Regulation of the regenerative activity of dental pulp stem cells from exfoliated deciduous teeth (SHED) of children by TGF-β1 is associated with ALK5/Smad2, TAK1, p38 and MEK/ERK signaling

Inducing cyclooxygenase-2 expression, prostaglandin E2 and prostaglandin F2α production of human dental pulp cells by activation of toll-like receptor-3, mitogen-activated protein kinase kinase/extracellular signal-regulated kinase and p38 signaling

Background/purpose

Bacterial infection was the major etiology for pulpal/root canal infection. This study aimed to investigate the activation of toll-like receptor-3 (TLR) on cyclooxygenase-2 (COX-2) expression and prostaglandin E2 (PGE2) and PGF2α production of human dental pulp cells (HDPCs) and associated signaling.

Materials and methods

HDPCs were exposed to different concentrations of Poly (I:C) (a TLR3 activator). Cell viability was determined by 3- (4,5-Dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay and alkaline phosphatase (ALP) activity was evaluated by ALP staining. Activation of extracellular signal-regulated kinase (ERK) and p38 by Poly (I:C) was determined by immunofluorescent staining. The COX-2 protein expression was analyzed by Western blot. PGE2 and PGF2α production was measured by enzyme-linked immunosorbent assay. The mRNA expression was studied by real-time polymerase-chain reaction. Moreover, HDPCs were exposed to Poly(I:C) with/without U0126 or SB203580 treatment and analysis of COX-2 expression and prostanoid production were conducted.

Results

Poly (I:C) showed little effect on ALP activity, but decreased viability of HDPCs. It stimulated COX-2 mRNA and protein expression. Poly (I:C) induced PGE2 and PGF2α production of HDPCs. Poly (I:C) activated p-ERK, and p-p38 protein expression. Treatment by U0126 (a mitogen-activated protein kinase kinase (MEK)/ERK inhibitor) and SB203580 (a p38 inhibitor) attenuated Poly (I:C)-induced COX-2 mRNA and protein expression as well as PGE2 and PGF2α production.

Conclusion

TLR3 activation is involved in the infection and inflammatory responses of pulp tissues, via MEK/ERK, and p38 signaling to mediate COX-2 expression as well as PGE2 and PGF2α production, contributing to the pathogenesis and progression of pulpal/periapical diseases.

The growth factor multimodality on treating human dental mesenchymal stem cells: a systematic review

BACKGROUND

Ensuring the quantity, quality, and efficacy of human dental mesenchymal stem cells (MSCs) has become an urgent problem as their applications increase. Growth factors (GFs) have low toxicity, good biocompatibility, and regulate stem cell survival and differentiation. They bind to specific receptors on target cells, initiating signal transduction and triggering biological functions. So far, relatively few studies have been conducted to summarize the effect of different GFs on the application of dental MSCs. We have reviewed the literature from the past decade to examine the effectiveness and mechanism of applying one or multiple GFs to human dental MSCs. Our review is based on the premise that a single dental MSC cannot fulfill all applications and that different dental MSCs react differently to GFs.

METHODS

A search for published articles was carried out using the Web of Science core collection and PubMed. The study was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA 2020) guidelines. This review considered studies from 2014 to 2023 that examined the effects of GFs on human dental MSCs. The final selection of articles was made on the 15th of July 2023.

RESULTS

Three thousand eight hundred sixty-seven pieces of literature were gathered for this systematic review initially, only 56 of them were selected based on their focus on the effects of GFs during the application of human dental MSCs. Out of the 56, 32 literature pieces were focused on a single growth factor while 24 were focused on multiple growth factors. This study shows that GFs can regulate human dental MSCs through a multi-way processing manner.

CONCLUSION

Multimodal treatment of GFs can effectively regulate human dental MSCs, ensuring stem cell quality, quantity, and curative effects.

Epithelial-specific deletion of FAM20A leads to short root defects

Short Root Defects defined by a reduced ratio of root to crown, may culminate in root resorption and subsequent tooth loss, in spite of the absence of apparent symptoms. Such defects present considerable impediments to orthodontic treatment and restoration. Recent identification of Fam20a, an emergent pseudokinase, has been associated with enamel development and tooth eruption, yet its definitive role in root formation and eruption remains ambiguous. In this research, we initially ascertained that the targeted knockout of Fam20a within the epithelium led to truncated tooth roots, irregular breaks in the epithelial root sheath initiation of the WNT signaling pathway, and decreased expression of the cell polarity-related transcription factor Cdc42 in murine models. This was concomitant with the participation of the associated epithelial root sheath developmental pathways BMP2, Gli1, and Nfic. Furthermore, we observed that Fam20a predominantly affects the intraosseous eruption phase of tooth emergence. During this phase, the osteoclast peak around the mandibular first molar in cKO mice is delayed, leading to a slower formation of the eruption pathway, ultimately resulting in delayed tooth eruption in mice. The findings of this study enrich the extant knowledge regarding the role of Fam20a, suggesting its potential regulatory function in tooth root development through the WNT/β-catenin/Cdc42 pathway.

Hopes and opportunities of stem cells from human exfoliated deciduous teeth (SHED) in cartilage tissue regeneration

Cartilage lesions are common conditions, affecting elderly and non-athletic populations. Despite recent advances, cartilage regeneration remains a major challenge today. The absence of an inflammatory response following damage and the inability of stem cells to penetrate into the healing site due to the absence of blood and lymph vessels are assumed to hinder joint repair. Stem cell-based regeneration and tissue engineering have opened new horizons for treatment. With advances in biological sciences, especially stem cell research, the function of various growth factors in the regulation of cell proliferation and differentiation has been established. Mesenchymal stem cells (MSCs) isolated from different tissues have been shown to increase into therapeutically relevant cell numbers and differentiate into mature chondrocytes. As MSCs can differentiate and become engrafted inside the host, they are considered suitable candidates for cartilage regeneration. Stem cells from human exfoliated deciduous teeth (SHED) provide a novel and non-invasive source of MSCs. Due to their simple isolation, chondrogenic differentiation potential, and minimal immunogenicity, they can be an interesting option for cartilage regeneration. Recent studies have reported that SHED-derived secretome contains biomolecules and compounds that efficiently promote regeneration in damaged tissues, including cartilage. Overall, this review highlighted the advances and challenges of cartilage regeneration using stem cell-based therapies by focusing on SHED.

Inducing cathepsin L expression/production, lysosomal activation, and autophagy of human dental pulp cells by dentin bonding agents, camphorquinone and BisGMA and the related mechanisms

Camphorquinone (CQ) and resin monomers are included in dentin bonding agents (DBAs) and composite resin to restore tooth defects due to abrasion, crown fracture, or dental caries. DBAs, CQ, and bisphenol A-glycidyl methacrylate (BisGMA) applications influence the biological activities of the dental pulp. The current investigation aimed to delineate the effect of DBAs, CQ, and BisGMA on cathepsin L production/expression, lysosomal activity, and autophagy induction in human dental pulp cells (HDPCs). HDPCs were exposed to DBAs, CQ, or BisGMA with/without inhibitors for 24 h. Enzyme-linked immunosorbent assay was employed to determine the cathepsin L level in culture medium. The cell layer was utilized to measure cell viability by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl -tetrazolium bromide (MTT) assay. Real-time PCR was used to evaluate the mRNA expression. Western blotting or immunofluorescent staining was used to study protein expression. Lysosomal density was evaluated by lysotracker red staining. We found that DBAs, CQ, and BisGMA stimulated cathepsin L mRNA, protein expression, and production in HDPCs. In addition, CQ and BisGMA induced lysosomal activity, Beclin1, ATG12, LC3B, Bax, and p53 expression in HDPCs, indicating the stimulation of autophagy. Glutathione (GSH) prevented CQ- and BisGMA-induced cytotoxicity. Moreover, E64d, cathepsin L inhibitor (two cathepsin inhibitors), and Pifithrin-α (a p53 inhibitor) showed little preventive effect toward CQ- and BisGMA-induced cytotoxicity. Autophagy inhibitors (NH4Cl, Lys05) mildly enhanced the CQ- and BisGMA-induced cytotoxicity. These results indicate that DBAs stimulated cathepsin L, possibly due to their content of CQ and BisGMA that may induce cathepsin L in HDPCs. CQ and BisGMA stimulated lysosomal activity, autophagy, and apoptosis, possibly via induction of Beclin 1, ATG12, LC-3B, Bax, and p53 expression. In addition, CQ and BisGMA cytotoxicity was related to redox change and autophagy. These events are important role in pulpal changes after the restoration of tooth decay using CQ- and BisGMA-containing DBAs and resin composite.

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

BACKGROUND/PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Multiple growth factors accommodated degradable submicron calcium sulfate hemihydrate/porous hydroxyapatite for dentin-pulp regeneration

Vital pulp therapy (VPT) has gained significant consideration by utilizing the natural healing capacity of the inflamed pulp in healing process. However, the protective pulp capping materials that facilitate this healing process are still under investigation for the successful promotion of dentin-pulp regeneration. Herein, we developed a bioactive and biodegradable pulp capping material (denoted as sCSHA-GFs) by synthesizing inorganic submicron calcium sulfate hemihydrate (sCS)/porous hydroxyapatite (HA) loaded with growth factors (GFs) such as transforming growth factor-beta 1 (TGF-β1), fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor (VEGF). Physiochemical characteristics of submicron CSHA-GFs (sCSHA-GFs) cement were determined. Human dental pulp stem cells (hDPSCs) were used for analyzing their biocompatibility and bioactivity for dentin mineralization. To evaluate the efficacy of sCSHA-GFs, we compared it with a commercial material, mineral trioxide aggregate (MTA), the reference standard used clinically on pulp capping. Our results showed that sCSHA-GFs cement presented good biodegradability with dissolution properties for sustained release of calcium (Ca²⁺) ions and GFs, and facilitated attachment, proliferation, differentiation and migration of hDPSCs. In addition, sCSHA-GFs cement was found to be more effective than MTA at prolonged incubation time in inducing the mRNA expression levels of odontoblastic differentiation markers, dentin sialophosphoprotein (DSPP) and dentin matrix protein (DMP-1), leading to increased mineralization (with calcium deposits) along with increased alkaline phosphatase (ALP) expressions, evident from Alizarin Red S and ALP staining assays. Our findings suggest that sCSHA-GFs cement may act as a suitable material in VPT for dentin-pulp regeneration.

MiR-335-3p/miR-155-5p Involved in IGFBP7-AS1-Enhanced Odontogenic Differentiation

BACKGROUND

The differentiation of stem cells from exfoliated deciduous teeth (SHEDs) into odontoblasts determines the regeneration of dentin-pulp complex. Non-coding RNAs (ncRNAs), including microRNA (miRNA) and long non-coding RNA (lncRNA), participate in many multiple biological processes, but the specific miRNAs involved in odontogenesis are incompletely defined. It was confirmed that lncRNA IGFBP7-AS1 could positively regulate odontogenetic differentiation in SHEDs. To investigate the downstream mechanisms of this process, miR-335-3p and miR-155-5p were found to be closely related with SHED odontogenic differentiation through whole-genome sequencing. The aim of the current study was to determine the role of miR-335-3p/miR-155-5p in IGFBP7-AS1-enhanced SHED differentiation and explore the potential mechanism of IGFBP7-AS1-mediated odontogenesis.

METHODS

Putative miR-335-3p/miR-155-5p binding sites within IGFBP7-AS1 were identified by bioinformatics analysis, and the binding of miR-335-3p/miR-155-5p to these sites was confirmed by dual-luciferase reporter gene assays. The effects of miR-335-3p/miR-155-5p in odontogenesis were detected by tissue nonspecific alkaline phosphatase staining, Alizarin red staining, quantitative real-time polymerase chain reaction (qRT-PCR) analyses, and western blot testing. The molecular mechanisms of miR-335-3p/miR-155-5p involved in IGFBP7-AS1-mediated odontogenesis were analysed by qRT-PCR and western blot testing.

RESULTS

Dual-luciferase reporter gene assays showed that miR-335-3p/miR-155-5p could directly bind to IGFBP7-AS1. MiR-335-3p and miR-155-5p both could down-regulate dentin sialophosphoprotein expression, and both miRNAs could inhibit IGFBP7-AS1-mediated SHED odontogenetic differentiation via suppression of the extracellular signal-regulated kinase (ERK) pathway.

CONCLUSIONS

Both miR-335-3p and miR-155-5p were negative regulators to IGFBP7-AS1-enhanced odontogenic differentiation of SHED through suppression of the ERK pathway.

Bone morphogenetic protein 7 mediates stem cells migration and angiogenesis: therapeutic potential for endogenous pulp regeneration

Pulp loss is accompanied by the functional impairment of defense, sensory, and nutrition supply. The approach based on endogenous stem cells is a potential strategy for pulp regeneration. However, endogenous stem cell sources, exogenous regenerative signals, and neovascularization are major difficulties for pulp regeneration based on endogenous stem cells. Therefore, the purpose of our research is to seek an effective cytokines delivery strategy and bioactive materials to reestablish an ideal regenerative microenvironment for pulp regeneration. In in vitro study, we investigated the effects of Wnt3a, transforming growth factor-beta 1, and bone morphogenetic protein 7 (BMP7) on human dental pulp stem cells (h-DPSCs) and human umbilical vein endothelial cells. 2D and 3D culture systems based on collagen gel, matrigel, and gelatin methacryloyl were fabricated to evaluate the morphology and viability of h-DPSCs. In in vivo study, an ectopic nude mouse model and an in situ beagle dog model were established to investigate the possibility of pulp regeneration by implanting collagen gel loading BMP7. We concluded that BMP7 promoted the migration and odontogenic differentiation of h-DPSCs and vessel formation. Collagen gel maintained the cell adhesion, cell spreading, and cell viability of h-DPSCs in 2D or 3D culture. The transplantation of collagen gel loading BMP7 induced vascularized pulp-like tissue regeneration in vivo. The injectable approach based on collagen gel loading BMP7 might exert promising therapeutic application in endogenous pulp regeneration.

BMP7 as a regenerative signaling molecule mediates stem cell migration and odontoblastic differentiation (a) and as a pro-angiogenic factor promotes revascularization of endothelial cells (b). Collagen gel supports cell adhesion, spreading, and viability (c).

Biomolecule-Mediated Therapeutics of the Dentin–Pulp Complex: A Systematic Review

The aim of this systematic review was to evaluate the application of potential therapeutic signaling molecules on complete dentin-pulp complex and pulp tissue regeneration in orthotopic and ectopic animal studies. A search strategy was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement in the MEDLINE/PubMed database. Animal studies evaluating the application of signaling molecules to pulpectomized teeth for pulp tissue or dentin-pulp complex regeneration were included. From 2530 identified records, 18 fulfilled the eligibility criteria and were subjected to detailed qualitative analysis. Among the applied molecules, basic fibroblast growth factor, vascular endothelial growth factor, bone morphogenetic factor-7, nerve growth factor, and platelet-derived growth factor were the most frequently studied. The clinical, radiographical and histological outcome measures included healing of periapical lesions, root development, and apical closure, cellular recolonization of the pulp space, ingrowth of pulp-like connective tissue (vascularization and innervation), mineralized dentin-like tissue formation along the internal dentin walls, and odontoblast-like cells in contact with the internal dentin walls. The results indicate that signaling molecules play an important role in dentin/pulp regeneration. However, further studies are needed to determine a more specific subset combination of molecules to achieve greater efficiency towards the desired tissue engineering applications.

bFGF stimulated plasminogen activation factors, but inhibited alkaline phosphatase and SPARC in stem cells from apical Papilla: Involvement of MEK/ERK, TAK1 and p38 signaling

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bFGF induced uPA, uPAR, PAI-1 production/expression in SCAP →

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bFGF induced decline of ALP and SPARC of SCAP →

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The effects of bFGF are regulated by ERK, p38, TAK1 and Akt signaling →

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Crucial for SCAP proliferation, matrix turnover and differentiation →

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These events are important for revascularization/root apexogenesis

Introduction

Objectives

Methods

Results

Conclusion

Direct effect of transforming growth factor-beta 1 (TGF-β1) on human apical papilla cell proliferation and mineralisation

Firstly, this study investigated the direct effect of Transforming Growth Factor-beta 1 at 10, 5, 2.5 and 1.25 ng mL^-1 on human apical papilla cell proliferation and mineralisation. Cell proliferation was examined at 0, 2, 4, 6, 24, 48, 72, 96 and 120 h using Alamar Blue^TM assay. Cell mineralisation was examined at day 21 with a quantitative Alizarin Red S staining. Secondly, the study aimed to estimate the amount of Transforming Growth Factor-beta 1 (TGF-β1) released from the dentin after root canal irrigation. The solution collected from a root canal after rinsing with various protocols (normal saline solution, ethylenediaminetetraacetic acid or chlorhexidine) was analysed with an enzyme-linked immunosorbent assay. Data were statistically analysed using a one-way analysis of variance. The results, from the first part, revealed cell proliferation reduction in all experimental groups presented with TGF-β1. The higher concentration generated more deteriorating effects. Cell mineralisation was highest in a group with TGF-β1 at 1.25 ng mL^-1 (P < 0.05). For the growth factor released from dentin, the highest amount was detected only when ethylenediaminetetraacetic acid was associated with the irrigation (P < 0.05). In summary, the direct effects of TGF-β1 on cell proliferation and differentiation were diverse, depending on concentration. The release of TGF-β1 from root dentin can be achieved after rinsing with ethylenediaminetetraacetic acid.

Effect of butyrate, a bacterial by-product, on the viability and ICAM-1 expression/production of human vascular endothelial cells: Role in infectious pulpal/periapical diseases

AIM

To investigate the effects of butyric acid (BA), a metabolic product generated by pulp and root canal pathogens, on the viability and intercellular adhesion molecule-1 (ICAM-1) production of endothelial cells, which are crucial to angiogenesis and pulpal/periapical wound healing.

METHODOLOGY

Endothelial cells were exposed to butyrate with/without inhibitors. Cell viability, apoptosis and reactive oxygen species (ROS) were evaluated using an MTT assay, PI/annexin V and DCF fluorescence flow cytometry respectively. RNA and protein expression was determined using a polymerase chain reaction assay and Western blotting or immunofluorescent staining. Soluble ICAM-1 (sICAM-1) was measured using an enzyme-linked immunosorbent assay. The quantitative results were expressed as mean ± standard error (SE) of the mean. The data were analysed using a paired Student's t-test where necessary. A p-value ≤0.05 was considered to indicate a statistically significant difference between groups.

RESULTS

Butyrate (>4 mM) inhibited cell viability and induced cellular apoptosis and necrosis. It inhibited cyclin B1 but stimulated p21 and p27 expression. Butyrate stimulated ROS production and hemeoxygenase-1 (HO-1) expression as well as activated the Ac-H3, p-ATM, p-ATR, p-Chk1, p-Chk2, p-p38 and p-Akt expression of endothelial cells. Butyrate stimulated ICAM-1 mRNA/protein expression and significant sICAM-1 production (p < .05). Superoxide dismutase, 5z-7oxozeaenol, SB203580 and compound C (p <  .05), but not ZnPP, CGK733, AZD7762 or LY294002, attenuated butyrate cytotoxicity to endothelial cells. Notably, little effect on butyrate-stimulated sICAM-1 secretion was found. Valproic acid, phenylbutyrate and trichostatin (three histone deacetylase inhibitors) significantly induced sICAM-1 production (p < .05).

CONCLUSION

Butyric acid inhibited proliferation, induced apoptosis, stimulated ROS and HO-1 production and increased ICAM-1 mRNA expression and protein synthesis in endothelial cells. Cell viability affected by BA was diminished by some inhibitors; however, the increased sICAM-1 secretion by BA was not affected by any of the tested inhibitors. These results facilitate understanding of the pathogenesis, prevention and treatment of pulpal/periapical diseases.