成年大鼠中枢神经系统脑室下带的组织学特征研究

为研究位于成年哺乳动物侧脑室外侧壁脑室下带 ( SVZ)的整体结构特征 ,本研究采用光镜观察半薄切片 ( Nissl染色 )、扫描电镜观察并结合形态计量分析技术 ,研究了侧脑室外侧壁不同部位以及内侧壁、第四脑室底壁和脊髓中央管壁的组织结构并做了相互比较。结果表明 ,仅侧脑室外侧壁存在有 SVZ,主要由具有未成熟特征的细胞组成 ,此处血管丰富。 SVZ的吻侧段明显地厚于中间段和尾侧段 ,位于吻侧段 SVZ部位的室管膜室腔面纤毛数量明显多于其他部位。本研究结果提示 ,SVZ有其独特的组织学特征 ,这种特征可能与成年动物的神经生发有关     

成年大鼠去皮层血管引起前脑室下区祖细胞增殖迁移并形成迁移路至损伤部位(一)祖细胞增殖迁移的部位在背外侧脑室下区

成年哺乳动物脑室下区(SVZ)富有神经干细胞、神经细胞祖细胞和胶质细胞祖细胞,它们能生成新的神经细胞、星状胶质细胞和少突胶质细胞。SVZ中的神经细胞祖细胞能形成切线形式的嘴侧迁移流(RMS)到嗅球,在嗅球分化成成熟的中间神经元。近年来证明成年动物实验性脑损伤和变性疾病都能引起SVZ细胞增生并能向非嗅球区迁移。本研究将成年大鼠一侧大脑皮层血管去除,15d和30d后取前脑作冠状及矢状连续切片,用BrdU和PCNA抗体显示前脑室下区正在分裂的细胞;用Tuj1抗体显示神经元祖细胞;用GFAP和vimentin抗体显示胶质细胞祖细胞。结果证明去除一侧皮层血管引起术侧及其对侧的背外侧脑室下区(dl-SVZ)的上述免疫反应阳性细胞明显增多,并向胼胝体迁移,在胼胝体内形成放射形式迁移路至损伤部位。本研究表明背外侧脑室下区的范围应包括背外侧角、外侧伸展和侧脑室上壁的SVZ,它们是切线形式和放射形式两种不同方向的迁移路祖细胞的共同源地。     

嗅球切除对成年大鼠侧脑室外侧壁神经生发活动的影响

目的研究成年大鼠嗅球切除后侧脑室外侧壁（SVZ）的形态学变化，探讨嗅球对成年大鼠SVZ神经生发活动的影响。方法建立成年SD雄性大鼠右侧嗅球切除模型，并分别存活2、4、8、12周；利用Nissl染色、多唾液酸神经细胞黏附分子（PSA—NCAM）、GFAP免疫组织化学染色的方法，分别观察成年SD大鼠嗅球切除后存活不同时间两侧SVZ的组织结构和免疫组织化学特征；计数模型动物脑两侧SVZ细胞总数及PSA-NCAM、GFAP免疫阳性细胞数，并进行统计学分析。结果嗅球切除4周后，嗅球切除侧SVZ的细胞总数增加，PSA—NCAM免疫阳性细胞数增加，但GFAP免疫阳性细胞数没有明显变化；SVZ的细胞总数及PSA-NCAM免疫阳性细胞数的增加有从SVZ嘴侧向尾侧蔓延的趋势。结论嗅球切除后在SVZ仍有新生神经元不断产生，说明SVZ的神经生发活动可能并不依赖于嗅球的存在。     

成年大鼠脑内具有神经生发功能的脑室下区的细胞形态学研究

为研究成年大鼠脑内具有神经生发功能的侧脑室外侧壁脑室下区 (SVZ)细胞的组成及特征 ,本研究对该区组织切片进行了免疫特异性反应、镀银及铅铀染色 ,在光镜和电镜下进行了观察。结果发现 ,SVZ含有能被溴脱氧尿核苷 (Brd U)标记且具有成神经细胞形态学特征的分裂后细胞 ,还有胶质纤维酸性蛋白阳性细胞和少突胶质样细胞等其他类型细胞。另外发现 ,室管膜(EL)细胞、EL深部细胞、少突胶质样细胞以及不同细胞突起所组成的网络样结构与上述 SVZ成神经样细胞紧密相邻。实验结果表明 ,SVZ成神经样细胞周围可以没有特定的胶质细胞鞘包裹 ,位于侧脑室外侧壁的不同类型细胞可能在 SVZ神经生发过程中具有不同作用。     

嗅球切除对成年大鼠侧脑室外侧壁新生细胞增殖和分化的影响

目的 研究嗅球切除后成年大鼠侧脑室外侧壁(SVZ)新生细胞增殖和分化的情况,进一步探讨嗅球对SVZ神经生发活动的影响.方法 建立成年SD雄性大鼠右侧嗅球切除模型,并分别存活4周和12周,利用Nissl染色、多唾液酸神经细胞黏附分子(PSA-NCAM)和BrdU免疫组织化学染色的方法观察了成年SD大鼠嗅球切除后存活不同时间两侧吻侧迁移流(RMS)BrdU阳性细胞数占总细胞百分比的变化以及两侧RMS PSA-NCAM阳性细胞的形态学变化.结果 1.嗅球切除后不同时间点,嗅球切除侧RMS的细胞数增加,BrdU免疫阳性细胞数增加,但BrdU免疫阳性细胞数占总细胞数的百分比随嗅球切除后大鼠存活时间的延长而下降,且以RMS的吻侧部分下降更明显;2.嗅球切除后,在切除侧断端吻侧颗粒层和RMS均出现较对照侧更多的具有较长突起的PSA-NCAM阳性细胞.结论 嗅球切除后仍有新生神经元沿RMS向吻侧迁移,但其增殖率随时间延长下调;嗅球的切除似乎并没有影响成神经细胞的分化.     

成年大鼠去皮层血管引起前脑室下区祖细胞增殖迁移并形成迁移路至损伤部位(二)来自背外侧脑室下区的祖细胞形成迁移路经胼胝体至损伤部位

近年来很多实验证明各种脑损伤和中枢神经疾病都能促进神经干细胞或祖细胞向非嗅球区域迁移,本研究将成年大鼠一侧大脑皮层血管去除,用免疫组化方法标记前脑室下区正在分裂的细胞、神经元祖细胞和胶质细胞祖细胞。结果证明:损伤侧及对侧的背外侧脑室下区各类祖细胞明显增多并向胼胝体迁移,在胼胝体内它们分别形成迁移路至损伤部位;迁移路内的各种祖细胞具有典型的不成熟的迁移细胞特点,胞体细长,一般首尾各有一突起,其引导突皆朝向损伤区。本研究结果提示去皮层血管增殖的前脑室下区神经元祖细胞和胶质细胞祖细胞通过放射状迁移路至损伤部位可能参与修复机制。     

成年哺乳动物脑内具有神经生发功能的脑室下区

成年哺乳动物脑侧脑室外侧壁的脑室下区 (SVZ)具有持续存在神经生发现象 ,表明此区存在着神经干细胞。成年神经干细胞 (adult neural stem cells)主要是指存在于成年神经系统的多能干细胞 (m ultipotent stem cells) [1 ] ,它们具有自我更新潜能 (self- renewal potential)和多向分化潜能 (m ul-tipotentiality) ,它们的子代细胞中既有与自身完全相同的细胞还有可通过非对称性分裂分化为神经元或胶质细胞的细胞。发现和分离培养以及鉴定出成年神经干细胞是近年来神经科学领域中的重大成果之一 ,它为探讨神经组织发育机制和神经组织损伤修…     

切除嗅球对成年大鼠嘴侧迁移流的影响

我们以前的研究观察到嗅球切除后室管膜下层(SVZ)仍能产生新细胞,但新细胞迁移的通路尚不清楚。为此,本研究建立了成年SD雄性大鼠右侧嗅球切除模型,利用Nissl染色、PSA-NCAM和GFAP免疫组织化学染色的方法观察了成年SD大鼠嗅球切除后存活不同时间两侧嘴侧迁移流(RMS)的形态学特征及RMS细胞的密度和单个细胞的面积,并进行统计学分析;同时利用Westernblot方法检测PSA-NCAM在RMS的表达。结果观察到:(1)嗅球切除后不同时间点,嗅球切除侧RMS的细胞数和面积增加,PSA-NCAM免疫阳性细胞数增加,而GFAP免疫阳性细胞数在嗅球切除后2周和4周有明显增加;(2)嗅球切除后两侧RMS的细胞密度和单个细胞的面积没有明显改变;(3)从矢状切片可见嗅球切除后RMS的形态和路径没有明显改变,但在切除断端细胞堆积明显。这些结果提示嗅球切除后仍有年轻神经元沿RMS向嘴侧迁移,SVZ的神经生发活动与嗅球的存在与否可能没有必然的联系。     

成年小鼠脑室下区及室周器官BrdU标记细胞的对比观察

目的:比较成年健康小鼠脑室下区及室周器官BrdU标记细胞的数量及分布,探讨生理状态下室周器官的神经生发功能。方法:成年健康BALB/c小鼠,腹腔注射BrdU(50 mg/kg),连续3 d给药。4 d后用含4%多聚甲醛的磷酸缓冲液灌注动物,取脑制备石蜡切片,免疫组织化学染色。结果:侧脑室室下区可见大量BrdU标记细胞(33.70%±1.92%),在最后区、穹窿下器及脉络丛内BrdU标记细胞分别为(2.42%±0.38%),(2.78%±0.67%)和(1.12%±0.24%),连合下器未见BrdU标记细胞。侧脑室室下区BrdU标记细胞分别与室周器官BrdU标记细胞相比较均具有显著差异(P<0.05)。最后区及穹窿下器BrdU标记细胞的数量分别与脉络丛的BrdU标记细胞的数量相比均具有显著差异(P﹤0.05)。结论:室周器官存在少量的BrdU标记细胞,这表明生理状态下成年小鼠室周器官具有一定程度的神经生发功能;但室周器官神经生发功能比室下区的神经生发功能弱的多。     

星型胶质细胞在帕金森病大鼠中脑、脑室下区的分布和体外培养分化特征

目的:观察星形胶质细胞在帕金森病(Parkinson's disease,PD)模型大鼠脑室下区、中脑的分布并进行PD模型大鼠脑室下区星形胶质细胞的体外培养、纯化和鉴定。方法:采用免疫荧光方法观察胶原纤维酸性蛋白(glial fibrillary acidic protein,GFAP)在PD模型大鼠中脑、脑室下区的表达;取PD模型大鼠侧脑室下区细胞进行体外培养、传代、贴壁分化和免疫荧光法鉴定。结果:(1)GFAP阳性细胞在PD模型大鼠中脑病侧较健侧明显增生,且GFAP荧光定量强度值在病侧较健侧明显增大(P0.05);GFAP阳性细胞在侧脑室、第三脑室和第四脑室室周区、视上核、下丘脑室旁核外侧大细胞部、正中隆起大量分布;(2)PD模型大鼠侧脑室下区培养分化的细胞具有星形胶质细胞的典型形态,其中原浆性星形胶质细胞突起粗短,分支多;纤维性星形胶质细胞突起细长,分支较少。结论:(1)星形胶质细胞在PD模型大鼠中脑和脑室下区的分布有明显区域性,可能与病侧的病理性增生相关,与相应区域的生理活动、调节功能及有关;(2)取PD模型大鼠侧脑室下区进行体外培养、分化获得星形胶质细胞的实验方法可靠。     

Short term treatment with estradiol decreases the rate of newly generated cells in the subventricular zone and main olfactory bulb of adult female mice

Adult neurogenesis occurs most notably in the subgranular zone (SGZ) of the hippocampal dentate gyrus and in the olfactory bulb (OB) where new neurons are generated from neural progenitors cells produced in the subventricular zone (SVZ) of the forebrain. As it is well known that gonadal steroid hormones, primarily estradiol, modulate neurogenesis in the hippocampus of adult female rodents, we wanted to determine whether estradiol would also affect the proliferation of progenitor cells in the SVZ and by consequence the rate of newly generated cells in the main OB. Thus a first group of adult female C57Bl6/J mice was ovariectomized and received a short term treatment with estradiol (single injection of 1 or 10 μg 17β-estradiol or Silastic capsule of estradiol during 2 days) before receiving a single injection with BrdU to determine whether estradiol would modulate the cell proliferation in the SVZ. A second group of adult ovariectomized female mice was submitted to the same estradiol treatment before receiving four BrdU injections, and was sacrificed 21 days later to determine whether a modulation in cell proliferation actually leads to a modulation in the number of newborn cells in the main OB. We observed a decrease in cell proliferation in the SVZ following either dose of estradiol compared to the controls. Furthermore, 21 days after their generation in the SVZ, the number of BrdU labeled cells was also lower in the main OB, both in the granular and periglomerular cell layers of estradiol-treated animals. These results show that a short term treatment with estradiol actually downregulates cell proliferation leading to a decreased number of newborn cells in the OB.     

BDNF control of adult SVZ neurogenesis

The sensory processing of odorants is a dynamic process that requires plasticity at multiple levels. In the olfactory bulb (OB), inhibitory interneurons undergo lifelong replacement through a process known as adult neurogenesis. These newly born cells are incorporated in a learning-dependent fashion, a process which has led some to suggest this as a primary mechanism through which the OB retains a high degree of plasticity throughout life. A continued focus of researchers in this field has been to understand the molecular mechanisms controlling adult subventricular zone (SVZ) neurogenesis and the innate functional role of these cells. Brain-derived neurotrophic factor (BDNF) has been identified as a strong candidate molecule regulating adult OB neurogenesis. We review what is known regarding the functional role of newly born cells, highlight the role of BDNF in this process, and describe preliminary findings from our lab implicating BDNF in the process of selecting of newly born cells for survival.     

Conditional ablation of Tbr2 results in abnormal development of the olfactory bulbs and subventricular zone‐rostral migratory stream

Development of the olfactory bulb (OB) is a complex process that requires contributions from several progenitor cell niches to generate neuronal diversity. Previous studies showed that Tbr2 is expressed during the generation of glutamatergic OB neurons in rodents. However, relatively little is known about the role of Tbr2 in the developing OB or in the subventricular zone‐rostral migratory stream (SVZ‐RMS) germinal niche that gives rise to many OB neurons. Results: Here, we use conditional gene ablation strategies to knockout Tbr2 during embryonic mouse olfactory bulb morphogenesis, as well as during perinatal and adult neurogenesis from the SVZ‐RMS niche, and describe the resulting phenotypes. We find that Tbr2 is important for the generation of mitral cells in the OB, and that the olfactory bulbs themselves are hypoplastic and disorganized in Tbr2 mutant mice. Furthermore, we show that the SVZ‐RMS niche is expanded and disordered following loss of Tbr2, which leads to ectopic accumulation of neuroblasts in the RMS. Lastly, we show that adult glutamatergic neurogenesis from the SVZ is impaired by loss of Tbr2. Conclusions: Tbr2 is essential for proper morphogenesis of the OB and SVZ‐RMS, and is important for the generation of multiple lineages of glutamatergic olfactory bulb neurons. Developmental Dynamics 243:440–450, 2014. © 2013 Wiley Periodicals, Inc.     

Enhanced expression of vascular endothelial growth factor receptor-3 in the subventricular zone of stroke-lesioned rats

Vascular endothelial growth factor receptor (VEGFR)-3, a receptor for VEGF-C and VEGF-D, has recently been proposed to be involved in adult hippocampal neurogenesis in response to cerebral ischemia. To identify whether VEGFR-3 is involved in poststroke neurogenesis, we investigated the temporal regulation of VEGFR-3 mRNA expression in the subventricular zone (SVZ) of rats with transient focal cerebral ischemia by in situ hybridization analysis, and identified the phenotypes of cells expressing VEGFR-3 by double- and triple-labeling techniques. In sham-operated rats, hybridization signals for VEGFR-3 mRNA were evident at a weaker intensity in the SVZ of the lateral ventricle. VEGFR-3 was transiently increased in the dorsolateral SVZ of the infarcted hemisphere on days 3–7 after reperfusion. Almost all VEGFR-3-expressing cells in the ipsilateral SVZ were colabeled with glial fibrillary acidic protein and the neural progenitor marker nestin, and were highly proliferative. In addition, a subset of VEGFR-3-labeled cells in the ipsilateral SVZ expressed the immature neuronal marker, polysialic acid-neural cell adhesion molecule. These data indicate that VEGFR-3 is upregulated in SVZ astrocytes and immature neurons after focal ischemia, suggesting that VEGFR-3 might mediate the adult neurogenesis after ischemic stroke.     

BM88/Cend1 expression levels are critical for proliferation and differentiation of subventricular zone-derived neural precursor cells

Neural stem cells remain in two areas of the adult mammalian brain, the subventricular zone (SVZ) and the dentate gyrus of the hippocampus. Ongoing neurogenesis via the SVZ-rostral migratory stream pathway maintains neuronal replacement in the olfactory bulb (OB) throughout life. The mechanisms determining how neurogenesis is restricted to only a few regions in the adult, in contrast to its more widespread location during embryogenesis, largely depend on controlling the balance between precursor cell proliferation and differentiation. BM88/Cend1 is a neuronal lineage-specific regulator implicated in cell cycle exit and differentiation of precursor cells in the embryonic neural tube. Here we investigated its role in postnatal neurogenesis. Study of in vivo BM88/Cend1 distribution revealed that it is expressed in low levels in neuronal precursors of the adult SVZ and in high levels in postmitotic OB interneurons. To assess the functional significance of BM88/Cend1 in neuronal lineage progression postnatally, we challenged its expression levels by gain- and loss-of-function approaches using lentiviral gene transfer in SVZ-derived neurospheres. We found that BM88/Cend1 overexpression decreases proliferation and favors neuronal differentiation, whereas its downregulation using new-generation RNA interference vectors yields an opposite phenotype. Our results demonstrate that BM88/Cend1 participates in cell cycle control and neuronal differentiation mechanisms during neonatal SVZ neurogenesis and becomes crucial for the transition from neuroblasts to mature neurons when reaching high levels.