5-Aza-2'-deoxycytidine treatment induces skeletal myogenic differentiation of mouse dental pulp stem cells

5-Azacytidine incorporated skeletal muscle-derived hydrogel promotes rat skeletal muscle regeneration

Decellularized skeletal muscle is a promising biomaterial for muscle regeneration due to the mimicking of the natural microenvironment. Previously, it has been reported that 5-Azacytidine (5-Aza), a DNA methyltransferase inhibitor, induces myogenesis in different types of stem cells. In the current study, we investigated the effect of 5-Aza incorporated muscle-derived hydrogel on the viability and proliferation of muscle-derived stem cells (MDSCs) in vitro and muscle regeneration in vivo. Wistar rat skeletal muscles were decellularized using a physico-chemical protocol. The decellularized tissue was analyzed using SEM, histological staining and evaluation of DNA content. Then, muscle-derived hydrogel was made from Pepsin-digested decellularized muscle tissues. 5-Aza was physically adsorbed in prepared hydrogels. Then, MDSCs were cultured on hydrogels with/without 5-Aza, and their proliferation and cell viability were determined using LIVE/DEAD and DAPI staining. Moreover, myectomy lesions were done in rat femoris muscles, muscle-derived hydroges with/without 5-Aza were injected to the myectomy sites, and histological evaluation was performed after three weeks. The analysis of decellularized muscle tissues showed that they maintained extracellular matrix components of native muscles, while they lacked DNA. LIVE/DEAD and DAPI staining showed that the hydrogel containing 5-Aza supported MDSCs viability. Histological analysis of myectomy sites showed an improvement in muscle regeneration after administration of 5-Aza incorporated hydrogel. These findings suggest that the combination of 5-Aza with skeletal muscle hydrogel may serve as an alternative treatment option to improve the regeneration of injured muscle tissue.

Advances in Molecular Pathology of Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a common syndrome that features a complex etiology and set of mechanisms. Here we summarized the molecular pathogenesis of OSA, especially the prospective mechanism of upper? airway dilator fatigue and the current breakthroughs. Additionally, we also introduced the molecular mechanism of OSA in terms of related studies on the main signaling pathways and epigenetics alterations, such as microRNA, long non-coding RNA, and DNA methylation. We also reviewed small molecular compounds, which are potential targets for gene regulations in the future, that are involved in the regulation of OSA. This review will be beneficial to point the way for OSA research within the next decade.

Epigenetic Regulation of Methylation in Determining the Fate of Dental Mesenchymal Stem Cells

Dental mesenchymal stem cells (DMSCs) are crucial in tooth development and periodontal health, and their multipotential differentiation and self-renewal ability play a critical role in tissue engineering and regenerative medicine. Methylation modifications could promote the appropriate biological behavior by postsynthetic modification of DNA or protein and make the organism adapt to developmental and environmental prompts by regulating gene expression without changing the DNA sequence. Methylation modifications involved in DMSC fate include DNA methylation, RNA methylation, and histone modifications, which have been proven to exert a significant effect on the regulation of the fate of DMSCs, such as proliferation, self-renewal, and differentiation potential. Understanding the regulation of methylation modifications on the behavior and the immunoinflammatory responses involved in DMSCs contributes to further study of the mechanism of methylation on tissue regeneration and inflammation. In this review, we briefly summarize the key functions of histone methylation, RNA methylation, and DNA methylation in the differentiation potential and self-renewal of DMSCs as well as the opportunities and challenges for their application in tissue regeneration and disease therapy.

DNA Methylation and Histone Modification in Dental-derived Mesenchymal Stem Cells

Epigenetic regulation, mainly involving DNA methylation, histone modification, and noncoding RNAs (ncRNAs), is essential for the regulation of multiple cellular processes. Dental-derived mesenchymal stem cells (DMSCs), a kind of multipotent cells derived from dental tissues, are impactful in regenerative medicine. Recent studies have shown that epigenetic regulation plays a major role in DMSCs. Therefore, exploring how epigenetic regulation is involved in DMSCs may be of guiding significance for tissue repair and regeneration or for exploring more effective treatments. A number of research of ncRNAs in DMSCs have been reported. However, little is known about the roles of DNA methylation and histone modifications in DMSCs. In this review, we summarize the important roles of DNA methylation and histone modifications of the fate of DMSCs.

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).

Dental-derived cells for regenerative medicine: stem cells, cell reprogramming, and transdifferentiation

Embryonic stem cells have been a popular research topic in regenerative medicine owing to their pluripotency and applicability. However, due to the difficulty in harvesting them and their low yield efficiency, advanced cell reprogramming technology has been introduced as an alternative. Dental stem cells have entered the spotlight due to their regenerative potential and their ability to be obtained from biological waste generated after dental treatment. Cell reprogramming, a process of reverting mature somatic cells into stem cells, and transdifferentiation, a direct conversion between different cell types without induction of a pluripotent state, have helped overcome the shortcomings of stem cells and raised interest in their regenerative potential. Furthermore, the potential of these cells to return to their original cell types due to their epigenetic memory has reinforced the need to control the epigenetic background for successful management of cellular differentiation. Herein, we discuss all available sources of dental stem cells, the procedures used to obtain these cells, and their ability to differentiate into the desired cells. We also introduce the concepts of cell reprogramming and transdifferentiation in terms of genetics and epigenetics, including DNA methylation, histone modification, and non-coding RNA. Finally, we discuss a novel therapeutic avenue for using dental-derived cells as stem cells, and explain cell reprogramming and transdifferentiation, which are used in regenerative medicine and tissue engineering.

Epigenetic regulation of dental pulp stem cells and its potential in regenerative endodontics

Regenerative endodontics (RE) therapy means physiologically replacing damaged pulp tissue and regaining functional dentin–pulp complex. Current clinical RE procedures recruit endogenous stem cells from the apical papilla, periodontal tissue, bone marrow and peripheral blood, with or without application of scaffolds and growth factors in the root canal space, resulting in cementum-like and bone-like tissue formation. Without the involvement of dental pulp stem cells (DPSCs), it is unlikely that functional pulp regeneration can be achieved, even though acceptable repair can be acquired. DPSCs, due to their specific odontogenic potential, high proliferation, neurovascular property, and easy accessibility, are considered as the most eligible cell source for dentin–pulp regeneration. The regenerative potential of DPSCs has been demonstrated by recent clinical progress. DPSC transplantation following pulpectomy has successfully reconstructed neurovascularized pulp that simulates the physiological structure of natural pulp. The self-renewal, proliferation, and odontogenic differentiation of DPSCs are under the control of a cascade of transcription factors. Over recent decades, epigenetic modulations implicating histone modifications, DNA methylation, and noncoding (nc)RNAs have manifested as a new layer of gene regulation. These modulations exhibit a profound effect on the cellular activities of DPSCs. In this review, we offer an overview about epigenetic regulation of the fate of DPSCs; in particular, on the proliferation, odontogenic differentiation, angiogenesis, and neurogenesis. We emphasize recent discoveries of epigenetic molecules that can alter DPSC status and promote pulp regeneration through manipulation over epigenetic profiles.

Key Markers and Epigenetic Modifications of Dental-Derived Mesenchymal Stromal Cells

As a novel research hotspot in tissue regeneration, dental-derived mesenchymal stromal cells (MSCs) are famous for their accessibility, multipotent differentiation ability, and high proliferation. However, cellular heterogeneity is a major obstacle to the clinical application of dental-derived MSCs. Here, we reviewed the heterogeneity of dental-derived MSCs firstly and then discussed the key markers and epigenetic modifications related to the proliferation, differentiation, immunomodulation, and aging of dental-derived MSCs. These messages help to control the composition and function of dental-derived MSCs and thus accelerate the translation of cell therapy into clinical practice.

Melatonin-induced suppression of DNA methylation promotes odontogenic differentiation in human dental pulp cells

Differentiation potency of human dental pulp cells (hDPCs) is essential for dentin regeneration. DNA methylation is one of the major epigenetic mechanisms and is suggested to involve in differentiation of hDPCs, the machinery of which includes DNA methyltransferase enzymes (DNMTs) and methyl-CpG-binding domain proteins (MBDs). Our previous study has found that melatonin (MT) promoted hDPC differentiation, but its mechanism remains elusive. We aimed to investigate the role of DNA methylation in the promotion of MT to differentiation of hDPCs in vitro. hDPCs were cultured in basal growth medium (CO) or odontogenic medium (OM) exposed to MT at different concentrations (0, 10-12, 10-10, 10-8, 10-6, 10-4 M). The cell growth was analyzed using Cell Counting Kit-8 assay, and mineralized tissue formation was measured using Alizarin red staining. The expression of the 10 genes (DNMT1, DNMT3A, DNMT3B, MBD1-6, MeCP2) was determined using real-time qPCR and western blotting. The abundance of MeCP2 in the nuclei was evaluated using immunofluorescence analysis. Global methylation level was tested using ELISA. We found that mineralized tissue formation significantly increased in OM with MT at 10-4 M, while the levels of MeCP2 and global DNA methylation level declined. The expression of MBD1, MBD3, and MBD4 significantly increased in OM alone, and the expession of DNMT1 and MBD2 was decreased. These results indicate that MT promotes odontogenic differentiation of hDPCs in vitro by regulating the levels of DNMT1, MeCP2, and global DNA methylation, suggesting that MT-induced DNA methylation machinery may play an important role in tooth regeneration.

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.

DNA methylation and demethylation link the properties of mesenchymal stem cells: Regeneration and immunomodulation

Mesenchymal stem cells (MSCs) are a heterogeneous population that can be isolated from various tissues, including bone marrow, adipose tissue, umbilical cord blood, and craniofacial tissue. MSCs have attracted increasingly more attention over the years due to their regenerative capacity and function in immunomodulation. The foundation of tissue regeneration is the potential of cells to differentiate into multiple cell lineages and give rise to multiple tissue types. In addition,the immunoregulatory function of MSCs has provided insights into therapeutic treatments for immune-mediated diseases. DNA methylation and demethylation are important epigenetic mechanisms that have been shown to modulate embryonic stem cell maintenance, proliferation, differentiation and apoptosis by activating or suppressing a number of genes. In most studies, DNA hypermethylation is associated with gene suppression, while hypomethylation or demethylation is associated with gene activation. The dynamic balance of DNA methylation and demethylation is required for normal mammalian development and inhibits the onset of abnormal phenotypes. However, the exact role of DNA methylation and demethylation in MSC-based tissue regeneration and immunomodulation requires further investigation. In this review, we discuss how DNA methylation and demethylation function in multi-lineage cell differentiation and immunomodulation of MSCs based on previously published work. Furthermore, we discuss the implications of the role of DNA methylation and demethylation in MSCs for the treatment of metabolic or immune-related diseases.

The secretome of human dental pulp stem cells protects myoblasts from hypoxia‑induced injury via the Wnt/β‑catenin pathway

Human dental pulp stem cells (hDPSCs) present several advantages, including their ability to be non-invasively harvested without ethical concern. The secretome of hDPSCs can promote the functional recovery of various tissue injuries. However, the protective effects on hypoxia-induced skeletal muscle injury remain to be explored. The present study demonstrated that C2C12 myoblast coculture with hDPSCs attenuated CoCl₂-induced hypoxic injury compared with C2C12 alone. The hDPSC secretome increased cell viability and differentiation and decreased G2/M cell cycle arrest under hypoxic conditions. These results were further verified using hDPSC-conditioned medium (hDPSC-CM). The present data revealed that the protective effects of hDPSC-CM depend on the concentration ratio of the CM. In terms of the underlying molecular mechanism, hDPSC-CM activated the Wnt/β-catenin pathway, which increased the protein levels of Wnt1, phosphorylated-glycogen synthase kinase-3β and β-catenin and the mRNA levels of Wnt target genes. By contrast, an inhibitor (XAV939) of Wnt/β-catenin diminished the protective effects of hDPSC-CM. Taken together, the findings of the present study demonstrated that the hDPSC secretome alleviated the hypoxia-induced myoblast injury potentially through regulating the Wnt/β-catenin pathway. These findings may provide new insight into a therapeutic alternative using the hDPSC secretome in skeletal muscle hypoxia-related diseases.

The role of epigenetic modifications in the osteogenic differentiation of adipose-derived stem cells

Over the last decade, stem cells have drawn extensive attention from scientists due to their full potential in tissue engineering, gene therapy, and cell therapy. Adipose-derived stem cells (ADSCs), which represent one type of mesenchymal stem cell (MSC), hold great promise in bone tissue engineering due to their painless collection procedure, their ability to self-renew and their multi-lineage differentiation properties. Major epigenetic mechanisms, which involve DNA methylation, histone modifications and RNA interference (RNAi), are known to represent one of the determining factors of ADSC fate and differentiation. Understanding the epigenetic modifications of ADSCs may provide a clue for improving stem cell therapy in bone repair and regeneration. The aim of this review is to present the recent advances in understanding the epigenetic mechanisms that facilitate ADSC differentiation into an osteogenic lineage, in addition to the characteristics of the main epigenetic modifications.

Local myogenic pulp-derived cell injection enhances craniofacial muscle regeneration in vivo

OBJECTIVES

To enhance myogenic differentiation in pulp cells isolated from extracted premolars by epigenetic modification using a DNA demethylation agent, 5-aza-2'-deoxycytidine (5-Aza), and to evaluate the potent stimulatory effect of 5-Aza-treated pulp cell injection for craniofacial muscle regeneration in vivo.

SETTING AND SAMPLE POPULATION

Pulp cells were isolated from premolars extracted for orthodontic purposes from four adults (age range, 18-22.1 years).

MATERIAL AND METHODS

Levels of myogenic differentiation and functional contraction response in vitro were compared between pulp cells with or without pre-treatment of 5-Aza. Changes in muscle regeneration in response to green fluorescent protein (GFP)-labelled myogenic pulp cell injection in vivo were evaluated using a cardiotoxin (CTX)-induced muscle injury model of the gastrocnemius as well as the masseter muscle in mice.

RESULTS

Pre-treatment of 5-Aza in pulp cells stimulated myotube formation, myogenic differentiation in terms of desmin and myogenin expression, and the level of collagen gel contraction. The local injection of 5-Aza pre-treated myogenic pulp cells was engrafted into the host tissue and indicated signs of enhanced muscle regeneration in both the gastrocnemius and the masseter muscles.

CONCLUSION

The epigenetic modification of pulp cells from extracted premolars and the local injection of myogenic pulp cells may stimulate craniofacial muscles regeneration in vivo.

MEF2 Transcription Factor Regulates Osteogenic Differentiation of Dental Pulp Stem Cells

The myocyte enhancer factor-2 (MEF2) is a member of the MADS-box family. It controls the expression of genes that are critical for biological processes such as proliferation, cell death, and differentiation. Some studies have shown that MEF2 expression is enhanced in osteogenic progenitor cells established from bone marrow stromal cells with other types of mesenchymal progenitor cells. However, the effect of MEF2 on dental pulp stem cells (DPSCs) is unclear. In this study, we investigate the effect of MEF2 on regulating osteogenic differentiation and proliferation of DPSCs. We find that MEF2 is stably expressed in DPSCs, and the expression is increased time-dependently along with cell osteogenic differentiation. MEF2 expression also increases the alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2) activity, and enhances mineralization in DPSCs. SB202190, inhibitor of p38, blocks the p38/MEF2 pathway and osteogenic differentiation. In addition, MEF2 overexpression inhibits DPSC proliferation. In summary, our data indicate that MEF2 not only regulates DPSCs as an inhibitor of cell proliferation but is also a promoter of osteogenic differentiation through the p38/MEF2 signaling pathway.

Genetic background and embryonic temperature affect DNA methylation and expression of myogenin and muscle development in Atlantic salmon (Salmo salar)

The development of ectothermic embryos is strongly affected by incubation temperature, and thermal imprinting of body growth and muscle phenotype has been reported in various teleost fishes. The complex epigenetic regulation of muscle development in vertebrates involves DNA methylation of the myogenin promoter. Body growth is a heritable and highly variable trait among fish populations that allows for local adaptations, but also for selective breeding. Here we studied the epigenetic effects of embryonic temperature and genetic background on body growth, muscle cellularity and myogenin expression in farmed Atlantic salmon (Salmo salar). Eggs from salmon families with either high or low estimated breeding values for body growth, referred to as Fast and Slow genotypes, were incubated at 8°C or 4°C until the embryonic 'eyed-stage' followed by rearing at the production temperature of 8°C. Rearing temperature strongly affected the growth rates, and the 8°C fish were about twice as heavy as the 4°C fish in the order Fast8>Slow8>Fast4>Slow4 prior to seawater transfer. Fast8 was the largest fish also at harvest despite strong growth compensation in the low temperature groups. Larval myogenin expression was approximately 4-6 fold higher in the Fast8 group than in the other groups and was associated with relative low DNA methylation levels, but was positively correlated with the expression levels of the DNA methyltransferase genes dnmt1, dnmt3a and dnmt3b. Juvenile Fast8 fish displayed thicker white muscle fibres than Fast4 fish, while Slow 8 and Slow 4 showed no difference in muscle cellularity. The impact of genetic background on the thermal imprinting of body growth and muscle development in Atlantic salmon suggests that epigenetic variation might play a significant role in the local adaptation to fluctuating temperatures over short evolutionary time.

Enhanced differentiation of mesenchymal stromal cells by three-dimensional culture and azacitidine

BACKGROUND

Mesenchymal stromal cells (MSCs) are useful for cell therapy because of their potential for multilineage differentiation. However, MSCs that are expanded in traditional two-dimensional (2D) culture systems eventually lose their differentiation abilities. Therefore, we investigated whether azacitidine (AZA) supplementation and three-dimensional culture (3D) could improve the differentiation properties of MSCs.

METHODS

2D- or 3D-cultured MSCs which were prepared according to the conventional or hanging-drop culture method respectively, were treated with or without AZA (1 µM for 72 h), and their osteogenic and adipogenic differentiation potential were determined and compared.

RESULTS

AZA treatment did not affect the cell apoptosis or viability in both 2D- and 3D-cultured MSCs. However, compared to conventionally cultured 2D-MSCs, AZA-treated 2D-MSCs showed marginally increased differentiation abilities. In contrast, 3D-MSCs showed significantly increased osteogenic and adipogenic differentiation ability. When 3D culture was performed in the presence of AZA, the osteogenic differentiation ability was further increased, whereas adipogenic differentiation was not affected.

CONCLUSION

3D culture efficiently promoted the multilineage differentiation of MSCs, and in combination with AZA, it could help MSCs to acquire greater osteogenic differentiation ability. This optimized culture method can enhance the therapeutic potential of MSCs.

Role of MSX1 in Osteogenic Differentiation of Human Dental Pulp Stem Cells

Msh homeobox 1 (MSX1) encodes a transcription factor implicated in embryonic development of limbs and craniofacial tissues including bone and teeth. Although MSX1 regulates osteoblast differentiation in the cranial bone of young animal, little is known about the contribution of MSX1 to the osteogenic potential of human cells. In the present study, we investigate the role of MSX1 in osteogenic differentiation of human dental pulp stem cells isolated from deciduous teeth. When these cells were exposed to osteogenesis-induction medium, runt-related transcription factor-2 (RUNX2), bone morphogenetic protein-2 (BMP2), alkaline phosphatase (ALPL), and osteocalcin (OCN) mRNA levels, as well as alkaline phosphatase activity, increased on days 4–12, and thereafter the matrix was calcified on day 14. However, knockdown of MSX1 with small interfering RNA abolished the induction of the osteoblast-related gene expression, alkaline phosphatase activity, and calcification. Interestingly, DNA microarray and PCR analyses revealed that MSX1 knockdown induced the sterol regulatory element-binding protein 2 (SREBP2) transcriptional factor and its downstream target genes in the cholesterol synthesis pathway. Inhibition of cholesterol synthesis enhances osteoblast differentiation of various mesenchymal cells. Thus, MSX1 may downregulate the cholesterol synthesis-related genes to ensure osteoblast differentiation of human dental pulp stem cells.

The role of oncostatin M regulates osteoblastic differentiation of dental pulp stem cells through STAT3 pathway

Dental pulp stem cells (DPSCs) are a type of mesenchymal stem cells, which have the self-renewal and multi-lineage differentiation potential, including chondrocytes, adipocytes, neural cells and osteoblasts. So they play a significant role in pulp repair and bone regeneration. Oncostatin M (OSM), one of the IL-6 family cytokines, inhibits adipogenic differentiation and stimulates osteogenic differentiation of human bone marrow mesenchymal stem cells. However, the effect of OSM on DPSCs is unclear. We found that OSM induced osteogenic differentiation of DPSCs, promoting matrix mineralization as measured by Alizarin Red S staining. OSM also increased expression of osteogenesis-associated gene products Alkaline phosphatase, Bone morphogenetic protein 2 (BMP2), Runt-related transcription factor 2 and Osteocalcin (OCN) as assessed by immunoblotting. We also found that OSM activated the Signal Transducer And Activator Of Transcription 3 (STAT3) pathway during the osteogenic differentiation of DPSCs. Blocking the osteogenic differentiation by silencing of STAT3 can significantly inhibit OSM-induced osteogenic differentiation of DPSCs and the expression of related genes, furthermore matrix mineralization was also suppressed. In summary, OSM promotes osteoblastic differentiation of DPSCs and osteogenesis-related genes expression through the JAK3/STAT3 signaling pathway which may be useful for the autologous transplantation of DPSCs.

Oral mucosal progenitor cell clones resist in vitro myogenic differentiation

Progenitor cells derived from the oral mucosa lamina propria (OMLP-PCs) demonstrate an ability to differentiate into tissue lineages removed from their anatomical origin. This clonally derived population of neural-crest cells have demonstrated potential to differentiate along mesenchymal and neuronal cell lineages.

OBJECTIVE

Significant efforts are being made to generate functioning muscle constructs for use in research and clinical tissue engineering. In this study we aimed to determine the myogenic properties of clonal populations of expanded OMLP-PCs.

DESIGN

PCs were subject to several in vitro culture conditions in an attempt to drive myogenic conversion. Methodologies include use of demethylation gene-modifying reagents, mechanical conditioning of tissue culture substrates, tuneable polyacrylamide gels and a 3-dimensional construct as well as published myogenic media compositions. PCR and immunostaining for the muscle cell markers Desmin and MyoD1 were used to assess muscle differentiation.

RESULTS

The clones tested did not intrinsically express myogenic lineage markers. Despite use of two and 3-dimensional pre-published in vitro culture protocols OMLP clones could not be differentiated down a myogenic lineage.

CONCLUSIONS

Within the confines of these experimental parameters it was not possible to generate identifiable muscle using the clonal populations. When reviewing the previously successful reports of myogenic conversion, cells utilised have either been derived from tissues that are already 'primed' with the requisite myogenic genetic potential or have undergone specific genetic reprogramming to enhance the myogenic conversion rate. This, along with as yet unidentified stromal interplay, may therefore be required for positive myogenic differentiation to be realised.

Clonal Heterogeneity in the Neuronal and Glial Differentiation of Dental Pulp Stem/Progenitor Cells

Cellular heterogeneity presents an important challenge to the development of cell-based therapies where there is a fundamental requirement for predictable and reproducible outcomes. Transplanted Dental Pulp Stem/Progenitor Cells (DPSCs) have demonstrated early promise in experimental models of spinal cord injury and stroke, despite limited evidence of neuronal and glial-like differentiation after transplantation. Here, we report, for the first time, on the ability of single cell-derived clonal cultures of murine DPSCs to differentiate in vitro into immature neuronal-like and oligodendrocyte-like cells. Importantly, only DPSC clones with high nestin mRNA expression levels were found to successfully differentiate into Map2 and NF-positive neuronal-like cells. Neuronally differentiated DPSCs possessed a membrane capacitance comparable with primary cultured striatal neurons and small inward voltage-activated K(+) but not outward Na(+) currents were recorded suggesting a functionally immature phenotype. Similarly, only high nestin-expressing clones demonstrated the ability to adopt Olig1, Olig2, and MBP-positive immature oligodendrocyte-like phenotype. Together, these results demonstrate that appropriate markers may be used to provide an early indication of the suitability of a cell population for purposes where differentiation into a specific lineage may be beneficial and highlight that further understanding of heterogeneity within mixed cellular populations is required.

Regenerative Applications Using Tooth Derived Stem Cells in Other Than Tooth Regeneration: A Literature Review

Tooth derived stem cells or dental stem cells are categorized according to the location from which they are isolated and represent a promising source of cells for regenerative medicine. Originally, as one kind of mesenchymal stem cells, they are considered an alternative of bone marrow stromal cells. They share many commonalties but maintain differences. Considering their original function in development and the homeostasis of tooth structures, many applications of these cells in dentistry have aimed at tooth structure regeneration; however, the application in other than tooth structures has been attempted extensively. The availability from discarded or removed teeth can be an innate benefit as a source of autologous cells. Their origin from the neural crest results in exploitation of neurological and numerous other applications. This review briefly highlights current and future perspectives of the regenerative applications of tooth derived stem cells in areas beyond tooth regeneration.

MiR-143 and miR-135 inhibitors treatment induces skeletal myogenic differentiation of human adult dental pulp stem cells

OBJECTIVE

Dental pulp stem cells (DPSCs) possess pluripotent properties that allow them to differentiate into multiple cell lineages, which can be potentially used in tissue regeneration. The aim of this in vitro study is to explore the effect of miRNAs on the myogenic differentiation of human adult DPSCs and seek for some potential biological factors for stable and feasible application in DPSC myogenic differentiation.

METHODS

Human adult DPSCs were isolated from normal impacted third molars were treated with 5-Aza-2'-deoxycytidine to induce to myogenic differentiation in vitro. During this process the levels of myomiRNAs and myogenic marker genes were detected by real-time qPCR and Western blotting. Then antisense oligonucleotides of miR-143 and miR-135 were transfected into DPSCs to explore their effects on myogenic differentiation. Gene expression detection and MyHC immunofluorescence microscopy analysis were applied to characterize the myogenic differentiation of DPSCs.

RESULTS

Expression of miR-135 and miR-143 was markedly decreased in myoblast DPSCs induced by 5-Aza. Part of the DPSCs treated with miR-135 or miR-143 inhibitors showed apparent myocytic properties and eventually fused to form myotubes. Co-transfection of miR-135 and miR-143 inhibitors impelled half of DPSCs to form myotubes.

CONCLUSION

MiR-135 and miR-143 inhibitors could induce myogenic differentiation of DPSCs. Our findings indicated that miRNAs could exert a decisive function in induction of myogenic differentiation of DPSCs.

Enhancement of human mesenchymal stem cell differentiation by combination treatment with 5-azacytidine and trichostatin A

OBJECTIVE

To enhance the differentiation of mesenchymal stem cells (MSCs) and their epigenetic status by modification using hypomethylating agents (HMAs) and histone deacetylase inhibitors (HDACs).

RESULTS

Treatment with 5-azacytidine or 5-azacytidine plus trichostatin A (TSA) increased expression of Runx-2, BDNF and Sox-9 compared with the control or TSA groups. Maximal increases of 4.1-, 4.5-, and 8.3-fold in Runx-2, BDNF, and Sox-9 transcript levels, respectively, were observed in the 5-azacytidine plus TSA group. Similar to the expression pattern of key regulatory molecules, differentiation to each lineage was also enhanced considerably in the 5-azacytidine or in the 5-azacytidine plus TSA groups. Quantitative analyses at the protein level showed 8.9-, 26.8-, 27.9-, and 28.5-fold upregulation of osterix, MAP-2, nestin, and type II collagen), respectively.

CONCLUSION

HMAs and HDACs enhanced in vitro differentiation of MSCs, which was maximized when the two drugs were combined, with HMA having the dominant effect.

Mouse Dental Pulp Stem Cells Support Human Umbilical Cord Blood-Derived Hematopoietic Stem/Progenitor Cells in Vitro

It is well documented that specialized mesenchymal stem/stromal cells (MSCs) constitute the hematopoietic stem cell (HSC) niche in the bone marrow (BM), and these MSCs support/maintain the HSCs in an undifferentiated state. A number of studies have demonstrated that BM-derived MSCs (BM-MSCs) can support HSCs in vitro. However, it remains unclear whether nonhematopoietic tissue-derived MSC-like cells, such as dental pulp stem cells (DPSCs), have the ability to support HSCs. In this study, we prospectively isolated DPSCs from mouse mandibular incisors by fluorescence-activated cell sorting (FACS) using BM-MSC markers, such as PDGFRα and Sca-1. The PDGFRα and Sca-1 double-positive DPSCs and BM-MSCs showed similar morphologies and expression patterns of MSC markers. The ability of the DPSCs to support hematopoietic stem/progenitor cells (HSPCs) was then analyzed by an in vitro coculture system. Moreover, their HSC-supporting activity was evaluated by in vivo xenotransplantation assays using NOD/Shi-scid/IL-2Rγcnull (NOG) mice. Interestingly, the DPSCs supported human cord blood (CB)-derived CD34-positive (CD34+), as well as CD34-negative (CD34–), HSCs. The supporting activities of DPSCs for human CB-derived CD34+ and CD34– HSCs were comparable to those of BM-MSCs. The results of the present study demonstrated, for the first time, that prospectively isolated murine PDGFRα and Sca-1 double-positive DPSCs could support primitive human CD34+ and CD34– HSCs in vitro.

Concurrent expression of Oct4 and Nanog maintains mesenchymal stem-like property of human dental pulp cells

Human dental pulp stem cells (DPSCs), unique mesenchymal stem cells (MSCs) type, exhibit the characteristics of self-renewal and multi-lineage differentiation capacity. Oct4 and Nanog are pluripotent genes. The aim of this study was to determine the physiological functions of Oct4 and Nanog expression in DPSCs. Herein, we determined the critical role of an Oct4/Nanog axis modulating MSCs properties of DPSCs by lentiviral-mediated co-overexpression or co-knockdown of Oct4/Nanog in DPSCs. MSCs properties including osteogenic/chondrogenic/adipogenic induction differentiation was assayed for expression of osteogenic/chondrogenic/adipogenic markers by quantitative real-time RT-PCR analysis. Initially, we observed that the expression profile of Oct4 and Nanog in dental pulp cells, which exerted properties of MSCs, was significantly up-regulated compared to that of STRO-1⁻CD146⁻ dental pulp cells. Down-regulation of Oct4 and Nanog co-expression significantly reduced the cell proliferation, osteogenic differentiation capability, STRO-1, CD146, and Alkaline phosphatase (ALP) activity of DPSCs. In contrast, co-overexpression of Oct4 and Nanog enhanced the expression level of STRO-1 and CD146, proliferation rate and osteogenic/chondrogenic/adipogenic induction differentiation capability, and expression of osteogenic/chondrogenic/adipogenic induction differentiation markers. Our results suggest that Oct4-Nanog signaling is a regulatory switch to maintain properties in DPSCs.

Transdifferentiation of human periodontal ligament stem cells into pancreatic cell lineage

Human periodontal ligament-derived stem cells (PDLSCs) demonstrate self-renewal capacity and multilineage differentiation potential. In this study, we investigated the transdifferentiation potential of human PDLSCs into pancreatic islet cells. To form three-dimensional (3D) clusters, PDLSCs were cultured in Matrigel with media containing differentiation-inducing agents. We found that after 6 days in culture, PDLSCs underwent morphological changes resembling pancreatic islet-like cell clusters (ICCs). The morphological characteristics of PDLSC-derived ICCs were further assessed using scanning electron microscopy analysis. Using reverse transcription-polymerase chain reaction analysis, we found that pluripotency genes were downregulated, whereas early endoderm and pancreatic differentiation genes were upregulated, in PDLSC-derived ICCs compared with undifferentiated PDLSCs. Furthermore, we found that PDLSC-derived ICCs were capable of secreting insulin in response to high concentrations of glucose, validating their functional differentiation into islet cells. Finally, we also performed dithizone staining, as well as immunofluorescence assays and fluorescence-activated cell sorting analysis for pancreatic differentiation markers, to confirm the differentiation status of PDLSC-derived ICCs. These results demonstrate that PDLSCs can transdifferentiate into functional pancreatic islet-like cells and provide a novel, alternative cell population for pancreatic repair.

Expression features of DNA methylcytosine dioxygenase ten-eleven translocation 1 in human dental pulp cells

INTRODUCTION

Human dental pulp cells (hDPCs) can specifically generate reparative dentin under external stimuli, and numerous mechanisms are involved in their odontogenic differentiation process. Ten-eleven translocation 1 (TET1) is a recently discovered DNA dioxygenase that plays important roles in promoting DNA demethylation and transcriptional regulation. Although several studies regarding its effect on cell differentiation and proliferation have been conducted, the expression and function of TET1 have not yet been characterized in hDPCs. The purpose of this study was to explore the expression features of TET1 in hDPCs.

METHODS

Cellular TET1 localization in hDPCs was determined by immunofluorescence. The expression pattern of TET1 and its potential changes during odontogenic induction were confirmed using real-time quantitative polymerase chain reaction and Western blot analyses.

RESULTS

TET1 existed in both the cytoplasm and the nucleus of the hDPCs. During serial cell passaging, TET1 expression significantly increased until the 6th passage and then decreased from the 7th-9th passages (P < .05, n = 3). TET1 gene and protein expression increased during the odontogenic differentiation of the hDPCs in a time-dependent manner (P < .05, n = 3).

CONCLUSIONS

TET1 messenger RNA and protein were both present in the hDPCs. TET1 expression increased during early spontaneous differentiation and odontogenic induction.

Dental pulp stem cells: state of the art and suggestions for a true translation of research into therapy

OBJECTIVES

Stem cells have the ability to rescue and/or repair injured tissue. In humans, it is possible to isolate different types of stem cells from the body. Among these, dental pulp stem cells (DPSCs) are relatively easily obtainable and exhibit high plasticity and multipotential capabilities. In particular they represent a gold standard for neural-crest-derived bone reconstruction in humans and can be used for the repair of body defects in low-risk autologous therapeutic strategies.

SOURCES

An electronic search was conducted on PubMed databases and supplemented with a manual study of relevant references.

RESULTS

All research described in this review highlight that DPSCs are mesenchymal stem cells that could be used in clinical applications. Unfortunately, very few clinical trials have been reported. Major obstacles imposed on researchers are hindering the translation of potentially effective therapies to the clinic. Both researchers and regulatory institutions need to develop a new approach to this problem, drawing up a new policy for good manufacturing practice (GMP) procedures. We strongly suggest that only general rules be standardized rather than everything. Importantly, this would not have an effect on the safety of patients, but may very well affect the results, which cannot be identical for all patients, due to physiological diversity in the biology of each patient. Alternatively, it would be important to study the role of specific molecules that recruit endogenous stem cells for tissue regeneration. In this way, the clinical use of stem cells could be successfully developed.

CONCLUSIONS

DPSCs are mesenchymal stem cells that differentiate into different tissues, maintain their characteristics after cryopreservation, differentiate into bone-like tissues when loaded on scaffolds in animal models, and regenerate bone in human grafts. In summary, all data reported up to now should encourage the development of clinical procedures using DPSCs.

Myogenic-induced mesenchymal stem cells are capable of modulating the immune response by regulatory T cells

Cell therapy for patients who have intractable muscle disorders may require highly regenerative cells from young, healthy allogeneic donors. Mesenchymal stem cells are currently under clinical investigation because they are known to induce muscle regeneration and believed to be immune privileged, thus making them suitable for allogeneic applications. However, it is unclear whether allogeneic and myogenic-induced mesenchymal stem cells retain their immunomodulatory characteristics. Therefore, our aim was to evaluate the effects of mesenchymal stem cell differentiation on the immune characteristics of cells in vitro. We investigated the immunologic properties of mesenchymal stem cells after myogenic induction. Mesenchymal stem cells were obtained from C57BL/6 mice and the C3H/10T1/2 murine mesenchymal stem cell line. Two different 5-aza-2'-deoxycytidine doses (0.5 and 3 µM) were evaluated for their effects on mesenchymal stem cell skeletal myogenic differentiation potential, immune antigen expression, and mixed lymphocytic reactions. Using a mixed lymphocytic reaction, we determined the optimal splenocyte proliferation inhibition dose. The induction of regulatory T cells was markedly increased by the addition of 3 µM 5-aza-2'-deoxycytidine-treated mesenchymal stem cells. Myogenic-induced mesenchymal stem cells do not elicit alloreactive lymphocyte proliferative responses and are able to modulate immune responses. These findings support the hypothesis that myogenic-induced mesenchymal stem cells may be transplantable across allogeneic barriers.

Dental pulp stem cells and their potential roles in central nervous system regeneration and repair

Functional recovery from injuries to the brain or spinal cord represents a major clinical challenge. The transplantation of stem cells, traditionally isolated from embryonic tissue, may help to reduce damage following such events and promote regeneration and repair through both direct cell replacement and neurotrophic mechanisms. However, the therapeutic potential of using embryonic stem/progenitor cells is significantly restricted by the availability of embryonic tissues and associated ethical issues. Populations of stem cells reside within the dental pulp, representing an alternative source of cells that can be isolated with minimal invasiveness, and thus should illicit fewer moral objections, as a replacement for embryonic/fetal-derived stem cells. Here we discuss the similarities between dental pulp stem cells (DPSCs) and the endogenous stem cells of the central nervous system (CNS) and their ability to differentiate into neuronal cell types. We also consider in vitro and in vivo studies demonstrating the ability of DPSCs to help protect against and repair neuronal damage, suggesting that dental pulp may provide a viable alternative source of stem cells for replacement therapy following CNS damage.

Neurogenic differentiation of human dental pulp stem cells using different induction protocols

OBJECTIVE

An investigation on neuronal differentiation capacity of human dental pulp stem cells (DPSCs) was still lacking. In this study, two different neuronal induction protocols were investigated and compared.

METHODS

The neuronal differentiation was induced using chemical or growth factor induction protocol. The differentiation was confirmed by the neurogenic mRNA and protein expression using polymerase chain reaction and immunocytochemistry, respectively.

RESULTS

Chemical-induced neuronal differentiation protocol promoted morphological change and β3-TUBULIN protein expression. Though, SOX2, SOX9, and β3-TUBULIN mRNA levels were not different compared with the control, indicating a defective differentiation. For growth factor induction protocol, the cells were exhibited neurite-like cellular process and positively stained with β3-TUBULIN. In addition, the increase in intracellular calcium was noted upon NMDA stimulation, implying the neuronal function. A dramatic increased mRNA expression of neurogenic markers [SOX2, SOX9, β3-TUBULIN, and gamma-aminobutyric acid (GABA receptors)] was noted as compared to the control. In addition, a remarkable increased expression of Notch signaling target gene, HEY1, was observed in growth factor-induced DPSCs derived neuronal-like cells compared with the control.

CONCLUSION

These data indicate that growth factor induction method is a preferable protocol for neuronal differentiation by DPSCs.

Engineering bone tissue using human dental pulp stem cells and an osteogenic collagen-hydroxyapatite-poly (L-lactide-co-ε-caprolactone) scaffold

The aim of this study was to design a new natural/synthetic bioactive bone scaffold for potential use in bone replacement applications. We developed a tri-component osteogenic composite scaffold made of collagen (Coll), hydroxyapatite (HA) and poly(l-lactide-co-ε-caprolactone) (PLCL). This Coll/HA/PLCL composite scaffold was combined with human osteoblast-like cells obtained by differentiation of dental pulp stem cells (DPSCs) to engineer bone tissue in vitro. Results show that the 3D Coll/HA/PLCL composite scaffold was highly porous, thereby enabling osteoblast-like cell adhesion and growth. Cultured in the Coll/HA/PLCL scaffold, the osteoblast-like cells expressed different osteogenic genes, produced alkaline phosphatase and formed nodules more than did PLCL alone. Micro-CT analyses revealed a significant (30%) increase of tissue mineralisation on the surface as well as inside of the Coll/HA/PLCL scaffold, thus confirming its effectiveness as a bone regeneration platform.

Modulation of cell cycle progression by 5-azacytidine is associated with early myogenesis induction in murine myoblasts

Myogenesis is a multistep process, in which myoblasts withdraw from the cell cycle, cease to divide, elongate and fuse to form multinucleated myotubes. Cell cycle transition is controlled by a family of cyclin-dependent protein kinases (CDKs) regulated by association with cyclins, negative regulatory subunits and phosphorylation. Muscle differentiation is orchestrated by myogenic regulatory factors (MRFs), such as MyoD and Myf-5. DNA methylation is crucial in transcriptional control of genes involved in myogenesis. Previous work has indicated that treatment of fibroblasts with the DNA-demethylating agent 5-azacytidine (AZA) promotes MyoD expression. We studied the effects of AZA on cell cycle regulation and MRFs synthesis during myoblast proliferation and early myogenesis phases in C2C12 cells. During the proliferation phase, cells were incubated in growth medium with 5µM AZA (GMAZA) or without AZA (GM) for 24 hours. At 70% confluence, cells were kept in growth medium in order to spontaneously achieve differentiation or transferred to differentiation medium with 5μM AZA (DMAZA) or without AZA (DM) for 12 and 24 hours. Cells used as control were unstimulated.

In the proliferation phase, AZA-treated cells seemed to lose their characteristic circular shape and become elongated. The presence of AZA resulted in significant increases in the protein contents of Cyclin-D (FC:1.23 GMAZA vs GM p≤0.05), p21 (FC: 1.23 GMAZA vs GM p≤0.05), Myf-5 (FC: 1.21 GMAZA vs GM p≤0.05) and MyoD (FC: 1.20 GMAZA vs GM p≤0.05). These results propose that AZA could inhibit cell proliferation.

During 12 hours of differentiation, AZA decreased the downregulation of genes involved in cell cycle arrest and in restriction point (G1 and G1/S phase) and the expression of several cyclins, E2F Transcription Factors, cyclin-dependent kinase inhibitors, specific genes responsible of cell cycle negative regulation. During 24 hours of differentiation, AZA induced an increment in the protein expression of Myf-5 (FC: 1.57 GMAZA vs GM p≤0.05), MyoD (FC: 1.14 DM vs GM p≤0.05; FC: 1.47 DMAZA vs GM p≤0.05), p21 (FC: 1.36 GMAZA vs GM p≤0.01; FC: 1.49 DM vs GM p≤0.05; FC: 1.82 DMAZA vs GM p≤0.01) and MyHC (FC: 1.40 GMAZA vs GM p≤0.01; FC: 2.39 DM vs GM p≤0.05; FC: 3.51 DMAZA vs GM p≤0.01). Our results suggest that AZA-induced DNA demethylation can modulate cell cycle progression and enhance myogenesis. The effects of AZA may open novel clinical uses in the field of muscle injury research and treatment.

Skeletal myogenic differentiation of human periodontal ligament stromal cells isolated from orthodontically extracted premolars

Objective

To investigate the stem cell-like characteristics of human periodontal ligament (PDL) stromal cells outgrown from orthodontically extracted premolars and to evaluate the potential for myogenic differentiation.

Methods

PDL stromal cells were obtained from extracted premolars by using the outgrowth method. Cell morphological features, self-replication capability, and the presence of cell-surface markers, along with osteogenic, adipogenic, and chondrogenic differentiation, were confirmed. In addition, myogenic differentiation was induced by the use of 5-aza-2'-deoxycytidine (5-Aza) for DNA demethylation.

Results

PDL stromal cells showed growth patterns and morphological features similar to those of fibroblasts. In contrast, the proliferation rates of premolar PDL stromal cells were similar to those of bone marrow and adipogenic stem cells. PDL stromal cells expressed surface markers of human mesenchymal stem cells (i.e., CD90 and CD105), but not those of hematopoietic stem cells (i.e., CD31 and CD34). PDL stromal cells were differentiated into osteogenic, adipogenic, and chondrogenic lineages. Myotube structures were induced in PDL stromal cells after 5-Aza pretreatment, but not in the absence of 5-Aza pretreatment.

Conclusions

PDL stromal cells isolated from extracted premolars can potentially be a good source of postnatal stem cells for oromaxillofacial regeneration in bone and muscle.

Dermal fibroblasts display similar phenotypic and differentiation capacity to fat-derived mesenchymal stem cells, but differ in anti-inflammatory and angiogenic potential

BACKGROUND

Mesenchymal stem cells (MSCs) are multipotent stem cells able to differentiate into different cell lineages. However, MSCs represent a subpopulation of a more complex cell composition of stroma cells contained in mesenchymal tissue. Due to a lack of specific markers, it is difficult to distinguish MSCs from other more mature stromal cells such as fibroblasts, which, conversely, are abundant in mesenchymal tissue. In order to find more distinguishing features between MSCs and fibroblasts, we studied the phenotypic and functional features of human adipose-derived MSCs (AD-MSCs) side by side with normal human dermal fibroblasts (HNDFs) in vitro

METHODS

AD-MSCs and HNDFs were cultured, expanded and phenotypically characterized by flow cytometry (FC). Immunofluorescence was used to investigate cell differentiation. ELISA assay was used to quantify angiogenic factors and chemokines release. Cultures of endothelial cells (ECs) and a monocyte cell line, U937, were used to test angiogenic and anti-inflammatory properties.

RESULTS

Cultured AD-MSCs and HNDFs display similar morphological appearance, growth rate, and phenotypic profile. They both expressed typical mesenchymal markers-CD90, CD29, CD44, CD105 and to a minor extent, the adhesion molecules CD54, CD56, CD106 and CD166. They were negative for the stem cell markers CD34, CD146, CD133, CD117. Only aldehyde dehydrogenase (ALDH) was expressed. Neither AD-MSCs nor HNDFs differed in their multi-lineage differentiation capacity; they both differentiated into osteoblast, adipocyte, and also into cardiomyocyte-like cells. In contrast, AD-MSCs, but not HNDFs, displayed strong angiogenic and anti-inflammatory activity. AD-MSCs released significant amounts of VEGF, HGF and Angiopoietins and their conditioned medium (CM) stimulated ECs proliferation and tube formations. In addition, CM-derived AD-MSCs (AD-MSCs-CM) inhibited adhesion molecules expression on U937 and release of RANTES and MCP-1. Finally, after priming with TNFα, AD-MSCs enhanced their anti-inflammatory potential; while HNDFs acquired pro-inflammatory activity.

CONCLUSIONS

AD-MSCs cannot be distinguished from HNDFs in vitro by evaluating their phenotypic profile or differentiation potential, but only through the analysis of their anti-inflammatory and angiogenic properties. These results underline the importance of evaluating the angiogenic and anti-inflammatory features of MSCs preparation. Their priming with inflammatory cytokines prior to transplantation may improve their efficacy in cell-based therapies for tissue regeneration.