Immune responses of human dental pulp stem cells in lipopolysaccharide-induced microenvironment

Dental Stem Cells and Lipopolysaccharides: A Concise Review

Dental tissue stem cells (DTSCs) are well known for their multipotent capacity and regenerative potential. They also play an important role in the immune response of inflammatory processes derived from caries lesions, periodontitis, and gingivitis. These oral diseases are triggered by toxins known as lipopolysaccharides (LPS) produced by gram-negative bacteria. LPS present molecular patterns associated with pathogens and are recognized by Toll-like receptors (TLRs) in dental stem cells. In this review, we describe the effect of LPS on the biological behavior of DTSCs. We also focus on the molecular sensors, signaling pathways, and emerging players participating in the interaction of DTSCs with lipopolysaccharides. Although the scientific advances generated provide an understanding of the immunomodulatory potential of DTSCs, there are still new reflections to explore with regard to their clinical application in the treatment of oral inflammatory diseases.

Mesenchymal Stem Cells Attenuates Hirschsprung Disease-Associated Enterocolitis by Reducing M1 Macrophages Infiltration via COX-2 Dependewhant Mechanism

OBJECTIVE AND DESIGN

Hirschsprung disease-associated enterocolitis (HAEC) is a common life-threatening complication of Hirschsprung disease (HSCR). We aimed to investigate the effectiveness, long-term safety and the underlying mechanisms of Mesenchymal stem cells (MSCs) based therapy for HAEC.

MATERIAL OR SUBJECTS

Specimens from HSCR and HAEC patients were used to assess the inflammatory condition. Ednrb knock-out mice was used as HAEC model. MSCs was intraperitoneally transplanted into HAEC mice. The therapy effects, long-term outcome, safety and toxicity and the mechanism of MSCs on the treatment of HAEC were explored in vivo and in vitro.

RESULTS

Intestinal M1 macrophages infiltration and severe inflammation condition were observed in HAEC. After the injection of MSCs, HAEC mice showed significant amelioration of the inflammatory injury and inhibition of M1 macrophages infiltration. The expression levels of pro-inflammatory cytokines (TNF-α and IFN-γ) were decreased and anti-inflammatory cytokines (IL-10 and TGF-β) were increased. In addition, we found that effective MSCs homing to the inflamed colon tissue occurred without long-term toxicity response. However, COX-2 inhibitor could diminish the therapeutic effects of MSCs. Using MSCs and macrophages co-culture system, we identified that MSCs could alleviate HAEC by inhibiting M1 macrophages activation through COX-2-dependent MAPK/ERK signaling pathway.

CONCLUSIONS

MSCs ameliorate HAEC by reducing M1 macrophages polarization via COX-2 mediated MAPK/ERK signaling pathway, thus providing novel insights and potentially promising strategy for the treatment or prevention of HAEC.

Ginsenoside Rb1 alleviates lipopolysaccharide-induced inflammation in human dental pulp cells via the PI3K/Akt, NF-κB, and MAPK signalling pathways

AIM

Among numerous constituents of Panax ginseng, a constituent named Ginsenoside Rb1 (G-Rb1) has been studied to diminish inflammation associated with diseases. This study investigated the anti-inflammatory properties of G-Rb1 on human dental pulp cells (hDPCs) exposed to lipopolysaccharide (LPS) and aimed to determine the underlying molecular mechanisms.

METHODOLOGY

The KEGG pathway analysis was performed after RNA sequencing in G-Rb1- and LPS-treated hDPCs. Reverse-transcription polymerase chain reaction (RT-PCR) and western blot analysis were used for the assessment of cell adhesion molecules and inflammatory cytokines. Statistical analysis was performed with one-way ANOVA and the Student-Newman-Keuls test.

RESULTS

G-Rb1 did not exhibit any cytotoxicity within the range of concentrations tested. However, it affected the levels of TNF-α, IL-6 and IL-8, as these showed reduced levels with exposure to LPS. Additionally, less mRNA and protein expressions of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) were shown. With the presence of G-Rb1, decreased levels of PI3K/Akt, phosphorylated IκBα and p65 were also observed. Furthermore, phosphorylated ERK and JNK by LPS were diminished within 15, 30 and 60 min of G-Rb1 exposure; however, the expression of non-phosphorylated ERK and JNK remained unchanged.

CONCLUSIONS

G-Rb1 suppressed the LPS-induced increase of cell adhesion molecules and inflammatory cytokines, while also inhibiting PI3K/Akt, phosphorylation of NF-κB transcription factors, ERK and JNK of MAPK signalling in hDPCs.

Involvement of the visfatin/toll-like receptor 4 signaling axis in human dental pulp cell senescence: Protection via toll-like receptor 4 blockade

Background

/purpose: Dental pulp plays an important role in the maintenance of tooth homeostasis and repair. The aging of dental pulp affects the functional life of the tooth owing to the senescence of dental pulp cells. Toll-like receptor 4 (TLR4) is involved in regulating cellular senescence in dental pulp. We have recently demonstrated that visfatin induces the senescence of human dental pulp cells (hDPCs). Here, we explored the association of TLR4 with visfatin signaling in cellular senescence in hDPCs.

Materials and methods

mRNA levels were determined using reverse transcription polymerase chain reaction (PCR) and quantitative real time-PCR. Protein levels were determined using immunofluorescence staining and Western blot analysis. Gene silencing was performed using small interfering RNA. The degree of cellular senescence was measured by senescence-associated-β-galactosidase (SA-β-gal) staining. Oxidative stress was determined by measurement of NADP/NADPH levels and intracellular reactive oxygen species (ROS) levels.

Results

Neutralizing anti-TLR4 antibodies or TLR4 inhibitor markedly blocked visfatin-induced hDPCs senescence, as revealed by an increase in the number of SA-β-gal-positive hDPCs and upregulation of p21 and p53 proteins. Moreover, visfatin-induced senescence was associated with excessive ROS production; NADPH consumption; telomere DNA damage induction; interleukin (IL)-1β, IL-6, IL-8, cyclooxygenase-2, and tumor necrosis factor-α upregulation; and nuclear factor-κB and mitogen-activated protein kinase activation. All of these alterations were attenuated by TLR4 blockade.

Conclusion

Our findings indicate that TLR4 plays an important role in visfatin-induced senescence of hDPCs and suggest that the visfatin/TLR4 signaling axis can be a novel therapeutic target for the treatment of inflammaging-related diseases, including pulpitis.

Determination of the optimal concentration and duration of C5aR antagonist application in an inflammatory model of human dental pulp cells

Deep tooth decay approaching the pulp may develop into pulpitis; to prevent this, pulp cells need to balance the rapid immune response to avoid rapid swelling of the pulp. Current treatment of deep decay that approaches the pulp involves the application of drugs that induce low-level inflammation in the dental pulp to promote its repair, but this treatment is sometimes insufficient. However, the unsuccessful treatment often resulted in pulpitis. The C5a-C5aR is the initial stage of the immune cascade response. Blocking the binding of C5a-C5aR can slow the immune response in the narrow pulp cavity, so that dental pulp cells have enough time to proliferate, migrate, and differentiate. In this study, we compared lipoteichoic acid (LTA) and lipopolysaccharides (LPS) at different concentrations and time points and used the C5aR antagonist W54011 to block the C5a-C5aR axis. The blocking effect was detected by analyzing the expression of C5a, C5aR, interleukin (IL)-6, and Toll-like receptors 2 and 4 (TLR-2, 4). Next, we determined the optimal concentration and duration of LTA and LPS treatment in combination with W54011. Based on our results, we selected 1.0 μg·mL-1 LPS treatment for 48 h to generate an inflammatory model of human dental pulp cells. We then regrouped the cells and conducted expression analyses to monitor the expression of C5a, C5aR, IL-6, and TLR-4 at the protein and mRNA levels. LPS stimulation for 48 h and treatment with W54011 for 48 h effectively inhibited inflammation and did not affect C5a expression. This study provides a basis for follow-up studies of W54011 in dental pulp cells.

The Role and Involvement of Stem Cells in Periodontology

Periodontitis is a widespread inflammatory condition, characterized by a progressive deterioration of the supporting structures of the teeth. Due to the complexity of periodontal tissue and the surrounding inflammatory microenvironment, the repair of lesions at this level represents a continuous challenge. The regeneration of periodontal tissues is considered a promising strategy. Stem cells have remarkable properties, such as immunomodulatory potential, proliferation, migration, and multilineage differentiation. Thus, they can be used to repair tissue damage and reduce inflammation, potentially leading to periodontal regeneration. Among the stem cells used for periodontal regeneration, we studied dental mesenchymal stem cells (DMSCs), non-dental stem cells, and induced pluripotent stem cells (IPSCs). Although these cells have well documented important physiological characteristics, their use in contemporary practice to repair the affected periodontium is still a challenge.

Differential Effects of Escherichia coli- Versus Porphyromonas gingivalis-derived Lipopolysaccharides on Dental Pulp Stem Cell Differentiation in Scaffold-free Engineered Tissues

INTRODUCTION

To leverage the therapeutic capabilities of dental pulp stem cells (DPSCs) for regenerative endodontic applications, a better understanding of their innate defense and reparative processes is needed. Lipopolysaccharide (LPS) is a major virulent factor of gram-negative bacteria and contributor to endodontic infections. We have developed 3-dimensional scaffold-free DPSC tissues that self-organize into dentin-pulp organoids comprising a mineralized dentin-like tissue on the periphery and an unmineralized pulp-like core. In this study, scaffold-free DPSC constructs were used as controllable experimental models to study the DPSC response to bacterial challenge.

METHODS

Scaffold-free constructs were engineered using DPSCs isolated from human third molars. To simulate bacterial exposure, DPSC constructs were exposed to either Porphyromonas gingivalis-derived LPS or Escherichia coli-derived LPS. The effects of LPS on DPSC differentiation, proliferation, and apoptosis were evaluated.

RESULTS

Engineered tissues lacking LPS treatment self-organized into dentin-pulp organoids. LPS treatment did not negatively affect DPSC proliferation or apoptosis in the engineered tissues. Both E. coli LPS and P. gingivalis LPS inhibited the up-regulation of RUNX2 messenger RNA expression and reduced the expression of the odontoblast-associated proteins (P < .05), suggesting that LPS is inhibiting odontoblastic differentiation. However, only E. coli LPS treatment significantly reduced mineral deposition in the DPSC (P < .05) constructs, indicating that E. coli LPS but not P. gingivalis LPS reduced functional differentiation of DPSCs and prevented DPSCs from self-organizing into a dentin-pulp complex-like structure.

CONCLUSIONS

This study establishes scaffold-free DPSC constructs as models of oral disease. Furthermore, it emphasizes the diversity of LPS derived from different bacterial species and highlights the necessity of using LPS derived from clinically relevant bacteria in basic science investigations.

Exposure to lipopolysaccharide and calcium silicate-based materials affects the behavior of dental pulp cells

This study assessed the cell viability, cytokine production, and mineralization potential of human dental pulp cells (hDPCs) after exposure to lipopolysaccharide (LPS) and application of calcium silicate-based materials (CSBM). Characterization of the CSBM was performed by infrared spectroscopy (n = 3). Extracts of Bio-C Repair, Biodentine, Cimmo HD, and MTA Repair HP were prepared and diluted (1:1, 1:4, and 1:16). Culture of hDPCs was established and treated or not with 1 µg/mL of LPS from Escherichia coli for 7 days. MTT assay was used to assess cell viability at 24, 48, and 72 h (n = 6). Alkaline phosphatase (ALP) activity was assayed on day 7 (n = 4). Il-10 and TNF-α were quantified by ELISA at 24 h (n = 6). Data were analyzed by ANOVA and Tukey's test (α = 0.05). Cell viability of LPS-activated hPDCs was higher than untreated control in 48 and 72 h (p < 0.05). Differences between non-treated and LPS-activated hPDCs were observed for Biodentine and Cimmo HP (p < 0.05). The CSBM influenced the cell viability (p < 0.05). ALP activity was higher in LPS-activated hDPCs (p < 0.05). No changes in the concentration of TNF-α were observed between groups (p > 0.05). The CSBM increased the Il-10 production (p < 0.05). LPS-activated hDPCs presented increased cell viability and ALP activity. The CSBM showed mild toxicity and was able to enhance the cell viability and mineralization potential of untreated and LPS-activated hDPCs. The CSBM also induced anti-inflammatory mechanisms without compromising pro-inflammatory ones.

Anti-Inflammatory and Mineralization Effects of an ASP/PLGA-ASP/ACP/PLLA-PLGA Composite Membrane as a Dental Pulp Capping Agent

Dental pulp is essential for the development and long-term preservation of teeth. Dental trauma and caries often lead to pulp inflammation. Vital pulp therapy using dental pulp-capping materials is an approach to preserving the vitality of injured dental pulp. Most pulp-capping materials used in clinics have good biocompatibility to promote mineralization, but their anti-inflammatory effect is weak. Therefore, the failure rate will increase when dental pulp inflammation is severe. The present study developed an amorphous calcium phosphate/poly (L-lactic acid)-poly (lactic-co-glycolic acid) membrane compounded with aspirin (hereafter known as ASP/PLGA-ASP/ACP/PLLA-PLGA). The composite membrane, used as a pulp-capping material, effectively achieved the rapid release of high concentrations of the anti-inflammatory drug aspirin during the early stages as well as the long-term release of low concentrations of aspirin and calcium/phosphorus ions during the later stages, which could repair inflamed dental pulp and promote mineralization. Meanwhile, the composite membrane promoted the proliferation of inflamed dental pulp stem cells, downregulated the expression of inflammatory markers, upregulated the expression of mineralization-related markers, and induced the formation of stronger reparative dentin in the rat pulpitis model. These findings indicate that this material may be suitable for use as a pulp-capping material in clinical applications.

Different expression patterns of inflammatory cytokines induced by lipopolysaccharides from Escherichia coli or Porphyromonas gingivalis in human dental pulp stem cells

Background

Lipopolysaccharide (LPS) is one of the leading causes of pulpitis. The differences in establishing an in vitro pulpitis model by using different lipopolysaccharides (LPSs) are unknown. This study aimed to determine the discrepancy in the ability to induce the expression of inflammatory cytokines and the underlying mechanism between Escherichia coli (E. coli) and Porphyromonas gingivalis (P. gingivalis) LPSs in human dental pulp stem cells (hDPSCs).

Material and methods

Quantitative real-time polymerase chain reaction (QRT-PCR) was used to evaluate the mRNA levels of inflammatory cytokines including IL-6, IL-8, COX-2, IL-1β, and TNF-α expressed by hDPSCs at each time point. ELISA was used to assess the interleukin-6 (IL-6) protein level. The role of toll-like receptors (TLR)2 and TLR4 in the inflammatory response in hDPSCs initiated by LPSs was assessed by QRT-PCR and flow cytometry.

Results

The E. coli LPS significantly enhanced the mRNA expression of inflammatory cytokines and the production of the IL-6 protein (p < 0.05) in hDPSCs. The peaks of all observed inflammation mediators’ expression in hDPSCs were reached 3–12 h after stimulation by 1 μg/mL E. coli LPS. E. coli LPS enhanced the TLR4 expression (p < 0.05) but not TLR2 in hDPSCs, whereas P. gingivalis LPS did not affect TLR2 or TLR4 expression in hDPSCs. The TLR4 inhibitor pretreatment significantly inhibited the gene expression of inflammatory cytokines upregulated by E. coli LPS (p < 0.05).

Conclusion

Under the condition of this study, E. coli LPS but not P. gingivalis LPS is effective in promoting the expression of inflammatory cytokines by hDPSCs. E. coli LPS increases the TLR4 expression in hDPSCs. P. gingivalis LPS has no effect on TLR2 or TLR4 expression in hDPSCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-022-02161-x.

Anti-Inflammatory and Repairing Effects of Mesoporous Silica-Loaded Metronidazole Composite Hydrogel on Human Dental Pulp Cells

In order to test an effective biopolymer scaffold in promoting the growth of human dental pulp stem cells (HDPSCs), mesoporous silica @ hydrogel (MSN@Gel) nanocomposites are invented as a new type of biopolymer scaffold for HDPSCs proliferation in this paper. The expression levels of alkaline phosphatase (ALP), dentin matrix protein 1 (DMP1), and dentin sialophosphoprotein (DSPP) are significantly increased in the MSN@Gel group so as to better repair damaged dentin. In order to inhibit the proliferation of bacteria in the dental pulp, metronidazole (MTR) is loaded into MSN. The study found that MSN could effectively prolong the half-life of MTR by 1.75 times, and the viability of HDPSCs could be better maintained in the MSN-MTR@Gel group so as to better promote its proliferation to repair pulpitis. However, with the increase of the MTR concentration, its proliferation effect on HDPSCs decreased gradually, and the proliferation effect is the best in 10 μmol/L. Therefore, the MSN-MTR@Gel scaffold is expected to become an effective method for pulpitis therapy in the future.

Therapeutic Potential of Synthetic Human β-Defensin 1 Short Motif Pep-B on Lipopolysaccharide-Stimulated Human Dental Pulp Stem Cells

Dental pulp inflammation is a widespread public problem usually caused by caries or trauma. Alleviating inflammation is critical to inflamed pulp repair. Human β-defensin 1 short motif Pep-B is a cationic peptide that has anti-inflammatory, antibacterial, and immunoregulation properties, but its repair effect on human dental pulp stem cells (hDPSCs) under inflammation remains unclear. In this study, we aimed to investigate anti-inflammatory function of Pep-B and explore its therapeutic potential in lipopolysaccharide-(LPS-) induced hDPSCs. CCK-8 assay and transwell assay evaluated effects of Pep-B on hDPSC proliferation and chemotaxis. Inflammatory response in hDPSCs was induced by LPS; after Pep-B application, lactate dehydrogenase release, intracellular ROS, inflammatory factor genes expression and possible signaling pathway were measured. Then, osteo-/odontoblast differentiation effect of Pep-B on LPS-induced hDPSCs was detected. The results showed that Pep-B promoted hDPSC proliferation and reduced LPS-induced proinflammatory marker expression, and western blot result indicated that Pep-B inhibited inflammatory activation mediated by NF-κB and MAPK pathways. Pep-B also enhanced the expression of the osteo-/odontogenic genes and proteins, alkaline phosphatase activity, and nodule mineralization in LPS-stimulated hDPSCs. These findings indicate that Pep-B has anti-inflammatory activity and promote osteo-/odontoblastic differentiation in LPS-induced inflammatory environment and may have a potential role of hDPSCs for repair and regeneration.

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.

The Antimicrobial, Antioxidative, and Anti-Inflammatory Effects of Polycaprolactone/Gelatin Scaffolds Containing Chrysin for Regenerative Endodontic Purposes

The appropriate endodontic material should eliminate the infection and inflammation to provide a situation for regeneration and healing of pulp tissue besides biomineralization. Chrysin is one of the active ingredients of plant flavonoids, which has significant anti-inflammatory and antimicrobial properties. In the present study, this natural substance was evaluated for antioxidant, anti-inflammatory, and mineralization properties on dental pulp stem cells (DPSCs). SEM, FTIR, and TGA tests were used to determine the successful synthesize of chrysin-loaded scaffolds. The antimicrobial effects of the synthesized scaffold against Acinetobacter baumannii, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis were assessed by the agar diffusion test and live/dead assay. The proliferation of DPSCs on these scaffolds was determined by the MTT assay, DAPI staining, and DNA extraction. Moreover, the antioxidant and anti-inflammation activity of chrysin-loaded scaffolds on inflamed DPSCs was evaluated. Alkaline phosphatase activity and Alizarin Red S Stain tests were done to evaluate the mineralization of DPSCs seeded on these scaffolds. The chrysin-loaded scaffolds reported antimicrobial effects against evaluated bacterial strains. The proliferation of DPSCs seeded on these scaffolds was increased significantly (p < 0.05). The TNFα and DCF levels in inflamed DPSCs showed a significant decrease in the presence of chrysin-loaded scaffolds (p < 0.05). The ALP activity and formation of mineralized nodules of DPSCs on these scaffolds were significantly increased compared with the control group (p < 0.05). These results indicated that chrysin as an ancient therapeutic agent can accelerate the healing and regeneration of damaged pulp tissue, and this active ingredient can be a potential natural substance for regenerative endodontic procedures.

Multidifferentiation potential of dental-derived stem cells

Tooth-related diseases and tooth loss are widespread and are a major public health issue. The loss of teeth can affect chewing, speech, appearance and even psychology. Therefore, the science of tooth regeneration has emerged, and attention has focused on tooth regeneration based on the principles of tooth development and stem cells combined with tissue engineering technology. As undifferentiated stem cells in normal tooth tissues, dental mesenchymal stem cells (DMSCs), which are a desirable source of autologous stem cells, play a significant role in tooth regeneration. Researchers hope to reconstruct the complete tooth tissues with normal functions and vascularization by utilizing the odontogenic differentiation potential of DMSCs. Moreover, DMSCs also have the ability to differentiate towards cells of other tissue types due to their multipotency. This review focuses on the multipotential capacity of DMSCs to differentiate into various tissues, such as bone, cartilage, tendon, vessels, neural tissues, muscle-like tissues, hepatic-like tissues, eye tissues and glands and the influence of various regulatory factors, such as non-coding RNAs, signaling pathways, inflammation, aging and exosomes, on the odontogenic/osteogenic differentiation of DMSCs in tooth regeneration. The application of DMSCs in regenerative medicine and tissue engineering will be improved if the differentiation characteristics of DMSCs can be fully utilized, and the factors that regulate their differentiation can be well controlled.

4-Methylumbelliferone promotes the migration and odontogenetic differentiation of human dental pulp stem cells exposed to lipopolysaccharide in vitro

Hyaluronic acid (HA), a major component of the extracellular matrix, is essential to inflammatory regulation. 4-Methylumbelliferone (4-mu), as the specific inhibitor of HA synthesis, is an anti-inflammatory in multiple systems. However, there have been no studies, to our knowledge, regarding 4-mu treatment in pulp inflammation. Therefore, the purpose of this study was to investigate the effects of 4-mu on biological behaviors in human dental pulp stem cells (hDPSCs) exposed to lipopolysaccharide (LPS) in vitro. hDPSCs were exposed to LPS to construct the inflammation model in vitro. Immunocytochemistry, quantitative polymerase chain reaction, western blotting, Cell Counting Kit-8, scratch/Transwell assay, and alizarin red staining/alkaline phosphatase staining were selected to explore the effect of 4-mu on the expression of inflammatory factors, cell proliferation, cell migration, and the odontogenic differentiation ability of hDPSCs. LPS stimulated hDPSCs to highly express the related inflammatory factors and CD44 (the major HA receptor), which were all inhibited by 0.1 mM of 4-mu. In addition, the cell proliferation ability of hDPSCs was suppressed by 4-mu, while cell migration and odontogenic differentiation abilities were significantly improved under inflammation. In conclusion, 4-mu suppressed inflammatory cytokines in inflamed hDPSCs and had a positive effect on the migration and odontogenic differentiation of hDPSCs.

The Role of Small Extracellular Vesicles Derived from Lipopolysaccharide-preconditioned Human Dental Pulp Stem Cells in Dental Pulp Regeneration

INTRODUCTION

Regenerative endodontics has created a desirable shift in the treatment paradigm despite current limitations of regenerative outcomes. Mesenchymal stem cells (MSCs) facilitate tissue regeneration and repair in a mild inflammatory environment. Small extracellular vesicles (sEVs) derived from MSCs play an imperative role in the paracrine modulation of regenerative responses modulated by MSCs. However, it remains unknown whether MSCs enhance dental pulp regeneration or whether this enhancement is mediated by sEVs in a mild inflammatory environment. The present study aimed to elucidate the effects of sEVs originated from lipopolysaccharide (LPS)-preconditioned human dental pulp stem cells (hDPSCs) on dental pulp regeneration.

METHODS

All sEVs were isolated from hDPSCs cultured with or without LPS (ie, N-sEVs and L-sEVs, respectively). The effect of N-sEVs and L-sEVs on proliferation, migration, angiogenesis, and differentiation of rat bone marrow MSCs was identified in vitro. Moreover, N-sEVs or L-sEVs were implanted into rat pulpless root canal models, and the regenerated tissue in root canals was assessed via hematoxylin-eosin staining, Masson staining, and immunohistochemistry after 30 days of transplantation.

RESULTS

Both N-sEVs and L-sEVs could modulate BMSC proliferation, migration, angiogenesis, and differentiation. Both kinds of sEVs enhanced the structure of the regenerated tissue closer to that of a normal dental pulp in vivo. L-sEVs had a more significant effect than N-sEVs.

CONCLUSIONS

sEVs released by hDPSCs in a mild inflammatory microenvironment are capable of facilitating the regeneration of dental pulp through functional healing instead of scar healing, which has potential applications in regenerative endodontics.

Regeneration of pulp-dentine complex-like tissue in a rat experimental model under an inflammatory microenvironment using high phosphorous-containing bioactive glasses

AIM

To investigate the effects of a bioactive glass with a high proportion of phosphorus (BG-hP) on the repair and regeneration of dental pulps in rats under an inflammatory microenvironment.

METHODOLOGY

Human dental pulp cells (hDPCs) stimulated with 1 μg mL^-1 lipopolysaccharide (LPS) were co-cultured with 0.1 mg mL^-1 BG-hP. Cell proliferation was detected by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide (MTT) assays. The expression of inflammation-related genes and odontogenic differentiation-related genes was determined by real-time PCR. Alizarin red staining was used to detect the formation of mineralized nodules. Coronal pulp tissues of rat molars were stimulated with 10 mg mL^-1 LPS and then treated with BG-hP. The expression of inflammation-related genes in pulp tissue was determined by real-time PCR. Haematoxylin-eosin staining and Masson staining were performed to observe the inflammatory response and mineralized matrix formation, after subcutaneous implantation in nude mice, at 3 days and 4 weeks, respectively. Analysis of variance was performed to measure statistical significance (P < 0.05).

RESULTS

BG-hP significantly reduced expression of interleukin-6 (IL-6) and IL-8 and significantly upregulated the expression of IL-10, IL-4 and transforming growth factor-β1 of the LPS-stimulated hDPCs (P < 0.05). BG-hP significantly inhibited the initial cell number (P < 0.05), but the hDPCs stimulated by LPS and co-cultured with BG-hP maintained the same proliferation rate as the untreated hDPCs. BG-hP significantly promoted the expression of dentine matrix protein-1 and dentine sialophosphoprotein and the mineralization capacity of the LPS-stimulated hDPCs (P < 0.05). Furthermore, BG-hP significantly downregulated the expression of Il-6 and reduced the inflammatory response of the LPS-stimulated pulp tissue 3 days after subcutaneous implantation (P < 0.05). Four weeks after subcutaneous implantation, BG-hP induced the formation of a continuous layer of dentine-like structure with dentinal tubules and polarizing odontoblast-like cells aligned along it in the LPS-stimulated pulp tissue.

CONCLUSION

The present preliminarily results demonstrated that the bioactive glass with a high proportion of phosphorus inhibited the inflammatory response and promoted the formation of a pulp-dentine complex in a rat experimental model. This study provides a foundation for the construction of materials with the dual functions of exerting anti-inflammatory effects and promoting tissue regeneration to meet the needs of dental pulp repair and regeneration.

Alterations of mitochondrial dynamics, inflammation and mineralization potential of lipopolysaccharide-induced human dental pulp cells after exposure to N-acetyl cysteine, Biodentine or ProRoot MTA

AIM

To investigate the effects of N-acetyl cysteine (NAC), Biodentine, ProRoot MTA and their combinations, on cell viability, mitochondrial reactive oxygen species (mtROS) production, mineralization and on the expression of genes related to inflammatory cytokine production, mitochondrial dynamics and cell apoptosis of lipopolysaccharide (LPS)-induced human dental pulp cells (hDPCs).

METHODOLOGY

Isolated hDPCs were exposed to 20 μg mL^-1 of Escherichia coli (E. coli) LPS for 24 h, before the experiment, except for the control group. Eight experimental groups were assigned: (i) control (hDPCs cultured in regular medium), (ii) +LPS (hDPCs cultured in LPS medium throughout the experiment), (iii) -LPS/Media, (iv) -LPS/BD, (v) -LPS/MTA, (vi) -LPS/NAC, (vii) -LPS/BD + NAC and (viii) -LPS/MTA + NAC. Cell viability was measured using Alamar blue assay at 24 and 48 h. Production of mtROS was evaluated at 6 and 24 h by MitoSOX Red and MitoTracker Green. The expressions of IL-6, TNF-α, Bcl-2, Bax, Mfn-2 and Drp-1 genes were investigated at 6 h using reverse transcriptase-polymerase chain reaction (RT-PCR). For differentiation potential, cells were cultured in the osteogenic differentiation media and stained using Alizarin red assay at 14 and 21 days. The Kruskal-Wallis test, Mann-Whitney U test and one-way anova were performed for statistical analysis.

RESULTS

NAC was associated with significantly greater LPS-induced hDPC viability (P < 0.05). Both Biodentine and MTA extracts promoted cell survival, whereas the combination of NAC to these material extracts significantly increased the number of viable cells at 24 h (P < 0.05). Biodentine, MTA or NAC did not alter the mtROS level (P > 0.05). NAC supplementation to the MTA extract significantly reduced the level of IL-6 and TNF-α expression (P < 0.05). Regarding mitochondrial dynamics, the use of NAC alone promoted significant Mfn-2/Drp-1 expression (P < 0.05). Most of the groups exhibited a level of Bcl-2/Bax gene expression similar to that of the control group. The increases in mineralization productions were observed in most of the groups, except the LPS group (P < 0.05).

CONCLUSIONS

The antioxidant effect of NAC was not evident under the LPS-induced condition in DPC in vitro. NAC combined either with Biodentine or MTA improved LPS-induced hDPCs survival at 24 h. The combination of NAC with MTA promoted mineralization.

Human dental pulp stem cells: A sanctuary for relapsing Bartonella quintana

Bartonella quintana is a facultative intracellular bacterium responsible for relapsing fever, an example of non-sterilizing immunity. The cellular sanctuary of B. quintana in-between febrile relapses remains unknown but repeated detection of B. quintana in dental pulp specimens suggested long-term half-life dental pulp stem cells (DPSCs) as candidates. As the capacity of DPSCs to internalize microscopic particles was unknown, we confirmed that DPSCs internalized B. quintana bacteria: Gimenez staining and fluorescence microscopy localized B. quintana bacteria inside DPSCs and this internalization did not affect the cellular multiplication of DPSCs during a one-month follow-up despite the increase in the bacterial load. B. quintana-infected DPSCs did not produce Tumor Necrosis Factor-α whereas an important production of Monocytes Chemoattractant Protein-1 was observed. These unprecedented observations suggest the possibility that DPSCs are shelters for the long-term persistence of B. quintana in the host, warranting further experimental and clinical investigations.

Gold Nanoparticles Combined Human β-Defensin 3 Gene-Modified Human Periodontal Ligament Cells Alleviate Periodontal Destruction via the p38 MAPK Pathway

Periodontitis is a chronic inflammatory disease with plaques as the initiating factor, which will induce the destruction of periodontal tissues. Numerous studies focused on how to obtain periodontal tissue regeneration in inflammatory environments. Previous studies have reported adenovirus-mediated human β-defensin 3 (hBD3) gene transfer could potentially enhance the osteogenic differentiation of human periodontal ligament cells (hPDLCs) and bone repair in periodontitis. Gold nanoparticles (AuNPs), the ideal inorganic nanomaterials in biomedicine applications, were proved to have synergetic effects with gene transfection. To further observe the potential promoting effects, AuNPs were added to the transfected cells. The results showed the positive effects of osteogenic differentiation while applying AuNPs into hPDLCs transfected by adenovirus encoding hBD3 gene. In vivo, after rat periodontal ligament cell (rPDLC) transplantation into SD rats with periodontitis, AuNPs combined hBD3 gene modification could also promote periodontal regeneration. The p38 mitogen-activated protein kinase (MAPK) pathway was demonstrated to potentially regulate both the in vitro and in vivo processes. In conclusion, AuNPs can promote the osteogenic differentiation of hBD3 gene-modified hPDLCs and periodontal regeneration via the p38 MAPK pathway.

Long noncoding RNA MEG3 expressed in human dental pulp regulates LPS-Induced inflammation and odontogenic differentiation in pulpitis

Pulpitis refers to inflammation of the inner pulp by invading microbes, and tissue repair occurs due to odontogenic differentiation of human dental pulp cells (hDPCs) with multidifferentiation potential. Long noncoding RNAs (lncRNAs) can modulate numerous pathological and biological processes; however, the role of lncRNAs in the inflammation and regeneration of the dentin-pulp complex in pulpitis is unclear. Here, we performed high-throughput sequencing to identify differentially expressed lncRNAs between human normal and inflamed pulp and concluded that lncMEG3 (lncRNA maternally expressed gene 3, MEG3) was significantly upregulated in both inflamed pulp and LPS-treated hDPCs. MEG3 expression in the pulp tissue was detected using the RNAscope® technique. RNA pulldown assays identified the MEG3-interacting proteins and the potential mechanisms. With MEG3 knockdown, we investigated the role of MEG3 in the secretion of inflammatory cytokines in LPS-treated hDPCs and odontogenic differentiation of hDPCs. MEG3 downregulation inhibited the secretion of TNF-α, IL-1β and IL-6 in LPS-treated hDPCs, and the p38/MAPK signaling pathway may be related to this effect. MEG3 knockdown promoted odontogenic differentiation of hDPCs by regulating the Wnt/β-catenin signaling pathway. Our study suggested that MEG3 has a negative effect on inflammation and regeneration of the dentin-pulp complex in pulpitis.

Infection of Human Dental Pulp Stromal Cells by Streptococcus mutans: Shedding Light on Bacteria Pathogenicity and Pulp Inflammation

Cariogenic Streptococcus mutans (S. mutans) is implicated in the dental pulp necrosis but also in cardiovascular tissue infections. Herein, the purpose was to elucidate how human dental pulp derived stromal cells (DPSCs) react toward a direct interaction with S. mutans. DPSCs were challenged with S. mutans. Following 3 h of interaction, DPSCs were able to internalize S. mutans (rate < 1%), and F-actin fibers played a significant role in this process. S. mutans persisted in the DPSCs for 48 h without causing a cytotoxic effect. S. mutans was, however, able to get out of the DPSCs cytoplasm and to proliferate in the extracellular environment. Yet, we noticed several adaptive responses of bacteria to the extracellular environment such as a modification of the kinetic growth, the increase in biofilm formation on type I collagen and polyester fabrics, as well as a tolerance toward amoxicillin. In response to infection, DPSCs adopted a proinflammatory profile by increasing the secretion of IL-8, lL-1β, and TNF-α, strengthening the establishment of the dental pulp inflammation. Overall, these findings showed a direct impact of S. mutans on DPSCs, providing new insights into the potential role of S. mutans in infective diseases.

Immunomodulatory Properties of Stem Cells in Periodontitis: Current Status and Future Prospective

Periodontitis is the sixth-most prevalent chronic inflammatory disease and gradually devastates tooth-supporting tissue. The complexity of periodontal tissue and the local inflammatory microenvironment poses great challenges to tissue repair. Recently, stem cells have been considered a promising strategy to treat tissue damage and inflammation because of their remarkable properties, including stemness, proliferation, migration, multilineage differentiation, and immunomodulation. Several varieties of stem cells can potentially be applied to periodontal regeneration, including dental mesenchymal stem cells (DMSCs), nonodontogenic stem cells, and induced pluripotent stem cells (iPSCs). In particular, these stem cells possess extensive immunoregulatory capacities. In periodontitis, these cells can exert anti-inflammatory effects and regenerate the periodontium. Stem cells derived from infected tissue possess typical stem cell characteristics with lower immunogenicity and immunosuppression. Several studies have demonstrated that these cells can also regenerate the periodontium. Furthermore, the interaction of stem cells with the surrounding infected microenvironment is critical to periodontal tissue repair. Though the immunomodulatory capabilities of stem cells are not entirely clarified, they show promise for therapeutic application in periodontitis. Here, we summarize the potential of stem cells for periodontium regeneration in periodontitis and focus on their characteristics and immunomodulatory properties as well as challenges and perspectives.

Human β-defensin 3 gene modification promotes the osteogenic differentiation of human periodontal ligament cells and bone repair in periodontitis

Efforts to control inflammation and achieve better tissue repair in the treatment of periodontitis have been ongoing for years. Human β-defensin 3, a broad-spectrum antimicrobial peptide has been proven to have a variety of biological functions in periodontitis; however, relatively few reports have addressed the effects of human periodontal ligament cells (hPDLCs) on osteogenic differentiation. In this study, we evaluated the osteogenic effects of hPDLCs with an adenoviral vector encoding human β-defensin 3 in an inflammatory microenvironment. Then human β-defensin 3 gene-modified rat periodontal ligament cells were transplanted into rats with experimental periodontitis to observe their effects on periodontal bone repair. We found that the human β-defensin 3 gene-modified hPDLCs presented with high levels of osteogenesis-related gene expression and calcium deposition. Furthermore, the p38 MAPK pathway was activated in this process. In vivo, human β-defensin 3 gene-transfected rat PDLCs promoted bone repair in SD rats with periodontitis, and the p38 mitogen-activated protein kinase (MAPK) pathway might also have been involved. These findings demonstrate that human β-defensin 3 accelerates osteogenesis and that human β-defensin 3 gene modification may offer a potential approach to promote bone repair in patients with periodontitis.

Dental pulp stem cells from human teeth with deep caries displayed an enhanced angiogenesis potential in vitro

Background/purpose

Dental pulp stem cells can be isolated from human teeth with deep caries (cDPSCs), but their biological characteristics are still unclear. The aim of this study was to investigate the angiogenic potential of cDPSCs and compare them to dental pulp stem cells from human normal teeth (nDPSCs).

Materials and methods

Cells were isolated from human pulp tissue of normal and infected teeth with deep caries. Basic mesenchymal stem cell (MSC) characterization was conducted. Colony forming units and proliferation ability were evaluated in nDPSCs and cDPSCs. Expression of VEGF in both tissues and cells was examined by immunohistochemical staining. After stimulating nDPSCs and cDPSCs with an angiogenic medium, angiogenic markers were evaluated by qRT-PCR and western blotting. Finally, tube formation assays were used to evaluate the in vitro angiogenesis potential of both cell populations.

Results

Both nDPSCs and cDPSCs possessed typical MSC characteristics. cDPSCs had enhanced colony formation and proliferation capacities than nDPSCs did. The expression of VEGF was higher in pulp tissue from teeth with deep caries and cDPSCs than in normal tissue and nDPSCs. When both cell types were grown in vitro under angiogenic conditions, cDPSCs expressed a higher level of angiogenic markers and showed a stronger angiogenesis potential than nDPSCs did.

Conclusion

cDPSCs maintained MSC traits and presented a higher angiogenesis potential than nDPSCs.

Method for Evaluating Neuromodulatory Properties of Dental Pulp Stem Cell as an In Vitro Model for Parkinson's Disease

Several research groups have utilized dental pulp stem cells for numerous studies as treatment modality for Parkinson's disease (PD). However, the roles of dental pulp stem cells in governing the Parkinson's disease inflammatory microenvironment remain to be evaluated. In this article, we elaborate the method where we can investigate the effects of dental pulp stem cells on neurons and microglia in an in vitro inflammatory microenvironment.

DNA methyltransferase DNMT1 inhibits lipopolysaccharide‑induced inflammatory response in human dental pulp cells involving the methylation changes of IL‑6 and TRAF6

Dental pulp inflammation is a pathological process characterized by local lesions in dental pulp and the accumulation of inflammatory mediators. DNA methylation of cytosine residues is a key epigenetic modification that is essential for gene transcription, and plays pivotal roles in inflammatory reactions and immune responses. However, the function of cytosine DNA methylation in the innate immune defense against the inflammation of dental pulp is poorly understood. To investigate the effect of DNA methylation in inflamed dental pulp upon innate immune responses, expression levels of the DNA methyltransferases (DNMT1, DNMT3a and DNMT3b) in human dental pulp cells (hDPCs) after lipopolysaccharide (LPS) stimulation were evaluated by western blotting and reverse transcription‑quantitative (RT‑q) PCR. Only DNMT1 expression was decreased, while the transcription of inflammatory cytokines was increased. In the immune responses of LPS‑induced hDPCs, the results of RT‑qPCR and ELISA showed that DNMT1 knockdown promoted the production of the pro‑inflammatory cytokines, interleukin (IL)‑6 and IL‑8. Western blotting demonstrated that DNMT1 knockdown increased the phosphorylation levels of IKKα/β and p38 in the NF‑κB and MAPK signaling pathways, respectively. Furthermore, MeDIP and RT‑qPCR analysis demonstrated that the 5‑methylcytosine levels of the IL‑6 and TNF receptor‑associated factor 6 (TRAF6) promoters were significantly decreased in DNMT1‑deficient hDPCs. Taken together, these results indicated that the expression of DNMT1 was decreased after LPS stimulation in hDPCs. DNMT1 depletion increased LPS‑induced cytokine secretion, and activated NF‑κB and MAPK signaling; these mechanisms may involve the decreased methylation levels of the IL‑6 and TRAF6 gene promoters. This study emphasized the role of DNMT1‑dependent DNA methylation on the inflammation of LPS‑infected dental pulp and provides a new rationale for the investigation of the molecular mechanisms of inflamed dental pulps.

Immunomodulatory properties of dental tissue-derived mesenchymal stem cells: Implication in disease and tissue regeneration

Mesenchymal stem cells (MSCs) are considered as an attractive tool for tissue regeneration and possess a strong immunomodulatory ability. Dental tissue-derived MSCs can be isolated from different sources, such as the dental pulp, periodontal ligament, deciduous teeth, apical papilla, dental follicles and gingiva. According to numerous in vitro studies, the effect of dental MSCs on immune cells might depend on several factors, such as the experimental setting, MSC tissue source and type of immune cell preparation. Most studies have shown that the immunomodulatory activity of dental MSCs is strongly upregulated by activated immune cells. MSCs exert mostly immunosuppressive effects, leading to the dampening of immune cell activation. Thus, the reciprocal interaction between dental MSCs and immune cells represents an elegant mechanism that potentially contributes to tissue homeostasis and inflammatory disease progression. Although the immunomodulatory potential of dental MSCs has been extensively investigated in vitro, its role in vivo remains obscure. A few studies have reported that the MSCs isolated from inflamed dental tissues have a compromised immunomodulatory ability. Moreover, the expression of some immunomodulatory proteins is enhanced in periodontal disease and even shows some correlation with disease severity. MSC-based immunomodulation may play an essential role in the regeneration of different dental tissues. Therefore, immunomodulation-based strategies may be a very promising tool in regenerative dentistry.

Astragaloside IV attenuates inflammatory injury and promotes odontoblastic differentiation in lipopolysaccharide-stimulated MDPC-23 cells and rat pulpitis

BACKGROUND

Astragaloside IV (AS-IV), a natural herbal compound from Astragalus membranaceus, has inhibitory effects on receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis, and RANKL signal helps to regulate odontoblast differentiation. However, whether and how AS-IV affects odontoblastic differentiation remains unclear.

METHODS

Lipopolysaccharide (LPS)-stimulated MDPC-23 cells and rat pulpitis were treated with AS-IV, cell viability, and LDH leakage was analyzed by CCK-8 assay and LDH Leakage assay. The production of TNF-α and IL-6 was determined by ELISA and qRT-PCR assay. The expression of alkaline phosphatase (ALP) was detected using an ALP assay kit, and the expression of dentin sialophos-phoprotein (DSPP), dentin matrix protein-1 (DMP1), basic fibroblast growth factor (FGF2), and phosphorylated extracellular signal-regulated kinase (p-ERK) was determined by western blot.

RESULTS

AS-IV dose dependently increased in cell viability and decreased the overproduction of TNF-α and IL-6 in LPS-stimulated MDPC-23 cells. AS-IV also counteracted LPS-induced downregulation of ALP, DSPP, and DMP1 in MDPC-23 cells. Furthermore, AS-IV significantly decreased the expression of FGF2 and p-ERK in LPS-stimulated MDPC-23 cells. More important, the addition of FGF2 partly neutralized AS-IV-mediated inhibition of FGF2/ERK signaling, abolished AS-IV-induced reduction of TNF-α and IL-6, and counteracted AS-IV-induced upregulation of DSPP and DMP-1 in these cells. Meanwhile, AS-IV inhibited the excessive production of TNF-α and IL-6, suppressed the downregulation of DSPP and DMP1, and disturbed the up-regulation of FGF2 and p-ERK in the pulp tissues of rat pulpitis model.

CONCLUSIONS

AS-IV exerted anti-inflammatory and pro-differentiation effects in LPS-stimulated MDPC-23 cells and rat pulpitis via inhibiting the FGF2/ERK signaling pathway.

Angiogenic effect of platelet-rich concentrates on dental pulp stem cells in inflamed microenvironment

OBJECTIVE

In this study, we aimed to determine the suitable concentrations of human platelet lysate (HPL) and platelet-rich plasma (PRP) for maintaining the in vitro proliferative and angiogenic potential of inflamed dental pulp stem cells.

MATERIALS AND METHODS

Lipopolysaccharide (LPS)-induced inflamed dental pulp-derived stem cells (iDPSCs) were treated with different concentrations of HPL and PRP (10% and 20%) followed by determination of viability using Alamar Blue assay. Expression of angiogenesis-, adhesion-, and inflammation-regulating genes was also analyzed using RT-qPCR array. Furthermore, expression of growth factors at protein level in the cell culture microenvironment was measured using multiplex assay.

RESULTS

Viability of iDPSCs was significantly (p < 0.05) higher in 20% HPL-supplemented media compared to iDPSCs. Expression of 10 out of 12 selected angiogenic genes, four out of seven adhesion molecules, and seven out of nine cytokine-producing genes were significantly (p < 0.05) higher in cells maintained in 20% HPL-supplemented media compared to that in FBS-supplemented media. Furthermore, expression of all the selected growth factors was significantly higher (p < 0.05) in the supernatants from 20% HPL media at 12 and 24 h post-incubation.

CONCLUSION

This study suggests that 20% HPL could be optimum to stimulate angiogenesis-related factors in iDPSCs while maintaining their viability.

CLINICAL RELEVANCE

This data may suggest the potential use of 20% HPL for expanding DPSCs scheduled for clinical trials for regenerative therapies including dental pulp regeneration.

Pulp capping materials modulate the balance between inflammation and regeneration

The interrelations between inflammation and regeneration are of particular significance within the dental pulp tissue inextensible environment. Recent data have demonstrated the pulp capacity to respond to insults by initiating an inflammatory reaction and dentin pulp regeneration. Different study models have been developed in vitro and in vivo to investigate the initial steps of pulp inflammation and regeneration. These include endothelial cell interaction with inflammatory cells, stem cell interaction with pulp fibroblasts, migration chambers to study cell recruitment and entire human tooth culture model. Using these models, the pulp has been shown to possess an inherent anti-inflammatory potential and a high regeneration capacity in all teeth and at all ages. The same models were used to investigate the effects of tricalcium silicate-based pulp capping materials, which were found to modulate the pulp anti-inflammatory potential and regeneration capacity. Among these, resin-containing materials such as TheraCal^® shift the pulp response towards the inflammatory reaction while altering the regeneration process. On the opposite, resin-free materials such as Biodentine™ have an anti-inflammatory potential and induce the pulp regeneration capacity. This knowledge contradicts the new tendency of developing resin-based calcium silicate hybrid materials for direct pulp capping. Additionally, it would allow investigating the modulatory effects of newly released pulp capping materials on the balance between tissue inflammation and regeneration. It would also set the basis for developing future capping materials targeting these processes.