Periapical inflammatory responses and their modulation

The effect of single-file reciprocating systems on Substance P and Calcitonin gene-related peptide expression in human periodontal ligament

AIM

To quantify the effect of two single-file reciprocating root canal preparation systems on Substance P (SP) and Calcitonin gene-related peptide (CGRP) expression in healthy human periodontal ligament (PDL).

METHODOLOGY

Forty PDL samples were obtained from healthy premolars where extraction was indicated for orthodontic reasons. Prior to extraction, 20 of these premolars were divided equally in two groups, and then, root canals were prepared using one of two different single-file systems: WaveOne and Reciproc. Ten premolars were prepared with hand files and served as a positive control group. The remaining 10 premolars where extracted without treatment and served as a negative control group. All PDL samples were processed, and SP and CGRP were measured by radioimmunoassay.

RESULTS

Greater SP and CGRP expression were found in the hand instrumentation group (1.220 pmol SP and 0.084 pmol CGRP per mg of PDL), followed by the WaveOne group (0.908 pmol SP and 0.046 pmol CGRP per mg of PDL) and the Reciproc group (0.511 pmol SP and 0.022 pmol CGRP per mg of PDL). The lower SP and CGRP values were associated with the intact control group (0.453 pmol SP and 0.018 pmol CGRP per mg of PDL). The Kruskal-Wallis test revealed significant differences between groups (P < 0.001). Post hoc Tukey HSD tests revealed significant differences in SP and CGRP expression between intact teeth in the control group and all the other groups (P < 0.001) except with the Reciproc group (P = 0.165 and P = 0.42 for SP and CGRP, respectively). Hand instrumentation was associated with significant differences with all the other groups (P < 0.001). Differences between the WaveOne and Reciproc groups were also significant (P < 0.001).

CONCLUSION

Substance P and CGRP expression in PDL cells increased when teeth were prepared with WaveOne as well as with hand instrumentation. Reciproc maintained SP and CGRP levels in line with the negative control group.

LPS induces IL-8 expression through TLR4, MyD88, NF-kappaB and MAPK pathways in human dental pulp stem cells

AIM

To evaluate the effects of lipopolysaccharide (LPS) on interleukin-8 (IL-8) and related intracellular signalling pathways in human dental pulp stem cells (hDPSCs).

METHODOLOGY

Human pulp tissues were isolated from human impacted third molars, and the hDPSCs were cultured and characterized. The effects of LPS on IL-8 and Toll-like receptor 4 (TLR4) gene expression in hDPSCs were investigated using real-time quantitative RT-PCR and ELISA. Whether TLR4/MyD88/NF-кB was involved in the LPS-induced up-regulation of IL-8 in hDPSCs was determined using transient transfection, luciferase assay and ELISA. The involvement of MAPKs in the LPS-induced up-regulation of IL-8 in hDPSCs was investigated via transient transfection, luciferase assay, ELISA and western blot. The data were statistically analysed using Student's t-test or one-way anova followed by the Student-Neumann-Keuls test.

RESULTS

Cells exposed to LPS not only displayed an enhanced expression of TLR4 but also showed an elevated IL-8 gene expression; exposure to LPS also resulted in the induction of IL-8 gene transcription via promoter activation. The LPS-induced IL-8 promoter activation was inhibited through dominant-negative mutations in TLR4 and MyD88, but not in TLR2. The LPS-induced IL-8 protein release was attenuated through the administration of TLR4-neutralizing antibody or MyD88 inhibitory peptide and a dominant-negative mutation in IκBα. In contrast, IL-8 protein release was enhanced through the expression of NF-κB p65. Treatment with PDTC, TPCK or Bay117082 effectively antagonized LPS-induced IL-8 protein release. Moreover, both the promoter activity and the LPS-induced release of IL-8 were diminished upon the administration of U0126 and SB203580, but not SP600125. Moreover, the exposure to LPS activated ERK1/2 and p38 MAPK phosphorylation in cells.

CONCLUSIONS

This study reports the LPS-mediated transcriptional and post-translational up-regulation of IL-8, which is a process that also involves TLR4, MyD88, NF-κB and MAPK.

Pro-inflammatory cytokines induce odontogenic differentiation of dental pulp-derived stem cells

Postnatal dental pulp stem cells (DPSCs) represent a unique precursor population in the dental pulp, which have multipotential and harbor great potential for tissue engineering purposes. However, for therapy applications, transplanted cells are often exposed to unfavorable conditions such as cytokines released from necrotic or inflammatory cells in injured tissues. It is not clear how stem cells exposed to these conditions changes in their characteristics. In this study, the effects of pro-inflammatory cytokines, such as IL-1 and TNF, on DPSCs were investigated. Cells were treated with IL-1, TNF, or both for 3, 7, and 12 days. The cultures were evaluated for cell proliferation, ALP activity, and real-time PCR. We found that a short treatment (3 days) of pro-inflammatory cytokines induced the odontogenic differentiation of DPSCs. Furthermore, post 3 days treatment with pro-inflammatory cytokines, the cell-scaffold complexes were implanted subcutaneously in mice for 8 weeks. Histological analysis demonstrated that the cultures gave obviously mineralized tissue formation, especially for both IL-1 and TNF applied. These data suggest that IL-1 and TNF produced in the early inflammatory reaction may induce the mineralization of DPSCs.

Protective effect of metformin on periapical lesions in rats by decreasing the ratio of receptor activator of nuclear factor kappa B ligand/osteoprotegerin

INTRODUCTION

Metformin, one of the antihyperglycemic agents commonly used for the treatment of type 2 diabetes, was shown to inhibit osteoclast formation. The current study aimed to investigate the effects of systemically administered metformin on alveolar bone resorption and on the ratio of receptor activator of nuclear factor kappa B ligand/osteoprotegerin (RANKL/OPG) in rats subjected to experimental periapical lesions.

METHODS

Forty adult male Wistar rats were divided equally into control and experimental groups, and the pulp chambers of their mandibular first molars were exposed to the oral environment to induce periapical lesions. The experimental group received daily intramuscular injections of metformin at 40 mg/kg doses, whereas the control group received only the saline vehicle. The injections were initiated 1 day before the periapical lesion induction and then were continued daily throughout the entire experimental period. Two or 4 weeks after pulp exposure, the rats were killed, and the mandibles were prepared for histologic analysis, enzyme histochemistry, immunohistochemistry, and immunofluorescence.

RESULTS

The number of RANKL-positive and tartrate-resistant acid phosphatase (TRAP)-positive cells in the metformin-treated groups decreased on day 14, whereas the number of OPG-positive cells increased on day 28. The periapical bone loss area in the metformin-treated group significantly decreased on day 28 compared with the control group.

CONCLUSIONS

Metformin inhibits the periapical lesions possibly by lowering the RANKL/OPG ratio, subsequently reducing the number of osteoclasts and bone resorption areas.

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.

Comparative analysis of carrier-based obturation and lateral compaction: a retrospective clinical outcomes study

The purpose of this retrospective study was to compare the outcome of primary endodontic treatment using a standardized cleaning and shaping technique and obturation with either lateral compaction or carrier-based obturation. Patients received primary endodontic treatment in the predoctoral dental clinic using a standardized cleaning and shaping protocol. All root canals were obturated using AH Plus^TM sealer with lateral compaction of gutta-percha (LC) or carrier-based obturation (CBO). A total of 205 cases met the inclusion criteria. 71 teeth in 60 patients were recalled after 2 years and evaluated both clinically and radiographically by two independent examiners. Success was defined as a lack of clinical symptoms and a normal periodontal ligament space or reduction in size of a previously existing periapical radiolucency. Chi-square and logistic regression were used for statistical analysis with a significance level of P < 0.05. There was no difference in success rates between cases obturated with LC or CBO (P = 0.802); overall success rate was 83%. Molars had a significantly lower success rate (53%) than premolar and anterior teeth (89%) (P = 0.005), irrespective of the obturation technique used. When a standardized cleaning and shaping protocol was used by predoctoral dental students in a controlled university setting, there was no difference in success rates between cases obturated with LC or CBO.

Bacteria-reactive immune response may induce RANKL-expressing T cells in the mouse periapical bone loss lesion

INTRODUCTION

The present study investigated whether bacteria infecting the root canal can activate any infiltrating T cells to produce receptor activator of nuclear factor kappa B (NF-κB) ligand (RANKL).

METHODS

Using a mouse model of periapical lesion induced by artificial dental pulp exposure, the presence of RANKL-positive T cells and osteoclasts in the periapical lesion was examined by an immunohistochemical approach. The bacteria colonizing the exposed root canal were identified by 16S ribosomal RNA (rRNA) sequence analysis. The isolated endodontic bacteria were further immunized to normal mice, and soluble activator of NF-κB ligand (sRANKL) production by the T cells isolated from the immunized mice was evaluated by ex vivo culture system.

RESULTS

RANKL-positive T cells along with TRAP+ osteoclasts were identified in periapical bone resorption lesions. The gram-negative bacterium Pasteurella pnumotropica, which was most frequently detected from the root canal of exposed pulp, showed remarkably elevated serum immunoglobulin G (IgG)-antibody response in pulp-exposed mice compared with control nontreated mice. Immunization of mice with P. pneumotropica induced not only serum IgG-antibody but also primed bacteria-reactive T cells that produced sRANKL in response to ex vivo exposure to P. pneumotropica.

CONCLUSIONS

T cells infiltrating the periapical region express RANKL, and the endodontic bacteria colonizing the root canal appear to induce RANKL expression from bacteria-reactive T cells, suggesting the possible pathogenic engagement of the immune response to endodontic bacteria in the context of developing bone resorptive periapical lesions.

A comparison of the cytotoxicity and proinflammatory cytokine production of EndoSequence root repair material and ProRoot mineral trioxide aggregate in human osteoblast cell culture using reverse-transcriptase polymerase chain reaction

INTRODUCTION

The purpose of this study was to compare the cytotoxicity and cytokine expression profiles of EndoSequence Root Repair Material (ERRM; Brasseler, Savannah, GA) putty, ERRM flowable, and ProRoot mineral trioxide aggregate (MTA; Dentsply Tulsa Dental, Johnson City, TN) using osteoblast cells (MG-63).

METHODS

Four millimeters in diameter of each material was placed in the center of a 6-well culture plate, and a 2-mL suspension (10(5) cells/mL) of human osteoblasts was seeded in each well. Photomicrograph images were used to evaluate cytotoxicity as evidenced by the lack of osteoblast cell growth in relation to the materials with AH-26 (Dentsply Tulsa Dental) as the positive control. In addition, reverse-transcriptase polymerase chain reaction (RT-PCR) was used to evaluate the expression of interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor-α (TNF-α). Cytokine expression of MG-63 cells upon lipopolysaccharide treatment was used as controls. RT-PCR results were normalized by the expression of the housekeeping gene β-actin and were used to measure cytokine expression. Statistical analysis was performed using analysis of variance.

RESULTS

Results showed that ERRM putty and MTA exhibited minimal levels of cytotoxicity; however, ERRM was slightly more cytotoxic although not statistically significant. The expression of IL-1β, IL-6, and IL-8 was detected in all samples with minimal TNF-α expression.

CONCLUSIONS

We concluded that ERRM and MTA showed similar cytotoxicity and cytokine expressions.

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.

Cells isolated from inflamed periapical tissue express mesenchymal stem cell markers and are highly osteogenic

INTRODUCTION

We previously reported the presence of mesenchymal stem/progenitor cells (MSCs) in inflamed pulp tissue. Here we asked whether MSCs also exist in inflamed periapical tissues resulting from endodontic infection. The objectives of this study were to detect the expression of MSC markers in periapical inflammatory tissues and to characterize isolated cells from these tissues.

METHODS

Human periapical inflammatory tissues were collected and processed to detect MSC marker expression by immunohistochemistry. Cells were isolated and tested for cell surface marker expression by using flow cytometry and examined for multiple differentiation potential into osteogenic and adipogenic pathways. In vivo formation of mineralized tissues was assessed in a mouse model.

RESULTS

Immunohistochemistry showed positive staining for MSC markers STRO-1, CD90, and CD146. Isolated cells at passage 0 appeared as typical fibroblastic cells, and a few cells formed colony-forming unit-fibroblasts (CFU-Fs). After passaging, the CFU-F forming ability diminished dramatically, and the population doubling was up to 26. Flow cytometry data showed that these cells at passage 2 expressed low levels of STRO-1 and CD146 and moderate to high levels of CD90, CD73, and CD105. At passage 6, the levels of these markers decreased. When incubated in specific differentiation medium, cells demonstrated a strong osteogenic but weak adipogenic capacity. After in vivo cell transplantation, mineralized tissues formed in immunocompromised mice.

CONCLUSIONS

Human periapical inflammatory tissues expressed MSC markers, suggesting the presence of MSCs. Isolated cells exhibited typical mesenchymal cell immunophenotype with a capacity to form mineralized matrix in vitro and in vivo.

Retracted: Effects of pro-inflammatory cytokines on mineralization potential of rat dental pulp stem cells

The following article from the Journal of Tissue Engineering and Regenerative Medicine, 'Effects of Pro-inflammatory Cytokines on Mineralization Potential of Rat Dental Pulp Stem Cells' by Yang X, Walboomers XF, Bian Z, Jansen JA, Fan M, published online on 11 July 2011 in Wiley Online Library (onlinelibrary.wiley.com), has been retracted by agreement between the authors, the journal Editor-in-Chief, and John Wiley & Sons, Ltd. The retraction has been agreed due to two authors (Walboomers XF, and Jansen JA) not having been involved in the research described, nor made aware of their names being listed on the manuscript, nor told of its submission to the journal.

A controversial role for IL-12 in immune response and bone resorption at apical periodontal sites

Periapical lesions are inflammatory conditions of tooth periapical tissues, triggered by dental pulp infection and characterized by exudation of immune cells to the affected tissues and production of inflammatory mediators such as cytokines. The inflammatory periapical reaction is mainly driven by Th1, Th2, and Th17 responses, and such polarization may modulate progression of the disease and expression of bone proresorptive cytokines. IL-12 is a potent inducer of IFN-γ production, which stimulates Th1 effector cells. Many evidences have shown a positive correlation between the bone resorptive cytokine IL-1β and the production of IL-12 and IFN-γ. Furthermore, IL-12 may have a potential role in the release of bone resorptive mediators and blockade of Th2 cytokines, affecting the progression of periapical bone loss. Nevertheless, IL-12 and IFN-γ have also been described as suppressors of osteoclast differentiation and activation, favoring bone maintenance. This paper focuses on the controversial roles of IL-12 in periapical lesions.

Antigen recognition and presentation in periapical tissues: a role for TLR expressing cells?

Bacteria are the prime cause of periapical diseases and root canal microbiology is a well-researched area of endodontics. Antigen-presenting cells (APCs) are present in periapical lesions of endodontic origin and play a substantial role in recognizing, processing and presenting pathogenic antigens to the adaptive immune system such as an effective and long-lasting immune response is generated against the specific pathogens. Toll-like receptors (TLRs) are germ-line encoded pathogen recognition receptors (PRR) expressed by various APCs which induce their maturation, lead to gene transcription in the nucleus and the production of several pro- and anti-inflammatory cytokines. Thirteen TLRs have been discovered, 10 of which have been identified in humans so far. Preliminary studies of dental pulp tissue have demonstrated various cell types expressing different TLRs in response to commonly encountered microorganisms. However, there is little information available regarding the expression and function of the various TLRs in human periapical lesions. This review discusses the interactions of various APCs in periapical lesions and the possible roles of different TLRs and APCs in pulp/periapical pathogen recognition and presentation to the adaptive immune system in the initiation and sustaining of periapical diseases.

Effect of alendronate on alveolar bone resorption and angiogenesis in rats with experimental periapical lesions

AIM

To investigate the effects of systemically administered alendronate, one of the most potent bisphosphonates (BPs), on alveolar bone resorption and angiogenesis in rats subjected to experimental periapical lesions over two time periods.

METHODOLOGY

Forty adult Sprague-Dawley (SD) rats were divided equally into control and experimental groups, and the pulp chambers of mandibular first molars of all rats were exposed to the oral environment to induce periapical lesions. The experimental group received daily subcutaneous injections of alendronate at a dose of 0.25 mg kg(-1), whereas the control group received only the saline vehicle. These injections were initiated 1 week before the periapical lesion induction and then continued daily throughout the entire experimental period. After 2 or 4 weeks following pulp exposure, the rats were killed, and the mandibles were examined histologically for periapical bone loss area, number of microvascular vessels (NMV) and tartrate-resistant acid phosphatase (TRAP) activity.

RESULTS

Overall, periapical bone loss area and the number of TRAP-positive cells (osteoclasts) were significantly decreased at 2 and 4 weeks, respectively, after daily subcutaneous injection of alendronate compared with the control group (P < 0.05). There was no significant decrease change in NMV (P > 0.05).

CONCLUSIONS

Administration of alendronate to rats might inhibit alveolar bone resorption associated with periapical disease, which might not lead to impairment of angiogenesis. However, because of the differences between rats and humans, one has to consider the possible consequences of this treatment in the clinic.

The effect of three different rotary instrumentation systems on substance P and calcitonin gene-related peptide expression in human periodontal ligament

INTRODUCTION

The purpose of this study was to quantify the effect of three different rotary root canal preparation systems on substance P and calcitonin gene-related peptide expression in healthy human periodontal ligament.

METHODS

Fifty periodontal ligament samples were obtained from healthy premolars in which extraction was indicated for orthodontic reasons. Before extraction, 40 of these premolars were equally divided into four groups, and root canals were prepared using four different systems: the ProTaper Universal rotary system, the RaCe rotary system, the Mtwo rotary system, and the hand instrumentation technique. The remaining 10 healthy premolars that were extracted without treatment served as a negative control group. All periodontal ligament samples were processed, and SP and CGRP were measured by radioimmunoassay.

RESULTS

Greater SP and CGRP expression were found in the ProTaper Universal group followed by the hand instrumentation group, the RaCe, and the Mtwo groups. The lower SP and CGRP values were for the negative control group. The Kruskal-Wallis test showed statistically significant differences between groups (p < 0.0001). Post hoc Least Significant Difference (LSD) tests showed statistically significant differences in SP and CGRP expression between the negative control group and all the other groups except the Mtwo group. Hand instrumentation also showed statistically significant differences with all the other groups, except the ProTaper Universal group. Differences between the three rotary systems were also statistically significant.

CONCLUSION

SP and CGRP expression in periodontal ligament increases when teeth are prepared with ProTaper Universal and RaCe rotary instrumentation systems as well as with hand instrumentation. Mtwo maintains SP and CGRP levels.

Effects of gender on serum biomarkers of systemic inflammation coincident to experimentally-induced periapical lesions

OBJECTIVE

The literature suggests that females have less adverse effects to infection than males, due to the protective effects of oestrogen. The purpose of our study is to compare the systemic effects of induced periapical lesions between groups of animals with various serum concentrations of oestrogen.

METHODS

To induce periapical inflammation, two molar tooth pulps were exposed in ovariectomized (OVX) and normal female (F) and castrated (Cast-M) and normal male (M) Sprague-Dawley rats (Experimental group, E). Sham-operated control animals from each group were also studied (Control group, C). Twenty-eight days later, serum and maxillas were collected. Serum 17β-oestradiol, testosterone, MMP-9, IL-18, IL-6, TNF-α, and IL-1β concentrations were measured by ELISA. Maxillas were cleaned of residual tissue and digital radiographs were made to verify the presence of periapical lesions. Data were compared by factorial ANOVA, post hoc Tukey, and Pearson correlation tests. Groups were considered to be significantly different when p<0.05.

RESULTS

The serum concentration of IL-18, TNF-α, IL-1-β, IL-6 and MMP-9 was greatest in OVX-E animals, compared to all other groups (p<0.001). F-E rats had significantly higher serum concentrations of these cytokines, compared to F-C. The fold difference in serum concentration of the biomarkers (between E and C groups) was significantly greater in females than males, even though males had higher baseline concentrations of all these biomarkers.

CONCLUSION

When females are oestrogen-deficient, their systemic response to periapical lesions is significantly greater than males, suggesting that oestrogen is essential in protecting females from the effects of this type of inflammation.

Advanced techniques for detecting lesions in bone

Imaging is an important clinical aid for the diagnosis of endodontic bone lesions. Traditional radiology performs more accurately than any other diagnostic tool. Computed tomography has been used for the last 20 years with important implications in the management of lesions in bone. Among the newest systems, digital volume tomography is becoming a new standard and real-time echotomography is gaining an interesting space in the diagnostic field of endodontics. These techniques offer some advantages for the increased safety and the amount of detailed information they can provide.

Protective role of osteopontin in endodontic infection

Endodontic infections are polymicrobial infections resulting in bone destruction and tooth loss. The host response to these infections is complex, including both innate and adaptive mechanisms. Osteopontin (OPN), a secreted, integrin-binding protein, functions in the regulation of immune responses and enhancement of leucocyte migration. We have assessed the role of OPN in the host response to endodontic infection using a well-characterized mouse model. Periapical bone loss associated with endodontic infection was significantly more severe in OPN-deficient mice compared with wild-type 3 weeks after infection, and was associated with increased areas of inflammation. Expression of cytokines associated with bone loss, interleukin-1alpha (IL-1alpha) and RANKL, was increased 3 days after infection. There was little effect of OPN deficiency on the adaptive immune response to these infections, as there was no effect of genotype on the ratio of bacteria-specific immunoglobulin G1 and G2a in the serum of infected mice. Furthermore, there was no difference in the expression of cytokines associated with T helper type 1/type2 balance: IL-12, IL-10 and interferon-gamma. In infected tissues, neutrophil infiltration into the lesion area was slightly increased in OPN-deficient animals 3 days after infection: this was confirmed by a significant increase in expression of neutrophil elastase in OPN-deficient samples at this time-point. We conclude that OPN has a protective effect on polymicrobial infection, at least partially because of alterations in phagocyte recruitment and/or persistence at the sites of infection, and that this molecule has a potential therapeutic role in polymicrobial infections.

Herpesviruses in abscesses and cellulitis of endodontic origin

Acute apical abscesses and cellulitis are severe endodontic diseases caused by opportunistic bacteria with possible coinfection with latent herpesviruses. The objectives of this study are to identify herpesviruses, including human cytomegalovirus (HCMV), Epstein-Barr virus (EBV), herpes simplex virus-1 (HSV-1), and Varicella zoster virus (VZV) in patients (n = 31) presenting with acute apical abscesses and cellulitis of endodontic origin. Primary and nested polymerase chain reaction (PCR) was conducted using virus-specific primers and DNA isolated from cell-free abscess fluid. From patients exhibiting concurrent spontaneous pain (n = 28), nine abscesses contained HCMV, two abscesses contained EBV, one abscess contained HSV-1, and no abscesses contained VZV. Control PCR using genomic or recombinant templates showed detection limits to a single genomic copy of HCMV, 100 genomic copies for EBV, and 1 to 10 copies for HSV-1 with no cross-amplification between herpesviral DNA targets. Nested PCR was required for detection of herpesviral DNA in the abscess specimens, indicating that these viruses were present in low copy number. Filtration of abscess specimens and virus transfer experiments using human fibroblastic MRC-5 cells confirmed the presence of HCMV particles in several abscess specimens. We conclude that herpesviruses are present but not required for the development of acute apical abscesses and cellulitis of endodontic origin.

Relationship between human cytomegalovirus transcription and symptomatic apical periodontitis in Iran

BACKGROUND/AIMS

Apical periodontitis of endodontic origin may develop as a result of cooperative interactions among herpesviruses, specific pathogenic bacteria and tissue-destructive inflammatory mediators. This study sought to identify the presence of Epstein-Barr virus (EBV) and human cytomegalovirus (HCMV) transcripts in symptomatic and asymptomatic periapical lesions of individuals living in Iran.

MATERIAL AND METHODS

Fifty endodontic patients (28 with symptomatic periapical lesions and 22 with asymptomatic periapical lesions) were included in the study. In each study subject, a microbiological periapical sample was collected using a curette in conjunction with periapical surgery. A reverse transcription-polymerase chain reaction assay was used to identify transcripts of EBV and HCMV.

RESULTS

Human cytomegalovirus transcript was detected in 15 of the 28 (53.6%) symptomatic and in six of the 22 (27.3%) asymptomatic periapical study lesions (significant difference between symptomatic and asymptomatic lesions; P = 0.03, chi-square test). Epstein-Barr virus transcript was identified in one symptomatic and in two asymptomatic periapical lesions.

CONCLUSION

This study establishes that HCMV transcription is common in apical periodontitis and is most frequent in symptomatic lesions. The high frequency of active herpesvirus infections in severe apical periodontitis changes the pathogenic paradigm of the disease and may also have preventive and therapeutic implications.

The influence of mineral trioxide aggregate on adaptive immune responses to endodontic pathogens in mice

This study assessed the influence of mineral trioxide aggregate (MTA) on adaptive immune responses. BALB/c mice were immunized with heat-killed Fusobacterium nucleatum (Fn) in MTA or other control adjuvants, and serum IgG responses to Fn were measured. Either Fn- or Peptostreptococcus anaerobius (Pa)-reactive memory T cells (Tm) were preincubated in vitro with/without MTA and restimulated with Fn or Pa. Tm proliferation and cytokine production were assessed. Compared with control groups, immunoglobulin G-antibody responses were upregulated in mice immunized with Fn in MTA in a similar manner to animals immunized with Fn in Freund's adjuvant or aluminum hydroxide adjuvant. Although MTA did not affect the upregulated expression of interleukin 10, tumor necrosis factor alpha, or RANKL by Tm, it suppressed the proliferation of Pa- or Fn-Tm and inhibited their production of Th1- or Th2-signature cytokines. MTA upregulated the adaptive humoral immune responses but had little or no effect on pro- or anti-inflammatory cytokine production by Tm.