IL-17 is involved in bone resorption in mouse periapical lesions

Effects of adjacent periodontitis on osseointegrated dental implants

PURPOSE

This study aimed to investigate whether new-onset periodontitis or apical periodontitis in the adjacent teeth affects osseointegrated dental implants in a beagle dog model.

METHODS

One control group and 2 experimental groups (periodontitis and apical periodontitis groups) were defined based on the presence of experimental periodontitis or apical periodontitis, with 1 beagle dog randomly assigned to each group. The mandibular second and fourth premolars on both sides of the 3 beagles were extracted. Eight weeks after extraction, 4 bone-level implant fixtures, 2 on both sides of each mandible, were placed in each beagle. Six weeks after implant surgery, healing abutments were connected. After sufficient osseointegration, plaque control was performed in the control group, while periodontitis and apical periodontitis were induced in the experimental groups. The beagles were euthanized for histological analyses 20 weeks after induction of experimental periodontitis. Statistical analyses were performed using the Kruskal-Wallis test with the Bonferroni correction to compare the 3 groups.

RESULTS

The implants in the control and apical periodontitis groups were well-maintained, while those in the periodontitis group showed clinical signs of inflammation with bone resorption. The bone-to-implant contact (BIC) and bone area values in the periodontitis group were lower than those in the other groups. The distance between the implant shoulder and the first BIC was significantly greater in the periodontitis group than in the control group (P<0.05).

CONCLUSIONS

The presence of periodontitis in adjacent teeth can pose a risk to dental implants, potentially resulting in peri-implantitis. However, this was not observed for apical periodontitis. Within the limitations of this study, periodontal care is necessary to reduce the impact of periodontitis in adjacent teeth on osseointegrated implants.

Five-year outcomes of immediate implant placement for mandibular molars with and without chronic apical periodontitis: A retrospective study

BACKGROUND

Most physicians consider molars with chronic apical periodontitis (CAP) lesions as contraindications for immediate implant placement. At the patient’s request, we perform immediate implant placement of the mandibular molars with CAP in clinical practice.

AIM

To retrospectively analyze and compare the 5-year outcomes of immediate implant placement of the mandibular molars with CAP and those without obvious inflammation.

METHODS

The clinical data of patients with immediate implant placement of the mandibular molars in the Department of Oral and Maxillofacial Surgery, the Affiliated Hospital of Qingdao University, from June 2015 to June 2017 were collected. The patients were divided into CAP (n = 52) and no-CAP (n = 45) groups. Changes in bone mineral density and bone mass around implants were analyzed 5 years after implant restoration.

RESULTS

At 5 years after implantation, the peri-implant bone mineral density was 528.2 ± 78.8 Hounsfield unit (HU) in the CAP group and 562.6 ± 82.9 HU in the no-CAP group (P = 0.126). Marginal bone resorption around implants did not differ significantly between the two groups, including buccal (P = 0.268) or lingual (P = 0.526) resorption in the vertical direction or buccal (P = 0.428) or lingual (P = 0.560) resorption in the horizontal direction. Changes in the peri-implant jump space did not differ significantly between the two groups, including the buccal (P = 0.247) or lingual (P = 0.604) space in the vertical direction or buccal (P = 0.527) or lingual (P = 0.707) space in the horizontal direction. The gray value of cone-beam computed tomography measured using Image J software can reflect the bone mineral density. In the CAP area, the gray values of the bone tissue immediately and 5 years after implant placement differed significantly from those of the surrounding bone tissue (P < 0.01).

CONCLUSION

The results of this study suggest that immediate implant placement of the mandibular molars with CAP can achieve satisfactory 5-year clinical results, without significant differences in the complications, survival rate, or bone tissue condition from the no-CAP mandibular molars.

Five-year outcomes of immediate implant placement for mandibular molars with and without chronic apical periodontitis: A retrospective study

BACKGROUND

Most physicians consider molars with chronic apical periodontitis (CAP) lesions as contraindications for immediate implant placement. At the patient's request, we perform immediate implant placement of the mandibular molars with CAP in clinical practice.

AIM

To retrospectively analyze and compare the 5-year outcomes of immediate implant placement of the mandibular molars with CAP and those without obvious inflammation.

METHODS

The clinical data of patients with immediate implant placement of the mandibular molars in the Department of Oral and Maxillofacial Surgery, the Affiliated Hospital of Qingdao University, from June 2015 to June 2017 were collected. The patients were divided into CAP (n = 52) and no-CAP (n = 45) groups. Changes in bone mineral density and bone mass around implants were analyzed 5 years after implant restoration.

RESULTS

At 5 years after implantation, the peri-implant bone mineral density was 528.2 ± 78.8 Hounsfield unit (HU) in the CAP group and 562.6 ± 82.9 HU in the no-CAP group (P = 0.126). Marginal bone resorption around implants did not differ significantly between the two groups, including buccal (P = 0.268) or lingual (P = 0.526) resorption in the vertical direction or buccal (P = 0.428) or lingual (P = 0.560) resorption in the horizontal direction. Changes in the peri-implant jump space did not differ significantly between the two groups, including the buccal (P = 0.247) or lingual (P = 0.604) space in the vertical direction or buccal (P = 0.527) or lingual (P = 0.707) space in the horizontal direction. The gray value of cone-beam computed tomography measured using Image J software can reflect the bone mineral density. In the CAP area, the gray values of the bone tissue immediately and 5 years after implant placement differed significantly from those of the surrounding bone tissue (P < 0.01).

CONCLUSION

The results of this study suggest that immediate implant placement of the mandibular molars with CAP can achieve satisfactory 5-year clinical results, without significant differences in the complications, survival rate, or bone tissue condition from the no-CAP mandibular molars.

Revisiting the role of IL-1 signaling in the development of apical periodontitis

Apical periodontitis (AP) develops as a result of an immune response to pulpal bacterial infection, and various cytokines are involved in the pathogenesis of AP, with Interleukin (IL)-1 being considered a key cytokine. The role of IL-1 in the pathogenesis of AP has been well studied. It is known that IL-1 expression in periapical lesions correlates closely with the development of AP. IL-1 is a potent bone-resorptive cytokine that induces osteoclast formation and activation. Hence, inhibiting its signaling with IL-1 receptor antagonist (IL-1RA) results in a reduction in periapical lesion size. On the other hand, IL-1 is also a central cytokine that combats bacterial infection by activating innate immune responses. Therefore, a complete loss of IL-1 signaling leads to a failure to limit bacterial dissemination and consequently exacerbates AP. In vivo, IL-1 expression is tightly regulated and its signaling is modulated to optimize the immune response. Obesity causes systemic low-grade chronic inflammation and increases the risk of cardiovascular, renal, and other disorders. In experimentally induced AP, obesity significantly increases periapical bone loss, albeit the underlying mechanism remains unclear. Recent technological innovations have enabled more comprehensive and detailed analyses than previously, leading to new insights into the role of IL-1RA in regulating IL-1 signaling, and modulating apical lesion progression in obesity. In this review, we provide a brief overview of the function of IL-1 in AP development, with special emphasis on the latest findings in normal weight and obese states.

Periapical lesions in two inbred strains of rats differing in immunological reactivity

AIM

To investigate the influence of strain differences in immune responses on the pathogenesis of experimental periapical lesions in Dark Agouti (DA) and Albino Oxford (AO) inbred strains of rats.

METHODOLOGY

Periapical lesions were induced in male DA and AO rats by pulp exposure of the first mandibular right molars to the oral environment. Animals were killed 21 days after pulp exposure. The mandibular jaws were retrieved and prepared for radiographic, pathohistological, immunohistochemical analysis, real-time PCR and flow cytometry. Blood samples and the supernatant of periapical lesions were collected for measurement of cytokines and oxidative stress marker levels. Statistical analysis was performed using the Kruskal-Wallis H and Mann-Whitney U non-parametric tests or parametric One-Way anova and Independent Samples T-test to determine the differences between groups depending on the normality of the data. A significant difference was considered when p values were <.05.

RESULTS

DA rats developed significantly larger (p < .05) periapical lesions compared to AO rats as confirmed by radiographic and pathohistological analysis. The immunohistochemical staining intensity for CD3 was significantly greater in periapical lesions of DA rats compared to AO rats (p < .05). In DA rats, periapical lesions had a significantly higher (p < .05) percentage of CD3+ cells compared to AO rats. Also, the percentage of INF-γ, IL-17 and IL-10 CD3+CD4+ cells was significantly higher in DA rats (p < .05). DA rats had a significantly higher Th17/Th10 ratio. RT-PCR expression of IL-1β, INF-γ and IL-17 genes was significantly higher in periapical lesions of DA compared to AO rats (p < .05). The receptor activator of nuclear factor kappa-Β ligand/osteoprotegerin ratio was higher in DA compared to AO rats with periapical lesions (p < .05). Systemic levels of TNF-α and IL-6 were significantly higher in DA compared to AO rats (p < .05). Levels of lipid peroxidation measured as thiobarbituric acid reactive substances and reduced glutathione were significantly higher (p < .05) in the supernatant in the periapical lesions of DA rats.

CONCLUSION

After pulp exposure, DA rats developed much larger periapical lesions compared to AO rats. Genetically determined differences in immunopathology have been demonstrated to be a significant element defining the severity of periapical lesions.

Comparative Metabolomics Reveals the Microenvironment of Common T-Helper Cells and Differential Immune Cells Linked to Unique Periapical Lesions

Periapical abscesses, radicular cysts, and periapical granulomas are the most frequently identified pathological lesions in the alveolar bone. While little is known about the initiation and progression of these conditions, the metabolic environment and the related immunological behaviors were examined for the first time to model the development of each pathological condition. Metabolites were extracted from each lesion and profiled using gas chromatography-mass spectrometry in comparison with healthy pulp tissue. The metabolites were clustered and linked to their related immune cell fractions. Clusters I and J in the periapical abscess upregulated the expression of MMP-9, IL-8, CYP4F3, and VEGF, while clusters L and M were related to lipophagy and apoptosis in radicular cyst, and cluster P in periapical granuloma, which contains L-(+)-lactic acid and ethylene glycol, was related to granuloma formation. Oleic acid, 17-octadecynoic acid, 1-nonadecene, and L-(+)-lactic acid were significantly the highest unique metabolites in healthy pulp tissue, periapical abscess, radicular cyst, and periapical granuloma, respectively. The correlated enriched metabolic pathways were identified, and the related active genes were predicted. Glutamatergic synapse (16–20),-hydroxyeicosatetraenoic acids, lipophagy, and retinoid X receptor coupled with vitamin D receptor were the most significantly enriched pathways in healthy control, abscess, cyst, and granuloma, respectively. Compared with the healthy control, significant upregulation in the gene expression of CYP4F3, VEGF, IL-8, TLR2 (P < 0.0001), and MMP-9 (P < 0.001) was found in the abscesses. While IL-12A was significantly upregulated in cysts (P < 0.01), IL-17A represents the highest significantly upregulated gene in granulomas (P < 0.0001). From the predicted active genes, CIBERSORT suggested the presence of natural killer cells, dendritic cells, pro-inflammatory M1 macrophages, and anti-inflammatory M2 macrophages in different proportions. In addition, the single nucleotide polymorphisms related to IL-10, IL-12A, and IL-17D genes were shown to be associated with periapical lesions and other oral lesions. Collectively, the unique metabolism and related immune response shape up an environment that initiates and maintains the existence and progression of these oral lesions, suggesting an important role in diagnosis and effective targeted therapy.

Interleukin-17 modulates uPA and MMP2 expression in human periodontal ligament mesenchymal stem cells: Involvement of the ERK1/2 MAPK pathway

Periodontal disease is a chronic infection of periodontal tissue characterized by extracellular matrix (ECM) degradation due to increased expression of plasminogen activators and matrix metalloproteinases (MMPs) and various proinflammatory cytokines, including interleukin (IL)-17. Successful regeneration of damaged periodontal tissues depends on the proper functionality of periodontal ligament mesenchymal stem cells (PDLMSCs), especially the production of extracellular matrix proteases. We investigated the influence of IL-17 on ECM remodeling through modulation of urokinasetype plasminogen activator (uPA) and MMP2/MMP9 expression in human PDLMSCs at mRNA, protein and activity levels using by RT-PCR, Western blotting and zymography, respectively. Investigation of the involvement of MAPKs in these processes in PDLMSCs was determined by Western blotting, as well as by utilizing specific p38 and MEK1/2 inhibitors. Our results show that IL-17 activates MAPK signaling in PDLMSCs. Moreover, IL-17 had no effect on MMP9 expression, but it stimulated uPA and MMP2 gene and protein expression in PDLMSCs through the activation of the ERK1/2 MAPK signaling pathway. The obtained data suggest that IL-17 contributes to ECM degradation in the periodontal ligament by stimulating uPA and MMP2 expression and activity in PDLMSCs. This information is important for understanding periodontal disease development and defining future directions of its treatment.

An update of knowledge on the regulatory role of Treg cells in apical periodontitis

Apical periodontitis (AP) is a prevalent infectious and inflammatory disorder that involves inflammation of periapical tissues and the disintegration of alveolar bone. AP may eventually lead to tooth loss if not timely treated. This disease is caused by pathogenic bacteria in the necrotic pulps and root canals, thereby triggering responses from the innate and adaptive immune system of the periapical tissues. Regulatory T (Treg) cells play a major role in maintaining immune homoeostasis and immunological self-tolerance; however, these only account for roughly 5%-10% of human peripheral CD4⁺ T cells. Several studies have examined the possible role and underlying mechanism of Treg cells in different inflammatory and autoimmune disorders to facilitate the development of novel treatments for these diseases. Recent studies have indicated that Treg cells may gather at the sites of infection, thus limiting the generation of immune responses and bone resorption in the periapical area. This review will summarize studies regarding the presence and regulatory role of Treg cells in AP.

Genetic and Epigenetic Characterization of Pulpal and Periapical Inflammation

Pulpal and periapical diseases affect a large segment of the population. The role of microbial infections and host effector molecules in these diseases is well established. However, the interaction between host genes and environmental factors in disease susceptibility and progression is less well understood. Studies of genetic polymorphisms in disease relevant genes have suggested that individual predisposition may contribute to susceptibility to pulpal and periapical diseases. Other studies have explored the contribution of epigenetic mechanisms to these diseases. Ongoing research expands the spectrum of non-coding RNAs in pulpal disease to include viral microRNAs as well. This review summarizes recent advances in the genetic and epigenetic characterization of pulpal and periapical disease, with special emphasis on recent data that address the pathogenesis of irreversible pulpal pathosis and apical periodontitis. Specifically, proinflammatory and anti-inflammatory gene expression and gene polymorphism, as well as recent data on DNA methylation and microRNAs are reviewed. Improved understanding of these mechanisms may aid in disease prevention as well as in improved treatment outcomes.

Effects of Er,Cr:YSGG and Diode Lasers on Clinical Parameters and Gingival Crevicular Fluid IL-1β and IL-37 Levels in Generalized Aggressive Periodontitis

Aim

The objective of the current study is to analyze the correlation between cytokine levels and periodontal parameters in aggressive periodontitis patients before and after periodontal treatment that was performed by using two different laser therapies.

Materials and Methods

Twenty-six generalized aggressive periodontitis patients were treated with three different methods (SRP, SRP+diode laser, and SRP+Er,Cr:YSGG laser) applied to three different half-jaws in the same patients. Pre- and posttreatment clinical periodontal parameters and GCF IL-1β and IL-37 levels were measured.

Results

There was a statistically significant decrease (p < 0.05) between pretreatment and posttreatment clinical periodontal parameters and IL-1β and IL-37 levels. When the reduction rates of IL-37 and IL-1β levels after treatment were evaluated, the decrease in IL-37 and IL-1β levels after treatment was lowest in the SRP group and highest in the SRP+Er,Cr:YSGG group. In addition, the amount of decrease in IL-1β in SRP+diode and SRP+Er,Cr:YSGG groups was found to be higher than that in IL-37. Furthermore, there was a positive correlation between IL-37 and IL-1β in all groups (p < 0.01).

Conclusion

Er,Cr:YSGG laser is more effective than diode laser for the treatment of aggressive periodontitis. IL-37 and IL-1β are cytokines that function together and thus must be evaluated together.

Interleukin-17 plays a role in pulp inflammation partly by WNT5A protein induction

OBJECTIVE

Our study aimed to investigate the role of interleukin (IL)-17 in dental pulp inflammation and the relationship between WNT5A and IL-17.

METHODS

Immunohistochemical staining was used to detect the expression of tumor necrosis factor-α (TNF-α), WNT5A and IL-17 in pulp tissues. Anti-IL-17 neutralizing antibody was used in rat pulpitis model and to study the role of IL-17 in pulpitis. TNF-α, WNT5A or IL-17 recombinant protein were used to treat human dental pulp cells. RT-PCR, Western blot, and Enzyme linked immunosorbent assay were used to detect the expression of mRNA and protein. Transwell assay was used to measure the migration of THP-1 cells, which is a human monocytic cell line.

RESULTS

IL-17 and WNT5A are co-expressed in TNF-α high-expressed region in human and rat pulpitis tissue. IL-17 mainly contributes to its positive regulatory role in inflammation through up regulate cytokines and mediated macrophages migration. Anti-IL-17 neutralizing antibody can suppress the inflammatory cell infiltration and TNF-α expression in dental pulpitis. TNF-α promotes the expression of IL-17 partly through WNT5A and WNT5A regulates IL-17 expression by mitogen-activated protein kinase (MAPK)-(P38 and ERK) pathway.

CONCLUSIONS

IL-17 acts as an inflammatory mediator in dental pulp inflammation. The expression of IL-17 can be partially regulated by WNT5A.

Inflammatory profile of chronic apical periodontitis: a literature review

Apical periodontitis caused by root canal infection is the most frequent pathological lesion in the jaws, mainly manifested as periapical granulomas and cysts. Understanding of the formation and progression of apical periodontitis as well as the identification of inflammatory biomarkers can help increase the knowledge of pathogenic mechanisms, improve the diagnosis and provide support for different therapeutic strategies. The objective of the present article is to review inflammatory biomarkers such as cytokines, chemokines, inflammatory cells, neuropeptides, RANK/RANKL/OPG system and other inflammatory markers and to relate these systems to the development and progression of pathological conditions related to apical periodontitis.

The Presence and involvement of interleukin-17 in apical periodontitis

Apical periodontitis (AP) is a chronic inflammatory disease characterized by periapical tissue inflammation and destruction of the associated alveolar bone. It is caused by microbial infections within the root canal and the resultant host immune responses in the periapical tissues. The proinflammatory cytokine interleukin (IL)-17 has been shown to play an important role in many inflammatory diseases. There is increasing evidence of the presence of IL-17 in AP, which might be associated with disease pathogenesis. Moreover, several animal studies indicate the potential role of IL-17 in periapical inflammation and the resultant bone resorption in AP. This article reviews recent studies regarding the collective in vitro, in vivo and clinical evidence of the presence and involvement of IL-17 in AP. A search related to IL-17 in apical periodontitis was conducted on PubMed, EMBASE and Web of Science databases using keywords and controlled vocabulary. Two independent reviewers first screened titles and abstracts and then the full texts that were included. A total of 25 papers were identified, of the 25 included articles, 7 involved laboratory studies on cell cultures, 11 involved animal experimentations, and 7 were observational studies using human clinical samples. In conclusion, evidence for the presence of IL-17 in AP from human and animal models is clear. However, there is relatively little information currently available that would highlight the specific role of IL-17 in AP.

Use of micro-computed tomography for the assessment of periapical lesions in small rodents: a systematic review

This systematic review aimed to evaluate the literature on the acquisition-, reconstruction- and analysis parameters of micro-computed tomography (micro-CT) for the assessment of periapical lesions in rats and mice, and to illustrate the effect of variation in these parameters. The PubMed database was searched from 2000 to January 2015 (English-language publications) for reports on the use of micro-CT to evaluate periapical lesions in rats and mice. QUADAS criteria were used to rate the quality of the studies. To illustrate the effect of variations in acquisition-, reconstruction-, and analysis parameters on images of periapical lesions, micro-CT examination of two hemi-mandibles of mice, with periapical lesions around the first molar was undertaken. Twenty-one studies were identified, which analysed periapical lesions in rats or mice using micro-CT. According to the QUADAS, no study was classified as high-, seven were classified as moderate-, and 14 as low quality. The effect of variation in parameters was that voxel size may interfere with image sharpness, reconstruction may interfere with image sharpness and contrast, and inadequate plane orientation may alter the size of the periapical lesion. Nonpersonalized ROIs resulted in areas that were not part of the periapical lesion. Changing the limits of the threshold for bone-tissue visualization increased lesion size. There is no defined protocol for acquiring and analysing micro-CT images of periapical lesions in rats and mice. Furthermore, acquisition-, reconstruction- and analysis parameters are not adequately explained, which may compromise the scientific impact of the studies.

Analysis of Interleukin 17A in periapical abscess and granuloma lesions

Interleukin 17A (IL-17A) is a proinflammatory cytokine responsible for the initiation and propagation of inflammation. One of its actions is the recruitment of neutrophils to the site of infection. The aim of this study was to investigate whether there is association between IL-17A expression and neutrophil infiltration in periapical abscesses and periapical granulomas, as well as to find which type of T lymphocyte effector (CD4+ or CD8+) expresses IL-17A in these lesions. Elastase, CD4, CD8, and IL-17A were analyzed by immunohistochemistry and immunofluorescence, in the biopsies of periapical lesions. Abscess lesions exhibited the highest labeling area for IL-17A (p = 0.011). During double immunofluorescence staining, there were significantly more CD4+/IL-17A+ cells compared to CD8+/IL-17A+ cells, both in the abscesses (p = 0.025) and granulomas (p = 0.011). In conclusion, IL-17A was intensively expressed in periapical abscesses rich in neutrophils. The high percentage of IL-17A in these cases suggests the participation of this cytokine particularly in the acute stages of the inflammatory process of the periapical lesions.

Host response mechanisms in periodontal diseases

Periodontal diseases usually refer to common inflammatory disorders known as gingivitis and periodontitis, which are caused by a pathogenic microbiota in the subgingival biofilm, including Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Tannerella forsythia and Treponema denticola that trigger innate, inflammatory, and adaptive immune responses. These processes result in the destruction of the tissues surrounding and supporting the teeth, and eventually in tissue, bone and finally, tooth loss. The innate immune response constitutes a homeostatic system, which is the first line of defense, and is able to recognize invading microorganisms as non-self, triggering immune responses to eliminate them. In addition to the innate immunity, adaptive immunity cells and characteristic cytokines have been described as important players in the periodontal disease pathogenesis scenario, with a special attention to CD4⁺ T-cells (T-helper cells). Interestingly, the T cell-mediated adaptive immunity development is highly dependent on innate immunity-associated antigen presenting cells, which after antigen capture undergo into a maturation process and migrate towards the lymph nodes, where they produce distinct patterns of cytokines that will contribute to the subsequent polarization and activation of specific T CD4+ lymphocytes. Skeletal homeostasis depends on a dynamic balance between the activities of the bone-forming osteoblasts (OBLs) and bone-resorbing osteoclasts (OCLs). This balance is tightly controlled by various regulatory systems, such as the endocrine system, and is influenced by the immune system, an osteoimmunological regulation depending on lymphocyte- and macrophage-derived cytokines. All these cytokines and inflammatory mediators are capable of acting alone or in concert, to stimulate periodontal breakdown and collagen destruction via tissue-derived matrix metalloproteinases, a characterization of the progression of periodontitis as a stage that presents a significantly host immune and inflammatory response to the microbial challenge that determine of susceptibility to develop the destructive/progressive periodontitis under the influence of multiple behavioral, environmental and genetic factors.

The effect of IL-17 on the production of proinflammatory cytokines and matrix metalloproteinase-1 by human periodontal ligament fibroblasts

OBJECTIVES

To investigate the effects of IL-17 on IL-6, IL-1β, and matrix metalloproteinase (MMP-1) production, and to compare the MMP-1 production between the individual and combined effects of IL-1β and IL-6 in human periodontal ligament fibroblasts (HPDLF).

MATERIALS AND METHODS

Human periodontal ligament fibroblasts were cultured with IL-17 for 0.5, 1, 4, 24, 48, and 72 h, and were cultured with IL-1β, IL-6/sIL-6R, or a combination of IL-1β and IL-6/sIL-6R for 24 h. To measure the mRNA levels of IL-6, IL-1β, and MMP-1, total RNA was extracted from the cultured HPDLF, and a real-time PCR analysis was performed. The protein levels of IL-6, IL-1β, and MMP-1 in supernatants were measured using enzyme-linked immunosorbent assays (ELISAs).

RESULTS

IL-17 significantly increased the expression of IL-6 and MMP-1 mRNA and protein, while IL-17 transiently increased the expression of IL-1β mRNA. The combination of IL-1β and IL-6/sIL-6R induced significantly higher levels of MMP-1 protein than IL-1β alone.

CONCLUSIONS

IL-17 upregulated the production of IL-6 and MMP-1 sequentially in HPDLF. IL-6/sIL-6R may enhance the effects of IL-1β on MMP-1 production. The present results suggest that IL-17 induces MMP-1 production not only directly, but also indirectly by promoting IL-6 production, thus resulting in the degradation of collagens in the PDL.

Periapical cytokine expression in sickle cell disease

INTRODUCTION

Sickle cell anemia (SCA) is the most prevalent genetic disease worldwide. Patients with SCA exhibit increased levels of proinflammatory mediators as part of a permanently activated immunoinflammatory status.

METHODS

The aim of this study was to evaluate the mRNA expression levels of the cytokines interferon (IFN-γ), tumor necrosis factor, interleukin (IL-1β, IL-17A, IL-10), receptor activator for nuclear factor kappa B ligand, and the chemokines CCL2/MCP-1 and CCL5 in the periapical interstitial fluid from SCA individuals compared with healthy individuals. Samples were collected from 12 teeth of SCA patients and 12 non-SCA patients with apical periodontitis. In addition, 12 teeth were sampled from the periapical region of healthy patients with vital pulp (control). The expression of cytokine mRNA was detected by using real-time polymerase chain reaction.

RESULTS

The expression of mRNA for the Th1-associated cytokines IFN-γ, tumor necrosis factor-α, and IL-1β were significantly higher in SCA individuals than in the control individuals (P < .05). Among Th1-associated cytokines, only IFN-γ was significantly increased in non-SCA compared with control patients (vital pulp). The expression of IL-17A mRNA was significant higher in SCA cases than in control samples (P < .05), whereas the IL-10 mRNA expression was significantly increased in SCA and non-SCA individuals when compared with the control group. Similar levels of receptor activator for nuclear factor kappa B ligand, CCL2, and CCL5 mRNA expression were observed in all samples. However, no significant differences were observed in the expression of cytokine or chemokine mRNA between SCA and non-SCA individuals (P > .05).

CONCLUSIONS

The results were able to demonstrate that SCA patients presented prone proinflammatory ability, despite the fact that any differences in periapical immune responses between SCA and non-SCA individuals were not observed.

Simultaneous analysis of T helper subsets (Th1, Th2, Th9, Th17, Th22, Tfh, Tr1 and Tregs) markers expression in periapical lesions reveals multiple cytokine clusters accountable for lesions activity and inactivity status

Previous studies demonstrate that the balance between pro- and anti-inflammatory mediators determines the stable or progressive nature of periapical granulomas by modulating the balance of the osteoclastogenic factor RANKL and its antagonist OPG. However, the cytokine networks operating in the development of periapical lesions are quite more complex than what the simple pro- versus anti-inflammatory mediators' paradigm suggests. Here we simultaneously investigated the patterns of Th1, Th2, Th9, Th17, Th22, Thf, Tr1 and Tregs cytokines/markers expression in human periapical granulomas.

METHODS

The expression of TNF-α, IFN-γ, IL-17A, IL23, IL21, IL-33, IL-10, IL-4, IL-9, IL-22, FOXp3 markers (via RealTimePCR array) was accessed in active/progressive (N=40) versus inactive/stable (N=70) periapical granulomas (as determined by RANKL/OPG expression ratio), and also to compare these samples with a panel of control specimens (N=26). A cluster analysis of 13 cytokine levels was performed to examine possible clustering between the cytokines in a total of 110 granulomas.

RESULTS

The expression of all target cytokines was higher in the granulomas than in control samples. TNF-α, IFN-γ, IL-17A and IL-21 mRNA levels were significantly higher in active granulomas, while in inactive lesions the expression levels of IL-4, IL-9, IL-10, IL-22 and FOXp3 were higher than in active granulomas. Five clusters were identified in inactive lesion groups, being the variance in the expression levels of IL-17, IL-10, FOXp3, IFN-γ, IL-9, IL-33 and IL-4 statistically significant (KW p<0.05). Three clusters were identified in active lesions, being the variance in the expression levels of IL-22, IL-10, IFN-γ, IL-17, IL-33, FOXp3, IL-21 and RANKL statistically significant (KW p<0.05).

CONCLUSION

There is a clear dichotomy in the profile of cytokine expression in inactive and active periapical lesions. While the widespread cytokine expression seems to be a feature of chronic lesions, hierarchical cluster analysis demonstrates the association of TNF-α, IL-21, IL-17 and IFN-γ with lesions activity, and the association of FOXP3, IL-10, IL-9, IL-4 and IL-22 with lesions inactivity.

Promotion of endodontic lesions in rats by a novel extraradicular biofilm model using obturation materials

Although extraradicular biofilm formation is related to refractory periapical periodontitis, the mechanism of extraradicular biofilm development, as well as its effect on periapical lesions, is unknown. Therefore, we aimed to develop an in vivo extraradicular biofilm model in rats and to identify and quantify extraradicular biofilm-forming bacteria while investigating the effect of extraradicular biofilms on periapical lesions. Periapical lesions were induced by exposing the pulpal tissue of the mandibular first molars of male Wistar rats to their oral environment. Four weeks later, gutta-percha points were excessively inserted into the mesial root canals of the right first molars (experimental sites) but not the left first molars (control sites). After 6 and 8 weeks of pulp exposure, the presence of extraradicular biofilms was confirmed histomorphologically, and biofilm-forming bacteria were identified by using classical culture methods. The biofilms were observed in the extraradicular area of the experimental sites. Similar species were detected both inside and outside the root canals. The bacterial count, quantified by real-time PCR assays, in the extraradicular area gradually increased in the experimental sites until 20 weeks after pulp exposure. After 8 weeks of pulp exposure, the periapical lesion volume that was measured by micro-computed tomography was significantly larger in the experimental sites than in the control sites (P < 0.05 by Welch's t test). These results suggest that we developed an extraradicular biofilm model in rats and that extraradicular biofilms affect developing periapical lesions.

IL-17 receptor A signaling is protective in infection-stimulated periapical bone destruction

IL-17 is a pleiotropic cytokine produced by Th17 T cells that induces a myriad of proinflammatory mediators. However, different models of inflammation report opposite functional roles of IL-17 signal in terms of its effects on bone destruction. In this study we determined the role of IL-17RA signal in bone resorption stimulated by dentoalveolar infections. Infrabony resorptive lesions were induced by surgical pulp exposure and microbial infection of mouse molar teeth. IL-17 was strongly induced in periapical tissues in wild-type (WT) mice by 7 d after the infection but was not expressed in uninfected mice. Dentoalveolar infections of IL-17RA knockout (KO) mice demonstrated significantly increased bone destruction and more abscess formation in the apical area compared with WT mice. Infected IL-17RA KO mice exhibited significantly increased neutrophils and macrophages compared with the WT littermates at day 21, suggesting a failure of transition from acute to chronic inflammation in the IL-17RA KO mice. The expression of IL-1 (both α and β isoforms) and MIP2 were significantly upregulated in the IL-17RA KO compared with WT mice at day 21 postinfection. The development of periapical lesions in IL-17RA KO mice was significantly attenuated by neutralization of IL-1β and MIP2. Taken together, these results demonstrate that IL-17RA signal seems to be protective against infection-induced periapical inflammation and bone destruction via suppression of neutrophil and mononuclear inflammation.

Immunoexpression of interleukin 17, transforming growth factor β1, and forkhead box P3 in periapical granulomas, radicular cysts, and residual radicular cysts

INTRODUCTION

Different cell types and cytokines have been identified as contributors to the formation of periapical lesions. In this perspective, this study aimed to evaluate the immunoexpression of interleukin (IL)-17, transforming growth factor (TGF)-β1, and the forkhead box P3 (FoxP3) in periapical lesions, correlating them with the type of lesion, the intensity of the inflammatory infiltrate, and the thickness of the cystic epithelial lining.

METHODS

Twenty periapical granulomas (PGs), 20 radicular cysts (RCs), and 20 residual radicular cysts (RRCs) were submitted to immunohistochemical analysis using anti-IL-17, anti-TGF-β1, and anti-FoxP3 antibodies.

RESULTS

In comparison with PGs and RCs, RRCs exhibited a lower immunoexpression of IL-17 and TGF-β1 (P = .021 and P < .001, respectively). The number of FoxP3+ cells increased in this order: RRCs, RCs, and PGs (P < .001). In comparison with lesions with inflammatory infiltrates grades I and II, lesions with inflammatory infiltrate grade III exhibited a higher number of FoxP3+ cells (P = .002). Similarly, in comparison with lesions with inflammatory infiltrates grades II and III, lesions with inflammatory infiltrate grade I showed a tendency for a lower expression of IL-17 and TGF-β1 (P = .085 and P = .051, respectively). For all groups, there was a positive correlation between the immunoexpressions of IL-17 and TGF-β1 (P < .05). Positive correlations between the number of FoxP3+ cells and the immunoexpressions of IL-17 and TGF-β1 (P < .05) were found only in PGs.

CONCLUSIONS

Th17 and Treg cells seem to interact at the site of injury, suggesting the involvement of proinflammatory and immunoregulatory cytokines in the pathogenesis of periapical lesions.

RNA interference-mediated silencing of Atp6i prevents both periapical bone erosion and inflammation in the mouse model of endodontic disease

Dental caries is one of the most prevalent infectious diseases in the United States, affecting approximately 80% of children and the majority of adults. Dental caries may lead to endodontic disease, where the bacterial infection progresses to the root canal system of the tooth, leading to periapical inflammation, bone erosion, severe pain, and tooth loss. Periapical inflammation may also exacerbate inflammation in other parts of the body. Although conventional clinical therapies for this disease are successful in approximately 80% of cases, there is still an urgent need for increased efficacy of treatment. In this study, we applied a novel gene-therapeutic approach using recombinant adeno-associated virus (AAV)-mediated Atp6i RNA interference (RNAi) knockdown of Atp6i/TIRC7 gene expression to simultaneously target periapical bone resorption and periapical inflammation. We found that Atp6i inhibition impaired osteoclast function in vitro and in vivo and decreased the number of T cells in the periapical lesion. Notably, AAV-mediated Atp6i/TIRC7 knockdown gene therapy reduced bacterial infection-stimulated bone resorption by 80% in the mouse model of endodontic disease. Importantly, Atp6i(+/-) mice with haploinsufficiency of Atp6i exhibited protection similar to that in mice with bacterial infection-stimulated bone erosion and periapical inflammation, which confirms the potential therapeutic effect of AAV-small hairpin RNA (shRNA)-Atp6i/TIRC7. Our results demonstrate that AAV-mediated Atp6i/TIRC7 knockdown in periapical tissues can inhibit endodontic disease development, bone resorption, and inflammation, indicating for the first time that this potential gene therapy may significantly improve the health of those who suffer from endodontic disease.

Expression of a cytokine, interleukin-23, in experimental periapical lesions

AIM

To investigate the expression of interleukin (IL)-23, a new member of the IL-12 family, in experimental periapical lesions.

METHODOLOGY

Periapical lesions were induced in Wistar rats by occlusal surface pulp exposure in mandibular first molars. The rats were randomly sacrificed 0, 7, 14, 21, 28, 35, 42 and 56 days after pulp exposure. The jaws that contained the first molars were obtained and routinely prepared for radiographic, histological, enzyme histochemical, immunohistochemical and double immunofluorescence analyses. Data were analysed by one-way analysis of variance and the Pearson correlation test.

RESULTS

The number of IL-23-positive cells increased from day 7 to day 35 and then gradually decreased. The number of osteoclasts increased and peaked on day 14 and then gradually decreased from day 21 to day 56. A significant positive correlation existed between the number of IL-23 positive cells and the size of bone resorption in periapical lesions from day 7 to day 56 (r = 0.875, P < 0.01).

CONCLUSIONS

Interleukin-23 can be observed and may be associated with inflammatory response and bone resorption in periapical lesions.

Interleukin-17/T-helper 17 cells in an atopic dermatitis mouse model aggravate orthodontic root resorption in dental pulp

Interleukin (IL)-17 is an important mediator of orthodontically induced inflammatory root resorption (OIIRR). However, its role in the dental pulp (DP) has not been studied. The aim of this study was to investigate, using an atopic dermatitis (AD) model, how IL-17 contributes to OIIRR in DP. Atopic dermatitis is the most common IL-17-associated allergic disease. Atopic dermatitis model mice (AD group) and wild-type mice (control group) were subjected to an excessive orthodontic force. The localization of T-helper (Th)17 cells, IL-17, IL-6, and keratinocyte chemoattractant (KC; an IL-8-related protein in rodents) were determined in DP. In addition, CD4+ T cells, including IL-17 production cells, were obtained from patients with AD and from healthy donors, and the effects of IL-17 on the production of IL-6 and IL-8 were investigated using a co-culture of CD4+ T cells with human dental pulp (hDP) cells stimulated with substance P (SP). Immunoreactivity for Th17 cells, IL-17, IL-6, and KC was increased in DP tissue subjected to orthodontic force in the AD group compared with DP tissue subjected to orthodontic force in the control group. The cells obtained from the AD patients displayed increased IL-6 and IL-8 production. These results suggest that IL-17 may aggravate OIIRR in DP.

Inhibiting periapical lesions through AAV-RNAi silencing of cathepsin K

Dental caries, one of the most prevalent infectious diseases worldwide, affects approximately 80% of children and the majority of adults. Dental caries may result in endodontic disease, leading to dental pulp necrosis, periapical inflammation and bone resorption, severe pain, and tooth loss. Periapical inflammation may also increase inflammation in other parts of the body. Although many studies have attempted to develop therapies for this disease, there is still an urgent need for effective treatments. In this study, we applied a novel gene therapeutic approach using recombinant adeno-associated virus (AAV)-mediated RNAi knockdown of Cathepsin K (Ctsk) gene expression, to target osteoclasts and periapical bone resorption in a mouse model. We found that AAV-sh-Cathepsin K (AAV-sh-Ctsk) impaired osteoclast function in vivo and furthermore reduced bacterial infection-stimulated bone resorption by 88%. Reduced periapical lesion size was accompanied by decreases in mononuclear leukocyte infiltration and inflammatory cytokine expression. Our study shows that AAV-RNAi silencing of Cathepsin K in periapical tissues can significantly reduce endodontic disease development, bone destruction, and inflammation in the periapical lesion. This is the first demonstration that AAV-mediated RNAi knockdown gene therapy may significantly reduce the severity of endodontic disease.

Porphyromonas gingivalis induces myocarditis and/or myocardial infarction in mice and IL-17A is involved in pathogenesis of these diseases

OBJECTIVES

Although an association between periodontitis and cardiovascular diseases has been suggested, the role of Porphyromonas gingivalis in cardiovascular diseases is not clear. In this study, we examined whether experimental bacteremia of P. gingivalis causes cardiovascular diseases and investigated the mechanism of pathogenesis of cardiovascular diseases induced by P. gingivalis.

DESIGN

C57BL/6 mice were intravenously inoculated with 2.0 × 10(8)CFU of P. gingivalis A7436 strain. Mice were sacrificed at specified days and their hearts were collected. The collected organs were divided into two halves and used for histological evaluation and cytokine analysis. IL-17A(-/-), IFN-γ(-/-) and TNF-α(-/-) mice were also intravenously inoculated and the histological changes of hearts in mice were examined.

RESULTS

Myocarditis and/or myocardial infarction were observed in mice injected with P. gingivalis. The levels of IL1-β, IL-6, IL-17A, IL-18, TNF-α and IFN-γ mRNA increased significantly after P. gingivalis injection. In particular, high levels of IL-17A and IFN-γ mRNA expression were observed in hearts of mice after P. gingivalis injection in comparison with these levels before injection. Furthermore, the production of IL-17A was detected in hearts of wild-type mice after P. gingivalis injection. In wild-type, TNF-α(-/-) and IFN-γ(-/-) mice, moderate infiltration of neutrophils and monocytes was observed in hearts at 5 days after injection. In contrast, no inflammatory findings were observed in hearts of IL-17A(-/-) mice.

CONCLUSION

We have demonstrated that an experimental bacteremia of P. gingivalis could induce myocarditis and/or myocardial infarction in mice, and IL-17A plays an important role in the pathogenesis of these diseases.

Adaptive immune response in osteoclastic bone resorption induced by orally administered Aggregatibacter actinomycetemcomitans in a rat model of periodontal disease

There is mounting evidence that innate and adaptive immunity are critical for periodontal disease-mediated bone resorption. These studies examined the role of B and CD4 T cells in adaptive immunity of rats infected with Aggregatibacter actinomycetemcomitans (Aa). Sprague-Dawley male rats were fed Aa-containing mash or control-mash for 2 weeks. B and CD4 T cells were obtained from draining lymph nodes at 2, 4 and 12 weeks, postinoculation. Quantitative polymerase chain reaction-based messenger RNA expression was conducted for 89 cytokine family genes. Disease-relevance of the differentially expressed genes was assessed using a biological interaction pathway analysis software. B and CD4 T cells of Aa-infected rats increased and were activated, resulting in enhanced isotype-switched serum immunoglobulin G by 2 weeks postinoculation. Bone resorption was evident 12 weeks after Aa-feeding. In B cells, interleukin-2 (IL-2), macrophage-inhibiting factor, IL-19, IL-21, tumor necrosis factor (TNF), CD40 ligand (CD40L), CD70, bone morphogenetic protein 2 (BMP2), BMP3, and BMP10 were upregulated early; while IL-7, Fas ligand (FasL), small inducible cytokine subfamily E1, and growth differentiation factor 11 (GDF11; BMP11) were upregulated late (12 weeks). BMP10 was sustained throughout. In CD4 T cells, IL-10, IL-16, TNF, lymphotoxin-beta (LTbeta), APRIL, CD40L, FasL, RANKL and osteoprotegerin were upregulated early, whereas IL-1beta, IL-1RN, IL-1F8, IL-24, interferon-alpha1, GDF11 (BMP11), and GDF15 were upregulated late (12 weeks). Adaptive immunity appears crucial for bone resorption. Several of the deregulated genes are, for the first time, shown to be associated with bone resorption, and the results indicate that activated B cells produce BMP10. The study provides a rationale for a link between periodontal disease and other systemic diseases.

Destructive and protective roles of cytokines in periodontitis: a re-appraisal from host defense and tissue destruction viewpoints

Periodontal diseases (PD) are chronic infectious inflammatory diseases characterized by the destruction of tooth-supporting structures, being the presence of periodontopathogens required, but not sufficient, for disease development. As a general rule, host inflammatory mediators have been associated with tissue destruction, while anti-inflammatory mediators counteract and attenuate disease progression. With the discovery of several T-cell subsets bearing distinct immunoregulatory properties, this pro- vs. anti-inflammatory scenario became more complex, and a series of studies has hypothesized protective or destructive roles for Th1, Th2, Th17, and Treg subpopulations of polarized lymphocytes. Interestingly, the "protective vs. destructive" archetype is usually considered in a framework related to tissue destruction and disease progression. However, it is important to remember that periodontal diseases are infectious inflammatory conditions, and recent studies have demonstrated that cytokines (TNF-α and IFN-γ) considered harmful in the context of tissue destruction play important roles in the control of periodontal infection. Therefore, in this review, the state-of-the-art knowledge concerning the protective and destructive roles of host inflammatory immune response will be critically evaluated and discussed from the tissue destruction and control-of-infection viewpoints.

Th17 cytokines in mucosal immunity and inflammation

PURPOSE OF REVIEW

Compelling evidence suggests that the Th17 lineage and other IL-17-producing cells play critical roles in host defense against pathogens at mucosal sites. However, IL-17 can also contribute to inflammatory responses at mucosal sites. In this review, we will discuss the recent progress in our understanding of the role of Th17 and other IL-17-producing cells in defining the fine balance between immunity and inflammation at different mucosal sites. RECENT FNDINGS: Recent findings have highlighted that Th17 cytokines are important for the induction of innate and adaptive host responses and contribute to host defense against pathogens at mucosal sites. More recent developments have probed how the Th17 responses are generated in vivo in response to infections and their requirement in maintaining barrier function at mucosal sites. Most importantly, it is becoming apparent that there is a fine balance between protective and pathological manifestation of Th17 responses at mucosal sites that defines immunity or inflammation.

SUMMARY

In this review, we have summarized the recent advances in our understanding of Th17 cytokines and how they contribute to immunity versus inflammation at mucosal sites.