Stem Cells In Subventricular Zone Research Articles

Experimental study on growth, proliferation and differentiation of neural stem cell from subventricular zone of human fetal brain at different gestational age

To study growth characteristics of neural stem cells (NSCs) from subventricular zone (SVZ) of the different human fetal brain at different gestational age and to provide experimental and theoretical evidences for clinical application of NSCs for treatment of certain diseases. Ninety human embryos at gestational age 16 - 36 weeks were collected and were divided into six groups according to gestational age: 16 w, 20 w, 24 w, 28 w, 32 w and 36 w. Each group had 15 embryos and brain tissues were taken from each embryo's SVZ. All subjects had congenital heart disease or digestive tract abnormity diagnosed with B ultrasound at antepartum, but none had abnormal development of brain. Pregnant mother and her husband desire termination of pregnancy. The morphology, existing mode and the number of neural stem cells in subventricular zone were examined with immunohistochemical method. The NSCs in subventricular zone were cultured, passaged and differentiated with cell culture technique, then were identified with immunohistochemical method. NSCs in SVZ from the different human fetal brain existed in a scattered manner in the network formed by stellate cells, NSCs had round, ellipse and fusiform shape, especially in stellate shape. NSCs had larger and smaller size and distributed in dense or scattered forms, each having zero to two enations, most had one or two. NSCs had less cytoplasm. The nucli of the NSCs had a round shape with loose chromatin and 1 - 4 nucleoli. Most of NSCs existed in singular scattered form, some of them showed symmetrical or asymmetrical division, some of them showed synaptic connection with other NSCs. The number of NSCs in SVZ from groups with different fetal age decreased with increasing gestational age (chi(2) = 4644.602, P < 0.01). NSCs in SVZ from the different human fetal brain cultured with serum-free medium formed typical neurospheres in suspension. The cells could be passaged continuously, and could express nestin antigen. Serum-contained medium induced neural stem cells to differentiate and express specific antigens of neuron, astrocyte and oligodendrocyte. NSCs existed in SVZ of human embryos at different gestational age. There are differences in morphology, existing pattern and the number of NSCs in SVZ at different gestational age. NSCs in SVZ at different gestational age may be cultured in vitro.

PDGFRα-Positive B Cells Are Neural Stem Cells in the Adult SVZ that Form Glioma-like Growths in Response to Increased PDGF Signaling

Neurons and oligodendrocytes are produced in the adult brain subventricular zone (SVZ) from neural stem cells (B cells), which express GFAP and have morphological properties of astrocytes. We report here on the identification B cells expressing the PDGFRalpha in the adult SVZ. Specifically labeled PDGFRalpha expressing B cells in vivo generate neurons and oligodendrocytes. Conditional ablation of PDGFRalpha in a subpopulation of postnatal stem cells showed that this receptor is required for oligodendrogenesis, but not neurogenesis. Infusion of PDGF alone was sufficient to arrest neuroblast production and induce SVZ B cell proliferation contributing to the generation of large hyperplasias with some features of gliomas. The work demonstrates that PDGFRalpha signaling occurs early in the adult stem cell lineage and may help regulate the balance between oligodendrocyte and neuron production. Excessive PDGF activation in the SVZ in stem cells is sufficient to induce hallmarks associated with early stages of tumor formation.

Lentiviral Vectors Mediate Efficient and Stable Gene Transfer in Adult Neural Stem CellsIn Vivo

Modulation of adult neurogenesis may offer new therapeutic strategies for various brain disorders. In the adult mammalian brain the subventricular zone (SVZ) of the lateral ventricle is a region of continuous neurogenesis. Lentiviral vectors stably integrate into dividing and nondividing cells, in contrast to retroviral vectors, which integrate only into dividing cells. We compared their potential for gene transfer into both quiescent and slowly dividing stem cells as well as into more rapidly dividing progenitor cells. In contrast to retroviral vectors, stereotactic injection of lentiviral vectors into the SVZ of adult mice resulted in efficient and long-term marker gene expression in cells with characteristics of both immature type B cells and migrating precursor cells. After migration along the rostral migratory stream and differentiation, the number of enhanced green fluorescent protein (eGFP)-expressing granular and periglomerular interneurons increased over time in the ipsilateral olfactory bulb. Moreover, the number of eGFP-labeled neuronal progenitor cells in the SVZ increased over time. By intraventricular injection of lentiviral vectors we could restrict gene transfer to ependymal cells and type B astroglial-like stem cells. In conclusion, lentiviral vectors surpass retroviral vectors in efficient long-term in vivo marking of subventricular zone stem cells for basic research and therapeutic applications.

In vivo transcriptional profile analysis reveals RNA splicing and chromatin remodeling as prominent processes for adult neurogenesis

Neural stem cells and neurogenesis persist in the adult mammalian brain subventricular zone (SVZ). Cells born in the rodent SVZ migrate to the olfactory bulb (Ob) where they differentiate into interneurons. To determine the gene expression and functional profile of SVZ neurogenesis, we performed three complementary sets of transcriptional analysis experiments using Affymetrix GeneChips: (1) comparison of adult mouse SVZ and Ob gene expression profiles with those of the striatum, cerebral cortex, and hippocampus; (2) profiling of SVZ stem cells and ependyma isolated by fluorescent-activated cell sorting (FACS); and (3) analysis of gene expression changes during in vivo SVZ regeneration after anti-mitotic treatment. Gene Ontology (GO) analysis of data from these three separate approaches showed that in adult SVZ neurogenesis, RNA splicing and chromatin remodeling are biological processes as statistically significant as cell proliferation, transcription, and neurogenesis. In non-neurogenic brain regions, RNA splicing and chromatin remodeling were not prominent processes. Fourteen mRNA splicing factors including Sf3b1, Sfrs2, Lsm4, and Khdrbs1/Sam68 were detected along with 9 chromatin remodeling genes including Mll, Bmi1, Smarcad1, Baf53a, and Hat1. We validated the transcriptional profile data with Northern blot analysis and in situ hybridization. The data greatly expand the catalogue of cell cycle components, transcription factors, and migration genes for adult SVZ neurogenesis and reveal RNA splicing and chromatin remodeling as prominent biological processes for these germinal cells.

EphB2-Fc promotes activation of endogenous neural stem cells after cerebral cortex infarction: experimental with hypertensive rats

To explore the effects of intraventricular injection of EphB2-Fc on activation of inherent neural stem cells after cerebral cortex infarction. Stroke-prone renovascular hypertension model was established in 96 SD rats by two-kidney, two-clip method. Middle cerebral artery occlusion (MCAO) model was established in 72 of these 96 stroke-prone renovascular hypertensive rats and the other 24 rats were used as sham operation group. Then the 72 rats were randomly divided into 3 equal groups: cerebral infarction group without any treatment after the MCAO, MCAO + EphB2-Fc group undergoing stereotaxical infusion of EphB2-Fc at the dose of 20 microl x 200 microg/ml into the lateral ventricle 4 days after the distal ligation of right middle cerebral artery, and MCAO + IgG-Fc group undergoing stereotaxical infusion of IgG-Fc at the dose of 20 microl x 200 microg/ml into the lateral ventricle 4 days after the distal ligation of right middle cerebral artery. By the ends of the first and fourth weeks after the MCAO procedure 12 rats from each group were killed and their brains were taken out to undergo in situ hybridization, immunohistochemistry and Western blotting analysis in order to determine the expression of EphB2 protein and mRNA, nestin and polysialic acid-neural cell adhesion molecule (PSA-NCAM). One week after the distal ligation of right middle cerebral artery, the EphB2 protein and mRNA expression levels in the ipsilateral cortex and subventricular zone (SVZ) of the cerebral infraction group were both lower than those of the sham operation group (P < 0.05), such levels of the MCAO + EphB2-Fc group were higher than those of the MCAO + IgG-Fc group (both P < 0.05), but there was no significant difference between the cerebral infraction group and IgG-Fc group (both P > 0.05), and there were no differences in such levels between the cerebral infarction group and MCAO + IgG-Fc group (both P > 0.05); the nestin and PSA-NCAM expression levels in the ipsilateral SVZ of the cerebral infraction group were both higher than those of the sham operation group (both P < 0.05), such levels of the MCAO + EphB2-Fc group were both higher than those of the MCAO + IgG-Fc group (both P < 0.05), and migration of PSA-NCAM positive cells to corpus callosum could be seen. Four weeks after, there were no significant differences in the expression levels of EphB2 protein and mRNA among different groups (all P > 0.05), the nestin and PSA-NCAM expression levels in the ipsilateral SVZ decreased in all groups, there were no significant differences in the expression of nestin among all groups, but the PSA-NCAM expression in the ipsilateral SVZ of the cerebral infraction group was still higher than that of the sham operation group. Disruption of EphB2 signal promotes the proliferation and migration of endogenous neural stem cells in the SVZ after cerebral cortex infarction.

Neurogenesis in the adult rat brain after intermittent hypoxia

Intermittent hypoxia has been found to prevent brain injury and to have a protective role in the CNS. To address the possible causes of this phenomenon, we made investigative effort to find out whether intermittent hypoxia affects neurogenesis in the adult rat brain by examining the newly divided cells in the subventricular zone (SVZ) and dentate gyrus (DG). The adult rats were treated with 3000 and 5000 m high altitude 4 h per day for 2 weeks consecutively. 5-Bromo-2-deoxyuridine-5-monophosphate (BrdU) immunocytochemistry demonstrated that the BrdU-labeled cells in the SVZ and DG increased after 3000 and 5000 m intermittent hypoxia. The number of BrdU-labeled cells in the SVZ returned to normal level 4 weeks following intermittent hypoxia. However, the BrdU-labeled cells in the DG had a twofold increase 4 weeks subsequent to intermittent hypoxia. From these data, we conclude that intermittent hypoxia facilitates the proliferation of neural stem cells in situ, and that the newly divided cells in the SVZ and DG react differently to hypoxia. We are convinced by these findings that the proliferation of neural stem cells in SVZ and DG may contribute to adaptive changes following intermittent hypoxia.

Sonic hedgehog controls stem cell behavior in the postnatal and adult brain

Sonic hedgehog (Shh) signaling controls many aspects of ontogeny, orchestrating congruent growth and patterning. During brain development, Shh regulates early ventral patterning while later on it is critical for the regulation of precursor proliferation in the dorsal brain, namely in the neocortex, tectum and cerebellum. We have recently shown that Shh also controls the behavior of cells with stem cell properties in the mouse embryonic neocortex, and additional studies have implicated it in the control of cell proliferation in the adult ventral forebrain and in the hippocampus. However, it remains unclear whether it regulates adult stem cell lineages in an equivalent manner. Similarly, it is not known which cells respond to Shh signaling in stem cell niches. Here we demonstrate that Shh is required for cell proliferation in the mouse forebrain's subventricular zone (SVZ) stem cell niche and for the production of new olfactory interneurons in vivo. We identify two populations of Gli1+ Shh signaling responding cells: GFAP+ SVZ stem cells and GFAP- precursors. Consistently, we show that Shh regulates the self-renewal of neurosphere-forming stem cells and that it modulates proliferation of SVZ lineages by acting as a mitogen in cooperation with epidermal growth factor (EGF). Together, our data demonstrate a critical and conserved role of Shh signaling in the regulation of stem cell lineages in the adult mammalian brain, highlight the subventricular stem cell astrocytes and their more abundant derived precursors as in vivo targets of Shh signaling, and demonstrate the requirement for Shh signaling in postnatal and adult neurogenesis.

Effects of epidermal growth factor on the movement and differentiation of neural stem cells of subventricular zone in cerebral infarction rats

成年动物脑梗死后,脑室管膜下区(subventricular zone, SVZ)的神经干细胞(neural stem cell, NSC)虽然有增殖和迁徙反应,但分化为神经元的数量太少而难以改善神经功能[1].外源性表皮生长因子(epidermal growth factor,EGF)可促进正常成年鼠SVZ内NSC的增殖而改善认知行为能力[2],表明EGF可作为活体成年脑SVZ内NSC的调控因素之一.本实验研究脑梗死大鼠脑室内注入外源性EGF对SVZ内NSC增殖、迁徙和分化的作用,并探讨梗死灶边缘增生星形胶质细胞的来源。

Radial glia give rise to adult neural stem cells in the subventricular zone.

Neural stem cells with the characteristics of astrocytes persist in the subventricular zone (SVZ) of the juvenile and adult brain. These cells generate large numbers of new neurons that migrate through the rostral migratory stream to the olfactory bulb. The developmental origin of adult neural stem cells is not known. Here, we describe a lox-Cre-based technique to specifically and permanently label a restricted population of striatal radial glia in newborn mice. Within the first few days after labeling, these radial glial cells gave rise to neurons, oligodendrocytes, and astrocytes, including astrocytes in the SVZ. Remarkably, the rostral migratory stream contained labeled migratory neuroblasts at all ages examined, including 150-day-old mice. Labeling dividing cells with the S-phase marker BrdUrd showed that new neurons continue to be produced in the adult by precursors ultimately derived from radial glia. Furthermore, both radial glia in neonates and radial glia-derived cells in the adult lateral ventricular wall generated self-renewing, multipotent neurospheres. These results demonstrate that radial glial cells not only serve as progenitors for many neurons and glial cells soon after birth but also give rise to adult SVZ stem cells that continue to produce neurons throughout adult life. This study identifies and provides a method to genetically modify the lineage that links neonatal and adult neural stem cells.

Mash1 specifies neurons and oligodendrocytes in the postnatal brain

Progenitors in the telencephalic subventricular zone (SVZ) remain mitotically active throughout life, and produce different cell types at embryonic, postnatal and adult stages. Here we show that Mash1, an important proneural gene in the embryonic telencephalon, is broadly expressed in the postnatal SVZ, in progenitors for both neuronal and oligodendrocyte lineages. Moreover, Mash1 is required at birth for the generation of a large fraction of neuronal and oligodendrocyte precursors from the olfactory bulb. Clonal analysis in culture and transplantation experiments in postnatal brain demonstrate that this phenotype reflects a cell-autonomous function of Mash1 in specification of these two lineages. The conservation of Mash1 function in the postnatal SVZ suggests that the same transcription mechanisms operate throughout life to specify cell fates in this structure, and that the profound changes in the cell types produced reflect changes in the signalling environment of the SVZ.

Gene expression changes in the course of neural progenitor cell differentiation.

The molecular changes underlying neural progenitor differentiation are essentially unknown. We applied cDNA microarrays with 13,627 clones to measure dynamic gene expression changes during the in vitro differentiation of neural progenitor cells that were isolated from the subventricular zone of postnatal day 7 mice and grown in vitro as neurospheres. In two experimental series in which we withdrew epidermal growth factor and added the neurotrophins Neurotrophin-4 or BDNF, four time points were investigated: undifferentiated cells grown as neurospheres, and cells 24, 48, and 96 hr after differentiation. Expression changes of selected genes were confirmed by semiquantitative RT-PCR. Ten different groups of gene expression dynamics obtained by cluster analysis are described. To correlate selected gene expression changes to the localization of respective proteins, we performed immunostainings of cultured neurospheres and of brain sections from adult mice. Our results provide new insights into the genetic program of neural progenitor differentiation and give strong hints to as yet unknown cellular communications within the adult subventricular zone stem cell niche.

Unique astrocyte ribbon in adult human brain contains neural stem cells but lacks chain migration.

The subventricular zone (SVZ) is a principal source of adult neural stem cells in the rodent brain, generating thousands of olfactory bulb neurons every day. If the adult human brain contains a comparable germinal region, this could have considerable implications for future neuroregenerative therapy. Stem cells have been isolated from the human brain, but the identity, organization and function of adult neural stem cells in the human SVZ are unknown. Here we describe a ribbon of SVZ astrocytes lining the lateral ventricles of the adult human brain that proliferate in vivo and behave as multipotent progenitor cells in vitro. This astrocytic ribbon has not been observed in other vertebrates studied. Unexpectedly, we find no evidence of chains of migrating neuroblasts in the SVZ or in the pathway to the olfactory bulb. Our work identifies SVZ astrocytes as neural stem cells in a niche of unique organization in the adult human brain.

Telomerase activity in the subventricular zone of adult mice

The subventricular zone (SVZ) is the most active site for the production of new neurons in the adult mouse brain. Neural stem cells in the adult SVZ give rise to neuroblasts that travel via the rostral migratory stream (RMS) to the olfactory bulb, where they differentiate into interneurons. The enzyme telomerase has been identified in other population of stem cells and is necessary for the synthesis of telomeric DNA to prevent chromosomal shortening, end-to-end fusions, and apoptosis during successive rounds of cell division. However, previous studies have failed to detect telomerase in the adult mammalian brain. Here we demonstrate that telomerase is expressed by all brain regions shortly after birth, but becomes restricted to the SVZ and olfactory bulb in the adult mouse brain. Cultures of neural precursor cells or of migratory neuroblasts purified from the SVZ were each found to possess telomerase activity. After elimination of migrating neuroblasts and immature precursor cells in vivo by treatment with cytosine-β- d-arabinofuranoside (Ara-C), telomerase activity was still detectable in the remaining SVZ, which includes a population of neural stem cells. Following withdrawal of Ara-C, telomerase activity subsequently increased with a time course that parallels regeneration of the SVZ network and RMS. Finally, intracranial surgery alone, which has previously been shown to increase the number of cells in the SVZ, produced higher telomerase levels in the SVZ. We conclude that telomerase is active in neural precursor cells of the adult mouse and suggest that its regulation is an important parameter for cellular proliferation to occur in the mammalian brain.

Transgenic overexpression of BMP4 increases astroglial and decreases oligodendroglial lineage commitment

Bone morphogenetic proteins (BMPs) promote astrocytic differentiation of cultured subventricular zone stem cells. To determine whether BMPs regulate the astrocytic lineage in vivo, transgenic mice were constructed that overexpress BMP4 under control of the neuron-specific enolase (NSE) promoter. Overexpression of BMP4 was first detectable by Western analysis on embryonic day 16 and persisted into the adult. The overexpression of BMP4 resulted in a remarkable 40% increase in the density of astrocytes in multiple brain regions accompanied by a decrease in the density of oligodendrocytes ranging between 11 and 26%, depending on the brain region and the developmental stage. No changes in neuron numbers or the pattern of myelination were detected, and there were no gross structural abnormalities. Similar phenotypes were observed in three independently derived transgenic lines. Coculture of transgenic neurons with neural progenitor cells significantly enhanced astrocytic lineage commitment by the progenitors; this effect was blocked by the BMP inhibitor Noggin, indicating that the stimulation of astrogliogenesis was due to BMP4 release by the transgenic neurons. These observations suggest that BMP4 directs progenitor cells in vivo to commit to the astrocytic rather than the oligodendroglial lineage. Further, differentiation of radial glial cells into astrocytes was accelerated, suggesting that radial glia were a source of at least some of the supernumerary astrocytes. Therefore, BMPs are likely important mediators of astrocyte development in vivo.

LeX/ssea-1 Is Expressed by Adult Mouse CNS Stem Cells, Identifying Them as Nonependymal

Adult neural stem cells are rare, and little is known about their unique characteristics, leaving their in vivo identity enigmatic. We show that Lewis X (LeX), a carbohydrate expressed by embryonic pluripotent stem cells, is made by adult mouse subventricular zone (SVZ) stem cells and shed into their environment. Only 4% of acutely isolated SVZ cells are LeX +; this subpopulation, purified by FACS, contains the SVZ stem cells. Ependymal cells are LeX −, and purified ependymal cells do not make neurospheres, resolving the controversial claim that these are stem cells. Thus, LeX expression by adult CNS stem cells aids their in vivo identification, allows their enrichment, and raises new questions about the role of this unusual carbohydrate in stem cell biology.

Symposium 1: Regulation of Neural Development by BMP and Activin Family Members. BMP regulation of stem cell differentiation

The effects of BMP family members on stem cell lineage commitment depend upon the developmental age of the stem cell. BMP4 promotes apoptosis of early ventricular zone (VZ) stem cells, neuronal differentiation of later stage VZ cells, and astroglial differentiation of subventricular zone (SVZ) cells. BMP4 inhibits oligodendroglial lineage commitment at all stages of development. The effects of BMP4 in promoting commitment to a specific lineage reflect active suppression of alternate lineages by transcriptional inhibitors including ID and HEY family members and others. For example, BMP mediated increases in ID expression in SVZ stem cells suppress both oligodendroglial and neuronal differentiation. Similarly HEY 1 expression in SVZ cells suppresses neuronal differentiation, whereas HEYL expression by VZ cells inhibits glial differentiation and promotes neurogenesis. The differing effects of the BMPs on VZ and SVZ stem cells reflect also differences in the complement of transcription factors that are expressed. For example, VZ stem cells express high levels of neurogenin and HEY L whereas SVZ stem cells express lower levels of these factors but higher levels of HEY1. Thus lineage commitment by stem cells reflects interplay among stimulatory and inhibitory transcription factors, and responses to the BMPs depend upon the repertoire of transcription factors already expressed by the cell.

Noggin Antagonizes BMP Signaling to Create a Niche for Adult Neurogenesis

Large numbers of new neurons are born continuously in the adult subventricular zone (SVZ). The molecular niche of SVZ stem cells is poorly understood. Here, we show that the bone morphogenetic protein (BMP) antagonist Noggin is expressed by ependymal cells adjacent to the SVZ. SVZ cells were found to express BMPs as well as their cognate receptors. BMPs potently inhibited neurogenesis both in vitro and in vivo. BMP signaling cell-autonomously blocked the production of neurons by SVZ precursors by directing glial differentiation. Purified mouse Noggin protein promoted neurogenesis in vitro and inhibited glial cell differentiation. Ectopic Noggin promoted neuronal differentiation of SVZ cells grafted to the striatum. We thus propose that ependymal Noggin production creates a neurogenic environment in the adjacent SVZ by blocking endogenous BMP signaling.

Architecture and cell types of the adult subventricular zone: in search of the stem cells.

Neural stem cells are maintained in the subventricular zone (SVZ) of the adult mammalian brain. Here, we review the cellular organization of this germinal layer and propose lineage relationships of the three main cell types found in this area. The majority of cells in the adult SVZ are migrating neuroblasts (type A cells) that continue to proliferate. These cells form an extensive network of tangentially oriented pathways throughout the lateral wall of the lateral ventricle. Type A cells move long distances through this network at high speeds by means of chain migration. Cells in the SVZ network enter the rostral migratory stream (RMS) and migrate anteriorly into the olfactory bulb, where they differentiate into interneurons. The chains of type A cells are ensheathed by slowly proliferating astrocytes (type B cells), the second most common cell type in this germinal layer. The most actively proliferating cells in the SVZ, type C, form small clusters dispersed throughout the network. These foci of proliferating type C cells are in close proximity to chains of type A cells. We discuss possible lineage relationships among these cells and hypothesize which are the neural stem cells in the adult SVZ. In addition, we suggest that interactions between type A, B, and C cells may regulate proliferation and initial differentiation within this germinal layer.