The anti-inflammatory effects of matrix metalloproteinase-3 on irreversible pulpitis of mature erupted teeth

Anti-Inflammatory Effect of Dietary Pentadecanoic Fatty Acid Supplementation on Inflammatory Bowel Disease in SAMP1/YitFc Mice

BACKGROUND/OBJECTIVES

Dietary fats have been linked to the increasing incidence of chronic diseases, including inflammatory bowel diseases (IBD), namely, Crohn's disease (CD).

METHODS

This study investigated the impact of pentadecanoic acid (C15:0), a type of an odd-numbered chain saturated fatty acid, for its potential anti-inflammatory properties in different mouse models of experimental IBD using the SAMP1/YitFc (SAMP) mouse line (14- or 24-week-old), including chronic ileitis and DSS-induced colitis. To quantitively assess the effect of C:15, we tested two dosages of C:15 in selected experiments in comparison to control mice. Intestinal inflammation and intestinal permeability were used as primary outcomes.

RESULTS

In ileitis, C:15 supplementation showed an anti-inflammatory effect in SAMP mice (e.g., a reduction in ileitis severity vs. control p < 0.0043), which was reproducible when mice were tested in the DSS model of colitis (e.g., reduced permeability vs. control p < 0.0006). Of relevance, even the short-term C:15 therapy prevented colitis in mice by maintaining body weight, decreasing inflammation, preserving gut integrity, and alleviating colitis signs.

CONCLUSIONS

Collectively, the findings from both ileitis and colitis in SAMP mice indicate that C:15 may have therapeutic effects in the treatment of IBD (colitis in the short term). This promising effect has major translational potential for the alleviation of IBD in humans.

Immune System of Dental Pulp in Inflamed and Normal Tissue

Teeth are vulnerable to structural compromise, primarily attributed to carious lesions, in which microorganisms originating from the oral cavity deteriorate the mineralized structures of enamel and dentin, subsequently infiltrating the underlying soft connective tissue, known as the dental pulp. Nonetheless, dental pulp possesses the necessary capabilities to detect and defend against bacteria and their by-products, using a variety of intricate defense mechanisms. The pulp houses specialized cells known as odontoblasts, which encounter harmful substances produced by oral bacteria. These cells identify pathogens at an early stage and commence the immune system response. As bacteria approach the pulp, various cell types within the pulp, such as different immune cells, stem cells, fibroblasts, as well as neuronal and vascular networks, contribute a range of defense mechanisms. Therefore, the immune system is present in the healthy pulp to restrain the initial spread of pathogens, and then in the inflamed pulp, it prepares the conditions for necrosis or regeneration, so inflammatory response mechanisms play a critical role in maintaining tissue homeostasis. This review aims to consolidate the existing literature on the immune system in dental pulp, encompassing current knowledge on this topic that explains the diverse mechanisms of recognition and defense against pathogens exhibited by dental pulp cells, elucidates the mechanisms of innate and adaptive immunity in inflamed pulp, and highlights the difference between inflamed and normal pulp tissue.

Dental pulp mesenchymal stem cells-response to fibrin hydrogel reveals ITGA2 and MMPs expression

Regenerative endodontic procedures (REP) aim at reestablishing tooth vitality by replacing the irreversibly damaged dental pulp removed by the dental practitioner with a new functional one. The current treatment of advanced caries relies on the replacement of the inflamed or necrosed dental pulp with an inert filling material. This leads to a functional but non-vital tooth, which lacks the ability to sense dental tissue damage, and to protect from further bacterial attack. Therapeutic strategies inspired by tissue engineering called REP propose to regenerate a fully functional dental pulp directly in the canal space. Promising results were obtained using dental pulp mesenchymal stem cells (DP-MSCs) in combination with bio-inspired artificial and temporary 3D hydrogels made of extracellular matrix molecules such as collagen and fibrin biomacromolecules. However, the uncontrolled mechanisms of DP regeneration from DP-MSCs in 3D biomacromolecules fail to regenerate a fully functional DP and can induce fibrotic scarring or mineralized tissue formation to a non-negligible extent. The lack of knowledge regarding the early molecular mechanisms initiated by DP-MSCs seeded in ECM-made hydrogels is a scientific lock for REP. In this study, we investigated the early DP-MSC-response in a 3D fibrin hydrogel. DP-MSCs isolated from human third molars were cultured for 24 h in the fibrin hydrogel. The differential transcript levels of extracellular and cell surface genes were screened with 84-gene PCR array. Out of the 84 genes screened, 9 were found to be overexpressed, including those coding for the integrin alpha 2 subunit, the collagenase MMP1 and stromelysins MMP3, MMP10 and MMP12. Over-expression of ITGA2 was confirmed by RT-qPCR. The expression of alpha 2 integrin subunit protein was assessed over time by immunoblot and immunofluorescence staining. The increase in the transcript level of MMP1, MMP3, MM10 and MMP12 was confirmed by RT-qPCR. The overexpression of MMP1 and 3 at the protein level was assessed by immunoblot. MMP3 expression by DP-MSCs was observed by immunofluorescence staining. This work demonstrates overexpression of ITGA2 and of MMP1, 3, 10 and 12 by DP-MSCs cultured in a fibrin hydrogel. The main preliminary extracellular and cell surface response of the DP-MSCs to fibrin hydrogel seems to rely on a ITGA2/MMP3 axis. Further investigations are needed to precisely decipher the role of this axis in dental pulp tissue building. Nevertheless, this work identifies extracellular and cell surface molecules that could be potential checkpoints to be targeted to guide proper dental pulp tissue regeneration.

Odontogenic and anti-inflammatory effects of magnesium-doped bioactive glass in vital pulp therapy

This study aimed to investigate the effects of magnesium-doped bioactive glass (Mg-BG) on the mineralization, odontogenesis, and anti-inflammatory abilities of human dental pulp stem cells (hDPSCs). Mg-BG powders with different Mg concentrations were successfully synthesized via the sol-gel method and evaluated using x-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. Apatite formation was observed on the surfaces of the materials after soaking in simulated body fluid. hDPSCs were cultured with Mg-BG powder extracts in vitro, and no evident cytotoxicity was observed. Mg-BG induced alkaline phosphatase (ALP) expression and mineralization of hDPSCs and upregulated the expression of odontogenic genes, including those encoding dentin sialophosphoprotein, dentin matrix protein 1, ALP, osteocalcin, and runt-related transcription factor 2. Moreover, Mg-BG substantially suppressed the secretion of inflammatory cytokines (interleukin [IL]-4, IL-6, IL-8, and tumor necrosis factor-alpha). Collectively, the results of this study suggest that Mg-BG has excellent in vitro bioactivity and is a potential material for vital pulp therapy of inflamed pulps.

Hyaluronic Acid Interacting Molecules Mediated Crosstalk between Cancer Cells and Microenvironment from Primary Tumour to Distant Metastasis

Hyaluronic acid (HA) is a prominent component of the extracellular matrix, and its interactions with HA-interacting molecules (HAIMs) play a critical role in cancer development and disease progression. This review explores the multifaceted role of HAIMs in the context of cancer, focusing on their influence on disease progression by dissecting relevant cellular and molecular mechanisms in tumour cells and the tumour microenvironment. Cancer progression can be profoundly affected by the interactions between HA and HAIMs. They modulate critical processes such as cell adhesion, migration, invasion, and proliferation. The TME serves as a dynamic platform in which HAIMs contribute to the formation of a unique niche. The resulting changes in HA composition profoundly influence the biophysical properties of the TME. These modifications in the TME, in conjunction with HAIMs, impact angiogenesis, immune cell recruitment, and immune evasion. Therefore, understanding the intricate interplay between HAIMs and HA within the cancer context is essential for developing novel therapeutic strategies. Targeting these interactions offers promising avenues for cancer treatment, as they hold the potential to disrupt critical aspects of disease progression and the TME. Further research in this field is imperative for advancing our knowledge and the treatment of cancer.

Luteolin Is a Potential Immunomodulating Natural Compound against Pulpal Inflammation

Aim

The present study evaluated the therapeutic effects of luteolin in alleviating pulpitis of dental pulp- (DP-) derived microvesicles (MVs) via the inhibition of protein kinase R- (PKR-) mediated inflammation. Methodology. Proteomic analysis of immortalized human dental pulp (DP-1) cell-derived MVs was performed to identify PKR-associated molecules. The effect of luteolin on PKR phosphorylation in DP-1 cells and the expression of tumor necrosis factor-α (TNF-α) in THP-1 macrophage-like cells were validated. The effect of luteolin on cell proliferation was compared with that of chemical PKR inhibitors (C16 and 2-AP) and the unique commercially available sedative guaiacol-parachlorophenol. In the dog experimental pulpitis model, the pulps were treated with (1) saline, (2) guaiacol-parachlorophenol, and (3) luteolin. Sixteen teeth from four dogs were extracted, and the pulp tissues were analyzed using hematoxylin and eosin staining. Immunohistochemical staining was performed to analyze the expression of phosphorylated PKR (pPKR), myeloperoxidase (MPO), and CD68. Experimental endodontic-periodontal complex lesions were established in mouse molar through a silk ligature and simultaneous MV injection. MVs were prepared from DP-1 cells with or without pretreatment with 2-AP or luteolin. A three-dimensional microcomputed tomography analysis was performed on day 7 (n = 6). Periodontal bone resorption volumes were calculated for each group (nonligated-ligated), and the ratio of bone volume to tissue volume was measured.

Results

Proteomic analysis identified an endogenous PKR activator, and a protein activator of interferon-induced PKR, also known as PACT, was included in MVs. Luteolin inhibited the expressions of pPKR in DP-1 cells and TNF-α in THP-1 cells with the lowest suppression of cell proliferation. In the dog model of experimental pulpitis, luteolin treatment suppressed the expression of pPKR-, MPO-, and CD68-positive cells in pulp tissues, whereas guaiacol-parachlorophenol treatment caused coagulative necrosis and disruption. In a mouse model of endodontic-periodontal complex lesions, luteolin treatment significantly decreased MV-induced alveolar bone resorption.

Conclusion

Luteolin is an effective and safe compound that inhibits PKR activation in DP-derived MVs, enabling pulp preservation.

The Reparative Function of MMP13 in Tertiary Reactionary Dentinogenesis after Tooth Injury

MMP13 gene expression increases up to 2000-fold in mineralizing dental pulp cells (DPCs), with research previously demonstrating that global MMP13 deletion resulted in critical alterations in the dentine phenotype, affecting dentine-tubule regularity, the odontoblast palisade, and significantly reducing the dentine volume. Global MMP13-KO and wild-type mice of a range of ages had their molar teeth injured to stimulate reactionary tertiary dentinogenesis. The response was measured qualitatively and quantitatively using histology, immunohistochemistry, micro-CT, and qRT-PCR in order to assess changes in the nature and volume of dentine deposited as well as mechanistic links. MMP13 loss affected the reactionary tertiary dentine quality and volume after cuspal injury and reduced Nestin expression in a non-exposure injury model, as well as mechanistic links between MMP13 and the Wnt-responsive gene Axin2. Acute pulpal injury and pulp exposure to oral fluids in mice teeth showed upregulation of the MMP13 in vivo, with an increase in the gene expression of Mmp8, Mmp9, and Mmp13 evident. These results indicate that MMP13 is involved in tertiary reactionary dentine formation after tooth injury in vivo, potentially acting as a key molecule in the dental pulp during dentine-pulp repair processes.

Dentin Degradation: From Tissue Breakdown to Possibilities for Therapeutic Intervention

Purpose of the Review

Presently, dental materials science is driven by the search for new and improved materials that can trigger specific reactions from the affected tissue to stimulate repair or regeneration while interacting with the oral environment to promote or maintain oral health. In parallel, evidence from the past decades has challenged the exclusive role of bacteria in dentin tissue degradation in caries, questioning our understanding of caries etiopathogenesis. The goal of this review is to recapitulate the current evidence on the host and bacterial contributions to degradation, inflammation, and repair of the dentin-pulp complex in caries.

Recent Findings

Contrasting findings attribute dentin breakdown to the activity of endogenous enzymes, such as matrix metalloproteinases (MMPs) and cathepsins, while the role of bacteria and their by-products in the destruction of dentin organic matrix and pulp inflammation has been for decades supported as an incontestable paradigm. Aiming to better understand the mechanisms involved in collagen degradation by host enzymes in caries, studies have showed that these proteinases are expressed in the mature dentin (i.e., after dentin formation) and become activated by the low pH in the acidic environment resulted by bacterial metabolism in caries. However, different host sources other than dentin-bound proteinases seem to also contribute to caries progression, such as saliva and pulp. Interestingly, studies evaluating pulp responses to bacteria invasion and inflammation in caries report higher levels of MMPs and cathepsins in inflamed tissue, but also showed MMP potential to resolve inflammation and stimulate wound healing. Notably, as reported for other tissues, MMPs exert dual roles in the dentin-pulp complex in caries, participating or regulating both degradative and reparative mechanisms.

Summary

The specific roles of host and bacteria and their by-products in caries progression have yet to be clarified. The complex interactions between inflammation and repair in caries pose challenges to a clear understanding of the dentin-pulp complex responses and changes to bacteria invasion. However, it opens new venues for the development of novel therapies and dental biomaterials based on the modulation of specific mechanisms to favor tissue repair and healing.

Hiding in Plain Sight: Human Gingival Fibroblasts as an Essential, Yet Overlooked, Tool in Regenerative Medicine

Adult human gingival fibroblasts (HGFs), the most abundant cells in the oral cavity, are essential for maintaining oral homeostasis. Compared with other tissues, adult oral mucosal wounds heal regeneratively, without scarring. Relative to fibroblasts from other locations, HGFs are relatively refractory to myofibroblast differentiation, immunomodulatory, highly regenerative, readily obtained via minimally invasive procedures, easily and rapidly expanded in vitro, and highly responsive to growth factors and cytokines. Consequently, HGFs might be a superior, yet perhaps underappreciated, source of adult mesenchymal progenitor cells to use in tissue engineering and regeneration applications, including the treatment of fibrotic auto-immune connective tissue diseases such as scleroderma. Herein, we highlight in vitro and translational studies that have investigated the regenerative and differentiation potential of HGFs, with the objective of outlining current limitations and inspiring future research that could facilitate translating the regenerative potential of HGFs into the clinic.

The Role of Cellular Metabolism in Maintaining the Function of the Dentine-Pulp Complex: A Narrative Review

The cellular metabolic processes ensure the physiological integrity of the dentine-pulp complex. Odontoblasts and odontoblast-like cells are responsible for the defence mechanisms in the form of tertiary dentine formation. In turn, the main defence reaction of the pulp is the development of inflammation, during which the metabolic and signalling pathways of the cells are significantly altered. The selected dental procedures, such as orthodontic treatment, resin infiltration, resin restorations or dental bleaching, can impact the cellular metabolism in the dental pulp. Among systemic metabolic diseases, diabetes mellitus causes the most consequences for the cellular metabolism of the dentine-pulp complex. Similarly, ageing processes present a proven effect on the metabolic functioning of the odontoblasts and the pulp cells. In the literature, several potential metabolic mediators demonstrating anti-inflammatory properties on inflamed dental pulp are mentioned. Moreover, the pulp stem cells exhibit the regenerative potential essential for maintaining the function of the dentine-pulp complex.

Biomechanical Modulation of Dental Pulp Stem Cell (DPSC) Properties for Soft Tissue Engineering

Dental pulp regeneration strategies frequently result in hard tissue formation and pulp obliteration. The aim of this study was to investigate whether dental pulp stem cells (DPSCs) can be directed toward soft tissue differentiation by extracellular elasticity. STRO-1-positive human dental pulp cells were magnetically enriched and cultured on substrates with elasticities of 1.5, 15, and 28 kPa. The morphology of DPSCs was assessed visually. Proteins relevant in mechanobiology ACTB, ITGB1, FAK, p-FAK, TALIN, VINCULIN, PAXILLIN, ERK 1/2, and p-ERK 1/2 were detected by immunofluorescence imaging. Transcription of the pulp marker genes BMP2, BMP4, MMP2, MMP3, MMP13, FN1, and IGF2 as well as the cytokines ANGPT1, VEGF, CCL2, TGFB1, IL2, ANG, and CSF1 was determined using qPCR. A low stiffness, i.e., 1.5 kPa, resulted in a soft tissue-like phenotype and gene expression, whereas DPSCs on 28 kPa substrates exhibited a differentiation signature resembling hard tissues with a low cytokine expression. Conversely, the highest cytokine expression was observed in cells cultured on intermediate elasticity, i.e., 15 kPa, substrates possibly allowing the cells to act as “trophic mediators”. Our observations highlight the impact of biophysical cues for DPSC fate and enable the design of scaffold materials for clinical pulp regeneration that prevent hard tissue formation.

Expression of Toll-like receptor 2, Dectin-1, and Osteopontin in murine model of pulpitis

OBJECTIVES

This in vivo animal study aimed to develop a murine model of pulpitis induced by pulp exposure with or without application of zymosan in Naval Medical Research Institute (NMRI) mice and observe expressions of Toll-like receptor (TLR)-2, TLR-4, Dectin-1, Osteopontin (OPN), tumor necrosis factor alpha (TNF-α), interleukin (IL)-6, and IL-1ß.

MATERIAL AND METHODS

A total of 168 NMRI mice were divided into two groups, i.e., group A (n = 84) (pulpitis induced by pulp exposure only) and group B (n = 84) (pulpitis induced by pulp exposure and zymosan application). Right maxillary molar pulps were exposed with ¼ round bur, and animals were sacrificed at 0, 6, 9, 12, 24, 48, and 72 h. The exposed teeth were obtained for real-time polymerase chain reaction (qRT-PCR) analysis and histological and immunohistochemistry (IHC) analysis.

RESULTS

Histological evaluation revealed a time-dependent steady increase in inflammation. Similar time-dependent increase in the expression of inflammatory cytokines was noted. Group A exhibited an increase in TLR-4, Dectin-1, and OPN at 6 h, while TLR-2 was expressed at 24 h. Group B expressed TLR-2, Dectin-1, and OPN at 9, 48, and 72 h, respectively (p ≤ 0.05). Expression of OPN and TNF-α exhibited a similar pattern in both groups. IHC also detected expression of TLR-2, Dectin-1, TLR4, and CD68 in some cells at 6 and 9 h.

CONCLUSIONS

NMRI mice provided for a stable pulp inflammation model. Zymosan may be used to develop pulp inflammation model and study inflammatory response towards fungal antigens. Dental pulp expressed Dectin-1 receptor. OPN and TNF-α exhibited a similar expression pattern.

CLINICAL RELEVANCE

Innate immunity of dental pulp is capable of detecting fungal pathogens.

Genome wide analysis of dexamethasone stimulated mineralization in human dental pulp cells by RNA sequencing

Human dental pulp cells (hDPCs) contain mesenchymal stem cells and are therefore indispensible for reparative dentin formation. Here, we present a pilot study of transcriptomic profiles of mineralized hDPCs isolated from sound human maxillary third molars. We observed altered gene expression of hDPCs between control (dexamethasone free) and experimental (dexamethasone 1 nm) groups. Differential expression analysis revealed up-regulation of several inflammation and mineralization-related genes in the experimental group. After a Gene Ontology analysis for predicting genes involved in biological process, cellular component and molecular function, we found enrichment of genes related to protein binding. Based on the results of Kyoto Encylopedia of Genes and Genomes pathway analysis, it is suggested up-regulated genes in mineralized hDPCs were mostly enriched in the mitogen-activated protein kinase (MAPK) signaling pathway, fluid shear stress and the atherosclerosis signaling pathway, etc. Importantly, Gene Set Enrichment Analysis revealed dexamethasone was positively related to the Janus kinase/signal transducer and activator of transcription, MAPK and Notch signaling pathway. Moreover, it was suggested that dexamethasone regulates signaling pathway in pluripotency of stem cells. Collectively, our work highlights transcriptome level gene regulation and intercellular interactions in mineralized hDPCs. The database produced in the present study paves the way for further investigations looking to explore genes that are involved in dental pulp cells mineralization.

Gene expression analysis of toll like receptor 2 and 4, Dectin-1, Osteopontin and inflammatory cytokines in human dental pulp ex-vivo

BACKGROUND

Toll like receptors (TLR) 2 and 4 present on innate immune cells of the dental pulp detect cariogenic bacteria. Along with bacteria, C. albicans may also be present in dental caries. The presence of C. albicans can be detected by Dectin-1 a C type Lectin receptor. Expression of Dectin-1 in human pulpits has not been reported. Similarly, cytokines are released as a consequence of dental pulp inflammation caused by cariogenic bacteria. The T helper (Th) 1 inflammatory response leads to exacerbation of inflammation and its relationship with Osteopontin (OPN) is not known in pulp inflammation.

OBJECTIVE

The aim of this study was to observe the expression of Dectin-1, TLR-2, OPN and pro-inflammatory cytokines in irreversibly inflamed human dental pulp and to observe relationship between Dectin-1/TLR-2 and OPN/Pro-inflammatory cytokines in the presence of appropriate controls.

METHODS

A total of 28 subjects diagnosed with irreversible pulpitis were included in this ex-vivo study. Fifteen samples were subjected to standard hematoxylin and Eosin (H&E) and immunohistochemistry staining. Whereas, gene expression analysis was performed on 13 samples to observe mRNA expression of pro-inflammatory cytokines; tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1 beta (ß), IL-6 Dectin-1, OPN, TLR-2 and TLR-4. SPSS version 21 was used for statistical analysis. One way analysis of variance (ANOVA), Pearson correlation and Chi-square test were used at p ≤ 0.05.

RESULTS

Gene expressions of Dectin-1, TLR-2 and TLR-4 were observed in all samples. Dectin-1 and TLR-2 expressions were significantly correlated (r = 0.5587, p = 0.0002). Similarly, OPN and TNF-α expression showed a significant correlation (r = 0.5860, p = 0001). The agreement between histologic and clinical diagnosis was 69.2% in the cases of irreversible pulpitis.

CONCLUSION

Dectin-1 was expressed by inflamed human dental pulp. Dectin-1 and TLR-2 expression pattern was suggestive of a collaborative receptor response in inflamed pulp environment. OPN and TNF-α expressions showed a positive correlation indicating a possible relationship.

Dentin Matrix Metalloproteinases: A Futuristic Approach Toward Dentin Repair and Regeneration

Matrix metalloproteinases (MMPs) have been linked to modulating healing during the production of tertiary dentin, as well as the liberation of physiologically active molecules and the control of developmental processes. Although efforts to protect dentin have mostly centered on preventing these proteases from doing their jobs, their role is actually much more intricate and crucial for dentin healing than anticipated. The role of MMPs as bioactive dentin matrix components involved in dentin production, repair, and regeneration is examined in the current review. The mechanical characteristics of dentin, especially those of reparative and reactionary dentin, and the established functions of MMPs in dentin production are given particular attention. Because they are essential parts of the dentin matrix, MMPs should be regarded as leading applicants for dentin regeneration.

Does α-lipoic acid therapeutically effective against experimentally induced-acute pulpitis in rats?

The purpose of the study was to investigate the therapeutic effects of α-lipoic acid (ALA) on an induced-acute pulpitis model in rats. Twenty-four Wistar albino rats were randomly divided into three groups: control, induced-acute pulpitis (PULP) and PULP + ALA groups. In the PULP and PULP + ALA groups, the crowns of the maxillary left incisors were removed horizontally. All exposed pulp tissues were treated with 5 µL LPS solution. In the PULP + ALA group, the rats were treated intraperitoneally with a single dose of ALA (100 mg/kg). The rats were sacrificed 24 h after pulp injury, and the trunk blood and pulp samples were collected and then determined using ELISA assay kits. TNF-α, IL-1β, MMP-1 and MMP-2 levels in the serum and pulp tissues were considerably higher in the PULP group than the control group (p < 0.01-0.001). In the PULP + ALA group, TNF-α, IL-1β, MMP-1 and MMP-2 levels in the serum and pulp tissues decreased significantly compared to the PULP group (p < 0.05-0.001). ALA decreases pro-inflammatory mediators and proteolytic enzymes, which might relieve acute inflammation.

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.

Dentine matrix metalloproteinases as potential mediators of dentine regeneration

Matrix metalloproteinases (MMPs) have been implicated not only in the regulation of developmental processes but also in the release of biologically active molecules and in the modulation of repair during tertiary dentine formation. Although efforts to preserve dentine have focused on inhibiting the activity of these proteases, their function is much more complex and necessary for dentine repair than expected. The present review explores the role of MMPs as bioactive components of the dentine matrix involved in dentine formation, repair and regeneration. Special consideration is given to the mechanical properties of dentine, including those of reactionary and reparative dentine, and the known roles of MMPs in their formation. MMPs are critical components of the dentine matrix and should be considered as important candidates in dentine regeneration.

Conditioned medium derived from 3D tooth germs: A novel cocktail for stem cell priming and early in vivo pulp regeneration

OBJECTIVES

Conditioned medium (CM) from 2D cell culture can mitigate the weakened regenerative capacity of the implanted stem cells. However, the capacity of 3D CM to prime dental pulp stem cells (DPSCs) for pulp regeneration and its protein profile are still elusive. We aim to investigate the protein profile of CM derived from 3D tooth germs, and to unveil its potential for DPSCs-based pulp regeneration.

MATERIALS AND METHODS

We prepared CM of 3D ex vivo cultured tooth germ organs (3D TGO-CM) and CM of 2D cultured tooth germ cells (2D TGC-CM) and applied them to prime DPSCs. Influences on cell behaviours and protein profiles of CMs were compared. In vivo pulp regeneration of CMs-primed DPSCs was explored using a tooth root fragment model on nude mice.

RESULTS

TGO-CM enhanced DPSCs proliferation, migration, in vitro mineralization, odontogenic differentiation, and angiogenesis performances. The TGO-CM group generated superior pulp structures, more odontogenic cells attachment, and enhanced vasculature at 4 weeks post-surgery, compared with the TGC-CM group. Secretome analysis revealed that TGO-CM contained more odontogenic and angiogenic growth factors and fewer pro-inflammatory cytokines. Mechanisms leading to the differential CM profiles may be attributed to the cytokine-cytokine receptor interaction and PI3K-Akt signalling pathway.

CONCLUSIONS

The unique secretome profile of 3D TGO-CM made it a successful priming cocktail to enhance DPSCs-based early pulp regeneration.

The Trinity of Matrix Metalloproteinases, Inflammation, and Cancer: A Literature Review of Recent Updates

The critical link between cancer and inflammation has been known for many years. This complex network was further complexed by revealing the association of the matrix metalloproteinase family members with inflammatory cytokines, which were previously known to be responsible for the development of metastasis. This article summarizes the current studies which evaluate the relationship between cancer and inflammatory microenvironment as well as the roles of MMPs on invasion and metastasis together.

Diagnostic potential and future directions of matrix metalloproteinases as biomarkers in gingival crevicular fluid of oral and systemic diseases

Gingival crevicular fluid (GCF) is a physiological fluid and an inflammatory serum exudate derived from the gingival plexus of blood vessels and mixed with host tissues and subgingival plaque flows. In addition to proteins, GCF contains a diverse population of cells, including desquamated epithelial cells, cytokines, electrolytes, and bacteria from adjacent plaques. Recently, matrix metalloproteinases(MMPs), which are endopeptidases that are active against extracellular macromolecules, in GCF have been revealed as potential utility biomarkers for the diagnosis and follow-up of oral and systemic diseases, thereby facilitating the early evaluation of malignancy risk and the monitoring of disease progression and treatment response. Tissue inhibitors of metalloproteinases (TIMPs) are specific inhibitors of matrixins that participate in the regulation of local activities of MMPs in tissues. This review provides an overview of the latest findings on the diagnostic and prognostic values of MMPs and TIMPs in GCF of oral and systemic diseases, including periodontal disease, pulpitis, peri-implantitis and cardiovascular disease as well as the extraction, detection and analytical methods for GCF.

MMP-3 plays a major role in calcium pantothenate-promoted wound healing after fractional ablative laser treatment

Ablative fractional laser treatment leads to a loss of matrix metalloproteinase-3 (MMP-3) expression; therefore, in the present in vitro study, we addressed the role of MMP-3 and its regulation by calcium pantothenate in wound healing processes at the molecular level. Utilizing confocal laser microscopy, we investigated MMP-3 protein expression in fractional ablative CO₂ laser-irradiated skin models. In addition, we established full-thickness 3D skin models using fibroblasts and keratinocytes with a MMP-3 knockdown that were irradiated with a fractional ablative Er:YAG laser to set superficial injuries with standardized dimensions and minimal thermal damage to the surrounding tissue. We revealed an upregulation of MMP-3 protein expression in laser-irradiated skin models receiving aftercare treatment with calcium pantothenate. Skin models with MMP-3 knockdown exhibited a slower wound closure after laser treatment compared to controls. Gene expression profiling detected an MMP-3 knockdown-dependent upregulation of cytokines and chemokines (e.g. IL-36B, CXCL17, IL-37, CXCL5), antimicrobial peptides (e.g., S100A7, S100A12), epidermal crosslinking enzymes (TGM5), and differentiation markers (e.g., LOR, KRT1, FLG2). We also detected a downregulation of cathepsin V and MMP-10, both of which play a prominent role in wound healing processes. After fractional ablative laser injury, an aftercare treatment with calcium pantothenate accelerated wound closure in MMP-3 expressing models faster than in MMP-3 knockdown models. Our data substantiate a major role of MMP-3 in wound healing processes after ablative laser treatments. For the first time, we could show that calcium pantothenate exerts its wound healing-promoting effects at least partly via MMP-3.

Review of Animal Models to Study Pulp Inflammation

Human dental pulp is a highly dynamic tissue equipped with a network of resident immunocompetent cells that play a major role in the defense against pathogens and during tissue injury. Animal studies are mandatory and complementary to in vitro experiments when studying the physiopathology of dental pulp, new diagnostic tools, or innovative therapeutic strategies. This animal approach makes it possible to define a benefit-risk ratio necessary to be subsequently tested in humans. Among the animal kingdom, rodents, rabbits, ferrets, swine, dogs, and non-human primates have been used to model human pulpitis. The diversity of animals found in studies indicate the difficulty of choosing the correct and most efficient model. Each animal model has its own characteristics that may be advantageous or limiting, according to the studied parameters. These elements have to be considered in preclinical studies. This article aims to provide a thorough understanding of the different animal models used to study pulp inflammation. This may help to find the most pertinent or appropriate animal model depending on the hypothesis investigated and the expected results.

Transcriptional Differences for COVID-19 Disease Map Genes between Males and Females Indicate a Different Basal Immunophenotype Relevant to the Disease

Worldwide COVID-19 epidemiology data indicate differences in disease incidence amongst sex and gender demographic groups. Specifically, male patients are at a higher death risk than female patients, and the older population is significantly more affected than young individuals. Whether this difference is a consequence of a pre-existing differential response to the virus, has not been studied in detail. We created DeCovid, an R shiny app that combines gene expression (GE) data of different human tissue from the Genotype-Tissue Expression (GTEx) project along with the COVID-19 Disease Map and COVID-19 related pathways gene collections to explore basal GE differences across healthy demographic groups. We used this app to study differential gene expression of COVID-19 associated genes in different age and sex groups. We identified that healthy women show higher expression-levels of interferon genes. Conversely, healthy men exhibit higher levels of proinflammatory cytokines. Additionally, young people present a stronger complement system and maintain a high level of matrix metalloproteases than older adults. Our data suggest the existence of different basal immunophenotypes amongst different demographic groups, which are relevant to COVID-19 progression and may contribute to explaining sex and age biases in disease severity. The DeCovid app is an effective and easy to use tool for exploring the GE levels relevant to COVID-19 across demographic groups and tissues.

Diagnostic biomarker candidates for pulpitis revealed by bioinformatics analysis of merged microarray gene expression datasets

Background

Pulpitis is an inflammatory disease, the grade of which is classified according to the level of inflammation. Traditional methods of evaluating the status of dental pulp tissue in clinical practice have limitations. The rapid and accurate diagnosis of pulpitis is essential for determining the appropriate treatment. By integrating different datasets from the Gene Expression Omnibus (GEO) database, we analysed a merged expression matrix of pulpitis, aiming to identify biological pathways and diagnostic biomarkers of pulpitis.

Methods

By integrating two datasets (GSE77459 and GSE92681) in the GEO database using the sva and limma packages of R, differentially expressed genes (DEGs) of pulpitis were identified. Then, the DEGs were analysed to identify biological pathways of dental pulp inflammation with Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis and Gene Set Enrichment Analysis (GSEA). Protein–protein interaction (PPI) networks and modules were constructed to identify hub genes with the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) and Cytoscape.

Results

A total of 470 DEGs comprising 394 upregulated and 76 downregulated genes were found in pulpitis tissue. GO analysis revealed that the DEGs were enriched in biological processes related to inflammation, and the enriched pathways in the KEGG pathway analysis were cytokine-cytokine receptor interaction, chemokine signalling pathway and NF-κB signalling pathway. The GSEA results provided further functional annotations, including complement system, IL6/JAK/STAT3 signalling pathway and inflammatory response pathways. According to the degrees of nodes in the PPI network, 10 hub genes were identified, and 8 diagnostic biomarker candidates were screened: PTPRC, CD86, CCL2, IL6, TLR8, MMP9, CXCL8 and ICAM1.

Conclusions

With bioinformatics analysis of merged datasets, biomarker candidates of pulpitis were screened and the findings may be as reference to develop a new method of pulpitis diagnosis.

Robust expression of SIRT6 inhibits pulpitis via activation of the TRPV1 channel

Invasion of dentinal tubules and pulp tissue by pathogenic bacteria may cause infection leading to pulpitis. Sirtuin 6 (SIRT6) is a NAD-dependent protein deacetylase encoded by the SIRT6 gene. The effect of SIRT6 on lipopolysaccharide (LPS)-induced pulpitis and its mechanism of action were discussed in this study. Dental pulp cells (DPCs) were extracted from human teeth and injected with LPS to induce inflammation. The cells injected with LPS showed substantially decreased expression of SIRT6. The overexpression of SIRT6, induced by plasmid-transfection of DPCs with SIRT6 overexpressing vector, led to a marked decrease in proinflammatory cytokines (IL-6, IL-1β, and TNF-α) and deactivation of NF kappa B pathway. Additionally, dentin matrix protein-1 (DMP1), a promoter of inflammation in dental pulp tissues, was downregulated. Further investigation revealed that SIRT6 promotes ubiquitination of the transient receptor potential vanilloid 1 (TRPV1) channel, leading to its degradation and deactivation. The role of TRPV1 in the anti-inflammatory effects of SIRT6 was determined through incubation of SIRT6-expressing dental pulp stem cells (DPSCs) with capsaicin. This incubation counteracted the effect of SIRT6 on cytokines and DMP1. The injection of lentivirus-SIRT6 attenuated LPS-induced pulpitis in vivo by suppressing TRPV1 activity. Thus, SIRT6 inhibits the TRPV1 channel during LPS-induced inflammation of dental pulp. SIGNIFICANCE OF THE STUDY: This study discussed the effect of sirtuin 6 (SIRT6) on lipopolysaccharide (LPS)-induced pulpitis as well as its mechanism of action and found that SIRT6 may be a negative regulator of pulpitis. Additionally, low expression of SIRT6 and high expression of transient receptor potential vanilloid 1 (TRPV1) in LPS-treated human dental pulp cells are closely associated with proinflammatory cytokines, dentin matrix protein 1 expression, and activation of the NF-κB pathway, which indicated that TRPV1 may be a biomarker for pulpitis and the SIRT6-TRPV1-CGRP axis maybe a clinical target due to their role regulating inflammation and neuropathic pain.

Role(s) of cytokines in pulpitis: Latest evidence and therapeutic approaches

Pulpitis is known as a typical inflammation of dental pulp tissue, and microorganisms of the oral microbiome are involved in this opportunistic infection. Studies indicated that several factors related to host response have a crucial role in pulpitis. Among these factors, inflammatory mediators of the immune system such as cytokines and chemokines contribute to pulpal defense mechanisms. A wide range of cytokines have been observed in dental pulp and these small molecules are able to trigger inflammation and participate in immune cell trafficking, cell proliferation, inflammation, and tissue damage in pulp space. Therefore, the aim of this review was to describe the role of cytokines in the pathogenesis of pulpitis.

Resolvin E1 Ameliorates Pulpitis by Suppressing Dental Pulp Fibroblast Activation in a Chemerin Receptor 23-dependent Manner

INTRODUCTION

Timely resolution of pulp inflammation is a prerequisite for the healing of inflamed dental pulp. Stromal cells, particularly fibroblasts, play a critical role in the inflammation resolution process. Resolvin E1 (RvE1) is a lipid-derived endogenous proresolution molecule that mediates this resolution process. In the present study, we investigated the effects of RvE1 on dental fibroblasts during the pathogenesis of pulpitis.

METHODS

The pulp tissues in maxillary incisors of male Sprague-Dawley rats (N = 50) were exposed to the oral environment for 0, 9, 24, and 48 hours, after which they were treated with RvE1 or its vehicle. The inflammatory changes after 24 hours were assessed using hematoxylin-eosin staining, immunohistochemistry, enzyme-linked immunosorbent assay, and quantitative polymerase chain reaction. Chemerin receptor 23 (ChemR23) expression in rat pulp tissues and human dental fibroblasts was detected by immunofluorescence, Western blot analysis, and quantitative polymerase chain reaction. Finally, small interfering RNA-based knockdown studies were performed to evaluate the effects of RvE1 inhibition on proinflammatory genes and nuclear factor kappa B signaling of human dental pulp fibroblasts.

RESULTS

Early treatment (within 24 hours after pulp exposure) with RvE1 promoted a decline in the number of inflammatory cells and gene expression of proinflammatory cytokines. Moreover, it reduced ChemR23 expression in the fibroblastlike cells of inflamed pulp tissues. In vitro, ChemR23 was widely expressed in human dental fibroblasts. RvE1 significantly suppressed cytokine production by fibroblasts, with down-regulation of the nuclear translocation of nuclear factor kappa B p65 in these cells. Knockdown of ChemR23 almost abolished the anti-inflammatory effect of RvE1.

CONCLUSIONS

RvE1 can suppress the activation of dental pulp fibroblasts in a ChemR23-dependent manner and inhibit inflammation in the relevant early stages of pulpitis.

Interleukin-17 plays a role in pulp inflammation partly by WNT5A protein induction

OBJECTIVE

Our study aimed to investigate the role of interleukin (IL)-17 in dental pulp inflammation and the relationship between WNT5A and IL-17.

METHODS

Immunohistochemical staining was used to detect the expression of tumor necrosis factor-α (TNF-α), WNT5A and IL-17 in pulp tissues. Anti-IL-17 neutralizing antibody was used in rat pulpitis model and to study the role of IL-17 in pulpitis. TNF-α, WNT5A or IL-17 recombinant protein were used to treat human dental pulp cells. RT-PCR, Western blot, and Enzyme linked immunosorbent assay were used to detect the expression of mRNA and protein. Transwell assay was used to measure the migration of THP-1 cells, which is a human monocytic cell line.

RESULTS

IL-17 and WNT5A are co-expressed in TNF-α high-expressed region in human and rat pulpitis tissue. IL-17 mainly contributes to its positive regulatory role in inflammation through up regulate cytokines and mediated macrophages migration. Anti-IL-17 neutralizing antibody can suppress the inflammatory cell infiltration and TNF-α expression in dental pulpitis. TNF-α promotes the expression of IL-17 partly through WNT5A and WNT5A regulates IL-17 expression by mitogen-activated protein kinase (MAPK)-(P38 and ERK) pathway.

CONCLUSIONS

IL-17 acts as an inflammatory mediator in dental pulp inflammation. The expression of IL-17 can be partially regulated by WNT5A.

The Versican G1 Fragment and Serum-Derived Hyaluronan-Associated Proteins Interact and Form a Complex in Granulation Tissue of Pressure Ulcers

The hyaluronan (HA)-rich extracellular matrix plays dynamic roles during tissue remodeling. Versican and serum-derived HA-associated protein (SHAP), corresponding to the heavy chains of inter-α-trypsin inhibitor, are major HA-binding molecules in remodeling processes, such as wound healing. Versican G1-domain fragment (VG1F) is generated by proteolysis and is present in either remodeling tissues or the mature dermis. However, the macrocomplex formation of VG1F has not been clarified. Therefore, we examined the VG1F-containing macrocomplex in pressure ulcers characterized by chronic refractory wounds. VG1F colocalized with SHAP-HA in specific regions of the granulation tissue but not with fibrillin-1. A unique VG1F-SHAP-HA complex was isolated from granulation tissues using gel filtration chromatography and subsequent cesium chloride-gradient ultracentrifugation under dissociating conditions. Consistent with this molecular composition, recombinant versican G1, but not versican G3, interacted with the two heavy chains of inter-α-trypsin inhibitor. The addition of recombinant VG1 in fibroblast cultures enhanced VG1F-SHAP-HA complex deposition in the pericellular extracellular matrix. Comparison with other VG1F-containing macrocomplexes, including dermal VG1F aggregates, versican-bound microfibrils, and intact versican, highlighted the tissue-specific organization of HA-rich extracellular matrix formation containing versican and SHAP. The VG1F-SHAP-HA complex was specifically detected in the edematous granulation tissues of human pressure ulcers and in inflamed stages in a mouse model of moist would healing, suggesting that the complex provides an HA-rich matrix suitable for inflammatory reactions.

Pulp Inflammation Diagnosis from Clinical to Inflammatory Mediators: A Systematic Review

INTRODUCTION

Similar to other tissues, the dental pulp mounts an inflammatory reaction as a way to eliminate pathogens and stimulate repair. Pulp inflammation is prerequisite for dentin pulp complex repair and regeneration; otherwise, chronic disease or pulp necrosis occurs. Evaluation of pulp inflammation severity is necessary to predict the clinical success of maintaining pulp vitality. Clinical limitations to evaluating in situ inflammatory status are well-described. A molecular approach that aids clinical distinction between reversible and irreversible pulpitis could improve the success rate of vital pulp therapy. The aim of this article is to review inflammatory mediator expression in the context of clinical diagnosis.

METHODS

We searched PubMed and Cochrane databases for articles published between 1970 and December 2016. Only published studies of inflammatory mediator expression related to clinical diagnosis were eligible for inclusion and analysis.

RESULTS

Thirty-two articles were analyzed. Two molecular approaches were described by study methods, protein expression analysis and gene expression analysis. Our review indicates that interleukin-8, matrix metalloproteinase 9, tumor necrosis factor-α, and receptor for advanced glycation end products expression increase at both the gene and protein levels during inflammation.

CONCLUSIONS

Clinical irreversible pulpitis is related to specific levels of inflammatory mediator expression. The difference in expression between reversible and irreversible disease is both quantitative and qualitative. On the basis of our analysis, in situ quantification of inflammatory mediators may aid in the clinical distinction between reversible and irreversible pulpitis.

Pulpal Tissue Inflammatory Reactions after Experimental Pulpal Exposure in Mice

INTRODUCTION

The purpose of this study was to establish a stable experimental mice pulpal inflammatory model and to evaluate inflammatory reactions of pulpal tissue after pulpal exposure.

METHODS

Pulpal inflammation was induced in 80 C57BL/6 mice by occlusal exposure of the pulp of the maxillary first molar. The mice were sacrificed randomly at 0, 1, 6, 12, 24, 48, and 72 hours after pulpal exposure. Mice without pulpal exposure served as controls. Maxillary teeth were obtained and prepared for histologic analyses and real-time polymerase chain reaction analyses.

RESULTS

As the duration of pulpal exposure increases, the inflammatory reaction is exacerbated. Within 6 to 12 hours after pulpal exposure, pulp tissues experienced red blood cell extravasation to the destruction of the odontoblast layer. After 24 hours, necrosis was observed in the pulpal tissue; until 72 hours, necrosis spread to the whole coronal pulpal tissue, and a large number of inflammatory cells were found in the radicular pulpal tissue. The results of histomorphologic scores have the same trend; samples from the 72-hour group possessed the highest score followed by samples from other groups (P < .01). The expression levels of inflammatory cytokines increased over the 72 hours, and there was a high rate of inflammatory cytokine expression at 6 and 12 hours after pulpal exposure.

CONCLUSIONS

Our study represents a stable mice model for studying pulpal inflammation in vivo. Mouse pupal inflammation progresses rapidly, with dramatic changes evident in just a few hours.

Polyphosphate-induced matrix metalloproteinase-3-mediated differentiation in rat dental pulp fibroblast-like cells

Inorganic polyphosphate [Poly(P)] induces differentiation of osteoblastic cells. In this study, matrix metalloproteinase (MMP)-3 small interfering RNA (siRNA) was transfected into purified rat dental pulp fibroblast-like cells (DPFCs) to investigate whether MMP-3 activity induced by Poly(P) is associated with cell differentiation into osteogenic cells. Real-time quantitative polymerase chain reaction, western blotting, and an MMP-3 activity assay were used in this study. Poly(P) enhanced expression of mature odontoblast markers dentin sialophosphoprotein (DSPP) and dentin matrix protein (DMP)-1 in DPFCs. These cells also developed an osteogenic phenotype with increased expression of osteocalcin (OC) and osteopontin (OP), high alkaline phosphatase (ALP) activity, and an increased calcification capacity. Poly(P) induced the expression of MMP-3 mRNA and protein, and increased MMP-3 activity. MMP-3 siRNA potently suppressed the expression of osteogenic biomarkers ALP, OC, OP, DSPP, and DMP-1, and blocked osteogenic calcification. Taken together, Poly(P)-induced MMP-3 regulates differentiation of osteogenic cells from DPFCs.

Products of dentin matrix protein-1 degradation by interleukin-1β-induced matrix metalloproteinase-3 promote proliferation of odontoblastic cells

We have previously reported that interleukin (IL)-1β induces matrix metalloproteinase (MMP)-3-regulated cell proliferation in mouse embryonic stem cell (ESC)-derived odontoblast-like cells, suggesting that MMP-3 plays a potentially unique physiological role in regeneration by odontoblast-like cells. MMPs are able to process virtually any component of the extracellular matrix, including collagen, laminin and bioactive molecules. Because odontoblasts produce dentin matrix protein-1 (DMP-1), we examined whether the degraded products of DMP-1 by MMP-3 contribute to enhanced proliferation in odontoblast-like cells. IL-1β increased mRNA and protein levels of odontoblastic marker proteins, including DMP-1, but not osteoblastic marker proteins, such as osteocalcin and osteopontin. The recombinant active form of MMP-3 could degrade DMP-1 protein but not osteocalcin and osteopontin in vitro. The exogenous degraded products of DMP-1 by MMP-3 resulted in increased proliferation of odontoblast-like cells in a dose-dependent manner. Treatment with a polyclonal antibody against DMP-1 suppressed IL-1β-induced cell proliferation to a basal level, but identical treatment had no effect on the IL-1β-induced increase in MMP-3 expression and activity. Treatment with siRNA against MMP-3 potently suppressed the IL-1β-induced increase in DMP-1 expression and suppressed cell proliferation (p < 0.05). Similarly, treatment with siRNAs against Wnt5a and Wnt5b suppressed the IL-1β-induced increase in DMP-1 expression and suppressed cell proliferation (p < 0.05). Rat KN-3 cells, representative of authentic odontoblasts, showed similar responses to the odontoblast-like cells. Taken together, our current study demonstrates the sequential involvement of Wnt5, MMP-3, DMP-1 expression, and DMP-1 degradation products by MMP-3, in effecting IL-1β-induced proliferation of ESC-derived odontoblast-like cells.

Polyphosphate-induced matrix metalloproteinase-3-mediated proliferation in rat dental pulp fibroblast-like cells is mediated by a Wnt5 signaling cascade

Although it is known that inorganic polyphosphate [Poly(P)] induces differentiation of osteoblasts, there are few reports concerning its effects on cell proliferation, especially in fibroblasts. Because we found that Poly(P) stimulates the proliferation of purified rat dental pulp fibroblast-like cells (DPFCs), matrix metalloproteinase (MMP)-3 small interfering RNA (siRNA) was transfected into purified rat DPFCs to investigate whether MMP-3 activity is induced by Poly(P) and/or is associated with cell proliferation in DPFCs. Real-time quantitative polymerase chain reaction, Western blots, an MMP-3 activity assay, and an enzyme-linked immunosorbent assay to assess cell proliferation were used in this study. Poly(P) induced expression of MMP-3 mRNA and protein, and increased MMP-3 activity and cell proliferation. Silencing of MMP-3 expression with siRNA yielded potent and significant suppression of Poly(P)-induced MMP-3 expression and activity, and decreased cell proliferation. Poly(P) also increased mRNA and protein levels of Wnt5 and the Wnt receptor Lrp5/Fzd9. Although exogenous MMP-3 could not induce Wnt5, exogenous Wnt5 was found to increase MMP-3 activity and, interestingly, the proliferation rate of DPFCs. Transfection with Wnt5a siRNA suppressed the Poly(P)-induced increase in MMP-3 expression and suppressed cell proliferation. These results demonstrate the sequential involvement of Wnt5 and MMP-3 in Poly(P)-induced proliferation of DPFCs, and may have relevance in our understanding and ability to improve wound healing following dental pulp injury.

Immune Cells and Molecular Networks in Experimentally Induced Pulpitis

Dental pulp is a dynamic tissue able to resist external irritation during tooth decay by using immunocompetent cells involved in innate and adaptive responses. To better understand the immune response of pulp toward gram-negative bacteria, we analyzed biological mediators and immunocompetent cells in rat incisor pulp experimentally inflamed by either lipopolysaccharide (LPS) or saline solution (phosphate-buffered saline [PBS]). Untreated teeth were used as control. Expression of pro- and anti-inflammatory cytokines, chemokine ligands, growth factors, and enzymes were evaluated at the transcript level, and the recruitment of the different leukocytes in pulp was measured by fluorescence-activated cell-sorting analysis after 3 h, 9 h, and 3 d post-PBS or post-LPS treatment. After 3 d, injured rat incisors showed pulp wound healing and production of reparative dentin in both LPS and PBS conditions, testifying to the reversible pulpitis status of this model. IL6, IL1-β, TNF-α, CCL2, CXCL1, CXCL2, MMP9, and iNOS gene expression were significantly upregulated after 3 h of LPS stimulation as compared with PBS. The immunoregulatory cytokine IL10 was also upregulated after 3 h, suggesting that LPS stimulates not only inflammation but also immunoregulation. Fluorescence-activated cell-sorting analysis revealed a significant, rapid, and transient increase in leukocyte levels 9 h after PBS and LPS stimulation. The quantity of dendritic cells was significantly upregulated with LPS versus PBS. Interestingly, we identified a myeloid-derived suppressor cell–enriched cell population in noninjured rodent incisor dental pulp. The percentage of this population, known to regulate immune response, was higher 9 h after inflammation triggered with PBS and LPS as compared with the control. Taken together, these data offer a better understanding of the mechanisms involved in the regulation of dental pulp immunity that may be elicited by gram-negative bacteria.

Dental Pulp Defence and Repair Mechanisms in Dental Caries

Dental caries is a chronic infectious disease resulting from the penetration of oral bacteria into the enamel and dentin. Microorganisms subsequently trigger inflammatory responses in the dental pulp. These events can lead to pulp healing if the infection is not too severe following the removal of diseased enamel and dentin tissues and clinical restoration of the tooth. However, chronic inflammation often persists in the pulp despite treatment, inducing permanent loss of normal tissue and reducing innate repair capacities. For complete tooth healing the formation of a reactionary/reparative dentin barrier to distance and protect the pulp from infectious agents and restorative materials is required. Clinical and in vitro experimental data clearly indicate that dentin barrier formation only occurs when pulp inflammation and infection are minimised, thus enabling reestablishment of tissue homeostasis and health. Therefore, promoting the resolution of pulp inflammation may provide a valuable therapeutic opportunity to ensure the sustainability of dental treatments. This paper focusses on key cellular and molecular mechanisms involved in pulp responses to bacteria and in the pulpal transition between caries-induced inflammation and dentinogenic-based repair. We report, using selected examples, different strategies potentially used by odontoblasts and specialized immune cells to combat dentin-invading bacteria in vivo.

Interleukin-1β-induced autophagy-related gene 5 regulates proliferation of embryonic stem cell-derived odontoblastic cells

We previously established a method for the differentiation of induced pluripotent stem cells and embryonic stem cells into α2 integrin-positive odontoblast-like cells. We also reported that Wnt5 in response to interleukin (IL)-1β induces matrix metalloproteinase (MMP)-3-regulated cell proliferation in these cells. Our findings suggest that MMP-3 plays a potentially unique physiological role in the generation of odontoblast-like cells under an inflammatory state. Here, we examined whether up-regulation of autophagy-related gene (Atg) 5 by IL-1β was mediated by Wnt5 signaling, thus leading to increased proliferation of odontoblast-like cells. IL-1β increased the mRNA and protein levels of Atg5, microtubule-associated protein 1 light chain (LC3, a mammalian homolog of yeast Atg8) and Atg12. Treatment with siRNAs against Atg5, but not LC3 and Atg12, suppressed the IL-1β-induced increase in MMP-3 expression and cell proliferation. Our siRNA analyses combined with western blot analysis revealed a unique sequential cascade involving Atg5, Wnt5a and MMP-3, which resulted in the potent increase in odontoblastic cell proliferation. These results demonstrate the unique involvement of Atg5 in IL-1β-induced proliferation of embryonic stem cell-derived odontoblast-like cells.

Polyphosphate induces matrix metalloproteinase-3-mediated proliferation of odontoblast-like cells derived from induced pluripotent stem cells

Inorganic polyphosphate [Poly(P)] may represent a physiological source of phosphate and has the ability to induce bone differentiation in osteoblasts. We previously reported that cytokine-induced matrix metalloproteinase (MMP)-3 accelerates the proliferation of purified odontoblast-like cells. In this study, MMP-3 small interfering RNA (siRNA) was transfected into odontoblast-like cells derived from induced pluripotent stem cells to investigate whether MMP-3 activity is induced by Poly(P) and/or is associated with cell proliferation and differentiation into odontoblast-like cells. Treatment with Poly(P) led to an increase in both cell proliferation and additional odontoblastic differentiation. Poly(P)-treated cells showed a small but significant increase in dentin sialophosphoprotein (DSPP) and dentin matrix protein-1 (DMP-1) mRNA expression, which are markers of mature odontoblasts. The cells also acquired additional odontoblast-specific properties including adoption of an odontoblastic phenotype typified by high alkaline phosphatase (ALP) activity and a calcification capacity. In addition, Poly(P) induced expression of MMP-3 mRNA and protein, and increased MMP-3 activity. MMP-3 siRNA-mediated disruption of the expression of these effectors potently suppressed the expression of odontoblastic biomarkers ALP, DSPP, and DMP-1, and blocked calcification. Interestingly, upon siRNA-mediated silencing of MMP-3, we noted a potent and significant decrease in cell proliferation. Using specific siRNAs, we revealed that a unique signaling cascade, Poly(P)→MMP-3→DSPP and/or DMP-1, was intimately involved in the proliferation of odontoblast-like cells.

Cytokines induce MMP-3-regulated proliferation of embryonic stem cell-derived odontoblast-like cells

OBJECTIVES

Matrix metalloproteinase (MMP)-3 expression increases after pulpectomy and accelerates angiogenesis in rat dental pulp by an uncharacterised mechanism. Odontoblasts, a major component of dental pulp, could represent a therapeutic target. We investigated whether MMP-3 activity is induced by cytokines and/or is associated with cell proliferation and apoptosis in embryonic stem cell-derived odontoblast-like cells.

MATERIALS AND METHODS

We used reverse transcriptase polymerase chain reaction, western blotting, an MMP-3 activity assay, a BrdU-cell proliferation enzyme-linked immunosorbent assay and DNA fragmentation analysis to evaluate siRNA-mediated downregulation of MMP-3 expression and activity, and any changes in the proliferative and apoptotic responses associated with this reduced expression.

RESULTS

Pro-inflammatory cytokines (interleukin-1β, tumour necrosis factor-α and interferon-γ, at relatively low concentrations) induced MMP-3 mRNA and protein expression, and increased MMP-3 activity and cell proliferation, but not apoptosis. MMP-3 silencing produced a potent and significant suppression of cytokine-induced MMP-3 expression and activity, decreased cell proliferation and increased apoptosis. These effects were rescued by application of exogenous MMP-3.

CONCLUSIONS

Our results suggest that pro-inflammatory cytokines induce MMP-3-regulated cell proliferation and anti-apoptosis effects in odontoblast-like cells derived from embryonic stem cells, in addition to their well-documented destructive role in inflammation.

Human gingival fibroblasts display a non-fibrotic phenotype distinct from skin fibroblasts in three-dimensional cultures

Scar formation following skin injury can be a major psychosocial and physiological problem. However, the mechanisms of scar formation are still not completely understood. Previous studies have shown that wound healing in oral mucosa is faster, associates with a reduced inflammatory response and results to significantly reduced scar formation compared with skin wounds. In the present study, we hypothesized that oral mucosal fibroblasts from human gingiva are inherently distinct from fibroblasts from breast and abdominal skin, two areas prone to excessive scar formation, which may contribute to the preferential wound healing outcome in gingiva. To this end, we compared the phenotype of human gingival and skin fibroblasts cultured in in vivo-like three-dimensional (3D) cultures that mimic the cells' natural extracellular matrix (ECM) niche. To establish 3D cultures, five parallel fibroblast lines from human gingiva (GFBLs) and breast skin (SFBLs) were seeded in high density, and cultured for up to 21 days in serum and ascorbic acid containing medium to induce expression of wound-healing transcriptome and ECM deposition. Cell proliferation, morphology, phenotype and expression of wound healing and scar related genes were analyzed by real-time RT-PCR, Western blotting and immunocytochemical methods. The expression of a set of genes was also studied in three parallel lines of human abdominal SFBLs. Findings showed that GFBLs displayed morphologically distinct organization of the 3D cultures and proliferated faster than SFBLs. GFBLs expressed elevated levels of molecules involved in regulation of inflammation and ECM remodeling (MMPs) while SFBLs showed significantly higher expression of TGF-β signaling, ECM and myofibroblast and cell contractility-related genes. Thus, GFBLs display an inherent phenotype conducive for fast resolution of inflammation and ECM remodeling, characteristic for scar-free wound healing, while SFBLs have a profibrotic, scar-prone phenotype.

RETRACTED: Proinflammatory cytokines induce stromelysin-1-mediated cell proliferation in dental pulp fibroblast-like cells

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of a member of the author team as it contains fabricated/falsified data. All of the authors except Nobuaki Ozeki and Taiki Hiyama have agreed to retract the article; N Ozeki left Aichi Gakuin University in March 2018 and does not respond to coauthor inquiries. T Hiyama left Aichi Gakuin University and could not be reached.

Extensive serum biomarker analysis in patients with enterohemorrhagic Escherichia coli O111-induced hemolytic-uremic syndrome

Proinflammatory cytokines are related to the pathogenesis of enterohemorrhagic Escherichia coli infection and hemolytic-uremic syndrome (HUS). We employed an antibody array that simultaneously detects 174 serum cytokines. We identified five serum biomarkers, namely insulin growth factor-binding protein-2, angiopoietin-2, soluble interleukin-6 receptor, soluble tumor necrosis factor receptor type II, and matrix metalloprotease protein-3 whose levels increased with the development of HUS. Furthermore, the levels of these cytokines were significantly increased in severe HUS compared with mild HUS. These cytokines might play an important role in the pathogenesis of HUS and may also be used to predict the severity of HUS.