Long-term molecular and cellular stability of human neural stem cell lines

The Role of Glia Telomere Dysfunction in the Pathogenesis of Central Nervous System Diseases

Maintaining the telomere length is decisive for the viability and homeostasis process of all the cells of an organism, including human glial cells. Telomere shortening of microglial cells has been widely associated with the onset and progression of neurodegenerative diseases such as Parkinson's and Alzheimer's disease. Additionally, traumatic brain injury appears to have a positive correlation with the telomere-shortening process of microglia, and telomere length can be used as a non-invasive biomarker for the clinical management of these patients. Moreover, telomere involvement through telomerase reactivation and homologous recombination also known as the alternative lengthening of telomeres (ALT) has been described in gliomagenesis pathways, and particular focus has been given in the translational significance of these mechanisms in gliomas diagnosis and prognostic classification. Finally, glia telomere shortening is implicated in some psychiatric diseases. Given that telomere dysfunction of glial cells is involved in the central nervous system (CNS) disease pathogenesis, it represents a promising drug target that could lead to the incorporation of new tools in the medicinal arsenal for the management of so far incurable conditions.

Low Levels of Amyloid Precursor Protein (APP) Promote Neurogenesis and Decrease Gliogenesis in Human Neural Stem Cells

Amyloid precursor protein (APP) has been widely studied due to its association with Alzheimer's disease (AD). However, the physiological functions of APP are still largely unexplored. APP is a transmembrane glycoprotein whose expression in humans is abundant in the central nervous system. Specifically, several studies have revealed the high expression of APP during brain development. Previous studies in our laboratory revealed that a transient increase in APP expression induces early cell cycle exit of human neural stem cells (hNSCs) and directs their differentiation towards glial cells (gliogenesis) while decreasing their differentiation towards neurons (neurogenesis). In the present study, we have evaluated the intrinsic cellular effects of APP down-expression (using siRNA) on cell death, cell proliferation, and cell fate specification of hNSCs. Our data indicate that APP silencing causes cellular effects opposite to those obtained in previous APP overexpression assays, inducing cell proliferation in hNS1 cells (a model line of hNSCs) and favoring neurogenesis instead of gliogenesis in these cells. In addition, we have analyzed the gene and protein expression levels of β-Catenin as a possible molecule involved in these cellular effects. These data could help to understand the biological role of APP, which is necessary to deepen the knowledge of AD.

Amyloid Precursor Protein (APP) Regulates Gliogenesis and Neurogenesis of Human Neural Stem Cells by Several Signaling Pathways

Numerous studies have focused on the pathophysiological role of amyloid precursor protein (APP) because the proteolytic processing of APP to β-amyloid (Aβ) peptide is a central event in Alzheimer's disease (AD). However, many authors consider that alterations in the physiological functions of APP are likely to play a key role in AD. Previous studies in our laboratory revealed that APP plays an important role in the differentiation of human neural stem cells (hNSCs), favoring glial differentiation (gliogenesis) and preventing their differentiation toward a neuronal phenotype (neurogenesis). In the present study, we have evaluated the effects of APP overexpression in hNSCs at a global gene level by a transcriptomic analysis using the massive RNA sequencing (RNA-seq) technology. Specifically, we have focused on differentially expressed genes that are related to neuronal and glial differentiation processes, as well as on groups of differentially expressed genes associated with different signaling pathways, in order to find a possible interaction between them and APP. Our data indicate a differential expression in genes related to Notch, Wnt, PI3K-AKT, and JAK-STAT signaling, among others. Knowledge of APP biological functions, as well as the possible signaling pathways that could be related to this protein, are essential to advance our understanding of AD.

Astrocytes derived from neural progenitor cells are susceptible to Zika virus infection

Zika virus (ZIKV) was first isolated in 1947. From its isolation until 2007, symptoms of ZIKV-caused disease were limited (e.g., fever, hives, and headache); however, during the epidemic in Brazil in 2014, ZIKV infection caused Guillain-Barré syndrome in adults and microcephaly in fetuses and infants of women infected during pregnancy. The neurovirulence of ZIKV has been studied using neural progenitor cells (NPCs), brain organoids, neurons, and astrocytes. NPCs and astrocytes appear to be the most susceptible cells of the Central Nervous System to ZIKV infection. In this work, we aimed to develop a culture of astrocytes derived from a human NPC cell line. We analyze how ZIKV affects human astrocytes and demonstrate that 1) ZIKV infection reduces cell viability, increases the production of Reactive Oxygen Species (ROS), and results in high viral titers; 2) there are changes in the expression of genes that facilitate the entry of the virus into the cells; 3) there are changes in the expression of genes involved in the homeostasis of the glutamatergic system; and 4) there are ultrastructural changes in mitochondria and lipid droplets associated with production of virions. Our findings reveal new evidence of how ZIKV compromises astrocytic functionality, which may help understand the pathophysiology of ZIKV-associated congenital disease.

Neurogenesis Is Increased in Human Neural Stem Cells by Aβ40 Peptide

Amyloid-β 40 peptides [Aβ1-40 (Aβ40)] are present within amyloid plaques in the brains of patients with Alzheimer's disease (AD). Even though Aβ peptides are considered neurotoxic, they can mediate many biological processes, both in adult brains and throughout brain development. However, the physiological function of these Aβ peptides remains poorly understood, and the existing data are sometimes controversial. Here, we analyze and compare the effects of monomeric Aβ40 on the biology of differentiating human neural stem cells (human NSCs). For that purpose, we used a model of human NSCs called hNS1. Our data demonstrated that Aβ40 at high concentrations provokes apoptotic cellular death and the damage of DNA in human NSCs while also increasing the proliferation and favors neurogenesis by raising the percentage of proliferating neuronal precursors. These effects can be mediated, at least in part, by β-catenin. These results provide evidence of how Aβ modulate/regulate human NSC proliferation and differentiation, suggesting Aβ40 may be a pro-neurogenic factor. Our data could contribute to a better understanding of the molecular mechanisms involved in AD pathology and to the development of human NSC-based therapies for AD treatment, since these results could then be used in diagnosing the disease at early stages and be applied to the development of new treatment options.

Tissue-Restricted Stem Cells as Starting Cell Source for Efficient Generation of Pluripotent Stem Cells: An Overview

Induced pluripotent stem cells (iPSCs) have vast biomedical potential concerning disease modeling, drug screening and discovery, cell therapy, tissue engineering, and understanding organismal development. In the year 2006, a groundbreaking study reported the generation of iPSCs from mouse embryonic fibroblasts by viral transduction of four transcription factors, namely, Oct4, Sox2, Klf4, and c-Myc. Subsequently, human iPSCs were generated by reprogramming fibroblasts as a starting cell source using two reprogramming factor cocktails [(i) OCT4, SOX2, KLF4, and c-MYC, and (ii) OCT4, SOX2, NANOG, and LIN28]. The wide range of applications of these human iPSCs in research, therapeutics, and personalized medicine has driven the scientific community to optimize and understand this reprogramming process to achieve quality iPSCs with higher efficiency and faster kinetics. One of the essential criteria to address this is by identifying an ideal cell source in which pluripotency can be induced efficiently to give rise to high-quality iPSCs. Therefore, various cell types have been studied for their ability to generate iPSCs efficiently. Cell sources that can be easily reverted to a pluripotent state are tissue-restricted stem cells present in the fetus and adult tissues. Tissue-restricted stem cells can be isolated from fetal, cord blood, bone marrow, and other adult tissues or can be obtained by differentiation of embryonic stem cells or trans-differentiation of other tissue-restricted stem cells. Since these cells are undifferentiated cells with self-renewal potential, they are much easier to reprogram due to the inherent characteristic of having an endogenous expression of few pluripotency-inducing factors. This review presents an overview of promising tissue-restricted stem cells that can be isolated from different sources, namely, neural stem cells, hematopoietic stem cells, mesenchymal stem cells, limbal epithelial stem cells, and spermatogonial stem cells, and their reprogramming efficacy. This insight will pave the way for developing safe and efficient reprogramming strategies and generating patient-specific iPSCs from tissue-restricted stem cells derived from various fetal and adult tissues.

Oligomeric and Fibrillar Species of Aβ42 Diversely Affect Human Neural Stem Cells

Amyloid-β 42 peptide (Aβ_1-42 (Aβ42)) is well-known for its involvement in the development of Alzheimer’s disease (AD). Aβ42 accumulates and aggregates in fibers that precipitate in the form of plaques in the brain causing toxicity; however, like other forms of Aβ peptide, the role of these peptides remains unclear. Here we analyze and compare the effects of oligomeric and fibrillary Aβ42 peptide on the biology (cell death, proliferative rate, and cell fate specification) of differentiating human neural stem cells (hNS1 cell line). By using the hNS1 cells we found that, at high concentrations, oligomeric and fibrillary Aβ42 peptides provoke apoptotic cellular death and damage of DNA in these cells, but Aβ42 fibrils have the strongest effect. The data also show that both oligomeric and fibrillar Aβ42 peptides decrease cellular proliferation but Aβ42 oligomers have the greatest effect. Finally, both, oligomers and fibrils favor gliogenesis and neurogenesis in hNS1 cells, although, in this case, the effect is more prominent in oligomers. All together the findings of this study may contribute to a better understanding of the molecular mechanisms involved in the pathology of AD and to the development of human neural stem cell-based therapies for AD treatment.

Microglia-Secreted Factors Enhance Dopaminergic Differentiation of Tissue- and iPSC-Derived Human Neural Stem Cells

Microglia have recently been established as key regulators of brain development. However, their role in neuronal subtype specification remains largely unknown. Using three different co-culture setups, we show that microglia-secreted factors enhance dopaminergic differentiation of somatic and induced pluripotent stem cell-derived human neural stem cells (NSCs). The effect was consistent across different NSC and microglial cell lines and was independent of prior microglial activation, although restricted to microglia of embryonic origin. We provide evidence that the effect is mediated through reduced cell proliferation and decreased apoptosis and necrosis orchestrated in a sequential manner during the differentiation process. tumor necrosis factor alpha, interleukin-1β, and insulinlike growth factor 1 are identified as key mediators of the effect and shown to directly increase dopaminergic differentiation of human NSCs. These findings demonstrate a positive effect of microglia on dopaminergic neurogenesis and may provide new insights into inductive and protective factors that can stimulate in vitro derivation of dopaminergic neurons.

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Differentiating NSCs in co-culture with microglia enhance dopaminergic differentiation

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The effect is restricted to microglia of embryonic origin

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Microglial TNFα, IL-1β, and IGF1 are key mediators of the effect

Impact of environmental neurotoxic: current methods and usefulness of human stem cells

The development of central nervous system is a highly coordinated and complex process. Any alteration of this process can lead to disturbances in the structure and function of the brain, which can cause deficits in neurological development, resulting in neurodevelopmental disorders, including, for example, autism or attention-deficit hyperactivity disorder. Exposure to certain chemicals during the fetal period and childhood is known to cause developmental neurotoxicity and has serious consequences that persist into adult life. For regulatory purposes, determination of the potential for developmental neurotoxicity is performed according the OECD Guideline 426, in which the test substance is administered to animals during gestation and lactation. However, these animal models are expensive, long-time consuming and may not reflect the physiology in humans; that makes it an unsustainable model to test the large amount of existing chemical products, hence alternative models to the use of animals are needed. One of the most promising methods is based on the use of stem cell technology. Stem cells are undifferentiated cells with the ability to self-renew and differentiate into more specialized cell types. Because of these properties, these cells have gained increased attention as possible therapeutic agents or as disease models. Here, we provide an overview of the current models both animal and cellular, available to study developmental neurotoxicity and review in more detail the usefulness of human stem cells, their properties and how they are becoming an alternative to evaluate and study the mechanisms of action of different environmental toxicants.

Protective Functions of Reactive Astrocytes Following Central Nervous System Insult

Astrocytes play important roles in numerous central nervous system disorders including autoimmune inflammatory, hypoxic, and degenerative diseases such as Multiple Sclerosis, ischemic stroke, and Alzheimer’s disease. Depending on the spatial and temporal context, activated astrocytes may contribute to the pathogenesis, progression, and recovery of disease. Recent progress in the dissection of transcriptional responses to varying forms of central nervous system insult has shed light on the mechanisms that govern the complexity of reactive astrocyte functions. While a large body of research focuses on the pathogenic effects of reactive astrocytes, little is known about how they limit inflammation and contribute to tissue regeneration. However, these protective astrocyte pathways might be of relevance for the understanding of the underlying pathology in disease and may lead to novel targeted approaches to treat autoimmune inflammatory and degenerative disorders of the central nervous system. In this review article, we have revisited the emerging concept of protective astrocyte functions and discuss their role in the recovery from inflammatory and ischemic disease as well as their role in degenerative disorders. Focusing on soluble astrocyte derived mediators, we aggregate the existing knowledge on astrocyte functions in the maintenance of homeostasis as well as their reparative and tissue-protective function after acute lesions and in neurodegenerative disorders. Finally, we give an outlook of how these mediators may guide future therapeutic strategies to tackle yet untreatable disorders of the central nervous system.

Nucleolar disruption, activation of P53 and premature senescence in POLR3A-mutated Wiedemann-Rautenstrauch syndrome fibroblasts

Recently, mutations in the RNA polymerase III subunit A (POLR3A) have been described as the cause of the neonatal progeria or Wiedemann-Rautenstrauch syndrome (WRS). POLR3A has important roles in transcription regulation of small RNAs, including tRNA, 5S rRNA, and 7SK rRNA. We aim to describe the cellular and molecular features of WRS fibroblasts. Cultures of primary fibroblasts from one WRS patient [monoallelic POLR3A variant c.3772_3773delCT (p.Leu1258Glyfs*12)] and one control patient were cultured in vitro. The mutation caused a decrease in the expression of wildtype POLR3A mRNA and POLR3A protein and a sharp increase in mutant protein expression. In addition, there was an increase in the nuclear localization of the mutant protein. These changes were associated with an increase in the number and area of nucleoli and to a high increase in the expression of pP53 and pH2AX. All these changes were associated with premature senescence. The present observations add to our understanding of the differences between Hutchinson-Gilford progeria syndrome and WRS and opens new alternatives to study cell senesce and human aging.

Adoptive immunotherapies in neuro-oncology: classification, recent advances, and translational challenges

Background:

Adoptive immunotherapies are among the pillars of ongoing biological breakthroughs in neuro-oncology, as their potential applications are tremendously wide. The present literature review comprehensively classified adoptive immunotherapies in neuro-oncology, provides an update, and overviews the main translational challenges of this approach.

Methods:

The PubMed/MEDLINE platform, Medical Subject Heading (MeSH) database, and ClinicalTrials.gov website were the sources. The MeSH terms “Immunotherapy, Adoptive,” “Cell- and Tissue-Based Therapy,” “Tissue Engineering,” and “Cell Engineering” were combined with “Central Nervous System,” and “Brain.” “Brain tumors” and “adoptive immunotherapy” were used for a further unrestricted search. Only articles published in the last 5 years were selected and further sorted based on the best match and relevance. The search terms “Central Nervous System Tumor,” “Malignant Brain Tumor,” “Brain Cancer,” “Brain Neoplasms,” and “Brain Tumor” were used on the ClinicalTrials.gov website.

Results:

A total of 79 relevant articles and 16 trials were selected. T therapies include chimeric antigen receptor T (CAR T) cell therapy and T cell receptor (TCR) transgenic therapy. Natural killer (NK) cell-based therapies are another approach; combinations are also possible. Trials in phase 1 and 2 comprised 69% and 31% of the studies, respectively, 8 of which were concluded. CAR T cell therapy targeting epidermal growth factor receptor variant III (EGFRvIII) was demonstrated to reduce the recurrence rate of glioblastoma after standard-of-care treatment.

Conclusion:

Adoptive immunotherapies can be classified as T, NK, and NKT cell-based. CAR T cell therapy redirected against EGFRvIII has been shown to be the most promising treatment for glioblastoma. Overcoming immune tolerance and immune escape are the main translational challenges in the near future of neuro-oncology. (www.actabiomedica.it)

Innovative therapies for malignant brain tumors: the road to a tailored cure

Background:

Immune tolerance, immune escape, neoangiogenesis, phenotypic changes, and glioma stem cells are all responsible for the resistance of malignant brain tumors to current therapies and persistent recurrence. The present study provides a panoramic view of innovative therapies for malignant brain tumors, especially glioblastoma, aimed at achieving a tailored approach.

Methods:

PubMed/Medline and ClinicalTrials.gov were the main sources of an extensive literature review in which “Regenerative Medicine,” “Cell-Based Therapy,” “Chemotherapy,” “Vaccine,” “Cell Engineering,” “Immunotherapy, Active,” “Immunotherapy, Adoptive,” “Stem Cells,” “Gene Therapy,” “Target Therapy,” “Brain Cancer,” “Glioblastoma,” and “Malignant Brain Tumor” were the search terms. Only articles in English published in the last 5 years were included. A further selection was made according to the quality of the studies and level of evidence.

Results:

Cell-based and targeted therapies represent the newest frontiers of brain cancer treatment. Active and adoptive immunotherapies, stem cell therapies, and gene therapies represent a tremendous evolution in recent years due to many preclinical and clinical studies. Clinical trials have validated the effectiveness of antibody-based immunotherapies, including an in-depth study of bevacizumab, in combination with standard of care. Preclinical data highlights the role of vaccines, stem cells, and gene therapies to prevent recurrence.

Conclusion:

Monoclonal antibodies strengthen the first-line therapy for high grade gliomas. Vaccines, engineered cells, stem cells, and gene and targeted therapies are good candidates for second-line treatment of both newly diagnosed and recurrent gliomas. Further data are necessary to validate this tailored approach at the bedside. (www.actabiomedica.it)

Physiological and pathological effects of amyloid-β species in neural stem cell biology

Although amyloid-β peptide is considered neurotoxic, it may mediate several physiological processes during embryonic development and in the adult brain. The pathological function of amyloid-β peptide has been extensively studied due to its implication in Alzheimer's disease, but its physiological function remains poorly understood. Amyloid-β peptide can be detected in non-aggregated (monomeric) and aggregated (oligomeric and fibrillary) forms. Each form has different cytotoxic and/or physiological properties, so amyloid-β peptide and its role in Alzheimer's disease need to be studied further. Neural stem cells and neural precursor cells are good tools for the study on neurodegenerative diseases and can provide future therapeutic applications in diseases such as Alzheimer's disease. In this review, we provide an outline of the effects of amyloid-β peptide, in monomeric and aggregated forms, on the biology of neural stem cells/neural precursor cells, and discuss the controversies. We also describe the possible molecular targets that could be implicated in these effects, especially GSK3β. A better understanding of amyloid-β peptide (both physiological and pathological), and the signaling pathways involved are essential to advance the field of Alzheimer's disease.

The cell-based approach in neurosurgery: ongoing trends and future perspectives

OBJECTIVE

Examination of the current trends and future perspectives of the cell-based therapies in neurosurgery.

METHODS

A PubMed/MEDLINE-based systematic review has been performed combining the main Medical Subject Headings (MeSH) regarding the cell- and tissue-based therapies with the "Brain", "Spinal Cord", "Spine" and "Skull" MeSH terms. Only articles in English published in the last 10 years and pertinent to neurosurgery have been selected.

RESULTS

A total of 1,173 relevant articles have been chosen. Somatic cells and gene-modification technologies have undergone the greatest development. Immunotherapies and gene therapies have been tested for the cure of glioblastoma, stem cells mainly for brain and spinal cord traumatic injuries. Stem cells have also found a rationale in the treatment of the cranial and spinal bony defects, and of the intervertebral disc degeneration, as well.Most of the completed or ongoing trials concerning the cell-based therapies in neurosurgery are on phase 2. Future perspectives involve the need to overcome issues related to immunogenicity, oncogenicity and routes for administration. Refinement and improvement of vector design and delivery are required within the gene therapies.

CONCLUSION

The last decade has been characterised by a progressive evolution of neurosurgery from a purely mechanical phase to a new biological one. This trend has followed the rapid and parallel development of translational medicine and nanotechnologies.The introduction of new technologies, the optimisation of the already existing ones, and the reduction of costs are among the main challenges of the foreseeable future.

Effects of chlorpyrifos on cell death and cellular phenotypic specification of human neural stem cells

Chlorpyrifos (CPF) is an organophosphate pesticide widely used in agriculture, whose traditional and well-known mechanism of action is the inhibition of the enzyme Acetylcholinesterase (AChE). Subacute exposures to CPF have been associated with alterations different from the inhibition of AChE. Because of the vulnerability of the developing nervous system, prenatal and early postnatal exposures are of special concern. Human neural stem cells (hNSC) provide the opportunity to study early stages of neural development and may be a valuable tool for developmental neurotoxicology (DNT). In the current work, the cell line hNS1 was used as a model system with the aim of validating this cell line as a reliable testing method. To evaluate the effects of CPF on early developmental stages, hNS1 cells were exposed to different concentrations of the pesticide and cell death, proliferation and cell fate specification were analyzed under differentiation conditions. Since hNS1 cells responded to CPF in a similar way to other human cell lines, we consider it may be a valid model for DNT chemical assessment. CPF induced apoptotic cell death only at the highest doses tested, suggesting that it is not toxic for the specific developmental stage here addressed under short term exposure. In addition, the higher doses of CPF promoted the generation of astroglial cells, without affecting neurogenesis.

Nonhypoxic pharmacological stabilization of Hypoxia Inducible Factor 1α: Effects on dopaminergic differentiation of human neural stem cells

Parkinson's disease is a neurodegenerative disease resulting in degeneration of midbrain dopaminergic neurons. Exploratory studies using human foetal tissue or predifferentiated stem cells have suggested that intracerebral transplantation of dopaminergic precursor cells may become an effective treatment for patients with Parkinson's disease. However, strategies for dopaminergic stem cell differentiation vary widely in efficiency, and better methods still need to be developed. Hypoxia Inducible Factor 1 (HIF-1) is a transcription factor involved in the regulation of genes important for cellular adaption to hypoxia and low glucose supply. HIF-1 is to a large degree regulated by the availability of oxygen as in its presence, the subunit HIF-1α is degraded by HIF prolyl hydroxylase enzymes (HPHs). Stabilization of HIF-1α through inhibition of HPHs has been shown to increase dopaminergic differentiation of stem cells and to protect dopaminergic neurons against neurotoxins. This study investigated the effects of noncompetitive (FG-0041) and competitive (Compound A and JNJ-42041935) HIF-1α stabilizing compounds on the dopaminergic differentiation of human neural stem cells. Treatment with all HPH inhibitors at high oxygen tension (20%) resulted in HIF-1α stabilization as assessed by immunocytochemistry for HIF-1α and detection of increased levels of vascular endothelial growth factor in the conditioned culture medium. Following 10 days of HIF-1α stabilization, the cultures displayed a slightly reduced proliferative activity and significantly increased relative levels of tyrosine hydroxylase-positive dopaminergic neurons. In conclusion, HIF-1α stabilization may represent a promising strategy for the generation of dopaminergic neurons intended for use in experimental in vitro studies and cell replacement therapies.

Deregulation of the imprinted DLK1-DIO3 locus ncRNAs is associated with replicative senescence of human adipose-derived stem cells

Background

Human adult adipose-derived stem cells (hADSCs) have become the most promising cell source for regenerative medicine. However the prolonged ex vivo expansion periods required to obtain the necessary therapeutic dose promotes progressive senescence, with the concomitant reduction of their therapeutic potential.

Aim and scope

A better understanding of the determinants of hADSC senescence is needed to improve biosafety while preserving therapeutic efficiency. Here, we investigated the association between deregulation of the imprinted DLK1-DIO3 region and replicative senescence in hADSC cultures.

Methods

We compared hADSC cultures at short (P_S) and prolonged (P_L) passages, both in standard and low [O₂] (21 and 3%, respectively), in relation to replicative senescence. hADSCs were evaluated for expression alterations in the DLK1-DIO3 region on chromosome 14q32, and particularly in its main miRNA cluster.

Results

Comparison of hADSCs cultured at P_L or P_S surprisingly showed a quite significant fraction (69%) of upregulated miRNAs in P_L cultures mapping to the imprinted 14q32 locus, the largest miRNA cluster described in the genome. In agreement, expression of the lncRNA MEG3 (Maternally Expressed 3; Meg3/Gtl2), cultured at 21 and 3% [O₂], was also significantly higher in P_L than in P_S passages. During hADSC replicative senescence the AcK16H4 activating mark was found to be significantly associated with the deregulation of the entire DLK1-DIO3 locus, with a secondary regulatory role for the methylation of DMR regions.

Conclusion

A direct relationship between DLK1-DIO3 deregulation and replicative senescence of hADSCs is reported, involving upregulation of a very significant fraction of its largest miRNA cluster (14q32.31), paralleled by the progressive overexpression of the lncRNA MEG3, which plays a central role in the regulation of Dlk1/Dio3 activation status in mice.

Aβ42 Peptide Promotes Proliferation and Gliogenesis in Human Neural Stem Cells

Amyloid-β 42 [Aβ_1-42 (Aβ42)] is one of the main Aβ peptide isoforms found in amyloid plaques of brains with Alzheimer's disease (AD). Although Aβ42 is associated with neurotoxicity, it might mediate several normal physiological processes during embryonic brain development and in the adult brain. However, due to the controversy that exists in the field, relatively little is known about its physiological function. In the present work, we have analyzed the effects of different concentrations of monomeric Aβ42 on cell death, proliferation, and cell fate specification of human neural stem cells (hNSCs), specifically the hNS1 cell line, undergoing differentiation. Our results demonstrate that at higher concentrations (1 μM), Aβ42 increases apoptotic cell death and DNA damage, indicating that prolonged exposure of hNS1 cells to higher concentrations of Aβ42 is neurotoxic. However, at lower concentrations, Aβ42 significantly promotes cell proliferation and glial cell specification of hNS1 cells by increasing the pool of proliferating glial precursors, without affecting neuronal differentiation, in a concentration-dependent manner. At the molecular level, these effects could be mediated, at least in part, by GSK3β, whose expression is increased by treatment with Aβ42 and whose inhibition prevents the glial specification induced by Aβ42. Since the cellular and molecular effects are known to appear decades before the first clinical symptoms, these types of studies are important in discovering the underlying pathophysiological processes involved in the development of AD. This knowledge could then be used in diagnosing the disease at early stages and be applied to the development of new treatment options.

Effects of Amyloid-β Peptide on the Biology of Human Neural Stem Cells

The amyloid -β peptide (Aβ) is the main component of the amyloid plaques in Alzheimer's disease (AD). It has been widely demonstrated that Aβ is toxic to neurons and is associated with AD pathology. However, Aβ also appears to have an important biological function both in the adult brain and throughout embryonic development of the nervous system, acting as a trophic factor at low concentrations.It is known that Neural Stem Cells (NSCs) are capable of self-renewal and differentiate into functional glial and neuronal cells. Therefore, human NSCs may be a hope for future therapeutic application in neurodegenerative diseases such as AD. The effects of Aβ peptides on NSCs are still not well understood and remain controversial.In this chapter we outline the materials and methods used for the culture and differentiation of hNS1 cells, a cell line of human NSCs. We describe the preparation of different forms (monomeric, oligomeric and fibrillary) of Aβ peptide and subsequent cell treatment, followed by the analysis of the effects on toxicity, cell proliferation and cell fate specification of hNS1 cells.

Activation of Group II Metabotropic Glutamate Receptors Increases Proliferation but does not Influence Neuronal Differentiation of a Human Neural Stem Cell Line

The multiple functions of glutamate include regulation of neural development and stem cells. While the importance of the ionotropic glutamate receptors is well-established, less is known about the role of metabotropic glutamate receptors (mGluRs). In this study, we examined the effects of pharmacological activation and inhibition of mGluR2/3 on proliferation, differentiation and viability of a human neural stem cell line. Immunofluorescence staining revealed the presence of mGluR2/3 receptors on both proliferating and differentiating stem cells, including cells differentiated into β-tubulin III-positive immature neurons and glial fibrillary acidic protein-positive astrocytes. Stimulation of mGluR2/3 receptors during cell propagation using the agonist (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl) glycine (DCG-IV) increased total cell numbers significantly (60% compared to untreated controls). This effect could be inhibited by the specific antagonist (2S)-2-Amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid (LY341495). The antagonist alone had no effect. No significant decrease in cell death was found following mGluR2/3 stimulation, suggesting that the observed elevation in cell number was not related to cell viability. Subsequent differentiation of the cells resulted in a slight decrease in β-tubulin III-positive neurons (5.2-3.2% of total cells) for DCG-IV pre-treated cultures. Treatment with DCG-IV and LY342495 during cell differentiation alone had no such effect. Western blot analysis revealed that the active, dimeric form of mGluR2/3 was mainly present on the proliferating cells, which may explain our findings. This study emphasizes the importance of glutamate and mGluRs on regulation of human neural stem cells and suggests a significant role of mGluR2/3 during cell proliferation.

Effects of halobenzoquinone and haloacetic acid water disinfection byproducts on human neural stem cells

Human neural stem cells (hNSCs) are a useful tool to assess the developmental effects of various environmental contaminants; however, the application of hNSCs to evaluate water disinfection byproducts (DBPs) is scarce. Comprehensive toxicological results are essential to the prioritization of DBPs for further testing and regulation. Therefore, this study examines the effects of DBPs on the proliferation and differentiation of hNSCs. Prior to DBP treatment, characteristic protein markers of hNSCs from passages 3 to 6 were carefully examined and it was determined that hNSCs passaged 3 or 4 times maintained stem cell characteristics and can be used for DBP analysis. Two regulated DBPs, monobromoacetic acid (BAA) and monochloroacetic acid (CAA), and two emerging DBPs, 2,6-dibromo-1,4-benzoquinone (2,6-DBBQ) and 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ), were chosen for hNSC treatment. Both 2,6-DBBQ and 2,6-DCBQ induced cell cycle arrest at S-phase at concentrations up to 1μmol/L. Comparatively, BAA and CAA at 0.5μmol/L affected neural differentiation. These results suggest DBP-dependent effects on hNSC proliferation and differentiation. The DBP-induced cell cycle arrest and inhibition of normal hNSC differentiation demonstrate the need to assess the developmental neurotoxicity of DBPs.

Human Neural Stem Cell Therapy for Chronic Ischemic Stroke: Charting Progress from Laboratory to Patients

Chronic disability after stroke represents a major unmet neurologic need. ReNeuron's development of a human neural stem cell (hNSC) therapy for chronic disability after stroke is progressing through early clinical studies. A Phase I trial has recently been published, showing no safety concerns and some promising signs of efficacy. A single-arm Phase II multicenter trial in patients with stable upper-limb paresis has recently completed recruitment. The hNSCs administrated are from a manufactured, conditionally immortalized hNSC line (ReNeuron's CTX0E03 or CTX), generated with c-mycER^TAM technology. This technology has enabled CTX to be manufactured at large scale under cGMP conditions, ensuring sufficient supply to meets the demands of research, clinical development, and, eventually, the market. CTX has key pro-angiogenic, pro-neurogenic, and immunomodulatory characteristics that are mechanistically important in functional recovery poststroke. This review covers the progress of CTX cell therapy from its laboratory origins to the clinic, concluding with a look into the late stage clinical future.

Japanese encephalitis virus induces human neural stem/progenitor cell death by elevating GRP78, PHB and hnRNPC through ER stress

Japanese encephalitis virus (JEV), which is a causative agent of sporadic encephalitis, harbours itself inside the neural stem/progenitor cells. It is a well-known fact that JEV infects neural stem/progenitor cells and decreases their proliferation capacity. With mass spectrometry-based quantitative proteomic study, it is possible to reveal the impact of virus on the stem cells at protein level. Our aim was to perceive the stem cell proteomic response upon viral challenge. We performed a two-dimensional gel electrophoresis-based proteomic study of the human neural stem cells (hNS1 cell line) post JEV infection and found that 13 proteins were differentially expressed. The altered proteome profile of hNS1 cell line revealed sustained endoplasmic reticulum stress, which deteriorated normal cellular activities leading to cell apoptosis. The proteomic changes found in hNS1 cell line were validated in vivo in the subventricular zone of JE infected BALB/c mice. Congruent alterations were also witnessed in multipotent neural precursor cells isolated from human foetus and in autopsy samples of human brain clinically diagnosed as cases of JE patients. Endoplasmic reticulum resident chaperone GRP78, mitochondrial protein Prohibitin and heterogeneous nuclear ribonucleoprotein hnRNPC (C1/C2) have been shown to interact with viral RNA. Hence it is proposed that these are the principle candidates governing endoplasmic reticulum stress-induced apoptosis in JEV infection.

Effects of cytomegalovirus infection in human neural precursor cells depend on their differentiation state

Cytomegalovirus (CMV) is the most common cause of congenital infection in developed countries and a major cause of neurological disability in children. Although CMV can affect multiple organs, the most important sequelae of intrauterine infection are related to lesions of the central nervous system. However, little is known about the pathogenesis and the cellular events responsible for neuronal damage in infants with congenital infection. Some studies have demonstrated that neural precursor cells (NPCs) show the greatest susceptibility to CMV infection in the developing brain. We sought to establish an in vitro model of CMV infection of the developing brain in order to analyze the cellular events associated with invasion by this virus. To this end, we employed two cell lines as a permanent source of NPC, avoiding the continuous use of human fetal tissue, the human SK-N-MC neuroblastoma cell line, and an immortalized cell line of human fetal neural origin, hNS-1. We also investigated the effect of the differentiation stage in relation to the susceptibility of these cell lines by comparing the neuroblastoma cell line with the multipotent cell line hNS-1. We found that the effects of the virus were more severe in the neuroblastoma cell line. Additionally, we induced hNS-1 to differentiate and evaluated the effect of CMV in these differentiated cells. Like SK-N-MC cells, hNS-1-differentiated cells were also susceptible to infection. Viability of differentiated hNS-1 cells decreased after CMV infection in contrast to undifferentiated cells. In addition, differentiated hNS-1 cells showed an extensive cytopathic effect whereas the effect was scarce in undifferentiated cells. We describe some of the effects of CMV in neural stem cells, and our observations suggest that the degree of differentiation is important in the acquisition of susceptibility.

V-myc immortalizes human neural stem cells in the absence of pluripotency-associated traits

A better understanding of the molecular mechanisms governing stem cell self-renewal will foster the use of different types of stem cells in disease modeling and cell therapy strategies. Immortalization, understood as the capacity for indefinite expansion, is needed for the generation of any cell line. In the case of v-myc immortalized multipotent human Neural Stem Cells (hNSCs), we hypothesized that v-myc immortalization could induce a more de-differentiated state in v-myc hNSC lines. To test this, we investigated the expression of surface, biochemical and genetic markers of stemness and pluripotency in v-myc immortalized and control hNSCs (primary precursors, that is, neurospheres) and compared these two cell types to human Embryonic Stem Cells (hESCs) and fibroblasts. Using a Hierarchical Clustering method and a Principal Component Analysis (PCA), the v-myc hNSCs associated with their counterparts hNSCs (in the absence of v-myc) and displayed a differential expression pattern when compared to hESCs. Moreover, the expression analysis of pluripotency markers suggested no evidence supporting a reprogramming-like process despite the increment in telomerase expression. In conclusion, v-myc expression in hNSC lines ensures self-renewal through the activation of some genes involved in the maintenance of stem cell properties in multipotent cells but does not alter the expression of key pluripotency-associated genes.

Influence of oxygen tension on dopaminergic differentiation of human fetal stem cells of midbrain and forebrain origin

Neural stem cells (NSCs) constitute a promising source of cells for transplantation in Parkinson's disease (PD), but protocols for controlled dopaminergic differentiation are not yet available. Here we investigated the influence of oxygen on dopaminergic differentiation of human fetal NSCs derived from the midbrain and forebrain. Cells were differentiated for 10 days in vitro at low, physiological (3%) versus high, atmospheric (20%) oxygen tension. Low oxygen resulted in upregulation of vascular endothelial growth factor and increased the proportion of tyrosine hydroxylase-immunoreactive (TH-ir) cells in both types of cultures (midbrain: 9.1±0.5 and 17.1±0.4 (P<0.001); forebrain: 1.9±0.4 and 3.9±0.6 (P<0.01) percent of total cells). Regardless of oxygen levels, the content of TH-ir cells with mature neuronal morphologies was higher for midbrain as compared to forebrain cultures. Proliferative Ki67-ir cells were found in both types of cultures, but the relative proportion of these cells was significantly higher for forebrain NSCs cultured at low, as compared to high, oxygen tension. No such difference was detected for midbrain-derived cells. Western blot analysis revealed that low oxygen enhanced β-tubulin III and GFAP expression in both cultures. Up-regulation of β-tubulin III was most pronounced for midbrain cells, whereas GFAP expression was higher in forebrain as compared to midbrain cells. NSCs from both brain regions displayed less cell death when cultured at low oxygen tension. Following mictrotransplantation into mouse striatal slice cultures predifferentiated midbrain NSCs were found to proliferate and differentiate into substantial numbers of TH-ir neurons with mature neuronal morphologies, particularly at low oxygen. In contrast, predifferentiated forebrain NSCs microtransplanted using identical conditions displayed little proliferation and contained few TH-ir cells, all of which had an immature appearance. Our data may reflect differences in dopaminergic differentiation capacity and region-specific requirements of NSCs, with the dopamine-depleted striatum cultured at low oxygen offering an attractive micro-environment for midbrain NSCs.

ATM-deficient human neural stem cells as an in vitro model system to study neurodegeneration

Loss of ATM kinase, a transducer of the DNA damage response and redox sensor, causes the neurodegenerative disorder ataxia-telangiectasia (A-T). While a great deal of progress has been made in elucidating the ATM-dependent DNA damage response (DDR) network, a key challenge remains in understanding the selective susceptibility of the nervous system to faulty DDR. Several factors appear implicated in the neurodegenerative phenotype in A-T, but which of them plays a crucial role remains unclear, especially since mouse models of A-T do not fully mirror the respective human syndrome. Therefore, a number of human neural stem cell (hNSC) systems have been developed to get an insight into the molecular mechanisms of neurodegeneration as consequence of ATM inactivation. Here we review the hNSC systems developed by us an others to model A-T.

Clonal human fetal ventral mesencephalic dopaminergic neuron precursors for cell therapy research

A major challenge for further development of drug screening procedures, cell replacement therapies and developmental studies is the identification of expandable human stem cells able to generate the cell types needed. We have previously reported the generation of an immortalized polyclonal neural stem cell (NSC) line derived from the human fetal ventral mesencephalon (hVM1). This line has been biochemically, genetically, immunocytochemically and electrophysiologically characterized to document its usefulness as a model system for the generation of A9 dopaminergic neurons (DAn). Long-term in vivo transplantation studies in parkinsonian rats showed that the grafts do not mature evenly. We reasoned that diverse clones in the hVM1 line might have different abilities to differentiate. In the present study, we have analyzed 9 hVM1 clones selected on the basis of their TH generation potential and, based on the number of v-myc copies, v-myc down-regulation after in vitro differentiation, in vivo cell cycle exit, TH⁺ neuron generation and expression of a neuronal mature marker (hNSE), we selected two clones for further in vivo PD cell replacement studies. The conclusion is that homogeneity and clonality of characterized NSCs allow transplantation of cells with controlled properties, which should help in the design of long-term in vivo experiments.

Large-scale analysis reveals acquisition of lineage-specific chromosomal aberrations in human adult stem cells

In this study, we assessed the genetic integrity of over 400 samples of human multipotent stem cells using gene expression data sets. Our analysis reveals that neural and mesenchymal stem cells acquire characteristic large chromosomal aberrations at a similar, or somewhat lower, frequency to that seen in pluripotent stem cells, sometimes within a few passages in culture. Some of the identified chromosomal abnormalities can also be detected in human tumors of the respective tissues.

Neuroprotective effects of the beta-catenin stabilization in an oxygen- and glucose-deprived human neural progenitor cell culture system

β-Catenin stabilization achieved either via GSK-3β specific inhibition or involving canonical Wnt signalling pathway, contributes to neuroprotection in an oxygen-glucose deprivation (4h OGD) in vitro hypoxia model performed on human cortical neural progenitor cells previously differentiated into neurons and glia. Neuroprotection mechanisms include both acquiring tolerance to injury throughout preconditioning (72 h prior to OGD) or being pro-survival during 24h reoxygenation after the insult. Four hours of OGD induced apoptotic cell death elevation to 73 ± 1% vs. 12% measured in control and the LDH level, indicative of necrotic cell injury, elevation by 67 ± 7% (set to 100%). A significant reduction in apoptosis occurred at 24h reoxygenation with indirubin supplement which was 49 ± 6% at 2.5 μM BIO while LDH level was only 47 ± 5% of OGD. Kenpaullone was efficient in reducing both cell deaths at 5 μM (apoptosis 38 ± 1% and necrosis 33 ± 3% less than in OGD). Wnt agonist reduced apoptosis to 45 ± 3% at 0.01 μM, while LDH value was decreased to a level of 53 ± 5% of control. Our findings suggest that GSK-3beta inhibitors/β-catenin stabilizers may ultimately be useful drugs in neuroprotection and neuroregeneration therapies in vivo.

Imaging fate of stem cells at a cellular resolution in the brains of mice

Transplantation of genetically engineered cells into the central nervous system (CNS) offers immense potential for the treatment of several neurological disorders. Monitoring expression levels of transgenes and following changes in cell function and distribution over time is critical in assessing therapeutic efficacy of such cells in vivo. We detail a unique method to visualize the fate of human neural stem cells (NSC) and tumor cells at a cellular resolution in glioma bearing brains in vivo by using intravital-scanning microscopy in real-time. The ability to monitor fate of stem cells in disease models enables studies aimed at evaluating the efficacy of their treatment for CNS disorders.

In vitro and in vivo enhanced generation of human A9 dopamine neurons from neural stem cells by Bcl-XL

Human neural stem cells derived from the ventral mesencephalon (VM) are powerful research tools and candidates for cell therapies in Parkinson disease. Previous studies with VM dopaminergic neuron (DAn) precursors indicated poor growth potential and unstable phenotypical properties. Using the model cell line hVM1 (human ventral mesencephalic neural stem cell line 1; a new human fetal VM stem cell line), we have found that Bcl-X(L) enhances the generation of DAn from VM human neural stem cells. Mechanistically, Bcl-X(L) not only exerts the expected antiapoptotic effect but also induces proneural (NGN2 and NEUROD1) and dopamine-related transcription factors, resulting in a high yield of DAn with the correct phenotype of substantia nigra pars compacta (SNpc). The expression of key genes directly involved in VM/SNpc dopaminergic patterning, differentiation, and maturation (EN1, LMX1B, PITX3, NURR1, VMAT2, GIRK2, and dopamine transporter) is thus enhanced by Bcl-X(L). These effects on neurogenesis occur in parallel to a decrease in glia generation. These in vitro Bcl-X(L) effects are paralleled in vivo, after transplantation in hemiparkinsonian rats, where hVM1-Bcl-X(L) cells survive, integrate, and differentiate into DAn, alleviating behavioral motor asymmetry. Bcl-X(L) then allows for human fetal VM stem cells to stably generate mature SNpc DAn both in vitro and in vivo and is thus proposed as a helpful factor for the development of cell therapies for neurodegenerative conditions, Parkinson disease in particular.

A brain slice culture model for studies of endogenous and exogenous precursor cell migration in the rostral migratory stream

The rostral migratory stream (RMS) is the main pathway by which newly born subventricular zone (SVZ) cells reach the olfactory bulb (OB) in rodents. This migration has been well studied in vivo, but an organotypic in vitro model would facilitate more experimental investigations. Here we introduce a slice culture preparation of the rat forebrain including en suite the rostral part of the lateral ventricle, the RMS and the OB. The preparation was validated with regard to endogenous cell proliferation and migration by tracking bromodeoxyuridine (BrdU)-labelled cells in newly established and 3 and 6 week old cultures. For testing the migratory abilities of exogenous precursor cells, rat SVZ neurospheres and human neural (HNS1 cells) and mesenchymal (hMSC-TERT) stem cell lines were micrografted to the rostral SVZ of 1 and 7 day old cultures. Two weeks later graft derivatives were identified by immunohistochemical staining for human nuclei (HNS1/hMSC-TERT cells) and BrdU (HNS1 cells/neurospheres). Numerous HNS1 cells and BrdU-positive neurosphere cells were found in the RMS. Having reached the OB, subpopulations of the cells expressed the astroglial markers glial fibrillary acidic protein/hAM and the neuronal markers NeuN/tyrosine hydroxylase. Interestingly, the hMSC-TERT cells remained at the implantation site, demonstrating a diversity in migratory capability of different precursor cells. In conclusion, the RMS in rat forebrain slice cultures retains its ability to support migration of endogenous and exogenous neural precursors, making the cultures highly feasible for studies of conditions and factors regulating cell migration.

c-MycERTAM transgene silencing in a genetically modified human neural stem cell line implanted into MCAo rodent brain

Background

The human neural stem cell line CTX0E03 was developed for the cell based treatment of chronic stroke disability. Derived from fetal cortical brain tissue, CTX0E03 is a clonal cell line that contains a single copy of the c-mycER^TAM transgene delivered by retroviral infection. Under the conditional regulation by 4-hydroxytamoxifen (4-OHT), c-mycER^TAM enabled large-scale stable banking of the CTX0E03 cells. In this study, we investigated the fate of this transgene following growth arrest (EGF, bFGF and 4-OHT withdrawal) in vitro and following intracerebral implantation into a mid-cerebral artery occluded (MCAo) rat brain. In vitro, 4-weeks after removing growth factors and 4-OHT from the culture medium, c-mycER^TAM transgene transcription is reduced by ~75%. Furthermore, immunocytochemistry and western blotting demonstrated a concurrent decrease in the c-MycER^TAM protein. To examine the transcription of the transgene in vivo, CTX0E03 cells (450,000) were implanted 4-weeks post MCAo lesion and analysed for human cell survival and c-mycER^TAM transcription by qPCR and qRT-PCR, respectively.

Results

The results show that CTX0E03 cells were present in all grafted animal brains ranging from 6.3% to 39.8% of the total cells injected. Prior to implantation, the CTX0E03 cell suspension contained 215.7 (SEM = 13.2) copies of the c-mycER^TAM transcript per cell. After implantation the c-mycER^TAM transcript copy number per CTX0E03 cell had reduced to 6.9 (SEM = 3.4) at 1-week and 7.7 (SEM = 2.5) at 4-weeks. Bisulfite genomic DNA sequencing of the in vivo samples confirmed c-mycER^TAM silencing occurred through methylation of the transgene promoter sequence.

Conclusion

In conclusion the results confirm that CTX0E03 cells downregulated c-mycER^TAM transgene expression both in vitro following EGF, bFGF and 4-OHT withdrawal and in vivo following implantation in MCAo rat brain. The silencing of the c-mycER^TAM transgene in vivo provides an additional safety feature of CTX0E03 cells for potential clinical application.

Long-term multilayer adherent network (MAN) expansion, maintenance, and characterization, chemical and genetic manipulation, and transplantation of human fetal forebrain neural stem cells

Human neural stem/precursor cells (hNSC/hNPC) have been targeted for application in a variety of research models and as prospective candidates for cell-based therapeutic modalities in central nervous system (CNS) disorders. To this end, the successful derivation, expansion, and sustained maintenance of undifferentiated hNSC/hNPC in vitro, as artificial expandable neurogenic micro-niches, promises a diversity of applications as well as future potential for a variety of experimental paradigms modeling early human neurogenesis, neuronal migration, and neurogenetic disorders, and could also serve as a platform for small-molecule drug screening in the CNS. Furthermore, hNPC transplants provide an alternative substrate for cellular regeneration and restoration of damaged tissue in neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease. Human somatic neural stem/progenitor cells (NSC/NPC) have been derived from a variety of cadaveric sources and proven engraftable in a cytoarchitecturally appropriate manner into the developing and adult rodent and monkey brain while maintaining both functional and migratory capabilities in pathological models of disease. In the following unit, we describe a new procedure that we have successfully employed to maintain operationally defined human somatic NSC/NPC from developing fetal, pre-term post-natal, and adult cadaveric forebrain. Specifically, we outline the detailed methodology for in vitro expansion, long-term maintenance, manipulation, and transplantation of these multipotent precursors.

Imaging neural stem cell fate in mouse model of glioma

This unit describes a protocol for following the fate of stem cells in real time in a mouse model of glioma. Stem cells and tumor cells can be transduced with lentiviral vectors bearing two different luciferases, firefly luciferase (Fluc) and Renilla (Rluc) luciferase, respectively. With the cells labeled in this manner, bioluminescence imaging can be used to study the fate of stem cells in glioma-bearing brains in vivo.

Implantation of c-mycER TAM immortalized human mesencephalic-derived clonal cell lines ameliorates behavior dysfunction in a rat model of Parkinson's disease

Human neural stem cells offer the hope that a cell therapy treatment for Parkinson's disease (PD) could be made widely available. In this study, we describe two clonal human neural cell lines, derived from two different 10-week-old fetal mesencephalic tissues and immortalized with the c-mycER(TAM) transgene. Under the growth control of 4-hydroxytamoxifen, both cell lines display stable long-term growth in culture with a normal karyotype. In vitro, these nestin-positive cells are able to differentiate into tyrosine hydroxylase (TH)-positive neurons and are multipotential. Implantation of the undifferentiated cells into the 6-OHDA substantia nigral lesioned rat model displayed sustained improvements in a number of behavioral tests compared with noncell-implanted, vehicle-injected controls over the course of 6 months. Histological analysis of the brains showed survival of the implanted cells but no evidence of differentiation into TH-positive neurons. An average increase of approximately 26% in host TH immunoreactivity in the lesioned dorsal striatum was observed in the cell-treated groups compared to controls, with no difference in loss of TH cell bodies in the lesioned substantia nigra. Further analysis of the cell lines identified a number of expressed trophic factors, providing a plausible explanation for the effects observed in vivo. The exact mechanisms by which the implanted human neural cell lines provide behavioral improvements in the PD model are not completely understood; however, these findings provide evidence that cell therapy can be a potent treatment for PD acting through a mechanism independent of dopaminergic neuronal cell replacement.

DNA-damage response, survival and differentiation in vitro of a human neural stem cell line in relation to ATM expression

Ataxia-telangiectasia (A-T) is a neurodegenerative disorder caused by defects in the ATM kinase, a component of the DNA-damage response (DDR). Here, we employed an immortalized human neural stem-cell line (ihNSC) capable of differentiating in vitro into neurons, oligodendrocytes and astrocytes to assess the ATM-dependent response and outcome of ATM ablation. The time-dependent differentiation of ihNSC was accompanied by an upregulation of ATM and DNA-PK, sharp downregulation of ATR and Chk1, transient induction of p53 and by the onset of apoptosis in a fraction of cells. The response to ionizing radiation (IR)-induced DNA lesions was normal, as attested by the phosphorylation of ATM and some of its substrates (e.g., Nbs1, Smc1, Chk2 and p53), and by the kinetics of gamma-H2AX nuclear foci formation. Depletion in these cells of ATM by shRNA interference (shATM) attenuated the differentiation-associated apoptosis and response to IR, but left unaffected the growth, self-renewal and genomic stability. shATM cells generated a normal number of MAP2/beta-tubulin III+ neurons, but a reduced number of GalC+ oligodendrocytes, which were nevertheless more susceptible to oxidative stress. Altogether, these findings highlight the potential of ihNSCs as an in vitro model system to thoroughly assess, besides ATM, the role of DDR genes in neurogenesis and/or neurodegeneration.

AMP-activated protein kinase is involved in neural stem cell growth suppression and cell cycle arrest by 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside and glucose deprivation by down-regulating phospho-retinoblastoma protein and cyclin D

The fate of neural stem cells (NSCs), including their proliferation, differentiation, survival, and death, is regulated by multiple intrinsic signals and the extrinsic environment. We had previously reported that 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) directly induces astroglial differentiation of NSCs by activation of the Janus kinase (JAK)/Signal transducer and activator of transcription 3 (STAT3) pathway independently of AMP-activated protein kinase (AMPK). Here, we reported the observation that AICAR inhibited NSC proliferation and its underlying mechanism. Analysis of caspase activity and cell cycle showed that AICAR induced G1/G0 cell cycle arrest in NSCs, associated with decreased levels of poly(ADP-ribose) polymerase, phospho-retinoblastoma protein (Rb), and cyclin D but did not cause apoptosis. Iodotubericidin and Compound C, inhibitors of adenosine kinase and AMPK, respectively, or overexpression of a dominant-negative mutant of AMPK, but not JAK inhibitor, were able to reverse the anti-proliferative effect of AICAR. Glucose deprivation also activated the AMPK pathway, induced G0/G1 arrest, and suppressed the proliferation of NSCs, an effect associated with decreased levels of phospho-Rb and cyclin D protein. Furthermore, Compound C and overexpression of dominant-negative AMPK in C17.2 NSCs could block the glucose deprivation-mediated down-regulation of cyclin D and partially reverse the suppression of proliferation. These results suggest that AICAR and glucose deprivation might induce G1/G0 cell cycle arrest and suppress proliferation of NSCs via phospho-Rb and cyclin D down-regulation. AMPK, but not JAK/STAT3, activation is key for this inhibitory effect and may play an important role in the responses of NSCs to metabolic stresses such as glucose deprivation.

Immortalized human neural progenitor cells from the ventral telencephalon with the potential to differentiate into GABAergic neurons

Human neural progenitor cells (hNPCs) are believed to have important potential in clinical applications and basic neuroscience research. In the present study, we created a new immortalized human neural cell line, hSN12W-TERT, derived from human fetal ventral telencephalon, using IRES-based retroviral overexpression of human telomerase reverse transcriptase. We showed that after more than 40 passages, hSN12W-TERT cells possess high telomerase activity, maintain a normal diploid karyotype, and retain the characteristics of hNPCs. Under proliferative conditions, these cells remained undifferentiated, expressing the neural progenitor cell markers nestin, vimentin, and Sox2. The cells were able to differentiate into neurons, astrocytes, and oligodendrocytes after a significant decrease in the level of telomerase following withdrawal of growth factors. The neurons were postmitotic and achieved electrophysiologic competence. Furthermore, we showed that most neurons were GABAergic, especially on differentiation induced by bone morphogenetic protein-2 (BMP2). RT-PCR analysis also confirmed that hSN12W-TERT cells expressed mammalian achaete-scute homolog 1 (Mash1) and Dlx2, genes associated with the development of GABAergic cortical interneurons. BMP2 exposure may activate a positive-feedback loop of BMP signaling in hSN12W-TERT cells. Our data indicated that this hSN12W-TERT cell line could be a valuable experimental tool with which to study the regulatory roles of intrinsic and extrinsic factors in human neural stem cell biology and that it would be useful in basic research and in research seeking to discover novel drug targets for clinical candidates.

Bimodal viral vectors and in vivo imaging reveal the fate of human neural stem cells in experimental glioma model

Transplantation of genetically engineered cells into the CNS offers immense potential for the treatment of several neurological disorders. Monitoring expression levels of transgenes and following changes in cell function and distribution over time is critical in assessing therapeutic efficacy of such cells in vivo. We have engineered lentiviral vectors bearing fusions between different combinations of fluorescent and bioluminescent marker proteins and used bioluminescence imaging and intravital-scanning microscopy in real time to study the fate of human neural stem cells (hNSCs) at a cellular resolution in glioma-bearing brains in vivo. Using Renilla luciferase (Rluc)-DsRed2 or GFP-Rluc-expressing malignant human glioma model, transduced hNSCs were shown to migrate extensively toward gliomas, with hNSCs populating gliomas at 10 d after transplantation. Furthermore, transduced hNSCs survived longer in mice with gliomas than in normal brain, but did not modulate glioma progression in vivo. These studies demonstrate the utility of bimodal viral vectors and real-time imaging in evaluating fate of NSCs in diseased models and thus provide a platform for accelerating cell-based therapies for CNS disorders.

Human stem cells for CNS repair

Although most peripheral tissues have at least a limited ability for self-repair, the central nervous system (CNS) has long been known to be relatively resistant to regeneration. Small numbers of stem cells have been found in the adult brain but do not appear to be able to affect any significant recovery following disease or insult. In the last few decades, the idea of being able to repair the brain by introducing new cells to repair damaged areas has become an accepted potential treatment for neurodegenerative diseases. This review focuses on the suitability of various human stem cell sources for such treatments of both slowly progressing conditions, such as Parkinson's disease, Huntington's disease and multiple sclerosis, and acute insult, such as stroke and spinal cord injury. Despite stem cell transplantation having now moved a step closer to the clinic with the first trials of autologous mesenchymal stem cells, the effects shown are moderate and are not yet at the stage of development that can fulfil the hopes that have been placed on stem cells as a means to replace degenerating cells in the CNS. Success will depend on careful investigation in experimental models to enable us to understand not just the practicalities of stem cell use, but also the underlying biological principles.