Differentiation of human dental stem cells reveals a role for microRNA-218

Notch signaling regulates mineralization via microRNA modulation in dental pulp stem cells

OBJECTIVES

This study investigated the miRNA expression profile in Notch-activated human dental stem pulp stem cells (DPSCs) and validated the functions of miRNAs in modulating the odonto/osteogenic properties of DPSCs.

METHODS

DPSCs were treated with indirect immobilized Jagged1. The miRNA expression profile was examined using NanoString analysis. Bioinformatic analysis was performed, and miRNA expression was validated. Odonto/osteogenic differentiation was examined using alkaline phosphatase staining, Alizarin Red S staining, as well as odonto/osteogenic-related gene and protein expression.

RESULTS

Fourteen miRNAs were differentially expressed in Jagged1-treated DPSCs. Pathway analysis revealed that altered miRNAs were associated with TGF-β, Hippo, ErbB signalling pathways, FoxO and Ras signalling. Target prediction analysis demonstrated that 7604 genes were predicted to be targets for these altered miRNAs. Enrichment analysis revealed relationships to various DNA bindings. Among differentially expressed miRNA, miR-296-3p and miR-450b-5p were upregulated under Jagged1-treated conditions. Overexpression of miR-296-3p and miR-450b-5p enhanced mineralization and upregulation of odonto/osteogenic-related genes, whereas inhibition of these miRNAs revealed opposing results. The miR-296-3p and miR-450b-5p inhibitors attenuated the effects of Jagged1-induced mineralization in DPSCs.

CONCLUSIONS

Jagged-1 promotes mineralization in DPSCs that are partially regulated by miRNA. The novel understanding of these miRNAs could lead to innovative controlled mechanisms that can be applied to modulate biology-targeted dental materials.

MiRNAs regulate cell communication in osteogenesis-angiogenesis coupling during bone regeneration

Bone regeneration is a complex process that requires not only the participation of multiple cell types, but also signal communication between cells. The two basic processes of osteogenesis and angiogenesis are closely related to bone regeneration and bone homeostasis. H-type vessels are a subtype of bone vessels characterized by high expression of CD31 and EMCN. These vessels play a key role in the regulation of bone regeneration and are important mediators of coupling between osteogenesis and angiogenesis. Molecular regulation between different cell types is important for coordination of osteogenesis and angiogenesis that promotes bone regeneration. MiRNAs are small non-coding RNAs that predominantly regulate gene expression at the post-transcriptional level and are closely related to cell communication. Specifically, miRNAs transduce external stimuli through various cell signaling pathways and cause a series of physiological and pathological effects. They are also deeply involved in the bone repair process. This review focuses on three signaling pathways related to osteogenesis-angiogenesis coupling, as well as the miRNAs involved in these pathways. Elucidation of the molecular mechanisms governing osteogenesis and angiogenesis is of great significance for bone regeneration.

Current concepts of microRNA-mediated regulatory mechanisms in human pulp tissue-derived stem cells: a snapshot in the regenerative dentistry

One of the most studied class of non-coding RNAs is microRNAs (miRNAs) which regulate more than 60% of human genes. A network of miRNA gene interactions participates in stem cell self-renewal, proliferation, migration, apoptosis, immunomodulation, and differentiation. Human pulp tissue-derived stem cells (PSCs) are an attractive source of dental mesenchymal stem cells (MSCs) which comprise human dental pulp stem cells (hDPSCs) obtained from the dental pulp of permanent teeth and stem cells isolated from exfoliated deciduous teeth (SHEDs) that would be a therapeutic opportunity in stomatognathic system reconstruction and repair of other damaged tissues. The regenerative capacity of hDPSCs and SHEDs is mediated by osteogenic, odontogenic, myogenic, neurogenic, angiogenic differentiation, and immunomodulatory function. Multi-lineage differentiation of PSCs can be induced or inhibited by the interaction of miRNAs with their target genes. Manipulating the expression of functional miRNAs in PSCs by mimicking miRNAs or inhibiting miRNAs emerged as a therapeutic tool in the clinical translation. However, the effectiveness and safety of miRNA-based therapeutics, besides higher stability, biocompatibility, less off-target effects, and immunologic reactions, have received particular attention. This review aimed to comprehensively overview the molecular mechanisms underlying miRNA-modified PSCs as a futuristic therapeutic option in regenerative dentistry.

MicroRNAs-mediated regulation of the differentiation of dental pulp-derived mesenchymal stem cells: a systematic review and bioinformatic analysis

BACKGROUND

Human dental pulp-derived mesenchymal stem cells (hDP-MSCs), which include human dental pulp stem cells (hDPSCs) and stem cells from human exfoliated deciduous teeth (SHEDs), are promising cell sources for regenerative therapies. Nevertheless, a lack of knowledge relating to the mechanisms regulating their differentiation has limited their clinical application. microRNAs (miRNAs) are important regulatory molecules in cellular processes including cell differentiation. This systematic review aims to provide a panel of miRNAs that regulate the differentiation of hDP-MSCs including hDPSCs and SHEDs. Additionally, bioinformatic analyses were conducted to discover target genes, signaling pathways and gene ontologies associated with the identified miRNAs.

METHODS

A literature search was performed in MEDLINE (via PubMed), Web of Science, Scopus, Embase and Cochrane Library. Experimental studies assessing the promotive/suppressive effect of miRNAs on the differentiation of hDP-MSCs and studies evaluating changes to the expression of miRNAs during the differentiation of hDP-MSCs were included. miRNAs involved in odontogenic/osteogenic differentiation were then included in a bioinformatic analysis. A miRNA-mRNA network was constructed, and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed. A protein-protein interaction (PPI) network was also constructed.

RESULTS

Of 766 initially identified records through database searching, 42 and 36 studies were included in qualitative synthesis and bioinformatic analyses, respectively. Thirteen miRNAs promoted and 17 suppressed odontogenic/osteogenic differentiation of hDP-MSCs. hsa-miR-140-5p, hsa-miR-218 and hsa-miR-143 were more frequently reported suppressing the odontogenic/osteogenic differentiation of hDP-MSCs. hsa-miR-221 and hsa-miR-124 promoted and hsa-miR-140-5p inhibited neuronal differentiation, hsa-miR-26a-5p promoted and hsa-miR-424 suppressed angiogenic differentiation, and hsa-miR-135 and hsa-miR-143 inhibited differentiation within myogenic lineages. A miRNA-mRNA network including 1890 nodes and 2171 edges was constructed. KEGG pathway analysis revealed MAPK, PI3K-Akt and FoxO as key signaling pathways involved in the odontogenic/osteogenic differentiation of hDP-MSCs.

CONCLUSIONS

The findings of this systematic review support the potential application of the specific miRNAs to regulate the directed differentiation of hDP-MSCs in the field of regenerative therapies.

Exploring craniofacial and dental development with microRNAs

microRNAs (miRs) are small RNA molecules that regulate many cellular and developmental processes. They control gene expression pathways during specific developmental time points and are required for tissue homeostasis and stem cell maintenance. miRs as therapeutic reagents in tissue regeneration and repair hold great promise and new technologies are currently being designed to facilitate their expression or inhibition. Due to the large amount of miR research in cells and cancer many cellular processes and gene networks have been delineated however, their in vivo response can be different in complex tissues and organs. Specifically, this report will discuss animal developmental models to understand the role of miRs as well as xenograft, disease, and injury models. We will discuss the role of miRs in clinical studies including their diagnostic function, as well as their potential ability to correct craniofacial diseases.

The Role of Epigenetic in Dental and Oral Regenerative Medicine by Different Types of Dental Stem Cells: A Comprehensive Overview

Postnatal teeth, wisdom teeth, and exfoliated deciduous teeth can be harvested for dental stem cell (DSC) researches. These mesenchymal stem cells (MSCs) can differentiate and also consider as promising candidates for dental and oral regeneration. Thus, the development of DSC therapies can be considered a suitable but challenging target for tissue regeneration. Epigenetics describes changes in gene expression rather than changes in DNA and broadly happens in bone homeostasis, embryogenesis, stem cell fate, and disease development. The epigenetic regulation of gene expression and the regulation of cell fate is mainly governed by deoxyribonucleic acid (DNA) methylation, histone modification, and noncoding RNAs (ncRNAs). Tissue engineering utilizes DSCs as a target. Tissue engineering therapies are based on the multipotent regenerative potential of DSCs. It is believed that epigenetic factors are essential for maintaining the multipotency of DSCs. A wide range of host and environmental factors influence stem cell differentiation and differentiation commitment, of which epigenetic regulation is critical. Several lines of evidence have shown that epigenetic modification of DNA and DNA-correlated histones are necessary for determining cells' phenotypes and regulating stem cells' pluripotency and renewal capacity. It is increasingly recognized that nuclear enzyme activities, such as histone deacetylases, can be used pharmacologically to induce stem cell differentiation and dedifferentiation. In this review, the role of epigenetic in dental and oral regenerative medicine by different types of dental stem cells is discussed in two new and promising areas of medical and biological researches in recent studies (2010-2022).

Progress in the Study of Non-Coding RNAs in Multidifferentiation Potential of Dental-Derived Mesenchymal Stem Cells

For decades, the desire for tissue regeneration has never been quenched. Dental-derived mesenchymal stem cells (DMSCs), with the potential of self-renewal and multi-directional differentiation, have attracted much attention in this topic. Growing evidence suggests that non-coding RNAs (ncRNAs) can activate various regulatory processes. Even with a slight decrease or increase in expression, ncRNAs can weaken or even subvert cellular fate. Therefore, a systematic interpretation of ncRNAs that guide the differentiation of DMSCs into cells of other tissue types is urgently needed. In this review, we introduce the roles of ncRNAs in the differentiation of DMSCs, such as osteogenic differentiation, odontogenic differentiation, neurogenic differentiation, angiogenic differentiation and myogenic differentiation. Additionally, we illustrate the regulatory mechanisms of ncRNAs in the differentiation of DMSCs, such as epigenetic regulation, transcriptional regulation, mRNA modulation, miRNA sponges and signalling. Finally, we summarize the types and mechanisms of ncRNAs in the differentiation of DMSCs, such as let-7 family, miR-17∼92 family, miR-21, lncRNA H19, lncRNA ANCR, lncRNA MEG3, circRNA CDR1as and CircRNA SIPA1L1. If revealing the intricate relationship between ncRNAs and pluripotency of DMSCs 1 day, the application of DMSCs in regenerative medicine and tissue engineering will be improved. Our work could be an important stepping stone towards this future.

Specific microRNAs regulate dental pulp stem cell behavior

INTRODUCTION

MicroRNAs (miRNAs), small non-coding RNA, control the translation of messenger RNAs into proteins. miRNAs have a crucial role in regulating the diverse biological processes of many physiological and pathological activities. The aim of this systematic review is to explore various functions of miRNAs in the regulation of dental pulp stem cells (DPSCs) behavior.

METHODS

The articles were searched in PubMed, SCOPUS and ISI Web of Science database using designated keywords. Full-length manuscripts published in English in peer-reviewed journals relevant to the role of miRNAs in DPSC functions were included and reviewed by 2 independent researchers.

RESULTS

The original search of the database generated 299 studies. One hundred and two duplicate studies were removed. After their exclusion, 48 studies were selected for review. miRNAs have shown to modulate the stemness and differentiation of various mesenchymal stem cells. The miRNAs expression profiles in DPSCs were differed compared with other cell types and have been demonstrated to regulate the levels of proteins crucial for promoting or inhibiting DPSC proliferation as well as differentiation. Further, miRNAs also modulate inflammatory processes in dental pulp.

CONCLUSION

miRNAs have various function upon the regulation of DPSCs and understanding these roles of miRNAs is crucial for the development of new therapeutics in regenerative dental medicine. With the advancing technologies, the utilization of miRNA technology could revolutionarily change the future of regenerative endodontics.

Characterization of circulating molecules and activities in plasma of patients after allogeneic and autologous intraoral bone grafting procedures: a prospective randomized controlled clinical trial in humans

Background

The objective was to assess whether intraoral bone augmentation procedures have an impact on the patient’s plasma levels of circulating nucleic acids, exosomes, miRNA levels and caspase activities. The null hypothesis was tested, that no significant differences between the two groups will be found.

Methods

In this prospective randomized controlled clinical trial 35 systemically healthy non-smoking participants were randomly allocated using sealed envelopes by a blinded clinician not involved in the clinical setting. Plasma samples were collected preoperatively and 3 times postoperatively (immediately, 5 weeks and 4 months postoperatively). The test group consisted of twenty-five patients who received allogeneic bone grafting material and the control group of ten patients who received autologous bone grafts. Levels of cell-free DNA (cfDNA) and microRNAs (miR-21, miR-27a, miR-218) were quantified by real-time PCR, caspase activities and exosome concentrations were determined by ELISA.

Results

Statistical evaluation reveled a significantly higher exosome level before surgery (p = 0.013) and the first postsurgical sample (p = 0.017) in the control group compared to the test group. The levels of miR-27a and miR-218 significantly differed between the plasma samples before surgery and after surgery in both groups. The levels of miR-21 only significantly differed between the pre- and postsurgical plasma samples in the test group, but not in the control group. All patients completed the study, no adverse events were recorded.

Conclusions

Our data show the diagnostic potential of the plasma levels of miR-27a, miR-218 and miR-21 in detecting changes in bone metabolism after alveolar bone augmentation. Our very promising results indicate that there might be a high diagnostic potential in evaluating the plasma levels of the before mentioned miRNAs in order to detect bone resorption activities before they become clinically relevant.

Trial registration Ethical commission of the Ärztekammer Hamburg, Germany (PV5211) on 11/03/2016 as well as by the German Registry of Clinical Studies (DRKS 00,013,010) on 30/07/2018 (http://apps.who.int/trialsearch/).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-02036-7.

The Effect of Diabetes Mellitus on IGF Axis and Stem Cell Mediated Regeneration of the Periodontium

Periodontitis and diabetes mellitus (DM) are two of the most common and challenging health problems worldwide and they affect each other mutually and adversely. Current periodontal therapies have unpredictable outcome in diabetic patients. Periodontal tissue engineering is a challenging but promising approach that aims at restoring periodontal tissues using one or all of the following: stem cells, signalling molecules and scaffolds. Mesenchymal stem cells (MSCs) and insulin-like growth factor (IGF) represent ideal examples of stem cells and signalling molecules. This review outlines the most recent updates in characterizing MSCs isolated from diabetics to fully understand why diabetics are more prone to periodontitis that theoretically reflect the impaired regenerative capabilities of their native stem cells. This characterisation is of utmost importance to enhance autologous stem cells based tissue regeneration in diabetic patients using both MSCs and members of IGF axis.

Bioinformatics Analysis Identified miR-584-5p and Key miRNA-mRNA Networks Involved in the Osteogenic Differentiation of Human Periodontal Ligament Stem Cells

Human periodontal ligament cells (PDLCs) play an important role in periodontal tissue stabilization and function. In the process of osteogenic differentiation of PDLSCs, the regulation of molecular signal pathways are complicated. In this study, the sequencing results of three datasets on GEO were used to comprehensively analyze the miRNA-mRNA network during the osteogenic differentiation of PDLSCs. Using the GSE99958 and GSE159507, a total of 114 common differentially expressed genes (DEGs) were identified, including 62 up-regulated genes and 52 down-regulated genes. GO enrichment analysis was performed. The up-regulated 10 hub genes and down-regulated 10 hub genes were screened out by protein-protein interaction network (PPI) analysis and STRING in Cytoscape. Similarly, differentially expressed miRNAs (DEMs) were selected by limma package from GSE159508. Then, using the miRwalk website, we further selected 11 miRNAs from 16 DEMs that may have a negative regulatory relationship with hub genes. In vitro RT-PCR verification revealed that nine DEMs and 18 hub genes showed the same trend as the RNA-seq results during the osteogenic differentiation of PDLSCs. Finally, using miR-584-5p inhibitor and mimics, it was found that miR-584-5p negatively regulates the osteogenic differentiation of PDLSCs in vitro. In summary, the present results found several potential osteogenic-related genes and identified candidate miRNA-mRNA networks for the further study of osteogenic differentiation of PDLSCs.

Research hotspots and trends of microRNA in periodontology and dental implantology: a bibliometric analysis

Background

Periodontal disease is a leading cause of tooth loss, and microRNA (miRNA) has been shown to regulate various biological processes. This study aimed to quantitatively analyze the literature related to miRNA in periodontology and dental implantology and summarize the research hotspots and trends in this field.

Methods

Literature records from 1985 to 2020 were obtained from the Web of Science Core Collection database. After manual selection, the data was used for cooperative network analysis, keyword co-occurrence analysis, and reference co-citation analysis and visualized by CiteSpace.

Results

A total of 287 papers were analyzed between 2007 and 2020, and more than 95% of them were published in the past decade. The largest number of publications were from China, followed by the USA and Japan. The direct cooperation among the productive institutions was not close. At present, most of the research belongs to the discipline of dentistry, oral surgery, cell biology, and molecular biology. Literature clusters generated by reference co-citation analysis and keyword co-occurrence network showed that previous studies mainly focused on four hotspots: periodontal ligament stem cells (PDLSCs), the pathological process of periodontitis, osteogenic differentiation/bone regeneration, and the competing endogenous RNA (ceRNA) network.

Conclusions

The therapeutic potential of miRNA in promoting bone formation and how the ceRNA network contributes to miRNA regulation at a deeper level have become the two main research trends of this field.

Genome-wide DNA (hydroxy) methylation reveals the individual epigenetic landscape importance on osteogenic phenotype acquisition in periodontal ligament cells

BACKGROUND

Mesenchymal cells' biology has been an important investigative tool to maximize bone regeneration through tissue engineering. Here we used mesenchymal cells from periodontal ligament (PDLCs) with high (h-) and low (l-) osteogenic potential, isolated from different donors, to investigate the impact of the individual epigenetic and transcriptional profiles on the osteogenic potential.

METHODS

Genome-wide and gene-specific DNA (hydroxy) methylation, mRNA expression and immunofluorescence analysis were carried out in h- and l-PDLCs at DMEM (non-induced to osteogenesis) and OM (induced-3rd and 10th days of osteogenic differentiation) groups in vitro.

RESULTS

Genome-wide results showed distinct epigenetic profile among PDLCs with most of the differences on 10th day of OM; DMEMs showed higher concentrations (xOM) of differentially methylated probes in gene body, intronic and open sea (3rd day), increasing this concentration in TSS200 and island regions, at 10 days. At basal levels, h- and l-PDLCs showed different transcriptional profiles; l-PDLCs demonstrated higher levels of NANOG/OCT4/SOX2, BAPX1, DNMT3A, TET1/3, and lower levels of RUNX2 transcripts, confirmed by NANOG/OCT4 and RUNX2 immunofluorescence. After osteogenic induction, the distinct transcriptional profile of multipotentiality genes was maintained among PDLCs. In l-PDLCs, the anti-correlation between DNA methylation and gene expression in RUNX2 and NANOG indicates methylation could play a role in modulating both transcripts.

CONCLUSIONS

Epigenetic and transcriptional distinct profiles detected at basal levels among PDLCs were maintained after osteogenic induction. We cannot discard the existence of a complex that represses osteogenesis, suggesting the individual donors' characteristics have significant impact on the osteogenic phenotype acquisition.

The Gingiva from the Tissue Surrounding the Bone to the Tissue Regenerating the Bone: A Systematic Review of the Osteogenic Capacity of Gingival Mesenchymal Stem Cells in Preclinical Studies

The current review aims to systematically assess the osteogenic capacity of gingiva-derived mesenchymal stem cells (GMSCs) in preclinical studies. A comprehensive electronic search of PubMed, Embase, Web of Science, and Scopus databases, as well as a manual search of relevant references, was performed in June 2020 without date or language restrictions. Eligibility criteria were the following: studies that compared mesenchymal stem cells (MSCs) derived from the gingiva with other MSC sources (in vitro or in vivo) or cell-free scaffold (in vivo) and studies that reported at least one of the following outcomes: osteogenic potential and new bone formation for in vitro and in vivo, respectively. Moreover, the assessment of included studies was conducted using appropriate guidelines. From 646 initial retrieved studies, 35 full-text articles were subjected to further screening and 26 studies were selected (20 in vitro studies and 6 in vivo studies). GMSCs showed great proliferation capacity and expressed recognized mesenchymal stem cell markers, particularly CD90. In vitro, MSC sources including GMSCs were capable of undergoing osteogenic differentiation with less ability in GMSCs, while most in vivo studies confirmed the capacity of GMSCs to regenerate bony defects. Concerning the assessment of methodological quality, in vitro studies met the relevant guideline except in five areas: the sample size calculation, randomization, allocation concealment, implementation, and blinding, and in vivo publications had probably low risk of bias in most domains except in three areas: allocation concealment, attrition, and blinding items.

The role of microRNAs in the osteogenic and chondrogenic differentiation of mesenchymal stem cells and bone pathologies

Mesenchymal stem cells (MSCs) have been identified in many adult tissues. MSCs can regenerate through cell division or differentiate into adipocytes, osteoblasts and chondrocytes. As a result, MSCs have become an important source of cells in tissue engineering and regenerative medicine for bone tissue and cartilage. Several epigenetic factors are believed to play a role in MSCs differentiation. Among these, microRNA (miRNA) regulation is involved in the fine modulation of gene expression during osteogenic/chondrogenic differentiation. It has been reported that miRNAs are involved in bone homeostasis by modulating osteoblast gene expression. In addition, countless evidence has demonstrated that miRNAs dysregulation is involved in the development of osteoporosis and bone fractures. The deregulation of miRNAs expression has also been associated with several malignancies including bone cancer. In this context, bone-associated circulating miRNAs may be useful biomarkers for determining the predisposition, onset and development of osteoporosis, as well as in clinical applications to improve the diagnosis, follow-up and treatment of cancer and metastases. Overall, this review will provide an overview of how miRNAs activities participate in osteogenic/chondrogenic differentiation, while addressing the role of miRNA regulatory effects on target genes. Finally, the role of miRNAs in pathologies and therapies will be presented.

The Role of Noncoding RNAs in Osteogenic Differentiation of Human Periodontal Ligament Stem Cells

Chronic inflammatory diseases, including periodontitis, are the most common causes of bone tissue destruction. Periodontitis often leads to loss of connective tissue homeostasis and reduced alveolar bone levels. Human periodontal ligament stem cells (PDLSCs), a population of multipotent stem cells derived from periodontal ligament tissues, are considered as candidate cells for the regeneration of alveolar bone and periodontal tissues. Periodontitis impairs the osteogenic differentiation of human PDLSCs. Noncoding RNAs (ncRNAs), including long noncoding RNA (lncRNA), microRNA (miRNA), and circular RNA (circRNA), have been proposed as vital regulators influencing several differentiation processes including bone regeneration. Still, the molecular mechanisms of ncRNAs regulating osteogenic differentiation of human PDLSCs remain poorly understood. Exploring the influence of ncRNAs in the process of osteogenic differentiation of human PDLSCs may provide novel therapeutic strategies for tissue regeneration as the regeneration of the lost periodontium is the ultimate goal of periodontal therapy.

MicroRNAs Modulate Signaling Pathways in Osteogenic Differentiation of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) have been identified in many adult tissues and they have been closely studied in recent years, especially in view of their potential use for treating diseases and damaged tissues and organs. MSCs are capable of self-replication and differentiation into osteoblasts and are considered an important source of cells in tissue engineering for bone regeneration. Several epigenetic factors are believed to play a role in the osteogenic differentiation of MSCs, including microRNAs (miRNAs). MiRNAs are small, single-stranded, non-coding RNAs of approximately 22 nucleotides that are able to regulate cell proliferation, differentiation and apoptosis by binding the 3' untranslated region (3'-UTR) of target mRNAs, which can be subsequently degraded or translationally silenced. MiRNAs control gene expression in osteogenic differentiation by regulating two crucial signaling cascades in osteogenesis: the transforming growth factor-beta (TGF-β)/bone morphogenic protein (BMP) and the Wingless/Int-1(Wnt)/β-catenin signaling pathways. This review provides an overview of the miRNAs involved in osteogenic differentiation and how these miRNAs could regulate the expression of target genes.

MiR-153-3p inhibits osteogenic differentiation of periodontal ligament stem cells through KDM6A-induced demethylation of H3K27me3

BACKGROUND AND OBJECTIVE

Periodontal ligament stem cells (PDLSCs) have potential for osteogenic differentiation and show a great foreground in treating bone diseases. Histone three lysine 27 (H3K27) demethylase lysine demethylase 6A (KDM6A) is a critical epigenetic modifier and plays an important role in regulating osteogenic differentiation. Multiple microRNAs have been found to play important roles in osteogenesis. The aim of this study was to explore the mechanisms underlying the roles of miR-153-3p and KDM6A in PDLSC osteogenesis.

METHODS

The levels of the osteogenic markers alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2), and osteopontin (OPN) were measured by western blotting. Osteoblast activity and mineral deposition were detected by ALP and Alizarin red S (ARS) staining. The levels of miR-153-3p and KDM6A were measured by quantitative real-time PCR (qRT-PCR). A luciferase reporter assay was used to confirm the interaction between KDM6A and miR-153-3p. Gain-of-function and loss-of-function assays were performed to identify the roles of miR-153-3p and KDM6A in the osteogenic differentiation of PDLSCs.

RESULTS

In osteogenic PDLSCs, the expression of KDM6A, ALP, Runx2, and OPN was upregulated, whereas that of miR-153-3p was downregulated. miR-153-3p downregulation or KDM6A overexpression promoted the osteogenic differentiation of PDLSCs, as demonstrated by increases in ALP activity, matrix mineralization, and ALP, Runx2, and OPN expression. KDM6A was confirmed to be a target of miR-153-3p, and KDM6A overexpression reversed the inhibitory effect of miR-153-3p mimic on PDLSC osteogenesis. KDM6A promoted ALP, Runx2, and OPN expression through the demethylation of H3K27me3 on the promoter regions of these genes.

CONCLUSION

miR-153-3p inhibited PDLSC osteogenesis by targeting KDM6A and inhibiting ALP, Runx2, and OPN transcription. These findings provide latent hope for PDLSCs application in periodontal therapy.

MiR-218 affects hypertrophic differentiation of human mesenchymal stromal cells during chondrogenesis via targeting RUNX2, MEF2C, and COL10A1

Background

Human mesenchymal stromal cells (MSC) hold hopes for cartilage regenerative therapy due to their chondrogenic differentiation potential. However, undesirable occurrence of calcification after ectopic transplantation, known as hypertrophic degeneration, remains the major obstacle limiting application of MSC in cartilage tissue regeneration approaches. There is growing evidence that microRNAs (miRs) play essential roles in post-transcriptional regulation of hypertrophic differentiation during chondrogenesis. Aim of the study was to identify new miR candidates involved in repression of hypertrophy-related targets.

Methods

The miR expression profile in human articular chondrocytes (AC) was compared to that in hypertrophic chondrocytes derived from human MSC by microarray analysis, and miR expression was validated by qPCR. Putative targets were searched by in silico analysis and validated by miR reporter assay in HEK293T, by functional assays (western blotting and ALP-activity) in transiently transfected SaOS-2 cells, and by a miR pulldown assay in human MSC. The expression profile of miR-218 was assessed by qPCR during in vitro chondrogenesis of MSC and re-differentiation of AC. MSC were transfected with miR-218 mimic, and differentiation outcome was assessed over 28 days. MiR-218 expression was quantified in healthy and osteoarthritic cartilage of patients.

Results

Within the top 15 miRs differentially expressed between chondral AC versus endochondral MSC differentiation, miR-218 was selected as a candidate miR predicted to target hypertrophy-related genes. MiR-218 was downregulated during chondrogenesis of MSC and showed a negative correlation to hypertrophic markers, such as COL10A1 and MEF2C. It was confirmed in SaOS-2 cells that miR-218 directly targets hypertrophy-related COL10A1, MEF2C, and RUNX2, as a gain of ectopic miR-218 mimic caused drop in MEF2C and RUNX2 protein accumulation, with attenuation of COL10A1 expression and significant concomitant reduction of ALP activity. A miR pulldown assay confirmed that miR-218 directly targets RUNX2, MEF2C in human MSC. Additionally, the gain of miR-218 in human MSC attenuated hypertrophic markers (MEF2C, RUNX2, COL10A1, ALPL), although with no boost of chondrogenic markers (GAG deposition, COL2A1) due to activation of WNT/β-catenin signaling. Moreover, no correlation between miR-218 expression and a pathologic phenotype in the cartilage of osteoarthritis (OA) patients was found.

Conclusions

Although miR-218 was shown to target pro-hypertrophic markers MEF2C, COL10A1, and RUNX2 in human MSC during chondrogenic differentiation, overall, it could not significantly reduce the hypertrophic phenotype or boost chondrogenesis. This could be explained by a concomitant activation of WNT/β-catenin signaling counteracting the anti-hypertrophic effects of miR-218. Therefore, to achieve a full inhibition of the endochondral pathway, a whole class of anti-hypertrophic miRs, including miR-218, needs to be taken into consideration.

Epigenetic Regulation of Dental Pulp Stem Cell Fate

Epigenetic regulation, mainly involving DNA methylation, histone modification, and noncoding RNAs, affects gene expression without modifying the primary DNA sequence and modulates cell fate. Mesenchymal stem cells derived from dental pulp, also called dental pulp stem cells (DPSCs), exhibit multipotent differentiation capacity and can promote various biological processes, including odontogenesis, osteogenesis, angiogenesis, myogenesis, and chondrogenesis. Over the past decades, increased attention has been attracted by the use of DPSCs in the field of regenerative medicine. According to a series of studies, epigenetic regulation is essential for DPSCs to differentiate into specialized cells. In this review, we summarize the mechanisms involved in the epigenetic regulation of the fate of DPSCs.

Recent Advances on Drug-Loaded Mesenchymal Stem Cells With Anti-neoplastic Agents for Targeted Treatment of Cancer

Mesenchymal stem cells (MSCs), as an undifferentiated group of adult multipotent cells, have remarkable antitumor features that bring them up as a novel choice to treat cancers. MSCs are capable of altering the behavior of cells in the tumor microenvironment, inducing an anti-inflammatory effect in tumor cells, inhibiting tumor angiogenesis, and preventing metastasis. Besides, MSCs can induce apoptosis and inhibit the proliferation of tumor cells. The ability of MSCs to be loaded with chemotherapeutic drugs and release them in the site of primary and metastatic neoplasms makes them a preferable choice as targeted drug delivery procedure. Targeted drug delivery minimizes unexpected side effects of chemotherapeutic drugs and improves clinical outcomes. This review focuses on recent advances on innate antineoplastic features of MSCs and the effect of chemotherapeutic drugs on viability, proliferation, and the regenerative capacity of various kinds of MSCs. It also discusses the efficacy and mechanisms of drug loading and releasing procedures along with in vivo and in vitro preclinical outcomes of antineoplastic effects of primed MSCs for clinical prospection.

[Functions of non-coding RNAs in the osteogenic differentiation of human periodontal ligament-derived cells]

Human periodontal ligament-derived cells serve as an important source of seeding cells in periodontal regenerative medicine, and their osteogenic potential is closely related to alveolar bone repair and periodontal regeneration. Non-coding RNA (ncRNA), such as microRNA, long non-coding RNA, and circular RNA, play important roles in the regu-lation of osteogenic genes in human periodontal ligament-derived cells. In this review, we summarize the target genes, path-ways, and functions of the ncRNA network during osteogenic differentiation of periodontal ligament-derived cells.

Overview of noncoding RNAs involved in the osteogenic differentiation of periodontal ligament stem cells

Periodontal diseases are infectious diseases that are characterized by progressive damage to dental support tissue. The major goal of periodontal therapy is to regenerate the periodontium destroyed by periodontal diseases. Human periodontal ligament (PDL) tissue possesses periodontal regenerative properties, and periodontal ligament stem cells (PDLSCs) with the capacity for osteogenic differentiation show strong potential in clinical application for periodontium repair and regeneration. Noncoding RNAs (ncRNAs), which include a substantial portion of poly-A tail mature RNAs, are considered “transcriptional noise.” Recent studies show that ncRNAs play a major role in PDLSC differentiation; therefore, exploring how ncRNAs participate in the osteogenic differentiation of PDLSCs may help to elucidate the underlying mechanism of the osteogenic differentiation of PDLSCs and further shed light on the potential of stem cell transplantation for periodontium regeneration. In this review paper, we discuss the history of PDLSC research and highlight the regulatory mechanism of ncRNAs in the osteogenic differentiation of PDLSCs.

Genome-wide identification of long noncoding RNAs and their competing endogenous RNA networks involved in the odontogenic differentiation of human dental pulp stem cells

BACKGROUND

Long noncoding RNAs (lncRNAs) play an important role in the multiple differentiations of mesenchymal stem cells (MSCs). However, few studies have focused on the regulatory mechanism of lncRNAs in the odontogenic differentiation of human dental pulp stem cells (hDPSCs).

METHODS

hDPSCs were induced to differentiate into odontoblasts in vitro, and the expression profiles of lncRNAs, microRNAs (miRNAs), and messenger RNAs (mRNAs) in differentiated and undifferentiated cells were obtained by microarray. Bioinformatics analyses including Gene Ontology (GO) analysis, pathway analysis, and binding site prediction were performed for functional annotation of lncRNA. miRNA/odontogenesis-related gene networks and lncRNA-associated ceRNA networks were constructed. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) was used to verify the expression of selected genes. RNA fluorescence in situ hybridization (FISH), qRT-PCR, and western blot analysis were used to explore the location and function of lncRNA-G043225. Dual-luciferase reporter assay was performed to confirm the binding sites of miR-588 with G043225 and Fibrillin 1 (FBN1).

RESULTS

We identified 132 lncRNAs, 114 miRNAs, and 172 mRNAs were differentially expressed. GO analysis demonstrated that regulation of the neurogenic locus notch homolog (Notch), Wnt, and epidermal growth factor receptor (ERBB) signaling pathways and activation of mitogen-activated protein kinase (MAPK) activity were related to odontogenic differentiation. Pathway analysis indicated that the most significant pathway was the forkhead box O (FoxO) signaling pathway, which is related to odontogenic differentiation. Two odontogenesis-related gene-centered lncRNA-associated ceRNA networks were successfully constructed. The qRT-PCR validation results were consistent with the microarray analysis. G043225 mainly locating in cytoplasm was proved to promote the odontogenic differentiation of hDPSCs via miR-588 and FBN1.

CONCLUSION

This is the first study revealing lncRNA-associated ceRNA network during odontogenic differentiation of hDPSCs using microarray, and it could provide clues to explore the mechanism of action at the RNA-RNA level as well as novel treatments for dentin regeneration based on stem cells.

Pilot GWAS of caries in African-Americans shows genetic heterogeneity

BACKGROUND

Dental caries is the most common chronic disease in the US and disproportionately affects racial/ethnic minorities. Caries is heritable, and though genetic heterogeneity exists between ancestries for a substantial portion of loci associated with complex disease, a genome-wide association study (GWAS) of caries specifically in African Americans has not been performed previously.

METHODS

We performed exploratory GWAS of dental caries in 109 African American adults (age > 18) and 96 children (age 3-12) from the Center for Oral Health Research in Appalachia (COHRA1 cohort). Caries phenotypes (DMFS, DMFT, dft, and dfs indices) assessed by dental exams were tested for association with 5 million genotyped or imputed single nucleotide polymorphisms (SNPs), separately in the two age groups. The GWAS was performed using linear regression with adjustment for age, sex, and two principal components of ancestry. A maximum of 1 million adaptive permutations were run to determine empirical significance.

RESULTS

No loci met the threshold for genome-wide significance, though some of the strongest signals were near genes previously implicated in caries such as antimicrobial peptide DEFB1 (rs2515501; p = 4.54 × 10- 6) and TUFT1 (rs11805632; p = 5.15 × 10- 6). Effect estimates of lead SNPs at suggestive loci were compared between African Americans and Caucasians (adults N = 918; children N = 983). Significant (p < 5 × 10- 8) genetic heterogeneity for caries risk was found between racial groups for 50% of the suggestive loci in children, and 12-18% of the suggestive loci in adults.

CONCLUSIONS

The genetic heterogeneity results suggest that there may be differences in the contributions of genetic variants to caries across racial groups, and highlight the critical need for the inclusion of minorities in subsequent and larger genetic studies of caries in order to meet the goals of precision medicine and to reduce oral health disparities.

MICROmanagement of Runx2 Function in Skeletal Cells

Purpose of Review-

Precise and temporal expression of Runx2 and its regulatory transcriptional network is a key determinant for the intricate cellular and developmental processes in adult bone tissue formation. This review analyzes how microRNA functions to regulate this network, and how dysregulation results in bone disorders.

Recent Findings-

Similar to other biologic processes, microRNA (miRNA/miR) regulation is undeniably indispensable to bone synthesis and maintenance. There exists a miRNA-RUNX2 network where RUNX2 regulates the transcription of miRs, or is post transcriptionally regulated by a class of miRs, forming a variety of miR-RUNX2 regulatory pathways which regulate osteogenesis.

Summary-

The current review provides insights to understand transcriptional-post transcriptional regulatory network governed by Runx2 and osteogenic miRs, and is based largely from in vitro and in vivo studies. When taken together, this article discusses a new regulatory layer of bone tissue specific gene expression by RUNX2 influenced via miRNA.

Involvement of miR-146a-5p/neurogenic locus notch homolog protein 1 in the proliferation and differentiation of STRO-1+ human dental pulp stem cells

Dental pulp stem cells (DPSCs) and stem cells from the apical papilla (SCAPs) are oral mesenchymal stem cells capable of self-renewal and have a potential for multilineage differentiation. Increasing evidence shows that microRNAs (miRNAs) play important roles in stem cell biology. Here, we focused on exploring miR-146a-5p and its relationship to the undifferentiated status of STRO-1⁺ SCAPs and STRO-1⁺ DPSCs, as well as its role during STRO-1⁺ DPSC differentiation and proliferation. Our data indicated that baseline miR-146a-5p expression is significantly lower in STRO-1⁺ SCAPs than in STRO-1⁺ DPSCs and increased in the latter during osteogenic induction. Moreover, we identified miR-146a-5p as a key miRNA that promotes osteo/odontogenic differentiation of STRO-1⁺ DPSCs and attenuates cell proliferation. Additionally, it was observed that STRO-1⁺ DPSC mineralization results in the downregulation of notch receptor 1 (NOTCH1) and hes family bHLH transcription factor 1 (HES1). Interference with neurogenic locus notch homolog protein 1 (Notch 1) signaling was verified to enhance differentiation and suppress STRO-1⁺ DPSC proliferation. It was further observed that miR-146a-5p directly targets the 3'-untranslated region (3'-UTR) of NOTCH1 and inhibits expression of both NOTCH1 and HES1mRNAs and Notch 1 and transcription factor HES-1 (HES-1) proteins in STRO-1⁺ DPSCs. We conclude that miR-146a-5p exerts its regulatory effect on STRO-1⁺ DPSC differentiation and proliferation partially by suppressing Notch signaling.

Role of microRNAs in osteogenesis of stem cells

Osteogenic differentiation is a controlled developmental process in which external and internal factors including cytokines, growth factors, transcription factors (TFs), signaling pathways and microRNAs (miRNAs) play important roles. Various stimulatory and inhibitory TFs contribute to osteogenic differentiation and are responsible for bone development. In addition, cross-talk between several complex signaling pathways regulates the osteogenic differentiation of some stem cells. Although much is known about regulatory genes and signaling pathways in osteogenesis, the role of miRNAs in osteogenic differentiation still needs to be explored. miRNAs are small, approximately 22 nucleotides, single-stranded nonprotein coding RNAs which are abundant in many mammalian cell types. They paly significant regulated roles in various biological processes and serve as promising biomarkers for disease states. Recently, emerging evidence have shown that miRNAs are the key regulators of osteogenesis of stem cells. They may endogenously regulate osteogenic differentiation of stem cells through direct targeting of positive or negative directors of osteogenesis and depending on the target result in the promotion or inhibition of osteogenic differentiation. This review aims to provide a general overview of miRNAs participating in osteogenic differentiation of stem cells and explain their regulatory effect based on the genes targeted with these miRNAs.

MiRNA-218 regulates osteoclast differentiation and inflammation response in periodontitis rats through Mmp9

Periodontitis is a multiple infection and inflammatory disease featured by connective tissue homeostasis loss, periodontal inflammation, and alveolar bone resorption. MicroRNAs (miRNAs) are involved in the mediation of a large scale of pathological processes. Here, we show that miRNA-218 provides protective effect on periodontitis via regulation of matrix metalloproteinase-9 (Mmp9). This pathway is aberrant in periodontium from rats with periodontitis and human periodontal ligament progenitor cells stimulated by lipopolysaccharide, with downregulation of miR-218 and higher levels of Mmp9 compared with periodontium from healthy rats and cells without stimulation. Overexpression of miR-218 can suppress the degradation of Collagen Types I and IV and dentin sialoprotein (DSP), attenuate osteoclast formation, and inhibit the secretion of proinflammatory cytokines. On the other hand, overexpression of Mmp9 promotes the degradation of Collagen Types I and IV and DSP as well as RANKL-induced osteoclast formation and elevates inflammatory factors levels. Furthermore, the inhibitory effect of miR-218 was prevented by rescuing the Mmp9 expression. In addition, we also have showed that miR-218 was able to attenuate bone resorption and inflammation in a periodontitis rat model. Collectively, our findings therefore suggest that miR-218 acts as a protective role in periodontitis through the regulation of Mmp9.

Long non-coding RNA H19/SAHH axis epigenetically regulates odontogenic differentiation of human dental pulp stem cells

Long noncoding RNAs (lncRNAs) are emerging as important regulators in molecular processes and may play vital roles in odontogenic differentiation of human dental pulp stem cells (hDPSCs). However, their functions remain to be elucidated. As lncRNA H19 is one of the most classical lncRNA, which plays essential roles in cellular differentiation, thus we explored the effects and mechanisms of H19 in odontogenic differentiation of hDPSCs. Stable overexpression and knockdown of H19 in hDPSCs were constructed using recombinant lentiviruses containing H19 and short hairpin-H19 expression cassettes, respectively. Alkaline phosphatase (ALP) assay, Alizarin red staining assay, von kossa staining, quantitative polymerase chain reaction (qPCR), Western blot analysis, and immunofluorescent staining results indicated that overexpression of H19 in hDPSCs positively regulates the odontogenic differentiation of hDPSCs, while knockdown of H19 in hDPSCs inhibits odontogenic differentiation of hDPSCs. Further, we found that H19 promotes the odontogenic differentiation of hDPSCs through S-adenosylhomocysteine hydrolase (SAHH) epigenetically regulates the methylation and expression of distal-less homeobox (DLX3) gene. Herein, for the first time, we determined that H19/SAHH axis epigentically regulates odontogenic differentiaiton of hDPSCs by inhibiting the DNA methyltransferase 3B (DNMT3B)-mediated methylation of DLX3. Our findings provide a new insight into how H19/SAHH axis play its role in odontogenic differentiation of hDPSCs, and would be helpful in developing therapeutic approaches for dentin regeneration based on stem cells.

Downregulation of microRNA-143-5p is required for the promotion of odontoblasts differentiation of human dental pulp stem cells through the activation of the mitogen-activated protein kinases 14-dependent p38 mitogen-activated protein kinases signaling pathway

MicroRNAs (miRNAs) play critical roles in various biological processes including cell differentiation. Some researchers suggested that the p38 mitogen-activated protein kinases (MAPK) signaling pathway had an effect on regulating the odontoblastic differentiation of human dental pulp stem cells (hDPSCs). This study focuses on the effects of miR-143-5p on hDPSCs by regulating the p38 MAPK signaling pathway. The targeting relationship of MAPK14 and miR-143-5p targets were verified by TargetScan and dual-luciferase reporter gene assay. Through overexpression of miR-143-5p or silencing of miR-143-5p, expressions of miR-143-5p, MAPK14, Ras, MAPK kinase (MKK) 3/6, dentin sialophosphoprotein (DSPP), alkaline phosphatase (ALP), and osteocalcin (OCN) were detected by reverse transcription quantitative polymerase chain reaction. Protein expressions of MAPK14, Ras, and MKK3/6 were determined by western blot analysis. ALP and alizarin red S staining were used to detect mineralization. Initially, MAPK14 was found to be negatively regulated by miR-143-5p. Meanwhile, the upregulated miR-143-5p decreased the p38 MAPK signaling pathway related genes (MAPK14, Ras, and MKK3/6) and odontoblastic differentiation markers (ALP, DSPP, and OCN) expression. On the contrary, the downregulated miR-143-5p increased the p38 MAPK signaling pathway related genes (MAPK14, Ras, and MKK3/6) and odontoblastic differentiation markers (ALP, DSPP, and OCN) expression. Furthermore, ALP activity and mineralized nodules increased after downregulation of miR-143-5p, and after its upregulation, ALP activity and mineralized nodules decreased. Our data suggest that poor expression of miR-143-5p promotes hDPSCs odontoblastic differentiation through the activation of the p38 MAPK signaling pathway by upregulating MAPK14.

MiR-218 regulated cardiomyocyte differentiation and migration in mouse embryonic stem cells by targeting PDGFRα

MicroRNAs (miRNAs) have been identified as key players in cardiogenesis and heart pathophysiological processes. However, many miRNAs are still not recognized for their roles in cardiomyocytes differentiation. In this study, we evaluated the effects of microRNA-218 (miR-218) in cardiomyocyte differentiation of the mouse embryonic stem cells (ESCs) in vitro. The percentage of the beating embryoid bodies (EBs) in miR-218 mimic-treated cells was reduced to 32% compared with miR-218 mimic negative control (56%) on day 5 + 3. The amplitude of the intracellular Ca²⁺ transients in the cardiomyocytes derived from ESCs was reduced upon miR-218 overexpression, followed by the decreased calcium-related proteins and cell junction proteins expressions. Besides, miR-218 expression in ESCs was related to the directional spreading ability of EBs during differentiation. The increased expression of miR-218 could promote the migration of ESCs in vitro, while the decreased expression of miR-218 could inhibit the migration by the transwell experiment. Meanwhile, miR-218 could regulate cell migration-related proteins Cdc42 and Rac1. Platelet-derived growth factor receptor α (PDGFRα) was further confirmed to be a direct target of miR-218 both physically and functionally by dual-luciferase reporter assay. Our data further described that overexpression of PDGFRα rescued the miR-218-mediated inhibition of cardiomyocyte differentiation and restored the miR-218-mediated promotion of cell migration. In conclusion, miR-218 was demonstrated to exert an inhibitory function and promoted cell migration via targeting PDGFRα during cardiomyocyte differentiation from ESCs. The current study revealed the role of miR-218 and may provide an important hint for cardiomyocyte differentiation of ESCs and induced pluripotent stem cells.

Teeth-derived stem cells: A source for cell therapy

Cell therapy is one of the important therapeutic approaches in the treatment of many diseases such as cancer, degenerative diseases, and cardiovascular diseases. Among various cell types, which could be used as cell therapies, stem cell therapy has emerged as powerful tools in the treatment of several diseases. Multipotent stem cells are one of the main classes of stem cells that could originate from different parts of the body such as bone marrow, adipose, placenta, and tooth. Among several types of multipotent stem cells, tooth-derived stem cells (TDSCs) are associated with special properties such as accessible, easy isolation, and low invasive, which have introduced them as a good source for using in the treatment of several diseases such as neural injuries, liver fibrosis, and Cohrn's disease. Here, we provided an overview of TDSCs particular stem cells from human exfoliated deciduous teeth and clinical application of them. Moreover, we highlighted molecular mechanisms involved in the regulation of dental stem cells fate.

Downregulated microRNA-488 enhances odontoblast differentiation of human dental pulp stem cells via activation of the p38 MAPK signaling pathway

Human dental pulp stem cells (hDPSCs) are primarily derived from the pulp tissues of permanent third molar teeth. They were widely used in human bone tissue engineering. It was previously indicated that microRNA (miR) expressions are closely associated with hDPSCs development. However, the specific effect of miR-488 on hDPSCs still remains unclear. In this study, we aimed to investigate effects of miR-488 on the differentiation of hDPSCs into odontoblast cells through the p38 mitogen-activated protein kinases (MAPK) signaling pathway by binding to MAPK1. The hDPSCs were isolated and cultured in vitro. Dual-luciferase reporter gene assay was performed to test the relationship between MAPK1 (p38) and miR-488. Reverse transcription quantitative polymerase chain reaction and western blot analysis were used to detect the mRNA and protein expressions of p38 MAPK signaling pathway-related genes (MAPK1, Ras, and Mitogen-activated protein kinase kinase 3/6 [MKK3/6]), along with expressions of dentin Sialophosphoprotein (DSPP), alkaline phosphatase (ALP), and osteonectin (OCN). ALP staining and alizarin red staining were conducted to detect ALP activity and degree of mineralization. Initially, we found that MAPK1 was the target gene of miR-488. Besides, downregulation of miR-488 was observed to stimulate the p38 MAPK signaling pathway and to increase the messenger RNA and protein expressions of DSPP, ALP, and OCN. Furthermore, ALP activity and formation of a mineralized nodule in hDPSCs were enhanced upon downregulation of miR-488. The aforementioned findings provided evidence supporting that downregulation of miR-488 promotes odontoblastic differentiation of hDPSCs through the p38 MAPK signaling pathway by targeting MAPK1, paving the basis for further study about hDPSCs.

MicroRNA-218 Promotes Osteogenic Differentiation of Mesenchymal Stem Cells and Accelerates Bone Fracture Healing

As a regulator of osteogenesis, microRNA-218 (miR-218) is reported to promote osteogenesis of mesenchymal stem cells (MSCs). However, the in vivo osteogenic effect of miR-218 remains elusive. In this study, miR-218 was confirmed to promote osteogenic differentiation of MSCs by stimulating the alkaline phosphatase activity, calcium nodule formation, and osteogenic marker gene expression. For in vivo study, the miR-218-overexpressing BMSCs were locally administrated into the fracture sites in a femur fracture mouse model. Based on the X-rays, micro-computed tomography, mechanical testing, histology, and immunohistochemistry examinations, miR-218 overexpression improved new bone formation and accelerated fracture healing. These findings suggest that miR-218 may be a promising therapeutic target for bone repair in future clinical applications.

MicroRNA-543 functions as an osteogenesis promoter in human periodontal ligament-derived stem cells by inhibiting transducer of ERBB2, 2

BACKGROUND AND OBJECTIVE

Previous research has indicated that altered expression of microRNAs (miRNAs) is in connection with osteogenesis of human periodontal ligament-derived stem cells (hPDLSCs). We investigated the mechanisms by which miR-543 promotes osteogenic differentiation of hPDLSCs.

MATERIAL AND METHODS

First, the expression of miR-543 in hPDLSCs cultured with or without an osteogenic inductive cocktail was explored. Then, the function of miR-543 during osteogenesis of hPDLSCs was investigated by overexpressing and inhibiting miR-543. Next, 3 databases were used to predict target genes of miR-543 and a luciferase report was used to validate the direct regulation of miR-543 on the target gene. Further, a rescue experiment using co-transfection of miR-543 mimic and target mimic was performed to evaluate whether overexpressing the target gene could partly rescue the efficiency of overexpressing miR-543 on osteogenesis in hPDLSCs.

RESULTS

miR-543 was upregulated during osteogenic differentiation of hPDLSCs. Functional experiments showed that overexpressing miR-543 could enhance osteogenesis, while inhibiting miR-543 resulted in reduced formation of mineralized nodules. The transducer of ERBB2, 2 (TOB2) was identified as a target gene of miR-543 and luciferase report revealed that miR-543 interacts directly with the 3'-untranslated repeat sequence of TOB2 mRNA. Overexpression of miR-543 inhibited the expression of TOB2 in both mRNA and protein levels while inhibiting miR-543 increased. Furthermore, the rescue experiment confirmed the promotional role of miR-543 TOB2 expression could be abrogated by overexpressing TOB2, which also had the effect of reducing osteogenic differentiation.

CONCLUSION

Our research confirmed that miR-543 is a promoter of osteogenesis in hPDLSCs, acting by inhibiting its target gene TOB2, which suggests that miR-543 may be a potential therapy for bone loss in periodontitis.

miR-143 suppresses the osteogenic differentiation of dental pulp stem cells by inactivation of NF-κB signaling pathway via targeting TNF-α

BACKGROUND

Dental pulp stem cells (DPSCs) are multipotent and play an important role in repairing damaged and/or defective dentinogenesis/osteogenesis. Recent studies have documented the implication of miR-143 in osteogenic differentiation of DPSCs. Nevertheless, the detailed mechanisms of miR-143 involved in the osteogenic differentiation of DPSCs remain to be further elaborated.

METHODS

Isolated DPSCs were incubated with osteogenic differentiation medium to induce osteogenic differentiation. qRT-PCR and western blot were performed to determine the expressions of miR-143 and tumor necrosis factor α (TNF-α). Luciferase reporter assay was used to confirm whether TNF-α was a target of miR-143. Osteogenic differentiation of DPSCs was evaluated by alkaline phosphatase (ALP) activity assay, ALP staining, and western blot analyses of osteogenic-markers including bone morphogenetic protein 2 (BMP2), ALP, runt-related transcription factor 2 (RUNX2) and collagen type I (COLI).

RESULTS

miR-143 was downregulated and TNF-α was upregulated during osteogenic differentiation of DPSCs. miR-143 posttranscriptionally regulated TNF-α expression in DPSCs by binding to its 3'UTR. miR-143 overexpression suppressed osteogenic differentiation of DPSCs, as demonstrated by the decrease of ALP activity, ALP positive cell ratio, as well as BMP2, ALP, RUNX2, and COLI expressions. Moreover, miR-143 reversed TNF-α-induced osteogenic differentiation of DPSCs. Finally, the osteogenic differentiation of DPSCs induced by miR-143 inhibitor was attenuated following inactivation of nuclear factor kappa B (NF-κB) signaling pathway.

CONCLUSION

miR-143 suppressed the osteogenic differentiation of DPSCs by blockade of NF-κB signaling pathway via targeting TNF-α.

How has dental pulp stem cells isolation been conducted? A scoping review

The objective of this study was to realize a scoping review the literature in order to identify the profile of DPSCs isolation and analyze the possible risk factors that could change the native behavior of these cells. An initial search was conducted using the following MeSH terms: "(dental pulp stem cell [MeSH])"; "(dental pulp [MeSH])" AND "(stem cell [MeSH])"; "("dental pulp stem cell" [MeSH]")". The electronic search was done without date restriction up to and including April 2014, in PubMed, Scopus, Scielo and ISI Web of Knowledge databases. Studies were submitted to inclusion and exclusion criteria and 222 articles were included. Data showed that over the past 15 years many studies have been conducted using DPSCs. However this is the first systematic review regarding the isolation of stem cell, and more specifically of dental pulp stem cells. The isolation of dental pulp stem cells showed great variability, hampering the development of standard protocols to achieve in vitro dental pulp stem cells with similar characteristics. This scoping review combined, for the first time, the methodologies used for dental pulp stem isolation, highlighting the most frequently used.

Stem Cells from Dental Pulp: What Epigenetics Can Do with Your Tooth

Adult stem cells have attracted scientific attention because they are able to self-renew and differentiate into several specialized cell types. In this context, human dental tissue-derived mesenchymal stem cells (hDT-MSCs) have emerged as a possible solution for repairing or regenerating damaged tissues. These cells can be isolated from primary teeth that are naturally replaced, third molars, or other dental tissues and exhibit self-renewal, a high proliferative rate and a great multilineage potential. However, the cellular and molecular mechanisms that determine lineage specification are still largely unknown. It is known that a change in cell fate requires the deletion of existing transcriptional programs, followed by the establishment of a new developmental program to give rise to a new cell lineage. Increasing evidence indicates that chromatin structure conformation can influence cell fate. In this way, reversible chemical modifications at the DNA or histone level, and combinations thereof can activate or inactivate cell-type-specific gene sequences, giving rise to an alternative cell fates. On the other hand, miRNAs are starting to emerge as a possible player in establishing particular somatic lineages. In this review, we discuss two new and promising research fields in medicine and biology, epigenetics and stem cells, by summarizing the properties of hDT-MSCs and highlighting the recent findings on epigenetic contributions to the regulation of cellular differentiation.

MicroRNA-214 Suppresses Osteogenic Differentiation of Human Periodontal Ligament Stem Cells by Targeting ATF4

Periodontitis is the main cause of adult tooth loss. Stem cell-based tissue engineering has become a promising therapy for periodontitis treatment. To date, human periodontal ligament stem cells (hPDLSCs) have been shown to be a favorable source for tissue engineering, but modulatory mechanisms of hPDLSCs remain unclear. Approximately 60% of mammalian genes are the targets of over 2000 miRNAs in multiple human cell types, and miRNAs are able to influence various biological processes in the human body, including bone formation. In this study, we found that after osteogenic induction, miR-214 was significantly decreased in hPDLSCs; therefore, we examined the effects of miR-214 on osteogenic differentiation. Computational miRNA target prediction analyses and luciferase reporter assays revealed that activating transcription factor 4 (ATF4) is a direct target of miR-214. We prepared cells overexpressing miR-214 and found that miR-214 negatively regulates osteogenic differentiation of hPDLSCs. For the target of miR-214, ATF4 protein expression level was decreased after induction. In conclusion, we found that miR-214-ATF4 axis is a novel pathway for regulating hPDLSC osteogenic differentiation.

MicroRNA-218 inhibits proliferation and invasion in ovarian cancer by targeting Runx2

MicroRNA-218 (miR-218) has been implicated in the development and progression of multiple cancers. We investigated the role of miR-218 in ovarian cancer progression. We found that miR-218 expression levels were lower in ovarian cancer tissues and cell lines than in adjacent normal tissues or a normal ovarian cell line.miR-218 levels associated with International Federation of Gynecology and Obstetrics (FIGO) stage and lymph node metastasis. Exogenous expression of miR-218 inhibited cell proliferation, colony formation, migration, and invasion in vitro and suppressed tumor growth in a tumor-bearing nude mouse model. Runt-related transcription factor 2 (RUNX2) was identified as a direct functional target of miR-218, and its expression was inversely correlated with miR-218 expression in ovarian cancer tissues. RUNX2 overexpression rescued the suppressive effect of miR-218 on ovarian cancer cell proliferation, colony formation, migration, and invasion. These findings highlight an important role played bymiR-218 in the regulation of cancer growth and metastasis, in part by repressing RUNX2, and revealed the potential of miR-218 as a new therapeutic target inovarian cancer.

Cross-talk of MicroRNA and hydrogen sulfide: A novel therapeutic approach for bone diseases

Bone homeostasis requires a balance between the bone formation of osteoblasts and bone resorption of osteoclasts to maintain ideal bone mass and bone quality. An imbalance in bone remodeling processes results in bone metabolic disorders such as osteoporosis. Hydrogen sulfide (H₂S), a gasotransmitter, has attracted the focus of many researchers due to its multiple physiological functions. It has been implicated in anti-inflammatory, vasodilatory, angiogenic, cytoprotective, anti-oxidative and anti-apoptotic mechanisms. H₂S has also been shown to exert osteoprotective activity through its anti-inflammatory and anti-oxidative effects. However, the underlying molecular mechanisms by which H₂S mitigates bone diseases are not completely understood. Experimental evidence suggests that H₂S may regulate signaling pathways by directly influencing a gene in the cascade or interacting with some other gasotransmitter (carbon monoxide or nitric oxide) or both. MicroRNAs (miRNAs) are short non-coding RNAs which regulate gene expression by targeting, binding and suppressing mRNAs; thus controlling cell fate. Certainly, bone remodeling is also regulated by miRNAs expression and has been reported in many studies. MicroRNAs also regulate H₂S biosynthesis. The inter-regulation of microRNAs and H₂S opens a new possibility for exploring the H₂S-microRNA crosstalk in bone diseases. However, the relationship between miRNAs, bone development, and H₂S is still not well explained. This review focuses on miRNAs and their roles in regulating bone remodeling and possible mechanisms behind H₂S mediated bone loss inhibition, H₂S-miRNAs crosstalk in relation to the pathophysiology of bone remodeling, and future perspectives for miRNA-H₂S as a therapeutic agent for bone diseases.

Identification of MicroRNAs by Microarray Analysis and Prediction of Target Genes Involved in Osteogenic Differentiation of Human Periodontal Ligament Stem Cells

BACKGROUND

The roles of microRNAs (miRNAs) in osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) remain largely unexplored. In this study, the underlying molecular mechanism of osteogenic differentiation in hPDLSCs is investigated using miRNA profiling.

METHODS

The miRNA expression profile during osteogenic differentiation was analyzed using a microarray. Target genes of miRNAs with at least two-fold change in expression (P <0.05) were predicted by bioinformatics. Six miRNAs with osteogenesis-related target genes were validated by quantitative reverse transcription-polymerase chain reaction (qRT-PCR).

RESULTS

Expression of 116 miRNAs was found to be altered after osteoinduction, with 30 upregulated and 86 downregulated. Thirty-one of these miRNAs (26.7%) had osteogenesis-related target genes. Changes in expression levels of six of the 31 miRNAs (miR-654-3p, miR-4288, miR-34c-5p, miR-218-5p, miR-663a, and miR-874-3p) were validated by qRT-PCR.

CONCLUSIONS

Significant alterations in miRNA expression profiles were observed during osteogenic differentiation of hPDLSCs. These results imply that miRNAs may have regulatory effects on this process by targeting osteogenesis-related genes.

MicroRNA-22 Promoted Osteogenic Differentiation of Human Periodontal Ligament Stem Cells by Targeting HDAC6

Stem cells transplantation is a promising therapy strategy for accelerating periodontal regeneration and reconstruction. Genetic modification could induce stem cells directional differentiation to facilitate recovery of physiological functions. In this study, we investigated the role and mechanism of miR-22 on human periodontal ligament stem cells (PDLSCs). First, a cellular model of osteogenic differentiation was first established by osteogenic inductive cocktail. Real-time PCR determined that expression of miR-22 was significantly increased during PDLSCs osteogenic differentiation. Alizirin red staining showed that overexpression of miR-22 in PDLSCs induced better mineralized nodule formation. Real-time PCR and Western blot further confirmed up-regulation of osteogenic genes Runx2 and OPN in miR-22-overexpressing PDLSCs. Conversely, inhibition of miR-22 delayed the process of PDLSCs osteogenic differentiation. Furthermore, Histone deacetylase 6 (HDAC6) was identified as a target gene of miR-22. Overexpression of miR-22 not only reduced the luciferase activity of the reporter containing the 3' untranslated region of HDAC6 mRNA, but also suppressed the endogenous protein expression of HDAC6. Rescue experiment showed that the promotion role of miR-22 in osteogenic differentiation could be relieved by overexpression of HDAC6. Meanwhile, overexpression of HDAC6 alone could also delay the osteogenic differentiation process. The results demonstrated that miR-22 promoted PDLSCs osteogenic differentiation by inhibiting HDAC6 expression, suggesting that miR-22 might be developed as a target of genetic modified stem cells therapy for periodontal diseases. J. Cell. Biochem. 118: 1653-1658, 2017. © 2017 Wiley Periodicals, Inc.

MicroRNAs and Periodontal Homeostasis

MicroRNAs (miRNAs) are a group of small RNAs that control gene expression in all aspects of eukaryotic life, primarily through RNA silencing mechanisms. The purpose of the present review is to introduce key miRNAs involved in periodontal homeostasis, summarize the mechanisms by which they affect downstream genes and tissues, and provide an introduction into the therapeutic potential of periodontal miRNAs. In general, miRNAs function synergistically to fine-tune the regulation of biological processes and to remove expression noise rather than by causing drastic changes in expression levels. In the periodontium, miRNAs play key roles in development and periodontal homeostasis and during the loss of periodontal tissue integrity as a result of periodontal disease. As part of the anabolic phase of periodontal homeostasis and periodontal development, miRNAs direct periodontal fibroblasts toward alveolar bone lineage differentiation and new bone formation through WNT, bone morphogenetic protein, and Notch signaling pathways. miRNAs contribute equally to the catabolic aspect of periodontal homeostasis as they affect osteoclastogenesis and osteoclast function, either by directly promoting osteoclast activity or by inhibiting osteoclast signaling intermediaries or through negative feedback loops. Their small size and ability to target multiple regulatory networks of related sets of genes have predisposed miRNAs to become ideal candidates for drug delivery and tissue regeneration. To address the immense therapeutic potential of miRNAs and their antagomirs, an ever growing number of delivery approaches toward clinical applications have been developed, including nanoparticle carriers and secondary structure interference inhibitor systems. However, only a fraction of the miRNAs involved in periodontal health and disease are known today. It is anticipated that continued research will lead to a more comprehensive understanding of the periodontal miRNA world, and a systematic effort toward harnessing the enormous therapeutic potential of these small molecules will greatly benefit the future of periodontal patient care.