Increasing Odontoblast-like Differentiation from Dental Pulp Stem Cells through Increase of β-Catenin/p-GSK-3β Expression by Low-Frequency Electromagnetic Field

The Frequency of a Magnetic Field Determines the Behavior of Tumor and Non-Tumor Nerve Cell Models

The involvement of magnetic fields in basic cellular processes has been studied for years. Most studies focus their results on a single frequency and intensity. Intensity has long been the central parameter in hypotheses of interaction between cells and magnetic fields; however, frequency has always played a secondary role. The main objective of this study was to obtain a specific frequency that allows a reduction in the viability and proliferation of glioblastoma (CT2A) and neuroblastoma (N2A) cell models. These were compared with an astrocyte cell model (C8D1A) (nontumor) to determine whether there is a specific frequency of response for each of the cell lines used. The CT2A, C8D1A, and N2A cell lines were exposed to a magnetic field of 100 µT and a variable frequency range between 20 and 100 Hz for 24, 48 and 72 h. The results fit a biological window model in which the viability and proliferation of N2A and CT2A cells decrease statistically significantly in a 50 Hz center of value window. In addition, the non-tumor cell model showed different behavior from tumor cell models depending on the applied frequency. These results are promising in the use of magnetic fields for therapeutic purposes.

Design and characterisation of a cell exposure system with high magnetic field homogeneity: RILZ coils

In vitro studies requiring controlled exposure to low-frequency electromagnetic fields employ exposure systems with different geometries and configurations, the Helmholtz configuration being one of the most widely used. This configuration has limitations in the homogeneity of the spatial distribution of the magnetic field intensity values. We present the design, manufacturing, and characterisation of a new coil system, called RILZ configuration, which improves the distribution of magnetic field intensity values in the three dimensions of space for three different heights in comparison with the traditional circular coils in Helmholtz configuration. In addition, a comparative study of the cellular response in CT2A cultures exposed to a magnetic field of 50 Hz and 100 µT for 48 hrs is performed with both exposure systems. The results of the study show reduced values of deviation from the central value of magnetic field intensity using the RILZ coil system. These differences are statistically significant compared to the Helmholtz configuration for the three Cartesian directions: x (p < 0.01), y (p < 0.01), z (p < 0.01). In addition, the intensity values for three different heights are statistically significantly correlated using the RILZ coil system (p < 0.01). The differences in cell behaviour are also statistically significant between the two systems (p < 0.01) and may be directly related to the differences found in the distribution of intensity values between the two systems. This study highlights the importance of the homogeneity of the magnetic field intensity generated by the exposure systems used and offers an effective solution to control the magnetic field exposure parameters in vitro assays.

Current Trends, Advances, and Challenges of Tissue Engineering-Based Approaches of Tooth Regeneration: A Review of the Literature

INTRODUCTION

Tooth loss is a significant health issue. Currently, this situation is often treated with the use of synthetic materials such as implants and prostheses. However, these treatment modalities do not fully meet patients' biological and mechanical needs and have limited longevity. Regenerative medicine focuses on the restoration of patients' natural tissues via tissue engineering techniques instead of rehabilitating with artificial appliances. Therefore, a tissue-engineered tooth regeneration strategy seems like a promising option to treat tooth loss.

OBJECTIVE

This review aims to demonstrate recent advances in tooth regeneration strategies and discoveries about underlying mechanisms and pathways of tooth formation.

RESULTS AND DISCUSSION

Whole tooth regeneration, tooth root formation, and dentin-pulp organoid generation have been achieved by using different seed cells and various materials for scaffold production. Bioactive agents are critical elements for the induction of cells into odontoblast or ameloblast lineage. Some substantial pathways enrolled in tooth development have been figured out, helping researchers design their experiments more effectively and aligned with the natural process of tooth formation.

CONCLUSION

According to current knowledge, tooth regeneration is possible in case of proper selection of stem cells, appropriate design and manufacturing of a biocompatible scaffold, and meticulous application of bioactive agents for odontogenic induction. Understanding innate odontogenesis pathways play a crucial role in accurately planning regenerative therapeutic interventions in order to reproduce teeth.

Public RNA-seq data-based identification and functional analyses reveal that MXRA5 retains proliferative and migratory abilities of dental pulp stem cells

Dental pulp stem cells (DPSC) usually remain quiescent in the dental pulp tissue; however, once the dental pulp tissue is injured, DPSCs potently proliferate and migrate into the injury microenvironment and contribute to immuno-modulation and tissue repair. However, the key molecules that physiologically support the potent proliferation and migration of DPSCs have not been revealed. In this study, we searched publicly available transcriptome raw data sets, which contain comparable (i.e., equivalently cultured) DPSC and mesenchymal stem cell data. Three data sets were extracted from the Gene Expression Omnibus database and then processed and analyzed. MXRA5 was identified as the predominant DPSC-enriched gene associated with the extracellular matrix. MXRA5 is detected in human dental pulp tissues. Loss of MXRA5 drastically decreases the proliferation and migration of DSPCs, concomitantly with reduced expression of the genes associated with the cell cycle and microtubules. In addition to the known full-length isoform of MXRA5, a novel splice variant of MXRA5 was cloned in DPSCs. Recombinant MXRA5 coded by the novel splice variant potently induced the haptotaxis migration of DPSCs, which was inhibited by microtubule inhibitors. Collectively, MXRA5 is a key extracellular matrix protein in dental pulp tissue for maintaining the proliferation and migration of DPSCs.

Topographic Cues of a PLGA Scaffold Promote Odontogenic Differentiation of Dental Pulp Stem Cells through the YAP/β-Catenin Signaling Axis

PURPOSE

The underlying mechanism of how topographic cues of artificial scaffolds regulate cell function remains poorly understood. Yes-associated protein (YAP) and β-catenin signaling have both been reported to play important roles in mechano-transduction and dental pulp stem cells (DPSCs) differentiation. We investigated the effects of YAP and β-catenin in spontaneous odontogenic differentiation of DPSCs induced by topographic cues of a poly(lactic-co-glycolic acid) (PLGA) membrane.

METHODS

The topographic cues and function of a fabricated PLGA scaffold were explored via scanning electron microscopy (SEM), alizarin red staining (ARS), reverse transcription-polymerase chain reaction (RT-PCR), and pulp capping. Immunohistochemistry (IF), RT-PCR, and western blotting (WB) were used to observe the activation of YAP and β-catenin when DPSCs were cultured on the scaffolds. Further, YAP was inhibited or overexpressed on either side of the PLGA membrane, and YAP, β-catenin, and odontogenic marker expression were analyzed using IF, ARS, and WB.

RESULTS

The closed side of the PLGA scaffold promoted spontaneous odontogenic differentiation and nuclear translocation of YAP and β-catenin in vitro and in vivo compared to the open side. The YAP antagonist verteporfin inhibited β-catenin expression, nuclear translocation, and odontogenic differentiation on the closed side, but the effects were rescued by LiCl. YAP overexpressing DPSCs on the open side activated β-catenin signaling and promoted odontogenic differentiation.

CONCLUSION

The topographic cue of our PLGA scaffold promotes odontogenic differentiation of DPSCs and pulp tissue through the YAP/β-catenin signaling axis.

Natural Bioactive Epigallocatechin-Gallate Promote Bond Strength and Differentiation of Odontoblast-like Cells

The (-)-Epigallocatechin-gallate (EGCG) metabolite is a natural polyphenol derived from green tea and is associated with antioxidant, biocompatible, and anti-inflammatory effects.

OBJECTIVE

To evaluate the effects of EGCG to promote the odontoblast-like cells differentiated from human dental pulp stem cells (hDPSCs); the antimicrobial effects on Escherichia coli, Streptococcus mutans, and Staphylococcus aureus; and improve the adhesion on enamel and dentin by shear bond strength (SBS) and the adhesive remnant index (ARI).

MATERIAL AND METHODS

hDSPCs were isolated from pulp tissue and immunologically characterized. EEGC dose-response viability was calculated by MTT assay. Odontoblast-like cells were differentiated from hDPSCs and tested for mineral deposition activity by alizarin red, Von Kossa, and collagen/vimentin staining. Antimicrobial assays were performed in the microdilution test. Demineralization of enamel and dentin in teeth was performed, and the adhesion was conducted by incorporating EGCG in an adhesive system and testing with SBS-ARI. The data were analyzed with normalized Shapiro-Wilks test and ANOVA post hoc Tukey test.

RESULTS

The hDPSCs were positive to CD105, CD90, and vimentin and negative to CD34. EGCG (3.12 µg/mL) accelerated the differentiation of odontoblast-like cells. Streptococcus mutans exhibited the highest susceptibility < Staphylococcus aureus < Escherichia coli. EGCG increased (p < 0.05) the dentin adhesion, and cohesive failure was the most frequent.

CONCLUSION

(-)-Epigallocatechin-gallate is nontoxic, promotes differentiation into odontoblast-like cells, possesses an antibacterial effect, and increases dentin adhesion.

METTL3-Mediated lncSNHG7 m6A Modification in the Osteogenic/Odontogenic Differentiation of Human Dental Stem Cells

Background: Human dental pulp stem cells (hDPSCs) play an important role in endodontic regeneration. N6-methyladenosine (m⁶A) is the most common RNA modification, and noncoding RNAs have also been demonstrated to have regulatory roles in the expression of m⁶A regulatory proteins. However, the study on m⁶A modification in hDPSCs has not yet been conducted. Methods: Single base site PCR (MazF) was used to detect the m⁶A modification site of lncSNHG7 before and after mineralization of hDPSCs to screen the target m⁶A modification protein, and bioinformatics analysis was used to analyze the related pathways rich in lncSNHG7. After knockdown and overexpression of lncSNHG7 and METTL3, the osteogenic/odontogenic ability was detected. After METTL3 knockdown, the m⁶A modification level and its expression of lncSNHG7 were detected by MazF, and their binding was confirmed. Finally, the effects of lncSNHG7 and METTL3 on the Wnt/β-catenin pathway were detected. Results: MazF experiments revealed that lncSNHG7 had a m⁶A modification before and after mineralization of hDPSCs, and the occurrence site was 2081. METTL3 was most significantly upregulated after mineralization of hDPSCs. Knockdown/ overexpression of lncSNHG7 and METTL3 inhibited/promoted the osteogenic/odontogenic differentiation of hDPSCs. The m⁶A modification and expression of lncSNHG7 were both regulated by METTL3. Subsequently, lncSNHG7 and METTL3 were found to regulate the Wnt/β-catenin signaling pathway. Conclusion: These results revealed that METTL3 can activate the Wnt/β-catenin signaling pathway by regulating the m⁶A modification and expression of lncSNHG7 in hDPSCs to enhance the osteogenic/odontogenic differentiation of hDPSCs. Our study provides new insight into stem cell-based tissue engineering.