Effect of interleukin-6 deficiency on the formation of periapical lesions after pulp exposure in mice

B Cells at the Core: Immune Mechanisms and Therapeutic Potentials in Periapical Lesions

INTRODUCTION

Periapical lesions (PLs) are common inflammatory diseases primarily caused by microbial infections within root canals. These infections trigger complex immune responses in periapical tissues, with B lymphocytes playing dual roles: defending against pathogens while also contributing to tissue damage. This highlights the crucial role of B cells in the immunological processes of PLs.

METHODS

A comprehensive review of the literature on B cells in PLs was conducted using PubMed, Web of Science, Scopus, and ScienceDirect databases.

RESULTS

The review included 120 studies that examined the distribution and subtypes of B cells, their dual functions in PLs, and the potential applications of B-cell-related therapies in treating apical periodontitis.

CONCLUSIONS

This review enhances our understanding of the complex immune mechanisms in PLs and aids in the development of new therapeutic approaches from a B-cell perspective.

Effects of natural antimicrobial compounds propolis and copaiba on periodontal ligament fibroblasts, molecular docking, and in vivo study in Galleria mellonella

Root canal treatment addresses infectious processes that require control. Occasionally, the radicular pulp is vital and inflamed, presenting a superficial infection. To preserve pulpal remnants, conservative procedures have gained favor, employing anti-inflammatory medications. This study investigated the effects of propolis (PRO), and copaiba oil-resin (COR) associated with hydrocortisone (H) and compared their impact to that of Otosporin® concerning cytotoxic and genotoxic activity, cytokine detection, and toxicity in the Galleria mellonella model. Human periodontal ligament fibroblasts (PDLFs) were exposed to drug concentrations and evaluated by the MTT assay. Associations were tested from concentrations that did not compromise cell density. Genotoxicity was evaluated through micronucleus counting, while cytokines IL-6 and TGF-β1 were detected in the cell supernatant using ELISA. Molecular docking simulations were conducted, considering the major compounds identified in PRO, COR, and H. Increasing concentrations of PRO and COR were assessed for acute toxicity in Galleria mellonella model. Cellular assays were analyzed using one-way ANOVA followed by Tukey tests, while larval survivals were evaluated using the Log-rank (Mantel-Cox) test (α = 0.05). PRO and COR promoted PDLFs proliferation, even in conjunction with H. No changes in cell metabolism were observed concerning cytokine levels. The tested materials induce the release of AT1R, proliferating the PDFLs through interactions. PRO and COR had low toxicity in larvae, suggesting safety at tested levels. These findings endorse the potential of PRO and COR in endodontics and present promising applications across medical domains, such as preventive strategies in inflammation, shedding light on their potential development into commercially available drugs.

Effectiveness of probiotics in apical periodontitis progression: A scoping review and implications for research

To synthesise the current knowledge on the effects of probiotics in apical periodontitis progression by a scoping review of animal and human studies. Reporting was based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Extension for Scoping Reviews. The literature search and screening was performed on PubMed and Scopus databases by two independent reviewers selecting human and animal studies that evaluated the effectiveness of probiotics in reducing the severity of apical periodontitis. Two animal studies with 3 publications met the eligibility criteria for qualitative synthesis. The most common probiotics were Lactobacillus rhamnosus and Lactobacillus acidophilus orally administered for gavage in Wistar rats with induced apical periodontitis. Overall, probiotics significantly reduced inflammation and bone resorption with an improvement in the apical periodontitis progression. Although results in animal studies are promising, the use of probiotics in apical periodontitis progression requires caution due to the insufficient available evidence.

Inflammatory profile of apical periodontitis exacerbated by cigarette smoke inhalation: Histological and immunohistochemical analysis in rats

AIM

The aim of this study was to evaluate the effects of cigarette smoke inhalation (CSI) on inflammation, pro-inflammatory mediators and haematological parameters in rats with induced apical periodontitis (AP).

METHODOLOGY

Thirty-two 3-month-old male Wistar rats were divided into four experimental groups (n = 8): C-Control; S-rats with CSI; AP-rats with AP; and SAP-rats with CSI + AP. Animals in groups S and SAP inhaled cigarette smoke by remaining inside a smoking chamber for 8 min, three times daily, for 50 days. After 20 days of smoke inhalation, animals in AP and SAP groups had the pulps of the lower right first molar exposed to oral environment for 30 days to induce AP. In these subsequent 30 days, animals in group S and SAP continued with CSI. On Day 50, animals were euthanized and mandibles were histologically processed to assess inflammatory infiltrate, immunohistochemical interleukins (IL-1β, IL-6 and TNF-α), and blood samples collected for laboratory analysis. The Mann-Whitney test was performed for non-parametric data and the pairwise analyses of Student's t-test for parametric data, with a significance level of p < .050.

RESULTS

Inflammatory infiltrate was moderate in AP group and more severe in the SAP (p = .010). The interleukins IL-6, IL-1β and TNF-α were higher in SAP group (p < .001) when compared to the AP group. A greater number of red blood cells (p = .010), haemoglobin (p = .007) and neutrophils (p = .014) were observed in the SAP group in comparison with the AP group.

CONCLUSION

Cigarette smoke inhalation induced a more severe inflammatory infiltrate, with increased levels of pro-inflammatory cytokines and changes in haematological parameters in rats with induced AP. Thus, CSI aggravated AP, exacerbating the inflammatory response.

Selenium ameliorates inflammation by decreasing autophagic flux and mitogen-activated protein kinase signalling on experimentally induced rat periapical lesions

AIM

To reveal the molecular mechanisms that targets mitogen-activated protein kinase (MAPK) signalling and the autophagic flux and to investigate the possible effects of the systemic administration of selenium (Se) on experimentally induced rat periapical lesions.

METHODOLOGY

Thirty adult Sprague-Dawley rats were divided equally into negative control, positive control and Se groups. In the positive control and Se groups, the pulp chambers of their mandibular first molars were exposed to the oral environment to induce periapical lesions The Se group received daily intraperitoneal injections of Se at a dose of 0.1 mg kg^-1 . After 28 days, the amount of bone destruction; severity of inflammation; penetration of microorganisms along the root canal; collagen degradation in periodontal ligament; interleukin (IL)-6, hypoxia-inducible factor-1 (HIF-1), cyclooxygenase-2 (COX-2) and caspase-3 expression; autophagic flux; and p38 MAPK signalling were evaluated using radiographic, histopathological, Gram staining, picrosirius red stain, immunohistochemical, quantitative real-time polymerase chain (qRT-PCR) and Western blot methods, respectively. These data were analysed through the Kruskal-Wallis and Dunnett's tests (p < .05).

RESULTS

The area of radiographic periapical bone loss, histopathological scores, the area of periapical bone loss and the scores for the bacteria localisation, the intensity of immunohistochemical staining for IL-6, HIF-1, COX-2 and caspase-3 in the Se group was significantly less than those of the positive control group (p < .01). The mRNA expression levels of Beclin-1, Atg3, Atg5, Atg7 and Atg16L1 were lower in the Se group than in the positive control group (p < .01). The protein expressions of Beclin-1, Atg5 and LC3-II, the phosphorylation ratio of the p38 MAPK and the ratios of LC3II/LC3I were significantly higher (p < .05) in the positive control and Se groups. On the contrary, the expression of the p62/SQSTM1 protein was significantly lower (p < .05) in the positive control and Se groups than in the negative control group.

CONCLUSION

The induction of periapical lesions in rats increased autophagic flux and activated p38 MAPK signal transduction processes. Se suppressed the inflammatory process, reduced bone destruction and both the autophagic flux and p38 MAPK activation.

Comparison of EASYDO ACTIVATOR, passive ultrasonic, and needle irrigation techniques on the treatment of apical periodontitis: a study in rats

OBJECTIVES

To evaluate the long-term therapeutic effect of EASYDO ACTIVATOR, passive ultrasonic irrigation, and needle irrigation in experimental apical periodontitis in rats.

MATERIALS AND METHODS

Sprague-Dawley male rats were used to produce periapical lesions. The pulp chambers of the bilaterally first mandibular molars were exposed and left open for 21 days. The rats were divided into four groups according to different irrigation protocols. Seven days after irrigation, the mandibles were removed for micro-CT, histological, and immunohistochemical analysis. Serum levels of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) were assessed by enzyme-linked immunosorbent assays (ELISA). Statistical data were analyzed by one-way analysis of variance (ANOVA) with LSD tests.

RESULTS

The passive ultrasonic irrigation and EASYDO ACTIVATOR groups had the smallest apical lesions compared to the other groups (P < 0.05), while the needle irrigation group had smaller lesions than the control group (P < 0.05). The EASYDO ACTIVATOR group had less inflammation infiltration compared to the control and needle irrigation groups (P < 0.05). The control and needle irrigation groups had more TNF-α expression compared to the passive ultrasonic irrigation and EASYDO ACTIVATOR groups (P < 0.05). The lowest IL-6 expression was observed in the EASYDO ACTIVATOR group. The EASYDO ACTIVATOR group had the lowest serum level of TNF-α than other groups (P < 0.05). IL-6 expression was significantly lower in the EASYDO ACTIVATOR group in comparison with the control and needle irrigation groups (P < 0.05).

CONCLUSIONS

EASYDO ACTIVATOR can significantly reduce the apical lesions and decrease the inflammatory response around the periapical area.

CLINICAL RELEVANCE

EASYDO ACTIVATOR is recommended for clinical application.

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.

Single nucleotide polymorphisms as a predisposing factor for the development of apical periodontitis-An umbrella review

BACKGROUND

The interaction between heredity and different environmental factors in the modification of apical periodontitis (AP) susceptibility and prediction of its progression remain poorly elucidated.

OBJECTIVES

This umbrella review aimed to (i) analyse the available relevant systematic reviews in an attempt to determine the association between genotype and allelic distribution of different single-nucleotide polymorphisms (SNPs) and the development of AP, (ii) report deficiencies and gaps in knowledge in this area and (iii) present recommendations to conduct future clinical studies and systematic reviews.

METHODS

A literature search was conducted using Clarivate Analytics' Web of Science, Scopus, PubMed and Cochrane Database of Systematic Reviews, from inception to October 2021, with no language restrictions, including a grey literature search. Systematic reviews with/without meta-analysis evaluating genotype and allelic distribution of different SNPs between adult patients with/ without AP were included. All other type of studies were excluded. The methodological quality was assessed using the A MeaSurement Tool to Assess systematic Reviews (AMSTAR)-2 tool. Two independent reviewers were involved in study selection, data extraction and appraising the included reviews; disagreements were resolved by a third reviewer.

RESULTS

The current study includes five systematic reviews. Three reviews performed meta-analysis. Three reviews were graded by AMSTAR 2 as 'critically low' quality, whereas the other two were graded as 'low' and 'moderate' quality. Two reviews indicated that carriers of specific genotypes and alleles of tumour necrosis factor-alpha (TNF-α) -308 G > A and interleukin 1-beta (IL-1β) + 3954 C/T gene polymorphisms are more susceptible to an acute and persistent form of AP. However, high heterogeneity was observed.

DISCUSSION

The statistical heterogeneity within included systematic reviews was a consequence of clinical and methodological diversity amongst primary studies. Although some of the included reviews suggested that carriers of specific genotype and/or allele of TNF-α -308 G > A and IL-1β + 3954 C/T SNPs are more susceptible to AP, their conclusions should be interpreted with caution.

CONCLUSIONS

No candidate genes could be identified as a definitive genetic risk or protective factor for the development and progression of AP, and further high-quality genome-wide association studies are warranted.

Proteomic profiling reveals engineered chitosan nanoparticles mediated cellular crosstalk and immunomodulation for therapeutic application in apical periodontitis

Macrophages (MQ) are major constituents of chronically inflamed periapical tissues in apical periodontitis. This study aimed to investigate the immunomodulatory effect of engineered bioactive chitosan-based nanoparticles (CSnp) antibiofilm medication on MQ cocultured with periodontal ligament fibroblasts (PdLF). Cells viability, spreading, PdLF migration, and intracellular CSnp uptake were characterized. Tandem Mass Tag-based proteomics was applied to analyze MQ global protein expression profiles after interaction with Enterococcus faecalis biofilm, CSnp-treated biofilm, and CSnp. Secreted inflammatory mediators were analyzed. Following bioinformatics analyses, candidate proteins were validated via targeted proteomics. CSnp maintained cells viability, increased MQ spreading, and PdLF migration (p < 0.05). Transmission electron micrographs demonstrated CSnp internalization via macropinocytosis, clathrin-mediated endocytosis, and phagocytosis. Proteomic analysis revealed that CSnp-treated biofilm upregulated proteins (>1.5-folds, p < 0.05) showed functional enrichment in the pathway of metal sequestration by antimicrobial proteins, while downregulated proteins showed enrichment in ferroptosis. CSnp upregulated proteins exhibiting antioxidant and immunoregulatory properties. Upregulation of SERPINB1 by CSnp (>1.5-folds, p < 0.05) was validated. CSnp-treated biofilm reduced pro-inflammatory IL-1β and nitric oxide but enhanced anti-inflammatory IL-10 and TGF-β1 (p < 0.05). Internalized engineered bioactive CSnp reprogrammed MQ proteomic and cytokine profiles to modulate biofilm-mediated inflammation, and prompted PdLF migration, emphasizing its potential to regulate healing process in the treatment of apical periodontitis.

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CSnp internalized via macropinocytosis, clathrin-mediated endocytosis, and phagocytosis.

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Enterococcus faecalis biofilm altered macrophage proteomic profile.

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Macrophage proteome upon CSnp-treated biofilm interaction was distinct from biofilm.

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CSnp upregulated proteins with immunoregulatory and antioxidant activities.

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CSnp reduced proinflammatory but increased anti-inflammatory mediators.

Influence of Bacterial Profiles in Cytokine and Clinical Features of Endodontic Disease

INTRODUCTION

We verified the association between selected bacterial profiles and levels of cytokines, chemokines, and the expression of signs and symptoms of primary endodontic infection with apical periodontitis.

METHODS

Samples were collected from 21 root canals, and macrophages were stimulated for 24 hours. Tumor necrosis factor alpha (TNF-α), interleukin (IL)-6, IL-10, IL-12p70, interferon gamma, and chemokine (C-C motif) ligand 2 (CCL2) were measured using cytometric bead array. We investigated the overlapping networks between cytokines and chemokines with regression analysis. Checkerboard DNA-DNA hybridization was used to assess 40 target bacteria species. Using factor analysis, bacterial species aggregated in 2 factors. The association of bacteria species-based factors on cytokine and chemokine levels and clinical features was estimated with regression analysis.

RESULTS

A negative relationship between IL-10 (anti-inflammatory cytokine) and CCL2, TNF-α, and IFN-γ (proinflammatory cytokines) (all P < .05) was observed. CCL2 was positively correlated with TNF-α (P < .01). Thirty-eight bacteria species were detected in primary endodontic infection with apical periodontitis. The first bacteria species-based factor was associated with the size of the radiolucent area (coefficient = 15.42) and tenderness to percussion/pain on palpation (coefficient = 20.79). The second factor was associated with CCL2 levels (coefficient = 1.28).

CONCLUSIONS

Different bacterial profiles can be differentially related to the expression of inflammatory proteins and the experience of clinical features.

Presence of langerhans cells, regulatory T cells (Treg) and mast cells in asymptomatic apical periodontitis

Asymptomatic Apical Periodontitis is essentially an inflammatory disease of microbial aetiology. Association and function of the cell components involved, or specific inductive factors and growth mediators associated with development, maintenance and resolution of the periapical lesions are still unknown. The objective of this study was to evaluate the concentration of Regulatory T cells (FoxP3+; Treg), Langerhans cells (CD1a+; LC) and mast cells in asymptomatic apical periodontitis. 73 cases were selected: 30 periapical granulomas, 29 radicular cysts and 14 residual cysts. All groups were submitted to morphological analysis for classification of inflammatory infiltrate and thickness of the epithelial lining as well as to immunohistochemical analysis for detection of LC and Treg cells. Toluidine blue staining was used for detecting mast cells. Analysis showed higher mean numbers of LC (8.2 cells/0.2mm2), and Treg cells in radicular cysts (5.910 cells/0.2mm2). As for mast cells, it was found that radicular cysts had a higher mean number of these cells compared to other periapical lesions (12.68 cells/0.2mm2). The association between thickness of the epithelial lining and inflammatory cells showed that the presence of hypertrophic epithelium in radicular cysts presented higher density of LC. The number of LC and Treg cells play an important role in the control of the inflammatory micro-environment in periapical granulomas and radicular cysts, respectively. The presence of mast cells in radicular cysts may be associated with progression of the lesion. Knowledge regarding the inflammatory cell profile is therefore essential for a better understanding of the pathogenesis of asymptomatic periapical periodontitis.

The importance of inflammatory biomarkers, IL-6 and PAPP-A, in the evaluation of asymptomatic apical periodontitis

To examine the use of IL-6 and PAPP-A along with the new imaging for scoring methods to determine the severity of apical periodontitis (AP). The scoring of disease severity in 121 patients with AP, using dental radiographs, was based on "The Apical Periodontitis Grading Scale" (APGS), as those having 1 tooth with AP and severity of 3-4 were classified as grade 1 (mild); those having > 1 tooth and severity of 3-4 as grade 2 (moderate) and those with at least one tooth with a severity of 5 as grade 3 (severe). 45 systematically and orally healthy volunteers were selected as the control group (grade 0). Dental demographic data of all participants were recorded. Besides, venous blood samples were collected to study their complete blood count and levels of IL-6 and PAPP-A. Both NLR and PAPP-A levels of the grade 3 AP patients were found significantly higher than those of the control group and grade 1 and grade 2 AP patients (2.55 ± 1.40 vs 1.98 ± 1.05, 1.94 ± 0.58 and 1.86 ± 0.50; 0.606 ± 0.211 vs 0.422 ± 0.273, 0.447 ± 0.224 and 0.436 ± 0.242, p < 0.01, respectively). AP grades identified by the new scoring system were moderately correlated with IL-6 levels (Spearman r = 0.4168, p < 0.001). The risk of patients with IL-6 levels above 12.5 pg/ml to develop AP (relative risk) was found to be 2.19 times higher than that in those with lower IL-6 levels (98% Cl 1.233-3.905, p < 0.0024). APGS classification suggested to determine AP severity was found to be significantly correlated with levels of inflammatory markers IL-6 and PAPP-A.

Systemic administration of probiotics reduces the severity of apical periodontitis

AIM

To evaluate the effect of systemic administration of probiotics on the severity of apical periodontitis (AP).

METHODOLOGY

Twenty-four male Wistar rats were used. AP was induced in the maxillary left/right first molars. The animals were arranged into groups: Control, Lactobacillus rhamnosus, and Lactobacillus acidophilus. Probiotics were administered orally for gavage (10⁹ colony-forming units diluted in 5 mL of water for 30 days) during the development of AP. After 30 days, cardiac puncture was performed to analyse the complete blood count. Moreover, microbiological analysis of the root canal contents and saliva was performed. Then, the animals were euthanized and the jaw removed for histopathological and IL-10, IL-1β and IL-6 immunolabeling analyses. After the Shapiro-Wilk test of normality, the Kruskal-Wallis followed by Dunn's test was performed for nonparametric data, and analysis of variance followed by the Tukey test was performed for parametric data (P < 0.05).

RESULTS

No significance difference was observed in the blood profiles and in the counts of microorganisms from the saliva samples among the groups (P > 0.05). Total microorganism counts in the root canal, the inflammatory infiltrate and the immunostaining for IL-1β and IL-6 in AP were significantly lower in the probiotic groups when compared with the control group (P < 0.05). IL-10 was significantly more immunolabled in the probiotic groups than in the control group (P < 0.05).

CONCLUSION

Supplementation with probiotics (Lactobacillus rhamnosus and Lactobacillus acidophilus) had a significant effect on the severity of apical periodontitis in rats, demonstrating the anti-inflammatory effect of probiotics on the development of apical periodontitis.

MicroRNA-181b-5p modulates tumor necrosis factor-α-induced inflammatory responses by targeting interleukin-6 in cementoblasts

Tooth cementum is a bone-like mineralized tissue and serves as a microbial barrier against invasion and destruction. Cementum is also responsible for tooth stability and defending pulp from outside stimuli, which is formed by cementoblasts. Although it is crucial for periodontal and periapical diseases, the mechanisms underlying the pathophysiological changes of cementoblasts and their inflammatory responses remain unclear. MiR-181b is found to modulate vascular inflammation and endotoxin tolerance. In this study, miR-181b-5p was downregulated in tumor necrosis factor-α (TNF-α)-stimulated cementoblasts, whereas proinflammatory molecules increased. The mouse periapical lesions have similar results, which imitate an inflammatory environment for cementoblasts in vivo. The bioinformatics analysis and dual luciferase reporter assay suggested that miR-181b-5p targeted interleukin-6 (IL-6). Overexpressing miR-181b-5p negatively regulated IL-6 and proinflammatory chemokine. Western blot analysis and luciferase activity reporter assay verified that miR-181b-5p weakened the NF-κB activity. Hence, miR-181b-5p moderated proinflammatory chemokine production by targeting IL-6 in cementoblasts and NF-κB signaling pathway was involved. Furthermore, miR-181b-5p promoted cementoblast apoptosis, which may enhance the resolution of inflammation. Overall, our data revealed that miR-181b-5p was a negative regulator of TNF-α-induced inflammatory responses in cementoblasts.

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.

Immunological profile of teeth with inflammatory periapical disease from chronic liver disease patients

AIM

To evaluate the mRNA expression levels of the cytokines interferon-γ, tumour necrosis factor-α, interleukin (IL)-1β, IL-10, IL-6, VEGF, and AGT and the chemokine CCL2/MCP-1 in periapical interstitial fluid associated with root canal infections before and after the reduction of the bacterial load using a cleaning procedure.

METHODOLOGY

The case group included 11 patients with chronic liver disease, and the control group included 11 healthy patients. Clinical samples were taken from teeth with pulp necrosis. After cleaning and drying the canal, three paper points were introduced into the root canal and passed through the root apex (2 mm) into the periapical tissues for 1 min. The samples were collected immediately after root canal cleaning and 7 days later to characterize those gene expression levels using real-time PCR. The data were subjected to the Shapiro-Wilk and the Wilcoxon tests.

RESULTS

In the control group, significantly increased expression of the pro-inflammatory cytokines IFN-γ and TNF-α was observed in teeth with restrained bacterial loads (day 7) (P < 0.05). Similarly, increased TNF-α expression was found on day 7 in the liver group (P < 0.05). No differences were observed in the expression levels of the IL-1β, IL-10 and, IL-6, MCP-1/CCL-2 and VEGF between the first collection (day 0) and second collection (day 7), over time in either group.

CONCLUSION

Chronic liver disease patients exhibited sufficient immunologic ability showing relatively similar expression levels of cytokines, chemokines and angiogenic factors in periapical samples compared with the responses from no-chronic liver disease patients. The outcomes of this study suggest that liver impairment did not compromise the periapical immune response.

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.

Targeted salivary biomarkers for discrimination of periodontal health and disease(s)

Generally, clinical parameters are used in dental practice for periodontal disease, yet several drawbacks exist with the clinical standards for addressing the needs of the public at large in determining the current status/progression of the disease, and requiring a significant amount of damage before these parameters can document disease. Therefore, a quick, easy and reliable method of assessing and monitoring periodontal disease should provide important diagnostic information that improves and speeds treatment decisions and moves the field closer to individualized point-of-care diagnostics.

OBJECTIVE

This report provides results for a saliva-based diagnostic approach for periodontal health and disease based upon the abundance of salivary analytes coincident with disease, and the significant progress already made in the identification of discriminatory salivary biomarkers of periodontitis.

METHODS

We evaluated biomarkers representing various phases of periodontitis initiation and progression (IL-1ß, IL-6, MMP-8, MIP-1α) in whole saliva from 209 subjects categorized with periodontal health, gingivitis, and periodontitis.

RESULTS

Evaluation of the salivary analytes demonstrated utility for individual biomarkers to differentiate periodontitis from health. Inclusion of gingivitis patients into the analyses provided a more robust basis to estimate the value of each of these analytes. Various clinical and statistical approaches showed that pairs or panels of the analytes were able to increase the sensitivity and specificity for the identification of disease.

CONCLUSIONS

Salivary concentrations of IL-1ß, IL-6, MMP-8, MIP-1α alone and in combination are able to distinguish health from gingivitis and periodontitis. The data clearly demonstrated a heterogeneity in response profiles of these analytes that supports the need for refinement of the standard clinical classifications if we are to move toward precision/personalized dentistry for the twenty-first century.

Early Cytokine Response to Infection with Pathogenic vs Non-Pathogenic Organisms in a Mouse Model of Endodontic Infection

Using the subcutaneous chamber model of infection, we showed previously that a mixture of four endodontic pathogens (EP: P. intermedia, F. nucleatum, S. intermedius and P. micra) are able to persist without clearance for up to seven days, while a non-pathogenic oral species, S. mitis, was substantially cleared in this time. Here we have compared the cytokine response inside the chambers against these microorganisms. A majority of cytokines tested (17/24) showed different patterns of expression. Several cytokines had a peak of expression at 2 h after infection in response to the EP, while none showed this pattern in S. mitis infections. Chemokines were uniformly present at similar or higher levels in response to S. mitis, with redundant expression of CXCR2 ligands, while several growth/survival factors were present at higher levels in EP infections. Protease activity expressed by EP may be responsible for the lower levels of some chemokines. T-cell associated cytokines were in general expressed at extremely low levels, and did not differ between the two infections. The inflammatory markers IL-6, IL-1α and IL1-β were expressed at similar levels in both infections at early times, while TNFα was preferentially present in S. mitis infections. In EP infected chambers, reciprocal changes in levels of IL-6 and IL-1α were observed at later times suggesting a switch in the inflammatory response. Analysis of the cytokine response to infection with the individual species from the EP mix suggests that P. intermedia drives this inflammatory switch. Together these results show a surprising level of divergence of the host response to pathogenic and non-pathogenic organisms associated with oral infections, and supports a dominant effect of P. intermedia in polymicrobial endodontic infections.

C-reactive protein expression is up-regulated in apical lesions of endodontic origin in association with interleukin-6

INTRODUCTION

C-reactive protein (CRP) is the prototype component of acute-phase proteins induced ultimately by interleukin (IL)-6 in the liver, but it is unknown whether periradicular tissues locally express CRP. The present study aimed to identify whether CRP messenger RNA synthesis occurs in situ within apical lesions of endodontic origin (ALEOs) and healthy periodontal ligament and its association with IL-6 and to determine their protein levels and tissue localization.

METHODS

Patients with asymptomatic apical periodontitis and healthy volunteers presenting at the School of Dentistry, University of Chile, Santiago, Chile, were enrolled. ALEOs and healthy teeth were obtained and processed for either immunohistochemistry and double immunofluorescence to assess IL-6 and CRP tissue localization, whereas healthy periodontal ligaments were processed as controls for real-time reverse-transcription polymerase chain reaction for their RNA expression levels and multiplex assay to determine their protein levels. Statistic analysis was performed using the unpaired t test or Mann-Whitney test according to data distribution and Pearson correlation.

RESULTS

IL-6 and CRP were synthesized in ALEOs, whereas their RNA expression and protein levels were significantly higher when compared with healthy periodontal ligament. IL-6 and CRP immunolocalized to the inflammatory cells, vascular endothelial cells, and mesenchymal cells. Both, IL-6 and CRP colocalized in ALEOs, and a positive correlation was found between their expression levels (P < .05).

CONCLUSIONS

IL-6 and CRP messenger RNA are constitutively expressed in periodontal ligament and up-regulated in ALEOs along with higher protein levels. Given their pleiotropic effects, IL-6 and CRP protein levels in apical tissues might partially explain the development and progression of ALEOs as well as potentially asymptomatic apical periodontitis-associated systemic low-grade inflammation.

Absence of interleukin 22 affects the oral microbiota and the progression of induced periapical lesions in murine teeth

AIM

To evaluate the absence of IL-22 on the progression of periapical lesions in wild-type (WT) and IL-22 knockout (IL-22 KO) mice.

METHODOLOGY

The evaluation of the oral microbial profile of mice was performed by Checkerboard DNA-DNA hybridization from saliva samples. Periapical lesions were induced in manbibular first molars by pulpal exposure and evaluated after 7, 21 and 42 days (n = 15). Haematoxylin-eosin-stained sections were analysed under conventional and fluorescence microscopy to evaluate the tissue features and size of periapical lesions and tartrate-resistant acid phosphatase histoenzymology (TRAP), Brown & Brenn staining and immunohistochemistry. The scores of the number of bacterial cells present in the oral cavity were analysed by the Mann-Whitney test, and the results and comparisons for periapical lesion size and number of osteoclasts were subjected to one-way anova and Bonferroni's post-test (α = 0.05).

RESULTS

Significant differences were observed for bacterial load between the groups of animals for 6 bacterial species (P < 0.05), with five species found in higher levels in the WT group, and one in the IL-22 KO group. WT mice had significantly larger periapical lesions (P < 0.05) between 7 and 42 days and between 21 and 42 days, with an increase in the mean size and number of osteoclasts. IL-22 KO mice had an increase in periapical lesion size and number of osteoclasts between 7 and 21 days (P < 0.05). No differences were found between bacteria localization in the root canal system between the experimental groups. Small variations related to the location of immunostaining were found between the groups.

CONCLUSION

This study revealed differences in the composition of oral microbiota between mice that may be taken into account in the susceptibility to infections and development of periapical lesions. The absence of IL-22 in mice resulted in smaller periapical lesions with fewer osteoclasts at the final experimental period, suggesting the participation of IL-22 in the host immune and inflammatory response to a periradicular infection.

Clinical investigation of bacterial species and endotoxin in endodontic infection and evaluation of root canal content activity against macrophages by cytokine production

INTRODUCTION

This study investigated the presence of different Gram-negative bacterial species and the levels of endotoxins found in primary endodontic infection (PEI), determining their stimulation ability against macrophages through the levels of interleukin (IL)-1, IL-6, IL-10, and tumor necrosis factor alpha (TNF-α), and evaluated their relationship with clinical and radiographic findings.

MATERIAL AND METHODS

Samples were taken from 21 root canals with primary endodontic infection with apical periodontitis (PEIAP). Molecular techniques were used for bacterial detection. Limulus amebocyte lysate assay was used to measure endotoxins. Pro-inflammatory cytokines were measured by ELISA assay.

RESULTS

All samples were positive for bacterial DNA (21/21). Prevotella nigrescens (57.2 %) was the most frequent species. Higher levels of endotoxins were found in teeth with pain on palpation and exudation (all p < 0.05). Positive correlations were found between endotoxins and the levels of TNF-α and IL-1β, whereas a negative correlation was found between endotoxin and the amount of IL-10 (p < 0.05). Endotoxin levels were found to be a risk factor for exudation and increased the number of Gram-negative bacterial species for the presence of a larger area of bone destruction (all p < 0.05).

CONCLUSION

A wide variety of Gram-negative bacterial species are involved in primary endodontic infection, with participation of different Treponema species. Thus, the levels of endotoxins and the number of Gram-negative bacteria species present in root canals were considered risk factors for the severity of endodontic infection.

CLINICAL RELEVANCE

The present study revealed that Gram-negative bacterial species and endotoxins play an important role in the development of signs/symptoms and the severity of bone destruction, this knowledge is essential for the establishment of an effective therapy.

The role of IL-6 on apical periodontitis: a systematic review

The aim of this review was to examine current knowledge of the role of interleukin-6 (IL-6) in apical periodontitis (AP) pathogenesis as an inflammatory or pro-inflammatory cytokine. It also looked at whether IL-6 could serve as a measure for differential diagnosis or as a biomarker that can further predict the progression of bone resorption. A systematic review relating to AP and IL-6 was made via PubMed, BIOSIS, Cochrane, EMBASE and Web of Science databases using keywords and controlled vocabulary. Two independent reviewers first screened titles and abstracts and then the full texts. The reference lists of the identified publications were examined for additional titles. Eighteen papers were studied in total. In vitro studies (n = 6) revealed that IL-6 is present in AP, and its levels are proportional to the size of the periapical lesions. Neutrophils and macrophages resident in these lesions can produce IL-6 in vitro after a bacterial stimulus. Animal studies (n = 5) showed that IL-6 is present in AP and that osteoblasts can produce IL-6 in vivo. On the other hand, two studies using IL-6 knockout mice revealed larger periapical lesions when compared with control groups, demonstrating IL-6's role as an anti-inflammatory cytokine. In human studies (n = 7), IL-6 was identified in AP, and its levels were higher in symptomatic, epithelialized and large lesions than in asymptomatic and small lesions. These data lead to the conclusion that IL-6 may play a pro-inflammatory role, increasing its levels and reabsorbing bone in the presence of infections. When IL-6 is not present, other cytokines such as IL-1 and TNF-α induce bone resorption. Further studies about the relationship between AP development and the cytokine network must be performed to establish the exact role of each cytokine in the inflammatory process.

Distribution of mast cells and macrophages and expression of interleukin-6 in periapical cysts

INTRODUCTION

Mast cells and macrophages are important components of the inflammatory infiltrate found in inflammatory periapical diseases. Several cytokines participate in the mechanisms of inflammation, tissue repair, and bone resorption associated with periapical cysts. The aim of the present study was to evaluate the distribution of mast cells and macrophages and the expression of interleukin-6 (IL-6) in periapical cysts.

METHODS

Thirty periapical cysts were selected for the study, and clinical, demographic, and gross information from the cases was obtained from the laboratory records. Five-micrometer sections stained with hematoxylin-eosin were reviewed for analysis of the microscopic features of the cysts, and 3-μm sections on silanized slides were used for immunohistochemical reactions with anti-tryptase, anti-CD68, and anti-IL-6.

RESULTS

There was no statistically significant difference in the mean number of mast cells and macrophages when comparing superficial and deep regions of the fibrous capsule of the cysts. Mean number of mast cells on the superficial region of the fibrous capsule was higher in cysts showing intense superficial inflammation and exocytosis. Macrophages were more commonly found in areas showing IL-6 expression, and IL-6 was less expressed in deep regions of the fibrous capsule in cysts showing greater gross volume.

CONCLUSIONS

The results reinforced the participation of mast cells and macrophages in the pathogenesis of periapical cysts and suggested that IL-6 is not the major bone resorption mediator in larger periapical cysts.

Correlation between clinical/radiographic features and inflammatory cytokine networks produced by macrophages stimulated with endodontic content

INTRODUCTION

Macrophages are highly activated by endodontic contents. This study investigated the correlation between different clinical signs/symptoms and radiographic features according to the levels of interleukin (IL)-1β, tumor necrosis factor α (TNF-α), IL-6, IL-10, prostaglandin E(2) (PGE(2)), and their networks produced by endodontic content-stimulated macrophages collected from primary endodontic infection with apical periodontitis (PEIAP).

METHODS

Samples were taken from 21 root canals with PEIAP by using paper points. The presence of exudate (EX), pain on palpation (POP), tenderness to percussion (TTP), and the size of the radiographic lesion (SRL) were recorded. Polymerase chain reaction (16S rDNA) was used for bacterial detection and limulus amebocyte lysate (LAL) assay for endotoxin measurement. Raw 264.7 macrophages were stimulated with bacterial contents during 24 hs. The amounts of IL-1β, TNF-α, IL-6, IL-10 and PGE(2) were measured by enzyme-linked immunosorbent assay. Log-based data were correlated by multiple logistic regression (P < .05).

RESULTS

Bacteria and endotoxin were detected in 100% of the samples. IL-6 and TNF-α were positively correlated with SRL and EX, respectively (P < .05). Clinical signs/symptoms and radiographic findings were set as dependent variables for EX-positive correlations between PGE(2), IL-1β, and TNF-α (P < .05), whereas IL-6 and PGE(2) were positively correlated to each other in POP but negatively correlated in SRL (P < .05). When POP and TTP-POP were set as dependent variables, different cytokine networks were found.

CONCLUSIONS

Our findings suggest different roles for each cytokine in the development of apical periodontitis, whose effects of overlapping networks depend on the signs/symptoms and radiographic features found in endodontic infection.

Pathogenesis of apical periodontitis: a literature review

OBJECTIVES

This review article discusses the host response in apical periodontitis with the main focus on cytokines, produced under this pathological condition and contributing to the degradation of periradicular tissues. The pace of research in this field has greatly accelerated in the last decade. Here we provide an analysis of studies published in this area during this period.

MATERIAL AND METHODS

Literature was selected through a search of PubMed electronic database. The keywords used for search were pathogenesis of apical periodontitis cytokines, periapical granuloma cytokines, inflammatory infiltrate apical periodontitis. The search was restricted to English language articles, published from 1999 to December 2010. Additionally, a manual search in the cytokine production, cytokine functions and periapical tissue destruction in the journals and books was performed.

RESULTS

In total, 97 literature sources were obtained and reviewed. The topics covered in this article include cellular composition of an inflammatory infiltrate in the periapical lesions, mechanisms of the formation of the innate and specific immune response. Studies which investigated cytokine secretion and functions were identified and cellular and molecular interactions in the course of apical periodontitis described.

CONCLUSIONS

The abundance and interactions of various inflammatory and anti-inflammatory molecules can influence and alter the state and progression of the disease. Therefore, periapical inflammatory response offers a model, suited for the study of many facets of pathogenesis, biocompatibility of different materials to periapical tissues and development of novel treatment methods, based on the regulation of cytokines expression.

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

Both lesions of endodontic origin and periodontal diseases involve the host response to bacteria and the formation of osteolytic lesions. Important for both is the upregulation of inflammatory cytokines that initiate and sustain the inflammatory response. Also important are chemokines that induce recruitment of leukocyte subsets and bone-resorptive factors that are largely produced by recruited inflammatory cells. However, there are differences also. Lesions of endodontic origin pose a particular challenge since that bacteria persist in a protected reservoir that is not readily accessible to the immune defenses. Thus, experiments in which the host response is inhibited in endodontic lesions tend to aggravate the formation of osteolytic lesions. In contrast, bacteria that invade the periodontium appear to be less problematic so that blocking arms of the host response tend to reduce the disease process. Interestingly, both lesions of endodontic origin and periodontitis exhibit inflammation that appears to inhibit bone formation. In periodontitis, the spatial location of the inflammation is likely to be important so that a host response that is restricted to a subepithelial space is associated with gingivitis, while a host response closer to bone is linked to bone resorption and periodontitis. However, the persistence of inflammation is also thought to be important in periodontitis since inflammation present during coupled bone formation may limit the capacity to repair the resorbed bone.

Inflammation and uncoupling as mechanisms of periodontal bone loss

Periodontal disease is characterized by both inflammation and bone loss. Advances in research in both these areas have led to a new appreciation of not only each field but also the intimate relationship between inflammation and bone loss. This relationship has resulted in a new field of science called osteoimmunology and provides a context for better understanding the pathogenesis of periodontal disease. In this review, we discuss several aspects of the immuno-inflammatory host response that ultimately results in loss of alveolar bone. A proposal is made that periodontal inflammation not only stimulates osteoclastogenesis but also interferes with the uncoupling of bone formation and bone resorption, consistent with a pathologic process. Furthermore, arguments based on experimental animal models suggest a critical role of the spatial and temporal aspects of inflammation in the periodontium. A review of these findings leads to a new paradigm to help explain more fully the impact of inflammation on alveolar bone in periodontal disease so that it includes the effects of inflammation on uncoupling of bone formation from resorption.

Regulatory T cells in mouse periapical lesions

INTRODUCTION

T-regulatory (Treg, CD4+ FOXP3+) cells constitute a unique subpopulation of CD4+ T cells that inhibit T-cell responses and prevent disease development/exacerbation in models of autoimmunity. In the present study, we tested the hypothesis that Treg cells are induced in periapical lesions by dental pulp infection.

METHODS

In situ hybridization (ISH) was used to localize FOXP3+ cells on day 21 after pulp exposure of the first molar teeth and infection with bacteria from the oral environment. FOXP3/GFP knock-in transgenic mice were used to quantify FOXP3+ Treg cells that infiltrate into periapical lesions by flow cytometry on days 7, 14, and 21 after infection. Periodontal ligament from uninfected teeth served as a negative control.

RESULTS

ISH showed strong signals that showed the presence of FOXP3+ cells mainly at the periphery of periapical lesions. In contrast, no positive cells were present in the periodontal ligament of uninfected controls. Flow cytometry showed an increase in the number of FOXP3+ Treg beginning between day 7 and day 14 (0.69% of the infiltrate) after infection and increased to day 21 (0.94%) (p < 0.05 and p < 0.001, respectively, vs uninfected controls). Treg were also increased in number in draining cervical lymph nodes after pulpal infection.

CONCLUSIONS

These results show that Treg cells are induced to infiltrate into periapical lesions by pulpal infection and suggest that they increase in a time-dependent manner.

Effects of TGF-β1 on interleukin profile of human dental pulp and odontoblasts

Transforming growth factor-beta 1 (TGF-beta1) is the most extensively studied growth factor in dentin-pulp complex, with pleiotropic effects on pulp response and healing. Our main objective was to analyze the expression profile of pulp tissue and odontoblasts, and the effects of TGF-beta1 on these profiles in cultured human pulp and odontoblasts with a specific interest in the anti- and pro-inflammatory cytokines. For that purpose, pulps and odontoblasts were cultured for different time periods, and microarray was performed to both cultured and native samples. Of cytokines, various interleukins (IL) were confirmed by RT-PCR, and in +/- TGF-beta1 treated pulps also by antibody array. Pro-inflammatory IL-7, -12alpha and -16 mRNAs were detected in native pulp. The expression levels of pro-inflammatory IL-1alpha, -1beta, -6 and -8 were clearly induced after TGF-beta1 treatment, while no anti-inflammatory cytokines were induced. Of all pulpal interleukins analyzed IL-6 and -8 were present at the highest levels in conditioned pulp tissue media. In native odontoblasts pro-inflammatory IL-6 and -7 mRNAs were detected, and in cultured odontoblasts pro-inflammatory IL-8 mRNA showed over 20-fold transient induction after TGF-beta1 treatment. Our results demonstrate that TGF-beta1 is a potent regulator of pro-inflammatory responses and defensive reactions in dentin-pulp complex.

Collagenase-3 (MMP-13) is expressed in periapical lesions: an immunohistochemical study

AIM

To determine whether or not matrix metalloproteinase 13 (MMP-13) is present in periapical granulomas with and without epithelium.

METHODOLOGY

Seventeen open periapical granulomas of pulpal origin (seven lesions without epithelium and 10 with proliferating epithelium) were fixed in formalin and then embedded in paraffin prior to being processed for immunohistochemical analysis. A monoclonal antibody against human MMP-13 was used to evaluate MMP-13 expression. Immunocomplexes were subsequently treated with the secondary antibody and then detected by means of streptavidin peroxidase. Immunoreactivity was visualized by development with 3,3'-diaminobenzidine.

RESULTS

An immunopositive cytoplasmatic reaction for MMP-13 was observed in all the specimens, although the immunostaining by anti-MMP-13 antibody was heterogeneous and its levels varied according to histopathological findings. In periapical lesions without epithelium MMP-13 immunolabelling was detected in a few fibroblast-like cells, and in some plasma cells within the granulomatous tissue. A clear upregulation of MMP-13 expression was detected in periapical lesions with epithelium, especially in small island and thin strands of epithelium.

CONCLUSIONS

The expression pattern of MMP-13 demonstrates that it is involved in the conversion of a periapical granuloma with epithelium into a radicular cyst. This property is related to the ability of MMP-13 to influence not only the migration of epithelial cell but also the invasion of granulomatous tissue.

High IL-6 synthesis in cultured fibroblasts isolated from radicular cysts

OBJECTIVE

Inflammatory cytokines have been reported to be related with inflammation and expansion of jaw cysts. In this study, to examine the relationship between radicular cysts and inflammatory cytokines, it was found that there was notable unique evidence on cytokine synthesis from fibroblasts isolated from radicular cysts.

METHODS

The expression of such cytokines, namely, interleukin-1beta, IL-1beta, IL-6, IL-8, IL-10, tumour necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), transforming growth factor-beta1 (TGF-beta1), and granulocyte-macrophage colony-stimulating (GM-CSF) mRNA, in nine radicular cysts was examined and compared with that detected in six specimens of healthy gingival mucosa. Furthermore, separating all fibroblasts from their respective radicular cysts, healthy gingival mucosa, and healthy periodontal ligaments, these fibroblast groups were cultured without stimulators and a supernatant for each was obtained to analyse IL-1beta, IL-6, IL-8, TNF-alpha, and IFN-gamma by ELISA.

RESULTS

Differences between radicular cysts and healthy gingival mucosa were not clearly shown by the expression of cytokine mRNA. Analysing inflammatory cytokine synthesis in fibroblast groups from these three kinds of tissues, surprisingly, the levels of IL-6 mRNA and protein were recognised to be higher in fibroblasts of radicular cysts than in those of control tissues by ELISA and a real-time RT-PCR. Significant differences in the cultured supernatants of these fibroblast groups were not recognised in the release of IL-1beta, IL-8, TNF-alpha, and IFN-gamma by ELISA.

CONCLUSIONS

From these results, it was suggested that fibroblasts inducing IL-6 production might play important roles in the expansion of radicular cysts. It is considered that fibroblasts around radicular cysts may lead to high IL-6 synthesis over time in chronic inflammation.