Human neural stem cells genetically modified for brain repair in neurological disorders

Existence of multipotent neural stem cells (NSC) has been known in developing or adult mammalian CNS, including humans. NSC have the capacity to grow indefinitely and have multipotent potential to differentiate into three major cell types of CNS, neurons, astrocytes and oligodendrocytes. Stable clonal lines of human NSC have recently been generated from the human fetal telencephalon using a retroviral vector encoding v‐myc. One of the NSC lines, HB1.F3, carries normal human karyotype of 46XX and has the ability to self‐renew, differentiate into cells of neuronal and glial lineages, and integrate into the damaged CNS loci upon transplantation into the brain of animal models of Parkinson disease, HD, stroke and mucopolysaccharidosis. F3 human NSC were genetically engineered to produce L‐dihydroxyphenylalanine (L‐DOPA) by double transfection with cDNA for tyrosine hydroxylase and guanosine triphosphate cylohydrolase‐1, and transplantation of these cells in the brain of Parkinson disease model rats led to L‐DOPA production and functional recovery. Proactively transplanted F3 human NSC in rat striatum, supported the survival of host striatal neurons against neuronal injury caused by 3‐nitropro‐pionic acid in rat model of HD. Intravenously introduced through the tail vein, F3 human NSC were found to migrate into ischemic lesion sites, differentiate into neurons and glial cells, and improve functional deficits in rat stroke models. These results indicate that human NSC should be an ideal vehicle for cell replacement and gene transfer therapy for patients with neurological diseases. In addition to immortalized human NSC, immortalized human bone marrow mesenchymal stem cell lines have been generated from human embryonic bone marrow tissues with retroviral vectors encording v‐myc or teromerase gene. These immortalized cell lines of human bone marrow mesenchymal stem cells differentiated into neurons/glial cells, bone, cartilage and adipose tissue when they were grown in selective inducing media. There is further need for investigation into the neurogenic potential of the human bone marrow stem cell lines and their utility in animal models of neurological diseases.     

经枕大池神经干细胞移植治疗大鼠创伤性脑损伤的研究

目的 将神经干细胞经枕大池移植到创伤性脑损伤模型大鼠蛛网膜下腔中并观察其存活、迁移和分化,从而为神经干细胞的体内存活、迁移和分化机理研究和临床应用提供实验依据.方法 体外培养BrdU标记的胚胎神经干细胞并应用免疫荧光细胞化学染色对BrdU、神经干细胞标记物nestin的表达进行鉴定:采用Feeney自由落体撞击法制做大鼠脑损伤模型,伤后24 h将BrdU标记的胚胎神经十细胞经立体定向注射移植到蛛网膜下腔;制作大鼠脑绢织石蜡切片,应用免疫组织化学染色检测BrdU、微管相关蛋白2(MAP2)、胶质纤维酸性蛋白(GFAP)表达;伤前24h、伤后24 h及1、2周行动物运动神经功能评分.结果 免疫荧光检测显示神经球的表面细胞表达nestin及BrdU:免疫组织化学染色检测到脑内损伤灶存在BrdU阳性神经干细胞、MAP2阳性神经元和GFAP阳性胶质细胞;接受神经十细胞移植的大鼠神经运动功能评分的恢复较对照组有明显提高,差异有统计学意义(P<0.05).结论 经枕大池移植到脑损伤大鼠蛛网膜下腔中的神经干细胞能存活且具有远距离迁移能力,并明显有助于脑损伤大鼠神经运动功能的恢复.     

Survival and Differentiation of Rat and Human Epidermal Growth Factor-Responsive Precursor Cells Following Grafting into the Lesioned Adult Central Nervous System

Epidermal Growth Factor (EGF)-responsive stem cells isolated from the developing central nervous system (CNS) can be expanded exponentially in culture while retaining the ability to differentiate into neurons and glia. As such, they represent a possible source of tissue for neural transplantation, providing they can survive and mature following grafting into the adult brain. In this study we have shown that purified rat stem cells generated from either the embryonic mesencephalon or the striatum can survive grafting into the striatum of rats with either ibotenic acid or nigrostriatal dopamine lesions. However, transplanted stem cells do not survive as a large mass typical of primary embryonic CNS tissue grafts, but in contrast form thin grafts containing only a small number of surviving cells. There was no extensive migration of transplanted stem cells labeled with either thelac-zgene or bromodeoxyuridine into the host region surrounding the graft, although a small number of labeled cells were seen in the ventral striatum some distance from the site of implantation. Some of these appeared to differentiate into dopamine neurons, particularly when the developing mesencephalon was used as the starting material for generating the stem cells. EGF-responsive stem cells could also be isolated from the mesencephalon of developing human embryos and expanded in culture, but only grew in large numbers when the gestational age of the embryo was greater than 11 weeks. Purified human CNS stem cells were also transplanted into immunosuppressed rats with nigrostriatal lesions and formed thin grafts similar to those seen when using rat stem cells. However, when primary cultures of human mesencephalon were grown with EGF for only 10 days and this mixture of stem cells and primary neural tissue was transplanted into the dopamine-depleted striatum, large well-formed grafts developed. These contained mostly small undifferentiated cells intermixed with a number of well-differentiated TH-positive neurons. These results show that purified populations of rat or human EGF-responsive CNS stem cells do not form large graft masses or migrate extensively into the surrounding host tissues when transplanted into the adult striatum. However, modifications of the growth conditionsin vitromay lead to an improvement of their survivalin vivo.     

菲立磁标记兔骨髓基质源神经干细胞自体移植入纹状体后的形态学观察

目的将体外标记的骨髓基质源神经干细胞经单细胞悬液微移植后观察其在兔纹状体的存活、迁移、分化和整合情况，为细胞移植治疗疾病奠定基础。方法分离兔骨髓基质细胞，利用神经干细胞培养基、白血病抑止因子和碱性成纤维母细胞生长因子进行细胞扩增并诱导成骨髓基质源神经干细胞，再经菲立磁和活细胞荧光染料PKH67标记后．采用微移植的方法，通过脑立体定位仪，用微玻璃针将干细胞分别植入兔脑纹状体内。存活1、4、8周后处死动物，组织切片，利用光镜和电镜观察标记细胞在脑内的形态学情况。结果菲立磁标记的兔骨髓基质源神经干细胞经微移植后可在兔脑内纹状体区域存活，移植的干细胞可向周围的脑实质内迁移和整合，迁移细胞沿特定的纹状体结构分布。少量菲立磁标记的干细胞可以分化成神经元。结论骨髓基质源神经干细胞移植后．可在脑实质内存活、迁移、分化和整合，这种细胞可能成为中枢神经系统自体移植的细胞来源。     

神经干细胞的来源

神经干细胞是近年来神经科学领域研究的一个热点。神经干细胞可来源于胚胎干细胞和成年干细胞，前者包括早期胚胎细胞和胎儿神经组织细胞，由于从胚胎获取干细胞面l临伦理学的束缚，从成年来源的神经干细胞将是未来临床应用更具可行性的途径。成年来源的神经干细胞包括存在于成年神经组织中的干细胞和从其他组织中分化得到的干细胞，其中骨髓基质细胞具有多分化潜能，在适当的条件下可以诱导分化出神经干细胞，目前备受关注。     

Behavior of human neural progenitor cells transplanted to rat brain

Human neural stem/progenitor cells provide a useful tool for studies of neural development and differentiation, as well as a potential means for neuroreplacement therapeutic needs in the human CNS. Stem cells isolated from developing human central nervous system of 8-12-week fetuses were transplanted to the forebrain and cerebellum of young and adult rats after 14 days of in vitro expansion. Cells were labeled by bisbenzimide prior to transplantation without immunosuppression. Recipient brains were examined 10 and 20 days after transplantation. Labeled stem cells were found in the neocortex, lateral ventricle and caudate nucleus in the forebrain, and in the molecular layer, Purkinje cell layer, and granular layer of the cerebellum. Mitotically dividing stem cells were observed in graft core, confirming their proliferative potential in new microenvironment. Engrafted cells migrate through the parenchyme of striatum, along the ventricular ependymal layer and callosal fibers, some of them reaching the opposite hemisphere. Some cells migrating along the capillaries express glial acid fibrillary protein, demonstrating their differentiation into astrocytes. Grafted cells expressing calbindin were found in the Purkinje cell layer, suggesting their differentiation into the Purkinje cells. At the same time, some grafted cells were undifferentiated and expressed vimentin. Our results demonstrate that cultured human neural stem/progenitor cells migrate and differentiate into both neurons and astrocytes after transplantation to the rat forebrain or cerebellum of young and adult rats.     

Neural stem cells are increased after loss of β-catenin, but neural progenitors undergo cell death

Neurons and glia in the central nervous system originate from neural stem and progenitor cells that reside in the ventricular zones. Here we examine the role of β-catenin in neural stem cell (NSC) regulation in mouse embryos lacking β-catenin specifically in the brain germinal zone. An in vitro clonal neurosphere assay was performed in order to ascertain the status of the NSC population. Intact neurospheres did not form from β-catenin-null cells due to a loss of cell adhesion and the number of expanded cells was reduced. Rescue of β-catenin expression restored adhesion and revealed that the number of NSCs increased in the knockout population. Using a clonal colony-forming assay, which confines precursor cells within a solid collagen matrix, we show that the number of NSCs in the hippocampus is unchanged although the β-catenin knockout striatum actually contains a larger proportion of NSCs. However, these colonies were smaller than those of control cells, due to increased apoptosis in the progenitor population. Furthermore, β-catenin knockout NSCs also retained multipotentiality as shown by their ability to clonally differentiate into neurons and glia. The effects on neural precursor cells were not due to loss of downstream T-cell factor signaling, as this pathway is not active in vivo in regions of the embryonic brain where NSCs and progenitor cells reside, nor is it active in vitro in NSC colonies. These data reveal that β-catenin is not required for the maintenance or differentiation of NSCs, but is required for the adhesion and survival of neural progenitor cells.     

Quiescent neural cells regain multipotent stem cell characteristics influenced by adult neural stem cells in co-culture

The source of cells participating in central nervous system (CNS) tissue repair and regeneration is poorly defined. One possible source is quiescent neural cells that can persist in CNS in the form of dormant progenitors or highly specialized cell types. Under appropriate conditions, these quiescent cells may be capable of re-entering the mitotic cell cycle and contributing to the stem cell pool. The aim of this study was to determine whether in vitro differentiated neural stem cells (NSC) can regain their multipotent-like stem cell characteristics in co-culture with NSC. To this end, we induced neural differentiation by plating NSC, derived from the periventricular subependymal zone (SEZ) of ROSA26 transgenic mice in Neurobasal A/B27 medium in the absence of bFGF. Under these conditions, NSC differentiated into neurons, glia, and oligodendrocytes. While the level of Nestin expression was downregulated, persistence of dormant progenitors could not be ruled out. However, further addition of bFGF or bFGF/EGF with conditioned medium derived from adult NSC did not induce any noticeable cell proliferation. In another experiment, differentiated neural cells were cultured with adult NSC, isolated from the hippocampus of Balb/c mice, in the presence bFGF. This resulted in proliferating colonies of ROSA26 derived cells that mimicked NSC in their morphology, growth kinetics, and expressed NSC marker proteins. The average nuclear area and DAPI fluorescence intensity of these cells were similar to that of NSC grown alone. We conclude that reactivation of quiescent neural cells can be initiated by NSC-associated short-range cues but not by cell fusion.     

大鼠脊髓损伤后PLGA支架细胞髓内移植的组织学观察

目的 观察神经干细胞(NSC)、许旺细胞(SCs)和组织工程材料乙交酯-丙交酯共聚物(PLGA)大鼠髓内共移植后的病理形态学改变.方法 36只Wistar大鼠,随机分为PLGA移植组、NSC/PLGA组和NSC+SCs/PLGA组.体外培养、鉴定胚胎脊髓源NSC和SCs,制备和构建PLGA支架细胞复合体并移植到大鼠脊髓Tq半横断损伤部位,应用HE染色、电镜和免疫组织化学染色方法在形态结构上观察材料的组织相容性、轴突髓鞘再生及NSC在脊髓内的存活、迁移和分化情况.结果 HE染色观察损伤12周时移植材料内可见细胞生长及新生的毛细血管;扫描电镜观察随着时间的延长,PLGA逐渐降解;材料正中横断面透射电镜观察可见新牛的无髓及有髓神经纤维;脊髓标本免疫组织化学染色可见移植的NSC可以在宿主脊髓内存活、迁移并分化成类神经元样细胞和少枝胶质细胞,未分化成星形胶质细胞.结论 NSC、SCs和PLGA共移植可以在形态学上促进大鼠脊髓半横断损伤的修复.     

Intracerebral transplantation of neural stem cells combined with trehalose ingestion alleviates pathology in a mouse model of Huntington's disease

The present investigation examined the neuroprotective benefits for combined trehalose administration with C17.2 neural stem cell transplantation in a transgenic mouse model of Huntington's disease (HD), R6/2. C17.2 neural stem cells have the potential of differentiating into a neuronal phenotype in vitro and have been shown to be effective in the treatment of a variety of lysosomal lipid storage disorders in the nervous system. In this study, we transplanted these cells into the lateral ventricle of R6/2 transgenic mice in order to examine the efficacy of using these cells for correcting the accumulated polyglutamine storage materials in HD. To improve efficacy, animals were fed with a diet rich in trehalose, which has been shown to be beneficial to retard aggregate formation. The combined treatment strategy not only decreased ubiquitin-positive aggregation in striatum, alleviated polyglutamine aggregation formation, and reduced striatal volume, but also extended life span in the R6/2 animal model. Behavioral evaluation showed that the combination treatment improved motor function. Statistical analysis revealed that the combination treatment was more effective than treatment with trehalose alone on the basis of the above biochemical and behavioral criteria. This study provides a strong a basis for further developing an effective therapeutic strategy for HD.     

Target-specific outgrowth from human mesencephalic tissue grafted to cortex or ventricle of immunosuppressed rats.

Human fetal mesencephalic tissue was grafted to rats with unilateral lesions of the nigrostriatal pathway. The animals were immunosuppressed with cyclosporine A. Grafts were placed either into the lateral ventricle ipsilateral to the lesion or in the cingulate cortex above corpus callosum. The grafts and newly formed fibers were visualized by immunohistochemistry with antibodies against tyrosine hydroxylase (TH) and the human Thy-1 glycoprotein. TH-positive fibers covered the total volume of striatum when the graft was placed either in the ventricle or in the cortex. When the transplant was located in the ventricle, TH-positive cells migrated from the graft into host striatum. No cell migration was seen into any other areas than striatum. Cortex and septum were sparsely reinnervated by the graft, but not to a density higher than that normally seen. Globus pallidus was totally devoid of TH-positive fibers. When the graft was placed in cingulate cortex, fiber bundles penetrated through corpus callosum into either striatum, to arborize in its dorsal parts, or followed the medial side of the lateral ventricle to ventral limbic areas, where a fiber network also was formed. Human specific Thy-1-immunohistochemistry revealed positivity only on the lesioned side. These data suggest that dopamine neurons in human mesencephalic tissue, grafted to the rat brain, can migrate specifically into host striatum. Furthermore, TH-positive fiber outgrowth occurred only into dopamine denervated areas of the host, avoiding areas that are normally not innervated by nigral neurons, but also able to reach distant target cells.     

Identification and early characterization of genetically modified NGF-producing neural stem cells grafted into the injured adult rat brain

OBJECTIVE: To investigate whether genetically modified mouse neural stem cells (NSC) expressing recombinant human nerve growth factor (rhNGF) and transplanted in chemically injured rat brain, can survive and eventually acquire phenotypic characteristics of early nerve cells. METHODS: Stably high expression of rhNGF in NSC was obtained by a new lentivirus-mediated expression system. To test the effectiveness of hNGF secreted by rhNGF-NSC, hereby we performed either a bioassay for neurite outgrowth in PC12 rat cells or immunoblot analysis for TrkA, the high-affinity NGF receptor, from engineered NSC. rhNGF and mock-NSC were grafted into adult injured rats striatum and 3 days later, animals were killed, and brains were removed and examined by immunohistochemical analysis. RESULTS: The results showed that rhNGF-producing NSC cultured for extended period of time release bioactive hNGF in the culture media which promotes PC12 neuronal differentiation and correlates with the up-regulation of TrkA. rhNGF-NSC transplanted into the injured brain can survive, produce hNGF and induce the expression of NGF receptors, p75(NTR) and TrkA. Discussion:In vitro and in vivo experiments confirmed the ability of rhNGF-NSC to secrete bioactive hNGF. Our data provide by means of genetically modified rhNGF-producing NSC, a useful experimental tool to test the potential clinical effectiveness of trophic factors relevant to central nervous system (CNS).     

神经干细胞移植治疗小鼠机械性脑损伤的实验研究

目的探讨神经干细胞移植后的体内存活、增殖与分化,及其对小鼠机械性脑损伤的治疗作用。方法运用牙科钻制作小鼠运动区皮质机械性损伤模型。48只清洁级昆明小鼠,雌雄不拘,体质量为18～20g,按体质量编号随机分为4组:神经干细胞移植组(损伤后原位移植经鉴定确认的原代培养的小鼠神经干细胞)、3T3移植组(损伤后原位移植3T3细胞)、单纯损伤组(损伤后不行神经干细胞移植)和空白对照组(仅施行麻醉),每组12只小鼠。于伤后第3天进行行为学检测;第10、30天行损伤区脑组织nestin及NF200免疫荧光染色,观察神经干细胞生长、分化情况。结果损伤后,获得原代培养的神经干细胞在移植早期贴附于损伤区域且向周边组织呈浸润生长;移植后期Hoechst33342及NF200染色显示损伤区附近可见分化形成的神经元。单纯损伤组小鼠出现偏瘫症状;而神经干细胞移植组小鼠植入神经干细胞后则症状减轻,运动功能明显改善,与其他各组相比差异有显著性意义(P<0.001)。结论神经干细胞移植能够改善小鼠机械性脑损伤后的神经功能状态。     

胚鼠室管膜及成鼠骨髓神经干细胞分离培养及分化鉴定实验研究

目的 :探寻胚鼠室管膜和成鼠骨髓分离培养神经干细胞 (NSC)的可行性。方法 :将分离的胚脑室管膜组织或成年骨髓细胞分别特殊培养。以细胞克隆及免疫细胞化学方法判断NSC增殖并鉴定NSC、神经元和神经胶质细胞。结果 :两种组织来源细胞在相应培养条件下NSC均有快速增殖。可得到具有长突起并建立有网状联系的神经元及胶质细胞。结论 :由胚鼠室管膜和成鼠骨髓诱导分化NSC是可行的     

神经干细胞移植途径的理论研究进展

神经干细胞是指来源于神经组织或能分化为神经组织、具有自我更新能力和多向分化潜能的一类细胞,近年来神经干细胞研究成为治疗神经退行性疾病和中枢神经系统损伤的热点。移植入宿主体内的神经干细胞能够向神经系统病变部位趋行、聚集,并能够存活、增殖、分化为神经元和/或胶质细胞,从而促进宿主缺失功能的部分恢复。如何将神经干细胞准确、安全移植到宿主体内,并最终迁移、聚集到脑内功能缺失部位成为该技术发展的一个重要环节。文章就目前神经干细胞动物实验和临床研究中较多采取的移植途径,包括局部注射移植、经脑脊液注射移植、经血液循环注射移植的研究进展加以概述,比较这3种方法各自的优缺点,分析神经干细胞移植的安全性和有效性,探讨哪种移植途径才是神经干细胞最适合的移植方法。     

Cortex- and striatum- derived neural stem cells produce distinct progeny in the olfactory bulb and striatum

Neural stem cells can be isolated from the mouse embryonic cortex but do not persist in the adult cortex. In contrast, neural stem cells from the striatal embryonic germinal zone persist in the adult subependyma. Emx1-lineage analysis revealed that cortex-derived neural stem cells survive and migrate ventrally into the subependyma where they intermix with the host striatal neural stem cells [S. Willaime-Morawek et al. (2006)J. Cell Biol. 175, 159-168]. Cortex-derived cells proliferate faster in the subependyma and reach the olfactory bulb earlier than striatum-derived cells. In the olfactory bulb, cortex-derived cells produce more cells and more dopaminergic neurons in the glomerular layer than striatum-derived cells. Cortex-derived cells also give rise to more astrocytes and less neurons in the striatum than striatum-derived cells. Thus, history matters; cortex-derived neural stem cells in the subependyma give rise to progeny in the olfactory bulb and striatum but in different proportions than striatum-derived neural stem cells.     

大鼠胚胎神经干细胞的冷冻复苏

目的：建立大鼠胚胎神经干细胞冷冻复苏方法，探讨冻存后神经干细胞的活力及生物学特性。方法：采用10％BSA＋7．5％DMSO作冷冻保护剂，于液氮中冻存；采用细胞培养和间接免疫荧光染色方法对冻存后细胞的活力，形态及分化能力作鉴定。结果：不同的冻存时间，细胞代数，组织来源以及神经营养因子对冻存后细胞存活率没有明显差异（P＞0．05）。冷冻保存复苏后培养的大鼠胚胎神经干细胞能够存活，能在体外多次传代，并能分化成神经元，星形胶质细胞细胞和少突胶质细胞。结论：大鼠神经干细胞的冻存复苏并不影响其原有的生物学特性包括其正常的，增殖能力和多向分化能力。     

Intracerebral grafting of cell line or patient-derived neural stem cells for the treatment of neurological disorders]

Due to the development of molecular biology techniques, several types of neurotransmitter or neurotrophic factor secreting cell line can be established. These cell lines were grafted into the brain of animal models of Parkinson's disease and cerebral ischemia after encapsulating into the hollow fiber consisted of semipermeable membrane. Immunological reaction and tumor formation were prevented and functional effects were observed histologically, chemically and behaviorally. Current issues regarding encapsulated cell grafting are: delivery of neurotransmitter and neurotrophic factor simultaneously from one capsule, usage of human-derived cell lines and control of secretion from outside. There are two possible approaches regarding the usage of patient's own neural stem cells for regenerative therapy. Neural stem cells are collected from the subventricular zone of the lateral ventricle and these cells are differentiated into dopaminergic neurons using tyrosine hydroxylase induction cocktail (TH cocktail). Then, these neurons are grafted into the striatum of the patient. Another method is to inject TH cocktail into the patient's striatum in order to induce differentiation of dopaminergic neurons from the neural stem cells in vivo.     

碱性成纤维生长因子和表皮生长因子对脊髓神经干细胞增殖与分化的影响

目的观察碱性成纤维生长因子(bFGF)和表皮生长因子(EGF)对胚胎脊髓神经干细胞(NSC)增殖与分化的影响。方法从14 d胚胎大鼠的脊髓组织中分离培养脊髓NSC,并随机分为3组:EGF组、bFGF组和bFGF+EGF组。通过光镜观察不同时间点各组脊髓NSC克隆细胞团数量及直径大小,并采用免疫荧光染色检测各组脊髓NSC向神经元和星形胶质细胞分化的情况。结果①EGF组培养1、3、7 d后NSC克隆细胞团数量和直径均少于bFGF和bFGF+EGF组,差异有统计学意义(P0.05)。而bFGF+EGF组仅在培养1 d时克隆细胞团数量多于bFGF组,在培养3、7 d时差异无统计学意义。②EGF组分化细胞中神经元比例显著少于bFGF和bFGF+EGF组,星形胶质细胞数量明显大于bFGF和bFGF+EGF组,差异有统计学意义(P0.05)。而bFGF和bFGF+EGF组组间差异无统计学意义。结论 EGF对脊髓NSC克隆形成有一定作用,而bFGF能较好地促进克隆细胞团的形成及生长,两者联合应用在培养早期可显著促进克隆细胞团形成。EGF可诱导脊髓NSC更多分化为星形胶质细胞,而bFGF则可促进脊髓NSC向神经元分化。     

Activated neural stem cells contribute to stroke-induced neurogenesis and neuroblast migration toward the infarct boundary in adult rats.

Stroke increases neurogenesis. The authors investigated whether neural stem cells or progenitor cells in the adult subventricular zone (SVZ) of rats contribute to stroke-induced increase in neurogenesis. After induction of stroke in rats, the numbers of cells immunoreactive to doublecortin, a marker for immature neurons, increased in the ipsilateral SVZ and striatum. Infusion of an antimitotic agent (cytosine-beta-D-arabiofuranoside, Ara-C) onto the ipsilateral cortex eliminated more than 98% of actively proliferating cells in the SVZ and doublecortin-positive cells in the ipsilateral striatum. However, doublecortin-positive cells rapidly replenished after antimitotic agent depletion of actively proliferating cells. Depleting the numbers of actively proliferating cells in vivo had no effect on the numbers of neurospheres formed in vitro, yet the numbers of neurospheres derived from stroke rats significantly (P<0.05) increased. Neurospheres derived from stroke rats self-renewed and differentiated into neurons and glia. In addition, doublecortin-positive cells generated in the SVZ migrated in a chainlike structure toward ischemic striatum. These findings indicate that in the adult stroke brain, increases in recruitment of neural stem cells contribute to stroke-induced neurogenesis, and that newly generated neurons migrate from the SVZ to the ischemic striatum.