The histone demethylases Jhdm1a/1b enhance somatic cell reprogramming in a vitamin-C-dependent manner

On the physiological and cellular homeostasis of ascorbate

Recent interest in the role of ascorbate in crucial metabolic processes is driven by the growing number of medical reports that show beneficial effects of ascorbate supplementation for maintaining general well-being and recovery from a variety of medical conditions. The effect of ascorbate on the local body environment highly depends on its local concentration; at low concentrations it can cause the reduction of reactive oxygen and facilitate activities of enzymes, while at high concentrations it generates free radicals by reducing ferric ions. Ascorbate serving as an electron donor assists the iron-containing proteins and the iron transfer between various aqueous compartments. These functions require effective and adjustable mechanisms responsible for ascorbate biodistribution. In the paper we propose a new biophysical model of ascorbate redistribution between various aqueous body compartments. It combines recent experimental evidence regarding the ability of ascorbate to cross the lipid bilayer by unassisted diffusion, with active transport by well-characterized sodium vitamin C transporter (SVCT) membrane proteins. In the model, the intracellular concentration of ascorbate is maintained by the balance of two opposing fluxes: fast active and slow passive transport. The model provides a mechanistic understanding of ascorbate flux across the epidermal barrier in the gut as well as the role of astrocytes in ascorbate recycling in the brain. In addition, ascorbate passive diffusion across biological membranes, which depends on membrane electric potentials and pH gradients, provides the rationale for the correlation between ascorbate distribution and the transfer of iron ions inside a cell. The proposed approach provides, for the first time, a mechanistic account of processes leading to ascorbate physiological and cellular distribution, which helps to explain numerous experimental and clinical observations.

Ascorbic Acid Promotes Functional Restoration after Spinal Cord Injury Partly by Epigenetic Modulation

Axonal regeneration after spinal cord injury (SCI) is difficult to achieve, and no fundamental treatment can be applied in clinical settings. DNA methylation has been suggested to play a role in regeneration capacity and neuronal growth after SCI by controlling the expression of regeneration-associated genes (RAGs). The aim of this study was to examine changes in neuronal DNA methylation status after SCI and to determine whether modulation of DNA methylation with ascorbic acid can enhance neuronal regeneration or functional restoration after SCI. Changes in epigenetic marks (5-hydroxymethylcytosine (5hmC) and 5-methylcytosine (5mC)); the expression of Ten-eleven translocation (Tet) family genes; and the expression of genes related to inflammation, regeneration, and degeneration in the brain motor cortex were determined following SCI. The 5hmC level within the brain was increased after SCI, especially in the acute and subacute stages, and the mRNA levels of Tet gene family members (Tet1, Tet2, and Tet3) were also increased. Administration of ascorbic acid (100 mg/kg) to SCI rats enhanced 5hmC levels; increased the expression of the Tet1, Tet2, and Tet3 genes within the brain motor cortex; promoted axonal sprouting within the lesion cavity of the spinal cord; and enhanced recovery of locomotor function until 12 weeks. In conclusion, we found that epigenetic status in the brain motor cortex is changed after SCI and that epigenetic modulation using ascorbic acid may contribute to functional recovery after SCI.

Role of Long Non-coding RNAs in Reprogramming to Induced Pluripotency

The generation of induced pluripotent stem cells through somatic cell reprogramming requires a global reorganization of cellular functions. This reorganization occurs in a multi-phased manner and involves a gradual revision of both the epigenome and transcriptome. Recent studies have shown that the large-scale transcriptional changes observed during reprogramming also apply to long non-coding RNAs (lncRNAs), a type of traditionally neglected RNA species that are increasingly viewed as critical regulators of cellular function. Deeper understanding of lncRNAs in reprogramming may not only help to improve this process but also have implications for studying cell plasticity in other contexts, such as development, aging, and cancer. In this review, we summarize the current progress made in profiling and analyzing the role of lncRNAs in various phases of somatic cell reprogramming, with emphasis on the re-establishment of the pluripotency gene network and X chromosome reactivation.

Roles of vitamins in stem cells

Stem cells can differentiate to diverse cell types in our body, and they hold great promises in both basic research and clinical therapies. For specific stem cell types, distinctive nutritional and signaling components are required to maintain the proliferation capacity and differentiation potential in cell culture. Various vitamins play essential roles in stem cell culture to modulate cell survival, proliferation and differentiation. Besides their common nutritional functions, specific vitamins are recently shown to modulate signal transduction and epigenetics. In this article, we will first review classical vitamin functions in both somatic and stem cell cultures. We will then focus on how stem cells could be modulated by vitamins beyond their nutritional roles. We believe that a better understanding of vitamin functions will significantly benefit stem cell research, and help realize their potentials in regenerative medicine.

Dietary natural products as epigenetic modifiers in aging-associated inflammation and disease

Covering: up to 2020Chronic, low-grade inflammation is linked to aging and has been termed "inflammaging". Inflammaging is considered a key contributor to the development of metabolic dysfunction and a broad spectrum of diseases or disorders including declines in brain and heart function. Genome-wide association studies (GWAS) coupled with epigenome-wide association studies (EWAS) have shown the importance of diet in the development of chronic and age-related diseases. Moreover, dietary interventions e.g. caloric restriction can attenuate inflammation to delay and/or prevent these diseases. Common themes in these studies entail the use of phytochemicals (plant-derived compounds) or the production of short chain fatty acids (SCFAs) as epigenetic modifiers of DNA and histone proteins. Epigenetic modifications are dynamically regulated and as such, serve as potential therapeutic targets for the treatment or prevention of age-related disease. In this review, we will focus on the role for natural products that include phytochemicals and short chain fatty acids (SCFAs) as regulators of these epigenetic adaptations. Specifically, we discuss regulators of methylation, acetylation and acylation, in the protection from chronic inflammation driven metabolic dysfunction and deterioration of neurocognitive and cardiac function.

Metabolic switch and epithelial-mesenchymal transition cooperate to regulate pluripotency

Both metabolic switch from oxidative phosphorylation to glycolysis (OGS) and epithelial-mesenchymal transition (EMT) promote cellular reprogramming at early stages. However, their connections have not been elucidated. Here, when a chemically defined medium was used to induce early EMT during mouse reprogramming, a facilitated OGS was also observed at the same time. Additional investigations suggested that the two events formed a positive feedback loop via transcriptional activation, cooperated to upregulate epigenetic factors such as Bmi1, Ctcf, Ezh2, Kdm2b, and Wdr5, and accelerated pluripotency induction at the early stage. However, at late stages, by over-inducing glycolysis and preventing the necessary mesenchymal-epithelial transition, the two events trapped the cells at a new pluripotency state between naïve and primed states and inhibited further reprogramming toward the naïve state. In addition, the pluripotent stem cells at the new state have high similarity to epiblasts from E4.5 and E5.5 embryos, and have distinct characteristics from the previously reported epiblast-like or formative states. Therefore, the time-dependent cooperation between OGS and EMT in regulating pluripotency should extend our understanding of related fields.

Dysregulation of the TET family of epigenetic regulators in lymphoid and myeloid malignancies

DNA methylation has pivotal regulatory roles in mammalian development, retrotransposon silencing, genomic imprinting, X-chromosome inactivation, and cancer. Cancer cells display highly dysregulated DNA methylation profiles, characterized by global hypomethylation in conjunction with hypermethylation of promoter CpG islands; these changes are often correlated with promoter hypermethylation, leading to decreased expression of tumor suppressor genes, as well as with genome instability, leading to amplification and aberrant expression of oncogenes. Ten-eleven-translocation (TET) proteins are α-ketoglutarate (α-KG)-dependent dioxygenases that oxidize 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) and the additional oxidation products 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC); together, these oxidized methylcytosines are intermediates in DNA demethylation. TET2 is frequently mutated in diverse lymphoid and myeloid cancers, and TET loss of function is often observed in the absence of coding region mutations in TET genes. Despite our understanding of the biochemical activities of TET proteins, how TET loss of function promotes the onset and progression of hematopoietic malignancies is largely unknown. Here, we review recent advances in our understanding of the role of TET enzymes in lymphoid and myeloid neoplasms and highlight the importance of metabolic alterations that decrease TET activity in cancer initiation and progression.

Application of the microRNA-302/367 cluster in cancer therapy

As a novel class of noncoding RNAs, microRNAs (miRNAs) can effectively silence their target genes at the posttranscriptional level. Various biological processes, such as cell proliferation, differentiation, and motility, are regulated by miRNAs. In different diseases and different stages of disease, miRNAs have various expression patterns, which makes them candidate prognostic markers and therapeutic targets. Abnormal miRNA expression has been detected in numerous neoplastic diseases in humans, which indicates the potential role of miRNAs in tumorigenesis. Previous studies have indicated that miRNAs are involved in nearly the entire process of tumor development. MicroRNA‐302a, miR‐302b, miR‐302c, miR‐302d, and miR‐367 are members of the miR‐302/367 cluster that plays various biological roles in diverse neoplastic diseases by targeting different genes. These miRNAs have been implicated in several unique characteristics of cancer, including the evasion of growth suppressors, the sustained activation of proliferative signaling, the evasion of cell death and senescence, and the regulation of angiogenesis, invasion, and metastasis. This review provides a critical overview of miR‐302/367 cluster dysregulation and the subsequent effects in cancer and highlights the vast potential of members of this cluster as therapeutic targets and novel biomarkers.

A comparative view on vitamin C effects on αβ- versus γδ T-cell activation and differentiation

Vitamin C (VitC) is an essential vitamin that needs to be provided through exogenous sources. It is a potent anti-oxidant, and an essential cofactor for many enzymes including a group of enzymes that modulate epigenetic regulation of gene expression. Moreover, VitC has a significant influence on T-cell differentiation, and can directly interfere with T-cell signaling. Conventional CD4 and CD8 T cells express the αβ TCR and recognize peptide antigens in the context of MHC presentation. The numerically small population of γδ T cells recognizes antigens in an MHC-independent manner. γδ T cells kill a broad variety of malignant cells, and because of their unique features, are interesting candidates for cancer immunotherapy. In this review, we summarize what is known about the influence of VitC on T-cell activation and differentiation with a special focus on γδ T cells. The known mechanisms of action of VitC on αβ T cells are discussed and extrapolated to the effects observed on γδ T-cell activation and differentiation. Overall, VitC enhances proliferation and effector functions of γδ T cells and thus may help to increase the efficacy of γδ T cells applied as cancer immunotherapy in adoptive cell transfer.

Mitochondrial dynamics and metabolism in induced pluripotency

Somatic cells can be reprogrammed to pluripotency by either ectopic expression of defined factors or exposure to chemical cocktails. During reprogramming, somatic cells undergo dramatic changes in a wide range of cellular processes, such as metabolism, mitochondrial morphology and function, cell signaling pathways or immortalization. Regulation of these processes during cell reprograming lead to the acquisition of a pluripotent state, which enables indefinite propagation by symmetrical self-renewal without losing the ability of reprogrammed cells to differentiate into all cell types of the adult. In this review, recent data from different laboratories showing how these processes are controlled during the phenotypic transformation of a somatic cell into a pluripotent stem cell will be discussed.

Nutritive vitamins as epidrugs

Epigenetic modifications play an important role in disease pathogenesis and therefore are a focus of intense investigation. Epigenetic changes include DNA, RNA, and histone modifications along with expression of non-coding RNAs. Various factors such as environment, diet, and lifestyle can influence the epigenome. Dietary nutrients like vitamins can regulate both physiological and pathological processes through their direct impact on epigenome. Vitamin A acts as a major regulator of above-mentioned epigenetic mechanisms. B group vitamins including biotin, niacin, and pantothenic acid also participate in modulation of various epigenome. Further, vitamin C has shown to modulate both DNA methylation and histone modifications while few reports have also supported its role in miRNA-mediated pathways. Similarly, vitamin D also influences various epigenetic modifications of both DNA and histone by controlling the regulatory mechanisms. Despite the information that vitamins can modulate the epigenome, the detailed mechanisms of vitamin-mediated epigenetic regulations have not been explored fully and hence further detailed studies are required to decipher their role at epigenome level in both normal and disease pathogenesis. The current review summarizes the available literature on the role of vitamins as epigenetic modifier and highlights the key evidences for developing vitamins as potential epidrugs.

Ascorbate and Iron Are Required for the Specification and Long-Term Self-Renewal of Human Skeletal Mesenchymal Stromal Cells

The effects of ascorbate on adult cell fate specification remain largely unknown. Using our stepwise and chemically defined system to derive lateral mesoderm progenitors from human pluripotent stem cells (hPSCs), we found that ascorbate increased the expression of mesenchymal stromal cell (MSC) markers, purity of MSCs, the long-term self-renewal and osteochondrogenic capacity of hPSC-MSCs in vitro. Moreover, ascorbate promoted MSC specification in an iron-dependent fashion, but not in a redox-dependent manner. Further studies revealed that iron synergized with ascorbate to regulate hPSC-MSC histone methylation, promote their long-term self-renewal, and increase their osteochondrogenic capacity. We found that one of the histone demethylases affected by ascorbate, KDM4B, was necessary to promote the specification of hPSC-MSCs. This mechanistic understanding led to the metabolic optimization of hPSC-MSCs with an extended lifespan in vitro and the ability to fully repair cartilage defects upon transplantation in vivo. Our results highlight the importance of ascorbate and iron metabolism in adult human cell fate specification.

•

Generation of hPSC-MSCs by stepwise and chemically defined protocol

•

Ascorbate promotes the specification and chondrogenesis of hPSC-MSCs

•

Ascorbate promotes the specification of hPS-MSCs and promotes osteochondrogenesis

•

hPSC-MSCs are able to fully repair the cartilage defects

Ascorbic Acid 2-Glucoside Stably Promotes the Primitiveness of Embryonic and Mesenchymal Stem Cells Through Ten-Eleven Translocation- and cAMP-Responsive Element-Binding Protein-1-Dependent Mechanisms

Aims: The naive or primitive states of stem cells (SCs) residing in specific niches are unstable and difficult to preserve in vitro. Vitamin C (VitC), in addition to suppressing oxygen radicals, exerts pleiotropic effects to preserve the core functions of SCs. However, this compound is labile and readily oxidized, resulting in cellular toxicity and preventing its reliable application in this context. We found that a VitC derivative, ascorbic acid 2-glucoside (AA2G), stably maintains the naive pluripotency of murine embryonic SCs (mESCs) and the primitiveness of human mesenchymal SCs (hMSCs) without cellular toxicity. Results: The beneficial effects of AA2G and related molecular mechanisms were evaluated in mESCs, induced pluripotent-SCs (iPSCs), and hMSCs. AA2G was stable in aqueous solution and barely induced cellular toxicity in cultured SCs, unlike VitC. AA2G supplementation recapitulated the well-known effects of VitC, including induction of ten-eleven translocation-dependent DNA demethylation in mESCs and suppression of p53 during generation of murine iPSCs. Furthermore, supplementation of hMSCs with AA2G improved therapeutic outcomes in an asthma mouse model by promoting their self-renewal, engraftment, and anti-inflammatory properties. Particularly, activation of the cAMP-responsive element-binding protein-1 (CREB1) pathway contributed to the ability of AA2G to maintain naive pluripotency of mESCs and functionality of hMSCs. Innovation and Conclusion: Given its long-lasting effects and low cellular toxicity, AA2G supplementation is useful to support the naive pluripotency of mESCs and the primitiveness of hMSCs, affecting their developmental potency and therapeutic efficacy. Furthermore, we demonstrate the significance of the CREB1 pathway in the mechanism of action of AA2G.

Vitamin C treatment of embryos, but not donor cells, improves the cloned embryonic development in sheep

Vitamin C is not only an antioxidant but also a regulator of epigenetic modifications that can enhance the activity of the ten-eleven translocation (TET) family dioxygenases and promote the oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). Here, we investigated the effects of vitamin C in regulating DNA methylation in sheep somatic cells or embryos in an effort to improve the cloned embryo development. Vitamin C treatment of sheep foetal fibroblast cells significantly increased the 5hmC levels but did not affect the 5mC levels in cells. After nuclear transfer, vitamin C-treated donor cells could not support a higher blastocyst development rate than non-treated cells. Although combination of serum starvation and vitamin C treatment could induce significant 5mC decrease in donor cells, it failed to promote the development of resultant cloned embryos. When cloned embryos were directly treated with vitamin C, the pre-implantation development of embryos and the 5hmC levels in blastocysts were significantly improved. This beneficial role of vitamin C on embryo development was also observed in fertilized embryos. Our results suggest that vitamin C treatment of the embryos, but not the donor cells, can improve the development of cloned sheep embryos.

Pro- and Antioxidant Effects of Vitamin C in Cancer in correspondence to Its Dietary and Pharmacological Concentrations

Vitamin C is an antioxidant that may scavenge reactive oxygen species preventing DNA damage and other effects important in cancer transformation. Dietary vitamin C from natural sources is taken with other compounds affecting its bioavailability and biological effects. High pharmacological doses of vitamin C may induce prooxidant effects, detrimental for cancer cells. An oxidized form of vitamin C, dehydroascorbate, is transported through glucose transporters, and cancer cells switch from oxidative phosphorylation to glycolysis in energy production so an excess of vitamin C may limit glucose transport and ATP production resulting in energetic crisis and cell death. Vitamin C may change the metabolomic and epigenetic profiles of cancer cells, and activation of ten-eleven translocation (TET) proteins and downregulation of pluripotency factors by the vitamin may eradicate cancer stem cells. Metastasis, the main reason of cancer-related deaths, requires breakage of anatomical barriers containing collagen, whose synthesis is promoted by vitamin C. Vitamin C induces degradation of hypoxia-inducible factor, HIF-1, essential for the survival of tumor cells in hypoxic conditions. Dietary vitamin C may stimulate the immune system through activation of NK and T cells and monocytes. Pharmacological doses of vitamin C may inhibit cancer transformation in several pathways, but further studies are needed to address both mechanistic and clinical aspects of this effect.

Recent advances of induced pluripotent stem cells application in neurodegenerative diseases

Stem cell is defined by its ability to self-renewal and generates differentiated functional cell types, which are derived from the embryo and various sources of postnatal animal. These cells can be divided according to their potential development into totipotent, unipotent, multipotent andpluripotent. Pluripotent is considered as the most important type due to its advantageous capability to create different cell types of the body in a similar behavior as embryonic stem cell. Induced pluripotent stem cells (iPSCs) are adult cells that maintain the characteristics of embryonic stem cells because it can be genetically reprogrammed to an embryonic stem cell-like state via express genes and transcription factors. Such cells provide an efficient pathway to explorehuman diseases and their corresponding therapy, particularly, neurodevelopmental disorders. Consequently, iPSCs can be investigated to check the specific mutations of neurodegenerative disease due to their unique ability to differentiate into neural cell types and/or neural organoids. The current review addresses the different neurodegenerative diseases model by using iPSCs approach such as Alzheimer's diseases (AD), Parkinson diseases (PD),multiplesclerosis(MS) and psychiatric disorders. We also highlight the importance of autophagy in neurodegenerative diseases.

Reprogramming: identifying the mechanisms that safeguard cell identity

Development and homeostasis rely upon concerted regulatory pathways to establish the specialized cell types needed for tissue function. Once a cell type is specified, the processes that restrict and maintain cell fate are equally important in ensuring tissue integrity. Over the past decade, several approaches to experimentally reprogram cell fate have emerged. Importantly, efforts to improve and understand these approaches have uncovered novel molecular determinants that reinforce lineage commitment and help resist cell fate changes. In this Review, we summarize recent studies that have provided insights into the various chromatin factors, post-transcriptional processes and features of genomic organization that safeguard cell identity in the context of reprogramming to pluripotency. We also highlight how these factors function in other experimental, physiological and pathological cell fate transitions, including direct lineage conversion, pluripotency-to-totipotency reversion and cancer.

Differential regulation of OCT4 targets facilitates reacquisition of pluripotency

Ectopic transcription factor expression enables reprogramming of somatic cells to pluripotency, albeit with generally low efficiency. Despite steady progress in the field, the exact molecular mechanisms that coordinate this remarkable transition still remain largely elusive. To better characterize the final steps of pluripotency induction, we optimized an experimental system where pluripotent stem cells are differentiated for set intervals before being reintroduced to pluripotency-supporting conditions. Using this approach, we identify a transient period of high-efficiency reprogramming where ectopic transcription factors, but not serum/LIF alone, rapidly revert cells to pluripotency with near 100% efficiency. After this period, cells reprogram with somatic-like kinetics and efficiencies. We identify a set of OCT4 bound cis-regulatory elements that are dynamically regulated during this transient phase and appear central to facilitating reprogramming. Interestingly, these regions remain hypomethylated during in vitro and in vivo differentiation, which may allow them to act as primary targets of ectopically induced factors during somatic cell reprogramming.

KDM2A/B lysine demethylases and their alternative isoforms in development and disease

Aberrant levels of histone modifications lead to chromatin malfunctioning and consequently to various developmental defects and human diseases. Therefore, the proteins bearing the ability to modify histones have been extensively studied and the molecular mechanisms of their action are now fairly well understood. However, little attention has been paid to naturally occurring alternative isoforms of chromatin modifying proteins and to their biological roles. In this review, we focus on mammalian KDM2A and KDM2B, the only two lysine demethylases whose genes have been described to produce also an alternative isoform lacking the N-terminal demethylase domain. These short KDM2A/B-SF isoforms arise through alternative promoter usage and seem to play important roles in development and disease. We hypothesise about the biological significance of these alternative isoforms, which might represent a more common evolutionarily conserved regulatory mechanism.

Antioxidant Regulation of Cell Reprogramming

Discovery of induced pluripotent stem cells (iPSCs) has revolutionized regeneration biology, providing further mechanistic insights and possible therapeutic applications. The original discovery by Yamanaka and co-workers showed that the expression of four transcription factors in fibroblasts resulted in the generation of iPSCs that can be differentiated into various cell types. This technology should be particularly useful for restoring cells with limited proliferative capacities such as adult heart muscle cells and neurons, in order to treat diseases affecting these cell types. More recently, iPSCs-mediated cell reprogramming has advanced to new technologies including direct reprogramming and pharmacological reprogramming. Direct reprogramming allows for the conversion of fibroblasts into cardiomyocytes, neurons or other cells by expressing multiple cell type-specific transcription factors without going through the production of iPSCs. Both iPSC-mediated reprogramming as well as direct reprogramming can also be promoted by a combination of small molecules, opening up a possibility for pharmacological therapies to induce cell reprogramming. However, all of these processes have been shown to be affected by reactive oxygen species that reduce the efficacies of reprogramming fibroblasts into iPSCs, differentiating iPSCs into target cells, as well as direct reprogramming. Accordingly, antioxidants have been shown to support these reprogramming processes and this review article summarizes these findings. It should be noted however, that the actions of antioxidants to support cell reprogramming may be through their ROS inhibiting abilities, but could also be due to mechanisms that are independent of classical antioxidant actions.

Metabolic-Epigenetic Axis in Pluripotent State Transitions

Cell state transition (CST) occurs during embryo development and in adult life in response to different stimuli and is associated with extensive epigenetic remodeling. Beyond growth factors and signaling pathways, increasing evidence point to a crucial role of metabolic signals in this process. Indeed, since several epigenetic enzymes are sensitive to availability of specific metabolites, fluctuations in their levels may induce the epigenetic changes associated with CST. Here we analyze how fluctuations in metabolites availability influence DNA/chromatin modifications associated with pluripotent stem cell (PSC) transitions. We discuss current studies and focus on the effects of metabolites in the context of naïve to primed transition, PSC differentiation and reprogramming of somatic cells to induced pluripotent stem cells (iPSCs), analyzing their mechanism of action and the causal correlation between metabolites availability and epigenetic alteration.

Reprogramming the Epigenome With Vitamin C

The erasure of epigenetic modifications across the genome of somatic cells is an essential requirement during their reprogramming into induced pluripotent stem cells (iPSCs). Vitamin C plays a pivotal role in remodeling the epigenome by enhancing the activity of Jumonji-C domain-containing histone demethylases (JHDMs) and the ten-eleven translocation (TET) proteins. By maintaining differentiation plasticity in culture, vitamin C also improves the quality of tissue specific stem cells derived from iPSCs that are highly sought after for use in regenerative medicine. The ability of vitamin C to potentiate the activity of histone and DNA demethylating enzymes also has clinical application in the treatment of cancer. Vitamin C deficiency has been widely reported in cancer patients and has recently been shown to accelerate cancer progression in disease models. Therapies involving high-dose vitamin C administration are currently gaining traction in the treatment of epigenetic dysregulation, by targeting aberrant histone and DNA methylation patterns associated with cancer progression.

Modeling blood diseases with human induced pluripotent stem cells

Induced pluripotent stem cells (iPSCs) are derived from somatic cells through a reprogramming process, which converts them to a pluripotent state, akin to that of embryonic stem cells. Over the past decade, iPSC models have found increasing applications in the study of human diseases, with blood disorders featuring prominently. Here, we discuss methodological aspects pertaining to iPSC generation, hematopoietic differentiation and gene editing, and provide an overview of uses of iPSCs in modeling the cell and gene therapy of inherited genetic blood disorders, as well as their more recent use as models of myeloid malignancies. We also discuss the strengths and limitations of iPSCs compared to model organisms and other cellular systems commonly used in hematology research.

Transcriptome Analyses Reveal Effects of Vitamin C-Treated Donor Cells on Cloned Bovine Embryo Development

Somatic cell nuclear transfer (SCNT) is a very powerful technique used to produce genetically identical or modified animals. However, the cloning efficiency in mammals remains low. In this study, we aimed to explore the effects of vitamin C (Vc)-treated donor cells on cloned embryos. As a result, Vc treatment relaxed the chromatin of donor cells and improved cloned embryo development. RNA sequencing was adopted to investigate the changes in the transcriptional profiles in early embryos. We found that Vc treatment increased the expression of genes involved in the cell–substrate adherens junction. Gene ontology (GO) analysis revealed that Vc treatment facilitated the activation of autophagy, which was deficient in cloned two-cell embryos. Rapamycin, an effective autophagy activator, increased the formation of cloned blastocysts (36.0% vs. 25.6%, p < 0.05). Abnormal expression of some coding genes and long non-coding RNAs in cloned embryos was restored by Vc treatment, including the zinc-finger protein 641 (ZNF641). ZNF641 compensation by means of mRNA microinjection improved the developmental potential of cloned embryos. Moreover, Vc treatment rescued some deficient RNA-editing sites in cloned two-cell embryos. Collectively, Vc-treated donor cells improved the development of the cloned embryo by affecting embryonic transcription. This study provided useful resources for future work to promote the reprogramming process in SCNT embryos.

Prenatal epigenetics diets play protective roles against environmental pollution

It is thought that germ cells and preimplantation embryos during development are most susceptible to endogenous and exogenous environmental factors because the epigenome in those cells is undergoing dramatic elimination and reconstruction. Exposure to environmental factors such as nutrition, climate, stress, pathogens, toxins, and even social behavior during gametogenesis and early embryogenesis has been shown to influence disease susceptibility in the offspring. Early-life epigenetic modifications, which determine the expression of genetic information stored in the genome, are viewed as one of the general mechanisms linking prenatal exposure and phenotypic changes later in life. From atmospheric pollution, endocrine-disrupting chemicals to heavy metals, research increasingly suggests that environmental pollutions have already produced significant consequences on human health. Moreover, mounting evidence now links such pollution to relevant modification in the epigenome. The epigenetics diet, referring to a class of bioactive dietary compounds such as isothiocyanates in broccoli, genistein in soybean, resveratrol in grape, epigallocatechin-3-gallate in green tea, and ascorbic acid in fruits, has been shown to modify the epigenome leading to beneficial health outcomes. This review will primarily focus on the causes and consequences of prenatal environment pollution exposure on the epigenome, and the potential protective role of the epigenetics diet, which could play a central role in neutralizing epigenomic aberrations against environmental pollutions.

Collagen Prolyl Hydroxylation-Dependent Metabolic Perturbation Governs Epigenetic Remodeling and Mesenchymal Transition in Pluripotent and Cancer Cells

Collagen prolyl hydroxylation (CPH), which is catalyzed by prolyl 4-hydroxylase (P4H), is the most prevalent posttranslational modification in humans and requires vitamin C (VitC). Here, we demonstrate that CPH acts as an epigenetic modulator of cell plasticity. Increased CPH induced global DNA/histone methylation in pluripotent stem and tumor cells and promoted cell state transition (CST). Interfering with CPH by either genetic ablation of P4H subunit alpha-2 (P4HA2) or pharmacologic treatment reverted epigenetic changes and antagonized CST. Mechanistically, we suggest that CPH modifies the epigenetic landscape by reducing VitC for DNA and histone demethylases. Repurposed drugs targeting CPH-mediated metabolic perturbation, such as the antiasthmatic budesonide, blocked metastatic dissemination of breast cancer cells in vivo by preventing mesenchymal transition. Our study provides mechanistic insights into how metabolic cues and epigenetic factors integrate to control CST and paves the way for the development of novel antimetastatic strategies. SIGNIFICANCE: A phenotype-based high-throughput screening reveals unforeseen metabolic control of cell plasticity and identifies budesonide as a drug candidate for metastatic cancer.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/13/3235/F1.large.jpg.

Metabolism Is a Key Regulator of Induced Pluripotent Stem Cell Reprogramming

Reprogramming to pluripotency involves drastic restructuring of both metabolism and the epigenome. However, induced pluripotent stem cells (iPSC) retain transcriptional memory, epigenetic memory, and metabolic memory from their somatic cells of origin and acquire aberrant characteristics distinct from either other pluripotent cells or parental cells, reflecting incomplete reprogramming. As a critical link between the microenvironment and regulation of the epigenome, nutrient availability likely plays a significant role in the retention of somatic cell memory by iPSC. Significantly, relative nutrient availability impacts iPSC reprogramming efficiency, epigenetic regulation and cell fate, and differentially alters their ability to respond to physiological stimuli. The significance of metabolites during the reprogramming process is central to further elucidating how iPSC retain somatic cell characteristics and optimising culture conditions to generate iPSC with physiological phenotypes to ensure their reliable use in basic research and clinical applications. This review serves to integrate studies on iPSC reprogramming, memory retention and metabolism, and identifies areas in which current knowledge is limited.

Ascorbic Acid Facilitates Neural Regeneration After Sciatic Nerve Crush Injury

Ascorbic acid (AA) is an essential micronutrient that has been safely used in the clinic for many years. The present study indicates that AA has an unexpected function in facilitating nerve regeneration. Using a mouse model of sciatic nerve crush injury, we found that AA can significantly accelerate axonal regrowth in the early stage [3 days post-injury (dpi)], a finding that was revealed by immunostaining and Western blotting for antibodies against GAP-43 and SCG10. On day 28 post-injury, histomorphometric assessments demonstrated that AA treatment increased the density, size, and remyelination of regenerated axons in the injured nerve and alleviated myoatrophy in the gastrocnemius. Moreover, the results from various behavioral tests and electrophysiological assays revealed that nerve injury-derived functional defects in motor and sensory behavior as well as in nerve conduction were significantly attenuated by treatment with AA. The potential mechanisms of AA in nerve regeneration were further explored by investigating the effects of AA on three types of cells involved in this process [neurons, Schwann cells (SCs) and macrophages] through a series of experiments. Overall, the data illustrated that AA treatment in cultured dorsal root ganglionic neurons resulted in increased neurite growth and lower expression of RhoA, which is an important inhibitory factor in neural regeneration. In SCs, proliferation, phagocytosis, and neurotrophin expression were all enhanced by AA. Meanwhile, AA treatment also improved proliferation, migration, phagocytosis, and anti-inflammatory polarization in macrophages. In conclusion, this study demonstrated that treatment with AA can promote the morphological and functional recovery of injured peripheral nerves and that this effect is potentially due to AA’s bioeffects on neurons, SCs and macrophages, three of most important types of cells involved in nerve injury and regeneration.

Biology and targeting of the Jumonji-domain histone demethylase family in childhood neoplasia: a preclinical overview

INTRODUCTION

Epigenetic mechanisms of gene regulatory control play fundamental roles in developmental morphogenesis, and, as more recently appreciated, are heavily implicated in the onset and progression of neoplastic disease, including cancer. Many epigenetic mechanisms are therapeutically targetable, providing additional incentive for understanding of their contribution to cancer and other types of neoplasia. Areas covered: The Jumonji-domain histone demethylase (JHDM) family exemplifies many of the above traits. This review summarizes the current state of knowledge of the functions and pharmacologic targeting of JHDMs in cancer and other neoplastic processes, with an emphasis on diseases affecting the pediatric population. Expert opinion: To date, the JHDM family has largely been studied in the context of normal development and adult cancers. In contrast, comparatively few studies have addressed JHDM biology in cancer and other neoplastic diseases of childhood, especially solid (non-hematopoietic) neoplasms. Encouragingly, the few available examples support important roles for JHDMs in pediatric neoplasia, as well as potential roles for JHDM pharmacologic inhibition in disease management. Further investigations of JHDMs in cancer and other types of neoplasia of childhood can be expected to both enlighten disease biology and inform new approaches to improve disease outcomes.

Approaches towards Longevity: Reprogramming, Senolysis, and Improved Mitotic Competence as Anti-Aging Therapies

Mainstream approaches that are currently used as anti-aging therapies primarily explore the senescence and epigenetic drift aging hallmarks and they are at two ends of the spectrum. While senolytic therapies include either the selective elimination of senescent cells or the disruption of their secretome with the use of drugs or natural compounds, cellular reprogramming uses genetic manipulation to revert cells all the way back to pluripotency. Here, we describe the progress that has been made on these therapies, while highlighting the major challenges involved. Moreover, based on recent findings elucidating the impact of mitotic shutdown and aneuploidy in cellular senescence, we discuss the modulation of mitotic competence as an alternative strategy to delay the hallmarks of aging. We propose that a regulated rise in mitotic competence of cells could circumvent certain limitations that are present in the senolytic and reprogramming approaches, by acting to decelerate senescence and possibly restore the epigenetic landscape.

Induced Pluripotent Stem Cells and Their Use in Human Models of Disease and Development

The discovery of somatic cell nuclear transfer proved that somatic cells can carry the same genetic code as the zygote, and that activating parts of this code are sufficient to reprogram the cell to an early developmental state. The discovery of induced pluripotent stem cells (iPSCs) nearly half a century later provided a molecular mechanism for the reprogramming. The initial creation of iPSCs was accomplished by the ectopic expression of four specific genes (OCT4, KLF4, SOX2, and c-Myc; OSKM). iPSCs have since been acquired from a wide range of cell types and a wide range of species, suggesting a universal molecular mechanism. Furthermore, cells have been reprogrammed to iPSCs using a myriad of methods, although OSKM remains the gold standard. The sources for iPSCs are abundant compared with those for other pluripotent stem cells; thus the use of iPSCs to model the development of tissues, organs, and other systems of the body is increasing. iPSCs also, through the reprogramming of patient samples, are being used to model diseases. Moreover, in the 10 years since the first report, human iPSCs are already the basis for new cell therapies and drug discovery that have reached clinical application. In this review, we examine the generation of iPSCs and their application to disease and development.

Dynamic regulation of epigenetic demethylation by oxygen availability and cellular redox

The chromatin structure of the mammalian genome must facilitate both precisely-controlled DNA replication together with tightly-regulated gene transcription. This necessarily involves complex mechanisms and processes which remain poorly understood. It has long been recognised that the epigenetic landscape becomes established during embryonic development and acts to specify and determine cell fate. In addition, the chromatin structure is highly dynamic and allows for both cellular reprogramming and homeostatic modulation of cell function. In this respect, the functions of epigenetic "erasers", which act to remove covalently-linked epigenetic modifications from DNA and histones are critical. The enzymatic activities of the TET and JmjC protein families have been identified as demethylases which act to remove methyl groups from DNA and histones, respectively. Further, they are characterised as members of the Fe(II)- and 2-oxoglutarate-dependent dioxygenase superfamily. This provides the intriguing possibility that their enzymatic activities may be modulated by cellular metabolism, oxygen availability and redox-based mechanisms, all of which are likely to display dynamic cell- and tissue-specific patterns of flux. Here we discuss the current evidence for such [O₂]- and redox-dependent regulation of the TET and Jmjc demethylases and the potential physiological and pathophysiological functional consequences of such regulation.

Conserved regulation of RNA processing in somatic cell reprogramming

BACKGROUND

Along with the reorganization of epigenetic and transcriptional networks, somatic cell reprogramming brings about numerous changes at the level of RNA processing. These include the expression of specific transcript isoforms and 3' untranslated regions. A number of studies have uncovered RNA processing factors that modulate the efficiency of the reprogramming process. However, a comprehensive evaluation of the involvement of RNA processing factors in the reprogramming of somatic mammalian cells is lacking.

RESULTS

Here, we used data from a large number of studies carried out in three mammalian species, mouse, chimpanzee and human, to uncover consistent changes in gene expression upon reprogramming of somatic cells. We found that a core set of nine splicing factors have consistent changes across the majority of data sets in all three species. Most striking among these are ESRP1 and ESRP2, which accelerate and enhance the efficiency of somatic cell reprogramming by promoting isoform expression changes associated with mesenchymal-to-epithelial transition. We further identify genes and processes in which splicing changes are observed in both human and mouse.

CONCLUSIONS

Our results provide a general resource for gene expression and splicing changes that take place during somatic cell reprogramming. Furthermore, they support the concept that splicing factors with evolutionarily conserved, cell type-specific expression can modulate the efficiency of the process by reinforcing intermediate states resembling the cell types in which these factors are normally expressed.

Sufficiency of hypoxia-inducible 2-oxoglutarate dioxygenases to block chemical oxidative stress-induced differentiation of human embryonic stem cells

Hypoxia benefits undifferentiated pluripotent stem cell renewal, and 2-oxoglutarate (2OG) dioxygenases have been implicated in pluripotent stem cell induction and renewal. We show in human embryonic stem cells (hESC) that an ambient oxygen-induced oxidative stress response elicited by culture in a hypoxic atmosphere (0.5% O₂) correlates with the expression of 2OG dioxygenases, which oxidise DNA (TET1, 2, 3) and histone H3 (KDM4C), the former reflected by elevation in genomic 5-hydroxymethylcytosine (5hmC). siRNA-mediated targeting of KDM4C and TET1-3 induces hESC differentiation. Under ambient atmospheric oxygen (21% O₂), exposure to a low inhibitory concentration of sodium arsenite (NaAsO₂, IC₁₀), as a model of chemically-induced oxidative stress, suppresses antioxidant gene expression, reduces mitochondrial membrane potential and induces hESC differentiation. Co-administration of the antioxidant N-acetyl-L-cysteine promoted anti-oxidant, pluripotency and 2OG dioxygenase gene expression, elevated genomic hydroxymethylation and blocked induction of differentiation. Transient ectopic expression of KDM4C or TET1 in ambient atmospheric oxygen achieved the same. Our study substantiates a role for 2OG-dependent dioxygenases in hypoxia's promotion of undifferentiated hESC self-renewal.

Short-Term Mitochondrial Permeability Transition Pore Opening Modulates Histone Lysine Methylation at the Early Phase of Somatic Cell Reprogramming

Reprogramming of somatic cells to induced pluripotent stem cells reconfigures chromatin modifications. Whether and how this process is regulated by signals originating in the mitochondria remain unknown. Here we show that the mitochondrial permeability transition pore (mPTP), a key regulator of mitochondrial homeostasis, undergoes short-term opening during the early phase of reprogramming and that this transient activation enhances reprogramming. In mouse embryonic fibroblasts, greater mPTP opening correlates with higher reprogramming efficiency. The reprogramming-promoting function of mPTP opening is mediated by plant homeodomain finger protein 8 (PHF8) demethylation of H3K9me2 and H3K27me3, leading to reduction in their occupancies at the promoter regions of pluripotency genes. mPTP opening increases PHF8 protein levels downstream of mitochondrial reactive oxygen species production and miR-101c and simultaneously elevates levels of PHF8's cofactor, α-ketoglutarate. Our findings represent a novel mitochondria-to-nucleus pathway in cell fate determination by mPTP-mediated epigenetic regulation.

Ascorbic Acid in Cancer Treatment: Let the Phoenix Fly

Vitamin C (ascorbic acid, ascorbate), despite controversy, has re-emerged as a promising anti-cancer agent. Recent knowledge of intravenous ascorbate pharmacokinetics and discovery of unexpected mechanisms of ascorbate action have spawned many investigations. Two mechanisms of anti-cancer activity with ascorbate have gained prominence: hydrogen peroxide-induced oxidative stress and DNA demethylation mediated by ten-eleven translocation enzyme activation. Here, we highlight salient aspects of the evolution of ascorbate in cancer treatment, provide insights into the pharmacokinetics of ascorbate, describe mechanisms of its anti-cancer activity in relation to the pharmacokinetics, outline promising preclinical and clinical evidence, and recommend future directions.

Vitamin C counteracts miR-302/367-induced reprogramming of human breast cancer cells and restores their invasive and proliferative capacity

Epigenetic reprogramming by embryonic stem cell-specific miR-302/367 cluster has shown some tumor suppressive effects in cancer cells of different tissues such as skin, colon, and cervix. Vitamin C has been known as a reprogramming enhancer of human and mouse somatic cells. In this study, first we aimed to investigate whether exogenous induction of miR-302/367 in breast cancer cells shows the same tumor suppressive effects previously observed in other cancer cells lines, and whether vitamin C can enhance reprogramming of breast cancer cells and also improve the tumor suppressive function of miR-302/367 cluster. Overexpression of miR-302/367 cluster in MDA-MB-231 and SK-BR-3 breast cancer cells upregulated expression of miR-302/367 members and also some core pluripotency factors including OCT4A, SOX2 and NANOG, induced mesenchymal to epithelial transition, suppressed invasion, proliferation, and induced apoptosis in the both cell lines. However, treatment of the miR-302/367 transfected cells with vitamin C suppressed the expression of pluripotency factors and augmented the tumorigenicity of the breast cancer cells by restoring their proliferative and invasive capacity and compromising the apoptotic effect of miR-302/367. Supplementing the culture medium with vitamin C downregulated expression of TET1 gene which seems to be the reason behind the negative impact of vitamin C on the reprogramming efficiency of miR-302/367 cluster and its anti-tumor effects. Therefore application of vitamin C may not always serve as a reprogramming enhancer depending on its switching function on TET1. This phenomenon should be carefully considered when considering a reprogramming strategy for tumor suppression.

The role of α-ketoglutarate-dependent proteins in pluripotency acquisition and maintenance

α-Ketoglutarate is an important metabolic intermediate that acts as a cofactor for several chromatin-modifying enzymes, including histone demethylases and the Tet family of enzymes that are involved in DNA demethylation. In this review, we focus on the function and genomic localization of these α-ketoglutarate-dependent enzymes in the maintenance of pluripotency during cellular reprogramming to induced pluripotent stem cells and in disruption of pluripotency during in vitro differentiation. The enzymatic function of many of these α-ketoglutarate-dependent proteins is required for pluripotency acquisition and maintenance. A better understanding of their specific function will be essential in furthering our knowledge of pluripotency.

Vitamin C in Stem Cell Reprogramming and Cancer

Vitamin C is an essential dietary requirement for humans. In addition to its known role as an antioxidant, vitamin C is a cofactor for Fe²⁺- and α-ketoglutarate-dependent dioxygenases (Fe²⁺/α-KGDDs) which comprise a large number of diverse enzymes, including collagen prolyl hydroxylases and epigenetic regulators of histone and DNA methylation. Vitamin C can modulate embryonic stem cell (ESC) function, enhance reprogramming of fibroblasts to induced pluripotent stem cells (iPSCs), and hinder the aberrant self-renewal of hematopoietic stem cells (HSCs) through its ability to enhance the activity of either Jumonji C (JmjC) domain-containing histone demethylases or ten-eleven translocation (TET) DNA hydroxylases. Given that epigenetic dysregulation is a known driver of malignancy, vitamin C may play a novel role as an epigenetic anticancer agent.

Intravenous Vitamin C for Cancer Therapy - Identifying the Current Gaps in Our Knowledge

The use of intravenous vitamin C (IVC) for cancer therapy has long been an area of intense controversy. Despite this, high dose IVC has been administered for decades by complementary health care practitioners and physicians, with little evidence base resulting in inconsistent clinical practice. In this review we pose a series of questions of relevance to both researchers and clinicians, and also patients themselves, in order to identify current gaps in our knowledge. These questions include: Do oncology patients have compromised vitamin C status? Is intravenous the optimal route of vitamin C administration? Is IVC safe? Does IVC interfere with chemotherapy or radiotherapy? Does IVC decrease the toxic side effects of chemotherapy and improve quality of life? What are the relevant mechanisms of action of IVC? What are the optimal doses, frequency, and duration of IVC therapy? Researchers have made massive strides over the last 20 years and have addressed many of these important aspects, such as the best route for administration, safety, interactions with chemotherapy, quality of life, and potential mechanisms of action. However, we still do not know the answers to a number of fundamental questions around best clinical practice, such as how much, how often and for how long to administer IVC to oncology patients. These questions point the way forward for both basic research and future clinical trials.

KDM2B is a histone H3K79 demethylase and induces transcriptional repression via sirtuin-1-mediated chromatin silencing

The methylation of histone H3 lysine 79 (H3K79) is an active chromatin marker and is prominent in actively transcribed regions of the genome; however, demethylase of H3K79 remains unknown despite intensive research. Here, we show that KDM2B, also known as FBXL10 and a member of the Jumonji C family of proteins known for its histone H3K36 demethylase activity, is a di- and trimethyl H3K79 demethylase. We demonstrate that KDM2B induces transcriptional repression of HOXA7 and MEIS1 via occupancy of promoters and demethylation of H3K79. Furthermore, genome-wide analysis suggests that H3K79 methylation levels increase when KDM2B is depleted, which indicates that KDM2B functions as an H3K79 demethylase in vivo. Finally, stable KDM2B-knockdown cell lines exhibit displacement of NAD⁺-dependent deacetylase sirtuin-1 (SIRT1) from chromatin, with concomitant increases in H3K79 methylation and H4K16 acetylation. Our findings identify KDM2B as an H3K79 demethylase and link its function to transcriptional repression via SIRT1-mediated chromatin silencing.-Kang, J.-Y., Kim, J.-Y., Kim, K.-B., Park, J. W., Cho, H., Hahm, J. Y., Chae, Y.-C., Kim, D., Kook, H., Rhee, S., Ha, N.-C., Seo, S.-B. KDM2B is a histone H3K79 demethylase and induces transcriptional repression via sirtuin-1-mediated chromatin silencing.

Ten years of progress and promise of induced pluripotent stem cells: historical origins, characteristics, mechanisms, limitations, and potential applications

The discovery of induced pluripotent stem cells (iPSCs) by Shinya Yamanaka in 2006 was heralded as a major breakthrough of the decade in stem cell research. The ability to reprogram human somatic cells to a pluripotent embryonic stem cell-like state through the ectopic expression of a combination of embryonic transcription factors was greeted with great excitement by scientists and bioethicists. The reprogramming technology offers the opportunity to generate patient-specific stem cells for modeling human diseases, drug development and screening, and individualized regenerative cell therapy. However, fundamental questions have been raised regarding the molecular mechanism of iPSCs generation, a process still poorly understood by scientists. The efficiency of reprogramming of iPSCs remains low due to the effect of various barriers to reprogramming. There is also the risk of chromosomal instability and oncogenic transformation associated with the use of viral vectors, such as retrovirus and lentivirus, which deliver the reprogramming transcription factors by integration in the host cell genome. These challenges can hinder the therapeutic prospects and promise of iPSCs and their clinical applications. Consequently, extensive studies have been done to elucidate the molecular mechanism of reprogramming and novel strategies have been identified which help to improve the efficiency of reprogramming methods and overcome the safety concerns linked with iPSC generation. Distinct barriers and enhancers of reprogramming have been elucidated, and non-integrating reprogramming methods have been reported. Here, we summarize the progress and the recent advances that have been made over the last 10 years in the iPSC field, with emphasis on the molecular mechanism of reprogramming, strategies to improve the efficiency of reprogramming, characteristics and limitations of iPSCs, and the progress made in the applications of iPSCs in the field of disease modelling, drug discovery and regenerative medicine. Additionally, this study appraises the role of genomic editing technology in the generation of healthy iPSCs.

Ascorbic acid promotes a TGFβ1-induced myofibroblast phenotype switch

l‐Ascorbic acid (AA), generally known as vitamin C, is a crucial cofactor for a variety of enzymes, including prolyl‐3‐hydroxylase (P3H), prolyl‐4‐hydroxylase (P4H), and lysyl hydroxylase (LH)‐mediated collagen maturation. Here, we investigated whether AA has additional functions in the regulation of the myofibroblast phenotype, besides its function in collagen biosynthesis. We found that AA positively influences TGFβ1‐induced expression of COL1A1,ACTA2, and COL4A1. Moreover, we demonstrated that AA promotes αSMA stress fiber formation as well as the synthesis and deposition of collagens type I and IV. Additionally, AA amplified the contractile phenotype of the myofibroblasts, as seen by increased contraction of a 3D collagen lattice. Moreover, AA increased the expression of several TGFβ1‐induced genes, including DDR1 and CCN2. Finally, we demonstrated that the mechanism of AA action seems independent of Smad2/3 signaling.

Implications of Epigenetic Mechanisms and their Targets in Cerebral Ischemia Models

BACKGROUND

Understanding the complexities associated with the ischemic condition and identifying therapeutic targets in ischemia is a continued challenge in stroke biology. Emerging evidence reveals the potential involvement of epigenetic mechanisms in the incident and outcome of stroke, suggesting novel therapeutic options of targeting different molecules related to epigenetic regulation.

OBJECTIVE

This review summarizes our current understanding of ischemic pathophysiology, describes various in vivo and in vitro models of ischemia, and examines epigenetic modifications associated with the ischemic condition.

METHOD

We focus on microRNAs, DNA methylation, and histone modifying enzymes, and present how epigenetic studies are revealing novel drug target candidates in stroke.

CONCLUSION

Finally, we discuss emerging approaches for the prevention and treatment of stroke and post-stroke effects using pharmacological interventions with a wide therapeutic window.

Ascorbic acid induces global epigenetic reprogramming to promote meiotic maturation and developmental competence of porcine oocytes

L-ascorbic acid (Vitamin C) can enhance the meiotic maturation and developmental competence of porcine oocytes, but the underlying molecular mechanism remains obscure. Here we show the role of ascorbic acid in regulating epigenetic status of both nucleic acids and chromatin to promote oocyte maturation and development in pigs. Supplementation of 250 μM L-ascorbic acid 2-phosphate sesquimagnesium salt hydrate (AA2P) during in vitro maturation significantly enhanced the nuclear maturation (as indicated by higher rate of first polar body extrusion and increased Bmp15 mRNA level), reduced level of reactive oxygen species, and promoted developmental potency (higher cleavage and blastocyst rates of parthenotes, and decreased Bax and Caspase3 mRNA levels in blastocysts) of pig oocytes. AA2P treatment caused methylation erasure in mature oocytes on nucleic acids (5-methylcytosine (5 mC) and N ⁶ -methyladenosine (m⁶A)) and histones (Histone H3 trimethylations at lysines 27, H3K27me3), but establishment of histone H3 trimethylations at lysines 4 (H3K4me3) and 36 (H3K36me3). During the global methylation reprogramming process, levels of TET2 (mRNA and protein) and Dnmt3b (mRNA) were significantly elevated, but simultaneously DNMT3A (mRNA and protein), and also Hif-1α, Hif-2α, Tet3, Mettl14, Kdm5b and Eed (mRNA) were significantly inhibited. Our findings support that ascorbic acid can reprogram the methylation status of not only DNA and histone, but also RNA, to improve pig oocyte maturation and developmental competence.