逆转录酶抑制剂AZT对胶质瘤干细胞端粒酶活性和细胞增殖的影响

目的 探讨逆转录酶抑制剂3-叠氮-3-脱氧胸腺核苷(AZT)对脑胶质瘤干细胞增殖的影响及相关机制.方法 原代分离培养脑胶质瘤干细胞和脑胶质瘤细胞并鉴定,两种细胞同时设立为实验组(0.125 mot/L、0.250 mol/L、0.500 mol/L AZT)和对照组.MTT法检测AZT对两种细胞增殖的影响;流式细胞仪检测细胞凋亡和细胞周期的改变;端粒重复序列扩增技术-酶联免疫吸附试验(TRAP-ELISA)检测端粒酶活性的变化.结果 AZT对两组细胞的生长抑制呈浓度-时间依赖性(均P<0.05),在同一浓度和时间点,AZT对脑胶质瘤干细胞的生长抑制作用弱于脑胶质瘤细胞(均P<0.05).0.250 mol/L、0.500 mol/L AZT作用72 h后,脑胶质瘤干细胞的凋亡率分别为(4.21±1.53)%、(10.60±0.38)%,而脑胶质瘤细胞的凋亡率分别为(6.75±1.25)%,(14.30±2,59)%,明显高于胶质瘤干细胞(均P<0.05).AZT对两组细胞端粒酶活性的抑制呈浓度-时间依赖性(均P<0.05),且在同一浓度和时间点对脑胶质瘤细胞的作用明显强于脑胶质瘤干细胞(均P<0.05).结论 逆转录酶抑制剂AZT对脑胶质瘤干细胞和脑胶质瘤细胞均有明显的生长抑制作用,可能机制是通过抑制端粒酶活性、调控细胞周期和诱导细胞凋亡实现.脑胶质瘤干细胞的耐药性强于胶质瘤细胞,其机制有待进一步研究.     

三氧化二砷对人胶质瘤U251细胞生长及端粒酶活性的影响

目的探讨三氧化二砷（As2O3）对人胶质瘤U251细胞的生长及端粒酶活性的影响。方法采用倒置显微镜和透射电镜观察As2O3处理后U251细胞形态变化;四甲基偶氮唑蓝比色法观察As2O3对U251细胞增殖的影响;流式细胞术检测细胞凋亡;端粒重序列扩增酶联免疫吸附实验（TRAP-ELISA）结合聚丙烯酰胺凝胶电泳（TRAP-PAGE）银染法检测As2O3处理后U251细胞端粒酶活性变化。结果倒置显微镜下观察到：As2O3处理后的U251细胞逐渐变圆、脱壁,细胞间接触变松,细胞质中颗粒增多,增殖变慢,细胞周围碎片增多;透射电镜下见较多典型凋亡细胞。1～8μmol/LAs2O3明显抑制U251细胞增殖,诱导其凋亡;并使端粒酶活性逐渐下降,该作用呈浓度和时间依赖性。结论 As2O3对人胶质瘤U251细胞株生长具有显著抑制作用,其机制可能与As2O3能够抑制U251细胞的端粒酶活性密切相关。     

端粒、端粒酶与干细胞

摘要：端粒、端粒酶与干细胞密切相关,在维持干细胞自我更新和增殖能力中起重要作用。端粒是真核细胞染色体末端的DNA重复序列和特异结合蛋白的复合体,富含鸟嘌呤,具有保护染色体的作用,端粒长度反映细胞的复制史及复制潜能。影响端粒长度的因素包括：端粒结合蛋白、端粒帽蛋白、端粒酶及 DNA复制酶等,其中端粒酶是最主要的因素。端粒酶位于端粒末端,作用是合成端粒DNA序列,以抵消或延缓端粒随细胞分裂的不断缩短。端粒酶活性的丧失及其增殖相关基因表达的改变是造成干细胞体外复制和扩增受限的主要原因。随着组织细胞工程学的兴起,体外定向诱导干细胞分化为各种所需组织细胞已经成为研究的焦点,因此诱导和增加端粒酶的活性,维持干细胞分化、自我更新和增殖能力,延长干细胞的寿命具有重要意义。     

神经干细胞的端粒酶活性与其增殖分化的关系

目的探讨体外培养的神经干细胞端粒酶活性与细胞增殖、分化的关系,以及细胞分化后端粒酶逆转录酶的表达情况。方法采用无血清培养法从新生大鼠脑皮质分离培养神经干细胞；通过免疫荧光细胞染色鉴定神经干细胞；细胞计数法检测细胞的增殖情况；TRAP-ELISA法测定神经干细胞的端粒酶活性：RT-PCR法和Western-blot法测定细胞分化前后的端粒酶逆转录酶的表达。结果从新生大鼠脑皮质分离培养的神经干细胞具有端粒酶活性；体外培养12周内,神经干细胞的端粒酶活性未见变化,细胞的增殖速率亦未见明显不同；神经干细胞分化后端粒酶活性丧失,端粒酶逆转录酶的mRNA和蛋白质也均未见表达。结论在体外培养过程中,大鼠脑神经干细胞的端粒酶活性和细胞增殖速率未见变化；神经干细胞分化后端粒酶活性丧失,可能是由于端粒酶逆转录酶停止表达所致。     

人脑肿瘤端粒酶活性的研究

端粒是真核染色体末端的特殊结构,人端粒由6个碱基重复序列(TTAGGG)和结合蛋白组成 [1].端粒有重要的生物学功能,能够稳定染色体,防止其末端融合;保护染色体结构基因;调节正常细胞生长[2].     

脑胶质瘤端粒酶活性特征研究

目的 研究端粒酶表达是否与胶质瘤的发生及恶性程度相关。方法 采用ＴＥＬＯＭ－ＥＲＡＳＥＰＣＲ－ＥＬＩＳＡ试剂盒（ＢＭ）对６２例胶质瘤标本端粒酶活性进行检测。评价端粒酶阳性率及活性水平。结果 １５例高恶性度胶质瘤中９例阳性,１８例中度胶质瘤中有７例阳性,２５你良性胶质瘤中有６例阳性。高恶性组胶质瘤端粒酶阳性率明显高于良性组（Ｐ〈０．０５）。大多数高端粒酶活性胶质瘤是恶性胶质瘤。另外６例髓母细胞瘤中有     

脑胶质瘤端粒酶活性的表达及端粒长度的分析

目的　研究分析在不同级别脑胶质瘤细胞端粒酶活性的表达及端粒长度的变化。方法　采集 40例脑胶质瘤手术切除标本、 4例正常脑组织 ,通过半定量端粒重复序列扩增 (telomererepeatamplificationprotocol,TRAP) 银染方法检测端粒酶活性水平 ,应用人的端粒序列特异性探针32 P (CCC TAA) 3 进行Southern杂交检测脑胶质瘤细胞的端粒长度。结果　在 40例胶质瘤标本中的 33例(82 5 % )中均检出端粒酶活性 ,而在正常脑组织中无端粒酶活性的表达 ,不同级别胶质瘤之间端粒酶活性水平有明显差异 ;恶性胶质瘤细胞中端粒的长度明显比正常胶质细胞缩短 ,端粒的长度与端粒酶活性的水平有着显著的的负相关。结论　端粒酶活性可以作为脑胶质瘤的恶性标记之一 ,端粒的缩短可能是脑胶质瘤进展的重要因素 ,端粒的修复机制对于维持端粒的稳定性和肿瘤细胞的增殖潜能具有十分重要的意义     

脑膜瘤端粒酶活性检测及其RNA和hTERT的表达

目的研究脑膜瘤的端粒酶活性及其RNA和人端粒酶逆转录酶(hTERT)的表达,为临床诊断和治疗开拓新思路.方法改良TRAP法及RT-PCR检测40例脑膜瘤的端粒酶活性及其RNA和hTERT表达.结果脑膜瘤端粒酶阳性率为42.5%,hTERT阳性率52.5%,两者都随肿瘤恶性度增加而升高;人端粒酶RNA(hTR)广泛存在于脑膜瘤和正常脑组织中.结论端粒酶活性及hTERT和脑膜瘤恶性程度有关,有助于临床诊断,可能成为新治疗靶点;hTERT是端粒酶活性调节的关键.     

脑肿瘤端粒酶活性的表达及其意义的研究

目的 探讨脑肿瘤中端粒酶的表达情况,及其与恶性肿瘤发生的关系。方法 采用ＴＲＡＰ－角染法检测了３７例及肿瘤组织和４例正常脑组织中的端粒酶活性。结果 ３７例脑肿瘤组织标本中,１６例有端粒酶活性的表达,阳性率为４３．２％,４例正常脑组织中均未检测到端粒酶活性。结论 端粒酶活性的表达与脑肿瘤的恶性程度密切相关,有可能成为恶性脑肿瘤的一个重要的标志物。     

垂体腺瘤组织端粒酶活性的表达意义

目的　检测垂体腺瘤组织中的端粒酶活性及评估端粒酶与垂体腺瘤大小、侵袭性之间的关系。方法采集30例垂体腺瘤手术切除标本,均为直径大于2cm的大、巨大腺瘤,根据垂体腺瘤侵袭性标准将病例分为侵袭性和非侵袭性,采用非放射性同位素TRAP-银染方法检测肿瘤端粒酶活性。结果　大腺瘤18例中10例侵袭性,巨大腺瘤12例均为侵袭性。总共检出端粒酶活性4例,阳性率13.3％;端粒酶阳性在大腺瘤占3/18,巨大腺瘤占1/12;侵袭性垂体腺瘤阳性占4/22,非侵袭性垂体腺瘤无阳性。统计学显示端粒酶阳性率在侵袭性和非侵袭性腺瘤间无显著差异（P>0.05）,也与肿瘤大小无关（P>0.05）。结论　端粒酶活性阳性提示部分垂体腺瘤细胞非良性增殖的特点,而与垂体瘤大小、侵袭性关系不大。     

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。     

Derivation of primitive neural stem cells from human-induced pluripotent stem cells

Human-induced pluripotent stem cells (hiPSCs) have facilitated studies on organ development and differentiation into specific lineages in in vitro systems. Although numerous studies have focused on cellular differentiation into neural lineage using hPSCs, most studies have initially evaluated embryoid body (EB) formation, eventually yielding terminally differentiated neurons with limited proliferation potential. This study aimed to establish human primitive neural stem cells (pNSCs) from exogene-free hiPSCs without EB formation. To derive pNSCs, we optimized N2B27 neural differentiation medium through supplementation of two inhibitors, CHIR99021 (GSK-3 inhibitor) and PD0325901 (MEK inhibitor), and growth factors including basic fibroblast growth factor (bFGF) and human leukemia inhibitory factor (hLIF). Consequently, pNSCs were efficiently derived and cultured over a long term. pNSCs displayed differentiation potential into neurons, astrocytes, and oligodendrocytes. These early NSC types potentially promote the clinical application of hiPSCs to cure human neurological disorders.     

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.     

Changes in the proliferative activity of hippocampal neural stem cells from manganismus mice

BACKGROUND: Manganese neurotoxicity presents in the form of not only extracorticospinal tract injury of central nervous system (CNS), but also learning and memory ability damage. So, the mechanism of manganese neurotoxicity will be further studied from the angle of hippocampus. OBJECTIVE: To observe the effects of manganism on learning and memory ability and the proliferation of neural stem cells (NSCs) in hippocampus of mouse brains, and analyze whether this effect has dose-dependence. DESIGN: Randomized controlled experiment. SETTING: Department of Human Anatomy, and Department of Industrial Hygiene and Occupational Diseases, Guangxi Medical University. MATERIALS: Twenty-eight male Kunming mice, aged 2 weeks, were involved in this experiment. The involved mice were randomized into 4 groups, with 7 in each: control group, low-dose manganism group, middle-dose manganism group and high-dose manganism group. Manganese chloride was purchased from Shantou Chemicals Factory. METHODS: This experiment was carried out in the Experimental Center for Preclinical Medicine, Guangxi Medical University from November 2005 to August 2006. Mice in the low-, middle- and high-dose manganism groups were intraperitoneally injected with 5, 20 and 50 mg/kg per day manganese chloride, once a day, for 2 weeks successively. Mice in the control group were injected with the same amount of stroke-physiological saline solution. Neurobehavioral detection of all the animals was performed in Morris water maze constantly from the 7th day after the first injection of manganese chloride solution. Learning ability was detected in the place navigation test. Mice were trained for 5 consecutive days with four trials per day. The time to find the platform was latency. Memory ability was detected in spatial probe test. Platform was withdrawn on the following day of place navigation. The mice were placed in the water from a random start in the edge of the pool. The number of times they traversed the plateform's region was recorded as the performance of spatial memory. At the final two days of the water maze tests, all the animals were daily intraperitoneally injected with 50 mg/kg BrdU three times successively, once every 4 hours. At 24 hours after the final BrdU injection, all the animals were sacrificed and perfused, and their brains were harvested, fixed and successively sliced at coronary plane on a freezing microtome. Distribution and number of BrdU-positive cells in the subgranular zone of hippocampus of brains of experimental animas were detected respectively by immunohistochemistry for reflecting the proliferation of NSCs. Single-factor analysis of variance was used for comparing the difference of measurement data. Linear correlation analysis was used among the performance record in Morris water maze test, the number of BrdU-immunopositive cells and the dose of manganism. MAIN OUTCOME MEASURES: Learning and memory ability and the number of hippocampal NSCs of mice in each group. RESULTS: ①Performance of mice in Morris water maze: In the place navigation test, there was a significant retarded learning in mice of high-dose manganism group from the 3rd day as compared with control group (P < 0.01). Till the 5th day, escape latency of mice in each manganism group was prolonged, and learning performance was significantly decreased (P < 0.05), while swimming speed did not affect above results. In the spatial probe test, the average frequency of middle- and high-dose manganism groups was 1.17±1.60 and 0.80±1.10, respectively, and decreased remarkably than that of control group which was 4.86±1.35 (P < 0.01), indicating memory ability was decreased; while the average frequency of low-dose manganism group did not differ obviously from that of control group (P =0.066) although it was 2.67±3.27. The difference of swimming speed in each group was still of no statistic significance (P > 0.05). ②Effect of manganism on the number of NSCs: After counting, the average number of BrdU- immunopositive cells of one side in the control group, low-, middle- and high-dose manganism groups was 69.20±4.48, 36.63±4.50, 31.00±6.87, 26.76±4.83, individually (P < 0.01). ③Results of linear correlation analysis: The ability of spatial memory was significantly in positive correlation with the number of BrdU-labeled cells ( r =0.734, P < 0.01), and in negative correlation with the intensity of manganese poisoning (r =–0.598,P < 0.01).Meanwhile, there was a significant negative correlation between the number of BrdU-labeled cells and the intensity of manganese poisoning(r =–0.666, P < 0.01). CONCLUSION: Manganese exposure in mice can affect the ability of learning and memory, which is probably caused by the inhibition of manganese to the neurogenesis of NSCs in hippocampus in dose-dependent manner.     

神经干细胞培养条件的探讨

目的探讨体外不同培养条件对小鼠神经干细胞增殖及分化的影响.方法分别用条件培养基及10 ml·L-1、 20 ml·L-1、 30 ml·L-1、 40 ml·L-1、 50 ml·L-1、 100 ml·L-1胎牛血清 条件培养基对小鼠胚胎脑组织进行培养, 用免疫组织化学方法进行鉴定.随后对不同培养条件下、不同生长时期神经干细胞生物学特性进行光镜观察.结果 10 ml·L-1、 20 ml·L-1胎牛血清 条件培养基组培养的神经干细胞比单独条件培养基组克隆球多而大; 30 ml·L-1、 40 ml·L-1、 50 ml·L-1胎牛血清 条件培养基组既有部分贴壁细胞, 也有大量的克隆球形成, 克隆球有伪足样突起, 克隆球间存在着广泛网络结构, 且单一神经干细胞核分裂旺盛; 100 ml·L-1胎牛血清 条件培养基组以贴壁细胞为主.结论在体外不同的培养条件下神经干细胞及其神经球增殖及分化不同.     

Stem cell transplantation for treatment of cerebral ischemia in rats Effects of human umbilical cord blood stem cells and human neural stem cells

BACKGROUND:Exogenous neural stem cell transplantation promotes neural regeneration. However, various types of stem cells transplantation outcomes remain controversial. OBJECTIVE:To explore distribution, proliferation and differentiation of human neural stem cells (hNSCs) and human umbilical cord blood stem cells (hUCBSCs) following transplantation in ischemic brain tissue of rats, and to compare therapeutic outcomes between hNSCs and hUCBSCs. DESIGN, TIME AND SETTING:Randomized controlled animal studies were performed at the Experimental Animal Center of Nanjing Medical University and Central Laboratory of Second Affiliated Hospital of Nanjing Medical University of China from September 2008 to April 2009. MATERIALS:hNSCs were harvested from brain tissue of 10-13 week old fetuses following spontaneous abortion, and hUCBSCs were collected from umbilical cord blood of full-term newborns at the Second Affiliated Hospital of Nanjing Medical University of China. hNSCs and hUCBSCs were labeled by 5-bromodeoxyuridine (BrdU) prior to transplantation. METHODS:Rat models of cerebral ischemia were established by the suture method. A total of 60 healthy male Sprague Dawley rats aged 7-9 weeks were randomly assigned to hNSC transplantation, hUCBSC transplantation and control groups. The rat models in the hNSC transplantation, hUCBSC transplantation and control groups were infused with hNSC suspension, hUCBSC suspension and saline via the caudal vein, respectively. MAIN OUTCOME MEASURES:The distribution, proliferation and differentiation of hNSCs and hUCBSCs in ischemic brain tissue were observed using immunohistochemical methods. Neurological function in rats was assessed using the neurological severity score. RESULTS:The number of BrdU-positive cells was significantly greater in the hNSC transplantation group compared with hUCBSC transplantation group at 14 days following transplantation (P < 0.05). The number of BrdU-positive cells reached a peak at 28 days following transplantation. Nestin-positive, glial fibrillary acidic protein-positive, cyclic nucleotide 3' phosphohydrolase-positive and neuron specific enolase-positive cells were visible following transplantation. No significant difference was determined in the constituent ratio of various cells between hNSC and hUCBSC transplantation groups (P > 0.05). The neurological severity score was significantly decreased in rats at 21 days following transplantation (P < 0.05). No significant difference was detected in neurological severity score between hNSC and hUCBSC transplantation groups at various time points (P > 0.05). CONCLUSION:The transplanted hNSCs and hUCBSCs can migrate into ischemic brain tissue, proliferate and differentiate into neuron-like, astrocyte-like and oligodendrocyte-like cells, and improve neurological function in rats with cerebral ischemia.     

大鼠雪旺氏细胞支持人胚胎神经干细胞的生长并诱导其分化

目的 探讨大鼠雪旺氏细胞对人胚胎神经干细胞生长和分化的作用。方法 实验分为三组：组一：干细胞生长于培养雪旺氏细胞1天后的培养液中；组二：干细胞与雪旺氏细胞共培养；组三：干细胞生长于DMEM／F12培养液中，观察干细胞的形态学变化和免疫荧光的.组一的神经球分化生长，绝大多数细胞tubulin-β阳性，少数为GalC或GFAP阳性；组二中，在雪旺氏细胞生长密集和稀少的地方，干细胞分别表明为不分化和明显分化两种状态；组三的神经干细胞无法正常生长。结论 大鼠雪旺氏细胞分泌物支持人胚胎神经干细胞的生长并诱导其分化。     

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.