Large-scale sources of neural stem cells

Soft Biological Actuators for Meter-Scale Homeostatic Biohybrid Robots

Skeletal muscle's elegant protein-based architecture powers motion throughout the animal kingdom, with its constituent actomyosin complexes driving intra- and extra-cellular motion. Classical motors and recently developed soft actuators cannot match the packing density and contractility of individual muscle fibers that scale to power the motion of ants and elephants alike. Accordingly, the interdisciplinary fields of robotics and tissue engineering have combined efforts to build living muscle actuators that can power a new class of robots to be more energy-efficient, dexterous, and safe than existing motor-powered and hydraulic paradigms. Doing so ethically and at scale─creating meter-scale tissue constructs from sustainable muscle progenitor cell lines─has inspired innovations in biomaterials and tissue culture methodology. We weave discussions of muscle cell biology, materials chemistry, tissue engineering, and biohybrid design to review the state of the art in soft actuator biofabrication. Looking forward, we outline a vision for meter-scale biohybrid robotic systems and tie discussions of recent progress to long-term research goals.

Microfluidics for Neuronal Cell and Circuit Engineering

The widespread adoption of microfluidic devices among the neuroscience and neurobiology communities has enabled addressing a broad range of questions at the molecular, cellular, circuit, and system levels. Here, we review biomedical engineering approaches that harness the power of microfluidics for bottom-up generation of neuronal cell types and for the assembly and analysis of neural circuits. Microfluidics-based approaches are instrumental to generate the knowledge necessary for the derivation of diverse neuronal cell types from human pluripotent stem cells, as they enable the isolation and subsequent examination of individual neurons of interest. Moreover, microfluidic devices allow to engineer neural circuits with specific orientations and directionality by providing control over neuronal cell polarity and permitting the isolation of axons in individual microchannels. Similarly, the use of microfluidic chips enables the construction not only of 2D but also of 3D brain, retinal, and peripheral nervous system model circuits. Such brain-on-a-chip and organoid-on-a-chip technologies are promising platforms for studying these organs as they closely recapitulate some aspects of in vivo biological processes. Microfluidic 3D neuronal models, together with 2D in vitro systems, are widely used in many applications ranging from drug development and toxicology studies to neurological disease modeling and personalized medicine. Altogether, microfluidics provide researchers with powerful systems that complement and partially replace animal models.

The role of hippocampal niche exosomes in rat hippocampal neurogenesis after fimbria-fornix transection

Exosomes transfer signaling molecules such as proteins, lipids, and RNAs to facilitate cell–cell communication and play an important role in the stem cell microenvironment. In previous work, we demonstrated that rat fimbria–fornix transection (FFT) enhances neurogenesis from neural stem cells (NSCs) in the subgranular zone (SGZ). However, how neurogenesis is modulated after denervation remains unknown. Here, we investigated whether exosomes in a denervated hippocampal niche may affect neurogenesis. Using the FFT rat model, we extracted hippocampal exosomes and identified them using western blots, transmission electron microscopy (TEM), and nanoparticle size measurement. We also used RNA sequencing and bioinformatic analysis of exosomes to identify noncoding RNA expression profiles and neurogenesis-related miRNAs, respectively. RNA sequencing analysis demonstrated 9 upregulated and 15 downregulated miRNAs. miR-3559-3P and miR-6324 increased gradually after FFT. Thus, we investigated the function of miR-3559-3P and miR-6324 with NSC proliferation and differentiation assays. Transfection of miR-3559-3p and miR-6324 mimics inhibited the proliferation of NSCs and promoted the differentiation of NSCs into neurons, while miR-3559-3p and miR-6324 inhibitors promoted NSC proliferation and inhibited neuronal differentiation. Additionally, the exosome marker molecules CD9, CD63, and Alix were expressed in exosomes extracted from the hippocampal niche. Finally, TEM showed that exosomes were ∼100 nm in diameter and had a “saucer-like” bilayer membrane structure. Taken together, these findings suggest that differentially expressed exosomes and their related miRNAs in the denervated hippocampal niche can promote differentiation of NSCs into neurons.

Genome Editing in Human Neural Stem and Progenitor Cells

Experimental tools for precise manipulation of mammalian genomes enable reverse genetic approaches to explore biology and disease. Powerful genome editing technologies built upon designer nucleases, such as CRISPR/Cas9, have recently emerged. Parallel progress has been made in methodologies for the expansion and differentiation of human pluripotent and tissue stem cells. Together these innovations provide a remarkable new toolbox for human cellular genetics and are opening up vast opportunities for discoveries and applications across the breadth of life sciences research. In this chapter, we review the emergence of genome editing technologies and how these are being deployed in studies of human neurobiology, neurological disease, and neuro-oncology. We focus our discussion on CRISPR/Cas9 and its application in studies of human neural stem and progenitor cells.

Polarity Induced in Human Stem Cell Derived Motoneurons on Patterned Self-Assembled Monolayers

The control of polarized human neurite/axon development at the single neuron level is critical in geographically directing signal propagation in engineered neural networks, for both in vitro and in vivo applications. While there is an increasing need to exert control over axonal growth for the successful development and establishment of integrative and functional in vitro systems, controlled, polarized distribution of either human-derived neurons or motoneurons in vitro has yet to be reported. In this study, we established the polarized distribution of stem cell derived human motoneurons, using a patterned surface, and maintained the cells in a serum-free system. A surface pattern with defined polarity was developed using self-assembled monolayers (SAMs). A cell permissive SAM, DETA (trimethoxysilyl propyldiethylenetri-amine), combined with photolithography and a nonpermissive fluorinated silane, 13F (tridecafluoro-1,1,2,2-tetrahydroctyl-1-dimethylchloro-silane), generated a surface where neurons only adhered to the designed attachment sites and did so with preferred orientation. In addition, 75% of the cells attached to the patterns were motoneurons compared to their percentage in the standard unpatterned surface which was used as a control condition (20%), demonstrating the preference of these human motoneurons in adhering to the patterns. The ability to dictate the distribution and polarity of human motoneurons will be essential to the engineering of human-based functional in vitro systems in which the control of signal propagation is necessary but more importantly for cell implantation studies. Such systems will greatly benefit the study of motor function as well as aid the development of high-throughput systems for drug screening and test beds for use in preclinical studies related to conditions such as spinal cord injury, ALS, and muscular dystrophy.

Isolation and characterization of GFAP-positive porcine neural stem/progenitor cells derived from a GFAP-CreERT2 transgenic piglet

Background

The porcine brain is gyrencephalic with similar gray and white matter composition and size more comparable to the human rather than the rodent brain; however, there is lack of information about neural progenitor cells derived from this model.

Results

Here, we isolated GFAP-positive porcine neural stem cells (NSCs) from the brain explant of a transgenic piglet, with expression of CreER^T2 under the control of the GFAP promoter (pGFAP-CreER^T2). The isolated pGFAP-CreER^T2 NSCs showed self-renewal and expression of representative NSC markers such as Nestin and Sox2. Pharmacological inhibition studies revealed that Notch1 signaling is necessary to maintain NSC identity, whereas serum treatment induced cell differentiation into reactive astrocytes and neurons.

Conclusions

Collectively, these results indicate that GFAP promoter-driven porcine CreER^T2 NSCs would be a useful tool to study neurogenesis of the porcine adult central nervous system and furthers our understanding of its potential clinical application in the future.

Graphical abstract

ᅟ

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1660-4) contains supplementary material, which is available to authorized users.

Identification of Neural Stem Cell Biomarkers by Isobaric Tagging for Relative and Absolute Quantitation (iTRAQ) Mass Spectrometry

This chapter describes a proteomic analysis of neural progenitor cells using isobaric tagging for relative and absolute quantitation (iTRAQ) mass spectrometry. A detailed procedure is described for the isolation, proliferation, and differentiation of these cells, including a comparative iTRAQ mass spectrometry analysis of the precursor and differentiated states. In total, there were changes in the levels of 55 proteins, many of which are not resolved easily by other proteomic methods. Therefore, this method should be useful for the identification of important regulatory molecules in the study of other precursor cells involved in neuronal or metabolic regulation in nutritional programming diseases.

A Two-Dimensional Difference Gel Electrophoresis (2D-DIGE) Protocol for Studies of Neural Precursor Cells

This chapter describes the basics of two-dimensional difference gel electrophoresis (2D-DIGE) for multiplex analysis of up to distinct proteomes. The example given describes the analysis of undifferentiated and differentiated neural precursor cells labelled with fluorescent Cy3 and Cy5 dyes in comparison to a pooled standard labelled with Cy2. After labelling, the proteomes are mixed together and electrophoresed on the same 2D gels. Scanning the gels at wavelengths specific for each dye allows direct overlay of the two different proteomes and the differences in abundance of specific protein spots can be determined through comparison to the pooled standard.

Approaches to Peripheral Nerve Repair: Generations of Biomaterial Conduits Yielding to Replacing Autologous Nerve Grafts in Craniomaxillofacial Surgery

Peripheral nerve injury is a common clinical entity, which may arise due to traumatic, tumorous, or even iatrogenic injury in craniomaxillofacial surgery. Despite advances in biomaterials and techniques over the past several decades, reconstruction of nerve gaps remains a challenge. Autografts are the gold standard for nerve reconstruction. Using autografts, there is donor site morbidity, subsequent sensory deficit, and potential for neuroma development and infection. Moreover, the need for a second surgical site and limited availability of donor nerves remain a challenge. Thus, increasing efforts have been directed to develop artificial nerve guidance conduits (ANCs) as new methods to replace autografts in the future. Various synthetic conduit materials have been tested in vitro and in vivo, and several first- and second-generation conduits are FDA approved and available for purchase, while third-generation conduits still remain in experimental stages. This paper reviews the current treatment options, summarizes the published literature, and assesses future prospects for the repair of peripheral nerve injury in craniomaxillofacial surgery with a particular focus on facial nerve regeneration.

A critical review of cell culture strategies for modelling intracortical brain implant material reactions

The capacity to predict in vivo responses to medical devices in humans currently relies greatly on implantation in animal models. Researchers have been striving to develop in vitro techniques that can overcome the limitations associated with in vivo approaches. This review focuses on a critical analysis of the major in vitro strategies being utilized in laboratories around the world to improve understanding of the biological performance of intracortical, brain-implanted microdevices. Of particular interest to the current review are in vitro models for studying cell responses to penetrating intracortical devices and their materials, such as electrode arrays used for brain computer interface (BCI) and deep brain stimulation electrode probes implanted through the cortex. A background on the neural interface challenge is presented, followed by discussion of relevant in vitro culture strategies and their advantages and disadvantages. Future development of 2D culture models that exhibit developmental changes capable of mimicking normal, postnatal development will form the basis for more complex accurate predictive models in the future. Although not within the scope of this review, innovations in 3D scaffold technologies and microfluidic constructs will further improve the utility of in vitro approaches.

Characterization of Apoptosis Signaling Cascades During the Differentiation Process of Human Neural ReNcell VM Progenitor Cells In Vitro

Apoptosis is an essential physiological process accompanying the development of the central nervous system and human neurogenesis. However, the time scale and the underlying molecular mechanisms are yet poorly understood. Due to this fact, we investigated the functionality and general inducibility of apoptosis in the human neural ReNcell VM progenitor cell line during differentiation and also after exposure to staurosporine (STS) and ultraviolet B (UVB) irradiation. Transmission light microscopy, flow cytometry, and Western-/Immunoblot analysis were performed to compare proliferating and differentiating, in addition to STS- and UVB-treated cells. In particular, from 24 to 72 h post-initiation of differentiation, G0/G1 cell cycle arrest, increased loss of apoptotic cells, activation of pro-apoptotic BAX, Caspase-3, and cleavage of its substrate PARP were observed during cell differentiation and, to a higher extent, after treatment with STS and UVB. We conclude that redundant or defective cells are eliminated by apoptosis, while otherwise fully differentiated cells were less responsive to apoptosis induction by STS than proliferating cells, likely as a result of reduced APAF-1 expression, and increased levels of BCL-2. These data provide the evidence that apoptotic mechanisms in the neural ReNcell VM progenitor cell line are not only functional, but also inducible by external stimuli like growth factor withdrawal or treatment with STS and UVB, which marks this cell line as a suitable model to investigate apoptosis signaling pathways in respect to the differentiation processes of human neural progenitor cells in vitro.

Effect of calcitonin gene-related peptide on the neurogenesis of rat adipose-derived stem cells in vitro

Calcitonin gene-related peptide (CGRP) promotes neuron recruitment and neurogenic activity. However, no evidence suggests that CGRP affects the ability of stem cells to differentiate toward neurogenesis. In this study, we genetically modified rat adipose-derived stem cells (ADSCs) with the CGRP gene (CGRP-ADSCs) and subsequently cultured in complete neural-induced medium. The formation of neurospheres, cellular morphology, and proliferative capacity of ADSCs were observed. In addition, the expression of the anti-apoptotic protein Bcl-2 and special markers of neural cells, such as Nestin, MAP2, RIP and GFAP, were evaluated using Western blot and immunocytochemistry analysis. The CGRP-ADSCs displayed a greater proliferation than un-transduced (ADSCs) and Vector-transduced (Vector-ADSCs) ADSCs (p<0.05), and lower rates of apoptosis, associated with the incremental expression of Bcl-2, were also observed for CGRP-ADSCs. Moreover, upon neural induction, CGRP-ADSCs formed markedly more and larger neurospheres and showed round cell bodies with more branching extensions contacted with neighboring cells widely. Furthermore, the expression levels of Nestin, MAP2, and RIP in CGRP-ADSCs were markedly increased, resulting in higher levels than the other groups (p<0.05); however, GFAP was distinctly undetectable until day 7, when slight GFAP expression was detected among all groups. Wnt signals, primarily Wnt 3a, Wnt 5a and β-catenin, regulate the neural differentiation of ADSCs, and CGRP gene expression apparently depends on canonical Wnt signals to promote the neurogenesis of ADSCs. Consequently, ADSCs genetically modified with CGRP exhibit stronger potential for differentiation and neurogenesis in vitro, potentially reflecting the usefulness of ADSCs as seed cells in therapeutic strategies for spinal cord injury.

Isolamento e cultivo de neurônios e neuroesferas de córtex cerebral aviar

Métodos de cultivo celular são convenientes na realização de análises funcionais de alterações/interações protéicas das células neuronais, auxiliando a decifrar o interactoma de proteínas chaves na neurogênese de doenças do Sistema Nervoso Central. Por esse motivo, culturas de neurônios e neuroesferas isolados do córtex cerebral aviar representam um modelo acessível para o estudo de diversas doenças neurológicas, tal como a epilepsia. A espécie aviar apresenta peculiaridades em seu proteoma neuronal, visto a presença de uma expressão diferenciada de proteínas chaves no metabolismo energético cerebral, algumas destas (VDAC1 e VDAC2) desempenham papel importante na compreensão do mecanismo da epilepsia refratária. A metodologia estabelecida no presente estudo obteve cultivo de neuroeferas, onde as células cresceram tipicamente em aglomerados atingindo, dentro de 7 dias, o diâmetro ideal de 100-200 µm. A diferenciação celular das neuroesferas foi obtida após a aderência destas às placas tratadas com poli-D-lisina, evidenciada pela migração de fibras do interior da neuroesfera. Ao contrário das neuroesferas, os neurônios em cultivo extenderam seus neuritos após 11 dias de isolamento. Tal modelo in vitro pode ser utilizado com sucesso na identificação das variáveis neuroproteômicas, propiciando uma avaliação global das alterações dinâmicas e suas interações protéicas. Tal modelo pode ter aplicações em estudos dos efeitos de indutores da morte celular e bloqueadores de canais de membrana mitocondriais em proteínas chaves do metabolismo energético cerebral.

Neural stem cell-based treatment for neurodegenerative diseases

Human neurodegenerative diseases such as Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD) are caused by a loss of neurons and glia in the brain or spinal cord. Neurons and glial cells have successfully been generated from stem cells such as embryonic stem cells (ESCs), mesenchymal stem cells (MSCs) and neural stem cells (NSCs), and stem cell-based cell therapies for neurodegenerative diseases have been developed. A recent advance in generation of a new class of pluripotent stem cells, induced pluripotent stem cells (iPSCs), derived from patients' own skin fibroblasts, opens doors for a totally new field of personalized medicine. Transplantation of NSCs, neurons or glia generated from stem cells in animal models of neurodegenerative diseases, including PD, HD, ALS and AD, demonstrates clinical improvement and also life extension of these animals. Additional therapeutic benefits in these animals can be provided by stem cell-mediated gene transfer of therapeutic genes such as neurotrophic factors and enzymes. Although further research is still needed, cell and gene therapy based on stem cells, particularly using neurons and glia derived from iPSCs, ESCs or NSCs, will become a routine treatment for patients suffering from neurodegenerative diseases and also stroke and spinal cord injury.

In vivo bioluminescence reporter gene imaging for the activation of neuronal differentiation induced by the neuronal activator neurogenin 1 (Ngn1) in neuronal precursor cells

PURPOSE

Facilitation of the ability of neuronal lineages derived from transplanted stem cells to differentiate is essential to improve the low efficacy of neuronal differentiation in stem cell therapy in vivo. Neurogenin 1 (Ngn1), a basic helix-loop-helix factor, has been used as an activator of neuronal differentiation. In this study, we monitored the in vivo activation of neuronal differentiation by Ngn1 in neuronal precursor cells using neuron-specific promoter-based optical reporters.

METHODS

The NeuroD promoter coupled with the firefly luciferase reporter system (pNeuroD-Fluc) was used to monitor differentiation in F11 neuronal precursor cells. In vitro luciferase activity was measured and normalized by protein content. The in vivo-jetPEI(TM) system was used for in vivo transgene delivery. The IVIS 100 imaging system was used to monitor in vivo luciferase activity.

RESULTS

The Ngn1-induced neuronal differentiation of F11 cells generated neurite outgrowth within 2 days of Ngn1 induction. Immunofluorescence staining demonstrated that early and late neuronal marker expression (βIII-tubulin, NeuroD, MAP2, NF-M, and NeuN) was significantly increased at 3 days after treatment with Ngn1. When Ngn1 and the pNeuroD-Fluc vector were cotransfected into F11 cells, we observed an approximately 11-fold increase in the luciferase signal. An in vivo study showed that bioluminescence signals were gradually increased in Ngn1-treated F11 cells for up to 3 days.

CONCLUSION

In this study, we examined the in vivo tracking of neuronal differentiation induced by Ngn1 using an optical reporter system. This reporter system could be used effectively to monitor the activation efficiency of neuronal differentiation in grafted stem cells treated with Ngn1 for stem cell therapy.

High glucose induces apoptosis and suppresses proliferation of adult rat neural stem cells following in vitro ischemia

Background

Post-stroke hyperglycemia appears to be associated with poor outcome from stroke, greater mortality, and reduced functional recovery. Focal cerebral ischemia data support that neural stem cells (NSCs) play an important role in post-ischemic repair. Here we sought to evaluate the negative effects of hyperglycemia on the cellular biology of NSCs following anoxia, and to test whether high glucose affects NSC recovery from ischemic injury.

Results

In this study, we used immortalized adult neural stem cells lines and we induced in vitro ischemia by 6 h oxygen and glucose deprivation (OGD) in an anaerobic incubator. Reperfusion was performed by returning cells to normoxic conditions and the cells were then incubated in experimental medium with various concentrations of glucose (17.5, 27.75, 41.75, and 83.75 mM) for 24 h. We found that high glucose (≥27.75 mM) exposure induced apoptosis of NSCs in a dose-dependent manner after exposure to OGD, using an Annexin V/PI apoptosis detection kit. The cell viability and proliferative activity of NSCs following OGD in vitro, evaluated with both a Cell Counting kit-8 (CCK-8) assay and a 5-ethynyl-2’-deoxyuridine (EdU) incorporation assay, were inhibited by high glucose exposure. Cell cycle analysis showed that high glucose exposure increased the percentage of cells in G0/G1-phase, and reduced the percentage of cells in S-phase. Furthermore, high glucose exposure was found to significantly induce the activation of c-Jun N-terminal protein kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) and suppress extracellular signal-regulated kinase 1/2 (ERK1/2) activity.

Conclusions

Our results demonstrate that high glucose induces apoptosis and inhibits proliferation of NSCs following OGD in vitro, which may be associated with the activation of JNK/p38 MAPK pathways and the delay of G1-S transition in the cells.

Modeling to optimize terminal stem cell differentiation

Embryonic stem cell (ESC), iPCs, and adult stem cells (ASCs) all are among the most promising potential treatments for heart failure, spinal cord injury, neurodegenerative diseases, and diabetes. However, considerable uncertainty in the production of ESC-derived terminally differentiated cell types has limited the efficiency of their development. To address this uncertainty, we and other investigators have begun to employ a comprehensive statistical model of ESC differentiation for determining the role of intracellular pathways (e.g., STAT3) in ESC differentiation and determination of germ layer fate. The approach discussed here applies the Baysian statistical model to cell/developmental biology combining traditional flow cytometry methodology and specific morphological observations with advanced statistical and probabilistic modeling and experimental design. The final result of this study is a unique tool and model that enhances the understanding of how and when specific cell fates are determined during differentiation. This model provides a guideline for increasing the production efficiency of therapeutically viable ESCs/iPSCs/ASC derived neurons or any other cell type and will eventually lead to advances in stem cell therapy.

Neural differentiation of rat adipose-derived stem cells in vitro

It is reported that adipose-derived stem cells (ADSCs) had multilineage differentiation potential, and could differentiate into neuron-like cells induced by special induction media, which may provide a new idea for restoration of erectile dysfunction (ED) after cavernous nerve injury. The aim of this research was to explore the neuronal differentiation potential of ADSCs in vitro. ADSCs isolated from inguinal adipose tissue of rat were characterized by flow cytometry, and results showed that ADSCs were positive for mesenchymal stem cell markers CD90 and CD44, but negative for hematopoietic stem cell markers. ADSCs maintained self-renewing capacity and could differentiate into adipocytes and neurocytes under special culture condition. In this research, two methods were used to induce ADSCs. In method 1, ADSCs were treated with the preinduction medium including epithelium growth factor, basic fibroblast growth factor, and brain derived neurotrophic factor (BDNF) for 3 days, then with the neurogenic induction medium containing isobutylmethylxanthine, indomethacin, and insulin. While in method 2, BDNF was not used to treat ADSCs. After induction, neuronal differentiation of ADSCs was evaluated. Neuronal markers, glial fibrillary acidic protein (GFAP), and β-tubulin III (Tuj-1) were detected by immunofluorescence and Western Blot analyses. The expressions of GFAP and Tuj-1 in method 1 were obviously higher then those in method 2. In addition, the positive rate of the neuron-like cells was higher in method 1. It suggested that ADSCs are able to differentiate into neural-like cells in vitro, and the administration of BDNF in the preinduction medium may provide a new way to modify the culture method for getting more neuron-like cells in vitro.

G-protein-coupled receptors in adult neurogenesis

The importance of adult neurogenesis has only recently been accepted, resulting in a completely new field of investigation within stem cell biology. The regulation and functional significance of adult neurogenesis is currently an area of highly active research. G-protein-coupled receptors (GPCRs) have emerged as potential modulators of adult neurogenesis. GPCRs represent a class of proteins with significant clinical importance, because approximately 30% of all modern therapeutic treatments target these receptors. GPCRs bind to a large class of neurotransmitters and neuromodulators such as norepinephrine, dopamine, and serotonin. Besides their typical role in cellular communication, GPCRs are expressed on adult neural stem cells and their progenitors that relay specific signals to regulate the neurogenic process. This review summarizes the field of adult neurogenesis and its methods and specifies the roles of various GPCRs and their signal transduction pathways that are involved in the regulation of adult neural stem cells and their progenitors. Current evidence supporting adult neurogenesis as a model for self-repair in neuropathologic conditions, adult neural stem cell therapeutic strategies, and potential avenues for GPCR-based therapeutics are also discussed.

Recent therapeutic strategies for spinal cord injury treatment: possible role of stem cells

Spinal cord injury (SCI) often results in significant dysfunction and disability. A series of treatments have been proposed to prevent and overcome the formation of the glial scar and inhibitory factors to axon regrowth. In the last decade, cell therapy has emerged as a new tool for several diseases of the nervous system. Stem cells act as minipumps providing trophic and immunomodulatory factors to enhance axonal growth, to modulate the environment, and to reduce neuroinflammation. This capability can be boosted by genetical manipulation to deliver trophic molecules. Different types of stem cells have been tested, according to their properties and the therapeutic aims. They differ from each other for origin, developmental stage, stage of differentiation, and fate lineage. Related to this, stem cells differentiating into neurons could be used for cell replacement, even though the feasibility that stem cells after transplantation in the adult lesioned spinal cord can differentiate into neurons, integrate within neural circuits, and emit axons reaching the muscle is quite remote. The timing of cell therapy has been variable, and may be summarized in the acute and chronic phases of disease, when stem cells interact with a completely different environment. Even though further experimental studies are needed to elucidate the mechanisms of action, the therapeutic, and the side effects of cell therapy, several clinical protocols have been tested or are under trial. Here, we report the state-of-the-art of cell therapy in SCI, in terms of feasibility, outcome, and side effects.

NeuriteQuant: an open source toolkit for high content screens of neuronal morphogenesis

Background

To date, some of the most useful and physiologically relevant neuronal cell culture systems, such as high density co-cultures of astrocytes and primary hippocampal neurons, or differentiated stem cell-derived cultures, are characterized by high cell density and partially overlapping cellular structures. Efficient analytical strategies are required to enable rapid, reliable, quantitative analysis of neuronal morphology in these valuable model systems.

Results

Here we present the development and validation of a novel bioinformatics pipeline called NeuriteQuant. This tool enables fully automated morphological analysis of large-scale image data from neuronal cultures or brain sections that display a high degree of complexity and overlap of neuronal outgrowths. It also provides an efficient web-based tool to review and evaluate the analysis process. In addition to its built-in functionality, NeuriteQuant can be readily extended based on the rich toolset offered by ImageJ and its associated community of developers. As proof of concept we performed automated screens for modulators of neuronal development in cultures of primary neurons and neuronally differentiated P19 stem cells, which demonstrated specific dose-dependent effects on neuronal morphology.

Conclusions

NeuriteQuant is a freely available open-source tool for the automated analysis and effective review of large-scale high-content screens. It is especially well suited to quantify the effect of experimental manipulations on physiologically relevant neuronal cultures or brain sections that display a high degree of complexity and overlap among neurites or other cellular structures.

In vitro development of nuclear transfer embryos derived from porcine embryonic germ cells and their descendent neural precursor cells

Undifferentiated stem cells may support a greater development of cloned embryos compared with differentiated cell types due to their ease of reprogramming during the nuclear transfer (NT) process. Hence, stem cells may be more suitable as nuclear donor cells for NT procedures than are somatic cells. Embryonic germ (EG) cells are undifferentiated stem cells that are isolated from cultured primordial germ cells (PGC) and can differentiate into several cell types. In this study, the in vitro development of NT embryos using porcine EG cells and their derivative neural precursor (NP) cells was investigated, thus eliminating any variation in genetic differences. The rates of fusion did not differ between NT embryos from EG and NP cells; however, the rate of cleavage in NT embryos derived from EG cells was significantly higher (p < 0.05) than that from NP cells (141/247 [57.1%] vs. 105/228 [46.1%]). Similarly, the rate of blastocyst development was significantly higher (P < 0.05) in NT using EG cells than the rate using NP cells (43/247 [17.4%] vs. 18/228 [7.9%]). The results obtained from the present study in pigs demonstrate a reduced capability for nuclear donor cells to be reprogrammed following the differentiation of porcine EG cells. Undifferentiated EG cells may be more amenable to reprogramming after reconstruction compared with differentiated somatic cells.

Activity-dependent long-term plasticity of afferent synapses on grafted stem/progenitor cell-derived neurons

Stem cell-based cell replacement therapies aiming at restoring injured or diseased brain function ultimately rely on the capability of transplanted cells to promote functional recovery. The mechanisms by which stem cell-based therapies for neurological conditions can lead to functional recovery are uncertain, but structural and functional repair appears to depend on integration of transplanted cell-derived neurons into neuronal circuitries. The nature by which stem/progenitor cell-derived neurons synaptically integrate into neuronal circuitries is largely unexplored. Here we show that transplanted GFP-labeled neuronal progenitor cells into the rat hippocampus exhibit mature neuronal morphology following 4-10 weeks. GFP-positive cells were preferentially integrated into the principal cell layers of hippocampus, particularly CA3. Patch-clamp recordings from GFP-expressing cells revealed that they generated fast action potentials, and their intrinsic membrane properties were overall similar to endogenous host neurons recorded in same areas. As judged by occurrence of spontaneous excitatory postsynaptic currents (EPSCs), transplanted GFP-positive cells were synaptically integrated into the host circuitry. Comparable to host neurons, both paired-pulse depression and facilitation of afferent fiber stimulation-evoked EPSCs were observed in GFP-positive cells. Upon high-frequency stimulation, GFP-positive cells displayed post-tetanic potentiation of EPSCs, in some cases followed by long-term potentiation (LTP) lasting for more than 30 min. Our data show for the first time that transplanted neuronal progenitor cells can become functional neurons and their afferent synapses are capable of expressing activity-dependent short and long-term plasticity. These synaptic properties may facilitate host-to-graft interactions and regulate activity of the grafted cells promoting functional recovery of the diseased brain.

Glypican-1, phosphacan/receptor protein-tyrosine phosphatase-ζ/β and its ligand, tenascin-C, are expressed by neural stem cells and neural cells derived from embryonic stem cells

The heparan sulfate proteoglycan glypican-1, the chondroitin sulfate proteoglycan phosphacan/RPTP (receptor protein-tyrosine phosphatase)-ζ/β and the extracellular matrix protein tenascin-C were all found to be expressed by neural stem cells and by neural cells derived from them. Expression of proteoglycans and tenascin-C increased after retinoic acid induction of SSEA1-positive ES (embryonic stem) cells to nestin-positive neural stem cells, and after neural differentiation, proteoglycans and tenascin-C are expressed by both neurons and astrocytes, where they surround cell bodies and processes and in certain cases show distinctive expression patterns. With the exception of tenascin-C (whose expression may decrease somewhat), expression levels do not change noticeably during the following 2 weeks in culture. The significant expression, by neural stem cells and neurons and astrocytes derived from them, of two major heparan sulfate and chondroitin sulfate proteoglycans of nervous tissue and of tenascin-C, a high-affinity ligand of phosphacan/RPTP-ζ/β, indicates that an understanding of their specific functional roles in stem cell neurobiology will be important for the therapeutic application of this new technology in facilitating nervous tissue repair and regeneration.

Expression of hyaluronan and the hyaluronan-binding proteoglycans neurocan, aggrecan, and versican by neural stem cells and neural cells derived from embryonic stem cells

We have examined the expression and localization patterns of hyaluronan and hyaluronan-binding chondroitin sulfate proteoglycans in neural stem cells and differentiated neural cells derived from mouse embryonic stem cells. Expression of proteoglycans and hyaluronan was weak in the SSEA1-positive embryonic stem cells but increased noticeably after retinoic acid induction to nestin-positive neural stem cells. After subsequent plating, the hyaluronan-binding chondroitin sulfate proteoglycans aggrecan, neurocan, and versican are expressed by cells in both the astrocytic and neuronal lineages. During the time period that hyaluronan was present, it co-localized with each of the hyaluronan-binding proteoglycans studied and was found to be clearly associated with beta-III tubulin-expressing neurons and oligodendrocytes expressing the O4 sulfatide marker. Although proteoglycan expression levels increased to varying degrees following neural differentiation, they did not change noticably during the following 2 weeks in culture, but there was a significant decrease in hyaluronan expression. Our studies therefore demonstrate the expression by neural stem cells and neural cells derived from them of hyaluronan and its associated proteoglycans, thereby providing a necessary foundation for integrating their specific properties into developing strategies for therapeutic applications.

Neurogenic differentiation of murine adipose derived stem cells transfected with EGFP in vitro

Some studies indicate that adipose derived stem cells (ADSCs) can differentiate into adipogenic, chondrogenic, myogenic, and osteogenic cells in vitro. However, whether ADSCs can be induced to differentiate into neural cells in vitro has not been clearly demonstrated. In this study, the ADSCs isolated from the murine adipose tissue were cultured and transfected with the EGFP gene, and then the cells were induced for neural differentiation. The morphology of those ADSCs began to change within two days which developed into characteristics of round cell bodies with several branching extensions, concomitantly expressing EGFP fluorescence. Approximately 60% of the total cell populations were bipolar or multipolar in shape. Some of them appeared to make contact with their neighboring cells. RT-PCR, Western blot and Immunocytochemistry revealed that the expression levels of the markers of neurons and oligodendrocytes such as MAP2, NF-70, Neu N and RIP upon neural induction were increased, but the expression of the special marker of astrocytes, GFAP, was undetectable until 96 h after induction when a small signal was observed. It was concluded that the ADSCs transfected with EGFP possessed the ability to undergo morphologic and phenotypic changes consistent with neural differentiation in vitro. It suggests that these cells might provide an ideal source for further stem cell research with possible therapeutic application for spinal cord injury.

Stem cell-based cell therapy in neurological diseases: a review

Human neurological disorders such as Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis (ALS), Alzheimer's disease, multiple sclerosis (MS), stroke, and spinal cord injury are caused by a loss of neurons and glial cells in the brain or spinal cord. Cell replacement therapy and gene transfer to the diseased or injured brain have provided the basis for the development of potentially powerful new therapeutic strategies for a broad spectrum of human neurological diseases. However, the paucity of suitable cell types for cell replacement therapy in patients suffering from neurological disorders has hampered the development of this promising therapeutic approach. In recent years, neurons and glial cells have successfully been generated from stem cells such as embryonic stem cells, mesenchymal stem cells, and neural stem cells, and extensive efforts by investigators to develop stem cell-based brain transplantation therapies have been carried out. We review here notable experimental and preclinical studies previously published involving stem cell-based cell and gene therapies for Parkinson's disease, Huntington's disease, ALS, Alzheimer's disease, MS, stroke, spinal cord injury, brain tumor, and lysosomal storage diseases and discuss the future prospects for stem cell therapy of neurological disorders in the clinical setting. There are still many obstacles to be overcome before clinical application of cell therapy in neurological disease patients is adopted: 1) it is still uncertain what kind of stem cells would be an ideal source for cellular grafts, and 2) the mechanism by which transplantation of stem cells leads to an enhanced functional recovery and structural reorganization must to be better understood. Steady and solid progress in stem cell research in both basic and preclinical settings should support the hope for development of stem cell-based cell therapies for neurological diseases.

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.

Applications of neural and mesenchymal stem cells in the treatment of gliomas

In addition to stem cells providing a better understanding about the biology and origins of gliomas, new therapeutic approaches have been developed based on the use of stem cells as delivery vehicles. The unique ability of stem cells to track down tumor cells makes them a very appealing therapeutic modality. This review introduces neural and mesenchymal stem cells, discusses the advances that have been made in the utilization of these stem cells as therapies and in diagnostic imaging (to track the advancement of the stem cells towards the tumor cells), and concludes by addressing various challenges and concerns regarding these therapies.

Defining a Developmental Path to Neural Fate by Global Expression Profiling of Mouse Embryonic Stem Cells and Adult Neural Stem/Progenitor Cells

To understand global features of gene expression changes during in vitro neural differentiation, we carried out the microarray analysis of embryonic stem cells (ESCs), embryonal carcinoma cells, and adult neural stem/progenitor (NS) cells. Expression profiling of ESCs during differentiation in monolayer culture revealed three distinct phases: undifferentiated ESCs, primitive ectoderm-like cells, and neural progenitor cells. Principal component (PC) analysis revealed that these cells were aligned on PC1 over the course of 6 days. This PC1 represents approximately 4,000 genes, the expression of which increased with neural commitment/differentiation. Furthermore, NS cells derived from adult brain and their differentiated cells were positioned along this PC axis further away from undifferentiated ESCs than embryonic stem-derived neural progenitors. We suggest that this PC1 defines a path to neural fate, providing a scale for the degree of commitment/differentiation.

Production, characterization, and efficient transfection of highly pure oligodendrocyte precursor cultures from mouse embryonic neural progenitors

Much current knowledge of oligodendrocyte biology, the myelin-forming cells in the central nervous system, comes from cell culture studies mainly from postnatal rat tissue but mouse cells have been much more difficult to produce in large quantities. We have developed a high yield protocol for production of oligodendrocyte precursor cells from mouse embryonic neural progenitors grown as neurospheres. Neurospheres can be maintained and expanded for long periods in culture in the presence of epidermal growth factor (EGF). When floating neurospheres were plated on substrate-coated dishes in media supplemented with platelet derived growth factor (PDGF) and basic fibroblast growth factor (bFGF), the spheres attached and generated migrating cells that were predominantly oligodendrocyte-lineage cells. Furthermore, cells in spheres could be shifted to the oligodendrocyte phenotype prior to plating on substrate, by incubation in suspension with PDGF/bFGF. Single cell suspensions plated after dissociation of either EGF-treated neurospheres or PDGF/bFGF-treated oligospheres had the bipolar, elongated morphology characteristic of oligodendrocyte precursor cells. mRNA and protein expression analysis of the cells generated by this method confirmed their oligodendrocyte lineage. Oligodendrocyte precursors generated by this method matured in response to ciliary neurotrophic factor treatment, producing cells with multiple processes and myelin-like membranes. The most important aspect of this protocol is the ability to generate very high numbers of relatively pure mouse oligodendrocyte progenitor cells, which can be easily transfected. These studies open up many kinds of investigations on transgenic and mutant mouse oligodendrocytes, thereby providing a valuable tool to study oligodendrocyte biology and development.

Setting the conditions for efficient, robust and reproducible generation of functionally active neurons from adult subventricular zone-derived neural stem cells

Although new culture conditions enable homogeneous and long-term propagation of radial glia-like neural stem (NS) cells in monolayer and serum-free conditions, the efficiency of the conversion of NS cells into terminally differentiated, functionally mature neurons is relatively limited and poorly characterized. We demonstrate that NS cells derived from adult mouse subventricular zone robustly develop properties of mature neurons when exposed to an optimized neuronal differentiation protocol. A high degree of cell viability was preserved. At 22 days in vitro, most cells (65%) were microtubule-associated protein 2(+) and coexpressed gamma-aminobutyric acid (GABA), GAD67, calbindin and parvalbumin. Nearly all neurons exhibited sodium, potassium and calcium currents, and 70% of them fired action potentials. These neurons expressed functional GABA(A) receptors, whereas activable kainate, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and N-methyl-D-aspartic acid receptors were present in approximately 80, 30 and 2% of cells, respectively. Antigenic and functional properties were efficiently and reliably reproduced across experiments and cell passages (up to 68). This is the first report showing a consistent and reproducible generation of large amounts of neurons from long-term passaged adult neural stem cells. Remarkably, the neuronal progeny carries a defined set of antigenic, biochemical and functional characteristics that make this system suitable for studies of NS cell biology as well as for genetic and chemical screenings.

Neural stem/progenitor cells promote endothelial cell morphogenesis and protect endothelial cells against ischemia via HIF-1alpha-regulated VEGF signaling

Vascular cells provide a neural stem/progenitor cell (NSPC) niche that regulates expansion and differentiation of NSPCs within the germinal zones of the embryonic and adult brain under both physiologic and pathologic conditions. Here, we examined the NSPC-endothelial cell (NSPC/EC) interaction under conditions of ischemia, both in vitro and after intracerebral transplantation. In culture, embryonic mouse NSPCs supported capillary morphogenesis and protected ECs from cell death induced by serum starvation or by transient oxygen and glucose deprivation (OGD). Neural stem/progenitor cells constitutively expressed hypoxia-inducible factor 1alpha (HIF-1alpha) transcription factor and vascular endothelial growth factor (VEGF), both of which were increased approximately twofold after the exposure of NSPCs to OGD. The protective effects of NSPCs on ECs under conditions of serum starvation and hypoxia were blocked by pharmacological inhibitors of VEGF signaling, SU1498 and Flt-1-Fc. After intracerebral transplantation, NSPCs continued to express HIF-1alpha and VEGF, and promoted microvascular density after focal ischemia. These studies support a role for NSPCs in stabilization of vasculature during ischemia, mediated via HIF-1alpha-VEGF signaling pathways, and suggest therapeutic application of NSPCs to promote revascularization and repair after brain injury.

Production and characterization of immortal human neural stem cell line with multipotent differentiation property

We document the protocols and methods for the production of immortalized cell lines of human neural stem cells from the human fetal central nervous system (CNS) cells by using a retroviral vector encoding v-myc oncogene. One of the human neural stem cell lines (HB1.F3) was found to express nestin and other specific markers for human neural stem cells, giving rise to three fundamental cell types of the CNS: neurons, astrocytes, and oligodendrocytes. After transplantation into the brain of mouse model of stroke, implanted human neural stem cells were observed to migrate extensively from the site of implantation into other anatomical sites and to differentiate into neurons and glial cells.

Novel and immortalization-based protocols for the generation of neural CNS stem cell lines for gene therapy approaches

Transplantation of neural cells engineered to produce growth factors or molecules with antitumor effects have the potential of grafted cells to be used as vectors for protein delivery in animal models of diseases. In this context, neural stem cells (NSCs), since their identification, have been considered an attractive subject for therapeutic applications to the damaged brain. NSCs have been shown to include attributes important for potential successful ex vivo gene therapy approaches: they show extensive in vitro expansion and, in some cases, a particular tropism toward pathological brain areas. Clearly, the challenges for future clinical development of this approach are in the definition of the most appropriate stem cells for a given application, what genes or chemicals can be delivered, and what diseases are suitable targets. Ideally, NSC lines should be homogeneous and well characterized in terms of their in vitro stability and grafting capacity. We discuss two possible approaches to produce homogeneous and stable progenitor and NSC lines that exploit an oncogene-based immortalization, or, in the second case, a novel protocol for growth factor expansion of stem cells with radial glia-like features. Furthermore, we describe the use of retroviral particles for genetic engineering.

Constant-current adjustable-waveform microstimulator for an implantable hybrid neural prosthesis

Microstimulation of neural tissue has become a widely-used technique for controlling neuronal responses with local electric fields as well as a therapeutic intervention for nervous system disorders such as epilepsy and Parkinson's disease. Of those afflicted by neurological diseases, many are or become tolerant to existing pharmaceuticals and are left with little recourse. Little is known about the necessary design criteria or efficacy of a hybrid neural prosthesis. Assessment of the potential clinical value of a hybrid electro-chemical neural prosthesis was performed through in vitro verification using a prototype microstimulator and P19 cell cultures. We constructed a printed circuit board (PCB) microstimulator as a prototype of a CMOS microstimulator ASIC that was subsequently fabricated in the IBM 7RF 0.18 microm process. Measured results for the prototype are described in this work. An output impedance of 237 kOmega, voltage compliance of 11.3 V, and a linear constant-current output up to +/-600 microA make this microstimulator system a viable option for an implantable hybrid neural prosthesis. Hybrid prostheses could uniquely affect neural modulation with linear glutamate release at physiological amplitudes and frequencies.

Role of DNA topoisomerase IIβ in neurite outgrowth

Failure to establish neuromuscular junctions is a major phenotype of top2beta knockout mice. However, the precise mechanism for this defect is not known. In the current study, we have investigated the role of TopIIbeta in cultured neurons. We showed that the TopII inhibitor ICRF-193 significantly blocked neurite outgrowth and growth cone formation in cultured cerebellar granule neurons (CGNs), dorsal root ganglions (DRGs) and cortical neurons (CNs). In addition, ICRF-193 also blocked neurite outgrowth and growth cone formation of PC12 cells undergoing NGF-induced differentiation. Isolated cortical neurons from top2beta knockout embryos elaborated shorter neurites than did those from their wild type counterparts, confirming the role of TopIIbeta in neurite outgrowth. Together, these results demonstrate a critical role of TopIIbeta in neurite outgrowth in cultured neurons. Furthermore, we demonstrated that neurons derived from top2beta knockout mice failed to form contacts with muscle cells in co-cultures. These results suggest that the defect in establishing neuromuscular junctions in top2beta knockout mice could be due to the lack of TopIIbeta-mediated neurite outgrowth.

Neural stem cells for the treatment of disorders of the enteric nervous system: strategies and challenges

The main goal of this review is to summarize the status of the research in the field of stem cells transplantation, as it is applicable to the treatment of gastrointestinal motility. This field of research has advanced tremendously in the past 10 years, and recent data produced in our laboratories as well as others is contributing to the excitement on the use of neural stem cells (NSC) as a valuable therapeutic approach for disorders of the enteric nervous system characterized by a loss of critical neuronal subpopulations. There are several sources of NSC, and here we describe therapeutic strategies for NSC transplantation in the gut. These include using NSC as a relatively nonspecific cellular replacement strategy in conditions where large populations of neurons or their subsets are missing or destroyed. As with many other recent "breakthroughs" stem cell therapy may eventually prove to be overrated. However, at the present time, it does appear to provide the hope for a true cure for many currently intractable diseases of both the central and the peripheral nervous system. Certainly more extensive research is needed in this field. We hope that our review will encourage new investigators in entering this field of research ad contribute to our knowledge of the potentials of NSC and other cells for the treatment of gastrointestinal dysmotility.

Genetically engineered human neural stem cells for brain repair in neurological diseases

Neural stem cells (NSCs)of the central nervous system (CNS) have recently received a great deal of attention and interest for their therapeutic potential for neurological disorders. NSCs are defined as CNS progenitor cells that have the capacity for self-renewal and multipotent potential to become neurons or glial cells. Recent studies have shown that NSCs isolated from mammalian CNS including human can be propagated in vitro and then implanted into the brain of animal models of human neurological disorders. Recently, we have generated clonally derived immortalized human NSC cell lines via a retroviral vector encoded with v-myc oncogene. One of the human NSC lines, HB1.F3, was utilized in stem-cell based therapy in animal models of human neurological disorders. When F3 human NSCs were implanted into the brain of murine models of lysosomal storage diseases, stroke, Parkinson disease, Huntington disease or stroke, implanted F3 NSCs were found to migrate to the lesion sites, differentiate into neurons and glial cells, and restore functional deficits found in these neurological disorders. In animal models of brain tumors, F3 NSCs could deliver a bioactive therapeutically relevant molecules to effect a significant anti-tumor response intracranial tumor mass. Since these genetically engineered human NSCs are immortalized and continuously multiplying, there would be limitless supply of human neurons for treatment for patients suffering from neurological disorders including stroke, Parkinson disease, Huntington disease, ALS, multiple sclerosis and spinal cord injury. The promising field of stem cell research as it applies to regenerative medicine is still in infancy, but its potential appears limitless, and we are blessed to be involved in this exciting realm of research.

Identification of Proteomic Changes during Differentiation of Adult Mouse Subventricular Zone Progenitor Cells

The use of neural precursor cells (NPCs) represents a promising repair strategy for many neurological disorders. However, the molecular events and biological features that control NPC proliferation and their differentiation into neurons, astrocytes, and oligodendrocytes are unclear. In the present study, we used a comparative proteomics approach to identify proteins that were differentially regulated in NPCs after short-term differentiation. We also used a subcellular fractionation technique for enrichment of nuclei and other dense organelles to identify proteins that were not readily detected in whole cell extracts. In total, 115 distinct proteins underwent expression changes during NPC differentiation. Forty one of these were only identified following subcellular fractionation. These included transcription factors, RNA-processing factors, cell cycle proteins, and proteins that translocate between the nucleus and cytoplasm. Biological network analysis showed that the differentiation of NPCs was associated with significant changes in cell cycle and protein synthesis machinery. Further characterization of these proteins could provide greater insight into the mechanisms involved in regulation of neurogenesis in the adult central nervous system (CNS) and potentially identify points of therapeutic intervention.

Neural stem cell therapy for neuropsychiatric disorders

OBJECTIVE

To conduct a comprehensive literature review of the area of neural stem cells and neuropsychiatry.

METHODS

'Neural stem cells' (NSCs) and 'neurogenesis' were used as keywords in Medline (1966 - November 2006) to identify relevant papers in the areas of Alzheimer's disease (AD), depression, schizophrenia and Parkinson's disease (PD). This list was supplemented with papers from reference lists of seminal reviews.

RESULTS

The concept of a 'stem cell' continues to evolve and is currently defined by operational criteria related to symmetrical renewal, multipotency and functional viability. In vivo adult mammalian neurogenesis occurs in discrete niches in the subventricular and subgranular zones - however, functional precursor cells can be generated in vitro from a wide variety of biological sources. Both artificial and physiological microenvironment is therefore critical to the characteristics and behaviour of neural precursors, and it is not straightforward how results from the laboratory can be extrapolated to the living organism. Transplant strategies in PD have shown that it is possible for primitive neural tissue to engraft into neuropathic brain areas, become biologically functional and lead to amelioration of clinical signs and symptoms. However, with long-term follow-up, significant problems related to intractable side-effects and potential neoplastic growth have been reported. These are therefore the potentials and pitfalls for NSC technology in neuropsychiatry. In AD, the physiology of amyloid precursor protein may directly interact with NSCs, and a role in memory function has been speculated. The role of endogenous neurogenesis has also been implicated in the etiology of depression. The significance of NSCs and neurogenesis for schizophrenia is still emerging.

CONCLUSIONS

There are a number of technical and conceptual challenges ahead before the promise of NSCs can be harnessed for the understanding and treatment of neuropsychiatric disorders. Further research into fundamental NSC biology and how this interacts with the neuropsychiatric disease processes is required.