Mineral trioxide aggregate enhances the osteogenic capacity of periodontal ligament stem cells via NF-κB and MAPK signaling pathways

Isoliquiritin treatment of osteoporosis by promoting osteogenic differentiation and autophagy of bone marrow mesenchymal stem cells

Osteoporosis is a chronic progressive bone disease characterized by the decreased osteogenic ability of osteoblasts coupled with increased osteoclast activity. Natural products showing promising therapeutic potential for postmenopausal osteoporosis remain underexplored. In this study, we aimed to analyze the therapeutic effects of isoliquiritin (ISL) on osteoporosis in mice and its possible mechanism of action. An ovariectomy-induced osteoporosis mouse model and bone marrow mesenchymal stem cells (BMSCs) were used to analyze the effects of ISL on bone regeneration in vivo and in vitro, respectively. Mitogen-activated protein kinase (MAPK) and autophagy inhibitors were used, to investigate whether the MAPK signaling pathway and autophagy affect the osteogenic differentiation of BMSCs. ISL significantly improved bone formation and reduced bone resorption in mouse femurs without inducing any detectable toxicity in critical organs such as the liver, kidney, brain, heart, and spleen. In vitro experiments showed that ISL enhanced the proliferation and osteogenic differentiation of BMSCs and that its osteogenic effect was attenuated by p38/extracellular regulated protein kinase (ERK) and autophagy inhibitors. Further studies showed that the inhibition of phosphorylated p38/ERK blocked ISL autophagy in BMSCs. ISL promoted the osteogenic differentiation of BMSCs through the p38/ERK-autophagy pathway and was therapeutically effective in treating osteoporosis in ovariectomized mice without any observed toxicity to vital organs. These results strongly suggest the promising potential of ISL as a safe and efficacious candidate drug for the treatment of osteoporosis.

Comparative Biocompatibility and Odonto-/Osteogenesis Effects of Hydraulic Calcium Silicate-Based Cements in Simulated Direct and Indirect Approaches for Regenerative Endodontic Treatments: A Systematic Review

BACKGROUND

Regenerative dentistry is the operation of restoring dental, oral and maxillofacial tissues. Currently, there are no guidelines for the ideal cement/material in regenerative endodontic treatments (RET). Hydraulic calcium silicate-based cements (hCSCs) are currently the material of choice for RET.

OBJECTIVES

This systematic review was conducted to gather all of the different direct and indirect approaches of using hCSCs in RET in vitro and in vivo, and to ascertain if there are any superiorities to indirect approaches.

METHODS AND MATERIALS

This systematic review was conducted according to the 2020 PRISMA guidelines. The study question according to the PICO format was as follows: Comparison of the biological behavior (O) of stem cells (P) exposed to hCSCs through direct and indirect methods (I) with untreated stem cells (C). An electronic search was executed in Scopus, Google Scholar, and PubMed.

RESULTS

A total of 78 studies were included. Studies were published between 2010 and 2022. Twenty-eight commercially available and eighteen modified hCSCs were used. Seven exposure methods (four direct and three indirect contacts) were assessed. ProRoot MTA and Biodentine were the most used hCSCs and had the most desirable results. hCSCs were either freshly mixed or set before application. Most studies allowed hCSCs to set in incubation for 24 h before application, which resulted in the most desirable biological outcomes. Freshly mixed hCSCs had the worst outcomes. Indirect methods had significantly better viability/proliferation and odonto-/osteogenesis outcomes.

CONCLUSION

Biodentine and ProRoot MTA used in indirect exposure methods result in desirable biological outcomes.

Immunomodulatory Effects of Endodontic Sealers: A Systematic Review

Inflammation is a crucial step prior to healing, and the regulatory effects of endodontic materials on the immune response can influence tissue repair. This review aimed to answer whether endodontic sealers can modulate the immune cells and inflammation. An electronic search in Scopus, Web of Science, PubMed, and Google Scholar databases were performed. This systematic review was mainly based on PRISMA guidelines, and the risk of bias was evaluated by SYRCLEs and the Modified CONSORT checklist for in vivo and in vitro studies, respectively. In total, 28 articles: 22 in vitro studies, and six in vivo studies were included in this systematic review. AH Plus and AH 26 can down-regulate iNOS mRNA, while S-PRG sealers can down-regulate p65 of NF-κB pathways to inhibit the production of TNF-α, IL-1, and IL-6. In vitro and in vivo studies suggested that various endodontic sealers exhibited immunomodulatory impact in macrophages polarization and inflammatory cytokine production, which could promote healing, tissue repair, and inhibit inflammation. Since the paradigm change from immune inert biomaterials to bioactive materials, endodontic materials, particularly sealers, are required to have modulatory effects in clinical conditions. New generations of endodontic sealers could hamper detrimental inflammatory responses and maintain periodontal tissue, which represent a breakthrough in biocompatibility and functionality of endodontic biomaterials.

Are Endodontic Solvents Cytotoxic? An In Vitro Study on Human Periodontal Ligament Stem Cells

The aim of this study was to assess the influence of eucalyptol, chloroform, and Endosolv on the proliferative capability, cell viability, and migration rates of human periodontal ligament stem cells (hPDLSCs) in vitro. Solvent eluates were formulated following ISO 10993-5 guidelines, and 1%, 0.25%, and 0.1% dilutions were prepared. The HPDLSCs were isolated from the extracted third molars of healthy donors. The following parameters were assessed: cell viability via trypan blue and IC50 assays, cell migration via horizontal wound healing assay, cell morphology via cell cytoskeleton staining (phalloidin labeling), and cell oxidative stress via reactive oxygen species assay. The data were analyzed using one-way ANOVA and Tukey’s posthoc tests, and their significance was established at p < 0.05. Chloroform and eucalyptol exhibited significantly higher cytotoxicity on the hPDLSCs in vitro compared to the control group, as shown by the cell viability, migration, morphology, and reactive oxygen species release assays. Alternatively, Endosolv showed adequate cytotoxicity levels comparable to those of the control group. The cytotoxicity of the tested endodontic solvents increased in a dose-dependent manner. The results from the present study highlight the cytotoxicity of chloroform and eucalyptol. Thus, their limited and cautious use is recommended, avoiding solvent extrusion.

Nano-Based Drug Delivery Systems for Periodontal Tissue Regeneration

Periodontitis is a dysbiotic biofilm-induced and host-mediated inflammatory disease of tooth supporting tissues that leads to progressive destruction of periodontal ligament and alveolar bone, thereby resulting in gingival recession, deep periodontal pockets, tooth mobility and exfoliation, and aesthetically and functionally compromised dentition. Due to the improved biopharmaceutical and pharmacokinetic properties and targeted and controlled drug release, nano-based drug delivery systems have emerged as a promising strategy for the treatment of periodontal defects, allowing for increased efficacy and safety in controlling local inflammation, establishing a regenerative microenvironment, and regaining bone and attachments. This review provides an overview of nano-based drug delivery systems and illustrates their practical applications, future prospects, and limitations in the field of periodontal tissue regeneration.

Trends of calcium silicate biomaterials in medical research and applications: A bibliometric analysis from 1990 to 2020

Background: Calcium silicate biomaterials (CSB) have witnessed rapid development in the past 30 years. This study aimed to accomplish a comprehensive bibliometric analysis of the published research literature on CSB for biomedical applications and explore the research hotspot and current status.

Methods: Articles related to CSB published in the last three decades (1990–2020) were retrieved from Web of Science Core Collection. The R bibliometrix package and VOSviewer were used to construct publication outputs and collaborative networking among authors, their institutes, countries, journals’ matrices and keywords plus.

Results: A total of 872 publications fulfilling the search criteria were included. CSB is mainly reported for bone tissues and dental applications. Among researchers, Chang J from Chinese Academy of Sciences and Gandolfi MG from the University of Bologna are the most productive author in these two fields, respectively. China was the leading contributor to the research on CSB in the medical field. A total of 130 keywords appeared more ten or more times were identified. The term “mineral trioxide aggregate” ranked first with 268 occurrences. The co-occurrence analysis identified three major clusters: CSB in dentistry, bone tissue and vitro bioactivity.

Conclusion: Calcium silicate biomaterials have a promising scope for various biomedical applications ranging from regeneration of hard tissues (bone and teeth) to skin, tumor, cardiac muscle and other soft tissues. This study may help researchers further understand the frontiers of the field.

Metformin combats high glucose-induced damage to the osteogenic differentiation of human periodontal ligament stem cells via inhibition of the NPR3-mediated MAPK pathway

Background

High glucose-induced damage to the osteogenic differentiation of human periodontal ligament stem cells (PDLSCs) has long been a challenge to periodontal regeneration for diabetic individuals. Metformin is an anti-hyperglycemic drug that exhibits abundant biological activities associated with cell metabolism and downstream tissue regeneration. However, how metformin combats damage to PDLSC osteogenic differentiation under high glucose and the underlying mechanisms remain unknown.

Methods

Osteogenic differentiation of PDLSCs was assessed by alkaline phosphatase (ALP) staining, ALP activity, Alizarin Red staining and quantitative assay, quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot analysis. RNA-seq analysis was performed to screen target genes of metformin, and the effects of target genes were confirmed using lentivirus transfection. Western blot analysis was also used to detect the protein level of underlying signaling pathways.

Results

We found that osteogenic differentiation of PDLSCs under high glucose was decreased, and metformin addition enhanced this capacity of differentiation. Furthermore, the results of RNA-seq analysis showed that natriuretic peptide receptor 3 (NPR3) was upregulated in PDLSCs under high glucose and downregulated after metformin addition. When the underlying pathways involved were investigated, we found that upregulation of NPR3 can compromise the metformin-enhanced PDLSC osteogenic differentiation and activate the MAPK pathway (especially the p38 MAPK and Erk1/2 pathway), and that inhibition of the NPR3-mediated p38 MAPK or Erk1/2 pathway enhanced the osteogenic differentiation of PDLSCs under high glucose.

Conclusions

The present study suggests that metformin may enhance the osteogenic differentiation of PDLSCs under high glucose via downregulation of NPR3 and inhibition of its downstream MAPK pathway. This is the first report identifying the involvement of NPR3-mediated MAPK pathway in the metformin-enhanced osteogenic differentiation, indicating that NPR3 antagonists, such as metformin, may be feasible therapeutics for periodontal tissue regeneration in diabetic individuals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02992-z.

PD-1 suppresses the osteogenic and odontogenic differentiation of stem cells from dental apical papilla via targeting SHP2/NF-κB axis

Stem cells from the apical papilla (SCAPs) are important for tooth root development and regeneration of root dentin. Here, we examined the expression of programmed cell death protein-1 (PD-1) in SCAPs and investigated the effect of PD-1 on odontogenic and osteogenic differentiation and the relationship between PD-1 and SHP2/NF-κB signals. SCAPs were obtained and cultured in the related medium. The proliferation ability was evaluated by cell counting kit 8 (CCK-8) and 5-ethynyl-20-deoxyuridine (EdU) assay. Alkaline phosphatase (ALP) activity assay, ALP staining, western blot, real time quantitative reverse-transcription polymerase chain reaction (RT-qPCR), Alizarin Red S (ARS) staining, and immunofluorescence (IF) staining were performed to explore the osteo/odontogenic potential and the involvement of SHP2/NF-κB pathways. Besides, we transplanted SCAPs component into mouse calvaria defects to evaluate osteogenesis in vivo. We found that human SCAPs expressed PD-1 for the first time. PD-1 knockdown enhanced the osteo/odontogenic differentiation of SCAPs by suppressing SHP2 pathway and activating NF-κB pathway. Overexpression of PD-1 inhibited the osteogenesis and odontogenesis of SCAPs via activation of SHP2 signal and inhibition of NF-κB pathway. PD-1 activated SHP2 signal to block NF-κB signal and then played a vital role in osteo/odontogenic differentiation of SCAPs.

Biological interactions between calcium silicate-based endodontic biomaterials and periodontal ligament stem cells: A systematic review of in vitro studies

BACKGROUND

Most recently, the biological interactions, that is cytocompatibility, cell differentiation and mineralization potential, between calcium silicate-based biomaterials and periodontal ligament stem cells (PDLSCs) have been studied at an in vitro level, in order to predict their clinical behaviour during endodontic procedures involving direct contact with periodontal tissues, namely root canal treatment, endodontic surgery and regenerative endodontic treatment.

OBJECTIVE

The aim of the present systematic review was to present a qualitative synthesis of available in vitro studies assessing the biological interaction of PDLSCs and calcium silicate-based biomaterials.

METHODOLOGY

The present review followed PRISMA 2020 guidelines. An advanced database search was performed in Medline, Scopus, Embase, Web of Science and SciELO on 1 July 2020 and last updated on 22 April 2021. Studies assessing the biological interactions of PDLSCs with calcium silicate-based sealers (CSSs) and/or cements (CSCs) at an in vitro level were considered for inclusion. The evaluation of the 'biological interaction' was defined as any assay or test on the cytotoxicity, cytocompatibility, cell plasticity or differentiation potential, and bioactive properties of PDLSCs cultured in CSC or CSS-conditioned media. Quality (risk of bias) was assessed using a modified CONSORT checklist for in vitro studies of dental materials.

RESULTS

A total of 20 studies were included for the qualitative synthesis. CSCs and CSSs, as a group of endodontic materials, exhibit adequate cytocompatibility and favour the osteo/cementogenic differentiation and mineralization potential of PDLSCs, as evidenced from the in vitro studies included in the present systematic review.

DISCUSSION

The influence of the compositional differences, inclusion of additives, sample preparation, and varying conditions and manipulations on the biological properties of calcium silicate-based materials remain a subject for future research.

CONCLUSIONS

Within the limitations of the in vitro nature of the included studies, this work supports the potential use of calcium silicate-based endodontic materials in stem cell therapy and biologically based regenerative endodontic procedures.

REGISTRATION

OSF Registries; https://doi.org/10.17605/OSF.IO/SQ9UY.

In vitro biocompatibility and bioactivity of calcium silicate‑based bioceramics in endodontics (Review)

Calcium silicate-based bioceramics have been applied in endodontics as advantageous materials for years. In addition to excellent physical and chemical properties, the biocompatibility and bioactivity of calcium silicate-based bioceramics also serve an important role in endodontics according to previous research reports. Firstly, bioceramics affect cellular behavior of cells such as stem cells, osteoblasts, osteoclasts, fibroblasts and immune cells. On the other hand, cell reaction to bioceramics determines the effect of wound healing and tissue repair following bioceramics implantation. The aim of the present review was to provide an overview of calcium silicate-based bioceramics currently applied in endodontics, including mineral trioxide aggregate, Bioaggregate, Biodentine and iRoot, focusing on their in vitro biocompatibility and bioactivity. Understanding their underlying mechanism may help to ensure these materials are applied appropriately in endodontics.

Comparison of in vitro biocompatibility and antibacterial activity of two calcium silicate-based materials

This study is aimed at comparing and evaluating the biocompatibility and antibacterial activities of mineral trioxide aggregate (MTA) and iRoot BP Plus as novel retro-filling materials. Discs of both materials were prepared and incubated for 72 h to obtain material extracts in medium. Flow cytometry and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay were used to assess the rate of apoptosis and proliferation of human periodontal ligament stem cells (hPDLSCs) when exposed to eluates of both materials. The expression levels of alkaline phosphatase, collagen type I, osteocalcin, Runt-related transcription factor-2, and Osterix were tested for evaluating the osteogenic differentiation of hPDLSCs. The antibacterial activities of both materials were compared by the direct contact test. The hPDLSCs stimulated by MTA or iRoot BP Plus eluates showed significantly higher cell viability than that of the control group with no eluates. No significant differences were observed among the percentages of necrotic and apoptotic cells stimulated by MTA and iRoot BP Plus eluates and the control group. The expression of all osteogenic differentiation markers of hPDLSCs in both experimental groups were significantly higher than those of the control group, while the increment values in MTA group were significantly higher than those of the iRoot BP Plus group. The antibacterial activity against Enterococcus faecalis showed no significant difference between MTA and iRoot BP Plus. Therefore, both materials may be suitable for retro-filling applications.

CTP-CM enhances osteogenic differentiation of hPDLSCs via NF-κB pathway

OBJECTIVE

The conditioned medium of calcined tooth powder (CTP-CM) is a type of biomimetic mineralized material and well contributing to bone healing and bone formation in vivo. However, little is known about the effect of CTP-CM on human periodontal ligament stem cells (hPDLSCs) as well as the underlying mechanisms.

METHODS

ALP activity assay was conducted to select the concentration with the highest ALP level, which was used for the following experiments. Cell proliferation was measured by cell counting kit-8 assay and flow cytometry analysis. Expression levels of osteogenic markers in CTP-CM-induced hPDLSCs were evaluated with real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), immunofluorescence staining, and Western blot. Mineralization of CTP-CM-induced hPDLSCs was evaluated by alizarin red staining. Furthermore, the involvement of NF-κB pathway was examined by immunofluorescence staining and Western blot.

RESULTS

20 μg/ml was selected for the further experiments. Functional studies demonstrated that CTP-CM exerted almost no influence on the proliferation of hPDLSCs and CTP-CM increased the osteogenic differentiation of hPDLSCs. Mechanistically, CTP-CM leads to activation of NF-κB signaling pathway. When treated with BMS345541, the osteogenic differentiation of CTP-CM-treated hPDLSCs was significantly attenuated.

CONCLUSION

CTP-CM can promote the osteogenic differentiation of hPDLSCs via activating NF-κB pathway.

Dental stem cell signaling pathway activation in response to hydraulic calcium silicate-based endodontic cements: A systematic review of in vitro studies

OBJECTIVE

To present a qualitative synthesis of in vitro studies which analyzed human dental stem cell (DSC) molecular signaling pathway activation in response to hydraulic calcium silicate-based cements (HCSCs).

METHODS

A systematic electronic search was performed in Medline, Scopus, Embase, Web of Science and SciELO databases on January 20 and last updated on March 20, 2020. In vitro studies assessing the implication of signaling pathways in activity related marker (gene/protein) expression and mineralization induced by HCSCs in contact with human DSCs were included.

RESULTS

The search identified 277 preliminary results. After discarding duplicates, and screening of titles, abstracts, and full texts, 13 articles were considered eligible. All of the materials assessed by the included studies showed positive results in cytocompatibility and/or bioactivity assays. ProRoot MTA and Biodentine were the modal HCSCs studied, hDPSCs were the modal cell variant used, and the most studied signaling pathway was MAPK. In vitro assays measuring the expression of activity-related markers and mineralized nodule formation evidenced the involvement of MAPK (and its subfamilies ERK, JNK and P38), NF-κB, Wnt/β-catenin, BMP/Smad and CAMKII pathways in the biological response of DSCs to HCSCs.

SIGNIFICANCE

HCSCs considered in the present review elicited a favorable biological response from a variety of DSCs in vitro, thus supporting their use in biologically-based endodontic procedures. MAPK, NF-κβ, Wnt/β-catenin, BMP/Smad and CAMKII signaling pathways have been proposed as potential mediators in the biological interaction between DSCs and HCSCs. Understanding the signaling processes involved in tissue repair could lead to the development of new biomaterial compositions targeted at enhancing these mechanisms through biologically-based procedures.

iRoot SP Promotes Osteo/Odontogenesis of Bone Marrow Mesenchymal Stem Cells via Activation of NF-κB and MAPK Signaling Pathways

The regeneration of bone and tooth tissues, and related cellular therapies, has attracted widespread attention. Bone marrow mesenchymal stem cells (BMSCs) are potential candidates for such regeneration. iRoot SP is a premixed bioceramic root canal sealer widely used in clinical settings. However, the effect of iRoot SP on the biological features of BMSCs has not been elucidated. In the present study, we found that 0.2 mg/ml iRoot SP conditioned medium promoted osteo/odontogenic differentiation and enhanced mineralization of BMSCs without affecting the proliferative ability. Mechanistically, the NF-κB and MAPK signaling pathways were activated in SP-treated BMSCs, and differentiation was inhibited when cultured with the specific inhibitor. Taken together, these findings demonstrate that iRoot SP promotes osteo/odontogenic differentiation of BMSCs via the NF-κB and MAPK signaling pathways, which could provide a new theoretical basis for clinical applications of iRoot SP and a new therapeutic target for the regeneration of bone and tooth tissue in the future.

MTA Enhances the Potential of Adipose-Derived Mesenchymal Stem Cells for Dentin-Pulp Complex Regeneration

The aim of the current study was to investigate the effects of mineral trioxide aggregate (MTA) on the proliferation and differentiation of human adipose-derived mesenchymal stem cells (Ad-MSCs) as a surrogate cell source in futuristic stem-cell-based endodontic therapies. Human Ad-MSCs and mesenchymal stem cells derived from bone marrow (BM-MSCs) were isolated from liposuction waste adipose tissue and femur, respectively, and the effects of MTA-conditioned media on their viability, mineralization potential, and osteo/odontogenic differentiation capacity were subsequently evaluated. Alkaline phosphatase (ALP) activity, quantitative alizarin red S staining, and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analyses were performed to investigate and compare the osteo/odontogenic induction potential of MTA on the Ad/BM-MSCs. The results of cytotoxicity assay revealed that at different concentrations, MTA-conditioned medium was not only biocompatible toward both cell types, but also capable of promoting cell proliferation. ALP activity assay showed that 0.2 mg/mL was the optimal concentration of MTA-conditioned medium for osteo/odontogenic induction in Ad/BM-MSCs. The expression of osteo/odontogenic gene markers was increased in Ad/BM-MSCs treated with 0.2 mg/mL MTA-conditioned media. Our results indicated that MTA can efficiently enhance the osteo/odontogenic potential of Ad-MSCs, and thus they can be considered as a better cell source for dentin-pulp complex regeneration. However, further investigations are required to test these potentials in animal models.

The effects of mineral trioxide aggregate on osteo/odontogenic potential of mesenchymal stem cells: a comprehensive and systematic literature review

The significance of dental materials in dentin-pulp complex tissue engineering is undeniable. The mechanical properties and bioactivity of mineral trioxide aggregate (MTA) make it a promising biomaterial for future stem cell-based endodontic therapies. There are numerous in vitro studies suggesting the low cytotoxicity of MTA towards various types of cells. Moreover, it has been shown that MTA can enhance mesenchymal stem cells' (MSCs) osteo/odontogenic ability. According to the preferred reporting items for systematic reviews and meta-analyses (PRISMA), a literature review was conducted in the Medline, PubMed, and Scopus databases. Among the identified records, the cytotoxicity and osteo/odontoblastic potential of MTA or its extract on stem cells were investigated. Previous studies have discovered the differentiation-inducing potential of MTA on MSCs, providing a background for dentin-pulp complex cell therapies using the MTA, however, animal trials are needed before moving into clinical trials. In conclusion, MTA can be a promising candidate dental biomaterial for futuristic stem cell-based endodontic therapies.

Microstructural composition, ion release, and bioactive potential of new premixed calcium silicate-based endodontic sealers indicated for warm vertical compaction technique

OBJECTIVE

The aim of this study was to evaluate the microstructural composition, ion release, cytocompatibility, and mineralization potential of Bio-C Sealer ION+ (BCI) and EndoSequence BC Sealer HiFlow (BCHiF), compared with AH Plus (AHP), in contact with human periodontal ligament cells (hPDLCs).

MATERIALS AND METHODS

The sealers' ionic composition and release were assessed using energy-dispersive spectroscopy (EDS) and inductively coupled plasma mass spectrometry (ICP-MS), respectively. For the biological assays, hPDLCs were isolated from third molars, and sealer extracts were prepared (undiluted, 1:2, and 1:4 ratios). An MTT assay, wound-healing assay, and cell morphology and adhesion analysis were performed. Activity-related gene expression was determined using RT-qPCR, and mineralization potential was assessed using Alizarin Red staining (ARS). Statistical analyses were performed using one-way ANOVA and Tukey's post hoc test (α < 0.05).

RESULTS

The three sealers exhibited variable levels of silicon, calcium, zirconium, and tungsten release and in their composition. Both BCI and BCHiF groups showed positive results in cytocompatibility assays, unlike AHP. The BCHiF group showed an upregulation of CAP (p < 0.01), CEMP1, ALP, and RUNX2 (p < 0.001) compared with the negative control, while the BCI group showed an upregulation of CEMP1 (p < 0.01), CAP, and RUNX2 (p < 0.001). Both groups also exhibited a greater mineralization potential than the negative and positive controls (p < 0.001).

CONCLUSIONS

The calcium silicate-based sealers considered in the present in vitro study exhibited a high calcium ion release, adequate cytocompatibility, upregulated osteo/cementogenic gene expression, and increased mineralized nodule formation in contact with hPDLCs.

CLINICAL RELEVANCE

From a biological perspective, BCI and BCHiF could be clinically suitable for root canal filling.

Intermittent Administration of Parathyroid Hormone Enhances Odonto/Osteogenic Differentiation of Stem Cells from the Apical Papilla via JNK and P38 MAPK Pathways

Objective

Parathyroid hormone (PTH) is considered to be essential during the tooth development. Stem cells from the apical papilla (SCAPs) are responsible for dentine formation. However, the interaction between PTH and SCAPs remains unclear. This study was aimed at investigating the effects of PTH on odonto/osteogenic differentiation capacity of SCAPs and elucidating the underlying molecular mechanisms. Materials and Methods. Here, SCAPs were isolated and identified in vitro. Effects of PTH on the proliferation of SCAPs were determined by Cell Counting Kit-8 (CCK-8), flow cytometry (FCM), and EdU. Alkaline phosphatase (ALP) activity, alizarin red staining, Western blot, and RT-PCR were carried out to detect the odonto/osteogenic differentiation of PTH-treated SCAPs as well as the participation of the MAPK signaling pathway.

Results

An ALP activity assay determined that 10^-8 mol/L PTH was the optimal concentration for the induction of SCAPs with no significant influence on the proliferation of SCAPs as indicated by CCK-8, FCM, and EdU. The expression of odonto/osteogenic markers was significantly upregulated in mRNA levels and protein levels. Moreover, intermittent treatment of PTH also increased phosphorylation of JNK and P38, and the differentiation was suppressed following the inhibition of JNK and P38 MAPK pathways.

Conclusion

PTH can regulate the odonto/osteogenic differentiation of SCAPs via JNK and P38 MAPK pathways.

In Vitro Effect of Putty Calcium Silicate Materials on Human Periodontal Ligament Stem Cells

New bioactive materials have been developed for retrograde root filling. These materials come into contact with vital tissues and facilitate biomineralization and apical repair. The objective of this study was to evaluate the cytocompatibility and bioactivity of two bioactive cements, Bio-C Repair (Angelus, Londrina, Pr, Brazil) and TotalFill BC RRM putty (FGK, Dentaire SA, La-Chaux-de-fonds, Switzerland). The biological properties in human periodontal ligament stem cells (hPDLSCs) that were exposed to Bio-C Repair and TotalFill BC RRM putty were studied. Cell viability, migration, and cell adhesion were analyzed. Moreover, qPCR and mineralization assay were performed to evaluate the bioactivity potential of these cements. The results were statistically analyzed using ANOVA and the Tukey test (p < 0.05). It was observed that cell viability and cell migration in Bio-C Repair and TotalFill BC RRM putty were similar to the control without statistically significant differences, except at 72 h when TotalFill BC RRM putty was slightly lower (p < 0.05). Excellent cell adhesion and morphology were observed with both Bio-C Repair and TotalFill BC RRM putty. Both cements promoted the osteo- and cementogenic differentiation of hPDLSCs. These results suggest that Bio-C Repair and TotalFill BC RRM putty are biologically appropriate materials to be used as retrograde obturation material.

Potassium dihydrogen phosphate promotes the proliferation and differentiation of human periodontal ligament stem cells via nuclear factor kappa B pathway

INTRODUCTION

Periodontal ligament stem cells (PDLSCs) are vital for the regeneration of periodontal tissues. Potassium dihydrogen phosphate (KH₂PO₄) has recently been applied as a component of the mineralization inducing medium (MM), which can be used to induce osteogenic differentiation of dental stem cells. However, whether KH₂PO₄ has effects on PDLSCs has not been studied.

MATERIALS AND METHODS

PDLSCs were isolated by magnetic activated cell sorting and cultured. Alkaline phosphatase (ALP) activity and ALP protein expression of PDLSCs treated with different concentrations of KH₂PO₄ were examined to make sure the optimal concentration of KH₂PO₄ for the following experiments. The effects of KH₂PO₄ on the proliferation and differentiation of PDLSCs were investigated by flow cytometry, cell counting kit-8 assay, alizarin red staining, real-time RT-PCR, and Western blot. The involvement of nuclear factor kappa B (NF-κB) pathway in KH₂PO₄-treated PDLSCs was analyzed by Western blot and alizarin red staining.

RESULTS

ALP activity assay and ALP protein expression examination revealed that 1.8 mmol/L KH₂PO₄ was the optimal concentration for the induction of hPDLSCs by KH₂PO₄. The proliferation and mineralization capacity of PDLSCs treated with KH₂PO₄ were enhanced as compared with the control group. PDLSCs treated with KH₂PO₄ showed an improved proliferation capacity in logarithmic growth phase at day 7. As PDLSCs were treated with KH₂PO₄, the expression of odonto/osteogenic markers (OCN/OCN, DSP/DSPP, OSX/OSX, RUNX2/RUNX2, and ALP/ALP) in cells were up-regulated at day 3 or 7. Moreover, the expression of IκBα in cytoplasm was down-regulated, along with an increased expression of p-P65 in cytoplasm and an up-regulated expression of P65 in nucleus. When treated with BMS345541 (the specific NF-κB inhibitor), the odonto/osteogenic differentiation of KH₂PO₄-treated PDLSCs was significantly attenuated.

CONCLUSION

KH₂PO₄ can improve the proliferation and odonto/osteogenic differentiation capacity of PDLSCs via NF-κB pathway, and thus represents a potential target involved in the regeneration of periodontium for clinical treatments.

Comparative Cytocompatibility and Mineralization Potential of Bio-C Sealer and TotalFill BC Sealer

The aim of this study was to investigate the cytocompatibility and mineralization potential of two premixed hydraulic endodontic sealers compared with an epoxy resin-based root canal sealer. The cellular responses and mineralization capacity were studied in human periodontal ligament stem cells (hPDLSCs) that were exposed to premixed hydraulic sealers, Bio-C Sealer (Angelus, Londrína, PR, Brazil), TotalFill BC Sealer (FKG Dentaire SA, La-Chaux-de-fonds, Switzerland) and an epoxy resin-based material, AH Plus (Dentsply De Trey, Konstanz, Germany). Non-exposed cultures served as the control. The endodontic sealers were assessed using scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis (EDX). Statistical analyses were done using Analisis of Variance (ANOVA), with Bonferroni adjusted pairwise comparison (p = 0.05). AH Plus reduced cell viability and cell migration, whereas increased cell viability and cell migration were observed in the Bio-C Sealer and the TotalFill BC Sealer (p < 0.05). The lowest cell attachment and spreading were observed for all concentrations of AH Plus, whereas the highest were observed for TotalFill BC Sealer. At the end of 21 days, only the Bio-C Sealer and the TotalFill BC Sealer supported matrix mineralization (p < 0.05). Additionally, SEM-EDX revealed high content of calcium, oxygen, and silicon in the Bio-C Sealer and the TotalFill BC Sealer. Based on the results from this study, Bio-C Sealer and TotalFill BC Sealer demonstrated better cytocompatibility in terms of cell viability, migration, cell morphology, cell attachment, and mineralization capacity than AH Plus.

iRoot BP Plus promotes osteo/odontogenic differentiation of bone marrow mesenchymal stem cells via MAPK pathways and autophagy

BACKGROUND

iRoot BP Plus is a novel bioceramic endodontic material. Recently, it has been considered as an alternative to MTA which is the most popular scaffold cover during regenerative endodontic therapy. This study aimed to evaluate the effects of iRoot BP Plus on the osteo/odontogenic capacity of bone marrow mesenchymal stem cells (BMMSCs), including the underlying mechanisms.

METHODS

BMMSCs were collected by a whole marrow method and treated with iRoot BP Plus-conditioned medium (BP-CM). The proliferation ability was evaluated by cell counting kit 8 and flow cytometry. Complete medium was used as a blank control, and 2 mg/ml MTA-conditioned medium was served as a positive control. Alkaline phosphatase (ALP) activity assay, ALP staining, western blot, real-time RT-PCR, Alizarin Red S staining, and immunofluorescence staining were performed to explore the osteo/odontogenic potential and the involvement of MAPK pathways. Besides, autophagy was investigated by western blot, immunofluorescence staining, and transmission electron microscopy.

RESULTS

Parathyroid hormone enhances the osteo/odontogenic differentiation of dental pulp stem cells via ERK and P38 MAPK pathways

OBJECTIVE

Parathyroid hormone (PTH) is a main systemic mediator of calcium and phosphate homeostasis in the bone. Dental pulp stem cells (DPSCs) have been extensively studied in the regeneration of bone and tooth tissues. This paper aims to uncover the influences of PTH on the proliferative ability and osteo/odontogenic differentiation of DPSCs, as well as the underlying mechanisms.

MATERIALS AND METHODS

The optimal concentration of PTH on DPSCs was determined by alkaline phosphatase (ALP) activity assay, ALP staining and western blot analysis. Proliferative ability and cell cycle distribution of DPSCs were analyzed by Cell counting kit-8, 5-ethynyl-20-deoxyuridine assay, and flow cytometry. Osteo/odontogenic capacity of DPSCs was evaluated and finally, the involvement of mitogen-activated protein kinase (MAPK) pathway was assessed.

RESULTS

Purified DPSCs were obtained by enzymatic digestion, which presented a typical fibroblast-like morphology. 10^-9  mol/L PTH was concerned as the optimal concentration for DPSCs induction. 10^-9  mol/L PTH treatment did not change the proliferative rate of DPSCs (p > .05). Relative expressions of DSPP/DSPP, RUNX2/RUNX2, OSX/OSX, and ALP/ALP were upregulated in PTH-treated DPSCs relative to control group. Particularly, their mRNA/protein levels at Day 7 were markedly higher relative to those at Day 3 (p < .05 or p < .01). Mineralized nodules were formed after PTH induction, and calcium content increased by cetylpyridinium chloride quantitative analysis. Mechanistically, the protein levels of p-ERK and p-P38 significantly increased after PTH treatment, and the inhibitors targeting MAPK were identified that weakened the effects of PTH on the committed differentiation of DPSCs.

CONCLUSIONS

PTH enhances the osteo/odontogenic differentiation capacity of DPSCs via ERK and P38 signaling pathways.

Differential circular RNA expression profiling during osteogenic differentiation of stem cells from apical papilla

Aim: This study aimed to investigate the distinct expression pattern of circular RNAs (circRNAs) in stem cells from apical papilla (SCAPs) during osteogenesis. Materials & methods: Isolated SCAPs were cultured in growth medium or osteogenic medium, respectively. Total RNA was extracted and submitted to RNA-sequencing. Expression profiles of circRNAs and constructed circRNA–miRNA–mRNA networks were determined. Results: A total of 333 unregulated circRNAs and 317 downregulated circRNAs in osteogenic differentiation were detected. Bioinformatics analysis identified that several biological pathways may be associated with osteogenic differentiation of SCAPs. Moreover, ten circRNAs, 21 miRNAs and 19 mRNAs were selected to construct competing endogenous RNA networks. Conclusion: This study revealed that expression profiles of circRNAs were significantly altered and specific circRNAs might function as competing endogenous RNAs in SCAPs during osteogenic differentiation.

LncRNA H19 promotes the committed differentiation of stem cells from apical papilla via miR-141/SPAG9 pathway

Long noncoding RNAs (lncRNAs) exert significant roles at transcriptional and post-transcriptional levels. Stem cells from apical papilla (SCAPs) differentiate into dentin/bone-like tissues under certain conditions. So far, whether lncRNA-H19 can affect the proliferative behaviors and osteo/odontogenesis of SCAPs, as well as its specific mechanism remain to be elucidated. Here, SCAPs were isolated and transfected with the lentiviruses or packaging vectors. Our results showed that lncRNA-H19 had no significant effect on the proliferative behaviors of SCAPs, as presented by CCK-8 assay, EdU assay and flow cytometry (FCM). Furthermore, alkaline phosphatase (ALP) activity, alizarin red staining, Western blot assay (WB), quantitative real-time polymerase chain reaction (qRT-PCR) and in vivo bone formation assay were conducted to verify the biological influences of H19 on SCAPs. Overexpression of H19 led to the enhanced osteo/odontogenesis of SCAPs, whereas knockdown of H19 inhibited these effects. Mechanistically, H19 competitively bound to miR-141 and prevented SPAG9 from miRNA-mediated degradation, thus significantly elevating phosphorylated levels of p38 and JNK and facilitating the committed differentiation of SCAPs. Taken together, the osteo/odontogenesis of SCAPs was upregulated by overexpression of H19 via miR-141/SPAG9 pathway.

Biological effects of acid-eroded MTA Repair HP and ProRoot MTA on human periodontal ligament stem cells

OBJECTIVE

The aim of this study was to analyze the biological effects of MTA Repair HP and ProRoot MTA on human periodontal ligament stem cells (hPDLSCs) after exposure to acidic and neutral environments.

MATERIALS AND METHODS

Discs of each material (n = 30) were exposed to phosphate buffered saline (pH = 7.4) or butyric acid (pH = 5.2) for 7 days, and biological testing was carried out in vitro on hPDLSCs. Cell viability and apoptosis assays were performed using eluates of each root-end filling material. To evaluate cell attachment to the different materials, hPDLSCs were directly seeded onto the material surfaces and analyzed by scanning electron microscopy. The chemical composition of the root-end filling materials was determined by energy-dispersive x-ray and eluates were analyzed by inductively coupled plasma-mass spectrometry. Statistical differences were assessed by ANOVA and Tukey test (p < 0.05).

RESULTS

Under an acidic environment, both materials displayed similar ion release abilities, with the increased release of Si and Ca ions. Substantial changes in microstructure were observed for both materials after exposure to acidic pH. In addition, material exposure to an acidic environment showed a similar degree of cell adherence, and, surprisingly, MTA Repair HP exhibited higher cell viability rates at pH 5.2 than ProRoot MTA.

CONCLUSIONS

Exposure to an acidic environment promoted Si and Ca ion release from ProRoot MTA and MTA Repair HP. Moreover, we observed optimal biological properties of ProRoot MTA and MTA Repair HP in terms of cell viability, cell death, and cell attachment in both environments.

CLINICAL RELEVANCE

These results may suggest that MTA Repair HP and ProRoot exhibited optimal biological properties in terms of cell viability, cell death and cell attachment in acidic environment, being considered as materials for root-end filling and perforations.

Role of the P2X7 receptor in inflammation-mediated changes in the osteogenesis of periodontal ligament stem cells

Accumulating evidence indicates that the pluripotency of periodontal ligament stem cells (PDLSCs) is compromised under inflammatory conditions; however, the underlying mechanisms remain largely unexplored. In this study, we hypothesize that the P2X7 receptor (P2X7R) is a key molecule linked to inflammation-associated impairment of PDLSCs. We first investigated P2X7R expression in PDLSCs under normal and inflammatory conditions and then determined the effect of a P2X7R agonist (BzATP) or antagonist (BBG) on PDLSC osteogenesis under various conditions. Gene-modified PDLSCs were used to further examine the role of P2X7R and the signaling pathway underlying P2X7R-enhanced osteogenesis. We found that inflammatory conditions decreased P2X7R expression in PDLSCs and reduced osteogenesis in these cells. In addition, activation of P2X7R by BzATP or overexpression of P2X7R via gene transduction reversed the inflammation-mediated decrease in PDLSC osteogenic differentiation. When selected osteogenesis-related signaling molecules were screened, the PI3K-AKT-mTOR pathway was identified as potentially involved in P2X7R-enhanced PDLSC osteogenesis. Our data reveal a crucial role for P2X7R in PDLSC osteogenesis under inflammatory conditions, suggesting a new therapeutic target to reverse or rescue inflammation-mediated changes in PDLSCs for future mainstream therapeutic uses.

MicroRNA hsa-let-7b suppresses the odonto/osteogenic differentiation capacity of stem cells from apical papilla by targeting MMP1

MicroRNA let-7 family acts as the key regulator of the differentiation of mesenchymal stem cells (MSCs). However, the influence of let-7b on biological characteristics of stem cells from apical papilla (SCAPs) is still controversial. In this study, the expression of hsa-let-7b was obviously downregulated during the osteogenic differentiation of SCAPs. SCAPs were then infected with hsa-let-7b or hsa-let-7b inhibitor lentiviruses. The proliferation ability was determined by CCK-8 and flow cytometry. The odonto/osteogenic differentiation capacity was analyzed by alkaline phosphatase (ALP) activity, alizarin red staining, Western blot assay, and real-time RT-PCR. Bioinformatics analysis was used to screen out the target of hsa-let-7b and the target relationship was confirmed by dual luciferase reporter assay. Hsa-let-7b was of no influence on the proliferation of SCAPs. Interferential expression of hsa-let-7b increased the ALP activity as well as the formation of calcified nodules of SCAPs. Moreover, the mRNA levels of osteoblastic markers (ALP, RUNX2, OSX, OPN, and OCN) were upregulated while the protein levels of DSPP, ALP, RUNX2, OSX, OPN, and OCN also increased considerably. Conversely, overexpression of hsa-let-7b inhibited the odonto/osteogenic differentiation capacity of SCAPs. Bioinformatics analysis revealed a putative binding site of hsa-let-7b in the matrix metalloproteinase 1 (MMP1) 3'-untranslated region (3'-UTR). Dual luciferase reporter assay confirmed that hsa-let-7b targets MMP1. The odonto/osteogenic differentiation ability of SCAPs ascended after repression of hsa-let-7b, which was then reversed after co-transfection with siMMP1. Together, hsa-let-7b can suppress the odonto/osteogenic differentiation capacity of SCAPs by targeting MMP1.