A method for clonal analysis of epidermal growth factor-responsive neural progenitors

Automated segmentation of brain cells for clonal analyses in fluorescence microscopy images

The understanding of how cell diversity within and across distinct brain regions is ontogenetically achieved is a pivotal topic in neuroscience. Clonal analyses based on multicolor cell labeling represent a powerful tool to tackle this issue and disclose lineage relationships, but produce enormous sets of fluorescence images, leading to time consuming analyses that may be biased by the operator's subjectivity. Thus, time-efficient automated software are needed to analyze images easily, accurately and without subjective bias. In this paper, we present a fully automated method, named FAST ('Fluorescent cell Analysis Segmentation Tool'), for the segmentation of neural cells labeled by multicolor combinations of fluorophores and for their classification into clones. The proposed method was tested on 77 high-magnification fluorescence images of adult mouse cerebellar tissues acquired using a confocal microscope. Automatic results were compared with manual annotations and two open-source software designed for cell detection in microscopic imaging. The algorithm showed very good performance in the cellular detection and in the assignment of the clonal identity. To the best of our knowledge, FAST is the first fully automated technique for the analysis of cellular clones based on combinatorial expression of fluorescent proteins. The proposed approach allows to perform clonal analyses easily, accurately and objectively, overcoming those biases and errors that may result from manual annotations. Moreover, it can be broadly applied to the quantification and colocalization within cells of fluorescent markers, therefore representing a versatile and powerful tool for automated quantitative analyses in fluorescence microscopy.

Differentiation of glioblastoma multiforme stem-like cells leads to downregulation of EGFR and EGFRvIII and decreased tumorigenic and stem-like cell potential

Glioblastoma multiforme (GBM) is the most common and devastating primary brain tumor among adults. Despite recent treatment progress, most patients succumb to their disease within 2 years of diagnosis. Current research has highlighted the importance of a subpopulation of cells, assigned brain cancer stem-like cells (bCSC), to play a pivotal role in GBM malignancy. bCSC are identified by their resemblance to normal neural stem cells (NSC), and it is speculated that the bCSC have to be targeted in order to improve treatment outcome for GBM patients. One hallmark of GBM is aberrant expression and activation of the epidermal growth factor receptor (EGFR) and expression of a deletion variant EGFRvIII. In the normal brain, EGFR is expressed in neurogenic areas where also NSC are located and it has been shown that EGFR is involved in regulation of NSC proliferation, migration, and differentiation. This led us to speculate if EGFR and EGFRvIII are involved in the regulation of bCSC. In this study we use GBM neurosphere cultures, known to preserve bCSC features. We demonstrate that EGFR and EGFRvIII are downregulated upon differentiation and moreover that when EGFR signaling is abrogated, differentiation is induced. Furthermore, we show that differentiation leads to decreased tumorigenic and stem cell-like potential of the neurosphere cultures and that by specifically inhibiting EGFR signaling it is possible to target the bCSC population. Our results suggest that differentiation therapy, possibly along with anti-EGFR treatment would be a feasible treatment option for patients with GBM, by targeting the bCSC population.

Level of Notch activation determines the effect on growth and stem cell-like features in glioblastoma multiforme neurosphere cultures

BACKGROUND

Brain cancer stem-like cells (bCSC) are cancer cells with neural stem cell (NSC)-like properties found in glioblastoma multiforme (GBM) and they are assigned a central role in tumor initiation, progression and relapse. The Notch pathway is important for maintenance and cell fate decisions in the normal NSC population. Notch signaling is often deregulated in GBM and recent results suggest that this pathway plays a significant role in bCSC as well. We therefore wished to further elucidate the role of Notch activation in GBM-derived bCSC.

METHODS

Human-derived GBM xenograft cells were cultured as NSC-like neurosphere cultures. Notch modulation was accomplished either by blocking the pathway using the γ-secretase inhibitor DAPT or by activating it by transfecting the cells with the constitutive active Notch-1 receptor.

RESULTS

GBM neurosphere cultures with high endogenous Notch activation displayed sensitivity toward Notch inhibition with regard to tumorigenic features as demonstrated by increased G0/G1 population and reduced colony formation capacity. Of the NSC-like characteristics, only the primary sphere forming potential was affected, while no effect was observed on self-renewal or differentiation. In contrast, when Notch signaling was activated a decrease in the G0/G1 population and an enhanced capability of colony formation was observed, along with increased self-renewal and de-differentiation.

CONCLUSION

Based on the presented results we propose that active Notch signaling plays a role for cell growth and stem cell-like features in GBM neurosphere cultures and that Notch-targeted anti-bCSC treatment could be feasible for GBM patients with high endogenous Notch pathway activation.

Taurine stimulates proliferation and promotes neurogenesis of mouse adult cultured neural stem/progenitor cells

This study reports an effect of taurine (1-10 mM) increasing markedly (120%) the number of neural precursor cells (NPCs) from adult mouse subventricular zone, cultured as neurospheres. This effect is one of the highest reported for adult neural precursor cells. Taurine-containing cultures showed 73-120% more cells than controls, after 24 and 96 h in culture, respectively. Taurine effect is due to enhanced proliferation as assessed by BrdU incorporation assays. In taurine cultures BrdU incorporation was markedly higher than controls from 1.5 to 48 h, with the maximal difference found at 1.5 h. This effect of taurine reproduced at every passage with the same window time. Taurine effects are not mimicked by glycine, alanine or GABA. Clonal efficiency values of 3.6% for taurine cultures and 1.3% for control cultures suggest a taurine influence on both, progenitor and stem cells. Upon differentiation, the proportion of neurons in control and taurine cultures was 3.1% (±0.5) and 10.2% (±0.8), respectively. These results are relevant for taurine implication in brain development as well as in adult neurogenesis. Possible mechanisms underlying taurine effects on cell proliferation are discussed.

Transplanted neural stem/precursor cells instruct phagocytes and reduce secondary tissue damage in the injured spinal cord

Transplanted neural stem/precursor cells possess peculiar therapeutic plasticity and can simultaneously instruct several therapeutic mechanisms in addition to cell replacement. Here, we interrogated the therapeutic plasticity of neural stem/precursor cells after their focal implantation in the severely contused spinal cord. We injected syngeneic neural stem/precursor cells at the proximal and distal ends of the contused mouse spinal cord and analysed locomotor functions and relevant secondary pathological events in the mice, cell fate of transplanted neural stem/precursor cells, and gene expression and inflammatory cell infiltration at the injured site. We used two different doses of neural stem/precursor cells and two treatment schedules, either subacute (7 days) or early chronic (21 days) neural stem/precursor cell transplantation after the induction of experimental thoracic severe spinal cord injury. Only the subacute transplant of neural stem/precursor cells enhanced the recovery of locomotor functions of mice with spinal cord injury. Transplanted neural stem/precursor cells survived undifferentiated at the level of the peri-lesion environment and established contacts with endogenous phagocytes via cellular-junctional coupling. This was associated with significant modulation of the expression levels of important inflammatory cell transcripts in vivo. Transplanted neural stem/precursor cells skewed the inflammatory cell infiltrate at the injured site by reducing the proportion of 'classically-activated' (M1-like) macrophages, while promoting the healing of the injured cord. We here identify a precise window of opportunity for the treatment of complex spinal cord injuries with therapeutically plastic somatic stem cells, and suggest that neural stem/precursor cells have the ability to re-programme the local inflammatory cell microenvironment from a 'hostile' to an 'instructive' role, thus facilitating the healing or regeneration past the lesion.

Notch signaling and brain tumors

Human brain tumors are a heterogenous group of neoplasms occurring inside the cranium and the central spinal cord. In adults and children, astrocytic glioma and medulloblastoma are the most common subtypes of primary brain tumors. These tumor types are thought to arise from cells in which Notch signaling plays a fundamental role during development. Recent findings have shown that Notch signaling is dysregulated and contributes to the malignant potential of these tumors. Growing evidence point towards an important role for cancer stem cells in the initiation and maintenance of glioma and medulloblastoma. In this chapter we will cover the present findings of Notch signaling in human glioma and medulloblastoma and try to create an overall picture of its relevance in the pathogenesis of these tumors.

Effect of microwell chip structure on cell microsphere production of various animal cells

The formation of three-dimensional cell microspheres such as spheroids, embryoid bodies, and neurospheres has attracted attention as a useful culture technique. In this study, we investigated a technique for effective cell microsphere production by using specially prepared microchip. The basic chip design was a multimicrowell structure in triangular arrangement within a 100-mm(2) region in the center of a polymethylmethacrylate (PMMA) plate (24x24 mm(2)), the surface of which was modified with polyethylene glycol (PEG) to render it nonadhesive to cells. We also designed six similar chips with microwell diameters of 200, 300, 400, 600, 800, and 1000 microm to investigate the effect of the microwell diameter on the cell microsphere diameter. Rat hepatocytes, HepG2 cells, mouse embryonic stem (ES) cells, and mouse neural progenitor/stem (NPS) cells formed hepatocyte spheroids, HepG2 spheroids, embryoid bodies, and neurospheres, respectively, in the microwells within 5 days of culture. For all the cells, a single microsphere was formed in each microwell under all the chip conditions, and such microsphere configurations remained throughout the culture period. Furthermore, the microsphere diameters of each type of cell were strongly positively correlated with the microwell diameters of the chips, suggesting that microsphere diameter can be factitiously controlled by using different chip conditions. Thus, this chip technique is a promising cellular platform for tissue engineering or regenerative medicine research, pharmacological and toxicological studies, and fundamental studies in cell biology.

A novel three-dimensional culture system for isolation and clonal propagation of neural stem cells using a thermo-reversible gelation polymer

In the present study, we examined the possible utility of a three-dimensional culture system using a thermo-reversible gelation polymer to isolate and expand neural stem cells (NSCs). The polymer is a synthetic biologically inert polymer and gelates at temperatures higher than the gel-sol transition point ( approximately 20 degrees C). When fetal mouse brain cells were inoculated into the gel, spherical colonies were formed ( approximately 1% in primary culture and approximately 9% in passage cultures). The spheroid-forming cells were positive for expression of the NSC markers nestin and Musashi. Under conditions facilitating spontaneous neural differentiation, the spheroid-forming cells expressed genes characteristic to astrocytes, oligodendrocytes, and neurons. The cells could be successively propagated at least to 80 poly-D-lysines over a period of 20 weeks in the gel culture with a growth rate higher than that observed in suspension culture. The spheroids formed by fetal mouse brain cells in the gel were shown to be of clonal origin. These results indicate that the spheroid culture system is a convenient and powerful tool for isolation and clonal expansion of NSCs in vitro.

The functional role of Notch signaling in human gliomas

Gliomas are among the most devastating adult tumors for which there is currently no cure. The tumors are derived from brain glial tissue and comprise several diverse tumor forms and grades. Recent reports highlight the importance of cancer-initiating cells in the malignancy of gliomas. These cells have been referred to as brain cancer stem cells (bCSC), as they share similarities to normal neural stem cells in the brain. The Notch signaling pathway is involved in cell fate decisions throughout normal development and in stem cell proliferation and maintenance. The role of Notch in cancer is now firmly established, and recent data implicate a role for Notch signaling also in gliomas and bCSC. In this review, we explore the role of the Notch signaling pathway in gliomas with emphasis on its role in normal brain development and its interplay with pathways and processes that are characteristic of malignant gliomas.

Identification of small-molecule modulators of mouse SVZ progenitor cell proliferation and differentiation through high-throughput screening

Adult mouse subventricular zone (SVZ) neural stem/progenitor cells are multipotent self-renewing cells that retain the capacity to generate the major cell types of the central nervous system in vitro and in vivo. The relative ease of expanding SVZ cells in culture as neurospheres makes them an ideal model for carrying out large-scale screening to identify compounds that regulate neural progenitor cell proliferation and differentiation. The authors have developed an adenosine triphosphate-based cell proliferation assay using adult SVZ cells to identify small molecules that activate or inhibit progenitor cell proliferation. This assay was miniaturized to a 1536-well format for high-throughput screening (HTS) of >1 million small-molecule compounds, and 325 and 581 compounds were confirmed as potential inducers of SVZ cell proliferation and differentiation, respectively. A number of these compounds were identified as having a selective proliferative and differentiation effect on SVZ cells versus mouse Neuro2a neuroblastoma cells. These compounds can potentially be useful pharmacological tools to modulate resident stem cells and neurogenesis in the adult brain. This study represents a novel application of primary somatic stem cells in the HTS of a large-scale compound library.

Intra-operatively obtained human tissue: protocols and techniques for the study of neural stem cells

The discoveries of neural (NSCs) and brain tumor stem cells (BTSCs) in the adult human brain and in brain tumors, respectively, have led to a new era in neuroscience research. These cells represent novel approaches to studying normal phenomena such as memory and learning, as well as pathological conditions such as Parkinson's disease, stroke, and brain tumors. This new paradigm stresses the importance of understanding how these cells behave in vitro and in vivo. It also stresses the need to use human-derived tissue to study human disease because animal models may not necessarily accurately replicate the processes that occur in humans. An important, but often underused, source of human tissue and, consequently, both NSCs and BTSCs, is the operating room. This study describes in detail both current and newly developed laboratory techniques, which in our experience are used to process and study human NSCs and BTSCs from tissue obtained directly from the operating room.

ABC transporters, neural stem cells and neurogenesis – a different perspective

Stem cells intrigue. They have the ability to divide exponentially, recreate the stem cell compartment, as well as create differentiated cells to generate tissues. Therefore, they should be natural candidates to provide a renewable source of cells for transplantation applied in regenerative medicine. Stem cells have the capacity to generate specific tissues or even whole organs like the blood, heart, or bones. A subgroup of stem cells, the neural stem cells (NSCs), is characterized as a self-renewing population that generates neurons and glia of the developing brain. They can be isolated, genetically manipulated and differentiated in vitro and reintroduced into a developing, adult or a pathologically altered central nervous system. NSCs have been considered for use in cell replacement therapies in various neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease. Characterization of genes with tightly controlled expression patterns during differentiation represents an approach to understanding the regulation of stem cell commitment. The regulation of stem cell biology by the ATP-binding cassette (ABC) transporters has emerged as an important new field of investigation. As a major focus of stem cell research is in the manipulation of cells to enable differentiation into a targeted cell population; in this review, we discuss recent literatures on ABC transporters and stem cells, and propose an integrated view on the role of the ABC transporters, especially ABCA2, ABCA3, ABCB1 and ABCG2, in NSCs' proliferation, differentiation and regulation, along with comparisons to that in hematopoietic and other stem cells.

Methods for isolating highly-enriched embryonic spinal cord neurons: A comparison between enzymatic and mechanical dissociations

Spinal cord neuronal culture is a useful system to study normal and abnormal functions of the spinal cord. For many bioassays, obtaining large quantities of highly purified spinal cord neurons is required. However, technical difficulties exist in obtaining these cells reliably and consistently. By comparing two dissociation methods, mechanical and enzymatic dissociations, we found that the enzymatic dissociation of embryonic day 14-15 spinal cords resulted in significantly higher cell yield than the mechanical dissociation (25.40 +/- 5.41 x 10(6) versus 3.43 +/- 0.52 x 10(6) cells per 12 embryos; n = 6/group; p < 0.01). Furthermore, cell viability was significantly higher after the enzymatic than the mechanical dissociation (83.40 +/- 3.08% versus 32.81 +/- 3.49%, n = 4/group; p < 0.01). In both methods, highly purified populations of primary neurons were obtained (mechanical: 85.17 +/- 2.84%; enzymatic: 87.67 +/- 2.52%; n = 3/group). Critical measures that affect culture outcomes include, but not limited to, the age of embryo, cell seeding density, dissociation time, and elimination of non-neuronal cells. Thus, the present study has identified the enzymatic dissociation method to be a preferred method for obtaining large quantity of highly-enriched embryonic spinal cord neurons.

Clonal analysis of adult human olfactory neurosphere forming cells

Olfactory neuroepithelium (ONe) is unique because it contains progenitor cells capable of mitotic division that replace damaged or lost neurons throughout life. We isolated populations of ONe progenitors from adult cadavers and patients undergoing nasal sinus surgery that were heterogeneous and consisted of neuronal and glial progenitors. Progenitor lines have been obtained from these cultures that continue to divide and form nestin positive neurospheres. In the present study, we used clonal and population analyses to probe the self-renewal and multipotency of the neurosphere forming cells (NSFCs). NSFCs plated at the single cell level produced additional neurospheres; dissociation of these spheres resulted in mitotically active cells that continued to divide and produce spheres as long as they were subcultured. The mitotic activity of clonal NSFCs was assessed using bromodeoxyuridine (BrdU) incorporation. Lineage restriction of the clonal cultures was determined using a variety of antibodies that were characteristic of different levels of neuronal commitment: ss-tubulin isotype III, neural cell adhesion molecule (NCAM) and microtubule associated protein (MAP2), or glial restriction: astrocytes, glial fibrillary acidic protein (GFAP); and oligodendrocytes, galactocerebroside (GalC). Furthermore, nestin expression, a marker indicative of progenitor nature, decreased in defined medium compared to serum-containing medium. Therefore, adult human ONe-derived neural progenitors retain their capacity for self-renewal, can be clonally expanded, and offer multipotent lineage restriction. Therefore, they are a unique source of progenitors for future cell replacement strategies in the treatment of neurotrauma and neurodegenerative diseases.

Sphere formation of ocular epithelial cells in the ciliary body is a reprogramming system for neural differentiation

It is well known that neural stem/progenitor cells of the central nervous system (CNS) can proliferate to form neurospheres (CNS-neurospheres) that are positive for nestin, an intermediate filament for neural progenitors. Retinal stem/progenitor properties were also isolated from the ciliary body (CB) of the eye where, as in the CNS, such stem/progenitors also form spheres and have been considered to expand only via expansion by their proliferation even from the single-cell level (called spheres of pigment cells from the ciliary margin: PCM-spheres). We here found a new and distinct process underlying the growth of CB cell-derived spheres (CB-spheres) that is unlike the mechanism of CNS- and PCM-sphere expansion; this new process is a cell proliferation-independent incorporation of neighbor spheres and cells cultured at high density (200 cells/mul). The majority of cells in CB-spheres consisted of nestin-negative epithelia-like cells and started to express nestin during the course of their expansion by high-density cultivation. The growth of CNS-neurospheres was sensitive to a cell-cycle inhibitor, whereas the growth of CB-spheres was not seriously affected by cell proliferation; rather, the spheres grew by incorporating other CB-spheres and nestin-negative adherent cells, the latter of which started to express nestin and lost the expression of epithelial markers after being incorporated. These results indicate that CB-spheres do not form by the accumulation of neural progenitors but rather by a reprogramming system from epithelia-like cells for neural differentiation, a clearly distinct mechanism from sphere formation by single-cell expansion of retinal stem/progenitor populations.

Neurofibromin regulates neural stem cell proliferation, survival, and astroglial differentiation in vitro and in vivo

Neurofibromatosis 1 (NF1) is a common inherited disease in which affected children exhibit abnormalities in astrocyte growth regulation and are prone to the development of brain tumors (astrocytoma). Previous studies from our laboratory demonstrated that Nf1 mutant mouse astrocytomas contains populations of proliferating nestin+ progenitor cells, suggesting that immature astroglial progenitors may serve as a reservoir of proliferating tumor cells. Here, we directly examined the consequences of Nf1 inactivation on neural stem cell (NSC) proliferation in vitro and in vivo. We found dose-dependent effects of neurofibromin expression on NSC proliferation and survival in vitro, which reflected increased RAS pathway activation and increased bcl2 expression. In addition, unlike wild-type NSCs, Nf1-/- NSCs and, to a lesser extent, Nf1+/- NSCs survive as xenografts in naive recipient brains in vivo. Although Nf1-/- NSCs are multipotent, Nf1-/- and Nf1+/-, but not wild-type, NSCs generated increased numbers of morphologically abnormal, immature astroglial cells in vitro. Moreover, the Nf1-/- NSC growth and survival advantage as well as the astroglial cell differentiation defect were completely rescued by expression of the GAP (RAS-GTPase activating protein) domain of neurofibromin. Finally, the increase in astroglial progenitors and proliferating cells seen in vitro was also observed in Nf1-/- and Nf1+/- embryonic as well as Nf1+/- adult brains in vivo. Collectively, these findings support the hypothesis that alterations in neurofibromin expression in the developing brain have significant consequences for astrocyte growth and differentiation relevant to normal brain development and astrocytoma formation in children.

F-spondin promotes nerve precursor differentiation

Cells in the developing nervous system secrete a large number of proteins that regulate the migration and differentiation of their neighbors. It is shown here that a clonal central nervous system cell line secretes a protein that causes both a rat hippocampal progenitor cell line and primary cortical neural cells to differentiate into cells with the morphological and biochemical features of neurons. This protein was identified as F-spondin. Analysis of F-spondin isoforms secreted from transfected cells shows that the core protein without the thrombospondin type 1 repeats is sufficient to promote neuronal differentiation when adsorbed to a surface. F-spondin can also inhibit neurite outgrowth while allowing the expression of nerve-specific proteins when present in a soluble form at high concentrations. Therefore, F-spondin can alter cell differentiation in multiple ways, depending upon its concentration and distribution between substrate-attached and soluble forms.

Effect of neurosphere size on the growth rate of human neural stem/progenitor cells

Neural stem/progenitor cells (NSPCs) proliferate as aggregates in vitro, but the mechanism of aggregation is not fully understood. Here, we report that aggregation promotes the proliferation of NSPCs. We found that the proliferation rate was linear and depended on the size of the aggregate; that is, the population doubling time of the NSPCs gradually decreased as the diameter approached 250 micro m and flattened to a nearly constant value beyond this diameter. Given this finding, and with the intent of enhancing the efficiency of human NSPC expansion, we induced the NSPCs to form aggregates close to 250 micro m in diameter quickly by culturing them in plates with U-bottomed wells. The NSPCs formed aggregates effectively in the U-bottomed wells, with cell numbers approximately 1.5 times greater than those in the aggregates that formed spontaneously in flat-bottomed wells. In addition, this effect of aggregation involved cell-cell signaling molecules of the Notch1 pathway. In the U-bottomed wells, Hes1 and Hes5, which are target genes of the Notch signal, were expressed at higher levels than in the control, flat-bottomed wells. The amount of cleaved Notch1 was also higher in the cells cultured in the U-bottomed wells. The addition of gamma-secretase inhibitor, which blocks Notch signaling, suppressed cell proliferation in the U-bottomed wells. These results suggest that the three-dimensional architecture of NSPC aggregates would create a microenvironment that promotes the proliferation of human NSPCs.

In vivo haematopoietic potential of human neural stem cells

The fetal sheep model was used to compare the in vivo haematopoietic potential of human neural stem cells (NSC) versus bone marrow (BM)-derived haematopoietic stem cells (HSC). To this end, sheep were transplanted with either 8 x 10(5) NSC (n = 11) or HSC, CD34(+)Lin(-) (n = 5), and subsequently analysed for haematopoietic chimaerism. While HSC-transplanted sheep displayed robust donor-derived haematopoiesis starting at less than 2 months post-transplant, NSC recipients exhibited haematopoietic engraftment at much later time points. Nevertheless, chimaerism persisted in both groups throughout the course of this study. Transplantation of secondary recipients with human CD45(+)/HLA-DR(+) cells from the BM of NSC primary recipients at 14 and 16 months post-transplant demonstrated that long-term engrafting HSC were present in these animals. At 6 months post-transplant, both NSC- and HSC-transplanted sheep were mobilised with granulocyte colony-stimulating factor. In contrast to HSC-transplanted animals, levels of human blood cells in peripheral blood of NSC-transplanted sheep remained low throughout mobilisation. Our results show that, although human NSC were able to give rise to multilineage haematopoiesis in our model, the levels, timing of blood cell production and the ability to respond to cytokine mobilisation were different, suggesting that human NSCs latent haematopoietic potential is inherently different from that of true HSC.

Regeneration of human auditory nerve. In vitro/in video demonstration of neural progenitor cells in adult human and guinea pig spiral ganglion

Time lapse video recordings of cultured adult human and guinea pig spiral ganglion (hSG and gpSG) show that mitogen responsive progenitor/stem cells develop in the form of spheres that proliferate and differentiate into mature neurons and glia cells. Neurospheres, cultured with EGF and bFGF showed expression of nestin and incorporation of 5'-Bromo-2-deoxyuridine (BrdU). Newly formed BrdU labelled cells were positive for beta-tubulin, and also for GFAP demonstrating that neuronal cells were derived from a dividing population of progenitor cells. Dissociated spheres cultured either with glia cell line-derived neurotrophic factor (GDNF) or brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), induced differentiation of the progenitor cells. Video microscopy showed that neurons develop from subcultured spheres maintained for up to four weeks. Neurons showed fasciculation and migration with a speed of 10-30 microm/h, and some cells had up to 6 mm long neurites coexpressing TrkB and TrkC receptors. Precise dissection suggests that the neurons formed are cochlea-specific. The results suggest that the mammalian auditory nerve has the capability for self-renewal and replacement. Transplantation of progenitor cells together with established means to induce neural differentiation and fiber growth may facilitate strategies for better repair and treatment of auditory neuronal damage.

Prospective characterization of neural stem cells by flow cytometry analysis using a combination of surface markers

Neural stem cells (NSCs) with self-renewal and multilineage differentiation properties can potentially repair degenerating or damaged neural tissue. Here, we have enriched NSCs from neurospheres, which make up a heterogeneous population, by fluorescence-activated cell sorting (FACS) with antibodies against syndecan-1, Notch-1, and integrin-beta1, which were chosen as candidates for hematopoietic cell-or somatic stem cell-markers. Antigen-positive cells readily initiated neurosphere formation, but cells lacking these markers did so less readily. Doubly positive cells expressing both syndecan-1 and Notch-1 underwent neurosphere formation more efficiently than did singly positive cells. The progeny of sorted cells could differentiate into neurons and glial cells both in vitro and in vivo. These antibodies were also useful for isolating cells from the murine embryonic day 14.5 brain that efficiently formed neurospheres. In contrast, there was no distinct difference in neurosphere formation efficiency between Hoechst 33342-stained side population cells and main population cells, although the former are known to have a stem cell phenotype in various tissues. These results indicate the usefulness of syndecan-1, Notch-1, and integrin-beta1 as NSC markers.

Neurospheres: Insights into neural stem cell biology

Neural stem cells (NSC) are a tissue-specific subtype of self-renewing and multipotent cells that can give rise to all neural populations. In this review, the importance of maintaining cell-cell contacts in the study of NSC is highlighted, and data obtained from some crucial single-cell studies is compared to results obtained from neurospheres, where aggregates of NSC are grown in suspension. In particular, results that indicate how this culture system may be well suited to analyze NSC plasticity, cell-cell, and cell-extracellular matrix (ECM) interactions are pointed out, and the hypothesis that cell-cell and cell-ECM contacts may be essential for NSC maintenance, survival, and proliferation is highlighted. Finally, it is suggested that neurospheres might play a role in the study of context-dependent behavior of NSC in niches by providing a system where NSC can be challenged chemically or biologically and analyzed in vitro, in a time- and context-dependent manner.

Clonogenicity of human endometrial epithelial and stromal cells

The human endometrium regenerates from the lower basalis layer, a germinal compartment that persists after menstruation to give rise to the new upper functionalis layer. Because adult stem cells are present in tissues that undergo regeneration, we hypothesized that human endometrium contains small populations of epithelial and stromal stem cells responsible for cyclical regeneration of endometrial glands and stroma and that these cells would exhibit clonogenicity, a stem-cell property. The aims of this study were to determine 1) the clonogenic activity of human endometrial epithelial and stromal cells, 2) which growth factors support this clonogenic activity, and 3) determine the cellular phenotypes of the clones. Endometrial tissue was obtained from women undergoing hysterectomy. Purified single- cell suspensions of epithelial and stromal cells were cultured at cloning density (300-500/cm(2)) in serum medium or in serum- free medium supplemented with one of eight growth factors. Small numbers of epithelial (0.22%) and stromal cells (1.25%) initiated colonies in serum-containing medium. The majority of colonies were small, containing large, loosely arranged cells, and 37% of epithelial and 1 in 60 of stromal colonies were classified as large, comprising small, densely packed cells. In serum-free medium, transforming growth factor-alpha (TGF alpha), epidermal growth factor (EGF), platelet-derived growth factor-BB (PDGF-BB) strongly supported clonogenicity of epithelial cells, while leukemia-inhibitory factor (LIF), hepatocyte growth factor (HGF), stem-cell factor (SCF), insulin-like growth factor-I (IGF- I) were weakly supportive, and basic fibroblast growth factor (bFGF) was without effect. TGF alpha, EGF, PDGF-BB, and bFGF supported stromal cell clonogenicity, while HGF, SCF, LIF, and IGF- I were without effect. Small epithelial colonies expressed three epithelial markers but not stromal markers; however, large epithelial colonies showed little reactivity for all markers except alpha(6)-integrin. All stromal colonies contained fibroblasts, expressing stromal markers, and in some colonies, myofibroblasts were also identified. This analysis of human endometrium has demonstrated the presence of rare clonogenic epithelial and stromal cells with high proliferative potential, providing the first evidence for the existence of putative endometrial epithelial and stromal stem cells.