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Research has been conducted on stem and cancer cells. Results demonstrate that nucleostemin controls stem and cancer cell prolioferation.

Temporal and spatial control of gene expression can be achieved using an inducible system as a fundamental tool for regulated transcription in basic, applied and eventually in clinical research. We describe a novel "hit and run" inducible direct reprogramming approach. In a single step, 2 days post-transfection, transiently transfected Sox2FLAG under the Leu3p-aIPM inducible control (iSox2) triggers the activation of endogenous Sox2, redirecting primary astrocytes into abundant distinct nestin-positive radial glia cells. This technique introduces a unique novel tool for safe, rapid and efficient reprogramming amendable to regenerative medicine. [ABSTRACT FROM AUTHOR]

The expression and function of several multidrug transporters (including ABCB1 and ABCG2) have been studied in human cancer cells and in mouse and human adult stem cells. However, the expression of ABCG2 in human embryonic stem cells (hESCs) remains unclear. Limited and contradictory results in the literature from two research groups have raised questions regarding its expression and function. In this study, we used quantitative real-time PCR, Northern blots, whole genome RNA sequencing, Western blots, and immunofluorescence microscopy to study ABCG2 expression in hESCs. We found that full-length ABCG2 mRNA transcripts are expressed in undifferentiated hESC lines. However, ABCG2 protein was undetectable even under embryoid body differentiation or cytotoxic drug induction. Moreover, surface ABCG2 protein was coexpressed with the differentiation marker stage-specific embryonic antigen-1 of hESCs, following constant BMP-4 signaling at days 4 and 6. This expression was tightly correlated with the downregulation of two microRNAs (miRNAs) (i.e., hsa-miR-519c and hsa-miR-520h). Transfection of miRNA mimics and inhibitors of these two miRNAs confirmed their direct involvement in the regulation ABCG2 translation. Our findings clarify the controversy regarding the expression of the ABCG2 gene and also provide new insights into translational control of the expression of membrane transporter mRNAs by miRNAs in hESCs. S TEM C ells 2012;30:2175-2187 [ABSTRACT FROM AUTHOR]

Pluripotent stem cells provide a platform to interrogate control elements that function to generate all cell types of the body. Despite their utility for modeling development and disease, the relationship of mouse and human pluripotent stem cell states to one another remains largely undefined. We have shown that mouse embryonic stem (ES) cells and epiblast stem cells (EpiSCs) are distinct, pluripotent states isolated from pre- and post-implantation embryos respectively. Human ES cells are different than mouse ES cells and share defining features with EpiSCs, yet are derived from pre-implantation human embryos. Here we show that EpiSCs can be routinely derived from pre-implantation mouse embryos. The preimplantation-derived EpiSCs exhibit molecular features and functional properties consistent with bona fide EpiSCs. These results provide a simple method for isolating EpiSCs and offer direct insight into the intrinsic and extrinsic mechanisms that regulate the acquisition of distinct pluripotent states. [ABSTRACT FROM AUTHOR]

Background: New mechanisms that regulate neural stem cell (NSC) expansion will contribute to improved assay systems and the emerging regenerative approach that targets endogenous stem cells. Expanding knowledge on the control of stem cell self renewal will also lead to new approaches for targeting the stem cell population of cancers. Methodology/Principal Findings: Here we show that Cholera toxin regulates two recently characterized NSC markers, the Tie2 receptor and the transcription factor Hes3, and promotes the expansion of NSCs in culture. Cholera toxin increases immunoreactivity for the Tie2 receptor and rapidly induces the nuclear localization of Hes3. This is followed by powerful cultured NSC expansion and induction of proliferation both in the presence and absence of mitogen. Conclusions/Significance: Our data suggest a new cell biological mechanismthat regulates the self renewal and differentiation properties of stem cells, providing a new logic to manipulate NSCs in the context of regenerative disease and cancer. [ABSTRACT FROM AUTHOR]

Background: The ability to grow a uniform cell type from the adult central nervous system (CNS) is valuable for developing cell therapies and new strategies for drug discovery. The adult mammalian brain is a source of neural stem cells (NSC) found in both neurogenic and non-neurogenic zones but difficulties in culturing these hinders their use as research tools [1,2,3,4,5,6]. Methodology/Principal Findings: Here we show that NSCs can be efficiently grown in adherent cell cultures when angiogenic signals are included in the medium. These signals include both anti-angiogenic factors (the soluble form of the Notch receptor ligand, Dll4) and pro-angiogenic factors (the Tie-2 receptor ligand, Angiopoietin 2). These treatments support the self renewal state of cultured NSCs and expression of the transcription factor Hes3, which also identifies the cancer stem cell population in human tumors. In an organotypic slice model, angiogenic factors maintain vascular structure and increase the density of dopamine neuron processes. Conclusions/Significance: We demonstrate new properties of adult NSCs and a method to generate efficient adult NSC cultures from various central nervous system areas. These findings will help establish cellular models relevant to cancer and regeneration. [ABSTRACT FROM AUTHOR]

The floor plate, an essential ventral midline organizing center that produces the morphogen Shh, has distinct properties along the neuraxis. The neurogenic potential of the floor plate and its underlying mechanisms remain unknown. Using Shh as a driver for lineage analysis, we found that the mouse midbrain, but not the hindbrain, floor plate is neurogenic, giving rise to dopamine (DA) neurons. Distinct spatiotemporal Shh and Wnt expression may distinguish the neurogenetic potential of these structures. We discovered an inhibitory role for Shh: removal of Shh resulted in neurogenesis from the hindbrain midline and, conversely, high doses of Shh inhibited proliferation and DA neuron production in midbrain cultures. We found that Wnt/beta-catenin signaling is necessary and sufficient for antagonizing Shh, DA progenitor marker induction and promotion of dopaminergic neurogenesis. These findings demonstrate how the dynamic interplay of canonical Wnt/beta-catenin signaling and Shh may orchestrate floor plate neurogenesis or a lack thereof. [ABSTRACT FROM AUTHOR]

The connection between development and neurodegeneration is emphasized via a new mouse knockout of a transcription factor that is critical for dopamine neuron specification, which produces a late-onset, asymmetric degenerative condition in a manner very similar to human Parkinson disease. [ABSTRACT FROM AUTHOR]

Despite evidence that oxygen regulates neural precursor fate, the effects of changing oxygen tensions on distinct stages in precursor differentiation are poorly understood. We found that 5% oxygen permitted clonal and long-term expansion of mouse fetal cortical precursors. In contrast, 20% oxygen caused a rapid decrease in hypoxia-inducible factor 1α and nucleophosmin, followed by the induction of p53 and apoptosis of cells. This led to a decrease in overall cell number and particularly a loss of astrocytes and oligodendrocytes. Clonal analysis revealed that apoptosis in 20% oxygen was due to a complete loss of CD133loCD24lo multipotent precursors, a substantial loss of CD133hiCD24lo multipotent precursors, and a failure of remaining CD133hiCD24lo cells to generate glia. In contrast, committed neuronal progenitors were not significantly affected. Switching clones from 5% to 20% oxygen only after mitogen withdrawal led to a decrease in total clone numbers but an even greater decrease in oligodendrocyte-containing clones. During this late exposure to 20% oxygen, bipotent glial (A2B5+) and early (platelet-derived growth factor receptor α) oligodendrocyte progenitors appeared and disappeared more quickly, relative to 5% oxygen, and late stage O4+ oligodendrocyte progenitors never appeared. These results indicate that multipotent cells and oligodendrocyte progenitors are more susceptible to apoptosis at 20% oxygen than committed neuronal progenitors. This has important implications for optimizing ex vivo production methods for cell replacement therapies. [ABSTRACT FROM AUTHOR]

The identification of regulatory elements from different cell types is necessary for understanding the mechanisms controlling cell type--specific and housekeeping gene expression. Mapping DNaseI hypersensitive (HS) sites is an accurate method for identifying the location of functional regulatory elements. We used a high throughput method called DNase-chip to identify 3,904 DNaseI HS sites from six cell types across 1% of the human genome. A significant number (22%) of DNaseI HS sites from each cell type are ubiquitously present among all cell types studied. Surprisingly, nearly all of these ubiquitous DNaseI HS sites correspond to either promoters or insulator elements: 86% of them are located near annotated transcription start sites and 10% are bound by CTCF, a protein with known enhancer-blocking insulator activity. We also identified a large number of DNaseI HS sites that are cell type specific (only present in one cell type); these regions are enriched for enhancer elements and correlate with cell type--specific gene expression as well as cell type--specific histone modifications. Finally, we found that approximately 8% of the genome overlaps a DNaseI HS site in at least one the six cell lines studied, indicating that a significant percentage of the genome is potentially functional. [ABSTRACT FROM AUTHOR]

The study of prion transmission and targeting is a major scientific issue with important consequences for public health. Only a few cell culture systems that are able to convert the cellular isoform of the prion protein into the pathologic scrapie isoform of the prion protein (PrPSc) have been described. We hypothesized that central nervous system neural stem cells (NSCs) could be the basis of a new cell culture model permissive to prion infection. Here, we report that monolayers of differentiated fetal NSCs and adult multipotent progenitor cells isolated from mice were able to propagate prions. We also demonstrated the large influence of neural cell fate on the production of PrPSc, allowing the molecular study of prion neuronal targeting in relation with strain differences. This new stem cell-based model, which is applicable to different species and to transgenic mice, will allow thoughtful investigations of the molecular basis of prion diseases, and will open new avenues for diagnostic and therapeutic research. [ABSTRACT FROM AUTHOR]

Nucleostemin (NS) was identified as a stem cell- and cancer cell-enriched nucleolar protein that controls the proliferation of these cells. Here, we report the mechanism that regulates its dynamic shuffling between the nucleolus and nucleoplasm. The nucleolar residence of nucleostemin involves a transient and a long-term binding by the basic and GTP-binding domains, and a dissociation mechanism mediated by the COOH-terminal region. This cycle is propelled by the GTP binding state of nucleostemin. We propose that a rapid nucleostemin cycle is designed to translate extra- and intra-cellular signals into the amount of nucleostemin in the nucleolus in a bidirectional and fast manner. [ABSTRACT FROM AUTHOR]

Abstract Stem cell technology promises new and rapid advances in cell therapy and drug discovery. Clearly, the value of this approach will be limited by the differentiated functions displayed by the progeny of stem cells. The foetal and adult central nervous system (CNS) harbour stem cells that can be expanded in vitro and differentiate into immature neurons and glia. Surprisingly, we do not know if neurons derived from stem cells form synapses, a definitive feature of neuronal function. Neuronal differentiation is a complex process and in this paper we establish conditions that permit extensive maturation of neurons in the presence of neurotrophins. These conditions permit the differentiation of rat hippocampal stem cells into both excitatory (glutamatergic) and inhibitory (GABAergic) neurons. The proportion of excitatory and inhibitory synapses was strongly influenced by specific neurotrophins, and these responses reflect the region of origin of the stem cells in the brain. These data show that stem cells can be used to study mechanisms of excitation and inhibition in the nervous system. [ABSTRACT FROM AUTHOR]

The production of hippocampal granule neurons continues throughout adulthood but dramatically decreases in old age. Here we show that reducing corticosteroid levels in aged rats restored the rate of cell proliferation, resulting in increased numbers of new granule neurons. This result indicates that the neuronal precursor population in the dentate gyrus remains stable into old age, but that neurogenesis is normally slowed by high levels of corticosteroids. The findings further suggest that decreased neurogenesis may contribute to age-related memory deficits associated with high corticosteroids, and that these deficits may be reversible. [ABSTRACT FROM AUTHOR]

Abstract The effects of altered N-methyl-d-aspartate (NMDA) receptor subunit composition on seizure development in kindling epilepsy were assessed in transgenic mice expressing high neuronal levels of NR2D under control of the calcium/calmodulin kinase II alpha subunit (αCaMKII) promoter. The NR2D subunit is normally present at very low levels in the mature forebrain. Transgenic mice showed a marked reduction of amygdala kindling development. Spread of epileptic activity was retarded and generalized seizures appeared later in animals overexpressing NR2D compared with wild-type mice. The progressive lengthening of epileptiform activity, which normally occurs in kindling, was also dampened in transgenic animals. We conclude that NMDA receptor subunit composition determines the progression of experimental epilepsy. [ABSTRACT FROM AUTHOR]

The article offers information on the 2009 International Society of Stem Cell Research (ISSCR) 7th Annual Meeting to be held in the Centre Convencions Internacional in Barcelona, Spain from July 8-11, 2009.

The article presents the abstract of the research BMP2 and FGF2 Cooperate to Induce Neural-Crest-Like Fates From Fetal and Adult CNS Stem Cells," by Martin H. M. Sailer, Thomas G. Hazel et al. The study cites that bone morphogenetic protein 2 induces telencephalic CNS stem cells to fates characteristic of neural crest and choroid plexus mesenchyme. The findings indicate that fibroblast growth factor 2 confers competence for dorsalization independently of its mitogenic action.

Physiological and morphological properties of cultured hippocampal neurons were measured to investigate whether NMDA receptors play a role in survival and differentiation. Neurons dissociated from mouse embryos with different NMDAR1 genotypes were grown in culture. Electrophysiological analysis verified the absence of NMDA receptor-mediated currents in neurons taken from homozygous mutant (NR1–/–) embryos. The number of surviving hippocampal neurons was 2.5-fold higher in cultures from the NR1–/– embryos compared with wild type (NR1 +/+) and heterozygous (NR1+/–) controls. Despite the lack of NMDA receptor function, NR1–/– neurons formed synapsin I-positive presynaptic boutons associated with MAP2ab-positive dendrites in culture. Confocal microscopic analysis of DiI labelled neurons confirmed the presence of dendritic spines on NR1–/– neurons with 80% of the density found in NR1 +/+ neurons. These results suggest that the NMDA receptor has little effect on general features of neuronal differentiation. In contrast, there is clear effect on neuronal survival. This finding establishes neuron number in standard culture conditions as a measure of NMDA receptor activity. [ABSTRACT FROM AUTHOR]

Schizophrenia is a neurodevelopmental psychiatric disorder, encompassing genetic and environmental risk factors. For several decades, investigators have been implementing the use of lesions of the neonatal rodent hippocampus to model schizophrenia, resulting in a broad spectrum of adult schizophrenia-related behavioral changes. Despite the extensive use of these proposed animal models of schizophrenia, the mechanisms by which these lesions result in schizophrenia-like behavioral alterations remain unclear. Here we provide in vivo evidence that transient pharmacological inactivation of the hippocampus via tetrodotoxin microinjections or a genetic reduction in brain derived neurotrophic factor (BDNF) protein levels (BDNF +/- rats) lead to global DNA hypomethylation, disrupted maturation of the neuronal nucleus and aberrant acoustic startle response in the adult rat. The similarity between the effects of the two treatments strongly indicate that BDNF signaling is involved in effects obtained after the TTX microinjections. These findings may shed light on the cellular mechanisms underlying the phenotypical features of neonatal transient inhibition of the hippocampus as a preclinical model of schizophrenia and suggest that BDNF signaling represents a target pathway for development of novel treatment therapies., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Due to increased interest in As(III) S-adenosylmethionine methyltransferase (AS3MT), a search for chemical probes that can help elucidate function was initiated. A homology model was built based on related enzymes, and virtual screening produced 426 potential hits. Evaluation of these compounds in a functional enzymatic assay revealed several modest inhibitors including an O-substituted 2-amino-3-cyano indole scaffold. Two iterations of near neighbor searches revealed compound 5 as a potent inhibitor of AS3MT with good selectivity over representative methyltransferases DOT1L and NSD2 as well as a representative set of diverse receptors. Compound 5 should prove to be a useful tool to investigate the role of AS3MT and a potential starting point for further optimization., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Use of human pluripotent stem cells (hPSCs) and their differentiated derivatives have led to recent proof-of-principle drug discoveries, defining a pathway to the implementation of hPSC-based drug discovery (hPDD). Current hPDD strategies, however, have inevitable conceptual biases and technological limitations, including the dimensionality of cell-culture methods, cell maturity and functionality, experimental variability, and data reproducibility. In this review, we dissect representative hPDD systems via analysis of hPSC-based 2D-monolayers, 3D culture, and organoids. We discuss mechanisms of drug discovery and drug repurposing, and roles of membrane drug transporters in tissue maturation and hPDD using the example of drugs that target various mutations of CFTR, the cystic fibrosis transmembrane conductance regulator gene, in patients with cystic fibrosis., (Published by Elsevier Ltd.)

Lineage commitment and differentiation of skeletal stem cells/bone marrow stromal cells (SSCs/BMSCs, often called bone marrow-derived "mesenchymal stem/stromal" cells) offer an important opportunity to study skeletal and hematopoietic diseases, and for tissue engineering and regenerative medicine. Currently, many studies in this field have relied on cell lineage tracing methods in mouse models, which have provided a significant advancement in our knowledge of skeletal and hematopoietic stem-cell niches in bone marrow (BM). However, there is a lack of agreement in numerous fundamental areas, including origins of various BM stem-cell niches, cell identities, and their physiological roles in the BM. In order to resolve these issues, we propose a new hypothesis of "paralogous" stem-cell niches (PSNs); that is, progressively altered parallel niches within an individual species throughout the life span of the organism. A putative PSN code seems to be plausible based on analysis of transcriptional signatures in two representative genes that encode Nes-GFP and leptin receptors, which are frequently used to monitor SSC lineage development in BM. Furthermore, we suggest a dynamic paralogous BM niche (PBMN) model that elucidates the coupling and uncoupling mechanisms between BM stem-cell niches and their zones of active regeneration during different developmental stages. Elucidation of these PBMNs would enable us to resolve the existing controversies, thus paving the way to achieving precision regenerative medicine and pharmaceutical applications based on these BM cell resources. Stem Cells 2018;36:11-21., (© 2017 AlphaMed Press.)

The cerebellum, a derivative of the hindbrain, plays a crucial role in balance and posture as well as in higher cognitive and locomotive processes. Cerebellar development is initiated during the segmental phase of hindbrain formation. Here, we describe the phenotype, of a single surviving adult conditional mouse mutant mouse, in which Sox2 function is ablated in embryonic radial glial cells by means of hGFAP-CRE. The single Sox2 RGINV/mosaic adult mutant mouse displays motor disability, microsomia, reduced Central Nervous System (CNS) size and cerebellar defects associated with human genetically related congenital abnormalities.

The ability to differentiate induced pluripotent stem cells (iPSCs) into committed skeletal progenitors could allow for an unlimited autologous supply of such cells for therapeutic uses; therefore, we attempted to create novel bone-forming cells from human iPSCs using lines from two distinct tissue sources and methods of differentiation that we previously devised for osteogenic differentiation of human embryonic stem cells, and as suggested by other publications. The resulting cells were assayed using in vitro methods, and the results were compared with those obtained from in vivo transplantation assays. Our results show that true bone was formed in vivo by derivatives of several iPSC lines, but that the successful cell lines and differentiation methodologies were not predicted by the results of the in vitro assays. In addition, bone was formed equally well from iPSCs originating from skin or bone marrow stromal cells (also known as bone marrow-derived mesenchymal stem cells), suggesting that the iPSCs did not retain a "memory" of their previous life. Furthermore, one of the iPSC-derived cell lines formed verifiable cartilage in vivo, which likewise was not predicted by in vitro assays., (©AlphaMed Press.)

Human pluripotent stem cells (hPSCs) have two potentially attractive applications: cell replacement-based therapies and drug discovery. Both require the efficient generation of large quantities of clinical-grade stem cells that are free from harmful genomic alterations. The currently employed colony-type culture methods often result in low cell yields, unavoidably heterogeneous cell populations, and substantial chromosomal abnormalities. Here, we shed light on the structural relationship between hPSC colonies/embryoid bodies and early-stage embryos in order to optimize current culture methods based on the insights from developmental biology. We further highlight core signaling pathways that underlie multiple epithelial-to-mesenchymal transitions (EMTs), cellular heterogeneity, and chromosomal instability in hPSCs. We also analyze emerging methods such as non-colony type monolayer (NCM) and suspension culture, which provide alternative growth models for hPSC expansion and differentiation. Furthermore, based on the influence of cell-cell interactions and signaling pathways, we propose concepts, strategies, and solutions for production of clinical-grade hPSCs, stem cell precursors, and miniorganoids, which are pivotal steps needed for future clinical applications., (Published by Elsevier B.V.)

The ex vivo expansion of stem cells is making major contribution to biomedical research. The multipotent nature of neural precursors acutely isolated from the developing central nervous system has been established in a series of studies. Understanding the mechanisms regulating cell expansion in tissue culture would support their expanded use either in cell therapies or to define disease mechanisms. Basic fibroblast growth factor (FGF2) and insulin, ligands for tyrosine kinase receptors, are sufficient to sustain neural stem cells (NSCs) in culture. Interestingly, real-time imaging shows that these cells become multipotent every time they are passaged. Here, we analyze the role of FGF2 and insulin in the brief period when multipotent cells are present. FGF2 signaling results in the phosphorylation of Erk1/2, and activation of c-Fos and c-Jun that lead to elevated cyclin D mRNA levels. Insulin signals through the PI3k/Akt pathway to regulate cyclins at the post-transcriptional level. This precise Boolean regulation extends our understanding of the proliferation of multipotent NSCs and provides a basis for further analysis of proliferation control in the cell states defined by real-time mapping of the cell lineages that form the central nervous system., (© 2013 AlphaMed Press.)

Human pluripotent stem cells (hPSCs) provide powerful resources for application in regenerative medicine and pharmaceutical development. In the past decade, various methods have been developed for large-scale hPSC culture that rely on combined use of multiple growth components, including media containing various growth factors, extracellular matrices, 3D environmental cues, and modes of multicellular association. In this Protocol Review, we dissect these growth components by comparing cell culture methods and identifying the benefits and pitfalls associated with each one. We further provide criteria, considerations, and suggestions to achieve optimal cell growth for hPSC expansion, differentiation, and use in future therapeutic applications., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Much of the excitement generated by induced pluripotent stem cell technology is concerned with the possibility of disease modeling as well as the potential for personalized cell therapy. However, to pursue this it is important to understand the 'normal' pluripotent state including its inherent variability. We have performed various molecular profiling assays for 21 hESC lines and 8 hiPSC lines to generate a comprehensive snapshot of the undifferentiated state of pluripotent stem cells. Analysis of the gene expression data revealed no iPSC-specific gene expression pattern in accordance with previous reports. We further compared cells, differentiated as embryoid bodies in 2 media proposed to initiate differentiation towards separate cell fates, as well as 20 adult tissues. From this analysis we have generated a gene list which defines pluripotency and establishes a baseline for the pluripotent state. Finally, we provide lists of genes enriched under both differentiation conditions which show the proposed bias toward independent cell fates., (Published by Elsevier B.V.)

Regenerative medicine, relying on human embryonic stem cell (hESC) technology, opens promising new avenues for therapy of many severe diseases. However, this approach is restricted by limited production of the desired cells due to the refractory properties of hESC growth in vitro. It is further hindered by insufficient control of cellular stress, growth rates, and heterogeneous cellular states under current culture conditions. In this study, we report a novel cell culture method based on a non-colony type monolayer (NCM) growth. Human ESCs under NCM remain pluripotent as determined by teratoma assays and sustain the potential to differentiate into three germ layers. This NCM culture has been shown to homogenize cellular states, precisely control growth rates, significantly increase cell production, and enhance hESC recovery from cryopreservation without compromising chromosomal integrity. This culture system is simple, robust, scalable, and suitable for high-throughput screening and drug discovery., (Published by Elsevier B.V.)

Background & Aims: Many studies of embryonic stem cells have investigated direct cell replacement of damaged tissues, but little is known about how donor cell-derived signals affect host tissue regeneration. We investigated the direct and indirect roles of human embryonic stem cell-derived cells in liver repair in mice., Methods: To promote the initial differentiation of human embryonic stem cells into mesendoderm, we activated the β-catenin signaling pathway with lithium; cells were then further differentiated into hepatocyte-like cells. The differentiated cells were purified by indocyanine green staining and laser microdissection and characterized by immunostaining, polymerase chain reaction, biochemical function, electron microscopy, and transplantation analyses. To investigate indirect effects of these cells, secreted proteins (secretomes) were analyzed by a label-free quantitative mass spectrometry. Carbon tetrachloride was used to induce acute liver injury in mice; cells or secreted proteins were administered by intrasplenic or intraperitoneal injection, respectively., Results: The differentiated hepatocyte-like cells had multiple features of normal hepatocytes, engrafted efficiently into mice, and continued to have hepatic features; they promoted proliferation of host hepatocytes and revascularization of injured host liver tissues. Proteomic analysis identified proteins secreted from these cells that might promote host tissue repair. Injection of the secreted proteins into injured livers of mice promoted significant amounts of tissue regeneration without cell grafts., Conclusions: Hepatocyte-like cells derived from human embryonic stem cells contribute to recovery of injured liver tissues in mice, not only by cell replacement but also by delivering trophic factors that support endogenous liver regeneration., (Copyright © 2012 AGA Institute. Published by Elsevier Inc. All rights reserved.)

To realize the promise of stem cell biology, it is important to identify the precise time in the history of the cell when developmental potential is restricted. To achieve this goal, we developed a real-time imaging system that captures the transitions in fate, generating neurons, astrocytes, and oligodendrocytes from single CNS stem cells in vitro. In the presence of bFGF, tripotent cells normally produce specified progenitors through a bipotent intermediate cell type. Surprisingly, the tripotent state is reset at each passage. The cytokine CNTF is thought to instruct multipotent cells to an astrocytic fate. We demonstrate that CNTF both directs astrogliogenesis from tripotent cells, bypassing two of the three normal bipotent intermediates, and later promotes the expansion of specified astrocytic progenitors. These results show how discrete cell types emerge from a multipotent cell and provide a strong basis for future studies to determine the molecular basis of fate specification.