expression of pro-inflammatory mediators (TNF-α, IL-1β and MMP-9 mRNA) and odontoblastic markers (ALP activity, calcium content, DSPP, DMP-1 and BMP-2 mRNA) were quantified after long-term culture in vitro. In addition, we evaluated the scaffold's pro-angiogenic potential after 24 h of in vitro co-culture with endothelial cells. Finally, we assessed the combined effects of simvastatin and NF-PLLA scaffolds in vivo using a subcutaneous implantation mouse model. The in vitro studies demonstrated that, compared with the DPC/NF-PLLA scaffold constructs cultured only with pro-inflammatory stimulator LPS, adding simvastatin significantly repress the expression of pro-inflammatory mediators. Treating LPS+ DPC/NF-PLLA constructs with simvastatin also reverted the negative effects of LPS on expression of odontoblastic markers in vitro and in vivo. Western blot analysis demonstrated that these effects were related to a reduction in NFkBp65 phosphorylation and up-regulation of PPARγ expression, as well as to increased phosphorylation of pERK1/2 and pSmad1, mediated by simvastatin on LPS-stimulated DPCs. The DPC/NF-PLLA constructs treated with LPS/simvastatin also led to an increase in vessel-like structures, correlated with increased VEGF expression in both DPSCs and endothelial cells. Therefore, the combination of low dosage simvastatin and NF-PLLA scaffolds appears to be a promising strategy for dentin regeneration with inflamed dental pulp tissue, by minimizing the inflammatory reaction and increasing the regenerative potential of resident stem cells.

STATEMENT OF SIGNIFICANCE

The regeneration potential of stem cells is dependent on their microenvironment. In this study, we investigated the effect of the microenvironment of dental pulp stem cells (DPSCs), including 3D structure of a macroporous and nanofibrous scaffold, the inflammatory stimulus lipopolysaccharide (LPS) and a biological molecule simvastatin, on their regenerative potential of mineralized dentin tissue. The results demonstrated that LPS upregulated inflammatory mediators and suppressed the odontogenic potential of DPSCs. Known as a lipid-lowing agent, simvastatin was excitingly found to repress the expression of pro-inflammatory mediators, up-regulate odontoblastic markers, and exert a pro-angiogenic effect on endothelial cells, resulting in enhanced vascularization and mineralized dentin tissue regeneration in a biomimetic 3D tissue engineering scaffold. This novel finding is significant for the fields of stem cells, inflammation and dental tissue regeneration.

Effect of lipopolysaccharide derived from surabaya isolates of Actinobacillus actinomycetemcomitans on alveolar bone destruction

Background:

Actinobacillus actinomycetemcomitans’ lipopolysaccharide (LPS) has a high virulence factor. It interacts with serum protein through receptors on the epithelial cell surface, thereby increasing both interleukin (IL)-1β, and IL-6 which results in damage to periodontal tissue.

Aim:

The aim of the study was to identify and evaluate the effect of LPS derived from local isolates (A. actinomycetemcomitans) on the destruction of alveolar bone by means of several biomarkers, including; the number of osteoblasts and osteoclasts, the expression of IL-6, matrix metallopeptidase 1 (MMP-1), and receptor activator of nuclear factor kappa-Β ligand (RANKL).

Materials and Methods:

The isolation of LPS from A. actinomycetemcomitans was calculated using phenol, while purification was performed using Sephadex C-18 column chromatography. 40 Wistar rats were divided into four groups of 10. Each treatment was divided into two groups which were 0.9% NaCl and LPS induced for 7 and 14 days, respectively. Gingival and alveolar bones were further introduced into the induction area, followed by the measuring of osteoblast and osteoclast with hematoxylin-eosin staining, IL-6, MMP-1 and RANKL expression with immunohistochemical.

Results:

Reduced numbers of osteoblasts at the 7^th and 14^th day of treatment were detected, while those of osteoclasts increased. There was an increased expression of IL-6, MMP-1, and RANKL in the 7^th and 14^th-day treatment group. Treatment of LPS from A. actinomycetemcomitans over 7 and 14 days resulted in damage to periodontal tissue and alveolar bone in Wistar rats.

Conclusion:

LPS of A. actinomycetemcomitans administration for 7 and 14 days causes periodontal and alveolar tissue destruction in Wistar rats.

The immunopathogenic and immunomodulatory effects of interleukin-12 in periodontal disease

Interleukin 12 (IL-12) is an inflammatory cytokine that promotes the response of the immune system. This cytokine has been implicated as a potent stimulator of several diseases characterized by inflammatory-induced bone destruction, such as rheumatoid arthritis and periodontitis. Yet, the exact role of IL-12 in the development and progress of periodontitis has not been clarified. Several studies have demonstrated a positive correlation between the level of IL-12 and the severity of periodontal destruction. Deletion of IL-12 in mice with periodontitis significantly suppressed the level of bone destruction. Interestingly, next to a role in modulating the pathogenesis, IL-12 also has immunological-regulatory properties. This cytokine induces expression of immunosuppressive molecules, such as indoleamine-pyrrole 2,3-dioxygenase (IDO). Thus, these findings suggest both negative and positive influences of IL-12 in periodontal disease. It is currently proposed that the diversity of action of cytokines is a molecular key which regulates biological development and homeostasis. Accordingly, the actions of IL-12 might be one of the mechanisms that regulate homeostasis of periodontal tissue during and following inflammation. Therefore, this article aims to review both destructive and protective functionalities of IL-12 with an emphasis on periodontal disease.

Anti-inflammatory activity of cannabinoid receptor 2 ligands in primary hPDL fibroblasts

OBJECTIVES

Approximately 65 million adults in the US have periodontitis, causing tooth loss and decreased quality of life. Cannabinoids modulate immune responses, and endocannabinoids are prevalent during oral cavity inflammation. Targets for intervention in periodontal inflammation are cannabinoid type 1 and 2 receptors (CB1R, CB2R), particularly CB2R because its levels increase during inflammation. We previously demonstrated that SMM-189 (CB2R inverse agonist) decreased pro-inflammatory cytokine production in primary microglial cells. The hypothesis of this study was that cannabinoids anandamide (AEA), HU-308 (CB2R selective agonist), and SMM-189 decrease pro-inflammatory IL-6 and MCP-1 production by primary human periodontal ligament fibroblasts (hPDLFs) stimulated with P. gingivalis LPS, TNF-α, or IL-1β.

DESIGN

Cytotoxic effects of cannabinoid compounds (10^-4-10^-6.5 M), LPS (1-1000 ng/ml), TNFα (10 ng/ml) and IL-1β (1 ng/ml) were assessed by measuring effects on cellular dehydrogenase activity. IL-6 and MCP-1 production were measured using Mesoscale Discovery (MSD) Human Pro-Inflammatory IL-6 and MSD Human Chemokine MCP-1 kits and analyzed using MSD Sector 2400 machine.

RESULTS

EC₅₀ values for AEA, SMM-189, and HU-308 were 16 μM, 13 μM, and 7.3 μM respectively. LPS (1 μg/ml), TNF-α (10 ng/ml), and IL-1β (1 ng/ml) increased IL-6 and MCP-1 production, which were inhibited by AEA, SMM-189, and HU-308. AEA alone significantly increased IL-6, but not MCP-1 levels, but the other cannabinoids alone had no effect.

CONCLUSION

The effective inhibition of LPS, TNF-α, IL-1β stimulated IL-6 and MCP-1 production by CB2R ligands in hPDLFs suggests that targeting the endocannabinoid system may lead to development of novel drugs for periodontal therapy, aiding strategies to improve oral health.

Hunter-gatherer dental pathology: Do historic accounts of Aboriginal Australians correspond to the archeological record of dental disease?

OBJECTIVES

Studies of hunter-gatherer oral pathology, particularly in Australia, often focus upon dental wear and caries or assume that historic studies of Aboriginal people reflect the precontact past. Consequently the range of population variation has been underestimated. In this paper dental pathology from human remains from Roonka are compared with a model of dental pathology derived from historic studies. The aim is to identify aspects of dental pathology indicative of regional or intra-population diversity.

METHODS

Adult dentitions (n = 115) dating from the mid to late Holocene were recorded for the following conditions: dental wear, caries, periapical voids, calculus, periodontal disease and antemortem tooth loss. Statistical analysis was used to identify patterns of dental pathology and to identify causal relationships between conditions.

RESULTS

Dental wear is marked while dental caries rates are extremely low. Other indications of dental pathology are uncommon (<7% of teeth affected). Temporal heterogeneity is apparent: there are 3 young adults with caries who died in the postcontact period. There is also a small group of middle age to old adults with disproportionate abscessing and pulp exposure who may represent temporal variation or heterogeneity in individual frailty.

CONCLUSIONS

The results confirm dental wear as the major cause of dental pathology in this group and that, at a general level, historic accounts do correspond with this archeological sample. However, intra-sample heterogeneity is apparent while 2 dental conditions, calculus and periodontal disease, along with the pattern of sex differences deviate from expectation, demonstrating that to identify regional variation attention needs to be paid to the dentoalveolar complex as a whole.

Oxidative Stress in the Local and Systemic Events of Apical Periodontitis

Oxidative stress is involved in the pathogenesis of a variety of inflammatory disorders. Apical periodontitis (AP) usually results in the formation of an osteolytic apical lesion (AL) caused by the immune response to endodontic infection. Reactive oxygen species (ROS) produced by phagocytic cells in response to bacterial challenge represent an important host defense mechanism, but disturbed redox balance results in tissue injury. This mini review focuses on the role of oxidative stress in the local and associated systemic events in chronic apical periodontitis. During endodontic infection, ligation of Toll-like receptors (TLRs) on phagocytes' surface triggers activation, phagocytosis, synthesis of ROS, activation of humoral and cellular responses, and production of inflammatory mediators, such as, cytokines and matrix metalloproteinases (MMPs). The increment in ROS perturbs the normal redox balance and shifts cells into a state of oxidative stress. ROS induce molecular damage and disturbed redox signaling, that result in the loss of bone homeostasis, increased pro-inflammatory mediators, and MMP overexpression and activation, leading to apical tissue breakdown. On the other hand, oxidative stress has been strongly involved in the pathogenesis of atherosclerosis, where a chronic inflammatory process develops in the arterial wall. Chronic AP is associated with an increased risk of cardiovascular diseases (CVD) and especially atherogenesis. The potential mechanisms linking these diseases are also discussed.

Increased levels of the T-helper 22-associated cytokine (interleukin-22) and transcription factor (aryl hydrocarbon receptor) in patients with periodontitis are associated with osteoclast resorptive activity and severity of the disease

BACKGROUND AND OBJECTIVE

Two new T-helper (Th) phenotypes have been recently described and named Th9 and Th22 lymphocytes; however, their role in the pathogenesis of periodontitis remains unclear. This study was aimed to assess whether Th9 and Th22 lymphocytes, through interleukin (IL)-9 and IL-22 production, respectively, are associated with the severity of periodontitis and bone resorption.

MATERIAL AND METHODS

Gingival crevicular fluid samples and biopsies were obtained from patients with moderate-to-advanced chronic periodontitis and gingivitis, and healthy controls. The levels for the Th9 and Th22-associated cytokines and master-switch transcription factors Spi-B and aryl hydrocarbon receptor (AhR) were quantified by enzyme-linked immunosorbent assay, real-time reverse-transcription quantitative polymerase chain reaction and flow cytometry. In addition, the osteoclast activity in response to tissue homogenates from periodontitis and healthy samples was analyzed quantifying the number of TRAP-positive cells and areas of bone resorption pits produced, in the presence or absence of recombinant human IL-22 and anti-IL-22 neutralization antibody.

RESULTS

Higher levels of IL-22 and AhR were detected in patients with periodontitis compared with gingivitis and healthy individuals. In addition, higher levels of IL-9 and Spi-B were detected in gingivitis patients compared with periodontitis and healthy individuals. In patients with periodontitis, a significant positive correlation was detected between secreted levels of IL-22 and clinical attachment level of the sampled periodontal pockets. When osteoclasts were exposed to tissue homogenates obtained from patients with periodontitis, higher levels of resorptive activity were observed as compared with the same cells exposed to tissue homogenates obtained from healthy individuals, and this increment was dependent on the presence and neutralization of IL-22.

CONCLUSION

Increased levels of IL-22 produced by Th22 lymphocytes are associated with the pathogenesis of periodontitis, in particular, with osteoclast resorptive activity and severity of disease.

M2 macrophages coexist with a Th1-driven profile in periapical cysts

AIM

To evaluate the participation of both Th1 and Th2 responses in periapical cysts by assessing the presence of M2 macrophages, as well as acute IL-1 β, TNF-α and IL-6 cytokines.

METHODOLOGY

Twenty-four cases of periapical cysts were selected. Immuno-expressions of IL-1 β, IL-6, TNF-α and CD163 were analysed in the cystic capsules in both superficial and deeper regions. Data were analysed with paired Wilcoxon test and Spearman correlation coefficient (P ≤ 0.05).

RESULTS

There was a higher expression of IL-1β, IL-6, TNF-α and M2 macrophages in the superficial region (P < 0.001) of cystic capsules. All acute cytokines had significant positive correlations amongst them regardless of the cystic capsule region. Regarding CD163, positive correlations occurred only with TNF-α (P = 0.007; r = 0.537) and IL-6 (P = 0.018; r = 0.478) in the superficial regions of the cystic capsule.

CONCLUSIONS

M2 macrophages participated actively in the inflammatory response of periapical cysts and correlated with the expression of certain acute Th1-related cytokines. This illustrates the coexistence of an acute and chronic Th2-driven immune response in these lesions. Although M2 macrophages favour the healing process, their presence is not sufficient for periapical cyst regression, once an acute active response has occurred due to an infectious stimuli.

Participation of osteoclastogenic factors in immunopathogenesis of human chronic periapical lesions

BACKGROUND

Chronic periapical lesions (CPLs) are common lesions of the oral cavity and are the result of caries, tooth fracture, iatrogenic causes, or factors causing contamination and pulp necrosis. Inflammatory cells participate in the expansion of CPLs by releasing factors that stimulate or inhibit osteolytic activity. The objective of this study was to investigate the participation of RANKL, TNF-α, cathepsin K, IL-33, and OPG in the development of radicular cysts (RCs) and periapical granulomas (PGs).

METHODS

Paraffin-embedded sections of 30 RCs and 22 PGs were submitted to immunohistochemistry.

RESULTS

Immunoexpression of the proteins studied was observed in the epithelium and capsule of RCs, as well as in connective tissue of PGs. The expression of the osteoclastogenic factors studied differed significantly in RCs and PGs (P < .001), with lower expression of OPG in RCs. In PGs, the lowest expression was observed for cathepsin K. Comparison of the 2 lesions showed a similar participation of RANKL and IL33, while a significant difference was observed for OPG (P < .001), TNF-α (P = .002), and cathepsin K (P = .016). No association of the expression of the proteins with lesions size was observed.

CONCLUSIONS

This study demonstrated the participation of RANKL, TNF-α, IL-33, cathepsin K, and OPG in the development of RCs and PGs, with emphasis on the highest immunoreactivity of cathepsin in RCs and TNF-α and OPG in PGs. OPG possibly determines the slower growth of PGs compared to RCs.

The role of 5-lipoxygenase in Aggregatibacter actinomycetemcomitans-induced alveolar bone loss

AIM

Leukotrienes (LTs) are pro-inflammatory lipid mediators formed by the enzyme 5-lipoxygenase (5-LO). The involvement of 5-LO metabolites in periodontal disease (PD) is not well defined. This study aimed to assess the role of 5-LO in experimental PD induced by Aggregatibacter actinomycetemcomitans (Aa).

MATERIAL AND METHODS

In vivo experiments were carried out using SV129 wild-type (WT) and 5-LO-deficient (5lo^-/- ) mice inoculated with Aa. Osteoclasts were stimulated in vitro with AaLPS in the presence or not of selective inhibitors of the 5-LO pathway, or LTB4 or platelet-activating factor (PAF), as PAF has already been shown to increase osteoclast activity.

RESULTS

In 5lo^-/- mice, there were no loss of alveolar bone and less TRAP-positive osteoclasts in periodontal tissues, after Aa inoculation, despite local production of TNF-α and IL-6. The differentiation and activity of osteoclasts stimulated with AaLPS were diminished in the presence of BLT1 antagonist or 5-LO inhibitor, but not in the presence of cysteinyl leukotriene receptor antagonist. The osteoclast differentiation induced by PAF was impaired by the BLT1 antagonism.

CONCLUSION

In conclusion, LTB4 but not CysLTs is important for Aa-induced alveolar bone loss. Overall, LTB4 affects osteoclast differentiation and activity and is a key intermediate of PAF-induced osteoclastogenesis.

The Effect of Calendula officinalis on Oxidative Stress and Bone Loss in Experimental Periodontitis

Periodontitis is associated with reduced antioxidant capacity and increased oxidative damage. Oxidative stress induces inflammation and bone loss contributing to the pathological progression of periodontal disease. Calendula officinalis (CLO) has demonstrated anti-inflammatory and anti-oxidant activities. Therefore, the aim of this study was to evaluate the effect of CLO on oxidative stress and bone loss in rats subjected to experimental periodontitis (EP). For this, 72 male Wistar rats were divided into groups: Naïve, Saline (SAL) and CLO. Rats received SAL or CLO (90 mg/kg) 30 min before ligature and daily until the 11th day. Naïve group experienced no manipulation. After 11 days, the animals were euthanized and left maxillae collected for macroscopic analysis of alveolar bone loss (ABL). Periodontium was analyzed by macroscopy, scanning electron microscopy; confocal and light polarized microscopy. Immunohistochemical examination of DKK1, WNT 10b and β-catenin was performed. The gingival tissue was collected to reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) analyses. The 11 days of ligature induced bone loss, breakdown of collagen fibers, increased the immunostaining DKK-1 while reduced WNT 10b and β-catenin expressions. Periodontitis reduced GSH, SOD, CAT and increase MDA. All findings were reversed by 90 mg/kg of CLO. In summary our findings demonstrated that CLO reduced oxidative stress and bone loss and preserved collagen fibers in rats with EP, with participation of WNT signaling pathway.

MicroRNA-335-5p Plays Dual Roles in Periapical Lesions by Complex Regulation Pathways

INTRODUCTION

MicroRNA-335-5p has been reported to regulate osteogenic and chondrogenic differentiations of mesenchymal stem cells. The aim of this study was to explore the function and regulation mechanism of miR-335-5p in apical periodontitis (AP).

METHODS

Total RNAs were extracted from human periodontal ligament fibroblasts (HPDLFs), 10 AP tissues, and 6 healthy periodontal ligament tissues using lysis buffer. Gene expression was detected using real-time polymerase chain reaction. The Dual Luciferase Assay (Promega, Madison, WI) was used to test miR-335-5p directly targeted urokinase-type plasminogen activator receptor (uPAR) and the receptor activator of nuclear factor kappa-B ligand (RANKL). Western Blot was used to detect protein expressions of RANKL, uPAR, and the fragile X-related 1 gene (FXR1). The enzyme-linked immunosorbent assay was used to detect the secretions of interleukin 6, tumor necrosis factor alpha, and RANKL. Data were analyzed using the Student t test.

RESULTS

miR-335-5p acted as a positive mediator in HPDLF inflammation (P < .05). Two targets of miR-335-5p, uPAR and RANKL, were identified. Interestingly, uPAR was repressed by miR-335-5p at the basal level, but it can be relieved from miR-335-5p-mediated repression, which is called derepression, when HPDLFs were subjected to lipopolysaccharide stimulation. miR-335-5p promoted RANKL in HPDLFs regardless of whether or not it was under inflammatory conditions (P < .05). We proved FXR1 was responsible for the derepression of uPAR from miR-335-5p (P < .01). Both FXR1 and uPAR were positive mediators in HPDLF inflammation (P < .05). miR-335-5p, uPAR, RANKL, and FXR1 had the same expression profiles in HPDLF inflammation and AP tissues (P < .05).

CONCLUSIONS

Our data showed that miR-335-5p may play dual roles in AP, and it might be considered as a target for therapeutic potency in clinical applications.

Osteoimmunology and Beyond

Abstract: Objective

Osteoimmunology investigates interactions between skeleton and immune system. In the light of recent discoveries in this field, a new reading register of osteoporosis is actually emerging, in which bone and immune cells are strictly interconnected. Osteoporosis could therefore be considered a chronic immune mediated disease which shares with other age related disorders a common inflammatory background. Here, we highlight these recent discoveries and the new landscape that is emerging.

Method

Extensive literature search in PubMed central.

Results

While the inflammatory nature of osteoporosis has been clearly recognized, other interesting aspects of osteoimmunology are currently emerging. In addition, mounting evidence indicates that the immunoskeletal interface is involved in the regulation of important body functions beyond bone remodeling. Bone cells take part with cells of the immune system in various immunological functions, configuring a real expanded immune system, and are therefore variously involved not only as target but also as main actors in various pathological conditions affecting primarily the immune system, such as autoimmunity and immune deficiencies, as well as in aging, menopause and other diseases sharing an inflammatory background.

Conclusion

The review highlights the complexity of interwoven pathways and shared mechanisms of the crosstalk between the immune and bone systems. More interestingly, the interdisciplinary field of osteoimmunology is now expanding beyond bone and immune cells, defining new homeostatic networks in which other organs and systems are functionally interconnected. Therefore, the correct skeletal integrity maintenance may be also relevant to other functions outside its involvement in bone mineral homeostasis, hemopoiesis and immunity.

Differential human Th22-lymphocyte response triggered by Aggregatibacter actinomycetemcomitans serotypes

OBJECTIVE

In Aggregatibacter actinomycetemcomitans, different serotypes have been described based on lipopolysaccharide (LPS) antigenicity. When T lymphocytes were stimulated with these serotypes, different patterns of T-helper (Th)1 and Th17-type of immune responses were reported. Recently, two new Th phenotypes have been described and named Th9 and Th22 lymphocytes; however, their role in the pathogenesis of periodontitis remains unclear. This study aimed to investigate the potential Th9 and/or Th22 lymphocyte responses when stimulated with autologous dendritic cells infected with different A. actinomycetemcomitans serotypes.

METHODS

Monocyte-derived dendritic cells and naïve CD4⁺ T lymphocytes were obtained from healthy donors and stimulated with different serotypes of A. actinomycetemcomitans at a multiplicity of infection MOI=10² or their purified LPS (10-50ng/ml). The levels for the Th9 and Th22-associated cytokines, as well as the transcription factor master-switch genes implied in their differentiation Spi-B and AhR, were quantified by qPCR and ELISA.

RESULTS

When stimulated with the serotype b of A. actinomycetemcomitans, higher levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-α were detected in dendritic cells, as well as higher levels of IL-22 and AhR were detected in T lymphocytes, when compared with stimulation with the other serotypes.

CONCLUSIONS

The serotype b of A. actinomycetemcomitans has a higher capacity of trigger Th22-type of immune response in both dendritic cells and T lymphocytes. These data allow us to suggest that, when the serotype b of A. actinomycetemcomitans is a significant part of the subgingival biofilm, the Th22 polarization might be triggered within the periodontal lesion.

Basic biology and role of interleukin-17 in immunity and inflammation

Interleukin-17 (also known as interleukin-17A) is a key cytokine that links T-cell activation to neutrophil mobilization and activation. As such, interleukin-17 can mediate protective innate immunity to pathogens or contribute to the pathogenesis of inflammatory diseases, such as psoriasis and rheumatoid arthritis. This review summarizes the basic biology of interleukin-17 and discusses its emerging role in periodontal disease. The current burden of evidence from human and animal model studies suggests that the net effect of interleukin-17 signaling promotes disease development. In addition to promoting neutrophilic inflammation, interleukin-17 has potent pro-osteoclastogenic effects that are likely to contribute to the pathogenesis of periodontitis, rheumatoid arthritis and other diseases involving bone immunopathology. Systemic treatments with anti-interleukin-17 biologics have shown promising results in clinical trials for psoriasis and rheumatoid arthritis; however, their impact on the highly prevalent periodontal disease has not been investigated or reported. Future clinical trials, preferably using locally administered interleukin-17 blockers, are required to implicate conclusivelyinterleukin-17 in periodontitis and, more importantly, to establish an effective adjunctive treatment for this oral inflammatory disease.

Interleukin-33 and RANK-L Interplay in the Alveolar Bone Loss Associated to Periodontitis

Introduction

Chronic Periodontitis (CP) is an inflammatory disease of bacterial origin that results in alveolar bone destruction. Porphyromonas gingivalis (Pg), one of the main periopathogens, initiates an inflammatory cascade by host immune cells thereby increasing recruitment and activity of osteoclasts, the bone resorbing cells, through enhanced production of the crucial osteoclastogenic factor, RANK-L. Antibodies directed against some cytokines (IL-1β, IL-6 and TNF-α) failed to exhibit convincing therapeutic effect in CP. It has been suggested that IL-33, could be of interest in CP.

Objective

the present study aims to analyze whether and how IL-33 and RANK-L and/or their interplay are involved in the bone destruction associated to CP.

Material and Methods

mRNAs and protein expressions of IL-33 and RANK-L were analyzed in healthy and CP human gingival samples by immunohistochemistry (IHC) and RT-qPCR. Murine experimental periodontitis (EP) was induced using Pg infected ligature and Pg free ligature around the first maxillary molar. Alveolar bone loss was recorded by μCT. Mouse gingival explants were stimulated for 24 hours with IL-33 and RANK-L mRNA expression investigated by RT-qPCR. Human oral epithelial cells were infected by Pg for 6, 12; 24 hours and IL-33 and RANK-L mRNA expressions were analyzed by RT-qPCR.

Results

IL-33 is overexpressed in gingival epithelial cells in human affected by CP as in the murine EP. In human as in murine gingival cells, RANK-L was independently induced by Pg and IL-33. We also showed that the Pg-dependent RANK-L expression in gingival epithelial cells occured earlier than that of IL-33.

Conclusion

Our results evidence that IL-33 overexpression in gingival epithelial cells is associated with CP and may trigger RANK-L expression in addition to a direct effect of Pg. Finally, IL-33 may act as an extracellular alarmin (danger signal) showing proinflammatory properties in CP perpetuating bone resorption induced by Pg infection.

MMP1-1607 polymorphism increases the risk for periapical lesion development through the upregulation MMP-1 expression in association with pro-inflammatory milieu elements

Increased matrix metalloproteinases (MMPs) activity is a hallmark of periapical granulomas. However, the factors underlying the MMPs expression modulation in healthy and diseased periapical tissues remains to be determined.

Biological Markers for Pulpal Inflammation: A Systematic Review

Background and Objective

Pulpitis is mainly caused by an opportunistic infection of the pulp space with commensal oral microorganisms. Depending on the state of inflammation, different treatment regimes are currently advocated. Predictable vital pulp therapy depends on accurate determination of the pulpal status that will allow repair to occur. The role of several players of the host response in pulpitis is well documented: cytokines, proteases, inflammatory mediators, growth factors, antimicrobial peptides and others contribute to pulpal defense mechanisms; these factors may serve as biomarkers that indicate the status of the pulp. Therefore, the aim of this systematic review was to evaluate the presence of biomarkers in pulpitis.

Methods

The electronic databases of MEDLINE, EMBASE, Scopus and other sources were searched for English and non-English articles published through February 2015. Two independent reviewers extracted information regarding study design, tissue or analyte used, outcome measures, results and conclusions for each article. The quality of the included studies was assessed using a modification of the Newcastle-Ottawa-Scale.

Results and Conclusions

From the initial 847 publications evaluated, a total of 57 articles were included in this review. In general, irreversible pulpitis was associated with different expression of various biomarkers compared to normal controls. These biomarkers were significantly expressed not only in pulp tissue, but also in gingival crevicular fluid that can be collected non-invasively, and in dentin fluid that can be analyzed without extirpating the entire pulpal tissue. Such data may then be used to accurately differentiate diseased from healthy pulp tissue. The interplay of pulpal biomarkers and their potential use for a more accurate and biologically based diagnostic tool in endodontics is envisaged.

Porphyromonas gingivalis suppresses adaptive immunity in periodontitis, atherosclerosis, and Alzheimer's disease

Porphyromonas gingivalis, a keystone pathogen in chronic periodontitis, has been found to associate with remote body organ inflammatory pathologies, including atherosclerosis and Alzheimer’s disease (AD). Although P. gingivalis has a plethora of virulence factors, much of its pathogenicity is surprisingly related to the overall immunosuppression of the host. This review focuses on P. gingivalis aiding suppression of the host’s adaptive immune system involving manipulation of cellular immunological responses, specifically T cells and B cells in periodontitis and related conditions. In periodontitis, this bacterium inhibits the synthesis of IL-2 and increases humoral responses. This reduces the inflammatory responses related to T- and B-cell activation, and subsequent IFN-γ secretion by a subset of T cells. The T cells further suppress upregulation of programmed cell death-1 (PD-1)-receptor on CD⁺cells and its ligand PD-L1 on CD11b⁺-subset of T cells. IL-2 downregulates genes regulated by immune response and induces a cytokine pattern in which the Th17 lineage is favored, thereby modulating the Th17/T-regulatory cell (Treg) imbalance. The suppression of IFN-γ-stimulated release of interferon-inducible protein-10 (IP-10) chemokine ligands [ITAC (CXCL11) and Mig (CXCL9)] by P. gingivalis capsular serotypes triggers distinct T cell responses and contributes to local immune evasion by release of its outer membrane vesicles. In atherosclerosis, P. gingivalis reduces Tregs, transforms growth factor beta-1 (TGFβ-1), and causes imbalance in the Th17 lineage of the Treg population. In AD, P. gingivalis may affect the blood–brain barrier permeability and inhibit local IFN-γ response by preventing entry of immune cells into the brain. The scarcity of adaptive immune cells in AD neuropathology implies P. gingivalis infection of the brain likely causing impaired clearance of insoluble amyloid and inducing immunosuppression. By the effective manipulation of the armory of adaptive immune suppression through a plethora of virulence factors, P. gingivalis may act as a keystone organism in periodontitis and in related systemic diseases and other remote body inflammatory pathologies.

VEGFR-2 reduces while combined VEGFR-2 and -3 signaling increases inflammation in apical periodontitis

BACKGROUND

In apical periodontitis, oral pathogens provoke an inflammatory response in the apical area that induces bone resorptive lesions. In inflammation, angio- and lymphangiogenesis take place. Vascular endothelial growth factors (VEGFs) and their receptors (VEGFRs) are key players in these processes and are expressed in immune cells and endothelial cells in the lesions.

OBJECTIVE

We aimed at testing the role of VEGFR-2 and -3 in periapical lesion development and investigated their role in lymphangiogenesis in the draining lymph nodes.

DESIGN

We induced lesions by pulp exposure in the lower first molars of C57BL/6 mice. The mice received IgG injections or blocking antibodies against VEGFR-2 (anti-R2), VEGFR-3 (anti-R3), or combined VEGFR-2 and -3, starting on day 0 until day 10 or 21 post-exposure.

RESULTS

Lesions developed faster in the anti-R2 and anti-R3 group than in the control and anti-R2/R3 groups. In the anti-R2 group, a strong inflammatory response was found expressed as increased number of neutrophils and osteoclasts. A decreased level of pro-inflammatory cytokines was found in the anti-R2/R3 group. Lymphangiogenesis in the draining lymph nodes was inhibited after blocking of VEGFR-2 and/or -3, while the largest lymph node size was seen after anti-R2 treatment.

CONCLUSIONS

We demonstrate an anti-inflammatory effect of VEGFR-2 signaling in periapical lesions which seems to involve neutrophil regulation and is independent of angiogenesis. Combined signaling of VEGFR-2 and -3 has a pro-inflammatory effect. Lymph node lymphangiogenesis is promoted through activation of VEGFR-2 and/or VEGFR-3.

Heat Shock 70 Protein Genes and Genetic Susceptibility to Apical Periodontitis

INTRODUCTION

Heat shock proteins (HSPs) protect cells under adverse conditions such as infection, inflammation, and disease. The differential expression of HSPs in human periapical granulomas suggests a potential role for these proteins in periapical lesion development, which may contribute to different clinical outcomes. Therefore, we hypothesized that polymorphisms in HSP genes leading to perturbed gene expression and protein function may contribute to an individual's susceptibility to periapical lesion development.

METHODS

Subjects with deep carious lesions with or without periapical lesions (≥3 mm) were recruited at the University of Texas School of Dentistry at Houston and at the University of Pittsburgh. Genomic DNA samples of 400 patients were sorted into 2 groups: 183 cases with deep carious lesions and periapical lesions (cases) and 217 cases with deep carious lesions but without periapical lesions (controls). Eight single nucleotide polymorphisms (SNPs) in HSPA4, HSPA6, HSPA1L, HSPA4L, and HSPA9 genes were selected for genotyping. Genotypes were generated by end point analysis by using Taqman chemistry in a real-time polymerase chain reaction assay. Allele and genotype frequencies were compared among cases and controls by using χ(2) and Fisher exact tests as implemented in PLINK v.1.07. In silico analysis of SNP function was performed by using Polymorphism Phenotyping V2 and MirSNP software.

RESULTS

Overall, SNPs in HSPA1L and HSPA6 showed significant allelic association with cases of deep caries and periapical lesions (P < .05). We also observed altered transmission of HSPA1L SNP haplotypes (P = .03). In silico analysis of HSPA1L rs2075800 function showed that this SNP results in a glutamine-to-lysine substitution at position 602 of the protein and might affect the stability and function of the final protein.

CONCLUSIONS

Variations in HSPA1L and HSPA6 may be associated with periapical lesion formation in individuals with untreated deep carious lesions. Future studies could help predict host susceptibility to developing apical periodontitis.

MicroRNA-200c Represses IL-6, IL-8, and CCL-5 Expression and Enhances Osteogenic Differentiation

MicroRNAs (miRs) regulate inflammation and BMP antagonists, thus they have potential uses as therapeutic reagents. However, the molecular function of miR-200c in modulating proinflammatory and bone metabolic mediators and osteogenic differentiation is not known. After miR-200c was transduced into a human embryonic palatal mesenchyme (HEPM) (a cell line of preosteoblasts), using lentiviral vectors, the resulting miR-200c overexpression increased osteogenic differentiation biomarkers, including osteocalcin (OCN) transcripts and calcium content. miR-200c expression also down-regulated interleukin (IL)-6, IL-8, and chemokine (C-C motif) ligand (CCL)-5 under lipopolysaccharide (LPS) stimulation and increased osteoprotegerin (OPG) in these cells. miR-200c directly regulates the expression of IL-6, IL-8 and CCL-5 transcripts by binding to their 3’UTRs. A plasmid-based miR-200c inhibitor effectively reduces their binding activities. Additionally, miR-200c delivered using polyethylenimine (PEI) nanoparticles effectively inhibits IL-6, IL-8 and CCL-5 in primary human periodontal ligament fibroblasts and increases the biomarkers of osteogenic differentiation in human bone marrow mesenchymal stem cells (MSCs), including calcium content, ALP, and Runx2. These data demonstrate that miR-200c represses IL-6, IL-8 and CCL-5 and improves osteogenic differentiation. miR-200c may potentially be used as an effective means to prevent periodontitis-associated bone loss by arresting inflammation and osteoclastogenesis and enhancing bone regeneration.

Sex-based differential regulation of bacterial-induced bone resorption

BACKGROUND AND OBJECTIVE

Periodontal disease pathogenesis is comprised of the complex inflammatory immune response to oral bacterial dysbiosis. Like other inflammatory diseases, there is sexual dimorphism evident in periodontal diseases. During periodontitis, inflammatory chemokines direct neutrophils to migrate to the site of infection to neutralize the pathogen. Interestingly, these same chemokines are also involved in regulating pathogen-induced osteoclast formation. Previous reports show differences in bone turnover and lymphocyte recruitment between sexes. We hypothesize that chemokine expression is differentially regulated by sex and thus results in differential osteoclast formation.

MATERIAL AND METHODS

Male and female mice were utilized to isolate neutrophils based on expression of Ly6G-specific, as well as defined osteoclast progenitors. Cells were stimulated with lipopolysaccharide (LPS; 100 ng/mL) then analyzed for neutrophil infiltration and gene expression. Defined osteoclast progenitors were primed: macrophage-colony stimulating factor (25 ng/mL), receptor activator of NF-κB ligand (50 ng/mL), then stimulated with LPS. Osteoclasts were enumerated via TRAP stain and mRNA isolated for gene expression analysis via quantitative polymerase chain reaction.

RESULTS

In response to LPS, male neutrophils in vitro respond with increased chemokine expression and significantly more osteoclast formed in response to LPS compared to females.

CONCLUSIONS

Findings support observations in humans regarding a sexual dimorphism in oral bacterial infections of alveolar bone loss. Males have a strong inflammatory response to bacterial infection, resulting in increased inflammatory microenvironment, reduced pathogenic bacteria clearance and increased osteoclast-driven bone loss in response to differential expression of key chemokines.

Cross-talk between clinical and host-response parameters of periodontitis in smokers

BACKGROUND AND OBJECTIVE

Periodontal diseases are a major public health concern leading to tooth loss and have also been shown to be associated with several chronic systemic diseases. Smoking is a major risk factor for the development of numerous systemic diseases, as well as periodontitis. While it is clear that smokers have a significantly enhanced risk for developing periodontitis leading to tooth loss, the population varies regarding susceptibility to disease associated with smoking. This investigation focused on identifying differences in four broad sets of variables, consisting of: (i) host-response molecules; (ii) periodontal clinical parameters; (iii) antibody responses to periodontal pathogens and oral commensal bacteria; and (iv) other variables of interest, in a population of smokers with (n = 171) and without (n = 117) periodontitis.

MATERIAL AND METHODS

Bayesian network structured learning (BNSL) techniques were used to investigate potential associations and cross-talk between the four broad sets of variables.

RESULTS

BNSL revealed two broad communities with markedly different topology between the populations of smokers, with and without periodontitis. Confidence of the edges in the resulting network also showed marked variations within and between the periodontitis and nonperiodontitis groups.

CONCLUSION

The results presented validated known associations and discovered new ones with minimal precedence that may warrant further investigation and novel hypothesis generation. Cross-talk between the clinical variables and antibody profiles of bacteria were especially pronounced in the case of periodontitis and were mediated by the antibody response profile to Porphyromonas gingivalis.

Osteogenic differentiation of human mesenchymal stem cells promotes mineralization within a biodegradable peptide hydrogel

An attractive strategy for the regeneration of tissues has been the use of extracellular matrix analogous biomaterials. Peptide-based fibrillar hydrogels have been shown to mimic the structure of extracellular matrix offering cells a niche to undertake their physiological functions. In this study, the capability of an ionic-complementary peptide FEFEFKFK (F, E, and K are phenylalanine, glutamic acid, and lysine, respectively) hydrogel to host human mesenchymal stem cells in three dimensions and induce their osteogenic differentiation is demonstrated. Assays showed sustained cell viability and proliferation throughout the hydrogel over 12 days of culture and these human mesenchymal stem cells differentiated into osteoblasts simply upon addition of osteogenic stimulation. Differentiated osteoblasts synthesized key bone proteins, including collagen-1 (Col-1), osteocalcin, and alkaline phosphatase. Moreover, mineralization occurred within the hydrogel. The peptide hydrogel is a naturally biodegradable material as shown by oscillatory rheology and reversed-phase high-performance liquid chromatography, where both viscoelastic properties and the degradation of the hydrogel were monitored over time, respectively. These findings demonstrate that a biodegradable octapeptide hydrogel can host and induce the differentiation of stem cells and has the potential for the regeneration of hard tissues such as alveolar bone.

Enterococcus faecalis promotes osteoclast differentiation within an osteoblast/osteoclast co-culture system

OBJECTIVE

To investigate the effects of heat-killed Enterococcus faecalis ATCC 29212 and P25RC clinical strain (derived from an obturated root canal with apical periodontitis) on osteoclast differentiation within an osteoblast/osteoclast co-culture system.

RESULTS

Heat-killed E. faecalis significantly increased the proportion of multinucleated osteoclastic cells (MNCs) within the co-culture system. The IL-6 level was significantly increased upon exposure to heat-killed E. faecalis. Gene expression levels of NFATc1 and cathepsin K were significantly up-regulated compared to the untreated control. EphrinB2 and EphB4 expressions at both the mRNA and protein levels were also significantly upregulated compared to the untreated control.

CONCLUSIONS

Heat-killed E. faecalis can induce osteoclast differentiation within the osteoblast/osteoclast co-culture system in vitro, possibly through ephrinB2-EphB4 bidirectional signaling.

Bone biology-related gingival transcriptome in ageing and periodontitis in non-human primates

AIM

Cellular and molecular immunoinflammatory changes in gingival tissues drive alveolar bone loss in periodontitis. Since ageing is a risk factor for periodontitis, we sought to identify age-related gingival transcriptome changes associated with bone metabolism in both healthy and in naturally occurring periodontitis.

MATERIALS AND METHODS

Adult (12-16 years) and aged (18-23 years) non-human primates (M. mulatta) (n = 24) were grouped into healthy and periodontitis. Gingival tissue samples were obtained and subjected to microarray analysis using the Gene Chip Macaque Genome Array. Gene expression profiles involved in osteoclast/osteoblast proliferation, adhesion and function were evaluated and compared across and between the age groups. QPCR was also performed on selected genes to validate microarray data.

RESULTS

Healthy aged tissues showed a gene profile expression that suggest enhancement of osteoclastic adhesion, proliferation/survival and function (SPP1, TLR4, MMP8 and TFEC) and impaired osteoblastic activity (SMEK3P and SMAD5). The gingival transcriptome in both adult and aged animals with naturally occurring periodontitis (FOS, IL6, TLR4, MMP9, MMP10 and SPP1 genes) was consistent with a local inflammatory response driving towards bone/connective tissue destruction.

CONCLUSION

A pro-osteoclastogenic gingival transcriptome is associated with periodontitis irrespective of age; however; a greater bone-destructive molecular environment is associated with ageing in healthy tissues.

Cytokines during periodontal wound healing: potential application for new therapeutic approach

Regeneration of periodontal tissues is one of the main goals of periodontal therapy. However, current treatment, including surgical approach, use of membrane to allow maturation of all periodontal tissues, or use of enamel matrix derivatives, presents limitations in their indications and outcomes leading to the development of new tissue engineering strategies. Several cytokines are considered as key molecules during periodontal destruction process. However, their role during each phase of periodontal wound healing remains unclear. Control and modulation of the inflammatory response and especially, release of cytokines or activation/inhibition in a time- and spatial-controlled manner may be a potential perspective for periodontal tissue engineering. The aim of this review was to summarize the specific role of several cytokines during periodontal wound healing and the potential therapeutic interest of inflammatory modulation for periodontal regeneration especially related to the expression sequence of cytokines.