Lipoteichoic acid stimulates the proliferation, migration and cytokine production of adult dental pulp stem cells without affecting osteogenic differentiation

Effects of Staphylococcus aureus on stem cells and potential targeted treatment of inflammatory disorders

Due to the advanced studies on stem cells in developmental biology, the roles of stem cells in the body and their phenotypes in related diseases have not been covered clearly. Meanwhile, with the intensive research on the mechanisms of stem cells in regulating various diseases, stem cell therapy is increasingly being attention because of its effectiveness and safety. As one of the most widely used stem cell in stem cell therapies, hematopoietic stem cell transplantation shows huge advantage in treatment of leukemia and other blood-malignant diseases. Besides, due to the effect of anti-inflammatory and immunomodulatory, mesenchymal stem cells could be a potential therapeutic strategy for variety infectious diseases. In this review, we summarized the effects of Staphylococcus aureus (S. aureus) and its components on different types of adult stem cells and their downstream signaling pathways. Also, we reviewed the roles of different kinds of stem cells in various disease models caused by S. aureus, providing new insights for applying stem cell therapy to treat infectious diseases.

LPS-Induced Neuron Cell Apoptosis through TNF-α and Cytochrome c Expression in Dental Pulp

OBJECTIVES

 Inflammation of the dental pulp tissue caused by bacteria, creating an immunology response of death of the dental pulp, is called apoptosis. The Porphyromonas gingivalis that cause apoptosis is lipopolysaccharide (LPS) through toll-like receptor (TLR) via two different mechanisms, intracellular and extracellular pathways. This study analyzed the role of LPS exposure of neuron cells, tumor necrosis factor-α (TNF-α), and cytochrome c (cyt-c) expression in the dental pulp to predict the possible mechanism of apoptosis.

MATERIALS AND METHODS

 The lower tooth of Sprague Dawley rats was opened and exposed to LPS for 48 hours. Then the neuron cell analyzed histopathology using hematoxylin-eosin, whereas the TNF-α and cyt-c expression with indirect immunohistochemistry using a light microscope. The relationship between neuron cells with TNF-α and cyt-c was analyzed using stepwise regression linear analysis.

RESULT

 The LPS exposure showed a lower number of neuron cells and had a relationship with TNF-α expression but not with cyt-c, while compared with control, both TNF-α and cyt-c expression were higher in neuron cells.

CONCLUSION

 LPS exposure in dental pulp is possible to stimulate the apoptosis process through extracellular pathways marked by higher TNF-α expression.

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

AIM

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

METHODOLOGY

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

RESULTS

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

CONCLUSIONS

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

Toll-like receptor and C-type lectin receptor agonists attenuate osteogenic differentiation in human dental pulp stem cells

BACKGROUND

This study aimed to investigate the effects of various toll-like receptor (TLR) and C-type lectin receptor (CLR) ligands on osteogenic differentiation in human dental pulp stem cells (hDPSCs).

METHODS

hDPSCs were cultured and treated with various concentrations (0.01, 0.1, 1.0, and 10 µg/mL) of TLR or CLR agonists (PG-LPS, E.coli LPS, poly(I:C), Pam3CSK4, Furfurman, and Zymosan). Cell viability was determined by MTT assay. The effects of TLR and CLR agonists on osteogenic differentiation of hDPSCs were measured by alkaline phosphatase (ALP) activity, Alizarin Red S staining, and Von Kossa staining. In addition, the mRNA expression of osteogenesis-related genes (ALP, COL1A1, RUNX2, OSX, OCN and DMP1) was examined by RT-qPCR. A non-parametric analysis was employed for the statistical analyses. The statistically significant difference was considered when p < 0.05.

RESULTS

Treatment with TLR and CLR agonists was associated with an increase in hDPSCs' colony-forming unit ability. Compared with the control group, TLR and CLR agonists significantly inhibited the osteogenic differentiation of hDPSCs by decreasing the ALP activity, mineralised nodule formation, and mRNA expression levels of osteogenesis-related genes (ALP, COL1A1, RUNX2, OSX, OCN and DMP1). The inhibition of TRIF but not Akt signalling rescued the effects of TLR and CLR agonist attenuating hDPSCs' mineralisation.

CONCLUSIONS

The activation of TLRs or CLRs exhibited an inhibitory effect on osteogenic differentiation of hDPSCs via the TRIF-dependent signalling pathway.

Effects of histone acetyltransferase (HAT) and histone deacetylase (HDAC) inhibitors on proliferative, differentiative, and regenerative functions of Toll-like receptor 2 (TLR-2)-stimulated human dental pulp cells (hDPCs)

OBJECTIVES

This in vitro study aimed to modify TLR-2-mediated effects on the paracrine, proliferative, and differentiation potentials of human dental pulp-derived cells using histone acetyltransferase (HAT) and histone deacetylase (HDAC) inhibitors.

MATERIALS AND METHODS

Cell viability was assessed using the XTT assay. Cells were either treated with 10 μg/ml Pam3CSK4 only, or pre-treated with valproic acid (VPA) (3 mM), trichostatin A (TSA) (3 μM), and MG-149 (3 μM) for a total of 4 h and 24 h. Control groups included unstimulated cells and cells incubated with inhibitors solvents only. Transcript levels for NANOG, OCT3-4, FGF-1 and 2, NGF, VEGF, COL-1A1, TLR-2, hβD-2 and 3, BMP-2, DSPP, and ALP were assessed through qPCR.

RESULTS

After 24 h, TSA pre-treatment significantly upregulated the defensins and maintained the elevated pro-inflammatory cytokines, but significantly reduced healing and differentiation genes. VPA significantly upregulated the pro-inflammatory cytokine levels, while MG-149 significantly downregulated them. Pluripotency genes were not significantly affected by any regimen.

CONCLUSIONS

At the attempted concentrations, TSA upregulated the defensins gene expression levels, and MG-149 exerted a remarkable anti-inflammatory effect; therefore, they could favorably impact the immunological profile of hDPCs.

CLINICAL RELEVANCE

Targeting hDPC nuclear function could be a promising option in the scope of the biological management of inflammatory pulp diseases.

Viral Entry Inhibitors Protect against SARS-CoV-2-Induced Neurite Shortening in Differentiated SH-SY5Y Cells

The utility of human neuroblastoma cell lines as in vitro model to study neuro-invasiveness and neuro-virulence of SARS-CoV-2 has been demonstrated by our laboratory and others. The aim of this report is to further characterize the associated cellular responses caused by a pre-alpha SARS-CoV-2 strain on differentiated SH-SY5Y and to prevent its cytopathic effect by using a set of entry inhibitors. The susceptibility of SH-SY5Y to SARS-CoV-2 was confirmed at high multiplicity-of-infection, without viral replication or release. Infection caused a reduction in the length of neuritic processes, occurrence of plasma membrane blebs, cell clustering, and changes in lipid droplets electron density. No changes in the expression of cytoskeletal proteins, such as tubulins or tau, could explain neurite shortening. To counteract the toxic effect on neurites, entry inhibitors targeting TMPRSS2, ACE2, NRP1 receptors, and Spike RBD were co-incubated with the viral inoculum. The neurite shortening could be prevented by the highest concentration of camostat mesylate, anti-RBD antibody, and NRP1 inhibitor, but not by soluble ACE2. According to the degree of entry inhibition, the average amount of intracellular viral RNA was negatively correlated to neurite length. This study demonstrated that targeting specific SARS-CoV-2 host receptors could reverse its neurocytopathic effect on SH-SY5Y.

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

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

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.

Cell Wall Mannan of Candida Attenuates Osteogenic Differentiation by Human Dental Pulp Cells

INTRODUCTION

Candida spp. has recently been introduced to interact with conventional carious bacteria, leading to dental caries progression and virulence ability. Evidence regarding the influence of Candida spp. on human dental pulp cell response remains unknown. This study aimed to investigate the effects of Candida albicans mannans on cytotoxicity, cell proliferation, osteogenic differentiation, and inflammatory-related gene expression in human dental pulp cells (hDPCs).

METHODS

hDPCs were treated with cell wall mannans isolated from C. albicans, Candida krusei, Candida glabrata, Candida tropocalis, Candida parapsilosis, and Candida dubliniensis. Cell viability was performed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay. Osteogenic differentiation- and inflammatory-related gene expression were determined using a real-time polymerase chain reaction. Mineralization was examined using alizarin red S staining.

RESULTS

The treatment of mannans isolated from C. albicans, C. krusei, C. glabrata, C. tropocalis, C. parapsilosis, and C. dubliniensis at concentrations ranging from 10-100 μg/mL did not affect cytotoxicity or cell proliferation. Mannans isolated from C. albicans, C. glabrata, and C. tropocalis significantly attenuated mineralization. However, cell wall mannans isolated from C. krusei, C. parapsilosis, and C. dubliniensis did not significantly influence mineral deposition in hDPCs. C. albicans cell wall mannans significantly attenuated osteogenic differentiation-related gene expression (RUNX2, ALP, and ENPP1). Interestingly, IL12 messenger RNA expression was significantly upregulated when treated with C. albicans cell wall mannans. The addition of recombinant IL12 significantly decreased mineralization in hDPCs.

CONCLUSIONS

C. albicans cell wall mannans attenuated osteogenic differentiation in hDPCs and up-regulated inflammatory-related gene IL12 expression.

PTX3 Protects Intestinal Mucosal Barrier Damage in Sepsis Through Toll-Like Receptor Signaling Pathway

This study aims to confirm the protective effect of Pentraxin 3 (PTX3) on intestinal mucosal barrier damage in sepsis in animal and cell models and explore its mechanism. Analysis of the GSE147775 gene set revealed that the level of PTX3 was upregulated in the lipopolysaccharide (LPS)-induced rat sepsis model. The mice sepsis model was established by cecal ligation perforation (CLP), and the cell inflammation model was induced by LPS. Cell apoptosis and the expression of apoptosis-related protein were detected by flow cytometry and Western blotting. The PTX3 level was significantly upregulated in the mice sepsis model. Intestinal mucosal barrier damage was aggravated and inflammatory factor expression was upregulated after PTX3 downregulation in sepsis mice. After upregulation of PTX3, intestinal mucosal barrier damage was alleviated and inflammatory factor expression was decreased in sepsis mice. Further data mining suggested that the anti-inflammatory effect of PTX3 might be realized through inhibition of the toll-like receptor (TLR) signaling pathway. Moreover, compared with the LPS group, downregulation of PTX3 increased cell apoptosis and the levels of BCL2-associated X (Bax), myeloperoxidase (MPO), tumor necrosis factor-alfa (TNF-α), interleukin 1 beta (IL-1β), and interferon-gamma (IFN-γ), and decreased the levels of B-cell lymphoma-2 (Bcl-2), zona occludens (ZO)-1, and occludin. On the contrary, overexpression of PTX3 reduced cell apoptosis and the levels of Bax, MPO, TNF-α, IL-1β, and IFN-γ. Moreover, downregulation of PTX3 reversed the inhibitive effects on cell apoptosis and inflammation and promotive effects on the levels of Zo-1 and occludin induced by CLI-095 (a TLR signaling pathway inhibitor). In the CLP-induced mice sepsis model and LPS-induced cell inflammation model, PTX3 inhibits inflammatory response and reduces intestinal mucosal barrier damage through the TLR signaling pathway.

G protein-coupled estrogen receptor 1 mediates proliferation and adipogenic differentiation of goat adipose-derived stem cells through ERK1/2-NF-κB signaling pathway

Adipose tissue formation and moderate fat deposition are important for the production performance and eating quality of livestock meats. The self-renewal and adipogenic differentiation of adipose-derived stem cells are responsible for the formation and development of adipose tissue. In addition, estrogen targeting G protein-coupled estrogen receptor 1 (GPER1) has been reported to modulate cell proliferation and differentiation during tissue and organ development. However, the potential correlation among estrogen, GPER1, proliferation, and adipogenic differentiation in goat adipose-derived stem cells (gADSCs) is still unclear. Herein, we demonstrated that 17β-estradiol enhances the proliferative ability of gADSCs, indicated by the increased cell number and cell viability, accompanied by up-regulated expressions of cyclin D1 and PCNA. Meanwhile, the adipogenic differentiation is promoted by 17β-estradiol, supported by higher ccumulation of intracellular lipids and increased expressions of PPARγ, ACC, and FABP4. Notably, these activities are all obviously reduced by administration with GPER1 antagonist G15, but GPER1 agonist G1 enhances cell proliferation and adipogenic differentiation. Moreover, GPER1 silencing diminishes cell proliferation and adipogenic differentiation. In parallel, 17β-estradiol elevates the protein level of nuclear p-p65. Furthermore, the phosphorylation of p65 is enhanced by G1 but inhibited by G15 and GPER1 silencing. In addition, the phosphorylation of p65 is mediated by ERK1/2, suggesting that estrogen targeting GPER1 regulates cell proliferation and adipogenic differentiation of gADSCs through the ERK1/2-NF-κB signaling pathway. This study may provide a strong theoretical basis for improving meat quality, flavor, and cold resistance of livestock.