Epigenetic changes in mesenchymal stem cells differentiation

The Effects of Chronological Age on the Chondrogenic Potential of Mesenchymal Stromal Cells: A Systematic Review

Tissue engineering and cell therapy for regenerative medicine have great potential to treat chronic disorders. In musculoskeletal disorders, mesenchymal stromal cells (MSCs) have been identified as a relevant cell type in cell and regenerative strategies due to their multi-lineage potential, although this is likely to be a result of their trophic and immunomodulatory effects on other cells. This PRISMA systematic review aims to assess whether the age of the patient influences the chondrogenic potential of MSCs in regenerative therapy. We identified a total of 3027 studies after performing a search of four databases, including Cochrane, Web of Science, Medline, and PubMed. After applying inclusion and exclusion criteria, a total of 14 papers were identified that were reviewed, assessed, and reported. Cell surface characterization and proliferation, as well as the osteogenic, adipogenic, and chondrogenic differentiation, were investigated as part of the analysis of these studies. Most included studies suggest a clear link between aged donor MSCs and diminished clonogenic and proliferative potential. Our study reveals a heterogeneous and conflicting range of outcomes concerning the chondrogenic, osteogenic, and adipogenic potential of MSCs in relation to age. Further investigations on the in vitro effects of chronological age on the chondrogenic potential of MSCs should follow the outcomes of this systematic review, shedding more light on this complex relationship.

CUL4B orchestrates mesenchymal stem cell commitment by epigenetically repressing KLF4 and C/EBPδ

Dysregulated lineage commitment of mesenchymal stem cells (MSCs) contributes to impaired bone formation and an imbalance between adipogenesis and osteogenesis during skeletal aging and osteoporosis. The intrinsic cellular mechanism that regulates MSC commitment remains unclear. Here, we identified Cullin 4B (CUL4B) as a critical regulator of MSC commitment. CUL4B is expressed in bone marrow MSCs (BMSCs) and downregulated with aging in mice and humans. Conditional knockout of Cul4b in MSCs resulted in impaired postnatal skeletal development with low bone mass and reduced bone formation. Moreover, depletion of CUL4B in MSCs aggravated bone loss and marrow adipose accumulation during natural aging or after ovariectomy. In addition, CUL4B deficiency in MSCs reduced bone strength. Mechanistically, CUL4B promoted osteogenesis and inhibited adipogenesis of MSCs by repressing KLF4 and C/EBPδ expression, respectively. The CUL4B complex directly bound to Klf4 and Cebpd and epigenetically repressed their transcription. Collectively, this study reveals CUL4B-mediated epigenetic regulation of the osteogenic or adipogenic commitment of MSCs, which has therapeutic implications in osteoporosis.

Epigenetic regulation of cancer-associated fibroblast heterogeneity

Cancer-associated fibroblasts (CAFs), a significant component of the tumor microenvironment (TME), contribute to cancer progression through the secretion of extracellular matrix (ECM), growth factors, and metabolites. It is now well recognized that CAFs are a heterogenous population with ablation experiments leading to reduced tumor growth and single-cell RNA sequencing demonstrating CAF subgroups. CAFs lack genetic mutations yet substantially differ from their normal stromal precursors. Here, we review epigenetic changes in CAF maturation, focusing on DNA methylation and histone modifications. DNA methylation changes in CAFs have been demonstrated globally, while roles of methylation at specific genes affect tumor growth. Further, loss of CAF histone methylation and gain of histone acetylation has been shown to promote CAF activation and tumor promotion. Many CAF activating factors, such as transforming growth factor β (TGFβ), lead to these epigenetic changes. MicroRNAs (miRNAs) serve as targets and orchestrators of epigenetic modifications that influence gene expression. Bromodomain and extra-terminal domain (BET), an epigenetic reader, recognizes histone acetylation and activates the transcription of genes leading to the pro-tumor phenotype of CAFs.

The role of epigenetic modifiers in the hepatic differentiation of human umbilical cord derived mesenchymal stem cells

Human umbilical cord (hUC) derived mesenchymal stem cells (MSCs) can be progressively differentiated into multiple lineages including hepatic lineages, and thus provide an excellent in vitro model system for the study of hepatic differentiation. At present, hepatic differentiation protocols are based on the use of soluble chemicals in the culture medium and provide immature hepatic like cells. Histone deacetylase inhibitors (HDACi) and DNA methyltransferase inhibitors (DNMTi) are two important epigenetic modifiers that regulate stem cell differentiation. Therefore, this study aimed to investigate the role of HDACi, valproic acid (VPA) and DNMTi,5-azacytidine (5-aza) along with a hepatic inducer in the hepatic differentiation of hUC-MSCs. hUC-MSCs were characterized via immunocytochemistry and flow cytometry. The final concentrations of VPA and 5-aza were optimized via MTT cytotoxicity assay. All treated groups were assessed for the presence of hepatic genes and proteins through qPCR and immunocytochemistry, respectively. The results showed that the pretreatment of epigenetic modifiers not only increased the hepatic genes but also increased the expression of the hepatic proteins. VPA induces hepatic differentiation in hUC-MSCs with significant gene expression of hepatic markers i.e., FOXA2 and CK8. Moreover, VPA pretreatment enhanced the expression of hepatic proteins AFP and TAT. The pretreatment of 5-aza shows significant gene expression of hepatic marker LDL-R. However, 5-aza treatment failed to induce hepatic protein expression. The results of the current study highlighted the effectiveness of epigenetic modifiers in the hepatic differentiation of hUC-MSCs. These differentiated cells can be employed in cell-based therapeutics for hepatic diseases in future.

Acly Deficiency Enhances Myelopoiesis through Acetyl Coenzyme A and Metabolic-Epigenetic Cross-Talk

Hematopoiesis integrates cytokine signaling, metabolism, and epigenetic modifications to regulate blood cell generation. These processes are linked, as metabolites provide essential substrates for epigenetic marks. In this study, we demonstrate that ATP citrate lyase (Acly), which metabolizes citrate to generate cytosolic acetyl-CoA and is of clinical interest, can regulate chromatin accessibility to limit myeloid differentiation. Acly was tested for a role in murine hematopoiesis by small-molecule inhibition or genetic deletion in lineage-depleted, c-Kit-enriched hematopoietic stem and progenitor cells from Mus musculus. Treatments increased the abundance of cell populations that expressed the myeloid integrin CD11b and other markers of myeloid differentiation. When single-cell RNA sequencing was performed, we found that Acly inhibitor-treated hematopoietic stem and progenitor cells exhibited greater gene expression signatures for macrophages and enrichment of these populations. Similarly, the single-cell assay for transposase-accessible chromatin sequencing showed increased chromatin accessibility at genes associated with myeloid differentiation, including CD11b, CD11c, and IRF8. Mechanistically, Acly deficiency altered chromatin accessibility and expression of multiple C/EBP family transcription factors known to regulate myeloid differentiation and cell metabolism, with increased Cebpe and decreased Cebpa and Cebpb. This effect of Acly deficiency was accompanied by altered mitochondrial metabolism with decreased mitochondrial polarization but increased mitochondrial content and production of reactive oxygen species. The bias to myeloid differentiation appeared due to insufficient generation of acetyl-CoA, as exogenous acetate to support alternate compensatory pathways to produce acetyl-CoA reversed this phenotype. Acly inhibition thus can promote myelopoiesis through deprivation of acetyl-CoA and altered histone acetylome to regulate C/EBP transcription factor family activity for myeloid differentiation.

Update on the application of mesenchymal stem cell-derived exosomes in the treatment of Parkinson's disease: A systematic review

Parkinson's disease (PD) has become the second largest neurodegenerative disease after Alzheimer's disease, and its incidence is increasing year by year. Traditional dopamine replacement therapy and deep brain stimulation can only alleviate the clinical symptoms of patients with PD but cannot cure the disease. In recent years, stem cell therapy has been used to treat neurodegenerative diseases. Many studies have shown that stem cell transplantation has a therapeutic effect on PD. Here, we review recent studies indicating that exosomes derived from mesenchymal stem cells also have the potential to treat PD in animal models, but the exact mechanism remains unclear. This article reviews the mechanisms through which exosomes are involved in intercellular information exchange, promote neuroprotection and freely cross the blood-brain barrier in the treatment of PD. The increase in the incidence of PD and the decline in the quality of life of patients with advanced PD have placed a heavy burden on patients, families and society. Therefore, innovative therapies for PD are urgently needed. Herein, we discuss the mechanisms underlying the effects of exosomes in PD, to provide new insights into the treatment of PD. The main purpose of this article is to explore the therapeutic potential of exosomes derived from mesenchymal stem cells and future research directions for this degenerative disease.

Fat Stem Cells Combined with Complement C3 Inhibits the Progress of Type 2 Diabetes in Rats

This study assessed the effect of fat stem cells combined with complement C3 on Wnt/β-catenin pathway in type 2 diabetic rats. 30 male rats were randomly and equally divided into group of type 2 diabetes (intraperitoneal injection of urea with cephalosporins at a dose of 30 mg/kg and fed with high sugar and fat), type 2 diabetes+adipose stem cells+C3 group (after adipose stem cells+C3 group) and control group. Rats in adipose stem cells+C3 group received administration of stem cells and C3. The model of type 2 diabetic rats was successfully constructed. The blood glucose of type 2 diabetic rats and fat stem cell+C3 group was significantly higher than 11.1 mmol/L. Adipocyte was induced to be differentiated into islet cells depending on insulin secretion and glucose concentration. The combination of complement C3 improved the glucose sensitivity in type 2 diabetic rats. Compared with diabetic group, β-catenin and TCF in fat stem cell+C3 group were significantly decreased (P < 0.05). In conclusion, fat stem cells combined with complement C3 inhibit the disease progression in type 2 diabetic rats possibly by inhibiting the activation of Wnt/β-catenin signaling pathway.

miRNA Expression Profile of Magnetic Field Combined with Nano-Scaffolds Enhance Chondrogenesis

The differentiation of mesenchymal stem cells (MSC) into cartilage is a critical step in the cartilage damage repair. Pulsed electromagnetic fields may provide a solution to promote the differentiation and proliferation of MSC, with a promisingly strong synergistic effect apparent when MSC subjected to magnetic nanoparticles and pulsed electromagnetic fields simultaneously. Previously, we developed a magnetic nanoparticles hydrogel (MagGel) that, when combined with magnetic fields, substantially enhanced cartilage tissue repair; however, we still know little about the mechanisms underlying its effectiveness. Here, we examined the role of magnetic fields and nano-scaffolds in promoting differentiation of MSCs into chondrocytes. Our results suggest that the mechanism causing MSC differentiation under these conditions resulted from the activation of multiple miRNAs and signaling pathways. These results can be built upon by future molecular studies to identify which miRNAs are involved in to chondrogenesis. By identifying these miRNAs and their targeted pathways, we can better manipulate the expression of the specific miRNAs that promote MSC differentiation and cartilage repair. Our study provides a starting point for the study of magnetic field-induced differentiation of the magnetic nanoparticles within stem cells.

KRAB-ZFPs and cancer stem cells identity

Studies on carcinogenesis continue to provide new information about different disease-related processes. Among others, much research has focused on the involvement of cancer stem cells (CSCs) in tumor initiation and progression. Studying the similarities and differences between CSCs and physiological stem cells (SCs) allows for a better understanding of cancer biology. Recently, it was shown that stem cell identity is partially governed by the Krϋppel-associated box domain zinc finger proteins (KRAB-ZFPs), the biggest family of transcription regulators. Several KRAB-ZFP factors exert a known effect in tumor cells, acting as tumor suppressor genes (TSGs) or oncogenes, yet their role in CSCs is still poorly characterized. Here, we review recent studies regarding the influence of KRAB-ZFPs and their cofactor protein TRIM28 on CSCs phenotype, stemness features, migration and invasion potential, metastasis, and expression of parental markers.

Changes in DNA methylation hallmark alterations in chromatin accessibility and gene expression for eye lens differentiation

Background

Methylation at cytosines (mCG) is a well-known regulator of gene expression, but its requirements for cellular differentiation have yet to be fully elucidated. A well-studied cellular differentiation model system is the eye lens, consisting of a single anterior layer of epithelial cells that migrate laterally and differentiate into a core of fiber cells. Here, we explore the genome-wide relationships between mCG methylation, chromatin accessibility and gene expression during differentiation of eye lens epithelial cells into fiber cells.

Results

Whole genome bisulfite sequencing identified 7621 genomic loci exhibiting significant differences in mCG levels between lens epithelial and fiber cells. Changes in mCG levels were inversely correlated with the differentiation state-specific expression of 1285 genes preferentially expressed in either lens fiber or lens epithelial cells (Pearson correlation r = − 0.37, p < 1 × 10^–42). mCG levels were inversely correlated with chromatin accessibility determined by assay for transposase-accessible sequencing (ATAC-seq) (Pearson correlation r = − 0.86, p < 1 × 10^–300). Many of the genes exhibiting altered regions of DNA methylation, chromatin accessibility and gene expression levels in fiber cells relative to epithelial cells are associated with lens fiber cell structure, homeostasis and transparency. These include lens crystallins (CRYBA4, CRYBB1, CRYGN, CRYBB2), lens beaded filament proteins (BFSP1, BFSP2), transcription factors (HSF4, SOX2, HIF1A), and Notch signaling pathway members (NOTCH1, NOTCH2, HEY1, HES5). Analysis of regions exhibiting cell-type specific alterations in DNA methylation revealed an overrepresentation of consensus sequences of multiple transcription factors known to play key roles in lens cell differentiation including HIF1A, SOX2, and the MAF family of transcription factors.

Conclusions

Collectively, these results link DNA methylation with control of chromatin accessibility and gene expression changes required for eye lens differentiation. The results also point to a role for DNA methylation in the regulation of transcription factors previously identified to be important for lens cell differentiation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13072-022-00440-z.

Bone Regeneration and Oxidative Stress: An Updated Overview

Bone tissue engineering is a complex domain that requires further investigation and benefits from data obtained over past decades. The models are increasing in complexity as they reveal new data from co-culturing and microfluidics applications. The in vitro models now focus on the 3D medium co-culturing of osteoblasts, osteoclasts, and osteocytes utilizing collagen for separation; this type of research allows for controlled medium and in-depth data analysis. Oxidative stress takes a toll on the domain, being beneficial as well as destructive. Reactive oxygen species (ROS) are molecules that influence the differentiation of osteoclasts, but over time their increasing presence can affect patients and aid the appearance of diseases such as osteoporosis. Oxidative stress can be limited by using antioxidants such as vitamin K and N-acetyl cysteine (NAC). Scaffolds and biocompatible coatings such as hydroxyapatite and bioactive glass are required to isolate the implant, protect the zone from the metallic, ionic exchange, and enhance the bone regeneration by mimicking the composition and structure of the body, thus enhancing cell proliferation. The materials can be further functionalized with growth factors that create a better response and higher chances of success for clinical use. This review highlights the vast majority of newly obtained information regarding bone tissue engineering, such as new co-culturing models, implant coatings, scaffolds, biomolecules, and the techniques utilized to obtain them.

miR-6807-5p Inhibited the Odontogenic Differentiation of Human Dental Pulp Stem Cells Through Directly Targeting METTL7A

Background: Tooth tissue regeneration mediated by mesenchymal stem cells (MSCs) has become the most ideal treatment. Although the known regulatory mechanism and some achievements have been discovered, directional differentiation cannot effectively induce regeneration of tooth tissue. In this study, we intended to explore the function and mechanism of miR-6807-5p and its target gene METTL7A in odontogenic differentiation.

Methods: In this study, human dental pulp stem cells (DPSCs) were used. Alkaline phosphatase (ALP), Alizarin red staining (ARS), and calcium ion quantification were used to detect the odontogenic differentiation of miR-6807-5p and METTL7A. Real-time RT-PCR, western blot, dual-luciferase reporter assay, and pull-down assay with biotinylated miRNA were used to confirm that METTL7A was the downstream gene of miR-6807-5p. Protein mass spectrometry and co-immunoprecipitation (Co-IP) were used to detect that SNRNP200 was the co-binding protein of METTL7A.

Results: After mineralized induction, the odontogenic differentiation was enhanced in the miR-6807-5p-knockdown group and weakened in the miR-6807-5p-overexpressed group compared with the control group. METTL7A was the downstream target of miR-6807-5p. After mineralized induction, the odontogenic differentiation was weakened in the METTL7A-knockdown group and enhanced in the METTL7A-overexpressed group compared with the control group. SNRNP200 was the co-binding protein of METTL7A. The knockdown of SNRNP200 inhibited the odontogenic differentiation of DPSCs.

Conclusion: This study verified that miR-6807-5p inhibited the odontogenic differentiation of DPSCs. The binding site of miR-6807-5p was the 3′UTR region of METTL7A, which was silenced by miR-6807-5p. METTL7A promoted the odontogenic differentiation of DPSCs. SNRNP200, a co-binding protein of METTL7A, promoted the odontogenic differentiation of DPSCs.

Adipose mesenchymal stem cells and gingival mesenchymal stem cells have a comparable effect in endothelium repair

Restenosis is the major factor influencing the long-term success rate of angioplasty and stent implantation and effective strategies to prevent restenosis remain limited. Mesenchymal stem cells (MSCs) are pluripotent stem cells capable of self-renewal and multidirectional differentiation, which may be able to promote endothelium repair, thereby reducing restenosis. The present study aimed to evaluate the effects of adipose MSCs (AMSCs) and gingival MSCs (GMSCs) on endothelium repair. MSCs were isolated from two human tissue types, namely adipose tissue and gingival tissue, and the effects of AMSCs and GMSCs in ex vivo endothelium repair and on vascular smooth muscle cell (SMC) growth were examined. To compare the feasibility of using AMSCs and GMSCs for the repair of endothelium damage in endothelial cell (EC) damage and vasoproliferative disorders, an ex vivo model of endothelium repair in a co-culture system was developed. It was indicated that AMSCs and GMSCs expressed characteristic MSC markers (CD105 and CD166). 3H-thymidine incorporation in the co-culture group of AMSCs and SMCs in the presence of ECs was lower compared with that in the GMSC and SMC co-culture group. The protein expression level of proliferating cell nuclear antigen in the co-culture group of AMSCs and SMCs in the presence of ECs were lower compared with that in the GMSC and SMC co-culture group. After co-culture with ECs for 5 days, 25.71±3.08% of AMSCs began to express CD31 protein and 20.06±2.09% of GMSCs began to express CD31 protein. Furthermore, anti-VEGF antibody was able to inhibit MSC differentiation. Collectively, the present results suggested that seeding of AMSCs had a stronger effect to inhibit the proliferation and migration of SMCs compared with GMSCs.

Natural Membrane Differentiates Human Adipose-Derived Mesenchymal Stem Cells to Neurospheres by Mechanotransduction Related to YAP and AMOT Proteins

Adipose tissue-derived mesenchymal stem cells (ADMSCs) are promising candidates for regenerative medicine, as they have good cell yield and can differentiate into several cell lines. When induced to the neuronal differentiation, they form neurospheres composed of neural precursors (NPs) that can be an alternative in treating neurodegenerative diseases. This study aimed to characterize NPs from neurospheres obtained after seeding ADMSCs on a natural polyisoprene-based membrane. The ADMSCs were isolated from adipose tissue by enzymatic dissociation, were subjected to trilineage differentiation, and were characterized by flow cytometry for specific ADMSC surface markers. For neuronal differentiation, the cells were seeded on polystyrene flasks coated with the membrane and were characterized by immunocytochemistry and RT-PCR. The results demonstrated that the isolated cells showed characteristics of ADMSCs. At 15 to 25 days, ADMSCs seeded on the natural membrane developed neurospheres. Then, after dissociation, the cells demonstrated characteristic neuronal markers expressed on NPs: nestin, ß-III tubulin, GFAP, NeuN, and the YAP1/AMOT in the cytoplasm. In conclusion, it was demonstrated that this membrane differentiates the ADMSCs to NPs without any induction factors, and suggests that their differentiation mechanisms are related to mechanotransduction regulated by the YAP and AMOT proteins.

Impact of the Epigenetically Regulated Hoxa-5 Gene in Neural Differentiation from Human Adipose-Derived Stem Cells

Human adipose-derived mesenchymal stem cells (hASCs) may be used in some nervous system pathologies, although obtaining an adequate degree of neuronal differentiation is an important barrier to their applicability. This requires a deep understanding of the expression and epigenetic changes of the most important genes involved in their differentiation. We used hASCs from human lipoaspirates to induce neuronal-like cells through three protocols (Neu1, 2, and 3), determined the degree of neuronal differentiation using specific biomarkers in culture cells and neurospheres, and analyzed epigenetic changes of genes involved in this differentiation. Furthermore, we selected the Hoxa-5 gene to determine its potential to improve neuronal differentiation. Our results showed that an excellent hASC neuronal differentiation process using Neu1 which efficiently modulated NES, CHAT, SNAP25, or SCN9A neuronal marker expression. In addition, epigenetic studies showed relevant changes in Hoxa-5, GRM4, FGFR1, RTEL1, METRN, and PAX9 genes. Functional studies of the Hoxa-5 gene using CRISPR/dCas9 and lentiviral systems showed that its overexpression induced hASCs neuronal differentiation that was accelerated with the exposure to Neu1. These results suggest that Hoxa-5 is an essential gene in hASCs neuronal differentiation and therefore, a potential candidate for the development of cell therapy strategies in neurological disorders.

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.

[New data on the molecular biology of soft tissue sarcoma]

Sarcoma consists in a group of rare malignant tumours of mesenchymal origin characterized by their vast clinical, pathological and biological heterogeneity. The pathological diagnosis of sarcoma relies classically of the differentiation features of tumour cells, with dozens of different tumour subtypes described in the last international classifications. Over the last decades, the advances in the development of new techniques of molecular biology have led to a major complexification of sarcoma classification, with the identification of multiple and specific molecular alterations that have led to significant changes for patients diagnostic, prognostic and therapeutic management. This review aims at giving an overview on the current knowledge of the molecular biology of soft tissue sarcoma, and emphasizes on their consequences for the daily management of patients.

DNMT1 Inhibitor Restores RUNX2 Expression and Mineralization in Periodontal Ligament Cells

Periodontal ligament cells (PDLCs) have well documented osteogenic potential; however, this commitment can be highly heterogenous, limiting their applications in tissue regeneration. In this study, we use PDLC populations characterized by high and low osteogenic potential (h-PDLCs and l-PDLCs, respectively) to identify possible sources of such heterogeneity and to investigate whether the osteogenic differentiation can be enhanced by epigenetic modulation. In h-PDLCs, low basal expression levels of pluripotency markers (NANOG, OCT4), DNA methyltransferases (DNMT1, DNMT3B), and enzymes involved in active DNA demethylation (TET1, TET3) were prerequisite to high osteogenic potential. Furthermore, these genes were downregulated upon early osteogenesis, possibly allowing for the increase in expression of the key osteogenic transcription factors, Runt-related transcription factor 2 (RUNX2) and SP7, and ultimately, mineral nodule formation. l-PDLCs appeared locked in the multipotent state and this was further enhanced upon early osteogenic stimulation, correlating with low RUNX2 expression and impaired mineralization. Further upregulation of DNMTs was also evident, while pretreatment with RG108, the DNMTs' inhibitor, enhanced the osteogenic program in l-PDLCs through downregulation of DNMTs, increased RUNX2 expression and nuclear localization, accelerated expression of osteogenic markers, and increased mineralization. These findings point toward the role of DNMTs and Ten Eleven Translocations (TETs) in osteogenic commitment and support application of epigenetic approaches to modulate biomineralization in PDLCs.

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.

Adipose tissue-derived mesenchymal stem cells for breast tissue regeneration

With an escalating incidence of breast cancer cases all over the world and the deleterious psychological impact that mastectomy has on patients along with several limitations of the currently applied modalities, it's plausible to seek unconventional approaches to encounter such a burgeoning issue. Breast tissue engineering may allow that chance via providing more personalized solutions which are able to regenerate, mimicking natural tissues also facing the witnessed limitations. This review is dedicated to explore the utilization of adipose tissue-derived mesenchymal stem cells for breast tissue regeneration among postmastectomy cases focusing on biomaterials and cellular aspects in terms of harvesting, isolation, differentiation and new tissue formation as well as scaffolds types, properties, material-host interaction and an in vitro breast tissue modeling.

SETD4 in the Proliferation, Migration, Angiogenesis, Myogenic Differentiation and Genomic Methylation of Bone Marrow Mesenchymal Stem Cells

Epigenetic modification is a crucial mechanism affecting the biological function of stem cells. SETD4 is a histone methyltransferase, and its biological role in bone marrow mesenchymal stem cells (BMSCs) is currently unknown. In this study, we employed CRISPR/Cas9 technology edited mouse model and found that SETD4 knockout significantly promoted the proliferation of BMSCs, impaired BMSCs migration and differentiation potentials of lineages of cardiacmyocyte and smooth muscle cell, and even the angiogenesis via paracrine of VEGF. Through Reduced Representation Bisulfite Sequencing (RRBS) method, we verified that the overall genomic methylation of BMSCs in the SETD4 knockout group only was decreased by 0.47 % compared with wild type. However, the changed genomic methylation covers a total of 96,331 differential methylated CpG sites and 8,692 differential methylation regions (DMRs), with part of them settled in promoter regions. Bioinformatic analysis revealed that differential CpG islands and DMRs in promoter impacted 270 GO functions and 34 KEGG signaling pathways, with some closely related to stem cell biology. Mechanismly, SETD4 knockout inhibited sets of monomethylases and dimethylases for histone lysine, along with significant changes in some factors including Nkx2.5, Gata4, Gli2, Grem2, E2f7, Map7, Nr2f2 and Shox2 that associated with stem cell biology. These results are the first to reveal that even though SETD4 changes the genome's overall methylation to a limited extent in BMSCs, it still affects the numerous cellular functions and signaling pathways, implying SETD4-altered genomic methylation serves a crucial molecular role in BMSCs' biological functions.

Emerging histone glutamine modifications mediated gene expression in cell differentiation and the VTA reward pathway

Gene expression is the key to cellular functions and homeostasis. Histone modifications regulate chromatin dynamics and gene expression. Neuronal cell functions largely depend on fluxes of neurotransmitters for activation of chromatin and gene expression. New studies by Lepack et al. and Farrelly et al. recently demonstrated how tissue transglutaminase 2 (TGM2) mediated histone glutamine modifications, either dopaminylation in the dopaminergic reward pathway or serotonylation in the context of cellular differentiation and signaling regulate gene expression and decipher striking differences from their known functions. This opens new avenues of research in the field of epigenetics in general and neuroepigenetics as special; and to find out the enzymes responsible for the reversible reaction of histone de-dopaminylation and de-serotonylation.

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.

Epigenetic silencing of the osteoblast-lineage gene program during hippocampal maturation

Accumulating evidence indicates that epigenetic control of gene expression plays a significant role during cell lineage commitment and subsequent cell fate maintenance. Here, we assess epigenetic mechanisms operating in the rat brain that mediate silencing of genes that are expressed during early and late stages of osteogenesis. We report that repression of the osteoblast master regulator Sp7 in embryonic (E18) hippocampus is mainly mediated through the Polycomb complex PRC2 and its enzymatic product H3K27me3. During early postnatal (P10), juvenile (P30), and adult (P90) hippocampal stages, the repressive H3K27me3 mark is progressively replaced by nucleosome enrichment and increased CpG DNA methylation at the Sp7 gene promoter. In contrast, silencing of the late bone phenotypic Bglap gene in the hippocampus is PRC2-independent and accompanied by strong CpG methylation from E18 through postnatal and adult stages. Forced ectopic expression of the primary master regulator of osteogenesis Runx2 in embryonic hippocampal neurons activates the expression of its downstream target Sp7 gene. Moreover, transcriptomic analyses show that several genes associated with the mesenchymal-osteogenic lineages are transcriptionally activated in these hippocampal cells that express Runx2 and Sp7. This effect is accompanied by a loss in neuronal properties, including a significant reduction in secondary processes at the dendritic arbor and reduced expression of critical postsynaptic genes like PSD95. Together, our results reveal a developmental progression in epigenetic control mechanisms that repress the expression of the osteogenic program in hippocampal neurons at embryonic, postnatal, and adult stages.

Epidrugs: novel epigenetic regulators that open a new window for targeting osteoblast differentiation

Efficient osteogenic differentiation of mesenchymal stem cells (MSCs) is a critical step in the treatment of bone defects and skeletal disorders, which present challenges for cell-based therapy and regenerative medicine. Thus, it is necessary to understand the regulatory agents involved in osteogenesis. Epigenetic mechanisms are considered to be the primary mediators that regulate gene expression during MSC differentiation. In recent years, epigenetic enzyme inhibitors have been used as epidrugs in cancer therapy. A number of studies mentioned the role of epigenetic inhibitors in the regulation of gene expression patterns related to osteogenic differentiation. This review attempts to provide an overview of the key regulatory agents of osteogenesis: transcription factors, signaling pathways, and, especially, epigenetic mechanisms. In addition, we propose to introduce epigenetic enzyme inhibitors (epidrugs) and their applications as future therapeutic approaches for bone defect regeneration.

Examining the Characteristics and Applications of Mesenchymal, Induced Pluripotent, and Embryonic Stem Cells for Tissue Engineering Approaches across the Germ Layers

The field of regenerative medicine utilizes a wide array of technologies and techniques for repairing and restoring function to damaged tissues. Among these, stem cells offer one of the most potent and promising biological tools to facilitate such goals. Implementation of mesenchymal stem cells (MSCs), induced pluripotent stem cells (iPSCs), and embryonic stem cells (ESCs) offer varying advantages based on availability and efficacy in the target tissue. The focus of this review is to discuss characteristics of these three subset stem cell populations and examine their utility in tissue engineering. In particular, the development of therapeutics that utilize cell-based approaches, divided by germinal layer to further assess research targeting specific tissues of the mesoderm, ectoderm, and endoderm. The combinatorial application of MSCs, iPSCs, and ESCs with natural and synthetic scaffold technologies can enhance the reparative capacity and survival of implanted cells. Continued efforts to generate more standardized approaches for these cells may provide improved study-to-study variations on implementation, thereby increasing the clinical translatability of cell-based therapeutics. Coupling clinically translatable research with commercially oriented methods offers the potential to drastically advance medical treatments for multiple diseases and injuries, improving the quality of life for many individuals.

Raman imaging as a new analytical tool for the quality control of the monitoring of osteogenic differentiation in forming 3D bone tissue

In this study, adipose-derived stem cells (ASCs) are used to produce 3D bone grafts. The safety and the feasibility of using these bone grafts have been already showed and quality controls are already implemented. However, a cheaper, fast and non-destructive technique is required to monitor the osteogenic differentiation process. Here, the use of Raman imaging to monitor the synthesis of the extracellular matrix and its progressive mineralization occurring during the osteogenic differentiation process is investigated for the first time on a 3D in forming bone tissue. The attention was focused on Raman bands related to this matrix belonging to phosphate, phenylalanine and hydroxyproline, which are very distinctive and intense. The kinetic of the osteogenic differentiation process was first compared between a 2D and a 3D forming bone tissue. It was observed that the kinetics of the osteogenic differentiation process is slower in 3D in forming bone tissue. In a second step, an evaluation of the reliability of the Raman imaging method was performed including a study of the influence of the harvest biopsies position on the forming 3D bone tissue. The repeatability and the specificity of this method were also demonstrated. In a last step, several batches of ASCs were cultured and analyzed in 3D at different time points using Raman imaging. From the mean Raman spectra, mineral to matrix ratios (MTMR) were determined and used to evaluate the formation of mineral deposits accompanying the extracellular matrix synthesis which is indicative of an ongoing osteogenic differentiation process. These ratios peaked between the day 35 and 49. This observation was very interesting since it corresponds to the time at which the 3D bone grafts are used for the patient surgery. To conclude, Raman imaging allowed fast acquisition and time-resolved monitoring in vitro of the mineralization of extracellular matrix during osteogenic differentiation.

Functional Relationship between Osteogenesis and Angiogenesis in Tissue Regeneration

Bone tissue renewal can be outlined as a complicated mechanism centered on the interaction between osteogenic and angiogenic events capable of leading to bone formation and tissue renovation. The achievement or debacle of bone regeneration is focused on the primary role of vascularization occurrence; in particular, the turning point is the opportunity to vascularize the bulk scaffolds, in order to deliver enough nutrients, growth factors, minerals and oxygen for tissue restoration. The optimal scaffolds should ensure the development of vascular networks to warrant a positive suitable microenvironment for tissue engineering and renewal. Vascular Endothelial Growth Factor (VEGF), a main player in angiogenesis, is capable of provoking the migration and proliferation of endothelial cells and indirectly stimulating osteogenesis, through the regulation of the osteogenic growth factors released and through paracrine signaling. For this reason, we concentrated our attention on two principal groups involved in the renewal of bone tissue defects: the cells and the scaffold that should guarantee an effective vascularization process. The application of Mesenchymal Stem Cells (MSCs), an excellent cell source for tissue restoration, evidences a crucial role in tissue engineering and bone development strategies. This review aims to provide an overview of the intimate connection between blood vessels and bone formation that appear during bone regeneration when MSCs, their secretome—Extracellular Vesicles (EVs) and microRNAs (miRNAs) —and bone substitutes are used in combination.

Epigenetic metabolites license stem cell states

It has become clear during recent years that stem cells undergo metabolic remodeling during their activation process. While these metabolic switches take place in pluripotency as well as adult stem cell populations, the rules that govern the switch are not clear. In this review, we summarize some of the transitions in adult and pluripotent cell types and will propose that the key function in this process is the generation of epigenetic metabolites that govern critical epigenetic modifications, and therefore stem cell states.

Control of mesenchymal stem cell biology by histone modifications

Mesenchymal stem cells (MSCs) are considered the most promising seed cells for regenerative medicine because of their considerable therapeutic properties and accessibility. Fine-tuning of cell biological processes, including differentiation and senescence, is essential for achievement of the expected regenerative efficacy. Researchers have recently made great advances in understanding the spatiotemporal gene expression dynamics that occur during osteogenic, adipogenic and chondrogenic differentiation of MSCs and the intrinsic and environmental factors that affect these processes. In this context, histone modifications have been intensively studied in recent years and have already been indicated to play significant and universal roles in MSC fate determination and differentiation. In this review, we summarize recent discoveries regarding the effects of histone modifications on MSC biology. Moreover, we also provide our insights and perspectives for future applications.

The epigenetic reader Brd4 is required for osteoblast differentiation

Transcription networks and epigenetic mechanisms including DNA methylation, histone modifications, and noncoding RNAs control lineage commitment of multipotent mesenchymal progenitor cells. Proteins that read, write, and erase histone tail modifications curate and interpret the highly intricate histone code. Epigenetic reader proteins that recognize and bind histone marks provide a crucial link between histone modifications and their downstream biological effects. Here, we investigate the role of bromodomain-containing (BRD) proteins, which recognize acetylated histones, during osteogenic differentiation. Using RNA-sequencing (RNA-seq) analysis, we screened for BRD proteins (n = 40) that are robustly expressed in MC3T3 osteoblasts. We focused functional follow-up studies on Brd2 and Brd4 which are highly expressed in MC3T3 preosteoblasts and represent "bromodomain and extra terminal domain" (BET) proteins that are sensitive to pharmacological agents (BET inhibitors). We show that small interfering RNA depletion of Brd4 has stronger inhibitory effects on osteoblast differentiation than Brd2 loss as measured by osteoblast-related gene expression, extracellular matrix deposition, and alkaline phosphatase activity. Similar effects on osteoblast differentiation are seen with the BET inhibitor +JQ1, and this effect is reversible upon its removal indicating that this small molecule has no lasting effects on the differentiation capacity of MC3T3 cells. Mechanistically, we find that Brd4 binds at known Runx2 binding sites in promoters of bone-related genes. Collectively, these findings suggest that Brd4 is recruited to osteoblast-specific genes and may cooperate with bone-related transcription factors to promote osteoblast lineage commitment and maturation.

Red Raspberry Polyphenols Attenuate High-Fat Diet-Driven Activation of NLRP3 Inflammasome and its Paracrine Suppression of Adipogenesis via Histone Modifications

SCOPE

The authors aim to investigate the mechanisms by which red raspberry (RR) polyphenolic fractions regulate obesity and inflammation with an emphasis on the crosstalk between adipose tissue macrophages (ATM) and adipocyte progenitors.

METHODS AND RESULTS

C57BL/6 male mice are fed either a high-fat (HF) diet or an HF diet supplemented with a RR polyphenolic fraction from whole fruit, pulp, or seed. Supplementation with pulp significantly increases energy expenditure and reduces HF-diet-induced obesity and insulin resistance. The pulp, and to a lesser extent, whole polyphenols, decreases the recruitment of ATM, activation of the nod-like receptor protein 3 (NLRP3) inflammasome, and adipocyte hypertrophy, which is associated with epigenetic modulation of adipogenesis (e.g., H3K27Ac, H3K9Ac). Results from an IL-1β reporter assay in J774 macrophages recapitulate the inhibitory role of RR polyphenols on NLRP3 inflammasome activation. Using conditioned media from macrophages, it is demonstrated that RR polyphenols reverse the IL-1β-mediated epigenetic suppression of H3K27Ac in adipocyte progenitor cells.

CONCLUSIONS

RR polyphenols from pulp and whole fruit serve as an inhibitor for NLRP3 inflammasome activation and an epigenetic modifier to regulate adipogenesis, which confers resistance against diet-induced obesity and metabolic dysfunction.

PTH1-34 improves bone healing by promoting angiogenesis and facilitating MSCs migration and differentiation in a stabilized fracture mouse model

Objective

PTH_1-34 (parathyroid hormone 1–34) is the only clinical drug to promote osteogenesis. MSCs (mesenchymal stem cells) have multidirectional differentiation potential and are closely related to fracture healing. This study was to explore the effects of PTH_1-34 on proliferation and differentiation of endothelial cells and MSCs in vitro, and on angiogenesis, and MSCs migration during fracture healing in vivo.

Methods

Mice with stabilized fracture were assigned to 4 groups: CON, PTH (PTH_1-34 40 μg/kg/day), MSC (transplanted with 10⁵ MSCs), PTH+MSCs. Mice were sacrificed 14 days after fracture, and callus tissues were harvested for microCT scan and immunohistochemistry analysis. The effects of PTH_1-34 on angiogenesis, and MSCs differentiation and migration were assessed by wound healing, tube formation and immunofluorescence staining.

Results

Treatment with either PTH_1-34, or MSCs promoted bone healing and vascular formation in fracture callus. The callus bone mass, bone volume, and bone mineral density were all greater in PTH and/or MSC groups than they were in CON (p<0.05). PTH_1-34 increased small vessels formation (diameter ≤50μm), whereas MSCs increased the large ones (diameter >50μm). Expression of CD31 within calluses and trabecular bones were significantly higher in PTH_1-34 treated group than that of not (p<0.05). Expression of CD31, VEGFR, VEGFR2, and vWF was upregulated, and wound healing and tube formation were increased in MSCs treated with PTH_1-34 compared to that of control.

Conclusions

PTH_1-34 improved the proliferation and differentiation of endothelial cells and MSCs, enhancing migration of MSCs to bone callus to promote angiogenesis and osteogenesis, and facilitating fracture healing.

Novel Aptamer-Functionalized Nanoparticles Enhances Bone Defect Repair By Improving Stem Cell Recruitment

Background

The restoration and repair method in the clinic of delayed fracture healing and non-union after comminuted fractures are urgently needed to improve the prognosis of patients. The recruitment of endogenous stem cells has been considered a promising approach in bone defect repair.

Propose

The aim of this study was to generate a de novel MSCs aptamer and developed the first, feasible, economical, bio-compatible, and functional MSCs aptamer-directed nanoparticles without complex manufacture to recruit mesenchymal stem cells (MSCs) for bone defect regeneration.

Methods

Whole-cell SELEX was used to generate a de novel MSCs aptamer. Flow cytometry was applied to assess the binding specificities, affinities and sorting abilities of the aptamers. Nano-Aptamer Ball (NAB) was constructed by NHS/EDC reaction. The diameter and zeta of NAB were assessed by dynamic light scattering. CCK8 assay was utilized to evaluate whether NAB could cause non-specific cytotoxicity and induce cell proliferation. To evaluate the bone repair capacity of NAB, histomorphological staining, alizarin red and micro X-ray were used to observe the repair degree of defect in vivo. ELISA was used to detect osteopontin (OPN), osteocalcin (BGP) by, and alkaline phosphatase (ALP) in peripheral blood.

Results

MSCs aptamer termed as HM69 could bind with MSCs with high specificity and Kd of 9.67 nM, while has minimal cross-reactivities to other negative cells. HM69 could capture MSCs with a purity of >89%. In vitro, NAB could bind and capture MSCs effectively, whereas did not cause obvious cytotoxicity. In vivo, serum OPN, BGP, and ALP levels in the NAB group of rats were increased at both 2 and 4 weeks, indicating the repair and osteogenesis generation. The healing of bone defects in the NAB group was significantly better than control groups, the defects became blurred, and local trabecular bone growth could be observed in X-ray. The organized hematoma and cell growth in the bone marrow of the NAB group were more vigorous in bone sections staining.

Conclusion

These suggested that HM69 and HM69-functionalized nanoparticles NAB exhibited the ability to recruit MSCs both in vitro and in vivo and achieved a better outcome of bone defect repair in a rat model. The findings demonstrate a promising strategy of using aptamer-functionalized bio-nanoparticles for the restoration of bone defects via aptamer-introduced homing of MSCs.

The Role of Mesenchymal Stem Cells in Atherosclerosis: Prospects for Therapy via the Modulation of Inflammatory Milieu

Atherosclerosis is a chronic, inflammatory disease that mainly affects the arterial intima. The disease is more prevalent in middle-age and older individuals with one or more cardiovascular risk factors, including dyslipidemia, hypertension, diabetes, smoking, obesity, and others. The beginning and development of atherosclerosis has been associated with several immune components, including infiltration of inflammatory cells, monocyte/macrophage-derived foam cells, and inflammatory cytokines and chemokines. Mesenchymal stem cells (MSCs) originate from several tissue sources of the body and have self-renewal and multipotent differentiation characteristics. They also have immunomodulatory and anti-inflammatory properties. Recently, it was shown that MSCs have a regulatory role in plasma lipid levels. In addition, MSCs have shown to have promising potential in terms of treatment strategies for several diseases, including those with an inflammatory component. In this regard, transplantation of MSCs to patients with atherosclerosis has been proposed as a novel strategy in the treatment of this disease. In this review, we summarize the current advancements regarding MSCs for the treatment of atherosclerosis.

Chitosan-based scaffold counteracts hypertrophic and fibrotic markers in chondrogenic differentiated mesenchymal stromal cells

Cartilage tissue engineering remains problematic because no systems are able to induce signals that contribute to native cartilage structure formation. Therefore, we tested the potentiality of gelatin-polyethylene glycol scaffolds containing three different concentrations of chitosan (CH; 0%, 8%, and 16%) on chondrogenic differentiation of human platelet lysate-expanded human bone marrow mesenchymal stromal cells (hBM-MSCs). Typical chondrogenic (SOX9, collagen type 2, and aggrecan), hypertrophic (collagen type 10), and fibrotic (collagen type 1) markers were evaluated at gene and protein level at Days 1, 28, and 48. We demonstrated that 16% CH scaffold had the highest percentage of relaxation with the fastest relaxation rate. In particular, 16% CH scaffold, combined with chondrogenic factor TGFβ3, was more efficient in inducing hBM-MSCs chondrogenic differentiation compared with 0% or 8% scaffolds. Collagen type 2, SOX9, and aggrecan showed the same expression in all scaffolds, whereas collagen types 10 and 1 markers were efficiently down-modulated only in 16% CH. We demonstrated that using human platelet lysate chronically during hBM-MSCs chondrogenic differentiation, the chondrogenic, hypertrophic, and fibrotic markers were significantly decreased. Our data demonstrate that only a high concentration of CH, combined with TGFβ3, creates an environment capable of guiding in vitro hBM-MSCs towards a phenotypically stable chondrogenesis.

Mesenchymal Stem Cells for Spinal Cord Injury: Current Options, Limitations, and Future of Cell Therapy

Spinal cord injury (SCI) constitutes an inestimable public health issue. The most crucial phase in the pathophysiological process of SCI concerns the well-known secondary injury, which is the uncontrolled and destructive cascade occurring later with aberrant molecular signaling, inflammation, vascular changes, and secondary cellular dysfunctions. The use of mesenchymal stem cells (MSCs) represents one of the most important and promising tested strategies. Their appeal, among the other sources and types of stem cells, increased because of their ease of isolation/preservation and their properties. Nevertheless, encouraging promise from preclinical studies was followed by weak and conflicting results in clinical trials. In this review, the therapeutic role of MSCs is discussed, together with their properties, application, limitations, and future perspectives.

The Impact of Epigenetic Signatures on Amniotic Fluid Stem Cell Fate

Epigenetic modifications play a significant role in determining the fate of stem cells and in directing the differentiation into multiple lineages. Current evidence indicates that mechanisms involved in chromatin regulation are essential for maintaining stable cell identities. There is a tight correlation among DNA methylation, histone modifications, and small noncoding RNAs during the epigenetic control of stem cells' differentiation; however, to date, the precise mechanism is still not clear. In this context, amniotic fluid stem cells (AFSCs) represent an interesting model due to their unique features and the possible advantages of their use in regenerative medicine. Recent studies have elucidated epigenetic profiles involved in AFSCs' lineage commitment and differentiation. In order to use these cells effectively for therapeutic purposes, it is necessary to understand the basis of multiple-lineage potential and elaborate in detail how cell fate decisions are made and memorized. The present review summarizes the most recent findings on epigenetic mechanisms of AFSCs with a focus on DNA methylation, histone modifications, and microRNAs (miRNAs) and addresses how their unique signatures contribute to lineage-specific differentiation.

Zebularine Promotes Hepatic Differentiation of Rabbit Bone Marrow Mesenchymal Stem Cells by Interfering with p38 MAPK Signaling

Demethylating agent zebularine is reported to be capable of inducing differentiation of stem cells by activation of methylated genes, though its function in hepatocyte differentiation is unclear. p38 signal pathway is involved in differentiation of hepatocytes and regulating of DNA methyltransferases 1 (DNMT1) expression. However, little is known about the impact of zebularine on bone marrow mesenchymal stem cells (BMMSCs) and p38 signaling during hepatic differentiation. The present study investigated the effects of zebularine on hepatic differentiation of rabbit BMMSCs, as well as the role of p38 on DNMT1 and hepatic differentiation, with the aim of developing a novel strategy for improving derivation of hepatocytes. BMMSCs were treated with zebularine at concentrations of 10, 20, 50, and 100 μM in the presence of hepatocyte growth factor; changes in the levels of hepatic-specific alpha-fetoprotein and albumin were detected and determined by RT-PCR, WB, and immunofluorescence staining. Expression of DNMT1 and phosphorylated p38 as well as urea production and ICG metabolism was also analyzed. Zebularine at concentrations of 10, 20, and 50 μM could not affect cell viability after 48 h. Zebularine treatment leads to an inhibition of DNMT activity and increase of hepatic-specific proteins alpha-fetoprotein and albumin in BMMSCs in vitro; zebularine addition also induced expression of urea production of and ICG metabolism. p38 signal was activated in BMMSCs simulated with HGF; inhibition of p38 facilitated the synthesis of DNMT1 and albumin in cells. Zebularine restrained DNMT1 and phosphorylated p38 which were induced by HGF. Therefore, this study demonstrated that treatment with zebularine exhibited terminal hepatic differentiation of BMMSCs in vitro in association with hepatocyte growth factor; p38 pathway at least partially participates in zebularine-induced hepatic differentiation of rabbit BMMSCs.

Epigenetic Crosstalk between the Tumor Microenvironment and Ovarian Cancer Cells: A Therapeutic Road Less Traveled

Metastatic dissemination of epithelial ovarian cancer (EOC) predominantly occurs through direct cell shedding from the primary tumor into the intra-abdominal cavity that is filled with malignant ascitic effusions. Facilitated by the fluid flow, cells distribute throughout the cavity, broadly seed and invade through peritoneal lining, and resume secondary tumor growth in abdominal and pelvic organs. At all steps of this unique metastatic process, cancer cells exist within a multidimensional tumor microenvironment consisting of intraperitoneally residing cancer-reprogramed fibroblasts, adipose, immune, mesenchymal stem, mesothelial, and vascular cells that exert miscellaneous bioactive molecules into malignant ascites and contribute to EOC progression and metastasis via distinct molecular mechanisms and epigenetic dysregulation. This review outlines basic epigenetic mechanisms, including DNA methylation, histone modifications, chromatin remodeling, and non-coding RNA regulators, and summarizes current knowledge on reciprocal interactions between each participant of the EOC cellular milieu and tumor cells in the context of aberrant epigenetic crosstalk. Promising research directions and potential therapeutic strategies that may encompass epigenetic tailoring as a component of complex EOC treatment are discussed.

Developmentally linked human DNA hypermethylation is associated with down-modulation, repression, and upregulation of transcription

DNA methylation can affect tissue-specific gene transcription in ways that are difficult to discern from studies focused on genome-wide analyses of differentially methylated regions (DMRs). To elucidate the variety of associations between differentiation-related DNA hypermethylation and transcription, we used available epigenomic and transcriptomic profiles from 38 human cell/tissue types to focus on such relationships in 94 genes linked to hypermethylated DMRs in myoblasts (Mb). For 19 of the genes, promoter-region hypermethylation in Mb (and often a few heterologous cell types) was associated with gene repression but, importantly, DNA hypermethylation was absent in many other repressed samples. In another 24 genes, DNA hypermethylation overlapped cryptic enhancers or super-enhancers and correlated with down-modulated, but not silenced, gene expression. However, such methylation was absent, surprisingly, in both non-expressing samples and highly expressing samples. This suggests that some genes need DMR hypermethylation to help repress cryptic enhancer chromatin only when they are actively transcribed. For another 11 genes, we found an association between intergenic hypermethylated DMRs and positive expression of the gene in Mb. DNA hypermethylation/transcription correlations similar to those of Mb were evident sometimes in diverse tissues, such as aorta and brain. Our findings have implications for the possible involvement of methylated DNA in Duchenne's muscular dystrophy, congenital heart malformations, and cancer. This epigenomic analysis suggests that DNA methylation is not simply the inevitable consequence of changes in gene expression but, instead, is often an active agent for fine-tuning transcription in association with development.