Neurturin基因转染c17.2神经干细胞移植保护帕金森病大鼠模型的实验研究

目的探讨neurturin（NTN）基因转染c17．2神经干细胞脑内移植后对帕金森病大鼠模型的保护作用。方法构建高表达NTN蛋白的NTN-c17．2细胞克隆。实验分成NTN（12只）、空质粒（Mock，9只）和PBS组（9只），分别在各组大鼠的纹状体区移植入NTN-c17．2、Mock-c17．2和PBS，16d后再注入6-羟多巴胺（6-OHDA）。通过免疫组化、原位杂交、旋转行为和神经递质变化观察c17．2神经干细胞的分化，NTN基因的表达和NTN蛋白的保护作用。结果NTN-c17．2细胞移植后，细胞分化但仍持续分泌NTN蛋白。NTN蛋白可逆向运输到黑质，保护酪氨酸羟化酶（TH）阳性神经元免受6-OHDA的损害。动物模型旋转行为动态观测显示NTN的保护作用至少持续了4个月，NTN组要明显好于Mock和PBS组。移植后10个月，NTN和Mock组动物移植侧与健侧纹状体的神经递质如多巴胺浓度比值分别为95％（P〈0．05）和93％（P〈0．05），PBS组为75％。结论用带有NTN基因的神经干细胞移植治疗帕金森病，显示出良好的保护效果。     

TrkA基因修饰、诱导神经干细胞分化为胆碱能神经元

目的研究外源性TrkaA基因修饰C17．2神经干细胞，对神经干细胞定向分化的影响。方法采用脂质体法将携带有TrkA基因的真核表达载体pcDNA3．1（＋）/TrkA转染C17．2神经干细胞，Western blot观察转染后基因表达情况；将正常生长的C17．2神经干细胞随机分成两组（A组和C组），将重组质粒转染阳性的C17．2神经干细胞随机分成两组（B组和D组），并用100ng／mg神经生长因子（NCF）分别作用于C组及D组，应用间接免疫荧光染色方法，观察各组细胞胆碱乙酰转移酶（CHAT）的表达。结果Western blot结果显示转染组TrkA蛋白表达明显高于非转染组，说明外源性TrkA基因导入靶细胞，并实现蛋白表达；间接免疫荧光染色显示，经NGF孵育的转染组细胞（D组）约有26％呈ChAT阳性，而非转染组（C组）约为9％，未经NGF孵育的A、B组未观察到CHAT阳性细胞。结论应用外源性TrkA基因修饰神经干细胞，造成TrkA基因过度表达，在NGF作用下，可以诱导更多的神经干细胞向胆碱能神经元分化。     

大鼠IL-12基因双亚基真核表达质粒的构建及表达

目的 构建双亚基共表达的大鼠白细胞介素12（rIL—12）基因真核表达载体质粒。方法 用Trizol提取大鼠腹腔巨噬细胞总RNA．RT—PCR方法分别获取rp40和rp35两个亚基的cDNA．依次克隆入pcDNA3．1（-）／myc—His A质粒中．以脊髓灰质炎病毒的内核糖体进入位点连接双亚基，构建成双顺反子真核表达载体质粒pcDNA3．1／rIL-12。用电转染法将构建的重组质粒转染大鼠胶质瘤9L细胞．G418筛选单克隆细胞株．ELISA法检测其培养上清rIL—12（p70）蛋白含量．同时抽提细胞RNA．RT—PCR方法检测rp40、rp35基因在9L/IL-12细胞中的表达。结果 所得rp40cDNA序列与GenBank NM022611和AF133197、rp35cDNA序列与GenBank NM053390和AF177031均一致，构建的质粒经PCR、酶切及测序鉴定正确。质粒转染9L细胞，获得9L／rIL-12单克隆细胞株，其培养上清rIL—12（p70）蛋白含量达139．0～162．1PG／mL．RT—PCR结果显示细胞中rIL—12基因表达阳性。结论 成功构建并鉴定了大鼠IL—12真核表达质粒pcDNA3．1／rIL—12。     

人野生型parkin基因真核表达载体的构建及其在PC12细胞中的表达

目的 克隆人野生型parkin基因并构建真核表达载体pCDNA3．1—parkin，将重组质粒转染PC12细胞获得高表达人野生型parkin基因的PC12细胞克隆。方法 从胎脑组织中提取总RNA，用RT—PCR方法获得人野生型parkin基因的全长cDNA，插入pCR2．1—TA克隆载体中进行序列测定，测序正确后将其亚克隆至表达载体pCD—NA3．1，利用脂质体将重组质粒转染PC12细胞，经G418筛选获得抗性细胞克隆，采用RT—PCR和Western Blot方法鉴定人野生型parkin基因在PC12细胞中的过表达。结果 经限制性内切酶酶切图谱分析和DNA序列测定证实目的基因已插入重组质粒，RT—PCR和Western Blot证明经G418筛选得到的转基因PC12细胞克隆中存在人野生型parkin基因的表达。结论 成功构建了人野生型parkin基因的真核表达载体，获得了稳定表达人野生型parkin基因的PC12细胞克隆，为进一步研究parkin的生物学功能以及parkin在帕金森病发病机制中的作用奠定了良好的基础。     

AADC和NURR1基因联合c17.2神经干细胞移植治疗帕金森病的实验研究

目的研究芳香族氨基酸脱羧酶(AADC)基因和NURR1基因联合c17．2神经干细胞脑内移植后对帕金森病模型大鼠的治疗效果。方法人类神经元性AADC基因和NURR1基因真核表达载体分别转染至c17．2神经干细胞内。将帕金森病(PD)模型大鼠随机分为4组,分别予以脑内毁损侧纹状区移植含空质粒的c17．2神经干细胞(A组),pCDNA3-AADC转染后的c17．2神经干细胞(B组),pCDNA3-NURR1转染后的c17．2神经干细胞(C组)以及含有pCDNA3-AADC和pCDNA3-NURR1转染后的c17．2 神经干细胞(D组)。观察其病理性旋转行为的改善,采用酪氨酸羟化酶(TH)的免疫组化方法研究脑内多巴胺含量的变化,并用荧光示踪方法观察c17．2细胞在PD模型脑内的移行。结果各组动物脑内移植后动物旋转行为较前均有改善(P<0．05),尤以D组改善最为明显,其行为学最大改善达73．7％,且同A、B、C组间差异具有显著性(P<0．05)。免疫组化可见各组移植TH阳性细胞明显增多,TH染色的神经元树突或轴突密集,体内TH阳性区域明显较PD模型组扩大,其中尤以D组病理学改善最为明显。荧光示踪观察c17．2神经干细胞有突触形成,并与临近的细胞建立突触联系。结论 AADC基因联合NURR1基因共转染c17．2神经干细胞脑内移植后改善了动物的旋转行为,增加了脑内多巴胺的表达,且植入的神经干细胞可同宿主神经元形成突触联接,为研究多基因联合神经干细胞移植治疗帕金森病提供了新方法。     

重组质粒pcDNA3.1 his-hTH与pEGFP-C2共转染骨髓基质细胞源神经干细胞的实验研究

目的 构建携带人酪氨酸羟化酶(tyrosine hydroxylase，TH)目的基因片段的真核表达重组质粒-pcDNA3．1his-hTH，与pEGFP-C2共转染恒河猴骨髓源神经干细胞，观察hTH基因在骨髓源神经干细胞中的表达情况。方法 应用基因重组技术，将pWAV2-TH中TH基因亚克隆到pcDNA3．1his真核表达载体，以酶切和测序方法鉴定重组质粒pcDNA3．1his-hTH的正确性；将pcDNA3．1his-hTH和pEGFP-C2经电击穿孔法共转染恒河猴骨髓源神经干细胞，24h后观察EGFP瞬时表达情况，10d后进行hTH基因RT-PCR，以及hTH和6His单克隆抗体的免疫组化检测。结果 (1)酶切和测序结果均证实pcDNA3．1his-hTH的正确性；(2)细胞转染24h后，荧光显微镜下可观察到EGFP的表达，80％以上细胞发出绿色荧光；10d后RT-PCR检测到细胞内有hTH基因的表达，免疫组化结果显示细胞有hTH和6His抗原表达。结论 成功构建的pcDNA3．1．his-hTH和pEGFP-C2能够共转染恒河猴骨髓源神经干细胞，hTH、EGFP和6His基因在细胞内有效表达。该系统可以作为体外检测转染率、细胞移植治疗帕金森病活体跟踪移植细胞的技术平台。     

白介素-18基因修饰人脑胶质瘤U87／hIL-18细胞的建立

目的构建人白介素18（hIL-18）基因真核表达载体质粒,建立hIL-18基因修饰并星稳定表达的人脑胶质瘤U87／hIL-18细胞。方法从人淋巴细胞cDNA文库钓取hIL-18基因后行PCR扩增,利用pcDNA3．1（＋）质粒为载体,构建hIL—18真核表达质粒pcDNA3．1／hIL-18。将构建的重组质粒转染人胶质瘤细胞U87,采用G418筛选单克隆细胞株,ELISA检测培养上清中的hIL-18蛋白含量,提取细胞RNA,RT—PCR方法检测hIL-18基因在U87／hIL-18细胞中的表达。结果所得hIL-18 cDNA序列与GeneBank比对一致,构建的质粒经PCR、酶切及测序鉴定正确。质粒转染U87细胞后,经加压筛选获得hIL-18基因稳定、高效表达的U87／hIL-18单克隆细胞株,细胞培养72h的上清中,hIL—18蛋白含量达131．2pg／ml,且RT—PCR结果显示细胞中hIL-18基因表达呈阳性。结论成功构建hIL-18真核表达质粒pcDNA3．1/hIL-18,并建立U87／hIL-18单克隆细胞株,为hIL-18基因修饰的胶质瘤疫苗研究打下了基础。     

基因修饰的神经干细胞脑内移植后TH表达和神经递质的变化

目的：探讨经TH基因修饰的神经干细胞脑内移植后，PD模型动物脑内TH表达和神经递质的变化。方法：构建pN2ATH逆转录病毒载体质粒，用PA317细胞包装，G418筛选阳性克隆，病毒上清感染神经干细胞，将神经干细胞和表达TH的神经干细胞植入PD大鼠纹状体内，观察移植后TH的表达情况以及DA和DOPAC含量变化。结果：TH基因修饰的神经干细胞移植2月内，TH在纹状体内的表达增加，纹状体DA和DOPAC含量增高，好于单纯神经干细胞移植组和对照组，但比正常水平低，结论：TH基因修饰的神经干细胞，脑内移植能增加纹状体内TH的表达以及DA和DOPAC含量，为其脑内移植治疗PD提供了理论基础。     

Neurturin基因克隆及其在Vero细胞中的表达

BACKGROUND： Transplantation of cell lines expressing neurturin （NTN） has been used to treat animal models of Parkinson＇s disease. However, gone homology between humans and rats varies greatly, so experimental results are not entirely suitable for understanding cellular transplantation in humans. OBJECTIVE： To explore expression of NTN in African green monkey kidney cells （Vero cells）; to obtain a stably NTN expressing cell line. DESIGN, TIME AND SETTING： An observation study of gone engineering and cellular biology was performed at the Institute of Medical Biology, Chinese Academy of Medical Science and Peking Union Medical College between 2005 and 2008. MATERIALS： Human embryonic hepatic tissues, expression vector pcDNA3, and Vero cells were prepared in this laboratory. Primers were synthesized by TaKaRa Biotechnology, Dalian, China; RNA extraction kit and plasmid extraction kit were purchased from Shanghai Watson Bioengineering, China; G418 and MTT were purchased through Sigma, USA; Lipofectamine2000 was a product of Invitrogen, USA; mice anti-human NTN antibody and fluorescent labeling goat anti-mouse IgG antibody were provided by Jingmei Biotech, China. METHODS： Total RNA was harvested from human embryonic hepatic tissues, and NTN cDNA was cloned by RT-PCR method, followed by subcloning into the pcDNA3 eukaryotic expression vector. The obtained pcDNA3/hNTN was stably transfected into Vero cells using Lipofectamine 2000, and stably expressing clones were selected using G418. MAIN OUTCOME MEASURES： NTN mRNA and protein expressions were respectively identified by RT-PCR and immunofluorescence. The morphology of transfected cells was observed under inverted microscopy, and the growth characteristics of those cells were determined using MTT method. RESULTS： A clonal cell line, stably expressing human NTN mRNA and protein, was obtained through stable transfection of pcDNA3/hNTN into Vero cells. The transfected Veto cells exhibited irregular morphology, rather than a spindle shape. The growth retardation phase was prolonged, but the number of cells was identical to non-transfected cells. CONCLUSION： Vero cell lines, which stably expressed human NTN protein, were obtained, and expression patterns of these cell lines were acceptable.     

Dopaminergic neuroprotection by neurturin-expressing c17.2 neural stem cells in a rat model of Parkinson's disease

Genetically engineered neural stem cell (NSC) lines are promising vectors for the treatment of regenerative diseases, especially Parkinson's disease (PD). Neurturin (NTN), a member of the glial cell line-derived neurotrophic factor-family, has been demonstrated to act specifically on mesencephalic dopaminergic neurons, suggesting its therapeutic potential for PD. Here, we have generated a NTN-secreting c17.2 NSC line and investigated the protective effect of NTN-c17.2 on PD rat models. These NTN-releasing NSCs engrafted and integrated in the host striatum with good success, gave rise to neurons, astrocytes and oligodendrocytes, and maintained stable, high-level NTN expression. In addition, inverse transfer of NTN protein into the substantia nigra (SN) was able to protect dopaminergic neurons from 6-OHDA toxicity. Observation of rotational behavior showed that the NTN group performed significantly better than the Mock group, and the protective effect of NTN lasted for at least 4 months. HPLC tests indicated that the contents of neurotransmitters (e.g. dopamine) in the corpus striatum area of the NTN-c17.2 group and the Mock-c17.2 group were significantly higher than in the PBS group, but there was no significant difference between expression in the NTN-c17.2 and Mock-c17.2 groups. Taken together, our results suggest that transplantation of NTN-secreting NSCs exerted protective on PD rat models.     

Mammalian-cell-produced neurturin (NTN) is more potent than purified Escherichia coli-produced NTN

Neurturin (NTN) is a recently identified homologue of glial-cell-line-derived neurotrophic factor. Both factors promote the survival of dopaminergic (DA) neurons. We investigated the biological activity of mammalian-cell-produced NTN versus purified Escherichia coli-produced NTN. Baby hamster kidney cells were engineered to stably secrete mature human NTN. Mammalian-cell-derived NTN enhanced the activity of embryonic DA neurons in vitro, with greater potency (maximum effect achieved in the picogram range) than purified E. coli-produced NTN. Cell-based delivery of NTN (less than 10 ng/day) was also shown to be biologically active in vivo. These results suggest that mammalian-cell-derived NTN, synthesized de novo and delivered in small quantities to the parenchyma at the target site, may be as active as much larger quantities of purified, E. coli-produced NTN, delivered by other means.     

Immortalized neural stem cells differ from nonimmortalized cortical neurospheres and cerebellar granule cell progenitors

Pluripotent neural stem cells (NSCs) have been used as replacement cells in a variety of neurological disease models. Among the many different NSCs that have been used to date, most robust results have been obtained with the immortalized neural stem cell line (C17.2) isolated from postnatal cerebellum. However, it is unclear if other NSCs isolated from different brain regions are similar in their potency as replacement therapies. To assess the properties of NSC-like C17.2 cells, we compared the properties of these cells with those reported for other NSC populations identified by a variety of different investigators using biological assays, microarray analysis, RT-PCR, and immunocytochemistry. We show that C17.2 cells differ significantly from other NSCs and cerebellar granule cell precursors, from which they were derived. In particular, they secrete additional growth factors and cytokines, express markers that distinguish them from other progenitor populations, and do not maintain karyotypic stability. Our results provide a caution on extrapolating results from C17.2 to other nonimmortalized stem cell populations and provide an explanation for some of the dramatic effects that are seen with C17.2 transplants but not with other cells. We suggest that, while C17.2 cells can illustrate many fundamental aspects of neural biology and are useful in their own right, their unique properties cannot be generalized.     

Neural stem cells constitutively secrete neurotrophic factors and promote extensive host axonal growth after spinal cord injury

Neural stem cells (NSCs) offer the potential to replace lost tissue after nervous system injury. This study investigated whether grafts of NSCs (mouse clone C17.2) could also specifically support host axonal regeneration after spinal cord injury and sought to identify mechanisms underlying such growth. In vitro, prior to grafting, C17.2 NSCs were found for the first time to naturally constitutively secrete significant quantities of several neurotrophic factors by specific ELISA, including nerve growth factor, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor. When grafted to cystic dorsal column lesions in the cervical spinal cord of adult rats, C17.2 NSCs supported extensive growth of host axons of known sensitivity to these growth factors when examined 2 weeks later. Quantitative real-time RT-PCR confirmed that grafted stem cells expressed neurotrophic factor genes in vivo. In addition, NSCs were genetically modified to produce neurotrophin-3, which significantly expanded NSC effects on host axons. Notably, overexpression of one growth factor had a reciprocal effect on expression of another factor. Thus, stem cells can promote host neural repair in part by secreting growth factors, and their regeneration-promoting activities can be modified by gene delivery.     

C57BL／6-gfp小鼠嗅球NSC培养及定位注射方法的建立

目的建立一套稳定的绿色荧光蛋白转基因小鼠（C57BL／6-gfp）嗅球神经干细胞（NSC）体外培养的方法,并初步应用于定位注射试验,为干细胞移植治疗神经性耳聋的实验研究奠定基础。方法培养C57BL／6-gfp小鼠胚胎嗅球NSC,传代并进行分化实验,鉴定后将其立体定位注射于大鼠耳蜗核。结果所培养的NSC生长良好,可稳定传代,能够分化为三种神经细胞。定位注射后可在局部见到绿色荧光阳性的细胞团。结论该方法培养的C57BL／6-gfp小鼠胚胎嗅球NSC可稳定传代并可作为荧光标记细胞进行移植试验。     

人神经干细胞的分离、克隆和动物脑内移植及转基因表达

目的分离和克隆人神经干细胞,并在体外和体内分析其生物学特征.方法我们联合采用四步法从人胚胎前脑分离制备多潜能神经干细胞,并使用重组腺病毒相关病毒载体(rAAV)将LacZ基因和胶质细胞起源的神经营养因子(GDNF)基因转移到神经干细胞.结果二株人神经干细胞被成功建立.这些克隆化后的神经干细胞在细胞培养中和移植到新生小鼠脑内后能发育分化成神经元、少枝胶质细胞和星形胶质细胞.在rAAV转导基因后,神经干细胞可在体外和体内表达转基因产物.结论这种具有转基因表达能力的神经干细胞为神经系统疾病的进一步治疗研究提供了有潜在价值的细胞资源.     

Fate of multipotent neural precursor cells transplanted into mouse retina selectively depleted of retinal ganglion cells

In some parts of the CNS, depletion of a particular class of neuron might induce changes in the microenvironment that influence the differentiation of newly grafted neural precursor cells. This hypothesis was tested in the retina by inducing apoptotic retinal ganglion cell (RGC) death in neonatal and adult female mice and examining whether intravitreally grafted male neural precursor cells (C17.2), a neural stem cell (NSC)-like clonal line, become incorporated into these selectively depleted retinae. In neonates, rapid RGC death was induced by removal of the contralateral superior colliculus (SC), in adults, delayed RGC death was induced by unilateral optic nerve (ON) transection. Cells were injected intravitreally 6-48 h after SC ablation (neonates) or 0-7 days after ON injury (adults). Cells were also injected into non-RGC depleted neonatal and adult retinae. At 4 or 8 weeks, transplanted cells were identified using a Y-chromosome marker and in situ hybridisation or by their expression of the lacZ reporter gene product Escherichia coli beta-galactosidase (beta-gal). No C17.2 cells were identified in axotomised adult-injected eyes undergoing delayed RGC apoptosis (n = 16). Donor cells were however stably integrated within the retina in 29% (15/55) of mice that received C17.2 cell injections 24 h after neonatal SC ablation; 6-31% of surviving cells were found in the RGC layer (GCL). These NSC-like cells were also present in intact retinae, but on average, there were fewer cells in GCL. In SC-ablated mice, most grafted cells did not express retinal-specific markers, although occasional donor cells in the GCL were immunopositive for beta-III tubulin, a protein highly expressed by, but not specific to, developing RGCs. Targeted rapid RGC depletion thus increased cell incorporation into the GCL, but grafted C17.2 cells did not appear to differentiate into an RGC phenotype.     

人端粒酶催化亚基基因转染大鼠颅神经嵴干细胞向永生化细胞的转变

背景：颅神经嵴干细胞可以作为颌面部各种组织和器官分化研究的重要细胞来源，如何使其获得永生化具有重要意义。人类细胞自发永生化的频率非常低，而一些永生化的基因可以显著增加这种频率。 目的：观察人端粒酶催化亚基基因在大鼠颅神经嵴干细胞永生化过程中的作用。 设计、时间及地点：观察性实验，于2007-09/2008-06在解放军第四军医大学完成。 材料：选择清洁级孕8.5 d SD大鼠3只，6周，体质量180 g；先天性细胞免疫缺陷动物雄性Balb/c裸小鼠，体质量18~21 g，均由解放军第四军医大学实验动物中心提供。质粒PCIneo-hTERT由解放军第四军医大学口腔医院牙体牙髓科提供。 方法：原代培养大鼠颅神经嵴干细胞后，将含有人端粒酶催化亚基基因的质粒PCIneo-hTERT转入大鼠颅神经嵴干细胞，经G418筛选后扩增，并连续培养。采用免疫细胞化学法观察转染细胞内人端粒酶催化亚基基因和颅神经嵴干细胞的特异标志物P75的表达，检测细胞的端粒酶活性，绘制细胞生长曲线观察其增殖能力，并通过裸鼠移植实验了解转染细胞的特性。 主要观察指标：细胞克隆、特异性蛋白P75表达、端粒酶活性、增殖能力及致瘤性实验结果。 结果：①质粒PCIneo-hTERT转染细胞后24 h，有少量细胞死亡。加G418后48 h，细胞逐步开始大量死亡。12 d后出现抗性细胞克隆，共有3个细胞克隆生长良好。分别命名为克隆1、2、3。克隆1和克隆2经过20~25代的传代后，细胞发生衰老、死亡；而克隆3在体外长期培养条件下生长状态良好，稳定表达人端粒酶催化亚基和P75。经转染后颅神经嵴干细胞的端粒酶活性明显升高，且能持续表达。②人端粒酶催化亚基基因转染后，3个细胞克隆在初期的增殖能力较强，随后克隆1、2的增殖速度逐渐变慢，出现死亡，克隆3越过衰老期，且无致瘤性。 结论：人端粒酶催化亚基基因转染大鼠颅神经嵴干细胞后，细胞得以永生化，其表型稳定，可作为颅颌面部细胞分化和组织工程研究的种子细胞。