Genome-Scale Mapping of MicroRNA Signatures in Human Embryonic Stem Cell Neurogenesis

BMPRII+ neural precursor cells isolated and characterized from organotypic neurospheres: an in vitro model of human fetal spinal cord development

Roof plate secretion of bone morphogenetic proteins (BMPs) directs the cellular fate of sensory neurons during spinal cord development, including the formation of the ascending sensory columns, though their biology is not well understood. Type-II BMP receptor (BMPRII), the cognate receptor, is expressed by neural precursor cells during embryogenesis; however, an in vitro method of enriching BMPRII+ human neural precursor cells (hNPCs) from the fetal spinal cord is absent. Immunofluorescence was undertaken on intact second-trimester human fetal spinal cord using antibodies to BMPRII and leukemia inhibitory factor (LIF). Regions of highest BMPRII+ immunofluorescence localized to sensory columns. Parenchymal and meningeal-associated BMPRII+ vascular cells were identified in both intact fetal spinal cord and cortex by co-positivity with vascular lineage markers, CD34/CD39. LIF immunostaining identified a population of somas concentrated in dorsal and ventral horn interneurons, mirroring the expression of LIF receptor/CD118. A combination of LIF supplementation and high-density culture maintained culture growth beyond 10 passages, while synergistically increasing the proportion of neurospheres with a stratified, cytoarchitecture. These neurospheres were characterized by BMPRII+/MAP2ab+/-/βIII-tubulin+/nestin-/vimentin-/GFAP-/NeuN- surface hNPCs surrounding a heterogeneous core of βIII-tubulin+/nestin+/vimentin+/GFAP+/MAP2ab-/NeuN- multipotent precursors. Dissociated cultures from tripotential neurospheres contained neuronal (βIII-tubulin+), astrocytic (GFAP+), and oligodendrocytic (O4+) lineage cells. Fluorescence-activated cell sorting-sorted BMPRII+ hNPCs were MAP2ab+/-/βIII-tubulin+/GFAP-/O4- in culture. This is the first isolation of BMPRII+ hNPCs identified and characterized in human fetal spinal cords. Our data show that LIF combines synergistically with high-density reaggregate cultures to support the organotypic reorganization of neurospheres, characterized by surface BMPRII+ hNPCs. Our study has provided a new methodology for an in vitro model capable of amplifying human fetal spinal cord cell numbers for > 10 passages. Investigations of the role BMPRII plays in spinal cord development have primarily relied upon mouse and rat models, with interpolations to human development being derived through inference. Because of significant species differences between murine biology and human, including anatomical dissimilarities in central nervous system (CNS) structure, the findings made in murine models cannot be presumed to apply to human spinal cord development. For these reasons, our human in vitro model offers a novel tool to better understand neurodevelopmental pathways, including BMP signaling, as well as spinal cord injury research and testing drug therapies.

Xenogenic Neural Stem Cell-Derived Extracellular Nanovesicles Modulate Human Mesenchymal Stem Cell Fate and Reconstruct Metabolomic Structure

Extracellular nanovesicles, particularly exosomes, can deliver their diverse bioactive biomolecular content, including miRNAs, proteins, and lipids, thus providing a context for investigating the capability of exosomes to induce stem cells toward lineage-specific cells and tissue regeneration. In this study, it is demonstrated that rat subventricular zone neural stem cell-derived exosomes (rSVZ-NSCExo) can control neural-lineage specification of human mesenchymal stem cells (hMSCs). Microarray analysis shows that the miRNA content of rSVZ-NSCExo is a faithful representation of rSVZ tissue. Through immunocytochemistry, gene expression, and multi-omics analyses, the capability to use rSVZ-NSCExo to induce hMSCs into a neuroglial or neural stem cell phenotype and genotype in a temporal and dose-dependent manner via multiple signaling pathways is demonstrated. The current study presents a new and innovative strategy to modulate hMSCs fate by harnessing the molecular content of exosomes, thus suggesting future opportunities for rSVZ-NSCExo in nerve tissue regeneration.

Nutraceutical regulation of miRNAs involved in neurodegenerative diseases and brain cancers

The human brain is a well-connected, intricate network of neurons and supporting glial cells. Neurodegenerative diseases arise as a consequence of extensive loss of neuronal cells leading to disruption of their natural structure and function. On the contrary, rapid proliferation and growth of glial as well as neuronal cells account for the occurrence of malignancy in brain. In both cases, the molecular microenvironment holds pivotal importance in the progression of the disease. MicroRNAs (miRNA) are one of the major components of the molecular microenvironment. miRNAs are small, noncoding RNAs that control gene expression post-transcriptionally. As compared to other tissues, the brain expresses a substantially high number of miRNAs. In the early stage of neurodegeneration, miRNA expression upregulates, while in oncogenesis, miRNA expression is gradually lost. Neurodegeneration and brain cancer is presumed to be under the influence of identical pathways of cell proliferation, differentiation and cell death which are tightly regulated by miRNAs. It has been confirmed experimentally that miRNA expression can be regulated by nutraceuticals - macronutrients, micronutrients or natural products derived from food; thereby making dietary supplements immensely significant for targeting miRNAs having altered expression patterns during neurodegeneration or oncogenesis. In this review, we will discuss in detail, about the common miRNAs involved in brain cancers and neurodegenerative diseases along with the comprehensive list of miRNAs involved separately in both pathological conditions. We will also discuss the role of nutraceuticals in the regulation of those miRNAs which are involved in both of these pathological conditions.

MicroRNAs expressed in neuronal differentiation and their associated pathways: Systematic review and bioinformatics analysis

MicroRNAs (miRNAs) plays an important role in the human brain from the embryonic period to adulthood. In this sense, they influence the development of neural stem cells (NSCs), regulating cellular differentiation and survival. Therefore, due to the importance of better comprehending the regulation of miRNAs in NSCs differentiation and the lack of studies that show the panorama of miRNAs and their signaling pathways studied until now we aimed to systematically review the literature to identify which miRNAs are currently being associated with neuronal differentiation and using bioinformatics analysis to identify their related pathways. A search was carried out in the following databases: Scientific Electronic Library Online (Scielo), National Library of Medicine National Institutes of Health (PubMed), Scopus, Web of Science and Science Direct, using the descriptors "(microRNA [MeSH])" and "(neurogenesis [MeSH])". From the articles found, two independent and previously calibrated reviewers, using the EndNote X7 (Thomson Reuters, New York, NY, US), selected those that concern miRNA in the development of NSCs, based on in vitro studies. After, bioinformatic analysis was performed using the software DIANA Tools, mirPath v.3. Subsequently, data was tabulated, analyzed and interpreted. Among the 106 miRNAs cited by included studies, 55 were up-regulated and 47 were down-regulated. The bioinformatics analysis revealed that among the up-regulated miRNAs there were 24 total and 6 union pathways, and 3 presented a statistically significant difference (p ≤ 0.05). Among the down-regulated miRNAs, 46 total and 13 union pathways were found, with 7 presenting a significant difference (p ≤ 0.05). The miR-125a-5p, miR-423-5p, miR-320 were the most frequently found miRNAs in the pathways determined by bioinformatics. In this study a panel of altered miRNAs in neuronal differentiation was created with their related pathways, which could be a step towards understanding the complex network of miRNAs in neuronal differentiation.

Retinoic acid and microRNA

Retinoic acid (RA), the biologically active metabolite of vitamin A, regulates a vast spectrum of biological processes, such as cell differentiation, proliferation, apoptosis, and morphogenesis. microRNAs (miRNAs) play a crucial role in regulating gene expression by binding to messenger RNA (mRNA) which leads to mRNA degradation and/or translational repression. Like RA, miRNAs regulate multiple biological processes, including proliferation, differentiation, apoptosis, neurogenesis, tumorigenesis, and immunity. In fact, RA regulates the expression of many miRNAs to exert its biological functions. miRNA and RA regulatory networks have been studied in recent years. In this manuscript, we summarize literature that highlights the impact of miRNAs in RA-regulated molecular networks included in the PubMed.

Alteration of miRNA-mRNA interactions in lymphocytes of individuals with schizophrenia

The aetiology of schizophrenia is complex, heterogeneous, and involves interplay of many genetic and environmental influences. While significant progress has been made in the understanding the common heritable component, we are still grappling with the genomic encoding of environmental risk. One class of molecule that has tremendous potential is miRNA. These molecules are regulated by genetic and environmental factors associated with schizophrenia and have a very significant impact on temporospatial patterns of gene expression. To better understand the relationship between miRNA and gene expression in the disorder we analysed these molecules in RNA isolated from peripheral blood mononuclear cells (PBMCs) obtained from an Australian cohort of 36 individuals with schizophrenia and 15 healthy controls using next-generation RNA sequencing. Significant changes in both mRNA and miRNA expression profiles were observed implicating important interaction networks involved in immune activity and development. We also observed sexual dimorphism, particularly in relation to variation in mRNA, with males showing significantly more differentially expressed genes. Interestingly, while we explored expression in lymphocytes, the systems biology of miRNA-mRNA interactions was suggestive of significant pleiotropy with enrichment of networks related to neuronal activity.

Exosome-Mediated Ultra-Effective Direct Conversion of Human Fibroblasts into Neural Progenitor-like Cells

Exosomes, naturally secreted nanoparticles, have been introduced as vehicles for horizontal transfer of genetic material. We induced autologous exosomes containing a cocktail of reprogramming factors ("reprosomes") to convert fibroblasts into neural progenitor cells (NPCs). The fibroblasts were treated with ultrasound and subsequently cultured in neural stem cell medium for 1 day to induce the release of reprosomes composed of reprogramming factors associated with chromatin remodeling and neural lineage-specific factors. After being treated with reprosomes, fibroblasts were converted into NPCs (rNPCs) with great efficiency via activation of chromatin remodeling, so quickly that only 5 days were required for the formation of 1500 spheroids showing an NPC-like phenotype. The rNPCs maintained self-renewal and proliferative properties for several weeks and successfully differentiated into neurons, astrocytes, and oligodendrocytes in vitro and in vivo. Reprosome-mediated cellular reprogramming is simple, safe, and efficient to produce autologous stem cells for clinical application.

High content image analysis reveals function of miR-124 upstream of Vimentin in regulating motor neuron mitochondria

microRNAs (miRNAs) are critical for neuronal function and their dysregulation is repeatedly observed in neurodegenerative diseases. Here, we implemented high content image analysis for investigating the impact of several miRNAs in mouse primary motor neurons. This survey directed our attention to the neuron-specific miR-124, which controls axonal morphology. By performing next generation sequencing analysis and molecular studies, we characterized novel roles for miR-124 in control of mitochondria localization and function. We further demonstrated that the intermediate filament Vimentin is a key target of miR-124 in this system. Our data establishes a new pathway for control of mitochondria function in motor neurons, revealing the value of a neuron-specific miRNA gene as a mechanism for the re-shaping of otherwise ubiquitously-expressed intermediate filament network, upstream of mitochondria activity and cellular metabolism.

The BAF45D Protein Is Preferentially Expressed in Adult Neurogenic Zones and in Neurons and May Be Required for Retinoid Acid Induced PAX6 Expression

Adult neurogenesis is important for the development of regenerative therapies for human diseases of the central nervous system (CNS) through the recruitment of adult neural stem cells (NSCs). NSCs are characterized by the capacity to generate neurons, astrocytes, and oligodendrocytes. To identify key factors involved in manipulating the adult NSC neurogenic fate thus has crucial implications for the clinical application. Here, we report that BAF45D is expressed in the subgranular zone (SGZ) of the dentate gyrus, the subventricular zone (SVZ) of the lateral ventricle, and the central canal (CC) of the adult spinal cord. Coexpression of BAF45D with glial fibrillary acidic protein (GFAP), a radial glial like cell marker protein, was identified in the SGZ, the SVZ and the adult spinal cord CC. Quantitative analysis data indicate that BAF45D is preferentially expressed in the neurogenic zone of the LV and the neurons of the adult CNS. Furthermore, during the neuroectoderm differentiation of H9 cells, BAF45D is required for the expression of PAX6, a neuroectoderm determinant that is also known to regulate the self-renewal and neuronal fate specification of adult neural stem/progenitor cells. Together, our results may shed new light on the expression of BAF45D in the adult neurogenic zones and the contribution of BAF45D to early neural development.

Post-transcriptional gene silencing mediated by microRNAs is controlled by nucleoplasmic Sfpq

There is a growing body of evidence about the presence and the activity of the miRISC in the nucleus of mammalian cells. Here, we show by quantitative proteomic analysis that Ago2 interacts with the nucleoplasmic protein Sfpq in an RNA-dependent fashion. By a combination of HITS-CLIP and transcriptomic analyses, we demonstrate that Sfpq directly controls the miRNA targeting of a subset of binding sites by local binding. Sfpq modulates miRNA targeting in both nucleoplasm and cytoplasm, indicating a nucleoplasmic commitment of Sfpq-target mRNAs that globally influences miRNA modes of action. Mechanistically, Sfpq binds to a sizeable set of long 3′UTRs forming aggregates to optimize miRNA positioning/recruitment at selected binding sites, including let-7a binding to Lin28A 3′UTR. Our results extend the miRNA-mediated post-transcriptional gene silencing into the nucleoplasm and indicate that an Sfpq-dependent strategy for controlling miRNA activity takes place in cells, contributing to the complexity of miRNA-dependent gene expression control.

MicroRNAs have been best characterized for their functions in the cytoplasm; however, there is growing evidence of a nuclear localized role. Here, the authors identify Sfpq as an Ago2-interacting protein that modulates miRNA activity in both the nucleus and cytoplasm.

Micro RNAs and DNA methylation are regulatory players in human cells with altered X chromosome to autosome balance

The gene balance hypothesis predicts that an imbalance in the dosage sensitive genes affects the cascade of gene networks that may influence the fitness of individuals. The phenotypes associated with chromosomal aneuploidies demonstrate the importance of gene dosage balance. We have employed untransformed human fibroblast cells with different number of X chromosomes to assess the expression of miRNAs and autosomal genes in addition to the DNA methylation status. High throughput NGS analysis using illumina Next seq500 has detected several autosomal as well as X linked miRNAs as differentially expressed in X monosomy and trisomy cells. Two of these miRNAs (hsa-miR-125a-5p and 335-5p) are likely to be involved in regulation of the autosomal gene expression. Additionally, our data demonstrates altered expression and DNA methylation signatures of autosomal genes in X monosomy and trisomy cells. In addition to miRNAs, expression of DNMT1 which is an important epigenetic player involved in many processes including cancer, is seen to be altered. Overall, present study provides a proof for regulatory roles of micro RNAs and DNA methylation in human X aneuploidy cells opening up possible new ways for designing therapeutic strategies.

Direct Conversion of Pluripotent Human Embryonic Stem Cells Under Defined Culture Conditions into Human Neuronal or Cardiomyocyte Cell Therapy Derivatives

Developing novel strategies for well-controlled efficiently directing pluripotent human embryonic stem cells (hESCs) exclusively and uniformly towards clinically relevant cell types in a lineage-specific manner is not only crucial for unveiling the molecular and cellular cues that direct human embryogenesis but also vital to harnessing the power of hESC biology for tissue engineering and cell-based therapies. Conventional hESC differentiation methods require uncontrollable simultaneous multi-lineage differentiation of pluripotent cells, which yield embryoid bodies (EB) or aggregates consisting of a mixed population of cell types of three embryonic germ layers, among which only a very small fraction of cells display targeted differentiation, impractical for commercial and clinical applications. Here, a protocol for lineage-specific differentiation of hESCs, maintained under defined culture systems, direct from the pluripotent stage using small-molecule induction exclusively and uniformly to a neural or a cardiac lineage is described. Lineage-specific differentiation of pluripotent hESCs by small-molecule induction enables well-controlled highly efficient direct conversion of nonfunctional pluripotent hESCs into a large supply of high-purity functional human neuronal or cardiomyocyte cell therapy derivatives for commercial and therapeutic uses.

Therapeutic potential of microRNA let-7: tumor suppression or impeding normal stemness

The first microRNA, let-7, and its family were discovered in Caenorhabditis elegans and are functionally conserved from worms to humans in the regulation of embryonic development and stemness. The let-7 family has been shown to have an essential role in stem cell differentiation and tumor-suppressive activity. Deregulating expression of let-7 is commonly reported in many human cancers. Emerging evidence has accumulated and suggests that reestablishment of let-7 in tumor cells is a valuable therapeutic strategy. However, findings reach beyond tumor therapeutics and may impinge on stemness and differentiation of stem cells. In this review, we discuss the role of let-7 in development and differentiation of normal adult stem/progenitor cells and offer a viewpoint of the association between deregulated let-7 expression and tumorigenesis. The regulation of let-7 expression, cancer-relevant let-7 targets, and the application of let-7 are highlighted.

The effects of microRNAs on human neural stem cell differentiation in two- and three-dimensional cultures

Introduction

Stem cells have the ability to self-renew or to differentiate into numerous cell types; however, our understanding of how to control and exploit this potential is currently limited. An emerging hypothesis is that microRNAs (miRNAs) play a central role in controlling stem cell-fate determination. Herein, we have characterized the effects of miRNAs in differentiated human neural stem cells (hNSCs) by using a cell line currently being tested in clinical trials for stroke disability (NCT01151124, Clinicaltrials.gov).

Methods

HNSCs were differentiated on 2- (2D) and 3-dimensional (3D) cultures for 1 and 3 weeks. Quantification of hNSC differentiation was measured with real-time PCR and axon outgrowth. The miRNA PCR arrays were implemented to investigate differential expression profiles in differentiated hNSCs. Evaluation of miRNA effects on hNSCs was performed by using transfection of miRNA mimics, real-time PCR, Western blot, and immunocytochemistry.

Results

The 3D substrate promoted enhanced hNSC differentiation coupled with a loss of cell proliferation. Differentiated hNSCs exhibited a similar miRNA profiling. However, in 3D samples, the degree and timing of regulation were significantly different in miRNA members of cluster mi-R17 and miR-96-182, and hsa-miR-302a. Overall, hNSC 3D cultures demonstrated differential regulation of miRNAs involved in hNSC stemness, cell proliferation, and differentiation.

The miRNA mimic analysis of hsa-miR-146b-5p and hsa-miR-99a confirmed induction of lineage-committed progenitors. Downregulated miRNAs were more abundant; those most significantly downregulated were selected, and their putative target mRNAs analyzed with the aim of unraveling their functionality. In differentiated hNSCs, downregulated hsa-miR-96 correlated with SOX5 upregulation of gene and protein expression; similar results were obtained for hsa-miR-302a, hsa-miR-182, hsa-miR-7, hsa-miR-20a/b, and hsa-miR-17 and their target NR4A3. Moreover, SOX5 was identified as a direct target gene of hsa-miR-96, and NR43A, a direct target of hsa-miR-7 and hsa-mir-17 by luciferase reporter assays. Therefore, the regulatory role of these miRNAs may occur through targeting NR4A3 and SOX5, both reported as modulators of cell-cycle progression and axon length.

Conclusions

The results provide new insight into the identification of specific miRNAs implicated in hNSC differentiation. These strategies may be exploited to optimize in vitro hNSC differentiation potential for use in preclinical studies and future clinical applications.

Steroids as external temporal codes act via microRNAs and cooperate with cytokines in differential neurogenesis

The generation of neuronal cell diversity is controlled by interdependent mechanisms, including cell intrinsic programs and environmental cues. During development, the astonishing variety of neurons is originated according to a precise timetable that is managed by a complex network of genes specifying individual types of neurons. Different neurons express specific sets of transcription factors, and they can be recognized by morphological characteristics and spatial localization, but, most importantly, they connect to each other and form functional units in a stereotyped fashion. This connectivity depends, mostly, on selective cell adhesion that is strictly regulated. While intrinsic factors specifying neuronal temporal identity have been extensively studied, an extrinsic temporal factor controlling neuronal temporal identity switch has not been shown. Our data demonstrate that pulses of steroid hormone act as a temporal cue to fine-tune neuronal cell differentiation. Here we also provide evidence that extrinsic JAK/STAT cytokine signaling acts as a spatial code in the process. Particularly, in Drosophila mushroom bodies, neuronal identity transition is controlled by steroid-dependent microRNAs that regulate spatially distributed cytokine-dependent signaling factors that in turn modulate cell adhesion. A new era of neuronal plasticity assessment via managing external temporal cues such as hormones and cytokines that specify individual types of neurons might open new possibilities for brain regenerative therapeutics.

Constraining the Pluripotent Fate of Human Embryonic Stem Cells for Tissue Engineering and Cell Therapy - The Turning Point of Cell-Based Regenerative Medicine

To date, the lack of a clinically-suitable source of engraftable human stem/progenitor cells with adequate neurogenic potential has been the major setback in developing safe and effective cell-based therapies for regenerating the damaged or lost CNS structure and circuitry in a wide range of neurological disorders. Similarly, the lack of a clinically-suitable human cardiomyocyte source with adequate myocardium regenerative potential has been the major setback in regenerating the damaged human heart. Given the limited capacity of the CNS and heart for self-repair, there is a large unmet healthcare need to develop stem cell therapies to provide optimal regeneration and reconstruction treatment options to restore normal tissues and function. Derivation of human embryonic stem cells (hESCs) provides a powerful in vitro model system to investigate molecular controls in human embryogenesis as well as an unlimited source to generate the diversity of human somatic cell types for regenerative medicine. However, realizing the developmental and therapeutic potential of hESC derivatives has been hindered by the inefficiency and instability of generating clinically-relevant functional cells from pluripotent cells through conventional uncontrollable and incomplete multi-lineage differentiation. Recent advances and breakthroughs in hESC research have overcome some major obstacles in bringing hESC therapy derivatives towards clinical applications, including establishing defined culture systems for de novo derivation and maintenance of clinical-grade pluripotent hESCs and lineage-specific differentiation of pluripotent hESCs by small molecule induction. Retinoic acid was identified as sufficient to induce the specification of neuroectoderm direct from the pluripotent state of hESCs and trigger a cascade of neuronal lineage-specific progression to human neuronal progenitors and neurons of the developing CNS in high efficiency, purity, and neuronal lineage specificity by promoting nuclear translocation of the neuronal specific transcription factor Nurr-1. Similarly, nicotinamide was rendered sufficient to induce the specification of cardiomesoderm direct from the pluripotent state of hESCs by promoting the expression of the earliest cardiac-specific transcription factor Csx/Nkx2.5 and triggering progression to cardiac precursors and beating cardiomyocytes with high efficiency. This technology breakthrough enables direct conversion of pluripotent hESCs into a large supply of high purity neuronal cells or heart muscle cells with adequate capacity to regenerate CNS neurons and contractile heart muscles for developing safe and effective stem cell therapies. Transforming pluripotent hESCs into fate-restricted therapy derivatives dramatically increases the clinical efficacy of graft-dependent repair and safety of hESC-derived cellular products. Such milestone advances and medical innovations in hESC research allow generation of a large supply of clinical-grade hESC therapy derivatives targeting for major health problems, bringing cell-based regenerative medicine to a turning point.

Constraining the Pluripotent Fate of Human Embryonic Stem Cells for Tissue Engineering and Cell Therapy - The Turning Point of Cell-Based Regenerative Medicine

To date, the lack of a clinically-suitable source of engraftable human stem/progenitor cells with adequate neurogenic potential has been the major setback in developing safe and effective cell-based therapies for regenerating the damaged or lost CNS structure and circuitry in a wide range of neurological disorders. Similarly, the lack of a clinically-suitable human cardiomyocyte source with adequate myocardium regenerative potential has been the major setback in regenerating the damaged human heart. Given the limited capacity of the CNS and heart for self-repair, there is a large unmet healthcare need to develop stem cell therapies to provide optimal regeneration and reconstruction treatment options to restore normal tissues and function. Derivation of human embryonic stem cells (hESCs) provides a powerful in vitro model system to investigate molecular controls in human embryogenesis as well as an unlimited source to generate the diversity of human somatic cell types for regenerative medicine. However, realizing the developmental and therapeutic potential of hESC derivatives has been hindered by the inefficiency and instability of generating clinically-relevant functional cells from pluripotent cells through conventional uncontrollable and incomplete multi-lineage differentiation. Recent advances and breakthroughs in hESC research have overcome some major obstacles in bringing hESC therapy derivatives towards clinical applications, including establishing defined culture systems for de novo derivation and maintenance of clinical-grade pluripotent hESCs and lineage-specific differentiation of pluripotent hESCs by small molecule induction. Retinoic acid was identified as sufficient to induce the specification of neuroectoderm direct from the pluripotent state of hESCs and trigger a cascade of neuronal lineage-specific progression to human neuronal progenitors and neurons of the developing CNS in high efficiency, purity, and neuronal lineage specificity by promoting nuclear translocation of the neuronal specific transcription factor Nurr-1. Similarly, nicotinamide was rendered sufficient to induce the specification of cardiomesoderm direct from the pluripotent state of hESCs by promoting the expression of the earliest cardiac-specific transcription factor Csx/Nkx2.5 and triggering progression to cardiac precursors and beating cardiomyocytes with high efficiency. This technology breakthrough enables direct conversion of pluripotent hESCs into a large supply of high purity neuronal cells or heart muscle cells with adequate capacity to regenerate CNS neurons and contractile heart muscles for developing safe and effective stem cell therapies. Transforming pluripotent hESCs into fate-restricted therapy derivatives dramatically increases the clinical efficacy of graft-dependent repair and safety of hESC-derived cellular products. Such milestone advances and medical innovations in hESC research allow generation of a large supply of clinical-grade hESC therapy derivatives targeting for major health problems, bringing cell-based regenerative medicine to a turning point.

Embedding the Future of Regenerative Medicine into the Open Epigenomic Landscape of Pluripotent Human Embryonic Stem Cells

It has been recognized that pluripotent human embryonic stem cells (hESCs) must be transformed into fate-restricted derivatives before use for cell therapy. Realizing the therapeutic potential of pluripotent hESC derivatives demands a better understanding of how a pluripotent cell becomes progressively constrained in its fate options to the lineages of tissue or organ in need of repair. Discerning the intrinsic plasticity and regenerative potential of human stem cell populations reside in chromatin modifications that shape the respective epigenomes of their derivation routes. The broad potential of pluripotent hESCs is defined by an epigenome constituted of open conformation of chromatin mediated by a pattern of Oct-4 global distribution that corresponds genome-wide closely with those of active chroma tin modifications. Dynamic alterations in chromatin states correlate with loss-of-Oct4-associated hESC differentiation. The epigenomic transition from pluripotence to restriction in lineage choices is characterized by genome-wide increases in histone H3K9 methylation that mediates global chromatin-silencing and somatic identity. Human stem cell derivatives retain more open epigenomic landscape, therefore, more developmental potential for scale-up regeneration, when derived from the hESCs in vitrothan from the CNS tissuein vivo . Recent technology breakthrough enables direct conversion of pluripotent hESCs by small molecule induction into a large supply of lineage-specific neuronal cells or heart muscle cells with adequate capacity to regenerate neurons and contractile heart muscles for developing safe and effective stem cell therapies. Nuclear translocation of NAD-dependent histone deacetylase SIRT1 and global chromatin silencing lead to hESC cardiac fate determination, while silencing of pluripotence-associated hsa-miR-302 family and drastic up-regulation of neuroectodermal Hox miRNA hsa-miR-10 family lead to hESC neural fate determination. These recent studies place global chromatin dynamics as central to tracking the normal pluripotence and lineage progres sion of hESCs. Embedding lineage-specific genetic and epigenetic developmental programs into the open epigenomic landscape of pluripotent hESCs offers a new repository of human stem cell therapy derivatives for the future of regenerative medicine.

Human Stem Cell Derivatives Retain More Open Epigenomic Landscape When Derived from Pluripotent Cells than from Tissues

The growing number of identified stem cell derivatives and escalating concerns for safety and efficacy of these cells towards clinical applications have made it increasingly crucial to be able to assess the relative risk-benefit ratio of a given stem cell from a given source for a particular disease. Discerning the intrinsic plasticity and regenerative potential of human stem cell populations might reside in chromatin modifications that shape the respective epigenomes of their derivation routes. Previously, we have generated engraftable human neuronal progenitors direct from pluripotent human embryonic stem cells (hESCs) by small molecule induction (hESC-I hNuPs). Unlike the prototypical neuroepithelial-like nestin-positive human neural stem cells (hNSCs), these in vitro neuroectoderm-derived Nurr1-positive hESC-I hNuPs are a more neuronal lineage-specific and plastic hESC derivative. In this study, the global chromatin landscape changes in pluripotent hESCs and their neuronal lineage-specific derivative hESC-I hNuPs were profiled using genome-wide mapping and compared to CNS tissue-derived hNSCs. This study found that the broad potential of pluripotent hESCs is defined by an epigenome constituted of open conformation of chromatin mediated by a pattern of Oct-4 global distribution that corresponds closely with those of acetylated nucleosomes genome-wide. The epigenomic transition from pluripotency to restriction in lineage choices is characterized by genome-wide increases in histone H3K9 methylation that mediates global chromatin-silencing and somatic identity. Tissue-resident CNS-derived hNSCs have acquired a substantial number of additional histone H3K9 methylation, therefore, more silenced chromatin. These data suggest that the intrinsic plasticity and regenerative potential of human stem cell derivatives can be differentiated by their epigenomic landscape features, and that human stem cell derivatives retain more open epigenomic landscape, therefore, more developmental potential for scale-up regeneration, when derived from the hESCs in vitro than from the CNS tissue in vivo.