神经干细胞壁龛与脑肿瘤干细胞壁龛的相关性研究

脑肿瘤干细胞(braintumor stem cells,BTSCs)发现以来,BTSCs的来源成为研究热点,越来越多的研究表明BTSCs起源于神经干细胞(neural stem sells,NSCs)的基因突变 [1],而最新提出的干细胞壁龛(niche)学说认为壁龛作为十细胞生存的微环境,通过与干细胞之间的直接和(或)间接作用影响干细胞的增殖和分化.     

Mesenchymal stem cells expressing neural antigens instruct a neurogenic cell fate on neural stem cells

The neurogenic response to injury in the postnatal brain is limited and insufficient for restoration of function. Recent evidence suggests that transplantation of mesenchymal stem cells (MSCs) into the injured brain is associated with improved functional recovery, mediated in part through amplification in the endogenous neurogenic response to injury. In the current study we investigate the interactions between bone marrow-derived MSCs and embryonic neural stem cells (NSCs) plus their differentiated progeny using an in vitro co-culture system. Two populations of MSCs were used, MSCs induced to express neural antigens (nestin+, Tuj-1+, GFAP+) and neural antigen negative MSCs. Following co-culture of induced MSCs with differentiating NSC/progenitor cells a significant increase in Tuj-1+ neurons was detected compared to co-cultures of non-induced MSCs in which an increase in astrocyte (GFAP+) differentiation was observed. The effect was mediated by soluble interactions between the two cell populations and was independent of any effect on cell death and proliferation. Induced and non-induced MSCs also promoted the survival of Tuj-1+ cell progeny in long-term cultures and both promoted axonal growth, an effect also seen in differentiating neuroblastoma cells. Therefore, MSCs provide instructive signals that are able to direct the differentiation of NSCs and promote axonal development in neuronal progeny. The data indicates that the nature of MSC derived signals is dependent not only on their microenvironment but on the developmental status of the MSCs. Pre-manipulation of MSCs prior to transplantation in vivo may be an effective means of enhancing the endogenous neurogenic response to injury.     

A note on the distribution of glial cells in the molecular layer of the dentate gyrus

KISHI, K., B. B. STANFIELD AND W. M. COWAN. A note on the distribution of glial cells in the molecular layer of thedentate gyrus. BRAIN RES. BULL. 4(1) 35–41, 1979.—The distribution of the perikarya of astrocytes and other glial cells in the molecular layer of the dentate gyrus has been studied in gold chloride-sublimate preparations of rats and of normal and reeler mice, and in plastic embedded material from young adult rats. Contrary to previous reports (Rose et al. [7]), we have found no evidence for a distinct “line” or “band” of astrocytic cell bodies along the interface between the zones of termination of the entorhinal and hippocampal afferents to the dentate gyrus. Indeed, apart from a conspicuous accumulation of astrocytes immediately beneath the pial surface and hippocampal fissure, the distribution of glial cells across the extent of the molecular layer appears to be more or less random. In view of this it is difficult to ascribe a critical role to the astrocytes in either determining the normal distribution of afferent fibers to the dentate gyrus or in promoting their re-organization following its partial deafferentation.     

Proliferation of neuronal precursor cells in the dentate gyrus is accelerated after transient forebrain ischemia in mice

We investigated the proliferation of neuronal progenitor cells by labeling dividing cells by systemic application of the thymidine analog 5-bromodeoxyuridine (BrdU) during transient forebrain ischemia in mice. At 3 (n=6), 7 (n=6), 10 (n=6), and 17 days (n=6) after reperfusion, BrdU-labeled cells were detected in the dentate gyrus and paraventricle lesion. After ischemia-reperfusion, BrdU-labeled cells in the dentate gyrus significantly increased in number but not in the paraventricle lesion. These observations may help to clarify the mechanism of functional recovery after stroke.     

A niche for adult neurogenesis in social behavior

The structural and functional changes occurring into the brain is the hallmark of its tremendous capacity for dealing with the complexity that we are facing throughout life. It is also the hallmark of what neuroscientists refer as neuroplasticity. The continuous generation of cohorts of new neurons in some discrete regions of the adult brain, including the olfactory system, is a newly recognized form of neuroplasticity that has been recently the focus of neuroscience studies. Several lines of evidence indicate that this recruitment of newly-generated neurons is extremely sensitive to the overall neuronal activity of the host circuits. Therefore, adult neurogenesis represents, not only a constitutive replacement mechanism for lost neurons, but also a process supporting a capacity of neural plasticity in response to specific experience throughout life. The remarkable complexity of the social life offers a host of daily challenges that require a diversity of brain mechanism to make sense of the ever-changing social world.This review describes some recent findings which have begun to define reciprocal relationships between the production and integration of newborn neurons in the adult brain and social behavior. These studies demonstrate how this domain of research has the potential to address issues in the functional contribution of adult neurogenesis in the expression of some social traits as well in the role of some social contexts to finely regulate the production, survival and integration of adult newborn neurons.     

卡马西平对匹罗卡品诱导成年癫间疒大鼠海马齿状回神经前体细胞增殖的影响

目的研究卡马西平对成年癫大鼠海马齿状回内源性神经前体细胞增殖的影响。方法采用氯化锂和匹罗卡品联合诱导大鼠癫模型,将癫大鼠随机分为癫对照组和癫卡马西平组,正常大鼠随机分为正常对照组和正常卡马西平组。癫对照组和正常对照组给以蒸馏水灌胃,同时癫卡马西平组和正常卡马西平组给予卡马西平灌胃。于灌胃后第6d腹腔注射5-溴脱氧尿苷嘧啶(BrdU)标记海马齿状回的内源性神经前体细胞的增殖情况;用免疫组化方法观察各组大鼠在注射BrdU后第1d、第7d齿状回BrdU阳性细胞数量的表达。结果①注射BrdU后第1d,癫对照组大鼠海马齿状回BrdU阳性细胞数较正常对照组明显增加(P<0.01),癫卡马西平组大鼠海马齿状回BrdU阳性细胞数较癫对照组减少(P<0.05);②注射BrdU后第7d,癫对照组大鼠海马齿状回BrdU阳性细胞数较正常对照组明显增加(P<0.01),癫卡马西平组大鼠海马齿状回BrdU阳性细胞数较癫对照组明显减少(P<0.05)。结论卡马西平抑制癫大鼠海马齿状回内源性神经前体细胞增殖。     

Glutamate-induced gamma oscillations in the dentate gyrus of rat hippocampal slices

In this paper we show that gamma oscillations can be elicited by brief (< or = 200 ms) local applications of glutamate in the dentate gyrus of rat hippocampal slices. Dentate gamma oscillations show an initial peak frequency of approximately 70 Hz and last for up to 4 min. The network activity involves functional GABA(A) receptors as it is drastically reduced by GABA(A) receptor antagonists. The oscillations can be observed in the whole dentate gyrus-CA3-network and are coherent between the dentate gyrus and area CA3 for variable periods. Thus, long-lasting gamma oscillations can be experimentally induced in the dentate gyrus and are propagated into the hippocampus proper.     

神经干细胞移植对视网膜节细胞再生的影响

目的探讨神经干细胞（NSCs）在视神经损伤后对视网膜节细胞轴突再生的作用及其在视神经内迁移和分化。方法实验动物分对照组（PBS组），实验组（NSCs组）；成年SD大鼠在眼球后1min处切断视神经。移植NSCs或PBS至视神经断端；4周后以霍乱毒素B亚基顺行标记观察轴突再生情况，并观察NSCs在视神经内的迁移及免疫组织化学法检测移植后的细胞表达神经丝蛋白（NF）、2，3-环核苷酸磷酸二酯酶（CNP）、胶质纤维酸性蛋白（GFAP）的情况。结果4周后视网膜节细胞再生轴突穿过视神经断端到达远端，移植的NSCs分化为星形胶质细胞并在视神经内迁移0．5～1min。免疫组织化学法检测NSCs部分呈GFAP阳性，未见NF、CNP表达。结论NSCs移植可促进视网膜节细胞轴突再生，能在视神经内迁移并在视神经周围分化为星形胶质细胞。     

Electron microscopic study of the gerbil dentate gyrus after transient forebrain ischemia

Summary Silver impregnation performed 1–2 days after transient forebrain ischemia in the Mongolian gerbil demonstrated terminal-like granular deposits in the outer two-thirds of the hippocampal dentate molecular layer (perforant path terminal zone), even though neither the cell bodies of origin of the perforant path nor the dentate granule cells were destroyed. Electron microscopic studies of the dentate gyrus were performed in an effort to discover the identity of these degenerating structures. Electron microscopy revealed that the granular silver deposits corresponded to electron-dense profiles. Many of these were degenerating boutons and some were degenerating postsynaptic dendritic fragments, but most of them could not be identified with certainty. Electron-dense profiles were less numerous than expected from the density of granular silver deposits. These structures were probably the degenerating axons, axon terminals and dendrites of CA4 neurons. The granular silver deposits and electron-dense boutons observed in the inner third of the dentate molecular layer 5 days after transient ischemia can probably be explained by the ischemia-induced degeneration of CA4 mossy cells, which give rise to the dentate associational-commissural projection. Finally, most mossy fiber boutons in area CA4 and some boutons in the molecular layer appeared watery and enlarged on postischemia days 1 and 2. Mossy fiber boutons with this ultrastructural appearance have previously been observed in seizure-prone animals and in animals undergoing convulsant-induced seizures. Although no postischemic seizures occur under the conditions of this study, these findings support the idea that excitatory pathways become hyperactive after transient ischemia.Supported by NIH Stroke Center grant NS 06233     

Time-sensitive effects of hypoxia on differentiation of neural stem cells derived from mouse embryonic stem cells in vitro

Abstract

Objectives:

Oxygen tension is an important component of microenvironment for the differentiation of embryonic stem cells including neural lineage. However, the comprehensive influence of hypoxia on neural differentiation during embryonic neural development has not yet been examined.

Methods:

In this study, we investigated the effect of low oxygen levels (5% O₂), or hypoxia, in two stages of neural differentiation in vitro: (1) inducing mouse embryonic stem cells into neural stem cells (NSCs); and then (2) inducing NSCs into neural progenitor cells in neurospheres.

Results:

In the first stage, NSCs generation was reduced under hypoxia. Less mature morphological changes (including neural marker) of NSCs were observed, suggesting the prevention of early differentiation under hypoxic conditions. Thus undifferentiated stem cells were maintained in this stage. However, in the second stage, hypoxia induced neural differentiation in neurospheres. Nevertheless, non-neural progenitor cell formation, such as mesoderm progenitor cell lines or epithelial cell lines, was restricted by low oxygen tension.

Discussions:

Our results demonstrate that hypoxia is essential for regulating neural differentiation and show the different effects on NSC differentiation dependent on the time-course of NSC development. In the early stage of NSCs induction, hypoxia inhibits neural differentiation and maintains the undifferentiated state; in the later stage of NSCs induction, hypoxia induces neural differentiation. Our study may contribute to the development of new insights for expansion and control of neural differentiation.     

Nestin-positive cells in the spinal cord: a potential source of neural stem cells

Some literatures have reported neural precursor cells (NPCs) exist in spinal cord of adult mammal, however, the NPCs distribution feature in spinal cord of adult mice so far is not described in detail. In order to observe and compare the distribution feature of NPCs in various spinal cord regions of adult mice, to research a potential source of neural stem cells (NSCs), we obtained NPCs distribution feature by analyzing the distribution of the nestin-containing cells (NCCs) in spinal cord of adult nestin second-intron enhancer controlled LacZ reporter transgenic mice (pNes-Tg) with LacZ staining and positive cell quantification. The results showed that: NCCs were observed in various regions of spinal cord of adult mice, but amount of NCCs was different in distinct region, the rank order of NCCs amount in various spinal cord regions was dorsal horn region greater than central canal greater than the ventral and lateral horn. NCCs in dorsal horn region mainly distributed in substantia gelatinosa, NCCs in central canal mainly distributed in ependymal zone, on the contrary, NCCs in ventral, lateral horn, medullae, nucleus regions of spinal cord were comparatively less. The rank order of NCCs amount in various spinal cord segments was cervical segment greater than lumbar sacral segment greater than thoracic segment. There was no significantly difference between NCCs amount in the left and right sides, and within cervical 1–7, thoracic 1–12, lumbar 1–5, sacral segment of spinal cord in adult mice. These data collectively indicate that NPCs extensively distribute in various regions of spinal cord of adult mice, especially in substantia gelatinosa and ependymal zone. NPCs in cervical segment are abundant, NPCs in thoracic segment are the least while compared the different spinal cord segment, the NPCs in various regions of spinal cord of adult mice are a potential source of NSCs.     

Downregulation of the LAR protein tyrosine phosphatase receptor is associated with increased dentate gyrus neurogenesis and an increased number of granule cell layer neurons

Growth factors stimulating neurogenesis act through protein tyrosine kinases which are counterbalanced by protein tyrosine phosphatases (PTPs); thus, downregulation of progenitor PTP function might provide a novel strategy for promoting neurogenesis. We tested the hypotheses that the leukocyte common antigen-related (LAR) PTP is present in adult dentate gyrus progenitors, and that its downregulation would promote neurogenesis. In adult mice, LAR immunostaining was present in Ki-67- and PCNA-positive subgranular zone cells. At 1 h post-BrdU administration, LAR-/- mice demonstrated an approximately 3-fold increase in BrdU- and PCNA-positive cells, indicating increased progenitor proliferation. At 1 day and 4 weeks following 6 days of BrdU administration, LAR-/- mice exhibited a significant increase in BrdU and NeuN colabeled cells consistent with increased neurogenesis. In association with increased neurogenesis in LAR-/- mice, stereological analysis revealed a significant 37% increase in the number of neurons present in the granule cell layer. In cultured progenitor clones derived from LAR+/+ mice, LAR immunostaining was present in PCNA- and BrdU-positive cells. Progenitor clones derived from adult LAR-/- hippocampus or LAR+/+ clones made LAR-deficient with LAR siRNA demonstrated increased proliferation and, under differentiation conditions, increased proportions of Tuj1- and MAP2-positive cells. These studies introduce LAR as the first PTP found to be expressed in dentate progenitors and point to inhibition of LAR as a potential strategy for promoting neurogenesis. These findings also provide a rare in vivo demonstration of an association between increased dentate neurogenesis and an expanded population of granule cell layer neurons.     

High frequency oscillations in the dentate gyrus of rat hippocampal slices induced by tetanic stimulation

Tetanic stimulation induces high-frequency network oscillations in area CA1 and in the subiculum of rat hippocampal slices. Here, we describe the effects of similar tetanic stimulation in the molecular layer of the dentate gyrus. We found field potential oscillations in the dentate granule cell layer which shared several properties with tetanically induced oscillations in CA1, including delayed onset, duration, progressive slowing of frequency within the oscillations and sensitivity to blockers of GABA(A) receptors, NMDA receptors and metabotropic glutamate receptors. However, the mean frequency of the oscillations in the dentate is approximately 100 Hz, much higher than tetanic oscillations in CA1 and, in contrast to CA1, dentate high-frequency oscillations are sensitive to antagonists of AMPA-receptors. Oscillation frequency was decreased by metabotropic glutamate receptor antagonists and increased by antagonists of AMPA-receptors as well as the gap junction blocker carbenoxolone. The oscillations can be observed in the whole dentate gyrus-CA3-network and are tightly correlated between the dentate gyrus and area CA3. Thus, tetanic stimulation in the dentate elicits a new pattern of network oscillations with coherence in the dentate-CA3-network which may affect the processing of afferent information in the hippocampus.     

Estimating the number of granule cells in the dentate gyrus with the disector

A practical example is given of how a newly developed stereological estimator of particle number, the disector, can be used to make estimates of neuron number in the dentate gyrus of rats. The estimates are free of biases related to lost caps, overprojection and assumptions about size, shape and orientation of the objects that are counted. The disector principle and the practical considerations relating to histological preparations and sampling are presented.     

次声对成年大鼠齿状回神经前体细胞增殖的影响

目的研究次声对成年大鼠海马齿状回神经前体细胞增殖的影响。方法大鼠随机等分为正常对照组、假次声组和次声组（每组16只）。次声组暴露于8Hz、130dB次声环境7d（2h／d），暴露结束后第1、3、7、14d处死，采用抗5-溴脱氧尿嘧啶尿苷（BrdU）免疫组化方法，观察齿状回BrdU阳性细胞数的变化。结果次声作用结束后第1d，齿状回BrdU阳性细胞数与假次声组和正常对照组相比均无统计学差异；第3d及第7d，BrdU阳性细胞数减少（P〈0．05），第14d恢复正常水平。结论8Hz、130dB次声可抑制正常成年大鼠海马神经前体细胞增殖，可能与次声引起大鼠脑内微环境改变有关。     

基于文献计量方法的神经干细胞研究现状分析

目的 分析国际神经干细胞研究领域的研究现状和研究热点.方法 通过科学引文索引数据库,应用文献计量方法,分别从文献外部特征和文献内容特征对1991-2011年的3389篇关于神经干细胞研究的文献进行统计学分析,主要分析国际神经干细胞研究的时间分布、国家分布、机构分布、基金来源,重点分析目前神经干细胞研究文献中的热点主题词.结果 神经干细胞相关研究在近10年得到了快速发展,从事该研究的主要有美国、中国、日本及欧盟国家等,基础研究内容主要集中在神经干细胞增殖、分化、基因转录、基因表达方面,神经干细胞移植研究热点集中在帕金森病、脊髓损伤、阿尔茨海默病、卒中、亨延顿病等神经系统疾病的治疗方面.结论 当前国际上关于神经干细胞的研究较为热门,也取得了令人鼓舞的进展,然而要实现神经干细胞移植治疗的临床应用,还存在诸多问题有待深入研究探索.     

Wnt-1对室管膜前下区神经干细胞体外分化的影响

目的 探讨室管膜前下区(anterior subventricular zone，SVZa)神经干细胞体外分化过程中，Nestin和Wnt-1表达的变化，以及Wnt-1对SVZa神经干细胞体外分化的影响。方法以免疫荧光染色方法观察在SVZa神经干细胞体外分化过程中，Nestin和Wnt-1在不同时间点的表达水平，同时以基因转染方法增强SVZa神经干细胞Wnt-1表达，观察Nestin、Wnt-1和Mash-1的表达以及神经元分化比例的改变。结果 (1)Nestin主要表达于SVZa神经干细胞分化的早期阶段，随着细胞的分化和成熟，Nestin的表达迅速减弱。(2)SVZa神经干细胞贴壁分化2h即有Wnt-1表达，其表达高峰在细胞分化开始后12h，以后随着细胞分化的进行而迅速降低。(3)SVZa神经干细胞转染Wnt-1基因后，Nestin的表达减弱，Mash-1的表达增强，神经元的分化比例增高，Mash-1的增强与神经元分化之间有很高的一致性。结论 (1)Wnt-1表达于SVZa神经干细胞分化过程之中，在细胞分化成熟后则不表达，Wnt-1可能参与调节SVZa神经干细胞的体外分化，并可作为神经干细胞处于分化状态的标志。(2)SVZa神经干细胞转染Wnt-1后表达Mash-1增强，并更多分化为神经元，Wnt-1可能通过Mash-1途径促使SVZa神经干细胞向神经元方向分化。     

Field responses to perforant path stimulation in the rat dentate gyrus: role of corticosterone and NMDA-receptor activation

Recent studies showed that corticosterone and NMDA receptor activation suppress cell turn-over in the dentate gyrus through a common pathway, the NMDA receptor acting downstream of the corticosteroids. The present data show that in the absence of corticosteroids but not of NMDA receptor activation synaptic responses of dentate cells are reduced. The reduced synaptic responsiveness in the absence of corticosterone is therefore probably not caused by changes in cell turn-over.     

脑积水对脑室周围神经干细胞影响的实验研究

目的探讨脑积水对大鼠脑室周围神经干细胞影响。方法6wWistar大鼠70只,随机分为实验组35只,对照组35只,应用显微外科技术向枕大池内注入25％无菌高岭土混悬液0．05ml,分别在高岭土注射后3d,1w,2w,3w,4w处死动物,迅速取脑组织,测侧脑室指数,用免疫组织化学方法动态检测脑室周围Nestin阳性细胞的表达,同样方法向枕大池内注入生理盐水作为对照组。结果实验组28只大鼠成功诱发脑积水并完成实验全过程,对照组30只完成实验全过程。对照组大鼠各对应时间点,侧脑室指数基本相同,实验组大鼠脑室进行性扩大;脑室周围Nestin阳性细胞：对照组细胞数平均193±20．3个并维持,脑积水造模后3d达到最大值,为对照组308％±1％（P〈0．001）,1w脑室周围Nestin阳性细胞下降到对照组196％±1％,2w降到对照组水平210±22．4个,3w脑室周围Nestin阳性细胞几乎看不到并持续。结论脑积水引起脑室进行性扩大,脑室周围神经干细胞可能受脑室扩张机械性压迫引起缺血,缺氧影响,参与脑积水病理损害和修复过程。