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

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

Ultrastructure of human neural stem/progenitor cells and neurospheres

BACKGROUND： Biological and morphological characteristics of neural stem/progenitor cells （NSPCs） have been widely investigated. OBJECTIVE： To explore the ultrastructure of human embryo-derived NSPCs and neurospheres cultivated in vitro using electron microscopy. DESIGN, TIME AND SETTING： A cell biology experiment was performed at the Brain Tumor Laboratory of Soochow University, and Jiangsu Province Key Laboratory of Neuroregeneration, Nantong University between August 2007 and April 2008. MATERIALS： Human fetal brain tissue was obtained from an 8-week-old aborted fetus; serum-free Dulbecco＇s modified Eagle＇s medium/F12 culture medium was provided by Gibco, USA; scanning electron microscope was provided by Hitachi Instruments, Japan; transmission electron microscope was provided by JEOL, Japan. METHODS： NSPCs were isolated from human fetal brain tissue and cultivated in serum-free Dulbecco＇s modified Eagle＇s medium/F12 culture medium. Cells were passaged every 5-7 days. After three passages, NSPCs were harvested and used for ultrastructural examination. MAIN OUTCOME MEASURES： Ultrastructural examination of human NSPCs and adjacent cells in neurospheres. RESULTS： Individual NSPCs were visible as spherical morphologies with rough surfaces under scanning electron microscope. Generally, they had large nuclei and little cytoplasm. Nuclei were frequently globular with large amounts of euchromatin and a small quantity of heterochromatin, and most NSPCs had only one nucleolus. The Golgi apparatus and endoplasmic reticulum were underdeveloped; however, autophagosomes were clearly visible. The neurospheres were made up of NSPCs and non-fixiform material inside. Between adjacent cells and at the cytoplasmic surface of apposed plasma membranes, there were vesicle-like structures. Some membrane boundaries with high permeabilities were observed between some contiguous NSPCs in neurospheres, possibly attributable to plasmalemmal fusion between adjacent cells. CONCLUSION： A large number of autophagosomes were observed in NSPCs and gap junctions were visible between adjacent NSPCs.

Identification of Ca2+ signaling components in neural stem/progenitor cells during differentiation into neurons and glia in intact and dissociated zebrafish neurospheres

The development of the CNS in vertebrate embryos involves the generation of different sub-types of neurons and glia in a complex but highly-ordered spatio-temporal manner. Zebrafish are commonly used for exploring the development, plasticity and regeneration of the CNS, and the recent development of reliable protocols for isolating and culturing neural stem/progenitor cells(NSCs/NPCs) from the brain of adult fish now enables the exploration of mechanisms underlying the induction/specification/differentiation of these cells. Here, we refined a protocol to generate proliferating and differentiating neurospheres from the entire brain of adult zebrafish. We demonstrated via RT-qPCR that some isoforms of ip3 r, ryr and stim are upregulated/downregulated significantly in differentiating neurospheres, and via immunolabelling that 1,4,5-inositol trisphosphate receptor(IP3 R) type-1 and ryanodine receptor(RyR) type-2 are differentially expressed in cells with neuron-or radial glial-like properties. Furthermore, ATP but not caffeine(IP3 R and RyR agonists, respectively), induced the generation of Ca^(2+) transients in cells exhibiting neuron-or glial-like morphology. These results indicate the differential expression of components of the Ca^(2+) -signaling toolkit in proliferating and differentiating cells. Thus, given the complexity of the intact vertebrate brain, neurospheres might be a useful system for exploring neurodegenerative disease diagnosis protocols and drug development using Ca^(2+) signaling as a read-out.

Aldynoglia cells and modulation of RhoGTPase activity as useful tools for spinal cord injury repair

A combined approach in spinal cord injury （SCI） therapy is the modulation of the cellular and molecular processes involved in glial scarring. Aldaynoglial cells are neural cell precursors with a high capacity to differentiate into neurons, promote axonal growth, wrapping and myelination of resident neurons. These important characteristics of aldaynoglia can be combined with specific inhibition of the RhoGTPase activity in astroglia and microglia that cause reduction of glial proliferation, retraction of glial cell processes and myelin production by oligodendrocytes. Previously we used experimental central nervous system （CNS） injury models, like spinal cord contusion and striatal lacunar infarction and observed that administration of RhoGTPase glycolipid inhibitor or aldaynoglial cells, respectively, produced a significant gain of functional recovery in treated animals. The combined therapy with neuro-regenerative properties strategy is highly desirable to treat SCI for functional potentiation of neurons and oligodendrocytes, resulting in better locomotor recovery. Here we suggest that treatment of spinal lesions with aldaynoglia from new rospheres plus local administration of a RhoGTPase inhibitor could have an additive effect and promote recovery from SCI.

Cell proliferation and apoptosis in optic nerve and brain integration centers of adult trout Oncorhynchus mykiss after optic nerve injury

Fishes have remarkable ability to effectively rebuild the structure of nerve cells and nerve fibers after central nervous system injury.However,the underlying mechanism is poorly understood.In order to address this issue,we investigated the proliferation and apoptosis of cells in contralateral and ipsilateral optic nerves,after stab wound injury to the eye of an adult trout Oncorhynchus mykiss.Heterogenous population of proliferating cells was investigated at 1 week after injury.TUNEL labeling gave a qualitative and quantitative assessment of apoptosis in the cells of optic nerve of trout 2 days after injury.After optic nerve injury,apoptotic response was investigated,and mass patterns of cell migration were found.The maximal concentration of apoptotic bodies was detected in the areas of mass clumps of cells.It is probably indicative of massive cell death in the area of high phagocytic activity of macrophages/microglia.At 1 week after optic nerve injury,we observed nerve cell proliferation in the trout brain integration centers：the cerebellum and the optic tectum.In the optic tectum,proliferating cell nuclear antigen（PCNA）-immunopositive radial glia-like cells were identified.Proliferative activity of nerve cells was detected in the dorsal proliferative（matrix） area of the cerebellum and in parenchymal cells of the molecular and granular layers whereas local clusters of undifferentiated cells which formed neurogenic niches were observed in both the optic tectum and cerebellum after optic nerve injury.In vitro analysis of brain cells of trout showed that suspension cells compared with monolayer cells retain higher proliferative activity,as evidenced by PCNA immunolabeling.Phase contrast observation showed mitosis in individual cells and the formation of neurospheres which gradually increased during 1–4 days of culture.The present findings suggest that trout can be used as a novel model for studying neuronal regeneration.

Growth and differentiation of neural stem cells in a three-dimensional collagen gel scaffold

Collagen protein is an ideal scaffold material for the transplantation of neural stem cells. In this study rat neural stern cells were seeded into a three-dimensional collagen gel scaffold, with suspension cultured neural stem cells being used as a control group. Neural stem cells, which were cultured in medium containing epidermal growth factor and basic fibroblast growth factor, actively expanded and formed neurospheres in both culture groups. In serum-free medium conditions, the processes extended from neurospheres in the collagen gel group were much longer than those in the suspension culture group. Immunofluorescence staining showed that neurespheres cultured in collagen gels were stained positive for nestin and differentiated cells were stained positive for the neuronal marker βIII-tubulin, the astrocytic marker glial fibrillary acidic protein and the oligodendrocytic marker 2＇,3＇-cyclic nucleotide 3＇-phosphodiesterase. Compared with neurospheres cultured in suspension, the differentiation potential of neural stem cells cultured in collagen gels increased, with the formation of neurons at an early stage. Our results show that the three-dimensional collagen gel culture system is superior to suspension culture in the proliferation, differentiation and process outgrowth of neural stem cells.

Sphere-forming corneal cells repopulate dystrophic keratoconic stroma:Implications for potential therapy

BACKGROUND Keratoconus is a degenerative corneal disease characterised by aberrant cell behaviour and loss of matrix that can result in vision loss.Cells extracted from peripheral corneas can form stem cell-enriched spheres,which have shown the potential to repopulate the normal peripheral corneal stroma in vitro upon sphere implantation but have not been previously studied in keratoconic tissue.AIM To investigate the therapeutic potential of stem cell-enriched spheres formed from extracted peripheral human corneal cells when introduced to keratoconic tissue.METHODS Stem cell-enriched spheres were formed from extracts of normal cadaveric human peripheral corneal cells.These spheres were implanted into incisions created in full thickness and onto the surface of 10μm thin sections of keratoconic and normal stromal tissues in vitro.Tissue sections were used to maximise use of limited keratoconic tissue available for research.Living cells were stained with Calcein-AM and visualised with stereo and fluorescence microscopy to assess survival and behaviours between the time of implantation day 0 and 14 d(D14)from implantation.Sphere cells in implanted tissues were characterised for stem cell and differentiation markers using immunohistochemistry and droplet digital PCR to assess the potential implications of these characteristics in the use of spheres in keratoconus treatment.RESULTS Spheres were successfully implanted into full-thickness central corneal tissue and onto the surface of 10μm thin en face tissue sections.No observable differences were seen in sphere migration,proliferation or differentiation in keratoconic tissue compared to normal between day 0 and D14.Spheres stained positively with Calcein-AM up to D14.Cell migration increased from day 0 to D14,occurring radially in three dimensions from the sphere and in alignment with tissue edges.Cell proliferation marker,EdU,was detected at day 10.Implanted spheres stained positively for putative stem cell markersΔNp63αand ABCB5,while ABCG2,ABCB5,ΔNp63 and p63αwere detectable by droplet digital PCR up to D14.Double immunolabelling revealed absence of ABCB5 staining in migrated cells but positive staining of alpha smooth muscle actin(myofibroblast marker)in some migrated cells.Droplet digital PCR showed similar expression patterns of differentiation markers but a reduction in stem cell markers between normal and keratoconic tissue with an increase in stromal cell markers and a reduction in epithelial cell markers,indicating an appropriate response to repopulating diseased tissue.CONCLUSION Cells from implanted stem cell-enriched spheres can repopulate a keratoconic corneal stromal surface in a directed manner and exhibit migratory stromal cell phenotypes.

Valproic acid enhances neurosphere formation in cultured rat embryonic cortical cells through TGFβ1 signaling

This study aimed to investigate the effect and mechanism of valproic acid(VPA)on the neurosphere formation in rat embryonic cortical cells.We used free-floating neurosphere formation as a model system to evaluate the VPA on the proliferation of neural stem cells(NSCs).We found a time-and dose-dependent increase in neurosphere formation and NSC proliferation after VPA treatment.Further RNA-seq analysis demonstrated that the upregulated TGFβ1 signaling might attribute to the effect of VPA on the neurosphere formation and NSC proliferation.Consistently,the neurosphere formation and NSC proliferation were blocked by the treatment with SB431542,an inhibitor of TGFβ1 receptor.Moreover,in a coculture system,NSCs treated with VPA significantly reduced the oxygen-glucose deprivation-induced neuronal apoptosis.Taken together,our results showed that VPA could enhance neurosphere formation and NSC proliferation by activating TGFβ1,which might be a novel therapeutic strategy for neurological disorders.

Nerve growth factor promotes in vitro proliferation of neural stem cells from tree shrews

Neural stem cells promote neuronal regeneration and repair of brain tissue after injury,but have limited resources and proliferative ability in vivo.We hypothesized that nerve growth factor would promote in vitro proliferation of neural stem cells derived from the tree shrews,a primate-like mammal that has been proposed as an alternative to primates in biomedical translational research.We cultured neural stem cells from the hippocampus of tree shrews at embryonic day 38,and added nerve growth factor（100 μg/L） to the culture medium.Neural stem cells from the hippocampus of tree shrews cultured without nerve growth factor were used as controls.After 3 days,fluorescence microscopy after DAPI and nestin staining revealed that the number of neurospheres and DAPI/nestin-positive cells was markedly greater in the nerve growth factor-treated cells than in control cells.These findings demonstrate that nerve growth factor promotes the proliferation of neural stem cells derived from tree shrews.

Role of nestin in glioma invasion

AIM: To determine the role for the intermediate filament protein nestin in glioma invasion. METHODS: We examined the expression and function of nestin in gliomas(Grades Ⅱ-Ⅳ as defined by the World Health Organization). We determined nestin expression using Immunohistochemical methods. To elucidate nestin's biological function(s), we reduced m RNA levels by 61% and 87% in two glioblastomaderived neurosphere lines using short hairpin RNAs and determined the effect of reduced nestin expression on glioma cell proliferation and invasion using MTS and matrigel migration assays, respectively. We also utilized quantitative real time polymerase chain reaction assaysto determine the effect of reduced nestin expression on the expression of other markers associated with glioma stem cells and their differentiated progenies. RESULTS: We found a significant correlation between nestin immunoreactivity and astrocytoma tumor grade, with 36% of grade Ⅱ, 75% of grade Ⅲ, and 100% of grade Ⅳtumors expressing significant levels of the protein when assessed using immunohistochemistry. Reduction in nestin expression had no effect on cell growth in culture, but did retard the capacity of one line to migrate in-vitro on matrigel. Interestingly, in the line whose migration was not affected, m RNA levels of a second intermediate filament, synemin(also knowns as desmuslin), were elevated following introduction of sh RNA targeting nestin. As synemin was not induced in the line which required nestin for migration, it is a possibility that synemin may compensate for the loss of nestin in this process. CONCLUSION: Nestin expression is prominent in high-grade astrocytomas. Nestin is not required for cell growth but it may, however, be required for cell motility.

Elimination of the geomagnetic field stimulates the proliferation of mouse neural progenitor and stem cells

Living organisms are exposed to the geomagnetic field （GMF） throughout their lifespan. Elimination of the GMF, resulting in a hypogeomagnetic field （HMF）, leads to central nervous system dysfunction and abnormal development in animals. However, the cellular mecha-nisms underlying these effects have not been identified so far. Here, we show that exposure to an HMF （〈200 nT）, produced by a magnetic field shielding chamber, pro- motes the proliferation of neural progenitor/stem cells （NPCslNSCs） from C57BL/6 mice. Following seven-day HMF-exposure, the primary neurospheres （NSs） were significantly larger in size, and twice more NPCslNSCs were harvested from neonatal NSs, when compared to the GMF controls. The self-renewal capacity and multi- potency of the NSs were maintalned, as HMF-exposed NSs were posltlve for NSC markers （Nestin and Sox2）, and could differentiate into neurons and astrocytelglial cells and be passaged continuously. In addition, adult mice exposed to the HMF for one month were observed to have a greater number of proliferative cells In the subventrlcular zone. These flndlngs indicate that continuous HMF-exposure increases the proliferation of NPCslNSCs, In vitro and in vlvo. HMF-dlsturbed NPCs/NSCs production probably affects brain development and function, which provides a novel clue for elucidating the cellular mechanisms of the bio.HMF response.

Comparative study on the stem cell phenotypes of C6 cells under different culture conditions

Background Glioma stem cell （GSC） hypothesis posits that a subpopulation of cells within gliomas have true clonogenic and tumorigenic potential. Significantly, a more controversial correlate to GSC is that cells in different culture conditions might display distinct stem cell properties. Considering these possibilities, we applied an approach comparing stem cell characteristics of C6 glioma cells under different culture conditions.Methods C6 cells were cultured under three different growth conditions, i.e., adherent growth in conventional 10% serum medium, non-adherent spheres growth in serum-free medium, as well as adherent growth on laminin-coated flask in serum-free medium. Growth characteristics were detected contrastively through neurosphere formation assay and cell cycle analysis. Markers were determined by immunofluorescence, relative-quantitative reverse transcription （RT）-PCR,Western blotting and flow cytometry. Side population cells were analyzed via flow cytometry. Tumor models were detected by magnetic resonance imaging and hematoxylin ＆ eosin staining. Data analyses were performed with SPSS software （17.0）.Results C6 cells （C6-Adh, C6-SC-Sph and C6-SC-Adh） showed distinctive growth patterns and proliferation capacity.Compared to suspending C6-SC-Sph, adherent C6-Adh and C6-SC-Adh displayed higher growth ratio. C6-SC-Sph and C6-SC-Adh showed enhanced capability of neurosphere formation and self-renewal. High side population ratio was detected in C6-SC-Sph and C6-SC-Adh. CD133 was not detected in all three kinds of cells. Conversely, Nestin and β-Ⅲ-tubulin were demonstrated positive, nonetheless with no statistical significance （P 〉0.05）. Interestingly, lower expression of glial fibrillary acidic protein was demonstrated in C6-SC-Sph and C6-SC-Adh. C6-Adh, C6-SC-Sph and C6-SC-Adh were all displayed in situ oncogenicity, while statistical difference of survival time was not confirmed.Conclusions C6 glioma cell line is endowed with some GSC phenotypes that can be moderately enriched in vitro when transferred into stem cell culture condition. The resultant tumor-spheres may be not a prerequisite or sound source of GSCs and adherent culture in stem cell medium is not a growth condition in favor of GSCs expanding in vivo.