Kinetics of Th17-related cytokine expression in experimentally induced rat periapical lesions

Interleukin 17 expression in periapical lesions from elderly patients

OBJECTIVE

To compare the expression of IL-17 in periapical lesions (cysts and granulomas) among elderly individuals and adults. We selected 20 periapical lesions of the elderly (12 granulomas and eight cysts) and 20 periapical lesions of adults (12 granulomas and eight cysts).

MATERIALS AND METHODS

Immunohistochemistry was performed using a specific antibody for IL-17. The slides were subdivided into five high magnification fields and then the images were observed through an optical microscope. According to the number of positive markings for the antibody, grades were given, ranging from 0 to 2.

RESULTS

The results demonstrate that there was no statistical difference when comparing the expression of IL-17 between cysts and granulomas of both groups (study group: cysts 0.7 ± 0.21 × granulomas 0.96 ± 0.58, p = .61; control group: cysts 0.37 ± 0.16 × granulomas 0.31 ± 0.23, p = .27). The comparison between adult (control group) and elderly patients (study group) showed a statistical difference both in cysts (study group: 0.7 ± 0.21 × control group: 0.37 ± 0.16, p = .007) and in granulomas (study group: 0.96 ± 0.58 × control group: 0.31 ± 0.23, p = .0009), in which elderly patients had a higher expression of interleukin 17, in relation to adult patients.

CONCLUSION

We concluded that elderly patients have a higher expression of IL-17 in both cysts and granulomas, when compared to adult patients.

Mines of cytokine: A treasure trove in pulpal and periapical diseases

Pulpitis is a special disease of dental pulp. It causes localized inflammation, due to various inflammatory mediators such as cytokines and chemokines. These inflammatory mediators are responsible for various reparative and resorptive processes in the dental pulp. The balance between these processes ultimately determines the viability of the tooth. Due to the important properties of various inflammatory markers, the correlation of cytokinin gene expression in various stages of inflammation becomes necessary to focus on. Several studies in the past have focused on the importance of such correlation to help in diagnostic applications. The nature of these inflammatory mediators can help us in diagnostic evaluation. Several attempts have been made to focus on these associations so that it can assist in making clinical decisions effectively. The data available are vast but are the most neglected topic. This review article briefly outlines and summarizes the importance of various inflammatory mediators such as cytokinin and chemokines in various pathways of pulpal and periapical inflammation in explanatory and diagrammatic forms. Knowledge gained about pulpal inflammatory response may aid in understanding the molecular level of inflammatory pulpal and periapical diseases, which shall modify our future diagnostic modalities. Several medicaments are used in the treatment of minimal to advanced dental caries which leads to periapical infections. Thorough understanding of these medicaments can resolve secondary infection and can improve the prognosis of the treated tooth.

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.

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.

Role and mechanism of the nod-like receptor family pyrin domain-containing 3 inflammasome in oral disease

OBJECTIVE

To summarize evidence and data from experimental studies regarding the role and mechanism of the Nod-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome in the pathogenesis of several representative oral diseases.

MATERIALS AND METHODS

A literature search of PubMed and EBSCO was performed. The literature was searched using a combination of keywords, e.g., NLRP3 inflammasome, inflammation, microorganisms, oral inflammatory diseases, and oral immunological diseases.

RESULTS

The initiation and activation of the NLRP3 inflammasome are associated with the pathogenesis and progression of several representative oral diseases, including periodontitis, oral lichen planus, dental pulp disease, and oral cavity squamous cell carcinoma.

CONCLUSIONS

The NLRP3 inflammasome plays a crucial role in the progression of inflammatory and adaptive immune responses. The possible role of the NLRP3 inflammasome in several oral diseases, including not only periodontitis and pulpitis but also mucosal diseases and oral cavity squamous cell carcinoma, may involve the aberrant regulation of inflammatory and immune responses. Understanding the cellular and molecular biology of the NLRP3 inflammasome is necessary because the NLRP3 inflammasome may be a potential therapeutic target for the treatment and prevention of oral inflammatory and immunological diseases.

Ovariectomy Exacerbates Apical Periodontitis in Rats with an Increase in Expression of Proinflammatory Cytokines and Matrix Metalloproteinases

INTRODUCTION

The aim of this study was to evaluate the gene expression of proinflammatory cytokines, matrix metalloproteinases (MMPs), and cathepsin K in apical periodontitis (AP) and the volume of lesions in ovariectomized and sham-operated rats.

METHODS

Twenty 12-week-old female Wistar rats were subjected to ovariectomy (OVX) or sham surgery. After 9 weeks, access cavities were prepared in the maxillary and mandibular first molars, pulp tissue was removed, and canals were exposed to the oral environment during 21 days for the induction of AP. The groups were as follows: sham, OVX, sham+AP, and OVX+AP. Animals were euthanized, and blocks containing the maxillary first molar and the surrounding bone were removed for quantification of proinflammatory cytokines cathepsin K and MMP genes by real-time polymerase chain reaction. The hemimandibles containing the mandibular first molars were used for analysis of the AP lesion volume by micro-computed tomographic imaging.

RESULTS

AP in OVX rats showed an increased expression of interleukin 1 beta, tumor necrosis factor alpha, interleukin 6, MMP-8, and MMP-13 (P < .05). OVX alone, without AP induction, did not affect the expression of the evaluated genes. Additionally, AP induced an increase in cathepsin K expression, without significant differences between AP in the sham and OVX groups (P > .05). Micro-computed tomographic imaging showed a significantly greater AP lesion mean volume in OVX compared with sham animals (P < .05).

CONCLUSIONS

AP lesions in ovariectomized rats are larger and have an increased expression of proinflammatory cytokines and MMPs, indicating that the infection combined with ovariectomy has an important role in the regulation of these signaling molecules and enzymes during the development of AP. Based on that, it may be assumed that the hypoestrogenic condition aggravates inflammation and degradation of extracellular matrix components in AP, which may provide insight into understanding the development of AP in female postmenopausal patients.

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.