neural stem cell niches and homing: recruitment and integration

Volume 51, Number 1 2010 3

Abstract

Considerable attention has focused on the study of neural stem cells (NSCs) as therapy for neurodegenerative diseases. The mammalian brain harbors NSCs throughout life mainly in the subventricular zone (SVZ) as well as the subgranular zone. NSCs in the SVZ are a specialized subpopulation of astro-cytes that maintain contact with the ventricle and vascular structures. Components of the SVZ microenvironment, or niche, include intercellular interactions, extracellular matrix proteins, and soluble factors, all of which aid in NSC prolif-eration, self-renewal, and multipotentiality. Multiple studies demonstrate that endogenous neurogenesis responds to insults such as ischemic stroke, multiple sclerosis and other neurode-generative diseases, and even brain tumors, supporting the existence of remarkable plasticity and signifi cant regenerative potential in the mammalian brain. Further, in response to re-cruitment cues from damaged brain tissue NSCs not only “home” to sites of disease but also integrate into functional tissues and appear to acquire the morphological and physio-logical properties of neurons, astrocytes, and oligodendro-cytes. In this review we focus on neurogenesis in the SVZ and on recruitment cues that promote homing and integration of NSCs to sites of disease in the brain. We also discuss animal models of important human neurodegenerative diseases in which transplantation of neural stem cells has been tested.

Key Words: animal models; central nervous system; hom-ing; stem cells; neurodegeneration; niche; recruitment; re-generation; subventricular zone

Tomás Garzón-Muvdi and Alfredo Quiñones-Hinojosa

Alfredo Quiñones-Hinojosa, MD, is Associate Professor of Neurological Surgery and Oncology and Tomás Garzón-Muvdi, PhD, is a postdoctoral research fellow, both in the Brain Stem Cell Laboratory of the Department of Neurosurgery at the Johns Hopkins Hospital in Baltimore, Maryland.

Address correspondence and reprint requests to Dr. Alfredo Quiñones-Hinojosa, The Johns Hopkins Hospital, Department of Neurosurgery, Brain Stem Cell Laboratory, Johns Hopkins University, CRB II, 1550 Orleans Street – Room 247, Baltimore, MD 21231 or email [email protected].

1Abbreviations used in this article: ALS, amyotrophic lateral sclerosis; CNS, central nervous system; GDNF, glial-derived neurotrophic factor; GFAP, glial fi brillary astrocytic protein; IL, interleukin; MS, multiple sclerosis; NSC, neural stem cell; PD, Parkinson’s disease; PDGF, platelet-derived growth factor; RMS, rostral migratory stream; SDF-1α, stromal-derived factor 1α; SVZ, subventricular zone

Neural Stem Cell Niches and Homing: Recruitment and Integration into Functional Tissues

Introduction

Stem cells possess intrinsic properties of unlimited self-renewal as well as the ability to differentiate into differ-ent cell types and therefore constitute an excellent and

appealing resource for application in regenerative medicine. Neural stem cells (NSCs1) show tropism to sites of pathology in the central nervous system (CNS1); such pathologies in-clude ischemic stroke (Pastori et al. 2008; Shyu et al. 2008), gliomas (Gutova et al. 2008; Honeth et al. 2006; Tyler et al. 2008; Zhao et al. 2008a), and multiple sclerosis (MS1) (Aharonowiz et al. 2008; Guan et al. 2008; Snethen et al. 2008). In addition, NSCs change disease progression when transplanted in animal models of amyotrophic lateral sclero-sis (ALS1) (Corti et al. 2007a), Parkinson’s disease (PD1) (Bjugstad et al. 2008), and spinal cord injuries (Enzmann et al. 2006; Obermair et al. 2008). These remarkable abilities make NSCs an optimal tool for the treatment of CNS diseases that require a regenerative approach, either by integration into damaged tissue and replacement of missing cells or as deliv-ery vehicles for drugs, growth factors, or functional proteins.

An understanding of the mechanisms involved in the mi-gration and homing of NSCs to the site of injury or disease is necessary to apply this therapeutic strategy for neurodegen-erative diseases. The objective of this review is to describe the features of the normal neurogenic niche in the adult mam-malian subventricular zone (SVZ1) as well as the factors that promote (1) NSC homing and recruitment to a site of disease and (2) the integration of NSCs into functional tissues in dif-ferent animal models of human neurological disease.

Neural Stem Cells in the Subventricular Zone

The hallmark characteristics of NSCs are their ability to self-renew, proliferate, and generate multiple cellular lineages, such as neurons, astrocytes, and oligodendrocytes both in vitro and in vivo (Laywell et al. 2007). The concept of the brain as a dormant organ has been challenged since the 1960s, when Altman and Das (1965, 1966) identifi ed prolif-erating cells in the hippocampal dentate gyrus of neonate rats using tritiated thymidine. Later, Goldman and Nottebohm (1983) demonstrated the presence of neurogenesis in the ventricular zone of the adult female canary. Since then, neu-rogenesis in the adult brain and its potential role in regenera-tion have received substantial attention.

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NSCs are present in the CNS throughout life in the adult human brain, in both the SVZ (Quiñones-Hinojosa and Chaichana 2007; Quiñones-Hinojosa et al. 2007) and the hippocampus (Gage et al. 1998). Given the prominent mi-gration of SVZ neuroblasts to the olfactory bulb through the rostral migratory stream (RMS1), the signifi cance of this neurogenic niche, and its potential applications to regenera-tive medicine, we focus our review on the SVZ (Lledo et al. 2008; Pencea et al. 2001). Excellent reviews on the hippo-campal neurogenic niche are available (Abrous et al. 2005; Ming and Song 2005).

In the SVZ, cells that express glial fi brillary astrocytic protein (GFAP1) constitute the genuine NSCs (Doetsch et al. 1999a). These semiquiescent cells combine the expression of GFAP, traditionally related to astrocytes (Ludwin et al. 1976), and nestin, a marker for immature neural cells (Gates et al. 1995; Lendahl et al. 1990). NSCs have been isolated from the SVZ in the mouse (Lois and Alvarez-Buylla 1994), rat (Palmer et al. 1995), and human (Sanai et al. 2004), among other species.

Neural Stem Cell Niches

A stem cell niche is a microenvironment that is able to main-tain the population of stem cells away from differentiation stimuli and apoptotic signals in a stable balance with ade-quate stem cell proliferation (Moore and Lemischka 2006). The niche comprises cellular structures, extracellular matrix proteins, and soluble factors (Alvarez-Buylla and Lim 2004). Evidence for the existence of neurogenic niches comes in part from the fi nding that NSCs transplanted to a neurogenic region proliferate, migrate, and integrate into the circuitry, whereas NSCs injected in nonneurogenic regions of the ro-dent brain do not proliferate and differentiate mainly into glia (Doetsch and Alvarez-Buylla 1996; Herrera et al. 1999). The SVZ is one of the main niches that has been the subject of study for some of the properties mentioned below.

Cytoarchitecture of the Subventricular Zone

The SVZ is located in the lateral walls of the lateral ventri-cles and contains ependymal cells, astrocytes, neuroblasts, and transit-amplifying cells (Alvarez-Buylla and Garcia-Verdugo 2002). A layer of ependymal cells lines the ventric-ular surface and consists of E1 cells, with multiple basal bodies and multiple long cilia, and E2 cells, with two cilia and complex basal bodies that may act as mechanical or chemical sensors monitoring the composition and fl ow of cerebrospinal fl uid (CSF) (Mirzadeh et al. 2008) (Figure 1). Next are B1 and B2 cells, which are astrocytes; the B1 astro-cytes extend a process to maintain contact with the ventricle (Doetsch et al. 1997), express GFAP, and are considered to be the true NSCs (Doetsch et al. 1999a; Ihrie and Alvarez-Buylla 2008; Mirzadeh et al. 2008; Quiñones-Hinojosa et al. 2006; Sanai et al. 2004).

Cell-cell interactions occur in the wall of the lateral ven-tricle, in the fashion of a “pinwheel architecture,” referring

to the organization of the ependymal lining where processes of B1 astrocytes, in contact with the ventricle, are surrounded by E1 and E2 ependymal cells (Mirzadeh et al. 2008). As discussed by Mirzadeh and colleagues, this organization is not present in the ventricular wall of nonneurogenic regions, suggesting an important role for this intercellular interaction and for contact with the CSF in neurogenesis. B1 cells also extend a basal process that contacts vascular structures in the SVZ. The interactions of B1 cells with the ventricle and with blood vessels in the SVZ may help the cells react to signals that originate in both structures (Mirzadeh et al. 2008).

Type B2 astrocytes isolate migrating type A cells (also called migrating neuroblasts) from the striatum and, together with type B1 cells, ensheath them; however, they do not con-tact the ventricle or vascular structures (Doetsch et al. 1997). Type C or transit-amplifying cells, which originate from asymmetric division of type B cells, proliferate rapidly, giv-ing rise to migrating neuroblasts, which express β-tubulin III, a marker for neural progenitors, and polysialylated neu-ral cell adhesion molecule (PSA-NCAM), a marker for the migrating neuroblasts. The type A cells migrate and divide along tubes formed by GFAP-positive type B1 and B2 astro-cytes to the RMS and toward the olfactory bulb, where, in rodents (Doetsch et al. 1999b; Lois et al. 1996) and primates (Pencea et al. 2001), they differentiate into interneurons. A study by Gould and colleagues (1999) reported that in non-human primates newly generated neurons migrate to the cor-tex and differentiate into mature neurons. But controversy arose from this work because of the techniques used and the interpretation of the results—the evidence did not conclu-sively support the proposed conclusions (Nowakowski and Hayes 2000). Moreover, in a study using nonhuman primates Kornack and Rakic (2001) found that BrdU-labeled cells in the cortex did not have a neuronal phenotype and that the only newly generated neurons were in the hippocampus and olfactory bulb.

Although there are some similarities, the human SVZ is quite different from that of other species because of the pres-ence of a hypocellular gap and of a prominent “astrocytic ribbon” in the lateral wall of the lateral ventricles, described as a band of GFAP- and vimentin-positive cells with a stel-late morphology (Quiñones-Hinojosa et al. 2006). This as-trocytic ribbon is separated from the layer of ependymal cells by the hypocellular gap, where GFAP-positive pro-cesses are found (Quiñones-Hinojosa et al. 2006; Sanai et al. 2004). Isolated PSA-NCAM-positive cells, which label mi-grating neuroblasts, were seen in the SVZ adjacent to the length of the lateral ventricle, including the anterior, dorsal, and temporal horns, as well as in the body of the ventricle (Figure 2). Our group also found that astrocytes project pro-cesses to contact the ventricle (Quiñones-Hinojosa et al. 2006), similar to the rodent SVZ (Doetsch et al. 1999b). Re-searchers recently described a RMS-like structure in the human brain (Curtis et al. 2007), but because convincing evidence of migrating cells was lacking, the presence of this structure in the human brain remains controversial (Quiñones-Hinojosa et al. 2006; Sanai et al. 2004, 2007).



Vascular Structures and Extracellular Matrix Proteins in the SVZ

NSCs in the adult rodent SVZ are present in a vascular niche, where they interact closely with blood vessels and with other cells (Mirzadeh et al. 2008; Shen et al. 2008; Tavazoie et al. 2008). Shen and colleagues (2008) recently showed that NSCs, which express LeX and are labeled with GFAP promoter-driven green fl uorescent protein (GFP) expression, are located signifi cantly closer to blood vessels than cells that do not express these markers. In the same study, these cells retained BrdU labeling over a 24-day period, suggest-ing a slowly proliferative population of cells. Additionally, a rapidly proliferating cell population, labeled with markers of cell proliferation (Ki-67 and phosphohistone H3), was found near vascular structures in the SVZ. Contributions to the SVZ neurogenic niche by endothelial cells composing vas-cular structures are soluble factors such as pigment epithelium-derived factor (PEDF), brain-derived neurotrophic factor

Figure 1 Cytoarchitecture of the adult rodent subventricular zone (SVZ). Left upper panel: Illustration of a coronal section of the rodent brain at the level of the anterior horn of the lateral ventricles showing the localization of the subventricular zone in the lateral walls of the lateral ventricles. Left lower panel: Color key for different cellular components of the SVZ neurogenic niche. Right panel: Cytoarchitecture of the rodent SVZ, showing the “pinwheel architecture” where ependymal cells interact with the apical process of glial fi brillary astrocytic protein (GFAP)–positive B1 astrocytes, the true neural stem cells (NSCs). B1 astrocytes extend a basal process that contacts vascular structures in the SVZ. To-gether with B1 cells, B2 astrocytes ensheath migrating neuroblasts in their path into the rostral migratory stream. Ependymal cells secrete noggin and pigment epithelium-derived factor (PEDF), important factors in the maintenance of the neurogenic niche, along with fi broblast growth factor (FGF) secreted by GFAP-positive cells. Type C (DLX-positive) or transit-amplifying cells rapidly proliferate and give rise to migrating neuroblasts, or type A cells. Type A cells, which express polysialylated neural cell adhesion molecule (PSA-NCAM), release gamma-aminobu-tyric acid (GABA), which regulates their production and speed of migration through its action on B1 astrocytes. Finally, endothelial cells from the vascular structures in the SVZ secrete numerous factors shown to infl uence neurogenesis. BDNF, brain-derived neurotrophic factor; VEGF, vascular endothelial growth factor

(BDNF), erythropoietin (EPO), and vascular endothelial growth factor (VEGF) (Laguna Goya et al. 2008; Leventhal et al. 1999; Pumiglia and Temple 2006; Ramirez-Castillejo et al. 2006; Shingo et al. 2001) (more on these below).

Extracellular matrix proteins also play an important role in maintaining the SVZ neurogenic niche. Tenascin C, an extracellular matrix protein, is expressed in the embryonic and postnatal SVZ and modulates epidermal growth factor (EGF) receptor expression in the embryonic stage of brain development, thus regulating NSC responsiveness to epi-dermal growth factor (EGF) (Garcion et al. 2001, 2004; Peretto et al. 2005). Tenascin C also appears to play a role in the migration and proliferation of oligodendrocyte precur-sors by regulating their sensitivity to platelet-derived growth factor (PDGF1) (Garcion et al. 2001).

Laminin and collagen type 1 are expressed in the extra-cellular matrix of the SVZ (Mercier et al. 2002). Laminin is in contact with multiple astrocytic processes, blood ves-sels, and the ependymal layer of the ventricular wall and is


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neurospheres by increasing proliferation of NSCs and de-creasing apoptosis; laminin may thus play a role in NSC pro-liferation (Hall et al. 2008).

Other extracellular matrix proteins present in the SVZ are heparan and chondroitin sulphate proteoglycans (Riquelme et al. 2008) and LeX, a trisaccharide expressed by astrocytes in contact with the SVZ vasculature (Capela and Temple 2002). LeX binds fi broblast growth factor (FGF) and Wnt-1, possibly modulating their action on NSCs (Capela and Temple 2006; Riquelme et al. 2008). These ex-tracellular matrix structures may concentrate growth factors and may be important in the regulation of the microenviron-ment in the SVZ (Mercier et al. 2002).

Soluble Factors in the SVZ

Soluble factors participate in the maintenance of the SVZ neurogenic niche. Ependymal cells produce noggin, an an-tagonist of the bone morphogenic protein (BMP) signaling pathway (Lim et al. 2000), which regulates NSC differentia-tion. The presence of noggin prevents differentiation (Li and LoTurco 2000) and thus increases both the proliferation of astrocytic cells with stem cell properties (Bonaguidi et al. 2005) and neuroblast production (Lim et al. 2000).

Growth factors are important players in the regulation of NSC proliferation and self-renewal. SVZ stem cells express receptors for EGF and basic FGF, and stimulation with these two factors, at least in vitro, is capable of inducing prolifera-tion of NSCs (Gritti et al. 1999; Reynolds and Weiss 1992). EGF also acts on type C cells, turning them into multipotent stem cells and decreasing neuroblast production (Doetsch et al. 2002). Exogenous intraventricular application of these two growth factors in vivo is important in the proliferation and differentiation of NSCs (Kuhn et al. 1997). The expres-sion of FGF2 by GFAP- and nestin-expressing cells has been demonstrated (Belluardo et al. 2008; Mudo et al. 2007, 2009). Hepatocyte growth factor (HGF) also contributes to the maintenance of self-renewal and proliferation of NSCs in the SVZ and is expressed by nestin-expressing cells (i.e., NSCs) (Nicoleau et al. 2008).

Vascular structures in the SVZ also secrete soluble factors. Ramirez-Castillejo and colleagues (2006) show in vitro and in vivo that PEDF is secreted by endothelial cells of the vascular niche and that this factor is capable of maintaining NSC self-renewal and multipotency by decreasing the expression of the proneural gene Mash1 and increasing the expression of tran-scription factors such as Sox2 and Notch pathway molecules. It has been suggested that PEDF is one of the most important players in neurogenesis (Pumiglia and Temple 2006).

BDNF is secreted by endothelial cells, and coculture ex-periments suggest that the cells support neurogenesis through secretion of this growth factor (Leventhal et al. 1999). Also, EPO increases NSC proliferation and directs it toward the production of neuroblasts by upregulating the proneural gene Mash1 through the NF-κβ pathway (Shingo et al. 2001).

Other soluble factors involved in the regulation of NSC proliferation are neurotransmitters. Neuroblast production

Figure 2 Representation of the adult human subventricular zone (SVZ). The lateral wall of the lateral ventricle in the human brain contains neural stem cells throughout adult life. In the background is a confocal image of the astrocytes present in the SVZ. The ependy-mal layer (E) as well as astrocytes (B), microglia (C), oligodendro-cytes (D), neurons (A), and blood vessels (F) are nearby and interact with each other. Astrocytes (B) are in contact with cells in the ependy-mal layer (E) and blood vessels (F). Also shown is an oligodendro-cyte (D) myelinating a neuronal axon. The hypocellular gap, the space between the layer of ependymal cells (E) and cell bodies of type B astrocytes (B), contains mainly processes projecting from as-trocytes (G) in the astrocytic ribbon (not shown). (Illustration by Ian Suk; based on Quiñones-Hinojosa A, Sanai N, Soriano-Navarro M, Gonzalez-Perez O, Mirzadeh Z, Gil-Perotin S, Romero-Rodriguez R, Berger MS, Garcia-Verdugo JM, Alvarez-Buylla A. 2006. Cellular composition and cytoarchitecture of the adult human subventricular zone: A niche of neural stem cells. J Comp Neurol 494:415-434.)

associated with a fi broblast/macrophage network, which could be involved in the secretion of growth factors and thus regulate differentiation and migration of NSCs (Mercier et al. 2002; Shen et al. 2008). Further, it has been shown that the supplementation of laminin increases the formation of



is tightly regulated by a paracrine negative feedback mecha-nism through the action of gamma-aminobutyric acid (GABA), which is produced by neuroblasts acting in a nonsynaptic manner on B cells (Liu et al. 2005; Platel et al. 2008). SVZ astrocytes regulate the speed of migration of neuroblasts into the olfactory bulb by regulating the concen-tration of GABA to which neuroblasts are exposed (Bolteus and Bordey 2004). In addition, the increase in neuronal ac-tivity directs the fate of NSCs to a neuronal phenotype due to downregulation of “proglial” and upregulation of “proneu-ronal” genes (Deisseroth et al. 2004).

Sources of Neural Stem Cells

Transplantation of NSCs has been envisioned as a cure for neurologic disorders such as PD and ALS, among others (Aharonowiz et al. 2008; Morita et al. 2008; Mukhida et al. 2008; Suzuki and Svendsen 2008; Wang et al. 2007). The availability of NSCs for treating neurologic diseases is the fi rst consideration; we discuss endogenous neurogenesis and exogenous NSCs as possible sources for NSC-based treat-ment of neurodegenerative disorders (Table 1).

Endogenous Neural Stem Cells

Endogenously generated NSCs in the SVZ are suitable for use in the mammalian brain (Alvarez-Buylla and Garcia-Verdugo 2002; Alvarez-Buylla and Lim 2004; Doetsch 2003), but the use of such NSCs to treat neurologic disease may be diffi cult because of the number of cells available and

the distance they would have to migrate to the site of injury. Furthermore, if the neurologic disorder has a genetic back-ground, the same genetic traits would be present in endoge-nous NSCs, rendering this therapeutic strategy inadequate. The challenge is to understand the hidden regenerative po-tential present in the mammalian brain and to learn how to use it as a treatment for neurologic disease.

These practical challenges aside, there is ample evidence that endogenous neurogenesis reacts to brain lesions such as ischemia (Darsalia et al. 2005; Liu et al. 2009), MS (Snethen et al. 2008), and gliomas (Kendall et al. 2008; Zhao et al. 2008a). Studies show that new neurons are produced in the SVZ after a stroke (Arvidsson et al. 2002; Kuge et al. 2009)—new cells migrate and integrate into the damaged tissue, ex-pressing neuronal markers and acquiring a morphological phenotype that resembles neurons after experimental occlu-sion of the middle cerebral artery (Arvidsson et al. 2002). Other studies have shown an increase in neurogenesis after ischemic stroke (Parent et al. 2002; Yagita et al. 2001; Zhang et al. 2009). These studies provide evidence of the regenera-tive capacity present in the injured brain, but this potential does not seem to be suffi cient and different manipulations may be necessary to potentiate endogenous regeneration.

Manipulation of endogenous neurogenesis and “encour-agement” of migration to sites of injury are important in the therapeutic use of endogenous NSCs. Chemotactic and hu-moral factors produced during disease serve as homing cues that recruit NSCs to the site of injury (Ekdahl et al. 2009); HGF and stromal-derived factor 1α (SDF-1α1 or CXCL12), for example, have strong chemoattractant and proliferative properties on NSCs (Lan et al. 2008; Takeuchi et al. 2007).

Table 1 Sources of neural stem cells (NSCs)a

Source Culture method Identifi cation Reference

Endogenous subventricular zone

None CD133 Uchida et al. 2000

Nestin Lendahl et al. 1990LeX Capela and Temple 2002

Exogenous

Skin Neurospheres, EGF- and FGF- supplemented media

Nestin, CD133 Valenzuela et al. 2008Nestin Joannides et al. 2004

Nestin Toma et al. 2001 Embryonic stem cells Embryoid bodies Nestin Erceg et al. 2008 Embryonic neural stem cells

Neurospheres, EGF- and FGF-supplemented media

Nestin Zhang et al. 2009

Bone marrow and adipose-derived mesenchymal stem cells

Neurospheres, EGF- and FGF- supplemented media

Nestin Fu et al. 2008

Human fetal nervous system


Nestin Vescovi et al. 1999

Human adult nervous system


GFAP and Vimentin Sanai et al. 2004

Human postmortem brain Neurospheres, EGF- and FGF-supplemented media

GFAP, CD133, Sox-2, Nestin

Feldmann and Mattern 2006

aEGF, epidermal growth factor; FGF, fi broblast growth factor; GFAP, glial fi brillary astrocytic protein


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The use of a chemoattractant-bearing hydrogel enables the extended release of HGF in vitro, promoting recruitment of NSCs to the site of application (Zhao et al. 2008b). Overex-pression of CXCR4, the receptor for SDF-1α, may also in-crease migration of NSCs to sites of disease (Liu et al. 2008). Further studies are needed to exploit the endogenous regen-erative ability of the mammalian brain.

Exogenous Neural Stem Cells

NSCs can be obtained from multiple tissues—skin (Joannides et al. 2004; Toma et al. 2001; Valenzuela et al. 2008), embry-onic stem cells (Erceg et al. 2008), embryonic NSCs (Zhang et al. 2009), bone marrow and adipose-derived mesenchymal stem cells (Fu et al. 2008), induced pluripotent stem cells (Amabile and Messner 2009; Chambers et al. 2009), and fe-tal (Vescovi et al. 1999) and adult nervous systems (Alvarez-Buylla and Garcia-Verdugo 2002; Alvarez-Buylla and Lim 2004; Feldmann and Mattern 2006; Sanai et al. 2004). It is also possible to obtain NSCs from neurosurgical procedures (e.g., lobectomy during epilepsy surgery) and increase their number for long periods of time (Ayuso-Sacido et al. 2008; Chaichana et al. 2009). However, all of these sources and methods require further study to thoroughly characterize the resulting NSCs and assess their safety.

In order to isolate and expand NSCs, Reynolds and Weiss developed the neurosphere assay (Reynolds and Weiss 1992; Reynolds et al. 1992). A neurosphere is a clonal cluster of cells originated from the proliferation of a single NSC. To identify clonal structures that arise from true NSCs, the requisites of the neurosphere assay include the formation of secondary neuro-spheres from the dissociation of the initial neurosphere, testing for long-term self-renewal, and appropriate differentiation of the cells in these clonal structures into the three main lineages of cells present in the CNS (Gritti et al. 1995, 1996; Marshall et al. 2007; Reynolds and Weiss 1996; Reynolds et al. 1992). However, there is signifi cant variability in the culture condi-tions among different scientifi c groups; widespread use of this method of expansion will require the adoption of universal culture conditions and methods (Chaichana et al. 2006). Different groups have used specifi c phenotypic markers to prospectively identify NSCs—for example, CD133 (Barraud et al. 2007; Corti et al. 2007b; Peh et al. 2009; Tamaki et al. 2002; Uchida et al. 2000), LeX (Imura et al. 2006; Platel et al. 2009), and Notch-1, syndecan-1, and integrin β1 (Nagato et al. 2005). Physiological properties such as expression of

Figure 3 Culture, identifi cation, and manipulation of neural stem cells (NSCs). After isolation of NSCs from adult or embryonic tissue it is possible to culture and expand them using the neurosphere assay, in which NSCs are cultured in suspension as fl oating clonal clusters of cells, derived from the proliferation of a single putative NSC. After neurosphere dissociation, it is possible to sort them using fl uorescence-activated cell sorting (FACS) with markers that allow for the enrichment of NSCs in the cell population. After enrichment, NSCs can be modifi ed in multiple ways to increase self-renewal (immortalization), to deliver neuroprotective agents (brain-derived neurotrophic factor, or BDNF, and vascular endothelial growth factor, or VEGF), and to enhance homing abilities (through the overexpression of epidermal growth factor receptor, or EGFR, or chemokine receptor CXCR4). Differentiation into specifi c cell types entails the use of transcription factors and growth factors. After manipulation, the next steps are genetic characterization of the NSCs and assessment of their tumorigenicity. The original fi gure is in color and is available in the online posting of this article at www.ilarjournal.com. PDGF, platelet-derived growth factor; hTERT, human telomerase reverse transcriptase

ABCG transporters (Kim and Morhead 2003), responsiveness to growth factors in terms of migration (Ciccolini et al. 2005), and high aldehyde dehydrogenase activity (Cai et al. 2004; Corti et al. 2006) have also been used. But novel and specifi c means of NSC isolation are still lacking.

Supplementation of the culture media with soluble fac-tors when isolating and expanding NSCs in vitro is impor-tant. The addition of leukemia inhibitory factor (LIF) seems to maintain NSC proliferation for long periods (Carpenter et al. 1999). Genetic manipulation of isolated NSCs may be necessary to obtain suffi cient numbers of stem cells and achieve feasibility in NSC-based therapy (Ostenfeld et al. 2000). Certain methods for immortalizing human NSC lines render the cells tumorigenic, but the introduction of telo-merase reverse transcriptase (TERT) may avoid unwanted changes and chromosomal instability and result in cell lines of neural progenitors that can produce neurons (Roy et al. 2004, 2007). Transduction of NSCs with Myc resulted in the generation of cell lines capable of differentiation into neuronal and glial cells, but polyploidy occurred in some cell lines, refl ecting the ability of Myc to cause genetic insta-bility (Kerosuo et al. 2008; Kim 2007; Snyder et al. 1992).

It is essential to thoroughly characterize a cell line before starting human treatment, since isolated NSCs can become tumorigenic after serial passaging and transplantation (Shiras et al. 2007; Siebzehnrubl et al. 2008) (Figure 3). With further research, it may become possible to develop reliable and thoroughly characterized NSC lines for use in the treatment of neurodegenerative diseases.

Neural Stem Cell Homing and Recruitment to the Injury/Disease Site

NSC-based therapy represents an important treatment option for MS, ALS, and stroke (Chu et al. 2005; Corti et al. 2007a; Darsalia et al. 2007; Jin et al. 2005; Takahashi et al. 2008; Windrem et al. 2008; Zhu et al. 2005), as well as gliomas (Honeth et al. 2006; Kendall et al. 2008; Tyler et al. 2008), among other illnesses. An understanding of the mechanisms that allow NSCs to home into sites of disease in the brain is important for cell-based regenerative therapy.

Infl ammation is a key player in the homing and recruit-ment of NSCs to sites of CNS injury where factors such as SDF-1α, LIF, and interleukin (IL1)-6 are overexpressed (Banner et al. 1997; Bauer and Patterson 2006; Hill et al.


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2004; Suzuki et al. 2000). Alterations in the extracellular mi-lieu during disease or injury are distinct for each pathology, but a common feature of disease in the brain is infl ammation (McCoy and Tansey 2008; Pluchino and Martino 2005; Thored et al. 2006; Tuttolomondo et al. 2008). Factors syn-thesized by cells undergoing apoptosis can also affect neuro-genesis and thus neurogenic repair mechanisms, suggesting that the generation of molecular cues promotes proliferation and recruitment of NSCs to aid in regeneration at sites of disease (Banner et al. 1997; Bauer et al. 2007; Magavi et al. 2000) (Figure 4 and Table 2).

In the following sections we describe various homing signals.

Stromal-Derived Factor 1α, or CXCL12

Expression of SDF-1α, also known as CXCL12, has been dem-onstrated in MS (Calderon et al. 2006; McCandless et al. 2008),

neonatal ischemia and ischemic stroke (Hill et al. 2004; Miller et al. 2005; Robin et al. 2006; Thored et al. 2006), and gliomas (Zagzag et al. 2008). Imitola and colleagues (2004) demon-strated that astrocytes and endothelial cells of an ischemic area in the brain increase the expression of SDF-1α and found constitutive expression and activation of CXCR4, the receptor for SDF-1α, resulting in NSC migration toward ischemic brain explants. Exposure to SDF-1α enhances migration and prolif-eration of LeX-positive NSCs, which can differentiate into cells with neuronal phenotypes after transplantation (Corti et al. 2005). SDF-1α is upregulated in traumatic brain injury (Itoh et al. 2009) and in active MS lesions (Calderon et al. 2006; McCandless et al. 2008), suggesting a recruiting mechanism for NSCs to traumatic and MS lesions in the brain.

Leukemia Inhibitory Factor and Interleukin-6

LIF expression is increased by macrophages, microglia, and activated astrocytes after different types of damage to the brain, such as ischemia and traumatic brain injury (Banner et al. 1997; Bauer et al. 2003; Slevin et al. 2008; Suzuki et al. 2000). LIF increases NSC proliferation and promotes NSC self-renewal (Bauer and Patterson 2006) and has therefore been used to culture both human embryonic NSCs for long periods of time (Carpenter et al. 1999; Galli et al. 2000; Wright et al. 2003) and adult human NSCs from the olfac-tory bulb (Pagano et al. 2000). Other studies have confi rmed that the exposure of neurospheres to LIF promotes amplifi -cation and self-renewal of GFAP-expressing NSCs and de-creases proliferation of neuronal progenitors (Bauer et al. 2007; Bonaguidi et al. 2005). Similar results have been ob-tained with IL-6, another infl ammatory cytokine, which de-creases the proliferation of neuroblasts and enhances NSC self-renewal, as demonstrated in a transgenic mouse model of IL-6 overexpression (Vallieres et al. 2002). IL-6 may also be involved in the differentiation of NSCs into neurons (Barkho et al. 2006; Bauer et al. 2007).

Vascular Endothelial Growth Factor

VEGF expression increases during normal and tumoral an-giogenesis (Cross et al. 2003; Lambrechts and Carmeliet 2006) as well as in macrophages, neurons, and glia surround-ing the damaged area shortly after ischemia (Hayashi et al. 1997). NSCs migrate following a gradient of VEGF recruited by a chemotactic effect mediated through the activation of VEGF receptor 2 (Zhang et al. 2003). Infusion of VEGF in the contralateral hemisphere of the rodent brain promoted migration of transplanted NSCs across the corpus callosum to the site of infusion, and VEGF-neutralizing antibodies de-creased NSC migration signifi cantly (Schmidt et al. 2009). Additionally, Jin and colleagues have shown a VEGF-induced increase in neurogenesis in a rat model of cerebral ischemia (Sun et al. 2003) and after intraventricular infusion of VEGF (Jin et al. 2002). Further, VEGF signaling is involved in NSC tropism to gliomas (Zhao et al. 2008a). These data suggest

Figure 4 Illustration of homing cues that recruit neural stem cells (NSCs) to the site of pathology in the mammalian central nervous system. Endogenous and exogenous transplanted NSCs home to different sites of pathology. Cerebral ischemia and gliomas express stromal-derived factor 1α (SDF-1α), which re-cruits NSCs to the site of disease. Vascular endothelial growth factor (VEGF) is overexpressed in brain tissue at the periphery of ischemic tissue. When injected into brain parenchyma, VEGF and hepatocyte growth factor (HGF) promote migration of NSCs to the site of release even when cells are implanted in the contralat-eral hemisphere. Platelet-derived growth factor (PDGF) is over-expressed by immune cells at the site of lesion in an animal model of multiple sclerosis; its expression also increases in the striatum of a model of Huntington’s disease and after cerebral ischemia, serving as a homing cue for NSCs. NSC migration also occurs upon cortical neuronal apoptosis, suggesting a mechanism for recruitment of NSCs in amyotrophic lateral sclerosis (Chen J, Magavi SS, Macklis JD. 2004. Neurogenesis of corticospinal mo-tor neurons extending spinal projections in adult mice. Proc Natl Acad Sci U S A 101:16357-16362; Magavi SS, Leavitt BR, Mack-lis JD. 2000. Induction of neurogenesis in the neocortex of adult mice. Nature 405:951-955). The original fi gure is in color and is available in the online posting of this article at www.ilarjournal.com.



that VEGF plays a role in the proliferation, homing, and recruitment of NSCs to the site of injury.

Hepatocyte Growth Factor

In immortalized neural progenitor cells derived from human striatal embryonic tissues, HGF has a chemotactic effect on NSCs that migrate following a concentration gradient (Cacci et al. 2003; Lan et al. 2008). In neural progenitor cells of the olfactory bulb–RMS system the chemotactic effect of HGF is mediated through activation of the HGF/Met signaling pathway, suggesting that HGF is a guidance molecule for neuroblasts that migrate to the olfactory bulb (Garzotto et al. 2008). Recruitment of NSCs by HGF has been shown in vitro (Zhao et al. 2008b) and in animal models of spinal cord injury (Takeuchi et al. 2007). Pathologies where HGF expression is seen include animal models of cerebral isch-emia (Nagayama et al. 2004), gliomas (Kendall et al. 2008), and medulloblastomas (Shimato et al. 2007). Increased levels of HGF also are seen in the cerebrospinal fl uid of patients with PD, ALS, and Alzheimer’s disease (Tsuboi et al. 2002) and are upregulated in motoneurons of patients with ALS (Jiang et al. 2005). These studies suggest that a gradient in the concentration of HGF may be used to direct migration of NSCs to the site of disease.

Platelet-Derived Growth Factor

PDGF regulates oligodendroglial differentiation of NSCs and therefore could be useful in the treatment of demyelinating dis-eases of the CNS such as MS (Keyoung and Goldman 2007). Increases in the local production of PDGF by genetic manipu-lation enhance the homing of oligodendrocyte precursor cells to demyelinating lesions (Woodruff et al. 2004), and expres-sion of PSA-NCAM is important in the maintenance of this movement toward the source of PDGF (Armstrong et al. 1991; Zhang et al. 2004). In embryonic rat cortex cultured cells, PDGF exerted a chemotactic effect on nestin-positive cells, re-sulting in directed migration (Forsberg-Nilsson et al. 1998).

Increased expression of PDGF has been observed in animal models of Huntington’s disease after the creation of a lesion in the striatum with ibotenic acid (Sjoborg et al. 1998) and in ischemic brain injury (Iihara et al. 1994; Ohno et al. 1999). Also, PDGF is expressed by immune cells located in sites of disease in a model of MS (Koehler et al. 2008). These studies suggest that PDGF is important in the healing process after brain injury and that it may be important in the recruitment of NSCs to sites of injury.

The chemotactic effect of PDGF in normal SVZ-de-rived NSCs needs further study. It may be useful in the treatment of demyelinating diseases by enhancing NSC

Table 2 Homing signals to site of diseasea

Homing signal Pathology Effect on NSCs Cell source Reference

SDF-1α/ CXCL12

MS

Ischemia

GliomasTraumatic brain injury

Chemotactic/ proliferative

Astrocytes/endothelial cells

Calderon et al. 2006; McCandless et al. 2008Miller et al. 2005; Robin et al. 2006Zagzag et al. 2008Itoh et al. 2009

LIF

Cortical brain injuryIschemia

Increase in NSC proliferation and self-renewal

Macrophages, microglia, and reactive astrocytes

Banner et al. 1997

Slevin et al. 2008; Suzuki et al. 2000

IL-6Infl ammation Enhances NSC

self-renewalAstrocytes, microglia, activated lymphocytes

Barkho et al. 2006; Bauer et al. 2007

VEGFIschemiaGliomas

ChemotacticMacrophages, neurons, and glia

Hayashi et al. 1997Zhao et al. 2008b

HGF

Spinal cord injuryIschemiaGliomasALS

Chemotactic

Reactive astrocytes

Reactive astrocytesTumor cellsMotoneurons

Takeuchi et al. 2007

Nagayama et al. 2004Kendall et al. 2008Jiang et al. 2005

PDGF

Huntington’s diseaseMSIschemia

Chemotactic

Astrocytes

Immune cellsPeri-infarct neurons

Sjoborg et al. 1998

Koehler et al. 2008Ohno et al. 1999

Integrins Ischemia Vascular adhesion Activated endothelial cells

Prestoz et al. 2001

aALS, amyotrophic lateral sclerosis; HGF, hepatocyte growth factor; IL-6, interleukin-6; LIF, leukemia inhibitory factor; MS, multiple sclerosis; NSC, neural stem cell; PDGF, platelet-derived growth factor; SDF-1α, stromal derived factor 1α; VEGF, vascular endothelial growth factor


12 ILAR Journal

migration and differentiation into the oligodendroglial lin-eage. However, NSCs in the SVZ express PDGF receptor α and the fact that stimulation with PDGF induces tumor-like formations strongly suggests a role for PDGF signaling in tumorigenesis (Assanah et al. 2009; Jackson et al. 2006).

Integrins

Integrins, among the most important cell adhesion mole-cules, trigger the activation of diverse intracellular signaling pathways (Hynes 2002). There is evidence that such pathways overlap with those used by tyrosine kinase receptors such as growth factors (Legate et al. 2009), so it is conceivable that, as with the effects of growth factor activity on NSCs, integ-rins also may enhance their migration.

Expression of integrin α6β1 has been documented in the SVZ neurogenic niche and is important in the interaction be-tween NSCs and blood vessels in the SVZ (Doetsch 2003; Shen et al. 2008). Integrin α6β1 regulates chain migration of rodent NSCs derived from neurospheres, and blocking antibodies against these integrins prevents chain migration (Jacques et al. 1998). NSC migration to the site of injury is dependent on the expression of integrins, as has been demonstrated in a rodent model of cerebral ischemia, sug-gesting that integrin signaling may play a signifi cant role in NSC migration to places of injury in the CNS (Prestoz et al. 2001). Tumor necrosis factor α (TNF-α) is an important inflammatory mediator in ischemic brain injury and in-fl ammatory demyelinating disease (Fromont et al. 2009; Tuttolomondo et al. 2008). Using TNF-α-stimulated endothe-lial cells to simulate brain pathology, a recent study found that integrins contribute to the homing process of NSCs to the site of injury when administered intravascularly (Mueller et al. 2006).

The expression and activation of different receptor/chemokine combinations occur during NSC migration and homing to the site of injury. An interdependent relation-ship between the actions and effects of these signaling pathways determines migration of NSCs to sites of injury or disease in the brain and may contribute to regen eration.

Integration of Neural Stem Cells into Functional Tissues

Integration of endogenous NSCs from the SVZ into func-tional tissues has been documented in models of demyelina-tion and cortical neuron apoptosis (Chen et al. 2004; Magavi et al. 2000; Menn et al. 2006). In ischemic stroke, new neurons generated in the SVZ differentiate into GABAergic and cholinergic striatal neurons, form functional synapses with preexisting neurons, and exhibit neuronal electrophysi-ological properties (Hou et al. 2008). Neurogenesis and inte-gration of newly generated neurons can also be elicited after induction of apoptosis of cortical neurons; although functional integration was not assessed, generated neurons integrate morphologically into normal tissue (Magavi et al. 2000).

Exogenous CD133-positive NSCs derived from a human fetal brain are also able to integrate into normal tissues after in vitro expansion and transplantation into rodent models, showing differentiation and integration into the olfactory bulb, SVZ, hippocampus, and other regions of the rodent brain (Tamaki et al. 2002; Uchida et al. 2000). Sorted and isolated LeX/CXCR4-positive mouse NSCs administered intraven-tricularly as well as intravenously are able to differentiate into cells with neuronal phenotypes after transplantation (Corti et al. 2005). Furthermore, homing properties to the CNS are en-hanced after the intracerebral administration of SDF-1α (Corti et al. 2005). These studies suggest that exogenous transplanted neurons survive and migrate to injured areas in the brain and can later differentiate into functional cells.

Numerous studies have reported the results of NSC-based therapy and integration of transplanted cells into func-tional tissues in different animal models of MS (Akiyama et al. 2001; Ben-Hur et al. 2003; Einstein et al. 2003; Pluchino et al. 2003; Windrem et al. 2002), PD (Banner et al. 1997; Bjugstad et al. 2005, 2008; Hovakimyan et al. 2008; Oured-nik et al. 2002), HD (Lee et al. 2005a), ALS (Xu et al. 2009), and ischemic stroke (Darsalia et al. 2007; Hou et al. 2008; Jin et al. 2005; Takahashi et al. 2008).

Animal Models and Neural Stem Cell Therapy for Degenerative Diseases and Stroke

Animal models of human neurodegenerative diseases have been irreplaceable tools in efforts to advance both understand-ing of the pathophysiologic mechanisms of disease and thus research and development in stem cell–based therapeutic strat-egies. In this section we discuss such animal models and the results of their use in studies of NSC-based therapy (Table 3).

Multiple Sclerosis

MS is an infl ammatory autoimmune and demyelinating disease of the CNS. One of the animal models of MS relies on the generation of lesions in white matter tracts of the brain of rodents using lysolecithin injections (Arenella and Herndon 1984). This model has been used to study the sur-vival and migration of transplanted progenitor cells to the site of the lesion and has shown that these cells survive and migrate to injured areas in the brain, differentiate into oligo-dendrocytes, and start remyelination at the site of disease (Vignais et al. 1993; Windrem et al. 2002). More recently, a study showed that lysolecithin-induced demyelination of the corpus callosum increases the generation of oligodendrocyte precursors by SVZ stem cells and that these cells migrate to the site of demyelination, indicating an endogenous NSC-regenerative potential after demyelination (Menn et al. 2006).

Another widely used animal model of MS is the experi-mental autoimmune encephalomyelitis (EAE) model, in which



infl ammatory demyelination is generated after the injection of an encephalitogenic peptide (Mix et al. 2008). Intravenous or intracerebroventricular injection of NSCs in EAE mice showed the presence of transplanted cells in demyelinated areas of the brain as well as a decrease of demyelination in treated ani-mals, demonstrating clinical and neurophysiological improve-ment (Pluchino et al. 2003). Other studies with this model have shown that NSCs are able to home to demyelinating le-sions in the EAE rodent model and differentiate into oligoden-drocytic and astrocytic cells (Ben-Hur et al. 2003). Similar results have been obtained with the intraventricular injection of NSCs in the EAE mouse model (Einstein et al. 2003).

In a rat model that uses X-ray irradiation and ethidium bromide exposure of the rat spinal cord, transplantation of human SVZ-derived NSCs of patients with glioblastoma multiforme led to remyelination of axons and recovery in the conduction velocities (Akiyama et al. 2001). This study has signifi cant implications because an anatomical relationship between the SVZ and gliomas has revealed that patients with gliomas in contact with the SVZ have a shorter survival and have multifocal disease at the time of diagnosis, suggesting a possible origin of these tumors from SVZ NSCs (Barami et al. 2009; Chaichana et al. 2009; Lim et al. 2007).

The results with MS animal models show that trans-planted NSCs can improve disease progression and integrate into injured tissues to aid in regeneration.

Parkinson’s Disease

PD is characterized by the loss of dopaminergic input of cells projecting from the substantia nigra into the basal ganglia (Gupta et al. 2008). Two rodent models used to study NSC-based therapy for PD have shown that the application of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and 6-OHDA (6-hydroxidopamine) provokes cell death of dopaminergic neurons in the substantia nigra and induces parkinsonian symp-toms (Jenner and Marsden 1986; Mokry 1995). Ourednik and colleagues (2002) showed a benefi cial effect of the implanta-tion of NSCs into the midbrain of MPTP-treated rats, suggest-ing that NSCs, besides differentiating into dopaminergic neurons, express neuroprotective substances such as glial- derived neurotrophic factor (GDNF1), which translated to an improvement in PD symptoms. In a similar model of PD in primates, transplanted human NSCs increased tyrosine hydroxylase–positive cells in the striatum and migrated through the nigrostriatal pathway toward the substantia nigra (Banner et al. 1997; Bjugstad et al. 2005, 2008). Although the study did not include evaluation of the outcome after treatment, the results indicate that migration, integration, and regeneration of injured areas are possible with NSC-based treatment of PD.

In a recent study using a nonhuman primate PD model, implantation of undifferentiated human NSCs in the sub-stantia nigra and caudate nucleus reduced behavioral abnor-malities such as impaired walking, tightness of muscles, and slowed movement (Redmond et al. 2007); the authors suggested neuroprotection and dopaminergic differentiation

of the NSCs as the mechanisms responsible for improvement. In a rodent model, transplantation of expanded and differenti-ated mesencephalic precursors improved functional outcome (Studer et al. 1998). The same was true with the use of fl uores-cence-activated cell-sorted NSCs obtained from the mesen-cephalon of rodent embryos (Sawamoto et al. 2001). On the other hand, a study with mesencephalic NSCs transplanted intrastriatally showed that these cells differentiated into neu-rons and GFAP-positive cells but not into dopaminergic neu-rons in parkinsonian rats, although the animals did show an improvement in behavior and functionality (Hovakimyan et al. 2008). This improvement could be mediated by the neu-roprotective effect and expression of GDNF by transplanted cells as shown in a PD primate model (Emborg et al. 2008).

Insulin-like growth factor 1–releasing NSCs have a neuroprotective and benefi cial effect in the treatment of PD models (Ebert et al. 2008). Genetically modifi ed NSCs were induced to differentiate into dopaminergic neurons af-ter overexpression of Pitx3, an important transcription factor in do paminergic differentiation; improvement of behavioral outcome was seen after transplantation into a PD rodent model (O’Keeffe et al. 2008). Interestingly, there are no apparent differences between the use of embryonic or adult NSCs in the treatment of PD rodent models (Aponso et al. 2008). However, although the results with animal models have been promising, trials in human patients have not been successful, yielding marginal benefi t (Laguna Goya et al. 2008).

Huntington’s Disease

HD, characterized by the degeneration of medium spiny neu-rons in the striatum, presents with movement disorders (e.g., chorea), cognitive decline, and neuropsychiatric manifesta-tions (Haddad and Cummings 1997). Multiple animal models of HD have been developed to evaluate NSC therapy as a potential treatment for the disease (Kim et al. 2008; Vonsattel 2008). The commonly used R6/1 and -2 mouse models ex-press exon 1 of huntingtin with different CAG repeats, pro-viding a close reproduction of HD (Li et al. 2005).

The generation of these models involves the injection of glutamic acid analogues (e.g., kainic, ibotenic, and quino-linic acids) into the animal’s striatum to cause the excito-toxic cell death of neurons in this structure and thus produce characteristics similar to those of HD (Beal et al. 1991; Isacson et al. 1985). Human NSCs are then injected intrave-nously and home to the injury site, where they reduce striatal atrophy, differentiate into neurons, and improve functional outcome (Lee et al. 2005b). In a rat model of HD, involving the stereotactic transplantation of human fetal NSCs (iden-tifi ed by neurosphere formation) into the striatum, motor function improved (McBride et al. 2004). And researchers have recently reported that genetically modifi ed NSCs that produce GDNF protect striatal neurons from degeneration (Pineda et al. 2007). Thus different strategies are available for the treatment of this fatal disease.


14 ILAR Journal

Tab

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16 ILAR Journal

Amyotrophic Lateral Sclerosis

ALS is a neurodegenerative disease that affects motor neu-rons in the CNS and leads to paralysis and death. Because some cases of ALS have been related to mutations in Cu/Zn superoxide dismutase (SOD1) (Rosen et al. 1993), one of the most used animal models entails an overexpression of mu-tant SOD1 in mice, resulting in motor neuron degeneration, paralysis, and death at 5 to 6 months of age (Gurney et al. 1994). In this animal model, NSCs transplanted into the spinal cord differentiated and integrated structurally into the neuronal circuit in the spinal cord (Xu et al. 2009). Other studies have shown that NSCs exposed to different culture conditions and growth factors can differentiate into cholinergic neurons (Ren et al. 2006; Wang et al. 2006). Transplantation of NSCs, isolated by their expression of LeX and CXCR4 (using fl uorescence-activated cell sorting, or FACS), into an ALS transgenic rodent model delayed disease progression and increased the animals’ survival (Corti et al. 2007a). As discussed above, GDNF has a neuroprotective effect in other neurological diseases, and testing of NSC- mediated delivery of GDNF in ALS rodent models showed that transplanted NSCs apparently survive for a period of time and secrete GDNF, but no functional evaluation of the animals was done (Klein et al. 2005; Suzuki et al. 2007).

Ischemic Stroke

Most animal models of ischemic stroke entail occlusion of arterial blood supply to the brain by surgical techniques. Researchers have used these models to study the response of endogenous neurogenesis to stroke and found that hypoxic injury to the brain leads to increased neurogenesis in the SVZ (Arvidsson et al. 2002; Jin et al. 2001; Parent et al. 2002). Moreover, studies of the cues that increase neurogenesis and migration of these NSCs to the site of injury showed that SDF-1α and angiopoietin-1 contribute to the homing process of newly formed neural progenitors to the site of injury (Ohab et al. 2006). Intracerebral implantation of NSCs after ischemia is a feasible method of administration of regenerative therapy (Jin et al. 2005). Intravenously administered NSCs, previously sorted for the expression of a surface antigen CD49d, home to ischemic lesions in the brain and thus improve functional re-covery after ischemia (Guzman et al. 2008).

To study the different therapeutic effects of the adminis-tration of embryonic versus adult NSCs, Takahashi and colleagues (2008) treated rats subjected to middle cerebral artery occlusion with either type of stem cell and found that embryonic stem cells survive longer and in larger propor-tions than adult NSCs and that the administration of either cell line decreased the infarct size. A study by Darsalia and colleagues (2007) showed that transplanted human NSCs survive and differentiate into neurons, expressing different neuronal markers. Taken together these data suggest that NSC transplantation is a potential regenerative therapy for stroke.

Neural Stem Cell–Based Therapy for Brain Tumors

We have discussed the homing abilities of NSCs and the pos-sible cues that recruit these cells to sites of pathology in dif-ferent neurologic diseases. Endogenous NSCs home to sites of tumor cell implantation in a murine model of glioblas-toma; this accumulation of NSCs around the tumor corre-lates with the formation of smaller tumors and longer survival (Glass et al. 2005). Glass and colleagues (2005) also sug-gested an antitumorigenic property of NSCs by inducing apoptosis of tumor cells. Exogenous NSCs migrate to gliomas whether implanted in the brain or administered in-travenously (Aboody et al. 2000).

NSCs can be modifi ed to deliver different therapeutic molecules (Pineda et al. 2007; Suzuki et al. 2007). In the case of brain tumors, NSCs have been engineered to express cytosine deaminase (Aboody et al. 2000) and thymidine kinase (Li et al. 2007), two prodrug-converting enzymes; these studies showed that administration of engineered NSCs and the prodrug can decrease tumor growth. Researchers have also shown that NSCs can deliver biologi-cally active particles such as viruses (Herrlinger et al. 2000; Tyler et al. 2008), and that NSC-based delivery of an oncolytic adenovirus is more feasible than systemic admin-istration for the delivery of the therapeutic virus (Tyler et al. 2008). Finally, local delivery of immunologically active molecules by genetically modifi ed NSCs is possible. NSC delivery of IL-4 resulted in a signifi cant decrease in tumor size and increase in survival in a rodent model of gliosar-coma (Benedetti et al. 1999). Treatment with IL-12-secreting NSCs produced greater tumor infi ltration by T cells, sug-gesting active stimulation of the immune system by this cytokine (Ehtesham et al. 2002). Also, NSCs expressing TNF-related apoptosis-inducing ligand (TRAIL) resulted in increased tumor cell apoptosis and a decrease in tumor size (Ehtesham et al. 2002). These studies provide important evidence of another application for NSC-based therapy of neurologic disease.

Summary

Studies using animal models have revealed much about the process of neurogenesis in the mammalian brain and about different interactions in the SVZ. This review summarizes aspects of recruitment and integration of NSCs in the diseased mammalian brain. Cell-cell interactions and cell-extracellular matrix interactions are critical to this complex process, modulating proliferation, differentiation, and mi-gration of NSCs in both the normal and the diseased brain. Soluble molecules such as growth factors and cytokines present in the main neurogenic regions and at sites of disease in the CNS clearly contribute to the proliferation, homing, and recruitment of NSCs.

A complete understanding of the components, architec-ture, and interactions in normal and pathological neurogenic



niches is paramount for the creation of optimal conditions in vitro to expand and culture NSCs and use them in the treat-ment of multiple neurological diseases. Further characteriza-tion of different sources and administration routes of NSCs is also necessary. Specifi c markers of NSCs have not been found, but it is possible to enrich NSC populations by using markers such as CD133 or LeX. Finally, researchers must understand the mechanisms that promote not only the migra-tion and homing of NSCs to the site of injury but also their proliferation and self-renewal in order to develop the tools to genetically modify NSCs according to the needs of different patients and neurologic diseases.

Current Problems and Future Directions of Neural Stem Cell Therapy

Regenerative therapy for brain degenerative diseases is in its infancy. Further research is needed before successful treat-ment strategies are possible for the treatment of neurodegen-erative illnesses such as Parkinson’s, Huntington’s, ALS, and MS, among many others. Such strategies will require the iden-tifi cation of a reliable source of NSCs, whether endogenous, with the advantage of avoiding immune rejection issues, or exogenous, allowing for a better characterization of cells for use in cell-based therapies. Exogenous NSCs can also be ge-netically modifi ed to enhance their migratory abilities and to deliver growth factors or cytokines as vehicles for therapeutic agents; investigators have studied a variety of therapeutic ap-plications of genetically modifi ed NSCs—for example, the treatment of gliomas using interleukin and cytokine-releasing NSCs (Aboody et al. 2008), adenovirus-releasing NSCs that target gliomas (Tyler et al. 2008), and VEGF-expressing NSCs for the treatment of ischemic stroke (Lee et al. 2007).

Once researchers have identifi ed a reliable and consis-tent source of NSCs, it will be essential to determine whether transplanted cells can integrate into the normal anatomy of the damaged area. Some mechanisms for the integration of NSCs into neuronal networks have been studied in the con-text of brain development (Ge et al. 2008), but the issue of integration into normal neural circuits requires further study. Research has shown that NSCs transplanted into rodent brains are capable of integration into neuronal circuitry and have the phenotypical and electrical properties of neurons (Auerbach et al. 2000; Lundberg et al. 2002). Among the challenges to overcome are poor survival of transplanted NSCs and identifi cation of the best route to improve deliv-ery. Harnessing the full potential of NSCs requires much more insight into the mechanisms behind regeneration.

Acknowledgments

Our work is supported by the National Institutes of Health (grant NIH-K08NS05585), Howard Hughes Medical Institute (grant 57005932), Robert Wood Johnson Foundation (grant 63519), and Maryland Stem Cell Technology Development Corporation (Tedco-2007-MSCRFE-0139-00). Special thanks

to Hugo Guerrero-Cazares, Pragathi Achanta, Oscar Gonza-lez-Perez, Thomas Kosztowski, and Hasan Zaidi for critical comments and discussion of the review. We thank Satyen Tripathi and Ian Suk for preparing the illustrations. We apolo-gize to authors whose work is not cited in this review because of space constraints.

References

Aboody KS, Brown A, Rainov NG, Bower KA, Liu S, Yang W, Small JE, Herrlinger U, Ourednik V, Black PM, Breakefi eld XO, Snyder EY. 2000. Neural stem cells display extensive tropism for pathology in adult brain: Evidence from intracranial gliomas. Proc Natl Acad Sci U S A 97:12846-12851.

Aboody KS, Najbauer J, Danks MK. 2008. Stem and progenitor cell-mediated tumor selective gene therapy. Gene Ther 15:739-752.

Abrous DN, Koehl M, Le Moal M. 2005. Adult neurogenesis: From precur-sors to network and physiology. Physiol Rev 85:523-569.

Aharonowiz M, Einstein O, Fainstein N, Lassmann H, Reubinoff B, Ben-Hur T. 2008. Neuroprotective effect of transplanted human embryonic stem cell-derived neural precursors in an animal model of multiple scle-rosis. PLoS One 3:e3145.

Akiyama Y, Honmou O, Kato T, Uede T, Hashi K, Kocsis JD. 2001. Trans-plantation of clonal neural precursor cells derived from adult human brain establishes functional peripheral myelin in the rat spinal cord. Exp Neurol 167:27-39.

Altman J, Das GD. 1965. Autoradiographic and histological evidence of post-natal hippocampal neurogenesis in rats. J Comp Neurol 124:319-335.

Altman J, Das GD. 1966. Autoradiographic and histological studies of post-natal neurogenesis. I. A longitudinal investigation of the kinetics, migra-tion and transformation of cells incorporating tritiated thymidine in neonate rats, with special reference to postnatal neurogenesis in some brain regions. J Comp Neurol 126:337-389.

Alvarez-Buylla A, Garcia-Verdugo JM. 2002. Neurogenesis in adult sub-ventricular zone. J Neurosci 22:629-634.

Alvarez-Buylla A, Lim DA. 2004. For the long run: Maintaining germinal niches in the adult brain. Neuron 41:683-686.

Amabile G, Meissner A. 2009. Induced pluripotent stem cells: Current prog-ress and potential for regenerative medicine. Trends Mol Med 15:59-68.

Aponso PM, Faull RL, Connor B. 2008. Increased progenitor cell prolifera-tion and astrogenesis in the partial progressive 6-hydroxydopamine model of Parkinson’s disease. Neuroscience 151:1142-1153.

Arenella LS, Herndon RM. 1984. Mature oligodendrocytes: Division fol-lowing experimental demyelination in adult animals. Arch Neurol 41:1162-1165.

Armstrong R, Harvath L, Dubois-Dalcq M. 1991. Astrocytes and o-2a pro-genitors migrate toward distinct molecules in a microchemotaxis cham-ber. Ann N Y Acad Sci 633:520-522.

Arvidsson A, Collin T, Kirik D, Kokaia Z, Lindvall O. 2002. Neuronal re-placement from endogenous precursors in the adult brain after stroke. Nat Med 8:963-970.

Assanah MC, Bruce JN, Suzuki SO, Chen A, Goldman JE, Canoll P. PDGF stimulates the massive expansion of glial progenitors in the neonatal forebrain. Glia 57:1835-1847.

Auerbach JM, Eiden MV, McKay RD. 2000. Transplanted CNS stem cells form functional synapses in vivo. Eur J Neurosci 12:1696-1704.

Ayuso-Sacido A, Roy NS, Schwartz TH, Greenfi eld JP, Boockvar JA. 2008. Long-term expansion of adult human brain subventricular zone precur-sors. Neurosurgery 62:223-229; discussion 229-231.

Banner LR, Moayeri NN, Patterson PH. 1997. Leukemia inhibitory factor is expressed in astrocytes following cortical brain injury. Exp Neurol 147:1-9.

Barami K, Sloan AE, Rojiani A, Schell MJ, Staller A, Brem S. 2009. Relation-ship of gliomas to the ventricular walls. J Clin Neurosci 16:195-201.


18 ILAR Journal

Barkho BZ, Song H, Aimone JB, Smrt RD, Kuwabara T, Nakashima K, Gage FH, Zhao X. 2006. Identifi cation of astrocyte-expressed factors that modulate neural stem/progenitor cell differentiation. Stem Cells Dev 15:407-421.

Barraud P, Stott S, Mollgard K, Parmar M, Bjorklund A. 2007. In vitro characterization of a human neural progenitor cell coexpressing ssea4 and cd133. J Neurosci Res 85:250-259.

Bauer S, Patterson PH. 2006. Leukemia inhibitory factor promotes neural stem cell self-renewal in the adult brain. J Neurosci 26:12089-12099.

Bauer S, Rasika S, Han J, Mauduit C, Raccurt M, Morel G, Jourdan F, Benahmed M, Moyse E, Patterson PH. 2003. Leukemia inhibitory factor is a key signal for injury-induced neurogenesis in the adult mouse olfac-tory epithelium. J Neurosci 23:1792-1803.

Bauer S, Kerr BJ, Patterson PH. 2007. The neuropoietic cytokine family in development, plasticity, disease and injury. Nat Rev Neurosci 8:221-232.

Beal MF, Ferrante RJ, Swartz KJ, Kowall NW. 1991. Chronic quinolinic acid lesions in rats closely resemble Huntington’s disease. J Neurosci 11:1649-1659.

Belluardo N, Mudo G, Bonomo A, Di Liberto V, Frinchi M, Fuxe K. 2008. Nicotine-induced fi broblast growth factor-2 restores the age-related de-cline of precursor cell proliferation in the subventricular zone of rat brain. Brain Res 1193:12-24.

Ben-Hur T, Einstein O, Mizrachi-Kol R, Ben-Menachem O, Reinhartz E, Karussis D, Abramsky O. 2003. Transplanted multipotential neural pre-cursor cells migrate into the infl amed white matter in response to exper-imental autoimmune encephalomyelitis. Glia 41:73-80.

Benedetti S, Bruzzone MG, Pollo B, DiMeco F, Magrassi L, Pirola B, Cirenei N, Colombo MP, Finocchiaro G. 1999. Eradication of rat malig-nant gliomas by retroviral-mediated, in vivo delivery of the interleukin 4 gene. Cancer Res 59:645-652.

Bjugstad KB, Redmond DE Jr, Teng YD, Elsworth JD, Roth RH, Blanchard BC, Snyder EY, Sladek JR Jr. 2005. Neural stem cells implanted into MPTP-treated monkeys increase the size of endogenous tyrosine hydroxylase-positive cells found in the striatum: A return to control measures. Cell Transpl 14:183-192.

Bjugstad KB, Teng YD, Redmond DE Jr, Elsworth JD, Roth RH, Cornelius SK, Snyder EY, Sladek JR Jr. 2008. Human neural stem cells migrate along the nigrostriatal pathway in a primate model of Parkinson’s dis-ease. Exp Neurol 211:362-369.

Bolteus AJ, Bordey A. 2004. GABA release and uptake regulate neuronal precursor migration in the postnatal subventricular zone. J Neurosci 24:7623-7631.

Bonaguidi MA, McGuire T, Hu M, Kan L, Samanta J, Kessler JA. 2005. LIF and BMP signaling generate separate and discrete types of GFAP-expressing cells. Development 132:5503-5514.

Cacci E, Salani M, Anastasi S, Perroteau I, Poiana G, Biagioni S, Augusti-Tocco G. 2003. Hepatocyte growth factor stimulates cell motility in cul-tures of the striatal progenitor cells st14a. J Neurosci Res 74:760-768.

Cai J, Cheng A, Luo Y, Lu C, Mattson MP, Rao MS, Furukawa K. 2004. Membrane properties of rat embryonic multipotent neural stem cells. J Neurochem 88:212-226.

Calderon TM, Eugenin EA, Lopez L, Kumar SS, Hesselgesser J, Raine CS, Berman JW. 2006. A role for CXCL12 (SDF-1alpha) in the pathogenesis of multiple sclerosis: Regulation of CXCL12 expres-sion in astrocytes by soluble myelin basic protein. J Neuroimmunol 177:27-39.

Capela A, Temple S. 2002. Lex/ssea-1 is expressed by adult mouse CNS stem cells, identifying them as nonependymal. Neuron 35:865-875.

Capela A, Temple S. 2006. Lex is expressed by principal progenitor cells in the embryonic nervous system, is secreted into their environment and binds wnt-1. Dev Biol 291:300-313.

Carpenter MK, Cui X, Hu ZY, Jackson J, Sherman S, Seiger A, Wahlberg LU. 1999. In vitro expansion of a multipotent population of human neu-ral progenitor cells. Exp Neurol 158:265-278.

Chaichana K, Zamora-Berridi G, Camara-Quintana J, Quiñones-Hinojosa A. 2006. Neurosphere assays: Growth factors and hormone differences in tumor and nontumor studies. Stem Cells 24:2851-2857.

Chaichana K, Guerrero-Cazares H, Capilla-Gonzalez V, Zamora-Berridi G, Achanta P, Gonzalez-Perez O, Jallo G, Garcia-Verdugo JM, Quiñones-Hinojosa A. 2009. Intra-operatively obtained human tissue: Protocols and techniques for the study of neural stem cells. J Neurosci Meth 180:116-125.

Chambers SM, Fasano CA, Papapetrou EP, Tomishima M, Sadelain M, Studer L. 2009. Highly effi cient neural conversion of human ES and IPS cells by dual inhibition of SMAD signaling. Nat Biotechnol 27:275-280.

Chen J, Magavi SS, Macklis JD. 2004. Neurogenesis of corticospinal motor neurons extending spinal projections in adult mice. Proc Natl Acad Sci U S A 101:16357-16362.

Chu K, Park KI, Lee ST, Jung KH, Ko SY, Kang L, Sinn DI, Lee YS, Kim SU, Kim M, Roh JK. 2005. Combined treatment of vascular endothelial growth factor and human neural stem cells in experimental focal cere-bral ischemia. Neurosci Res 53:384-390.

Ciccolini F, Mandl C, Holzl-Wenig G, Kehlenbach A, Hellwig A. 2005. Prospective isolation of late development multipotent precursors whose migration is promoted by EGFR. Dev Biol 284:112-125.

Corti S, Locatelli F, Papadimitriou D, Donadoni C, Del Bo R, Fortunato F, Strazzer S, Salani S, Bresolin N, Comi GP. 2005. Multipotentiality, homing properties, and pyramidal neurogenesis of CNS-derived lex(ssea-1)+/cxcr4+ stem cells. FASEB J 19:1860-1862.

Corti S, Locatelli F, Papadimitriou D, Donadoni C, Salani S, Del Bo R, Strazzer S, Bresolin N, Comi GP. 2006. Identifi cation of a primitive brain-derived neural stem cell population based on aldehyde dehydroge-nase activity. Stem Cells 24:975-985.

Corti S, Locatelli F, Papadimitriou D, Del Bo R, Nizzardo M, Nardini M, Donadoni C, Salani S, Fortunato F, Strazzer S, Bresolin N, Comi GP. 2007a. Neural stem cells lewisx+ cxcr4+ modify disease progression in an amyotrophic lateral sclerosis model. Brain 130:1289-1305.

Corti S, Nizzardo M, Nardini M, Donadoni C, Locatelli F, Papadimitriou D, Salani S, Del Bo R, Ghezzi S, Strazzer S, Bresolin N, Comi GP. 2007b. Isolation and characterization of murine neural stem/progenitor cells based on prominin-1 expression. Exp Neurol 205:547-562.

Cross MJ, Dixelius J, Matsumoto T, Claesson-Welsh L. 2003. VEGF-receptor signal transduction. Trends Biochem Sci 28:488-494.

Curtis MA, Kam M, Nannmark U, Anderson MF, Axell MZ, Wikkelso C, Holtas S, van Roon-Mom WM, Bjork-Eriksson T, Nordborg C, Frisen J, Dragunow M, Faull RL, Eriksson PS. 2007. Human neuroblasts migrate to the olfactory bulb via a lateral ventricular extension. Science 315:1243-1249.

Darsalia V, Heldmann U, Lindvall O, Kokaia Z. 2005. Stroke-induced neu-rogenesis in aged brain. Stroke 36:1790-1795.

Darsalia V, Kallur T, Kokaia Z. 2007. Survival, migration and neuronal dif-ferentiation of human fetal striatal and cortical neural stem cells grafted in stroke-damaged rat striatum. Eur J Neurosci 26:605-614.

Deisseroth K, Singla S, Toda H, Monje M, Palmer TD, Malenka RC. 2004. Excitation-neurogenesis coupling in adult neural stem/progenitor cells. Neuron 42:535-552.

Doetsch F. 2003. A niche for adult neural stem cells. Curr Opin Genet Dev 13:543-550.

Doetsch F, Alvarez-Buylla A. 1996. Network of tangential pathways for neuronal migration in adult mammalian brain. Proc Natl Acad Sci U S A 93:14895-14900.

Doetsch F, Garcia-Verdugo JM, Alvarez-Buylla A. 1997. Cellular composi-tion and three-dimensional organization of the subventricular germinal zone in the adult mammalian brain. J Neurosci 17:5046-5061.

Doetsch F, Caille I, Lim DA, Garcia-Verdugo JM, Alvarez-Buylla A. 1999a. Subventricular zone astrocytes are neural stem cells in the adult mam-malian brain. Cell 97:703-716.

Doetsch F, Garcia-Verdugo JM, Alvarez-Buylla A. 1999b. Regeneration of a germinal layer in the adult mammalian brain. Proc Natl Acad Sci U S A 96:11619-11624.

Doetsch F, Petreanu L, Caille I, Garcia-Verdugo JM, Alvarez-Buylla A. 2002. EGF converts transit-amplifying neurogenic precursors in the adult brain into multipotent stem cells. Neuron 36:1021-1034.

Ebert AD, Beres AJ, Barber AE, Svendsen CN. 2008. Human neural progenitor cells over-expressing IGF-1 protect dopamine neurons and



restore function in a rat model of Parkinson’s disease. Exp Neurol 209:213-223.

Ehtesham M, Kabos P, Kabosova A, Neuman T, Black KL, Yu JS. 2002. The use of interleukin 12-secreting neural stem cells for the treatment of intracranial glioma. Cancer Res 62:5657-5663.

Einstein O, Karussis D, Grigoriadis N, Mizrachi-Kol R, Reinhartz E, Abramsky O, Ben-Hur T. 2003. Intraventricular transplantation of neu-ral precursor cell spheres attenuates acute experimental allergic enceph-alomyelitis. Mol Cell Neurosci 24:1074-1082.

Ekdahl CT, Kokaia Z, Lindvall O. 2009. Brain infl ammation and adult neu-rogenesis: The dual role of microglia. Neuroscience 158:1021-1029.

Emborg ME, Ebert AD, Moirano J, Peng S, Suzuki M, Capowski E, Joers V, Roitberg BZ, Aebischer P, Svendsen CN. 2008. GDNF-secreting human neural progenitor cells increase tyrosine hydroxylase and VMAT2 expres-sion in MPTP-treated cynomolgus monkeys. Cell Transpl 17:383-395.

Enzmann GU, Benton RL, Talbott JF, Cao Q, Whittemore SR. 2006. Func-tional considerations of stem cell transplantation therapy for spinal cord repair. J Neurotrauma 23:479-495.

Erceg S, Ronaghi M, Stojkovic M. 2008. Human embryonic stem cell dif-ferentiation toward regional specifi c neural precursors. Stem Cells 27:78-87.

Feldmann RE Jr, Mattern R. 2006. The human brain and its neural stem cells postmortem: From dead brains to live therapy. Int J Legal Med 120:201-211.

Forsberg-Nilsson K, Behar TN, Afrakhte M, Barker JL, McKay RD. 1998. Platelet-derived growth factor induces chemotaxis of neuroepithelial stem cells. J Neurosci Res 53:521-530.

Fromont A, De Seze J, Fleury MC, Maillefert JF, Moreau T. 2009. Infl am-matory demyelinating events following treatment with anti-tumor ne-crosis factor. Cytokine 45:55-57.

Fu L, Zhu L, Huang Y, Lee TD, Forman SJ, Shih CC. 2008. Derivation of neural stem cells from mesenchymal stem cells: Evidence for a bipoten-tial stem cell population. Stem Cells Dev 17:1109-1121.

Gage FH, Kempermann G, Palmer TD, Peterson DA, Ray J. 1998. Multipo-tent progenitor cells in the adult dentate gyrus. J Neurobiol 36:249-266.

Galli R, Pagano SF, Gritti A, Vescovi AL. 2000. Regulation of neuronal dif-ferentiation in human CNS stem cell progeny by leukemia inhibitory factor. Dev Neurosci 22:86-95.

Garcion E, Faissner A, ffrench-Constant C. 2001. Knockout mice reveal a contribution of the extracellular matrix molecule tenascin-c to neural precursor proliferation and migration. Development 128:2485-2496.

Garcion E, Halilagic A, Faissner A, ffrench-Constant C. 2004. Generation of an environmental niche for neural stem cell development by the ex-tracellular matrix molecule tenascin c. Development 131:3423-3432.

Garzotto D, Giacobini P, Crepaldi T, Fasolo A, De Marchis S. 2008. Hepa-tocyte growth factor regulates migration of olfactory interneuron pre-cursors in the rostral migratory stream through met-grb2 coupling. J Neurosci 28:5901-5909.

Gates MA, Thomas LB, Howard EM, Laywell ED, Sajin B, Faissner A, Gotz B, Silver J, Steindler DA. 1995. Cell and molecular analysis of the developing and adult mouse subventricular zone of the cerebral hemi-spheres. J Comp Neurol 361:249-266.

Ge S, Sailor KA, Ming GL, Song H. 2008. Synaptic integration and plastic-ity of new neurons in the adult hippocampus. J Physiol 586:3759-3765.

Glass R, Synowitz M, Kronenberg G, Walzlein JH, Markovic DS, Wang LP, Gast D, Kiwit J, Kempermann G, Kettenmann H. 2005. Glioblastoma-induced attraction of endogenous neural precursor cells is associated with improved survival. J Neurosci 25:2637-2646.

Goldman SA, Nottebohm F. 1983. Neuronal production, migration, and dif-ferentiation in a vocal control nucleus of the adult female canary brain. Proc Natl Acad Sci U S A 80:2390-2394.

Gould E, Reeves AJ, Graziano MS, Gross CG. 1999. Neurogenesis in the neocortex of adult primates. Science 286:548-552.

Gritti A, Cova L, Parati EA, Galli R, Vescovi AL. 1995. Basic fi broblast growth factor supports the proliferation of epidermal growth factor-generated neuronal precursor cells of the adult mouse CNS. Neurosci Lett 185:151-154.

Gritti A, Parati EA, Cova L, Frolichsthal P, Galli R, Wanke E, Faravelli L, Morassutti DJ, Roisen F, Nickel DD, Vescovi AL. 1996. Multipotential stem cells from the adult mouse brain proliferate and self-renew in re-sponse to basic fi broblast growth factor. J Neurosci 16:1091-1100.

Gritti A, Frolichsthal-Schoeller P, Galli R, Parati EA, Cova L, Pagano SF, Bjornson CR, Vescovi AL. 1999. Epidermal and fi broblast growth fac-tors behave as mitogenic regulators for a single multipotent stem cell-like population from the subventricular region of the adult mouse forebrain. J Neurosci 19:3287-3297.

Guan Y, Jiang Z, Ciric B, Rostami AM, Zhang GX. 2008. Upregulation of chemokine receptor expression by il-10/il-4 in adult neural stem cells. Exp Mol Pathol 85:232-236.

Gupta A, Dawson VL, Dawson TM. 2008. What causes cell death in Parkinson’s disease? Ann Neurol 64 Suppl 2:S3-S15.

Gurney ME, Pu H, Chiu AY, Dal Canto MC, Polchow CY, Alexander DD, Caliendo J, Hentati A, Kwon YW, Deng HX, Chen W, Zhai P, Sufi t RL, Sidiique T. 1994. Motor neuron degeneration in mice that express a hu-man cu, zn superoxide dismutase mutation. Science 264:1772-1775.

Gutova M, Najbauer J, Frank RT, Kendall SE, Gevorgyan A, Metz MZ, Guevorkian M, Edmiston M, Zhao D, Glackin CA, Kim SU, Aboody KS. 2008. Urokinase plasminogen activator and urokinase plasminogen activator receptor mediate human stem cell tropism to malignant solid tumors. Stem Cells 26:1406-1413.

Guzman R, De Los Angeles A, Cheshier S, Choi R, Hoang S, Liauw J, Schaar B, Steinberg G. 2008. Intracarotid injection of fl uorescence acti-vated cell-sorted cd49d-positive neural stem cells improves targeted cell delivery and behavior after stroke in a mouse stroke model. Stroke 39:1300-1306.

Haddad MS, Cummings JL. 1997. Huntington’s disease. Psychiatr Clin North Am 20:791-807.

Hall PE, Lathia JD, Caldwell MA, ffrench-Constant C. 2008. Laminin en-hances the growth of human neural stem cells in defi ned culture media. BMC Neurosci 9:71.

Hayashi T, Abe K, Suzuki H, Itoyama Y. 1997. Rapid induction of vascular endothelial growth factor gene expression after transient middle cere-bral artery occlusion in rats. Stroke 28:2039-2044.

Herrera DG, Garcia-Verdugo JM, Alvarez-Buylla A. 1999. Adult-derived neural precursors transplanted into multiple regions in the adult brain. Ann Neurol 46:867-877.

Herrlinger U, Woiciechowski C, Sena-Esteves M, Aboody KS, Jacobs AH, Rainov NG, Snyder EY, Breakefi eld XO. 2000. Neural precursor cells for delivery of replication-conditional hsv-1 vectors to intracerebral gliomas. Mol Ther 1:347-357.

Hill WD, Hess DC, Martin-Studdard A, Carothers JJ, Zheng J, Hale D, Maeda M, Fagan SC, Carroll JE, Conway SJ. 2004. Sdf-1 (CXCL12) is upregulated in the ischemic penumbra following stroke: Association with bone marrow cell homing to injury. J Neuropathol Exp Neurol 63:84-96.

Honeth G, Stafl in K, Kalliomaki S, Lindvall M, Kjellman C. 2006. Chemokine-directed migration of tumor-inhibitory neural progenitor cells toward an intracranially growing glioma. Exp Cell Res 312:1265-1276.

Hou SW, Wang YQ, Xu M, Shen DH, Wang JJ, Huang F, Yu Z, Sun FY. 2008. Functional integration of newly generated neurons into striatum after cerebral ischemia in the adult rat brain. Stroke 39:2837-2844.

Hovakimyan M, Haas SJ, Schmitt O, Gerber B, Wree A, Andressen C. 2008. Mesencephalic human neural progenitor cells transplanted into the adult hemiparkinsonian rat striatum lack dopaminergic differentia-tion but improve motor behavior. Cells Tissues Organs 188:373-383.

Hynes RO. 2002. Integrins: Bidirectional, allosteric signaling machines. Cell 110:673-687.

Ihrie RA, Alvarez-Buylla A. 2008. Cells in the astroglial lineage are neural stem cells. Cell Tissue Res 331:179-191.

Iihara K, Sasahara M, Hashimoto N, Uemura Y, Kikuchi H, Hazama F. 1994. Ischemia induces the expression of the platelet-derived growth factor-b chain in neurons and brain macrophages in vivo. J Cereb Blood Flow Metab 14:818-824.


20 ILAR Journal

Imitola J, Raddassi K, Park KI, Mueller FJ, Nieto M, Teng YD, Frenkel D, Li J, Sidman RL, Walsh CA, Snyder EY, Khoury SJ. 2004. Directed migration of neural stem cells to sites of CNS injury by the stromal cell-derived factor 1alpha/cxc chemokine receptor 4 pathway. Proc Natl Acad Sci U S A 101:18117-18122.

Imura T, Nakano I, Kornblum HI, Sofroniew MV. 2006. Phenotypic and functional heterogeneity of GFAP-expressing cells in vitro: Differential expression of lex/cd15 by GFAP-expressing multipotent neural stem cells and non-neurogenic astrocytes. Glia 53:277-293.

Isacson O, Brundin P, Gage FH, Bjorklund A. 1985. Neural grafting in a rat model of Huntington’s disease: Progressive neurochemical changes af-ter neostriatal ibotenate lesions and striatal tissue grafting. Neuroscience 16:799-817.

Itoh T, Satou T, Ishida H, Nishida S, Tsubaki M, Hashimoto S, Ito H. 2009. The relationship between SDF-1alpha/cxcr4 and neural stem cells ap-pearing in damaged area after traumatic brain injury in rats. Neurol Res 31:90-102.

Jackson EL, Garcia-Verdugo JM, Gil-Perotin S, Roy M, Quiñones-Hinojosa A, VandenBerg S, Alvarez-Buylla A. 2006. PDGFr alpha-positive B cells are neural stem cells in the adult SVZ that form glioma-like growths in response to increased PDGF signaling. Neuron 51:187-199.

Jacques TS, Relvas JB, Nishimura S, Pytela R, Edwards GM, Streuli CH, ffrench-Constant C. 1998. Neural precursor cell chain migration and division are regulated through different beta1 integrins. Development 125:3167-3177.

Jenner P, Marsden CD. 1986. The actions of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in animals as a model of Parkinson’s disease. J Neu-ral Transm Suppl 20:11-39.

Jiang YM, Yamamoto M, Kobayashi Y, Yoshihara T, Liang Y, Terao S, Takeuchi H, Ishigaki S, Katsuno M, Adachi H, Niwa J, Tanaka F, Doyu M, Yoshida M, Hashizume Y, Sobue G. 2005. Gene expression profi le of spinal motor neurons in sporadic amyotrophic lateral sclerosis. Ann Neurol 57:236-251.

Jin K, Minami M, Lan JQ, Mao XO, Batteur S, Simon RP, Greenberg DA. 2001. Neurogenesis in dentate subgranular zone and rostral subventric-ular zone after focal cerebral ischemia in the rat. Proc Natl Acad Sci U S A 98:4710-4715.

Jin K, Zhu Y, Sun Y, Mao XO, Xie L, Greenberg DA. 2002. Vascular endo-thelial growth factor (VEGF) stimulates neurogenesis in vitro and in vivo. Proc Natl Acad Sci U S A 99:11946-11950.

Jin K, Sun Y, Xie L, Mao XO, Childs J, Peel A, Logvinova A, Banwait S, Greenberg DA. 2005. Comparison of ischemia-directed migration of neural precursor cells after intrastriatal, intraventricular, or intravenous transplantation in the rat. Neurobiol Dis 18:366-374.

Joannides A, Gaughwin P, Schwiening C, Majed H, Sterling J, Compston A, Chandran S. 2004. Effi cient generation of neural precursors from adult human skin: Astrocytes promote neurogenesis from skin-derived stem cells. Lancet 364:172-178.

Kendall SE, Najbauer J, Johnston HF, Metz MZ, Li S, Bowers M, Garcia E, Kim SU, Barish ME, Aboody KS, Glackin CA. 2008. Neural stem cell targeting of glioma is dependent on phosphoinositide 3-kinase signal-ing. Stem Cells 26:1575-1586.

Kerosuo L, Piltti K, Fox H, Angers-Loustau A, Hayry V, Eilers M, Sariola H, Wartiovaara K. 2008. Myc increases self-renewal in neural progeni-tor cells through miz-1. J Cell Sci 121:3941-3950.

Keyoung HM, Goldman SA. 2007. Glial progenitor-based repair of demy-elinating neurological diseases. Neurosurg Clin N Am 18:93-104, x.

Kim M, Morshead CM. 2003. Distinct populations of forebrain neural stem and progenitor cells can be isolated using side-population analysis. J Neurosci 23:10703-10709.

Kim M, Lee ST, Chu K, Kim SU. 2008. Stem cell-based cell therapy for Huntington disease: A review. Neuropathology 28:1-9.

Kim SU. 2007. Genetically engineered human neural stem cells for brain repair in neurological diseases. Brain Dev 29:193-201.

Klein SM, Behrstock S, McHugh J, Hoffmann K, Wallace K, Suzuki M, Aebischer P, Svendsen CN. 2005. GDNF delivery using human neu-ral progenitor cells in a rat model of ALS. Hum Gene Ther 16:509-521.

Koehler NK, Roebbert M, Dehghani K, Ballmaier M, Claus P, von Hoersten S, Shing M, Odin P, Strehlau J, Heidenreich F. 2008. Up-regulation of platelet-derived growth factor by peripheral-blood leukocytes during experimental allergic encephalomyelitis. J Neurosci Res 86:392-402.

Kornack DR, Rakic P. 2001. Cell proliferation without neurogenesis in adult primate neocortex. Science 294:2127-2130.

Kuge A, Takemura S, Kokubo Y, Sato S, Goto K, Kayama T. 2009. Temporal profi le of neurogenesis in the subventricular zone, dentate gyrus and cerebral cortex following transient focal cerebral ischemia. Neurol Res [Epub ahead of print; doi: 10.1179/174313209X383312].

Kuhn HG, Winkler J, Kempermann G, Thal LJ, Gage FH. 1997. Epidermal growth factor and fi broblast growth factor-2 have different effects on neural progenitors in the adult rat brain. J Neurosci 17:5820-5829.

Laguna Goya R, Tyers P, Barker RA. 2008. The search for a curative cell therapy in Parkinson’s disease. J Neurol Sci 265:32-42.

Lambrechts D, Carmeliet P. 2006. VEGF at the neurovascular interface: Therapeutic implications for motor neuron disease. Biochim Biophys Acta 1762:1109-1121.

Lan F, Xu J, Zhang X, Wong VW, Li X, Lu A, Lu W, Shen L, Li L. 2008. Hepatocyte growth factor promotes proliferation and migration in immortalized progenitor cells. Neuroreport 19:765-769.

Laywell ED, Steindler DA, Silver DJ. 2007. Astrocytic stem cells in the adult brain. Neurosurg Clin N Am 18:21-30, viii.

Lee A, Kessler JD, Read TA, Kaiser C, Corbeil D, Huttner WB, Johnson JE, Wechsler-Reya RJ. 2005a. Isolation of neural stem cells from the post-natal cerebellum. Nat Neurosci 8:723-729.

Lee HJ, Kim KS, Park IH, Kim SU. 2007. Human neural stem cells over-expressing VEGF provide neuroprotection, angiogenesis and functional recovery in mouse stroke model. PLoS One 2:e156.

Lee ST, Chu K, Park JE, Lee K, Kang L, Kim SU, Kim M. 2005b. Intravenous administration of human neural stem cells induces func-tional recovery in Huntington’s disease rat model. Neurosci Res 52:243-249.

Legate KR, Wickstrom SA, Fassler R. 2009. Genetic and cell biological analysis of integrin outside-in signaling. Genes Dev 23:397-418.

Lendahl U, Zimmerman LB, McKay RD. 1990. CNS stem cells express a new class of intermediate fi lament protein. Cell 60:585-595.

Leventhal C, Rafi i S, Rafi i D, Shahar A, Goldman SA. 1999. Endothelial trophic support of neuronal production and recruitment from the adult mammalian subependyma. Mol Cell Neurosci 13:450-464.

Li JY, Popovic N, Brundin P. 2005. The use of the r6 transgenic mouse models of Huntington’s disease in attempts to develop novel therapeutic strategies. NeuroRx 2:447-464.

Li S, Gao Y, Tokuyama T, Yamamoto J, Yokota N, Yamamoto S, Terakawa S, Kitagawa M, Namba H. 2007. Genetically engineered neural stem cells migrate and suppress glioma cell growth at distant intracranial sites. Cancer Lett 251:220-227.

Li W, LoTurco JJ. 2000. Noggin is a negative regulator of neuronal differ-entiation in developing neocortex. Dev Neurosci 22:68-73.

Lim DA, Tramontin AD, Trevejo JM, Herrera DG, Garcia-Verdugo JM, Alvarez-Buylla A. 2000. Noggin antagonizes BMP signaling to create a niche for adult neurogenesis. Neuron 28:713-726.

Lim DA, Cha S, Mayo MC, Chen MH, Keles E, VandenBerg S, Berger MS. 2007. Relationship of glioblastoma multiforme to neural stem cell re-gions predicts invasive and multifocal tumor phenotype. Neuro Oncol 9:424-429.

Liu X, Wang Q, Haydar TF, Bordey A. 2005. Nonsynaptic GABA signaling in postnatal subventricular zone controls proliferation of GFAP-expressing progenitors. Nat Neurosci 8:1179-1187.

Liu XS, Chopp M, Santra M, Hozeska-Solgot A, Zhang RL, Wang L, Teng H, Lu M, Zhang ZG. 2008. Functional response to SDF1 alpha through over-expression of CXCR4 on adult subventricular zone progenitor cells. Brain Res 1226:18-26.

Liu YP, Lang BT, Baskaya MK, Dempsey RJ, Vemuganti R. 2009. The potential of neural stem cells to repair stroke-induced brain damage. Acta Neuropathol 117:469-480.

Lledo PM, Merkle FT, Alvarez-Buylla A. 2008. Origin and function of olfactory bulb interneuron diversity. Trends Neurosci 31:392-400.



Lois C, Alvarez-Buylla A. 1994. Long-distance neuronal migration in the adult mammalian brain. Science 264:1145-1148.

Lois C, Garcia-Verdugo JM, Alvarez-Buylla A. 1996. Chain migration of neuronal precursors. Science 271:978-981.

Ludwin SK, Kosek JC, Eng LF. 1976. The topographical distribution of s-100 and gfa proteins in the adult rat brain: An immunohistochemical study using horseradish peroxidase-labelled antibodies. J Comp Neurol 165:197-207.

Lundberg C, Englund U, Trono D, Bjorklund A, Wictorin K. 2002. Differ-entiation of the rn33b cell line into forebrain projection neurons after transplantation into the neonatal rat brain. Exp Neurol 175:370-387.

Magavi SS, Leavitt BR, Macklis JD. 2000. Induction of neurogenesis in the neocortex of adult mice. Nature 405:951-955.

Marshall GP 2nd, Reynolds BA, Laywell ED. 2007. Using the neurosphere assay to quantify neural stem cells in vivo. Curr Pharm Biotechnol 8:141-145.

McBride JL, Behrstock SP, Chen EY, Jakel RJ, Siegel I, Svendsen CN, Kordower JH. 2004. Human neural stem cell transplants improve motor function in a rat model of Huntington’s disease. J Comp Neurol 475:211-219.

McCandless EE, Piccio L, Woerner BM, Schmidt RE, Rubin JB, Cross AH, Klein RS. 2008. Pathological expression of CXCL12 at the blood-brain barrier correlates with severity of multiple sclerosis. Am J Pathol 172:799-808.

McCoy MK, Tansey MG. 2008. Tnf signaling inhibition in the CNS: Impli-cations for normal brain function and neurodegenerative disease. J Neu-roinfl ammation 5:45.

Menn B, Garcia-Verdugo JM, Yaschine C, Gonzalez-Perez O, Rowitch D, Alvarez-Buylla A. 2006. Origin of oligodendrocytes in the subventricu-lar zone of the adult brain. J Neurosci 26:7907-7918.

Mercier F, Kitasako JT, Hatton GI. 2002. Anatomy of the brain neurogenic zones revisited: Fractones and the fi broblast/macrophage network. J Comp Neurol 451:170-188.

Miller JT, Bartley JH, Wimborne HJ, Walker AL, Hess DC, Hill WD, Carroll JE. 2005. The neuroblast and angioblast chemotaxic factor SDF-1 (CXCL12) expression is briefl y up regulated by reactive astrocytes in brain following neonatal hypoxic-ischemic injury. BMC Neurosci 6:63.

Ming GL, Song H. 2005. Adult neurogenesis in the mammalian central ner-vous system. Annu Rev Neurosci 28:223-250.

Mirzadeh Z, Merkle FT, Soriano-Navarro M, Garcia-Verdugo JM, Alvarez-Buylla A. 2008. Neural stem cells confer unique pinwheel architecture to the ventricular surface in neurogenic regions of the adult brain. Cell Stem Cell 3:265-278.

Mix E, Meyer-Rienecker H, Zettl UK. 2008. Animal models of multiple sclerosis for the development and validation of novel therapies: Poten-tial and limitations. J Neurol 255 Suppl 6:7-14.

Mokry J. 1995. Experimental models and behavioural tests used in the study of Parkinson’s disease. Physiol Res 44:143-150.

Moore KA, Lemischka IR. 2006. Stem cells and their niches. Science 311:1880-1885.

Morita E, Watanabe Y, Ishimoto M, Nakano T, Kitayama M, Yasui K, Fukada Y, Doi K, Karunaratne A, Murrell WG, Sutharsan R, Mackay-Sim A, Hata Y, Nakashima K. 2008. A novel cell transplantation protocol and its application to an ALS mouse model. Exp Neurol 213:431-438.

Mudo G, Belluardo N, Mauro A, Fuxe K. 2007. Acute intermittent nicotine treatment induces fi broblast growth factor-2 in the subventricular zone of the adult rat brain and enhances neuronal precursor cell proliferation. Neuroscience 145:470-483.

Mudo G, Bonomo A, Di Liberto V, Frinchi M, Fuxe K, Belluardo N. 2009. The fgf-2/fgfrs neurotrophic system promotes neurogenesis in the adult brain. J Neural Transm 116:995-1005.

Mueller FJ, Serobyan N, Schraufstatter IU, DiScipio R, Wakeman D, Loring JF, Snyder EY, Khaldoyanidi SK. 2006. Adhesive interactions between human neural stem cells and infl amed human vascular en-dothelium are mediated by integrins. Stem Cells 24:2367-2372.

Mukhida K, Baghbaderani BA, Hong M, Lewington M, Phillips T, McLeod M, Sen A, Behie LA, Mendez I. 2008. Survival, differentiation, and

migration of bioreactor-expanded human neural precursor cells in a model of Parkinson disease in rats. Neurosurg Focus 24:E8.

Nagato M, Heike T, Kato T, Yamanaka Y, Yoshimoto M, Shimazaki T, Okano H, Nakahata T. 2005. Prospective characterization of neural stem cells by fl ow cytometry analysis using a combination of surface mark-ers. J Neurosci Res 80:456-466.

Nagayama T, Nagayama M, Kohara S, Kamiguchi H, Shibuya M, Katoh Y, Itoh J, Shinohara Y. 2004. Post-ischemic delayed expression of hepato-cyte growth factor and c-met in mouse brain following focal cerebral ischemia. Brain Res 999:155-166.

Nicoleau C, Benzakour O, Agasse F, Thiriet N, Petit J, Prestoz L, Roger M, Jaber M, Coronas V. 2008. Endogenous hepatocyte growth factor is a niche signal for subventricular zone neural stem cell amplifi cation and self-renewal. Stem Cells 27:408-419.

Nowakowski RS, Hayes NL. 2000. New neurons: Extraordinary evidence or extraordinary conclusion? Science 288:771.

O’Keeffe FE, Scott SA, Tyers P, O’Keeffe GW, Dalley JW, Zufferey R, Caldwell MA. 2008. Induction of a9 dopaminergic neurons from neural stem cells improves motor function in an animal model of Parkinson’s disease. Brain 131:630-641.

Obermair FJ, Schroter A, Thallmair M. 2008. Endogenous neural progeni-tor cells as therapeutic target after spinal cord injury. Physiology (Bethesda) 23:296-304.

Ohab JJ, Fleming S, Blesch A, Carmichael ST. 2006. A neurovascular niche for neurogenesis after stroke. J Neurosci 26:13007-13016.

Ohno M, Sasahara M, Narumiya S, Tanaka N, Yamano T, Shimada M, Hazama F. 1999. Expression of platelet-derived growth factor b-chain and beta-receptor in hypoxic/ischemic encephalopathy of neonatal rats. Neuroscience 90:643-651.

Ostenfeld T, Caldwell MA, Prowse KR, Linskens MH, Jauniaux E, Svendsen CN. 2000. Human neural precursor cells express low levels of telomerase in vitro and show diminishing cell proliferation with extensive axonal outgrowth following transplantation. Exp Neurol 164:215-226.

Ourednik J, Ourednik V, Lynch WP, Schachner M, Snyder EY. 2002. Neural stem cells display an inherent mechanism for rescuing dysfunctional neurons. Nat Biotechnol 20:1103-1110.

Pagano SF, Impagnatiello F, Girelli M, Cova L, Grioni E, Onofri M, Cavallaro M, Etteri S, Vitello F, Giombini S, Solero CL, Parati EA. 2000. Isolation and characterization of neural stem cells from the adult human olfactory bulb. Stem Cells 18:295-300.

Palmer TD, Ray J, Gage FH. 1995. Fgf-2-responsive neuronal progenitors reside in proliferative and quiescent regions of the adult rodent brain. Mol Cell Neurosci 6:474-486.

Parent JM, Vexler ZS, Gong C, Derugin N, Ferriero DM. 2002. Rat fore-brain neurogenesis and striatal neuron replacement after focal stroke. Ann Neurol 52:802-813.

Pastori C, Librizzi L, Breschi GL, Regondi C, Frassoni C, Panzica F, Frigerio S, Gelati M, Parati E, De Simoni MG, de Curtis M. 2008. Arte-rially perfused neurosphere-derived cells distribute outside the ischemic core in a model of transient focal ischemia and reperfusion in vitro. PLoS One 3:e2754.

Peh GS, Lang RJ, Pera MF, Hawes SM. 2009. CD133 expression by neural progenitors derived from human embryonic stem cells and its use for their prospective isolation. Stem Cells Dev 18:269-282.

Pencea V, Bingaman KD, Freedman LJ, Luskin MB. 2001. Neurogenesis in the subventricular zone and rostral migratory stream of the neonatal and adult primate forebrain. Exp Neurol 172:1-16.

Peretto P, Giachino C, Aimar P, Fasolo A, Bonfanti L. 2005. Chain formation and glial tube assembly in the shift from neonatal to adult subventricular zone of the rodent forebrain. J Comp Neurol 487:407-427.

Pineda JR, Rubio N, Akerud P, Urban N, Badimon L, Arenas E, Alberch J, Blanco J, Canals JM. 2007. Neuroprotection by GDNF-secreting stem cells in a Huntington’s disease model: Optical neuroimage tracking of brain-grafted cells. Gene Ther 14:118-128.


22 ILAR Journal

Platel JC, Dave KA, Bordey A. 2008. Control of neuroblast production and migration by converging GABA and glutamate signals in the postnatal forebrain. J Physiol 586:3739-3743.

Platel JC, Gordon V, Heintz T, Bordey A. 2009. GFAP-GFP neural progeni-tors are antigenically homogeneous and anchored in their enclosed mo-saic niche. Glia 57:66-78.

Pluchino S, Martino G. 2005. The therapeutic use of stem cells for myelin repair in autoimmune demyelinating disorders. J Neurol Sci 233:117-119.

Pluchino S, Quattrini A, Brambilla E, Gritti A, Salani G, Dina G, Galli R, Del Carro U, Amadio S, Bergami A, Furlan R, Comi G, Vescovi AL, Martino G. 2003. Injection of adult neurospheres induces recovery in a chronic model of multiple sclerosis. Nature 422:688-694.

Prestoz L, Relvas JB, Hopkins K, Patel S, Sowinski P, Price J, ffrench-Constant C. 2001. Association between integrin-dependent migration capacity of neural stem cells in vitro and anatomical repair following transplantation. Mol Cell Neurosci 18:473-484.

Pumiglia K, Temple S. 2006. PEDF: Bridging neurovascular interactions in the stem cell niche. Nat Neurosci 9:299-300.

Quiñones-Hinojosa A, Chaichana K. 2007. The human subventricular zone: A source of new cells and a potential source of brain tumors. Exp Neu-rol 205:313-324.

Quiñones-Hinojosa A, Sanai N, Soriano-Navarro M, Gonzalez-Perez O, Mirzadeh Z, Gil-Perotin S, Romero-Rodriguez R, Berger MS, Garcia-Verdugo JM, Alvarez-Buylla A. 2006. Cellular composition and cyto-architecture of the adult human subventricular zone: A niche of neural stem cells. J Comp Neurol 494:415-434.

Quiñones-Hinojosa A, Sanai N, Gonzalez-Perez O, Garcia-Verdugo JM. 2007. The human brain subventricular zone: Stem cells in this niche and its organization. Neurosurg Clin N Am 18:15-20, vii.

Ramirez-Castillejo C, Sanchez-Sanchez F, Andreu-Agullo C, Ferron SR, Aroca-Aguilar JD, Sanchez P, Mira H, Escribano J, Farinas I. 2006. Pigment epithelium-derived factor is a niche signal for neural stem cell renewal. Nat Neurosci 9:331-339.

Redmond DE Jr, Bjugstad KB, Teng YD, Ourednik V, Ourednik J, Wakeman DR, Parsons XH, Gonzalez R, Blanchard BC, Kim SU, Gu Z, Lipton SA, Markakis EA, Roth RH, Elsworth JD, Sladek JR Jr, Sidman RL, Snyder EY. 2007. Behavioral improvement in a primate Parkinson’s model is associated with multiple homeostatic effects of human neural stem cells. Proc Natl Acad Sci U S A 104:12175-12180.

Ren W, Guo Q, Yang Y, Chen F. 2006. BFGF and heparin but not laminin are necessary factors in the mediums that affect NSCs differentiation into cholinergic neurons. Neurol Res 28:87-90.

Reynolds BA, Weiss S. 1992. Generation of neurons and astrocytes from isolated cells of the adult mammalian central nervous system. Science 255:1707-1710.

Reynolds BA, Weiss S. 1996. Clonal and population analyses demonstrate that an EGF-responsive mammalian embryonic CNS precursor is a stem cell. Dev Biol 175:1-13.

Reynolds BA, Tetzlaff W, Weiss S. 1992. A multipotent EGF-responsive striatal embryonic progenitor cell produces neurons and astrocytes. J Neurosci 12:4565-4574.

Riquelme PA, Drapeau E, Doetsch F. 2008. Brain micro-ecologies: Neural stem cell niches in the adult mammalian brain. Philos Trans R Soc Lond B Biol Sci 363:123-137.

Robin AM, Zhang ZG, Wang L, Zhang RL, Katakowski M, Zhang L, Wang Y, Zhang C, Chopp M. 2006. Stromal cell-derived factor 1alpha medi-ates neural progenitor cell motility after focal cerebral ischemia. J Cereb Blood Flow Metab 26:125-134.

Rosen DR, Siddique T, Patterson D, Figlewicz DA, Sapp P, Hentati A, Don-aldson D, Goto J, O’Regan JP, Deng HX, Rahmani Z, Krizus A, McK-enna-Yasek D, Cayabyab A, Gaston SM, Berger R, Tanzi RE, Halperin JJ, Herzfeldt B, Van den Bergh R, Hung W, Bird T, Deng G, Mulder DW, Smyth C, Laing NG, Soriano E, Pericak-Vance MA, Haines J, Rouleau GA, Gusella JS, Horvitz HR, Brown RH. 1993. Mutations in cu/zn superoxide dismutase gene are associated with familial amyo-trophic lateral sclerosis. Nature 362:59-62.

Roy NS, Nakano T, Keyoung HM, Windrem M, Rashbaum WK, Alonso ML, Kang J, Peng W, Carpenter MK, Lin J, Nedergaard M, Goldman SA.

2004. Telomerase immortalization of neuronally restricted progenitor cells derived from the human fetal spinal cord. Nat Biotechnol 22:297-305.

Roy NS, Chandler-Militello D, Lu G, Wang S, Goldman SA. 2007. Retrovi-rally mediated telomerase immortalization of neural progenitor cells. Nat Protoc 2:2815-2825.

Sanai N, Tramontin AD, Quiñones-Hinojosa A, Barbaro NM, Gupta N, Kunwar S, Lawton MT, McDermott MW, Parsa AT, Manuel-Garcia Verdugo J, Berger MS, Alvarez-Buylla A. 2004. Unique astrocyte rib-bon in adult human brain contains neural stem cells but lacks chain mi-gration. Nature 427:740-744.

Sanai N, Berger MS, Garcia-Verdugo JM, Alvarez-Buylla A. 2007. Com-ment on “Human neuroblasts migrate to the olfactory bulb via a lateral ventricular extension”. Science 318:393; author reply 393.

Sawamoto K, Nakao N, Kakishita K, Ogawa Y, Toyama Y, Yamamoto A, Yamaguchi M, Mori K, Goldman SA, Itakura T, Okano H. 2001. Gener-ation of dopaminergic neurons in the adult brain from mesencephalic precursor cells labeled with a nestin-GFP transgene. J Neurosci 21:3895-3903.

Schmidt NO, Koeder D, Messing M, Mueller FJ, Aboody KS, Kim SU, Black PM, Carroll RS, Westphal M, Lamszus K. 2009. Vascular endo-thelial growth factor-stimulated cerebral microvascular endothelial cells mediate the recruitment of neural stem cells to the neurovascular niche. Brain Res 1268:24-37.

Shen Q, Wang Y, Kokovay E, Lin G, Chuang SM, Goderie SK, Roysam B, Temple S. 2008. Adult SVZ stem cells lie in a vascular niche: A quantita-tive analysis of niche cell-cell interactions. Cell Stem Cell 3:289-300.

Shimato S, Natsume A, Takeuchi H, Wakabayashi T, Fujii M, Ito M, Ito S, Park IH, Bang JH, Kim SU, Yoshida J. 2007. Human neural stem cells target and deliver therapeutic gene to experimental leptomeningeal me-dulloblastoma. Gene Ther 14:1132-1142.

Shingo T, Sorokan ST, Shimazaki T, Weiss S. 2001. Erythropoietin regu-lates the in vitro and in vivo production of neuronal progenitors by mammalian forebrain neural stem cells. J Neurosci 21:9733-9743.

Shiras A, Chettiar ST, Shepal V, Rajendran G, Prasad GR, Shastry P. 2007. Spontaneous transformation of human adult nontumorigenic stem cells to cancer stem cells is driven by genomic instability in a human model of glioblastoma. Stem Cells 25:1478-1489.

Shyu WC, Lin SZ, Yen PS, Su CY, Chen DC, Wang HJ, Li H. 2008. Stromal cell-derived factor-1 alpha promotes neuroprotection, angiogenesis, and mobilization/homing of bone marrow-derived cells in stroke rats. J Pharmacol Exp Ther 324:834-849.

Siebzehnrubl FA, Jeske I, Muller D, Buslei R, Coras R, Hahnen E, Huttner HB, Corbeil D, Kaesbauer J, Appl T, von Horsten S, Blumcke I. 2008. Spontaneous in vitro transformation of adult neural precursors into stem-like cancer cells. Brain Pathol 19:399-408.

Sjoborg M, Pietz K, Ahgren A, Yamada N, Lindvall O, Funa K, Odin P. 1998. Expression of platelet-derived growth factor after intrastriatal ibotenic acid injury. Exp Brain Res 119:245-250.

Slevin M, Krupinski J, Mitsios N, Perikleous C, Cuadrado E, Montaner J, Sanfeliu C, Luque A, Kumar S, Kumar P, Gaffney J. 2008. Leukaemia inhibitory factor is over-expressed by ischaemic brain tissue concomi-tant with reduced plasma expression following acute stroke. Eur J Neurol 15:29-37.

Snethen H, Love S, Scolding N. 2008. Disease-responsive neural precursor cells are present in multiple sclerosis lesions. Regen Med 3:835-847.

Snyder EY, Deitcher DL, Walsh C, Arnold-Aldea S, Hartwieg EA, Cepko CL. 1992. Multipotent neural cell lines can engraft and participate in development of mouse cerebellum. Cell 68:33-51.

Studer L, Tabar V, McKay RD. 1998. Transplantation of expanded mesen-cephalic precursors leads to recovery in parkinsonian rats. Nat Neurosci 1:290-295.

Sun Y, Jin K, Xie L, Childs J, Mao XO, Logvinova A, Greenberg DA. 2003. VEGF-induced neuroprotection, neurogenesis, and angiogenesis after focal cerebral ischemia. J Clin Invest 111:1843-1851.

Suzuki M, Svendsen CN. 2008. Combining growth factor and stem cell therapy for amyotrophic lateral sclerosis. Trends Neurosci 31:192-198.

Suzuki M, McHugh J, Tork C, Shelley B, Klein SM, Aebischer P, Svendsen CN. 2007. GDNF-secreting human neural progenitor cells protect dying



motor neurons, but not their projection to muscle, in a rat model of familial ALS. PLoS One 2:e689.

Suzuki S, Tanaka K, Nogawa S, Ito D, Dembo T, Kosakai A, Fukuuchi Y. 2000. Immunohistochemical detection of leukemia inhibitory factor after focal cerebral ischemia in rats. J Cereb Blood Flow Metab 20:661-668.

Takahashi K, Yasuhara T, Shingo T, Muraoka K, Kameda M, Takeuchi A, Yano A, Kurozumi K, Agari T, Miyoshi Y, Kinugasa K, Date I. 2008. Embryonic neural stem cells transplanted in middle cerebral artery oc-clusion model of rats demonstrated potent therapeutic effects, compared to adult neural stem cells. Brain Res 1234:172-182.

Takeuchi H, Natsume A, Wakabayashi T, Aoshima C, Shimato S, Ito M, Ishii J, Maeda Y, Hara M, Kim SU, Yoshida J. 2007. Intravenously transplanted human neural stem cells migrate to the injured spinal cord in adult mice in an SDF-1- and HGF-dependent manner. Neurosci Lett 426:69-74.

Tamaki S, Eckert K, He D, Sutton R, Doshe M, Jain G, Tushinski R, Reitsma M, Harris B, Tsukamoto A, Gage F, Weissman I, Uchida N. 2002. Engraftment of sorted/expanded human central nervous system stem cells from fetal brain. J Neurosci Res 69:976-986.

Tavazoie M, Van der Veken L, Silva-Vargas V, Louissaint M, Colonna L, Zaidi B, Garcia-Verdugo JM, Doetsch F. 2008. A specialized vascular niche for adult neural stem cells. Cell Stem Cell 3:279-288.

Thored P, Arvidsson A, Cacci E, Ahlenius H, Kallur T, Darsalia V, Ekdahl CT, Kokaia Z, Lindvall O. 2006. Persistent production of neurons from adult brain stem cells during recovery after stroke. Stem Cells 24:739-747.

Toma JG, Akhavan M, Fernandes KJ, Barnabe-Heider F, Sadikot A, Kaplan DR, Miller FD. 2001. Isolation of multipotent adult stem cells from the dermis of mammalian skin. Nat Cell Biol 3:778-784.

Tsuboi Y, Kakimoto K, Akatsu H, Daikuhara Y, Yamada T. 2002. Hepato-cyte growth factor in cerebrospinal fl uid in neurologic disease. Acta Neurol Scand 106:99-103.

Tuttolomondo A, Di Raimondo D, di Sciacca R, Pinto A, Licata G. 2008. In-fl ammatory cytokines in acute ischemic stroke. Curr Pharm Des 14:3574-3589.

Tyler MA, Ulasov IV, Sonabend AM, Nandi S, Han Y, Marler S, Roth J, Lesniak MS. 2008. Neural stem cells target intracranial glioma to deliver an oncolytic adenovirus in vivo. Gene Ther 16:262-278.

Uchida N, Buck DW, He D, Reitsma MJ, Masek M, Phan TV, Tsukamoto AS, Gage FH, Weissman IL. 2000. Direct isolation of human central nervous system stem cells. Proc Natl Acad Sci U S A 97:14720-14725.

Valenzuela MJ, Dean SK, Sachdev P, Tuch BE, Sidhu KS. 2008. Neural precursors from canine skin: A new direction for testing autologous cell replacement in the brain. Stem Cells Dev 17:1087-1094.

Vallieres L, Campbell IL, Gage FH, Sawchenko PE. 2002. Reduced hip-pocampal neurogenesis in adult transgenic mice with chronic astrocytic production of interleukin-6. J Neurosci 22:486-492.

Vescovi AL, Gritti A, Galli R, Parati EA. 1999. Isolation and intracerebral grafting of nontransformed multipotential embryonic human CNS stem cells. J Neurotrauma 16:689-693.

Vignais L, Nait Oumesmar B, Mellouk F, Gout O, Labourdette G, Baron-Van Evercooren A, Gumpel M. 1993. Transplantation of oligodendro-cyte precursors in the adult demyelinated spinal cord: Migration and remyelination. Int J Dev Neurosci 11:603-612.

Vonsattel JP. 2008. Huntington disease models and human neuropathology: Similarities and differences. Acta Neuropathol 115:55-69.

Wang TT, Jing AH, Luo XY, Li M, Kang Y, Zou XL, Chen H, Dong J, Liu S. 2006. Neural stem cells: Isolation and differentiation into cholinergic neurons. Neuroreport 17:1433-1436.

Wang Y, Chen S, Yang D, Le WD. 2007. Stem cell transplantation: A prom-ising therapy for Parkinson’s disease. J Neuroimmune Pharmacol 2:243-250.

Windrem MS, Roy NS, Wang J, Nunes M, Benraiss A, Goodman R, McKhann GM 2nd, Goldman SA. 2002. Progenitor cells derived from the adult human subcortical white matter disperse and differentiate as oligodendrocytes within demyelinated lesions of the rat brain. J Neuro-sci Res 69:966-975.

Windrem MS, Schanz SJ, Guo M, Tian GF, Washco V, Stanwood N, Rasband M, Roy NS, Nedergaard M, Havton LA, Wang S, Goldman SA. 2008. Neonatal chimerization with human glial progenitor cells can both remyelinate and rescue the otherwise lethally hypomyelinated shiverer mouse. Cell Stem Cell 2:553-565.

Woodruff RH, Fruttiger M, Richardson WD, Franklin RJ. 2004. Platelet-derived growth factor regulates oligodendrocyte progenitor numbers in adult CNS and their response following CNS demyelination. Mol Cell Neurosci 25:252-262.

Wright LS, Li J, Caldwell MA, Wallace K, Johnson JA, Svendsen CN. 2003. Gene expression in human neural stem cells: Effects of leukemia inhibitory factor. J Neurochem 86:179-195.

Xu L, Ryugo DK, Pongstaporn T, Johe K, Koliatsos VE. 2009. Human neu-ral stem cell grafts in the spinal cord of SOD1 transgenic rats: Differen-tiation and structural integration into the segmental motor circuitry. J Comp Neurol 514:297-309.

Yagita Y, Kitagawa K, Ohtsuki T, Takasawa K, Miyata T, Okano H, Hori M, Matsumoto M. 2001. Neurogenesis by progenitor cells in the ischemic adult rat hippocampus. Stroke 32:1890-1896.

Zagzag D, Esencay M, Mendez O, Yee H, Smirnova I, Huang Y, Chiriboga L, Lukyanov E, Liu M, Newcomb EW. 2008. Hypoxia- and vascular endothelial growth factor-induced stromal cell-derived factor-1alpha/CXCR4 expression in glioblastomas: One plausible explanation of Scherer’s structures. Am J Pathol 173:545-560.

Zhang H, Vutskits L, Pepper MS, Kiss JZ. 2003. VEGF is a chemoattractant for FGF-2-stimulated neural progenitors. J Cell Biol 163:1375-1384.

Zhang H, Vutskits L, Calaora V, Durbec P, Kiss JZ. 2004. A role for the polysialic acid-neural cell adhesion molecule in PDGF-induced chemo-taxis of oligodendrocyte precursor cells. J Cell Sci 117:93-103.

Zhang P, Li J, Liu Y, Chen X, Kang Q. 2009. Transplanted human embry-onic neural stem cells survive, migrate, differentiate and increase en-dogenous nestin expression in adult rat cortical peri-infarction zone. Neuropathology 29:410-421.

Zhao D, Najbauer J, Garcia E, Metz MZ, Gutova M, Glackin CA, Kim SU, Aboody KS. 2008a. Neural stem cell tropism to glioma: Critical role of tumor hypoxia. Mol Cancer Res 6:1819-1829.

Zhao J, Zhang N, Prestwich GD, Wen X. 2008b. Recruitment of endoge-nous stem cells for tissue repair. Macromol Biosci 8:836-842.

Zhu W, Mao Y, Zhao Y, Zhou LF, Wang Y, Zhu JH, Zhu Y, Yang GY. 2005. Transplantation of vascular endothelial growth factor-transfected neu-ral stem cells into the rat brain provides neuroprotection after transient focal cerebral ischemia. Neurosurgery 57:325-333; discussion 325-333.


neural stem cell niches and homing: recruitment and integration

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