CCL3 and CXCL12 production in vitro by dental pulp fibroblasts from permanent and deciduous teeth stimulated by Porphyromonas gingivalis LPS

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

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

Single-cell atlas of dental pulp stem cells exposed to the oral bacteria Porphyromonas gingivalis and Enterococcus faecalis

Introduction: Porphyromonas gingivalis and Enterococcus faecalis promote the development of pulpitis and periapical periodontitis. These bacteria are difficult to eliminate from the root canal systems, leading to persistent infection and poor treatment outcomes. We explored the response of human dental pulp stem cells (hDPSCs) to bacterial invasion and the mechanisms underlying the impact of residual bacteria on dental pulp regeneration. Methods: Single-cell sequencing was used to categorize the hDPSCs into clusters based on their response to P. gingivalis and E. faecalis. We depicted a single-cell transcriptome atlas of hDPSCs stimulated by P. gingivalis or E. faecalis. Results: The most differentially expressed genes in the Pg samples were THBS1, COL1A2, CRIM1, and STC1, which are related to matrix formation and mineralization, and HILPDA and PLIN2, which are related to the cellular response to hypoxia. A cell cluster characterized by high expression levels of THBS1 and PTGS2 was increased after P. gingivalis stimulation. Further signaling pathway analysis showed that hDPSCs prevented P. gingivalis infection by regulating the TGF-β/SMAD, NF-κB, and MAPK/ERK signaling pathways. Differentiation potency and pseudotime trajectory analyses showed that hDPSCs infected by P. gingivalis undergo multidirectional differentiation, particularly to the mineralization-related cell lineage. Furthermore, P. gingivalis can create a hypoxia environment to effect cell differentiation. The Ef samples were characterized by the expression of CCL2, which is related to leukocyte chemotaxis, and ACTA2, which is related to actin. There was an increased proportion of a cell cluster that was similar to myofibroblasts and exhibited significant ACTA2 expression. The presence of E. faecalis promoted the differentiation of hDPSCs into fibroblast-like cells, which highlights the role of fibroblast-like cells and myofibroblasts in tissue repair. Discussion: hDPSCs do not maintain their stem cell status in the presence of P. gingivalis and E. faecalis. They differentiate into mineralization-related cells in the presence of P. gingivalis and into fibroblast-like cells in the presence of E. faecalis. We identified the mechanism underlying the infection of hDPSCs by P. gingivalis and E. faecalis. Our results will improve understanding of the pathogenesis of pulpitis and periapical periodontitis. Furthermore, the presence of residual bacteria can have adverse effects on the outcomes of regenerative endodontic treatment.

Stimulation phosphatidylinositol 3-kinase/protein kinase B signaling by Porphyromonas gingivalis lipopolysacch aride mediates interleukin-6 and interleukin-8 mRNA/protein expression in pulpal inflammation

BACKGROUND/PURPOSE

The signaling mechanisms for Porphyromonas gingivalis lipopolysaccharide (PgLPS)-induced inflammation in human dental pulp cells are not fully clarified. This in vitro study aimed to evaluate the involvement of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway in PgLPS-induced pulpal inflammation.

METHODS

Human dental pulp cells (HDPCs) were challenged with PgLPS with or without pretreatment and coincubation with a PI3K/Akt inhibitor (LY294002). The gene or protein levels of PI3K, Akt, interleukin (IL)-6, IL-8, alkaline phosphatase (ALP), osteocalcin and osteonectin were analyzed by reverse transcription polymerase chain reaction (PCR), real-time PCR, western blotting, and immunofluorescent staining. In addition, an enzyme-linked immunosorbent assay was used to analyze IL-6 and IL-8 levels in culture medium.

RESULTS

In response to 5 μg/ml PgLPS, IL-6, IL-8, and PI3K, but not Akt mRNA expression of HDPCs, was upregulated. IL-6, IL-8, PI3K, and p-Akt protein levels were stimulated by 10-50 μg/ml of PgLPS in HDPCs. PgLPS also induced IL-6 and IL-8 secretion at concentrations higher than 5 μg/ml. Pretreatment and co-incubation by LY294002 attenuated PgLPS-induced IL-6 and IL-8 mRNA expression in HDPCs. The mRNA expression of ALP, but not osteocalcin and osteonectin, was inhibited by higher concentrations of PgLPS in HDPCs.

CONCLUSION

P. gingivalis contributes to pulpal inflammation in HDPCs by dysregulating PI3K/Akt signaling pathway to stimulate IL-6 and IL-8 mRNA/protein expression and secretion. These results are useful for understanding the pulpal inflammation and possible biomarkers of inflamed pulp diagnosis and treatment.

Inflammation down regulates stromal cell-derived factor 1α in the early phase of pulpitis

The key to prevent pulp necrosis in the early stage of pulpitis is to promote tissue repair, which begins with cell migration. Stromal cell-derived factor 1α (SDF-1α) has been proven to promote cell migration. Related research has so far concentrated on the biological effects of SDF-1α while its expression in pulpitis is still unclear. We investigated the effect of inflammation on SDF-1α in dental pulp and the underlying regulatory mechanisms. First, rat pulpitis models were established by exposing pulp. SDF-1α was decreased on the 3rd day but increased on the 7th day. Next, lipopolysaccharide from Porphyromonas gingivalis (Pg.LPS) was applied to dental pulp cells (DPCs). Within 24 h, SDF-1α decreased, but after 48 h, it steadily increased. Similarly, SDF-1α expression in human chronic pulpitis tissues was also increased. To investigate the effect of altered SDF-1α on DPC migration, cell supernatants collected following Pg.LPS treatment were utilized to stimulate DPCs, and the number of migrated cells was correlated with changes in SDF-1α secretion. Finally, we explored the regulatory mechanisms of SDF-1α down-regulation in the early phase of pulpitis. Within 24 h, JNK/c-Jun pathway was activated in DPC inflammation. When JNK pathway was suppressed, SDF-1α rose. Furthermore, tumor necrosis factor receptor 2 (TNFR2) and apoptosis signal-regulated kinase-interacting protein 1 (AIP1) were up-regulated. Knockdown of them abolished Pg.LPS-induced activation of JNK and c-Jun(Ser63) and significantly enhanced SDF-1α. Our findings indicated that in the early phase of pulpitis, inflammation suppressed SDF-1α by up-regulating TNFR2 and AIP1, which activated JNK/c-Jun(Ser63) pathway.

Role of Lipopolysaccharide, Derived from Various Bacterial Species, in Pulpitis—A Systematic Review

Lipopolysaccharide (LPS) is widely used for induction of inflammation in various human tissues, including dental pulp. The purpose of this study was to summarize current medical literature focusing on (1) cell types used by researchers to simulate dental pulp inflammation, (2) LPS variants utilized in experimental settings and how these choices affect the findings. Our study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We searched for studies reporting outcomes of lipopolysaccharide application on dental pulp cells in vitro using electronic databases: MEDLINE, Web of Science and Scopus. Having gathered data from 115 papers, we aimed to present all known effects LPS has on different cell types present in dental pulp. We focused on specific receptors and particles that are involved in molecular pathways. Our review provides an essential foundation for further research using in vitro models of pulpitis.

Molecular Response of Pulp Fibroblasts after Stimulation with Pulp Capping Materials

This in vitro study evaluated cell viability and metabolism, nitric oxide release and production of two chemokines and one cytokine by cultured human dental pulp fibroblasts (HDPF) in contact with two glass ionomer cements (Ketac Molar-KM and Vitrebond-VB), Single Bond (SB) and calcium hydroxide (Dycal-DY). Cultures of HDPF were established by means of an explant technique. The specimens were prepared under sterile conditions and in disks measuring 5 mm x 2 mm obtained from a prefabricated mold and placed on a permeable membrane to avoid direct contact with the cells. Cytotoxicity was assessed by Trypan Blue exclusion method and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Nitric oxide release in cell supernatant was detected by the Griess Method whereas stromal derived factor-1 alpha (SDF-1α or CXCL12), chemokine (C-X-C motif) ligand 8 [Interleukin 8 (IL-8 or CXCL8)] and interleukin-6 (IL-6) were detected by ELISA. RT-qPCR was employed for gene expression analysis. Statistical analyses were performed by One-way ANOVA followed by Tukey's post hoc test for materials independent of the time, and Two-way ANOVA followed by Bonferroni correction test for the comparisons between materials and experimental time (p<0.05). Cytotoxic tests showed significant differences only for DY. Protein levels and mRNA expression were significantly increased for IL-8 for both periods of time. IL-6 production increased when fibroblasts were stimulated by KM. SDF-1α protein production and mRNA expression were not affected by any of the materials. There was a decrease in nitrate/nitrite levels only for KM. Although DY caused intense cell death and did not stimulate the production of the inflammatory mediators evaluated in this work, it is known that this event seems to be fundamental for the process of repair of the pulp tissue and formation of mineralized barrier. KM and VB increased production of proteins related to the inflammatory process, thus favoring tissue repair. Therefore, although these glass ionomer cements did not lead to large cell death, they should be used with caution.

What is the response profile of deciduous pulp fibroblasts stimulated with E. coli LPS and E. faecalis LTA?

Background

Oral fibroblast immunological responses to bacterial stimuli are well known. However, there are few studies about pulp fibroblasts from deciduous teeth (HDPF) responses, which are important for the treatment of pulp infections in children. The aim of this study was to evaluate expression and production of inflammatory cytokines and chemokines by HDPF when challenged with bacterial antigens normally present in advanced caries lesions.

Methods

Triplicate HDPF from 4 children (n = 4; 2 boys and 2 girls) were cultured by explant technique and challenged or not with Escherichia coli lipopolysaccharide/1 μg/mL (EcLPS) or Enterococcus faecalis lipoteichoic acid/1 μg/mL (EfLTA) for 6 and 24 h. Most of published studies employed immortalized cells, i.e., without checking possible gender and genetic variables. mRNA expression and protein production were evaluated by RT-qPCR and ELISA MILLIPLEX®, respectively, for Interleukin (IL)-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-17, Chemokine C-C motif ligand 2/monocyte chemoattractant protein 1 (CCL2/MCP-1), Chemokine C-C motif ligand 3/macrophage inflammatory protein 1-alpha (CCL3/MIP1-α), Chemokine C-C motif ligand 5/ regulated on activation, normal T cell expressed and secreted (CCL5/RANTES), C-X-C motif chemokine 12/ stromal cell-derived factor 1 (CXCL12/SDF-1), Tumor Necrosis Factor-alpha (TNF-α), Interferon-gamma (IFN γ), Vascular Endothelial Growth Factor (VEGF), Colony stimulating factor 1 (CSF-1) and Macrophage colony-stimulating factor (M-CSF).

Results

EcLPS increased IL-1α, IL-1β, IL-8, CCL2, CCL5, TNF-α and CSF-1 mRNA and protein levels while EfLTA was only able to positively regulate gene expression and protein production of IL-8.

Conclusion

The results of the present study confirmed our hypothesis, since pulp fibroblasts from deciduous teeth are capable of increasing gene expression and protein production after being stimulated with EcLPS and EfLTA.

Dental Pulp Fibroblasts Response after Stimulation with HEMA and Adhesive System

This study evaluated in vitro cell viability and metabolism, nitric oxide release and production of chemokines by cultured human dental pulp fibroblasts (DPF) under contact with HEMA and Single Bond. Cultures of DPF were established by means of an explant technique. Once plated, cells were kept under contact with increasing concentrations of HEMA (10, 100 and 1000 nM) or Single Bond (SB) [10-fold serially diluted in culture medium (10-4, 10-3 and 10-2 v/v)] and also with polymerized SB components. Cytotoxicity was assessed by Trypan Blue exclusion method and MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Nitric oxide release on cell supernatant was detected by Griess Method whereas chemokines (CXCL12 and CXCL8) were detected by ELISA. RT-qPCR was employed for chemokines gene expression analysis. Cytotoxic tests showed significant differences for SB 10-2. None of the tested materials significantly altered NO levels. Protein levels of CXCL12 were significantly decreased only by HEMA. On the other hand, while CXCL12 mRNA remained unaltered, gene expression of CXCL8 had significant decrease with all materials, except for polymerized SB. In conclusion, Single Bond and HEMA at various concentrations, decreased expression and production of molecules involved in inflammatory processes and, therefore, the use of adhesive systems such as pulp capping materials must be viewed with caution due to its large cytotoxic effect when in close contact with the pulp.

[Vital pulp therapy of damaged dental pulp]

The development of an expert consensus on vital pulp therapy can provide practical guidance for the improvement of pulp damage care in China. Dental pulp disease is a major type of illness that adversely affects human oral health. Pulp capping and pulpotomy are currently the main methods for vital pulp therapy. Along with the development of minimal invasion cosmetic dentistry, using different treatment technologies and materials reasonably, preserving healthy tooth tissue, and extending tooth save time have become urgent problems that call for immediate solution in dental clinics. This paper summarizes the experiences and knowledge of endodontic experts. We develop a clinical path of vital pulp therapy for clinical work by utilizing the nature, approach, and degree of pulp damage as references, defense and self-repairing ability of pulp as guidance, and modern technologies of diagnosis and treatment as means.

Eugenol Toxicity in Human Dental Pulp Fibroblasts of Primary Teeth

OBJECTIVE

The aim of the study was to determine the eugenol concentrations at which toxicity occurs in human dental pulp fibroblasts of primary teeth.

STUDY DESIGN

Samples of primary dental pulp tissue were taken. Tissue samples were seeded by means of explant technique and used in the 4(th)-5th pass. Single Cell Gel Electrophoresis (Comet), phenazine MeThoSulfate (MTS), LIVE/DEAD Cell Viability/Toxicity and trypan blue assays for evaluation of the cytotoxicity of increasing concentrations of eugenol (0.06 to 810 μM) were performed.

RESULTS

The results of toxicity tests showed toxic effects on dental pulp fibroblasts, even at very low concentrations of eugenol (0.06 μM). Very low concentrations of eugenol produce high toxicity in human dental pulp fibroblasts.

CONCLUSIONS

All of the concentrations of eugenol that we evaluated produced high toxicity in human dental pulp fibroblasts of primary teeth.

Association of CXCL12 gene promoter methylation with periodontitis in patients with diabetes mellitus type 2

OBJECTIVES

CXCL12 is widely expressed, constitutive chemokine involved in tissue repair and regeneration, while the extent of its expression is important in various chronic inflammatory conditions. Involvement of DNA methylation in CXCL12 gene suppression (CXCL12) has been shown in malignancy and some autoimmune diseases. The aim of this study was to investigate whether the alterations in DNA methylation of CXCL12 are also involved in progression of periodontitis in combination with diabetes, as these chronic inflammatory conditions are strongly interrelated.

DESIGN

Study included 72 subjects divided in three groups: healthy control (C, n=21), periodontitis (P, n=29) and diabetes/periodontitis group (D/P, n=22). DNA extracted from epithelial cells obtained by sterile cotton swabs from buccal mucosa was subjected to methylation specific polymerase chain reaction (MSP) to obtain DNA methylation pattern of CXCL12 promoter.

RESULTS

CXCL12 promoter was predominantly unmethylated in all groups. However, increase in the frequency of the methylated form and increase in percent of methylation of CXCL12 promoter in periodontitis and diabetes/periodontitis group compared to control group were found, although without statistical significance. However, statistically significant increase in Tm of MSP products in diabetes/periodontitis group was observed. Correlation analysis revealed statistically significant relationship between the extent of DNA methylation of the CXCL12 promoter and periodontal parameters, as well as between DNA methylation of CXCL12 and glycosylated hemoglobin.

CONCLUSION

Presented results suggest that chronic inflammation contributes to the change of CXCL12 DNA methylation in buccal cells and that DNA methylation profile of CXCL12 promoter plays important role in development and progression of periodontal disease.

Leukocyte presence does not increase microbicidal activity of Platelet-rich Plasma in vitro

Background

Human platelets are a rich reservoir of molecules that promote regenerative processes and microbicidal activity. This activity might be increased by concentration in platelet-rich plasma (PRP) products and modulated by the presence of leukocytes. Despite extensive use in clinical procedures, only few studies have investigated PRP’s real microbicidal potential. Therefore, this study aimed at comparing the in vitro microbicidal activity of platelets and leukocyte-enriched PRP (L-PRP) to pure platelet-rich plasma (P-PRP) and the contribution of leukocytes to microbicidal properties.

Antimicrobial effects of P- and L-PRP were tested against Escherichia Coli, Staphylococcus Aureus, Klebsiella Pneumoniae, Pseudomonas Aeruginosa and Enterococcus Faecalis. Furthermore, L-PRP was frozen (L-PRP cryo) to assess whether the preparation maintained in vitro characteristics. Microbicidal proteins released by the three preparations were also evaluated.

Results

L-PRP, L-PRP cryo and P-PRP generally induced comparable bacterial growth inhibition for up to 4 h’ incubation, range 1–4 log. MIP-1α, RANTES, GRO-α, IL-8, NAP-2, SDF-1α and IL-6 showed strong microbicidal potential.

Conclusions

We found in vitro antibacterial activity of L-PRP and P-PRP and the possibility to cryopreserve L-PRP, without important changes to its effectiveness; similar microbicidal activity between preparations containing or not leukocytes; and the contribution of three new molecules (NAP-2, SDF-1α and IL-6).

MicroRNA-146a and microRNA-155 show tissue-dependent expression in dental pulp, gingival and periodontal ligament fibroblasts in vitro

MicroRNAs (miRNAs) are small non-coding RNAs showing a tissue-specific expression pattern, and whose function is to suppress protein synthesis. In this study, we hypothesized that expression of miRNAs would differ among fibroblasts from dental pulp (DPF), gingiva (GF) and periodontal ligament (PLF) in vitro. Once established by an explant technique, DPF, GF and PLF were collected for RNA isolation and subjected to a miRNA microarray. Next, cells were stimulated with E. coli lipopolysaccharide (LPS) for 24 h and then collected for RNA isolation. Expression of miR-146a and miR-155 was investigated by qPCR. Microarray screening revealed several miRNAs that showed specifically high expression in at least one of the fibroblast subtypes. These molecules are potentially involved in the regulation of extracellular matrix turnover and production of inflammatory mediators. Microarray analysis showed that both miR-146a and miR-155 were among the miRNAs expressed exclusively in GF. qPCR demonstrated significant upregulation of miR-146a only in GF after LPS stimulation, whereas basal expression of miR-155 was higher in GF than in the other cell subtypes. LPS downregulated the expression of miR-155 only in GF. Our results suggest that the expression and regulation of miR-146a and miR-155 are more pronounced in GF than in DPF and PLF.

In vitro regulation of CCL3 and CXCL12 by bacterial by-products is dependent on site of origin of human oral fibroblasts

INTRODUCTION

Production of chemokines by tissue resident cells is one of the main mechanisms involved in the inflammatory infiltrate formation during inflammation. The specific ability of fibroblasts from different oral tissues such as gingiva, periodontal ligament, and dental pulp from permanent and deciduous teeth in producing the chemokines CCL3 and CXCL12 under stimulation by bacterial products commonly found in endodontic infections was investigated.

METHODS

Cultures of fibroblasts from gingiva and periodontal ligament as well as from dental pulp from permanent and deciduous teeth were established by using an explant technique and stimulated with increasing concentrations of Escherichia coli lipopolysaccharide (EcLPS) and Enterococcus faecalis lipoteichoic acid (EfLTA) for 1, 6, and 24 hours. Supernatants were tested for CCL3 and CXCL12 by enzyme-linked immunosorbent assay.

RESULTS

In general, CCL3 production was induced by EcLPS in the 4 fibroblast subtypes and by EfLTA in fibroblasts from gingiva and periodontal ligament. Constitutive CXCL12 synthesis decreased in all fibroblast subtypes especially under stimulation with EcLPS. Fibroblast from permanent deciduous teeth was the cell type presenting the most expressive reduction in CXCL12 release by both stimuli. On the basis of computational matching of CXCL12 mRNA with the microRNAs miR-141 and miR-200a, their expression was also investigated. Although detected in the fibroblasts, these molecules remained unaltered by bacterial by-product stimulation.

CONCLUSIONS

EcLPS and EfLTA induced the production of CCL3 and unbalanced the synthesis of CXCL12 in a manner dependent on the specific tissue origin of fibroblasts.