Cytokine induction by Streptococcus mutans and pulpal pathogenesis

An in vitro coculture approach to study the interplay between dental pulp cells and Streptococcus mutans

AIM

To develop a new coculture system that allows exposure of dental pulp cells (DPCs) to Streptococcus mutans and dentine matrix proteins (eDMP) to study cellular interactions in dentine caries.

METHODOLOGY

Dental pulp cells and S. mutans were cocultured with or without eDMP for 72 h. Cell proliferation and viability were assessed by cell counting and MTT assays, while bacterial growth and viability were determined by CFU and LIVE/DEAD staining. Glucose catabolism and lactate excretion were measured photometrically as metabolic indicators. To evaluate the inflammatory response, the release of cytokines and growth factors (IL-6, IL-8, TGF-β1, VEGF) was determined by ELISA. Non-parametric statistical analyses were performed to compare all groups and time points (Mann-Whitney U test or Kruskal-Wallis test; α = .05).

RESULTS

While eDMP and especially S. mutans reduced the number and viability of DPCs (p ≤ .0462), neither DPCs nor eDMP affected the growth and viability of S. mutans during coculture (p > .0546). The growth of S. mutans followed a common curve, but the death phase was not reached within 72 h. S. mutans consumed medium glucose in only 30 h, whereas in the absence of S. mutans, cells were able to catabolize glucose throughout 72 h, resulting in the corresponding amount of l-lactate. No change in medium pH was observed. S. mutans induced IL-6 production in DPCs (p ≤ .0011), whereas eDMP had no discernible effect (p > .7509). No significant changes in IL-8 were observed (p > .198). TGF-β1, available from eDMP supplementation, was reduced by DPCs over time. VEGF, on the other hand, was increased in all groups during coculture.

CONCLUSIONS

The results show that the coculture of DPCs and S. mutans is possible without functional impairment. The bacterially induced stimulation of proinflammatory and regenerative cytokines provides a basis for future investigations and the elucidation of molecular biological relationships in pulp defence against caries.

The Efficacy of Different Antibiotic Compounds in Regenerative Treatment of Immature Necrotic Teeth

Objectives: Endodontic treatment of immature teeth poses a significant challenge, especially in achieving a proper seal using traditional obturation methods. Revascularization presents itself as an alternative approach to this problem, and the application of triple antibiotic paste (TAP) has been suggested as a means to achieve disinfection during the procedure. This study aims to compare the antibacterial properties of three different antibiotic combinations to assess their effectiveness on root canal disinfection. Materials and Methods: Eighty samples were employed to assess the impact of three antibiotic combinations on Enterococcus faecalis, Escherichia coli, Streptococcus mutans, and a combination thereof. The antibiotics included metronidazole, ciprofloxacin, and cefaclor (CCM), the commonly used TAP, and a double antibiotic paste (DAP) composed of metronidazole and ciprofloxacin. Dentin shavings collected using Gates-Glidden drills were placed in microtubes containing a 2ml standard bacterial suspension. Microtube contents were diluted and cultured on BHI agar plates, with colony counts calculated based on dentine shavings' weight in CFU/mg. Kruskal-Wallis and Dunn's post-hoc tests were used for statistical analysis and P<0.05 was considered significant. Results: A significant difference in mean CFU was observed among all bacterial groups (P<0.05). Dunn's post-hoc analysis showed a significant difference only between the control group (methylcellulose) and the other antibiotic groups. There was no significant difference between the other antibiotic groups in two-by-two comparisons. Conclusion: There was no significant difference in the antimicrobial properties of DAP, TAP and CCM. Therefore, DAP and CCM may be used during regenerative treatment.

Increased IL-12p70 and IL-8 Produced by Monocytes in Response to Streptococcus spp. and Actinomyces spp. Causals of Endodontic Primary Infections

We sought to evaluate the effect of endodontic-causative microorganisms of primary infections on mononuclear cells such as CD14+, CD4+, CD8+, CD19+ and Tregs Foxp3+. Facultative anaerobic microorganisms were isolated from radicular conducts and peripheral blood samples, which were taken from patients with primary infections. Cellular cultures were performed with peripheral blood mononuclear cells (PBMC) with and without Actinomyces spp. and Streptococcus spp. during 48, 72, and 96 h of contact in culture (concentration 5 × 105 cells/well) in a round plate bound with 48 wells. Later, PBMC was collected for analysis by flow cytometry, with the monoclonal antibodies αCD14, αCD4, αCD8, αCD19 and αFoxp3, and acquired using an FACSCanto II cytometer. The supernatant of cellular cultures was analyzed for the quantification of inflammatory cytokines. Data analysis was performed in FlowJo v10.8.2 and FCAPArray software, and statistical analysis was performed using GraphPad v5.0. software. We observed an increase in the percentage of CD14+ cells in patients at different hours of cellular culture in the presence of both Actinomyces spp. and Streptococcus spp. microorganisms, compared to healthy controls. This study demonstrates the role played by the innate immune system in the pathogeny of endodontic primary infections, explaining the effects that generate the more common microorganisms in this oral pathology.

Thrombus Aspirates From Patients With Acute Ischemic Stroke Are Infiltrated by Viridans Streptococci

BACKGROUND

Acute ischemic stroke may be due to embolism from ruptured atherosclerotic carotid arteries. DNA of oral bacteria, mainly the viridans streptococci group, has been detected in thrombus aspirates of patients with ischemic stroke as well as in carotid endarterectomy samples. Because viridans streptococci are known to possess thrombogenic properties, we studied whether their presence in thrombus aspirates and in carotid artery specimens can be confirmed using bacterial immunohistochemistry.

METHODS AND RESULTS

Thrombus aspirates from 61 patients with ischemic stroke (70.5% men; mean age, 66.8 years) treated with mechanical thrombectomy, as well as carotid endarterectomy samples from 20 symptomatic patients (65.0% men; mean age, 66.2 years) and 48 carotid artery samples from nonstroke autopsy cases (62.5% men; mean age, 66.4 years), were immunostained with an antibody cocktail against 3 species (Streptococcus sanguinis, Streptococcus mitis, and Streptococcus gordonii) of viridans streptococci. Of the thrombus aspirates, 84.8% were immunopositive for viridans streptococci group bacteria, as were 80.0% of the carotid endarterectomy samples, whereas immunopositivity was observed in 31.3% of the carotid artery samples from nonstroke autopsies. Most streptococci were detected inside neutrophil granulocytes, but there were also remnants of bacterial biofilm as well as free bacterial infiltrates in some samples.

CONCLUSIONS

Oral streptococci were found in aspirated thrombi of patients with acute ischemic stroke as well as in carotid artery samples. Our results suggest that viridans streptococci group bacteria may play a role in the pathophysiology of ischemic stroke.

Antibacterial and Immunomodulatory Properties of Stem Cells from Human Exfoliated Deciduous Teeth: An In Vitro Study

Stem cells from human exfoliated deciduous teeth (SHED) provide an important autologous source for stem cell-based regenerative therapies with their easy acquisition and multipotency. However, the understanding of their antibacterial and immunomodulatory properties is limited. This in vitro research aims to determine whether SHED inhibits the growth of Streptococcus mutans (S. mutans) and Enterococcus faecalis (E. faecalis), as well as whether or not it has immunomodulatory effects by measuring interleukins (ILs)-2 and -6 levels. SHEDs were derived from the pulp of deciduous teeth that had undergone up to two-thirds of their roots' resorption. Isolated SHEDs were characterized on their morphological features, viability, assessment of surface markers, and in vitro induction into osteocytes and adipocytes. SHED was tested for its antibacterial efficacy against S. mutans and E. faecalis using a colony-forming units (CFU) assay. Lastly, we checked the cytokine levels by enzyme-linked immune sorbent assay (ELISA) for assessing the immunomodulatory properties of SHED. The results showed that the established SHED had fibroblastic morphology with higher viability. The ability to differentiate into osteocytes and adipocytes, as well as the expression of stem cell-specific markers, demonstrated their potential and flexibility under in vitro settings. SHED demonstrated antibacterial characteristics by significantly (p < 0.05) lowering S. mutans CFU, whereas E. faecalis CFU was either unaffected by or just slightly affected by the cells. SHED also helped keep inflammatory indicators, including IL-2 and IL-6, at stable levels when compared to the control. The results indicate that SHED may aid in preventing or reducing an infection due to its antibacterial activity and may provide immunomodulatory activities by controlling the production of cytokines.

How to cite this article

Tyagi A, Shetty J, Shetty S, et al. Antibacterial and Immunomodulatory Properties of Stem Cells from Human Exfoliated Deciduous Teeth: An In Vitro Study. Int J Clin Pediatr Dent 2023;16(S-3):S240-S246.

Anti-inflammatory effects of the prostacyclin analogue iloprost in an in vitro model of inflamed human dental pulp cells

Iloprost's anti-inflammatory effects on human dental pulp stem cells (HDPCs) are currently unknown. We hypothesized that iloprost could downregulate the expression of inflammatory-related genes and protein in an inflamed HDPC in vitro model. To induce inflammation, the HDPCs were treated with a cocktail of interleukin-1 beta, interferon-gamma, and tumour necrosis alpha, at a ratio of 1:10:100. Iloprost (10-6  M) was then added or not to the cultures. Interleukin-6 (IL-6) and interleukin-12 (IL-12) mRNA expression were assessed by real-time polymerase chain reaction. IL-6 protein expression was assessed by enzyme-linked immunosorbent assay. The results were analysed using one-way ANOVA or the Kruskal-Wallis test. The cytokine cocktail induced more robust IL-6 expression than LPS treatment. Iloprost slightly, yet significantly, downregulated IL-6 and IL-12 mRNA expression. These findings suggest that iloprost might be used as a beneficial component in vital pulp therapy.

Extracellular matrix remodelling in dental pulp tissue of carious human teeth through the prism of single-cell RNA sequencing

Carious lesions are bacteria-caused destructions of the mineralised dental tissues, marked by the simultaneous activation of immune responses and regenerative events within the soft dental pulp tissue. While major molecular players in tooth decay have been uncovered during the past years, a detailed map of the molecular and cellular landscape of the diseased pulp is still missing. In this study we used single-cell RNA sequencing analysis, supplemented with immunostaining, to generate a comprehensive single-cell atlas of the pulp of carious human teeth. Our data demonstrated modifications in the various cell clusters within the pulp of carious teeth, such as immune cells, mesenchymal stem cells (MSC) and fibroblasts, when compared to the pulp of healthy human teeth. Active immune response in the carious pulp tissue is accompanied by specific changes in the fibroblast and MSC clusters. These changes include the upregulation of genes encoding extracellular matrix (ECM) components, including COL1A1 and Fibronectin (FN1), and the enrichment of the fibroblast cluster with myofibroblasts. The incremental changes in the ECM composition of carious pulp tissues were further confirmed by immunostaining analyses. Assessment of the Fibronectin fibres under mechanical strain conditions showed a significant tension reduction in carious pulp tissues, compared to the healthy ones. The present data demonstrate molecular, cellular and biomechanical alterations in the pulp of human carious teeth, indicative of extensive ECM remodelling, reminiscent of fibrosis observed in other organs. This comprehensive atlas of carious human teeth can facilitate future studies of dental pathologies and enable comparative analyses across diseased organs.

Current State and Challenges of the Global Outcomes of Dental Caries Research in the Meta-Omics Era

Despite significant healthcare advances in the 21st century, the exact etiology of dental caries remains unsolved. The past two decades have witnessed a tremendous growth in our understanding of dental caries amid the advent of revolutionary omics technologies. Accordingly, a consensus has been reached that dental caries is a community-scale metabolic disorder, and its etiology is beyond a single causative organism. This conclusion was based on a variety of microbiome studies following the flow of information along the central dogma of biology from genomic data to the end products of metabolism. These studies were facilitated by the unprecedented growth of the next- generation sequencing tools and omics techniques, such as metagenomics and metatranscriptomics, to estimate the community composition of oral microbiome and its functional potential. Furthermore, the rapidly evolving proteomics and metabolomics platforms, including nuclear magnetic resonance spectroscopy and/or mass spectrometry coupled with chromatography, have enabled precise quantification of the translational outcomes. Although the majority supports 'conserved functional changes' as indicators of dysbiosis, it remains unclear how caries dynamics impact the microbiota functions and vice versa, over the course of disease onset and progression. What compounds the situation is the host-microbiota crosstalk. Genome-wide association studies have been undertaken to elucidate the interaction of host genetic variation with the microbiome. However, these studies are challenged by the complex interaction of host genetics and environmental factors. All these complementary approaches need to be orchestrated to capture the key players in this multifactorial disease. Herein, we critically review the milestones in caries research focusing on the state-of-art singular and integrative omics studies, supplemented with a bibliographic network analysis to address the oral microbiome, the host factors, and their interactions. Additionally, we highlight gaps in the dental literature and shed light on critical future research questions and study designs that could unravel the complexities of dental caries, the most globally widespread disease.

Clinical, radiological, and histological correlation in diagnosis of pulpitis

BACKGROUND

To establish an endodontic diagnosis, a clinician should consider a variety of factors. Various studies have failed to demonstrate a strong correlation between histological findings with clinical and radiographic assessments. This study sought to evaluate the histopathological features of reversible and irreversible pulpitis diseases and their correlation with clinical diagnosis in extracted human molar teeth.

MATERIALS AND METHODS

In this experimental ex vivo study, 75 molars with caries and three intact molars were used. According to the radiographic findings and clinical criteria and the need for root canal therapy, samples were categorized as having normal/reversible pulpitis and irreversible pulpitis. Immediately after extraction, an exposure was made at 2 mm below the cementoenamel junction. Formalin-fixed specimens were decalcified, sectioned and stained with hematoxylin and eosin for histological examinations using light microscopy. Variables including the type and severity of the inflammation, hyperemia, necrosis, fibrosis and the existence of an odontoblastic layer and dentin bridge were evaluated. The Fisher's exact test and the Chi-squared test were used for statistical analysis. P <0.05 was considered as significant.

RESULTS

Acute inflammation, hyperemia and pulp exposure were significantly more common among subjects with irreversible pulpitis (P < 0/005). However, fibrosis was significantly higher in the reversible group (P < 0/005). There were no statistically significant differences between the groups regarding the other variables.

CONCLUSION

Some discrepancies between clinical, radiographic and histological findings were observed in our experimental study. Indeed, effective clinical practice requires consideration of all discrepancies found.

Leptin in Dental Pulp and Periapical Tissues: A Narrative Review

Leptin is a non-glycosylated 16 kDa protein synthesized mainly in adipose cells. The main function of leptin is to regulate energy homeostasis and weight control in a central manner. There is increasing evidence that leptin also has systemic effects, acting as a link between innate and acquired immune responses. The expression of leptin and its receptor in human dental pulp and periradicular tissues have already been described, as well as several stimulatory effects of leptin protein expression in dental and periodontal tissues. The aim of this paper was to review and to compile the reported scientific literature on the role and effects of leptin in the dental pulp and periapical tissues. Twelve articles accomplished the inclusion criteria, and a comprehensive narrative review was carried out. Review of the available scientific literature concluded that leptin has the following effects on pulpal and periapical physiology: 1) Stimulates odontogenic differentiation of dental pulp stem cells (DPSCs), 2) Increases the expression of dentin sialophosphoprotein (DSPP) and dentin matrix protein-1 (DMP-1), odontoblastic proteins involved in odontoblastic differentiation and dentin mineralization, 3) Stimulates vascular endothelial growth factor (VEGF) expression in human dental pulp tissue and primary cultured cells of human dental pulp (hDPCs), 4) Stimulates angiogenesis in rat dental pulp cells, and 5) Induces the expression of interleucinas 6 and 8 in human periodontal ligament cells (hPDLCs). There is evidence which suggests that leptin is implicated in the dentin mineralization process and in pulpal and periapical inflammatory and reparative responses.

A critical analysis of research methods and experimental models to study pulpitis

Pulpitis is the inflammatory response of the dental pulp to a tooth insult, whether it is microbial, chemical, or physical in origin. It is traditionally referred to as reversible or irreversible, a classification for therapeutic purposes that determines the capability of the pulp to heal. Recently, new knowledge about dental pulp physiopathology led to orientate therapeutics towards more frequent preservation of pulp vitality. However, full adoption of these vital pulp therapies by dental practitioners will be achieved only following better understanding of cell and tissue mechanisms involved in pulpitis. The current narrative review aimed to discuss the contribution of the most significant experimental models developed to study pulpitis. Traditionally, in vitro two(2D)- or three(3D)-dimensional cell cultures or in vivo animal models were used to analyse the pulp response to pulpitis inducers at cell, tissue or organ level. In vitro 2D cell cultures were mainly used to decipher the specific roles of key actors of pulp inflammation such as bacterial by-products, pro-inflammatory cytokines, odontoblasts or pulp stem cells. However, these simple models did not reproduce the 3D organisation of the pulp tissue and, with rare exceptions, did not consider interactions between resident cell types. In vitro tissue/organ-based models were developed to better reflect the complexity of the pulp structure. Their major disadvantage is that they did not allow the analysis of blood supply and innervation participation. On the contrary, in vivo models have allowed researchers to identify key immune, vascular and nervous actors of pulpitis and to understand their function and interplay in the inflamed pulp. However, inflammation was mainly induced by iatrogenic dentine drilling associated with simple pulp exposure to the oral environment or stimulation by individual bacterial by-products for short periods. Clearly, these models did not reflect the long and progressive development of dental caries. Lastly, the substantial diversity of the existing models makes experimental data extrapolation to the clinical situation complicated. Therefore, improvement in the design and standardization of future models, for example by using novel molecular biomarkers, databased models and artificial intelligence, will be an essential step in building an incremental knowledge of pulpitis in the future.

Association between Oral Pathology, Carotid Stenosis, and Oral Bacterial DNA in Cerebral Thrombi of Patients with Stroke

Methods

Thrombus aspirates and control arterial blood were taken from 71 patients (70.4% male; mean age, 67.4 years) with acute ischemic stroke. Tooth pathology was registered using CT scans. Carotid stenosis was estimated with CTA and ultrasonography. The presence of bacterial DNA from aspirated thrombi was determined using quantitative PCR. We also analyzed the presence of these bacterial DNAs in carotid endarterectomies from patients with peripheral arterial disease.

Results

Bacterial DNA was found in 59 (83.1%) of the thrombus aspirates (median, 8.6-fold). Oral streptococcal DNA was found in 56 (78.9%) of the thrombus aspirates (median, 5.1-fold). DNA from A. actinomycetemcomitans and P. gingivalis was not found. Most patients suffered from poor oral health and had in median 19.0 teeth left. Paradoxically, patients with better oral health had more oral streptococcal DNA in their thrombus than the group with the worst pathology (p = 0.028). There was a trend (OR 7.122; p = 0.083) in the association of ≥50% carotid artery stenosis with more severe dental pathology. Oral streptococcal DNA was detected in 2/6 of carotid endarterectomies.

Conclusions

Stroke patients had poor oral health which tended to associate with their carotid artery stenosis. Although oral streptococcal DNA was found in thrombus aspirates and carotid endarterectomy samples, the amount of oral streptococcal DNA in thrombus aspirates was the lowest among those with the most severe oral pathology. These results suggest that the association between poor oral health and acute ischemic stroke is linked to carotid artery atherosclerosis.

Deciphering Reparative Processes in the Inflamed Dental Pulp

Research over several decades has increased our understanding of the nature of reparative and regenerative processes in the dental pulp, at both the cellular and molecular level. However, advances in scientific knowledge have not translated into novel clinical treatment strategies for caries-induced pulpitis. This narrative review explores the evidence regarding the ability of inflamed pulp tissue to heal and how this knowledge may be used therapeutically. A literature search and evidence analysis covering basic, translational and clinical pulp biology research was performed. The review focuses on (1) the regenerative and defense capabilities of the pulp during caries-induced inflammation; (2) the potential of novel biomaterials to harness the reparative and regenerative functions of the inflamed pulp; and (3) future perspectives and opportunities for conservative management of the inflamed pulp. Current conservative management strategies for pulpitis are limited by a combination of unreliable diagnostic tools and an outdated understanding of pulpal pathophysiological responses. This approach leads to the often unnecessary removal of the entire pulp. Consequently, there is a need for better diagnostic approaches and a focus on minimally-invasive treatments utilizing biologically-based regenerative materials and technologies.

Multifaceted effect of caffeic acid against Streptococcus mutans infection: microbicidal and immunomodulatory agent in macrophages

The aim of the present study was to investigate the effects of caffeic acid in the interface between the antimicrobial and anti-inflammatory function in macrophage response against S. mutans. S. mutans (10⁸ cfu/mL) were incubated with caffeic acid to determinate the half-maximal inhibitory concentration (IC₅₀) and macrophage cells were incubated with caffeic acid to determinate cell viability and toxicity. Anti-inflammatory effects were measured by nitrite accumulation, TNF-α and PGE₂ production, and NF-kB phosphorylation, and S. mutans survival following internalization by macrophages was investigated. We found that caffeic acid presented antimicrobial activity against S. mutans (IC₅₀ = 2.938 ± 0.1225 mM) without exerting cytotoxicity. Caffeic acid inhibited nitrite, TNF-α and PGE₂ production by the NF-kB dependent pathway, indicating an immunomodulatory property. Caffeic acid also contributed to macrophage bacteria clearance activity. In summary, caffeic acid presented antimicrobial activity against S. mutans and anti-inflammatory effects in macrophages.

The Genetic and Epigenetic Mechanisms Involved in Irreversible Pulp Neural Inflammation

AIM

To identify the critical genetic and epigenetic biomarkers by constructing the long noncoding RNA- (lncRNA-) related competing endogenous RNA (ceRNA) network involved in irreversible pulp neural inflammation (pulpitis).

MATERIALS AND METHODS

The public datasets regarding irreversible pulpitis were downloaded from the gene expression omnibus (GEO) database. The differential expression analysis was performed to identify the differentially expressed genes (DEGs) and DElncRNAs. Functional enrichment analysis was performed to explore the biological processes and signaling pathways enriched by DEGs. By performing a weighted gene coexpression network analysis (WGCNA), the significant gene modules in each dataset were identified. Most importantly, DElncRNA-DEmRNA regulatory network and DElncRNA-associated ceRNA network were constructed. A transcription factor- (TF-) DEmRNA network was built to identify the critical TFs involved in pulpitis.

RESULT

Two datasets (GSE92681 and GSE77459) were selected for analysis. DEGs involved in pulpitis were significantly enriched in seven signaling pathways (i.e., NOD-like receptor (NLR), Toll-like receptor (TLR), NF-kappa B, tumor necrosis factor (TNF), cell adhesion molecules (CAMs), chemokine, and cytokine-cytokine receptor interaction pathways). The ceRNA regulatory relationships were established consisting of three genes (i.e., LCP1, EZH2, and NR4A1), five miRNAs (i.e., miR-340-5p, miR-4731-5p, miR-27a-3p, miR-34a-5p, and miR-766-5p), and three lncRNAs (i.e., XIST, MIR155HG, and LINC00630). Six transcription factors (i.e., GATA2, ETS1, FOXP3, STAT1, FOS, and JUN) were identified to play pivotal roles in pulpitis.

CONCLUSION

This paper demonstrates the genetic and epigenetic mechanisms of irreversible pulpitis by revealing the ceRNA network. The biomarkers identified could provide research direction for the application of genetically modified stem cells in endodontic regeneration.

In vitro antimicrobial activity of mineral trioxide aggregate, Biodentine, and calcium-enriched mixture cement against Enterococcus faecalis, Streptococcus mutans, and Candida albicans using the agar diffusion technique

BACKGROUND

This study assessed the antimicrobial activity of Biodentine, mineral trioxide aggregate (MTA), and calcium-enriched mixture (CEM) cement against Enterococcus faecalis, Streptococcus mutans, and Candida albicans.

MATERIALS AND METHODS

In this in vitro study, microbial suspensions were inoculated onto agar plates. The antimicrobial effects of MTA, Biodentine and CEM cement were assessed against E. faecalis, S. mutans, and C. albicans by the agar diffusion test. In each experimental group, 7 plates containing 3 wells were prepared and immediately filled with freshly mixed cements. Positive and negative control plates were prepared with/without the bacterial suspension, respectively. After 2 h of preincubation at room temperature, the plates were incubated at 37°C for 24 h. The diameter of growth inhibition zones was measured after 24 h. Data were analyzed using ANOVA and Tukey's test (α = 0.05).

RESULTS

Biodentine showed strong antimicrobial activity against all three microorganisms with an average inhibition zone of 9.10 mm. The inhibitory effect of Biodentine on E. faecalis and C. albicans was significantly superior to that of the other two cements (P < 0.05). MTA and CEM cement showed significantly higher antimicrobial activity against S. mutans (P < 0.05). The antimicrobial effects of Biodentine on S. mutans and E. faecalis were significantly greater than on C. albicans (P < 0.05).

CONCLUSION

All cements revealed antimicrobial properties against the tested microbial strains. Biodentine had stronger antimicrobial effects against E. faecalis and C. albicans compared with MTA and CEM cement. Furthermore, the largest inhibition zones around all three cements belonged to S. mutans.

Tailored 70S30C Bioactive glass induces severe inflammation as pulpotomy agent in primary teeth: an interim analysis of a randomised controlled trial

OBJECTIVES

This study compared clinical, histologic, and inflammatory outcomes of Biodentine and Bioactive glass (70S30C-BAG) as pulpotomy agents in primary teeth.

METHODS

A randomised, clinical trial was performed recruiting 70 children, 5-9 years old, having ≥ 1 tooth indicated for vital pulpotomy. Participants were randomised to Biodentine or 70S30C-BAG groups. Clinical evaluation was scheduled at 1, 3, 6, 9, and 12 months. Additional 16 teeth were extracted after 6 weeks to assess histologic and inflammatory response (IL-8/IL-10 ratio) using ELISA. Fisher exact, Mann Whitney U test, and t test were used to compare clinical, histologic outcomes and IL-8/IL-10 ratio.

RESULTS

After 3 months, 10 teeth treated with Biodentine were clinically successful, while 9 teeth treated with 70S30C-BAG failed (P < 0.001) necessitating trial termination. Causes of failure were analysed by assessing the pH and ionic release of 70S30C-BAG. Biodentine-treated teeth showed minor inflammation, normal pulp, and hard tissue formation.70S30C-BAG-treated teeth showed severe inflammation, abscesses, root resorption without hard tissue formation. There was a significantly greater percent reduction of IL-8/IL-10 ratio in Biodentine than 70S30C-BAG (mean ± SD = 66.39 ± 18.56 and 40.66 ± 0.86, P = 0.02).

CONCLUSIONS

Biodentine showed favourable clinical, histologic, and anti-inflammatory outcomes, promoting pulp healing and regeneration. 70S30C-BAG resulted in pulp necrosis-through persistent inflammation-causing clinical failure.

CLINICAL RELEVANCE

Biodentine is a promising pulpotomy agent in primary teeth; it promoted healing and regeneration of the dentine-pulp complex. In its current form, 70S30C-BAG is not a suitable pulpotomy agent; it induced persistent inflammation, negating the pulp ability to heal and regenerate. TRN: NCT03786302, 12/19/2018.

Deep metagenomics examines the oral microbiome during dental caries, revealing novel taxa and co-occurrences with host molecules

Dental caries, the most common chronic infectious disease worldwide, has a complex etiology involving the interplay of microbial and host factors that are not completely understood. In this study, the oral microbiome and 38 host cytokines and chemokines were analyzed across 23 children with caries and 24 children with healthy dentition. De novo assembly of metagenomic sequencing obtained 527 metagenome-assembled genomes (MAGs), representing 150 bacterial species. Forty-two of these species had no genomes in public repositories, thereby representing novel taxa. These new genomes greatly expanded the known pangenomes of many oral clades, including the enigmatic Saccharibacteria clades G3 and G6, which had distinct functional repertoires compared to other oral Saccharibacteria. Saccharibacteria are understood to be obligate epibionts, which are dependent on host bacteria. These data suggest that the various Saccharibacteria clades may rely on their hosts for highly distinct metabolic requirements, which would have significant evolutionary and ecological implications. Across the study group, Rothia, Neisseria, and Haemophilus spp. were associated with good dental health, whereas Prevotella spp., Streptococcus mutans, and Human herpesvirus 4 (Epstein-Barr virus [EBV]) were more prevalent in children with caries. Finally, 10 of the host immunological markers were significantly elevated in the caries group, and co-occurrence analysis provided an atlas of potential relationships between microbes and host immunological molecules. Overall, this study illustrated the oral microbiome at an unprecedented resolution and contributed several leads for further study that will increase the understanding of caries pathogenesis and guide therapeutic development.

[Advances in oral bacteria influencing host epigenetic regulation]

Epigenetics refers to a steady change in the level of gene expression caused by non-DNA sequence changes. Microbes can modulate host inflammation through epigenetic pathways to evade or expend immune responses. As an important part of human microbes, oral bacteria also have various epigenetic regulation mechanisms to affect host inflammatory responses. This article reviews the common pathways of epigenetic regulation in microbe infection and the regulation of host epigenetics by using oral microbes to provide a reference for the study of epigenetic-related mechanisms in oral diseases.

Semaphorin3A released from human dental pulp cells inhibits the increase in interleukin-6 and CXC chemokine ligand 10 production induced by tumor necrosis factor-α through suppression of nuclear factor-κB activation

Human dental pulp cells (HDPCs) play an important role in pulpitis. Semaphorin3A (Sema3A), which is an axon guidance molecule, is a member of the secretory semaphorin family. Recently, Sema3A has been reported to be an osteoprotective factor and to be involved in the immune response. However, the role of Sema3A in dental pulp inflammation remains unknown. The aim of this study was to reveal the existence of Sema3A in human dental pulp tissue and the effect of Sema3A which is released from tumor necrosis factor (TNF)-α-stimulated HDPCs on production of proinflammatory cytokines, such as interleukin (IL)-6 and CXC chemokine ligand 10 (CXCL10), from HDPCs stimulated with TNF-α. Sema3A was detected in inflamed pulp as compared to normal pulp. HDPCs expressed Neuropilin-1(Nrp1) which is Sema3A receptor. TNF-α increased the levels of IL-6 and CXCL10 in HDPCs in time-dependent manner. Sema3A inhibited production of these two cytokines from TNF-α-stimulated HDPCs. TNF-α induced soluble Sema3A production from HDPCs. Moreover, antibody-based neutralization of Sema3A further promoted production of IL-6 and CXCL10 from TNF-α-stimulated HDPCs. Sema3A inhibited nuclear factor (NF)-κB P65 phosphorylation and inhibitor κBα degradation in TNF-α-stimulated HDPCs. These results indicated that Sema3A is induced in human dental pulp, and TNF-α acts on HDPCs to produce Sema3A, which partially inhibits the increase in IL-6 and CXCL10 production induced by TNF-α, and that the inhibition leads to suppression of NF-κB activation. Therefore, it is suggested that Sema3A may regulate inflammation in dental pulp and be novel antiinflammatory target molecule for pulpitis.

Oral Bacterial Signatures in Cerebral Thrombi of Patients With Acute Ischemic Stroke Treated With Thrombectomy

Background

Chronic infections have been reported to be risk factors for both coronary heart disease and ischemic stroke. DNA of oral bacteria, mainly from the viridans streptococci group, has been detected in coronary thrombus aspirates of myocardial infarction and cerebral aneurysms. Viridans streptococci are known to cause infective endocarditis and possess thrombogenic properties. We studied the presence of oral bacterial DNA in thrombus aspirates of patients with acute ischemic stroke treated with mechanical thrombectomy.

Methods and Results

Thrombus aspirates and arterial blood were taken from 75 patients (69% men; mean age, 67 years) with acute ischemic stroke. The presence of Streptococcus species, mainly the Streptococcus mitis group, belonging to viridans streptococci as well as Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans in samples were determined using a quantitative polymerase chain reaction with specific primers and probes. The relative amount of bacterial DNA in a sample was determined with the comparative threshold cycle method. Bacterial DNA was detected in 84% (n=63) of aspired thrombi, and 16% (n=12) of samples were considered bacterial DNA negative. DNA of Streptococcus species, mainly the S mitis group, was found in 79% (n=59) of samples. The median relative amount of Streptococcus species DNA was 5.10‐fold higher compared with the control blood samples from the same patients. All thrombi were negative for both P gingivalis and A actinomycetemcomitans.

Conclusions

This is the first study showing the common presence of bacterial DNA from viridans streptococci in aspired thrombi of patients with acute ischemic stroke. Streptococcal bacteria, mostly of oral origin, may contribute to the progression and thrombotic events of cerebrovascular diseases.

Resinous adhesive systems differentially affect the expression of cytokines by human monocytes stimulated or not with Streptococcus mutans in vitro

OBJECTIVES

The polymerization of adhesive systems is incomplete and the residual monomers that have been released have a cytotoxic capacity. Some teeth develop into pulp necrosis after composite resin restorations. Considering frequent pulpal inflammation in response to cariogenic bacteria, substances released from the patches could affect the cells of the inflammatory infiltrate and interfere with the mechanisms of defense against microorganisms and protection of pulpal tissue. The aim of this study was to evaluate the effect of substances released by different resinous adhesive systems on cell viability and cytokine expression by human monocytes stimulated in vitro with Streptococcus mutans.

DESIGN

Peripheral blood mononuclear cells from 10 healthy subjects were stimulated with S. mutans and then incubated with supernatants obtained from the Single Bond Universal (SBU) or Clearfil SE Bond (CSEB) adhesive systems for eight hours. Staining with Annexin V and 7AAD for analysis of apoptosis were performed and detection of monocytes expressing cytokines IL-1α, IL-6, IL-8, IL-10, IL-12 and TNF-α were performed by flow cytometry.

RESULTS

No treatment significantly affected apoptosis in monocytes. SBU supernatant increased the frequency of monocytes expressing IL-8 and decreased the monocytes expressing IL-10. Considering S. mutans-stimulated cells, while SBU increased the frequency of IL-8⁺ monocytes, CSEB reduced the frequency of IL-6 and TNF-α positive monocytes.

CONCLUSIONS

Products released from SBU seem to induce proinflammatory effects on monocytes while those from CSEB show an anti-inflammatory outcome. These effects may interfere in the control of cytokine-mediated immunoinflammatory pulp reactions, both in the presence and absence of stimulation by cariogenic bacteria.

Effect of dental caries on periodontal inflammatory status: A split-mouth study

OBJECTIVE

This controlled split-mouth study aimed to estimate the effect of caries and related treatment on concentrations of interleukin (IL)-2, interferon (IFN)-γ, IL-12, IL-17A, IL-13, IL-10, IL-6, IL-5, IL-4, IL-22, tumor necrosis factor (TNF)-α, and IL1-β in gingival crevicular fluid (GCF) of caries affected teeth before (B), 7 (7D) and 30 (30D) days post-treatment and to compare them with concentrations from healthy teeth.

DESIGN

Study population included 81 systemically and periodontally healthy non-smokers exhibiting at least one shallow occlusal/ inter-proximal caries and one healthy tooth from the same morphologic group at the contralateral position. Following clinical exam, the GCF samples were collected baseline as well as 7D and 30D, while the biomarker measurement was performed using multiplex flowcytometry.

RESULTS

Caries affected teeth exhibited significantly higher levels of IFN-γ, IL-1β, IL-2, IL-4 and IL-6 when compared to healthy teeth. Post-treatment cytokines levels showed general trend of increase when compared to baseline, that was significant for IL-22 and IL-17 at 7D, while IFN-γ was significantly increased at 7D compared to the healthy teeth. At 30D, IFN-γ, TNF-α, IL-17 and IL-4 levels were significantly increased when compared to healthy teeth, while IL-2 levels were significantly higher than baseline levels.

CONCLUSION

Considering significantly increased periodontal levels of inflammatory markers in caries affected teeth and in response to performed treatment, it seems that dental caries and related restorative treatment might contribute to periodontal inflammation via additive effects already in early-stage caries.

Heparin-LL37 complexes are less cytotoxic for human dental pulp cells and have undiminished antimicrobial and LPS-neutralizing abilities

AIM

To investigate whether glycosaminoglycans (GAGs) binding to high-dose LL37 eliminates its cytotoxicity to dental pulp cells (hDPCs) whilst retaining undiminished antimicrobial and LPS-neutralizing abilities.

METHODOLOGY

hDPCs were stimulated with varying concentrations of LL37, and their cell viability was analysed by MTT. Then, high-dose LL37 (10 μmol L^-1 ) was bound to varying concentrations of three GAGs, heparin, chondroitin sulphate and hyaluronic acid, and their cytotoxic effects on hDPCs and antimicrobial effects were evaluated and compared. Furthermore, the LPS-neutralizing ability of heparin (5 μg mL^-1 )-LL37 (10 μmol L^-1 ) complexes, which were found to be less cytotoxic for hDPCs with undiminished antimicrobial ability, was investigated. Statistical analysis was performed using one-way analysis of variance (anova), followed by Dunnett's test. P values below 0.05 were considered significant.

RESULTS

LL37 significantly reduced the cell viability of hDPCs in a dose-dependent manner (P < 0.01). LL37 (10 μmol L^-1 ) binding to heparin within a limited concentration range (2~6 μg mL^-1 ) eliminated the cytotoxicity for hDPCs (P < 0.01) whilst exerting potent antimicrobial effects against Streptococcus mutans, Streptococcus sobrinus, Streptococcus salivarius, Aggegatibacter actinomycetemcomitans and Escherichia coli. LL37 (10 μmol L^-1 ) binding to chondroitin sulphate exhibited similar functions (P < 0.01); however, the effective chondroitin sulphate concentration was highly restricted (3 μg mL^-1 ). LL37 (10 μmol L^-1 ) binding to hyaluronic acid was unable to abrogate the cytotoxicity of LL37 even at higher concentrations (10 and 100 μg mL^-1 ). Moreover, exogenous addition of LPS dose-dependently reduced the amount of LL37 precipitated with the heparin-LL37 agarose beads (P < 0.01), and the released LL37 simultaneously neutralized the pro-inflammatory ability of LPS in macrophages (P < 0.01).

CONCLUSIONS

Heparin-LL37 complexes generated at suitable concentration ratios are easy to make, are less cytotoxic and are broad-range antimicrobial materials that can neutralize LPS by providing LL37 in accordance with the amount of free LPS. They may be a potential treatment to save dental pulp tissue from the acute inflammation exacerbated by invading bacteria and the LPS they release.

Up-regulation of microRNA-223 inhibits brain injury and hippocampal neuron apoptosis of rats after febrile seizure through the NLRP3-Caspase-1 signaling pathway

OBJECTIVE

This study is conducted to explore the role of microRNA-223 (miR-223) in brain injury and apoptosis of hippocampal neurons through the NLRP3-Caspase-1 signaling pathway in febrile seizure (FS) rats.

METHODS

The models of FS were induced in rats by hot water-bath, which were stereotactically injected with miR-223 mimics and mimics negative control (NC) to perturb the expression of miR-223. A series of experiments was conducted to find out the potential mechanisms of miR-223 on convulsion attack, learning and memory ability, pathological injury of hippocampal neurons, inflammatory injury, apoptosis of hippocampal neurons in FS rats. Besides, the targeting relationship between miR-223 and NLRP3 was also verified.

RESULTS

Low expression of miR-223 was found in hippocampus tissues of FS rats. Up-regulation of miR-223 alleviated convulsion attack and improved learning and memory ability, while inhibiting pathological injury of hippocampal neurons and inflammatory injury in FS rats. Up-regulation of miR-223 promoted the survival of hippocampal neurons and inhibited their apoptosis in FS rats. MiR-223 inhibited the activation of NLRP3-Caspase-1 signaling pathway in hippocampus tissues of FS rats by inhibiting NLRP3.

CONCLUSION

The inhibited expression of miR-223 after FS may participate in the activation of the NLRP3-Caspase-1 signaling pathway, resulting in brain injury and apoptosis of hippocampal neurons in rat models of FS.

C5L2 Silencing in Human Pulp Fibroblasts Enhances Nerve Outgrowth Under Lipoteichoic Acid Stimulation

INTRODUCTION

We recently reported that caries-associated C5a receptor (C5aR) expression and activation result in up-regulation of brain-derived neurotropic factor secretion by pulp fibroblasts inducing prominent neurite outgrowth toward the carious site. Our data further showed a negative regulation of this brain-derived neurotropic factor secretion by C5L2, another C5aR. C5L2 was considered a nonfunctional receptor and thus has received much less attention than C5aR. The aim of this study was to identify the role of C5L2 in pulp fibroblast-mediated neurite outgrowth.

METHODS

In this study, lipoteichoic acid (LTA) was used to mimic dental caries-like inflammation. To evaluate the role of C5L2 in pulp neurite outgrowth, human pulp fibroblasts were C5L2 small interfering RNA silenced and cocultured with human neurons in a nerve growth assay system.

RESULTS

C5L2 silencing drastically increased the neurite outgrowth toward the LTA-stimulated pulp fibroblasts. The number of neurites detected was increased in the LTA-treated pulp fibroblasts.

CONCLUSIONS

Our results show that C5L2 constitutes a negative regulator of the neurite outgrowth under LTA stimulation. Of the events occurring during dentin-pulp regeneration, nerve regeneration is the key factor for maintaining tooth viability after infection or injury. Our study provides a foundation for creating therapeutic tools that target pulp fibroblasts during pulp/nerve regeneration.

Human Dental Pulp Cells Express Cellular Markers for Inflammation and Hard Tissue Formation in Response to Bacterial Information

INTRODUCTION

Lipopolysaccharide (LPS) is a major component of the outer membranes of gram-negative bacteria associated with deep dental caries and pulpitis. When bacteria invade dentinal tubes and dentin is continually destroyed, tertiary dentin is formed by preexisting odontoblasts. However, the relationship between LPS and tertiary dentin formation remains unclear. We investigated whether LPS stimulation induces the formation of hard tissue in human dental pulp cells (hDPCs).

METHODS

Immortalized hDPCs were cultured, and Escherichia coli-derived LPS (1 μg/mL) was incorporated into the culture medium. Samples were obtained after 0, 1, 3, 7, 14, and 21 days, and messenger RNA expression of IL-1β, IL-6, Wnt5a, Runx2, ALP, and alkaline phosphatase (ALP) activity was investigated.

RESULTS

Quantitative real-time polymerase chain reaction revealed higher messenger RNA expression levels of IL-1β and IL-6 in the LPS group on 1 day (P < .05). The expression levels of dentinogenesis-related markers including Wnt5a, Runx2, and ALP were higher in the LPS group (2.0-, 4.7- and 10.0-fold, respectively) than that in the control group at 14 days (P < .01). ALP activity was significantly stronger in the LPS group than in the control group at 21 days (P < .01). Treatment of Box5, an antagonist of Wnt5a, showed a decreased expression of Runx2 and ALP (P < .05).

CONCLUSIONS

These results indicate that LPS stimulation induces the gene expression of inflammatory cytokines and hard tissue formation through Wnt5a signaling pathways in hDPCs.

The roles of odontoblasts in dental pulp innate immunity

Odontoblasts located in the outermost layer of dental pulp form a natural barrier between mineralized tissues, dentin, and soft tissues, dental pulp, of the vital tooth, and they first recognize caries-related pathogens and sense external irritations. Therefore, odontoblasts possess a specialized innate immune system to fight oral pathogens invading into dentin. Generally, the rapid initial sensing of microbial pathogens, especially pathogen-associated molecular patterns (PAMPs) shared by microorganisms, are mediated by pattern recognition receptors (PRRs), such as Toll-like receptor and the nucleotide-binding oligomerization domain (NOD). The innate immune responses in odontoblasts initiated by sensing oral pathogens provide host protective events, such as inflammatory reactions, to produce a variety of pro-inflammatory mediators, including chemokines and cytokines. These attract various inflammatory cells and cause antibacterial reactions, such as the production of defensins, to kill microorganisms in the proximal region of the odontoblast layer. This review focuses on innate immunity, especially cellular and molecular mechanisms regarding the sensing of PAMPs from oral pathogens by PRRs, in odontoblasts and provides information for future studies for the development of novel therapeutic strategies, including diagnosis and treatment, to prevent exceeding dental pulp inflammation and preserve the dental pulp tissues.

Efficacy of removal of cariogenic bacteria and carious dentin by ablation using different modes of Er:YAG lasers

The primary objective of this in vitro study was to evaluate the efficiency of removal of cariogenic bacteria and carious dentin by ablation using two lasers: fluorescence-feedback controlled (FFC) Er:YAG laser and different pulses of Er:YAG laser based on variable square pulse technology (VSPt). The secondary objective was to measure the temperature during laser ablation of carious tissue. Seventy-two extracted human molars were used in this study. Sixty teeth with carious dentin were randomly divided into four experimental groups according to the treatment for caries removal: group 1: 400 µs (FFC group); group 2: super short pulse (SSP group, 50 µs pulse); group 3: medium short pulse (MSP group, 100 µs pulse); group 4: short pulse (SP group, 300 µs pulse) and one positive control group with no treatment. Twelve teeth without carious lesion were used as a negative control group. After caries removal, swabs were taken with cotton pellets and real-time PCR analysis was performed. During caries ablation, a thermal infrared camera was used to measure the temperature changes. In all experimental groups, specimens were free of bacterial contamination after the treatment. In the SSP, MSP and SP groups, temperatures measured during caries ablation were significantly higher compared to temperatures in the FFC group (P<0.001). In this in vitro study, laser treatment for removal of carious dentin and cariogenic bacteria was an efficient treatment modality without causing excessive temperatures that might adversely affect pulp vitality.

Oral Neuroimmune Network and Mast Cells

Inflammation is a critical process in the oral cavity, especially in gingival inflammation and pulpitis, as seen in periodontitis and decayed tooth structure. Nevertheless, the cellular process involved in oral inflammation is not well delineated. Recent evidence from other organs as well as the mouth suggests that neurogenic inflammation involving mast cells (MCs) may be a critical factor. MCs, best known for their role in allergic reactions, are also involved in immunity and inflammation. They are located at strategic points close to small blood vessels and nerve fibers often containing substance P (SP). The pain models of reversible or irreversible pulpitis simply suggest the complexity of neural-inflammatory interactions within the dental pulp. In the pulp and periapical area, neuropeptides and cytokines modulate vascular responses, increase permeability and leukocyte migration. SP-immunoreactive nerve fibers and TNF-positive MCs were found localized around blood vessels in all samples of periapical granulomas. By generating a profound number of potent mediators, MCs may serve as a link between the immune, endocrine and nervous systems in pulp inflammation. This role has been strengthened by recent evidence of MCs involvement in inflammatory conditions.

The innate host response in caries and periodontitis

INTRODUCTION

Innate immunity rapidly defends the host against infectious insults. These reactions are of limited specificity and exhaust without providing long-term protection. Functional fluids and effector molecules contribute to the defence against infectious agents, drive the immune response, and direct the cellular players.

AIM

To review the literature and present a summary of current knowledge about the function of tissues, cellular players and soluble mediators of innate immunity relevant to caries and periodontitis.

METHODS

Historical and recent literature was critically reviewed based on publications in peer-reviewed scientific journals.

RESULTS

The innate immune response is vital to resistance against caries and periodontitis and rapidly attempts to protect against infectious agents in the dental hard and soft tissues. Soluble mediators include specialized proteins and lipids. They function to signal to immune and inflammatory cells, provide antimicrobial resistance, and also induce mechanisms for potential repair of damaged tissues.

CONCLUSIONS

Far less investigated than adaptive immunity, innate immune responses are an emerging scientific and therapeutic frontier. Soluble mediators of the innate response provide a network of signals to organize the near immediate molecular and cellular response to infection, including direct and immediate antimicrobial activity. Further studies in human disease and animal models are generally needed.

Inflammatory cytokines in normal and irreversibly inflamed pulps: A systematic review

OBJECTIVE

To review the available literature in regard to the inflammatory process and pulpitis. Setting forth to evaluate if differences in the levels of various cytokines (TNF-α, IL-1β, IL-2, IL-6 and IL-8) can be observed in clinically diagnosed normal and irreversibly inflamed pulps that could serve as possible markers and/or diagnostic tools to predict and differentiate between certain states of inflammation. Methods used to measure and assess levels of cytokines have been limited to two protein quantification methods ELISA and/or Multiplex Array.

DESIGN

The databases PubMed, EMBASE/Ovid, The Cochrane Central Register of Controlled Trials, Cochrane Reviews and Scopus were consulted for the electronic literature search. Screening of titles and abstracts followed the PRISMA guidelines while data extraction and the assessment of the full texts were carried out in accordance to the GRADES assessment.

RESULTS

The review showed that significant increases in levels of IL-1β, IL-2, IL-6, IL-8 and TNF-α in irreversible pulpitis samples exist, in comparison to normal pulp samples which serve as a good basis for potential markers. Due to larger discrepancies in available literature, IL-2 seems rather unsuitable at the moment, while IL-6 and TNF alpha seem to be more promising.

CONCLUSION

It may be concluded that even by combining two protein quantification methods inconsistencies between studies exist. At the moment it is difficult to select just one specific cytokine suitable for testing, rather it supports the rationale that further high-quality clinical studies are needed.

Role of leptin as a link between metabolism and the immune system

Leptin is an adipocyte-derived hormone not only with an important role in the central control of energy metabolism, but also with many pleiotropic effects in different physiological systems. One of these peripheral functions of leptin is a regulatory role in the interplay between energy metabolism and the immune system, being a cornerstone of the new field of immunometabolism. Leptin receptor is expressed throughout the immune system and the regulatory effects of leptin include cells from both the innate and adaptive immune system. Leptin is one of the adipokines responsible for the inflammatory state found in obesity that predisposes not only to type 2 diabetes, metabolic syndrome and cardiovascular disease, but also to autoimmune and allergic diseases. Leptin is an important mediator of the immunosuppressive state in undernutrition status. Placenta is the second source of leptin and it may play a role in the immunomodulation during pregnancy. Finally, recent work has pointed to the participation of leptin and leptin receptor in the pathophysiology of inflammation in oral biology. Therefore, leptin and leptin receptor should be considered for investigation as a marker of inflammation and immune activation in the frontier of innate-adaptive system, and as possible targets for intervention in the immunometabolic mediated pathophysiology.

Pro-inflammatory Cytokines Up-regulate MUC1 Gene Expression in Oral Epithelial Cells

The membrane-bound mucin MUC1 is expressed ubiquitously on epithelial surfaces and is thought to provide protection from bacterial and chemical injury. The present study was undertaken to determine whether MUC1 was expressed in cultured oral epithelial cells and whether expression is modulated by pro-inflammatory mediators released as part of the host response to infection by oral pathogens. Northern and Western blotting experiments showed that KB cells express MUC1 mRNA and protein. When cells were treated with interleukins (IL-1β, IL-6), tumor necrosis factor-alpha (TNF-α), or interferon-gamma (IFN-γ), or combinations of these, real-time PCR demonstrated that MUC1 mRNA increased 1.4- to 3.2-fold. Interestingly, a significant increase in levels of MUC1 protein was also observed. While no effect was observed when KB cells were incubated with LPS from Porphyromonas gingivalis, infection of KB monolayers with this oral pathogen caused a 2.85-fold increase in MUC1 transcript levels. These results suggest that increased MUC1 synthesis may be a key element in the host response to infection with oral pathogens.

Caries-related Bacteria and Cytokines Induce CXCL10 in Dental Pulp

Marked infiltration of inflammatory cells, such as activated T-cells, is observed in the progression of pulpitis; however, little is known about the mechanism of their recruitment into pulpal lesions. It has been recently demonstrated that CXC chemokine ligand 10 (CXCL10) chemoattracts CXC chemokine receptor 3 (CXCR3)-positive activated T-cells. We therefore examined whether CXCL10 is involved in the pathogenesis of pulpitis. CXCL10 mRNA expression levels in clinically inflamed dental pulp were higher than those in healthy dental pulp. Immunostaining results revealed that CXCL10 was detected in macrophages, endothelial cells, and fibroblasts in inflamed dental pulp, and that CXCR3 expression was observed mainly on T-cells. Moreover, cultured dental pulp fibroblasts produced CXCL10 after stimulation with live caries-related bacteria, peptidoglycans, and pro-inflammatory cytokines. In contrast, heat-killed bacteria did not induce CXCL10 secretion. These findings suggest that CXCL10-CXCR3 may play an important role in the pulpal immune response to caries-related bacterial invasion. Abbreviations: CXCL10, CXC chemokine ligand 10; CXCR3, CXC chemokine receptor 3; IFN, interferon; FBS, fetal bovine serum; LTA, lipoteichoic acid; PGN, peptidoglycan; IL, interleukin; TNF, tumor necrosis factor; PBS, phosphate-buffered saline; ELISA, enzyme-linked immunosorbent assay; CCL, C-C chemokine ligand; TLR, Toll-like receptor; NOD, nucleotide oligomerization domain; HDPF, human dental pulp fibroblasts.

DPSCs from Inflamed Pulp Modulate Macrophage Function via the TNF-α/IDO Axis

Human dental pulp stem cells (DPSCs) can be isolated from inflamed pulp derived from carious teeth with symptomatic irreversible pulpitis (I-DPSCs), which possess stemness and multidifferentiation potentials similar to DPSCs from healthy pulp. Since macrophages-essential cell players of the pulpal innate immunity-can regulate pulpal inflammation and repair, the authors investigated the immunomodulatory effects of DPSCs/I-DPSCs on macrophage functions and their underlying mechanisms. Similar to DPSCs, I-DPSCs were capable of colony-forming efficiency and adipogenic and osteo/dentinogenic differentiation under in vitro induction conditions. I-DPSCs also expressed a similar phenotypic profile of mesenchymal stem cell markers, except a relatively higher level of CD146 as compared with DPSCs. Coculture of DPSCs or I-DPSCs with differentiated THP-1 cells, the human monocyte cell line, markedly suppressed tumor necrosis factor α (TNF-α) secretion in response to stimulation with lipopolysaccharides (LPS) and/or nigericin. However, unlike TNF-α, the secreted level of interleukin 1β was not affected by coculture with DPSCs or I-DPSCs. Furthermore, DPSC/I-DPSC-mediated inhibition of TNF-α secretion by macrophages was abolished by pretreatment with 1-methyl-D-tryptophan, a specific inhibitor of indoleamine-pyrrole 2,3-dioxygenase (IDO), but not by NSC-398, a specific inhibitor of COX-2, suggesting IDO as a mediator. Interestingly, IDO expression was significantly augmented in macrophages and mesenchymal stromal cells in inflamed human pulp tissues. Collectively, these findings show that I-DPSCs, similar to DPSCs, possess stem cell properties and suppress macrophage functions via the TNF-α/IDO axis, thereby providing a physiologically relevant context for their innate immunomodulatory activity in the dental pulp and their capability for pulp repair.

Structural and recovery mechanisms of 3D dental pulp cell microtissues challenged with Streptococcusmutans in extracellular matrix environment

Cariopathogen Streptococcus mutans exists in infected dental pulp of deciduous teeth and is frequently linked with heart diseases. Organotypic (3D) dental pulp stem cell (DPSC) cultures/microtissues, developed to mimic the physiological conditions in vivo, were utilized to assess the bacterial impact on their (i) 3D structural configuration and (ii) recovery mechanisms. The cultures, developed in extracellular matrix (ECM) bio-scaffold (Matrigel™), interacted with WT and GFP-tagged bacterial biofilms by permitting their infiltration through the ECM. Challenged cell constructs were visualized by F-actin/nuclei staining. Their pluripotency (Sox2) and differentiation (osteocalcin) markers were assessed by immunocytochemistry. Secreted mineral was detected by alizarin red, and 3D structural arrangements were analysed by epi-fluorescence and confocal scanning microscopy. Bacterial biofilm/ECM-embedded DPSC interactions appeared in distinct areas of the microtissues. Bacterial attachment to the cell surface occurred without evidence of invasion. Surface architecture of the challenged versus unchallenged microtissues was apparently unaltered. However, significant increases in thickness (138.42 vs 106.51 µm) and bacterial penetration were detected in challenged structures causing canal-like microstructures with various diameters (12.94 -42.88 µm) and average diameter of 20.66 to 33.42 µm per microtissue. Challenged constructs expressed pluripotency and differentiation markers and secreted the mineral. Presented model shows strong potential for assessing pulp-pathogen interactions in vivo. S. mutans infiltrated and penetrated the microtissues but did not invade the cells or compromise major cell repair mechanisms. These findings would suggest reexamining the role of S. mutans as an endodontic pathogen and investigating DPSC resistance to its pathogenicity.

Lipoteichoic acids as a major virulence factor causing inflammatory responses via Toll-like receptor 2

Lipoteichoic acid (LTA), a major cell wall component of Gram-positive bacteria, is associated with various inflammatory diseases ranging from minor skin diseases to severe sepsis. It is known that LTA is recognized by Toll-like receptor 2 (TLR2), leading to the initiation of innate immune responses and further development of adaptive immunity. However, excessive immune responses may result in the inflammatory sequelae that are involved in severe diseases such as sepsis. Although numerous studies have tried to identify the molecular basis for the pathophysiology of Gram-positive bacterial infection, the exact role of LTA during the infection has not been clearly elucidated. This review provides an overview of LTA structure and host recognition by TLR2 that leads to the activation of innate immune responses. Emphasis is placed on differential immunostimulating activities of LTAs of various Gram-positive bacteria at the molecular level.

DPSCs from Inflamed Pulp Modulate Macrophage Function via the TNF-α/IDO Axis

Human dental pulp stem cells (DPSCs) can be isolated from inflamed pulp derived from carious teeth with symptomatic irreversible pulpitis (I-DPSCs), which possess stemness and multidifferentiation potentials similar to DPSCs from healthy pulp. Since macrophages-essential cell players of the pulpal innate immunity-can regulate pulpal inflammation and repair, the authors investigated the immunomodulatory effects of DPSCs/I-DPSCs on macrophage functions and their underlying mechanisms. Similar to DPSCs, I-DPSCs were capable of colony-forming efficiency and adipogenic and osteo/dentinogenic differentiation under in vitro induction conditions. I-DPSCs also expressed a similar phenotypic profile of mesenchymal stem cell markers, except a relatively higher level of CD146 as compared with DPSCs. Coculture of DPSCs or I-DPSCs with differentiated THP-1 cells, the human monocyte cell line, markedly suppressed tumor necrosis factor α (TNF-α) secretion in response to stimulation with lipopolysaccharides (LPS) and/or nigericin. However, unlike TNF-α, the secreted level of interleukin 1β was not affected by coculture with DPSCs or I-DPSCs. Furthermore, DPSC/I-DPSC-mediated inhibition of TNF-α secretion by macrophages was abolished by pretreatment with 1-methyl-D-tryptophan, a specific inhibitor of indoleamine-pyrrole 2,3-dioxygenase (IDO), but not by NSC-398, a specific inhibitor of COX-2, suggesting IDO as a mediator. Interestingly, IDO expression was significantly augmented in macrophages and mesenchymal stromal cells in inflamed human pulp tissues. Collectively, these findings show that I-DPSCs, similar to DPSCs, possess stem cell properties and suppress macrophage functions via the TNF-α/IDO axis, thereby providing a physiologically relevant context for their innate immunomodulatory activity in the dental pulp and their capability for pulp repair.

Conditioned medium from human bone marrow stromal cells attenuates initial inflammatory reactions in dental pulp tissue

AIM

To evaluate the effect of MSC-conditioned medium (CM) on the secretion of pro- and anti-inflammatory cytokines from dental pulp cells (hDPC) in vitro, and on the gene expression in vivo after replantation of rat molars.

MATERIALS AND METHODS

hDPC were cultured in CM for 24 h, and the concentration of interleukin IL-10, IL-4, IL-6, and IL-8, regulated on activation, normal T Cell expressed and secreted (RANTES), and prostaglandin E₂ (PGE₂ ) in the media were measured by multiplex assay and ELISA, respectively. Expression of cyclooxygenase-2 (COX-2) was also examined by Western blot analysis after 24 h. Left and right maxillary first rat molars (n = 20) were elevated for 2 min and then replanted with or without application of CM into the tooth sockets. Levels of IL-1β, IL-10, IL-4, IL-6, and IL-8, and tumor necrosis factor-alpha (TNF-α) mRNA were evaluated by real-time qRT-PCR 3 and 14 days following tooth replantation.

RESULTS

The production of IL-8, IL-10, and IL-6, RANTES and PGE₂ by cells cultured in CM was significantly higher than production by cells cultured in standard medium (DMEM). At day 3 following replantation in vivo, the levels of IL-1β and IL-6, and TNF-α mRNA were significantly lower in the CM-treated replanted teeth compared with control teeth. Further, at day 3, the IL-6/IL-10 ratio was significantly lower in the CM-treated replanted teeth compared with control. At day 14 following replantation, no differences in the mRNA ratios were detected between the pulp tissues of replanted and control teeth.

CONCLUSIONS

These findings indicated that CM promotes secretion of pro- and anti-inflammatory cytokines from hDPCin vitro and attenuates the initial inflammatory response in the rat dental pulp in vivo following tooth replantation.

Epigenetic regulation in dental pulp inflammation

Dental caries, trauma, and other possible factors could lead to injury of the dental pulp. Dental infection could result in immune and inflammatory responses mediated by molecular and cellular events and tissue breakdown. The inflammatory response of dental pulp could be regulated by genetic and epigenetic events. Epigenetic modifications play a fundamental role in gene expression. The epigenetic events might play critical roles in the inflammatory process of dental pulp injury. Major epigenetic events include methylation and acetylation of histones and regulatory factors, DNA methylation, and small non-coding RNAs. Infections and other environmental factors have profound effects on epigenetic modifications and trigger diseases. Despite growing evidences of literatures addressing the role of epigenetics in the field of medicine and biology, very little is known about the epigenetic pathways involved in dental pulp inflammation. This review summarized the current knowledge about epigenetic mechanisms during dental pulp inflammation. Progress in studies of epigenetic alterations during inflammatory response would provide opportunities for the development of efficient medications of epigenetic therapy for pulpitis.

Antibacterial efficacy of Azadirachta indica, Mimusops elengi and 2% CHX on multispecies dentinal biofilm

Aims:

To check the antimicrobial activity of Azadirachta indica (Neem), Mimusops elengi (Bakul), and Chlorhexidine gluconate (CHX) on multispecies biofilm of common endodontic pathogens such as Streptococcus mutans, Enterococcus faecalis, Staphylococcus aureus and Candida albicans.

Settings and Design:

In vitro dentin disinfection model used to check the antimicrobial efficacy of herbal extracts.

Materials and Methods:

The in vitro dentin disinfection model was used to check the antimicrobial activity of the methanolic extracts of the medicinal plants along with Chlorhexidine gluconate. The polymicrobial biofilm was allowed to grow on extracted teeth sections for a period of 21 days. Remaining microbial load in the form of CFU/ml after the antimicrobial treatment was tabulated, and data were statistically analyzed using ANOVA and Bonferroni post-hoc tests.

Statistical Analysis Used:

SPSS version 17, one-way ANOVA, Bonferroni post-hoc test.

Results:

Both the plant extracts showed considerable antimicrobial efficacy as compared to negative control. 2% CHX was the most effective antimicrobial agent having statistically significant difference against plant extracts and negative control (saline).

Conclusion:

The methanolic extract of A. Indica, M. elengi, and Chlorhexidine Gluconate has considerable antimicrobial activity against polymicrobial dentinal biofilm of S. mutans, E. faecalis, S. aureus and C. albicans.