神经干细胞与脑胶质瘤干细胞☆

所有的肿瘤组织并不是由均一的肿瘤细胞所组成的,不同的细胞具有不同的增殖、浸润和转移能力,亦即肿瘤的异质性。其中存在少数担当着干细胞角色的肿瘤细胞,具有干细胞的基本特性,包括自我更新能力、无限的增殖能力和多向分化潜能,为肿瘤干细胞。神经干细胞具有很强的自我更新机制,获得较少突变即有可能恶性转化,而且干细胞存活时间较长,这意味着干细胞比成熟细胞发生细胞复制的错误几率更大,因外界环境的刺激而发生突变的机会更多,最终形成脑胶质瘤干细胞,同时调节神经干细胞增殖和自我更新的基因在脑胶质瘤的脑胶质瘤干细胞中也表达,这也是支持神经干细胞是脑胶质瘤干细胞来源的;也有推测认为它可能起源于已分化的细胞,由这些细胞突变发生去分化得来,并通过基因突变而获得了干细胞自我更新的特性,从而形成脑胶质瘤干细胞。通过探讨神经干细胞与脑胶质瘤干细胞,为脑胶质瘤的治疗提供依据。     

利用C6胶质瘤干细胞立体定向建立大鼠脑胶质瘤模型

目的利用C6胶质瘤干细胞建立wistar大鼠脑胶质瘤模型,观察肿瘤生长规律及病理特征,探讨利用肿瘤干细胞构建模型的优势。方法体外提取并培养c6细胞系中胶质瘤干细胞,应用立体定向法在鼠脑右侧尾状核区接种10^4个胶质瘤干细胞,术后连续观察大鼠生存状态和生存时间,分时段行鼠脑MRI检查、病理HE切片及GFAP免疫组织化学检查,观察肿瘤生长及病理特征。结果利用本方法建立模型成瘤率为100％,术后大鼠恢复快,术后反应轻,未见颅外转移,生存期稳定,重复性好,肿瘤生长规律、影像学特征及组织病理特点与人脑胶质瘤相似。结论利用胶质瘤干细胞建立的大鼠脑胶质瘤模型稳定可靠,肿瘤生长更贴近胶质瘤在脑内自然发生的特点,且较传统方法脑内注射体积小,模型制作时间短,术后恢复快,成瘤率更高等优点,为研究胶质瘤干细胞在肿瘤形成过程中的生长方式、分子机制及实验性治疗提供了一个较为理想的模型。     

CD133:脑胶质瘤干细胞标志物?

过去十五年,癌症研究中的重大进展之一为"肿瘤干细胞"模式的提出.该模式认为,恶性肿瘤的发生类似于正常组织发生,最初起源于与"正常干细胞"具有相类似的自我更新和多向分化潜能特性的"肿瘤干细胞"[1].细胞表面分子CD133在各类肿瘤干细胞的分选及鉴定中广泛应用[2].然而最近,CD133分子在脑胶质瘤、结直肠癌、肺癌等恶性肿瘤组织中作为肿瘤干细胞标志物的作用受到了质疑,例如,在脑胶质瘤中的研究表明,CD133阴性的肿瘤细胞在体外实验中也可具备自我更新及多向分化能力,在免疫缺陷鼠中亦可有效导致肿瘤发生;而且CD133阴性肿瘤细胞在免疫缺陷鼠中所诱发的肿瘤可包含CD133阳性肿瘤细胞[3].因此,CD133分子作为肿瘤于细胞,尤其是脑胶质瘤干细胞标志物的特异性成为当前研究的热点.     

脑胶质瘤干细胞Hedgehog信号通路研究进展

脑胶质瘤是中枢神经系统发病率和复发率最高的恶性肿瘤,因其呈浸润性生长,手术、放疗及化疗等治疗手段均难以根治。随着对神经干细胞入了解和肿瘤干细胞概念的提出,有学者成功分离出脑胶质瘤干细胞（glima stem cells,GSCs）,这为有效的治疗脑胶质瘤的研究提供了锲机,也成为神经外科领域的研究热点。Hedgehog信号通路广泛参与胚胎的发育以及多种病理生理过程。     

脑胶质瘤干细胞巢的研究进展

胶质瘤是中枢神经系统最常见的原发肿瘤,约占颅内原发肿瘤的一半.虽然胶质瘤很少发生远处转移,但是它们能侵袭性生长入正常的脑组织中,手术难以完整切除,放疗和化疗也只能延缓肿瘤的复发,不能根治肿瘤.因此,迫切需要寻求一些新的治疗方法,以提高肿瘤的疗效.目前,有些学者提出一种极具前景的治疗方法-靶向性杀伤癌症干细胞,这些干细胞样肿瘤细胞只占恶性白血病和许多实性肿瘤细胞中的一小部分,但在疾病的实验模型中它们是引起肿瘤侵袭、增殖、转移、耐药及复发等的独立因素[1].     

免疫磁珠法分离、培养人脑胶质瘤干细胞

目的建立免疫磁珠法分离，并培养人脑胶质瘤干细胞的方法。方法将术中取得的脑胶质瘤标本，通过剪切、消化和吹打成单细胞悬液，筛网过滤，免疫磁珠分选试剂盒分选出CD133^＋细胞，用神经干细胞无血清培养法培养出具有单细胞克隆能力的细胞球，取第3代进行诱导分化，分化前后用免疫细胞荧光化学方法鉴定肿瘤干细胞及分化后细胞。结果免疫磁珠分选出的CD133^＋细胞，可悬浮生长并形成神经干细胞样细胞球，有较强的增殖能力，干细胞标志物巢蛋白（nestin）阳性，分化后细胞表达神经元小管相关蛋白β-3（β-tubulin3）和星形胶质细胞胶质纤维酸性蛋白质（GFAP）特异性抗原，而巢蛋白、CD133^＋阴性，并具有肿瘤的核型。结论免疫磁珠分选法可避免原代培养中众多细胞混杂生长的发生，能够从大量肿瘤细胞中分离出只占极少比例的肿瘤干细胞，细胞结合磁珠后在体外可以长期培养和传代，进一步证实了肿瘤干细胞的存在，并为胶质瘤干细胞的研究奠定基础。     

人脑胶质瘤中肿瘤干细胞的体外培养及生物学特性

背景：有研究者提出，脑内存在少量正常的神经干细胞能够向肿瘤组织迁移。这需要对从胶质瘤体外培养得到的肿瘤干细胞与正常的神经干细胞进行鉴别。 目的：从人脑胶质瘤组织中分离脑胶质瘤干细胞进行体外培养，并对其干细胞特性加以鉴定，观察脑肿瘤干细胞的生长特性。 设计、时间及地点：细胞学观察实验，于2007-02/12在解放军第四军医大学细胞工程研究中心完成。 材料：7份肿瘤标本来源于胶质瘤患者，间变性星形细胞瘤标本3份，多形性胶质母细胞瘤标本4份。 方法：将获取的胶质瘤细胞置于含2%B27、表皮细胞生长因子、碱性成纤维细胞生长因子、左旋谷胺酰氨、胰岛素、青霉素和链霉素生长因子的无血清DMEM/F12培养基中，重新悬浮为单细胞悬液，以1×108 L-1接种于含有B27、表皮细胞生长因子及碱性成纤维细胞生长因子的DMEM/F12培养基中培养分离培养肿瘤干细胞球。取第5代的肿瘤干细胞球，离心后除去原培养基，用含有体积分数为0.10胎牛血清的DMEM/F12培养基接种于放置有多聚赖氨酸包被盖玻片的小平皿中，观察肿瘤干细胞分化情况。 主要观察指标：利用细胞免疫荧光及组织免疫组织化学法检测脑肿瘤干细胞在细胞培养或组织切片中CD133及巢蛋白表达。 结果：在胶质瘤中存在一定量的细胞能在无血清培养基中存活并悬浮生长，并增殖形成克隆性脑肿瘤干细胞球，细胞核较大，核质比例高，具有肿瘤细胞的特性，与原肿瘤组织标本的苏木精-伊红染色比较，肿瘤干细胞分化后的子代细胞中大部分与胶质瘤细胞相似。原代及传代脑肿瘤干细胞表达神经干细胞的特异性标志物巢蛋白和CD133。 结论：人脑胶质瘤中存在一定量的肿瘤干细胞，并能在体外将其分离培养，能够自我更新增殖、诱导分化，表达神经干细胞标志物CD133。     

干细胞移植治疗脑胶质瘤的研究进展

尽管脑胶质瘤的治疗取得不断的进步，但其致残率和死亡率仍很高，其难以根除的主要原因是肿瘤细胞对脑组织的高度浸润性。传统的外科手术辅助放疗、化疗方法对正常神经组织的破坏及副作用很大，如放射性坏死、认知障碍和脑白质病等。近几年随着干细胞技术的兴起，利用干细胞作为载体的脑胶质瘤基因治疗受到广泛关注，该治疗方法的优势在于既能除去肿瘤细胞又有组织修复功能。本就干细胞治疗神经胶质瘤的细胞来源、肿瘤趋向性、治疗机理及体内监测等方面的现状及进展进行简要回顾和展望。[第一段]     

胶质瘤及肿瘤干细胞抑制剂—MicroRNA-34a

微小RNA(MicroRNA,miRNA)是一类内源性、保守、稳定的非编码短单链RNA,在转录后水平调节靶基因表达。miR-34a作为微小RNA家族一员,具有抑制多种肿瘤生长的特性,并在胶质瘤中表达下调。miR-34a能够通过多种机制抑制脑胶质瘤细胞的生长,包括抑制肿瘤细胞c-Met、Bcl-2原癌基因的表达、抑制Notch信号转导、与抑癌基因p53形成正反馈环路,达到诱导肿瘤细胞凋亡的作用。另外,miR-34a在诱导胶质瘤肿瘤干细胞分化为正常的神经细胞过程中起重要作用,因此miR-34a有可能成为恶性胶质瘤基因治疗的潜在靶点。     

室管膜下区与脑肿瘤干细胞的研究现状

脑肿瘤细胞的起源一直是学者们关注的焦点问题之一。研究发现,脑肿瘤中存在少量具有干细胞特性的细胞即脑肿瘤干细胞(brain tumor stem cells,BTSCs),它们是引发肿瘤并维持其生长的细胞来源[l]。BTSCs与神经干细胞(neural stem cells,NSCs)存在诸多相似性。成人侧脑室室管膜下区(subventricular zone,SVZ)是NSCs最集中的部位。目前,寻找胶质瘤和SVZ区的相关性以便解释脑胶质瘤的起源之谜是国内外研究的热点问题,本文将对其作以如下综述。     

Neuronal stem cells

Stem cells are self regenerating multipotential cells, found in the human brain which have the potential to differentiate into neurons, astrocytes and oligodendrocytes, and to self renew sufficiently to provide adequate number of cells in the brain. Neural stem cell grafts have been studied in a variety of animal models for various diseases like metabolic disorders, muscular dystrophies, neurodegenerative disorders, spinal cord repair, brain tumors and demyelinating disease. Stem cells may be derived from autologus, allogeneic or xenogenic sources. Histocompatibility is prerequisite for transplantation of allogeneic stem cells. Fetal tissue is the best current tissue source for human neural stem cells, however ethical issues are a major concern. Thus the prospect that stem cells could potentially be used to promote neurogenesis following injury and disease may seem attractive, yet the inherent problems associated with isolation and rejection in case of stem cells from another source, the potential to form tumors and ethical issues are the major challenges.     

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.     

Efficient production of neural stem cells and neurons from embryonic stem cells

We have developed a simple method to efficiently produce a large number of neural stem cells and neurons from mouse embryonic stem (ES) cells. When cultured in astrocyte-conditioned medium (ACM) with mitogens (FGF-2 and EGF) under free-floating conditions, colonies of undifferentiated ES cells give rise to neural stem spheres (NSSs), composed of plentiful neural stem cells. Subsequent culture of the NSSs on an adhesive substrate with mitogens results in the migration of neural stem cells onto the substrate. These cells can be expanded, preserved by freezing, and differentiated into functional neurons. Neural stem cells and neurons provided by this NSS method may be valuable as potential donor cells for neuronal transplantation and also as convenient alternatives to tissue-derived neural cells.     

体外诱导人类胚胎干细胞定向分化为神经干细胞

目的 探索一种诱导人类胚胎干细胞（hESCs）向神经干细胞（NSCs）定向分化的简单高效的方法。方法 将hESCs在细菌培养皿中以无血清培养基悬浮培养形成拟胚体，进一步将成熟拟胚体打散、贴壁培养于含有B27和noggin等成分的特定培养基中，诱导其向神经干细胞定向分化。结果 悬浮于细菌培养皿中的hESCs不贴壁，进行性长大，7～10d形成成熟拟胚体；拟胚体在特定培养基中可诱导成高纯度（约96．4％）的nestin阳性细胞（即NSCs），进一步培养，这些细胞可分化成各种成熟的神经细胞。结论 该方法诱导hESCs向NSCs定向分化较文献报道耗时更短、费用低廉且效率更高，为进行细胞移植治疗神经系统相关疾病提供了很好的种子细胞来源。     

The generation of neural stem cells: induction of neural stem cells from embryonic stem (ES) cells]

Neural stem cells are considered the ultimate lineage precursors to all neurons and glia. Despite the significance of neural stem cells in the mammalian brain development, their ontogenesis remains unclear. We have established a colony-forming embryonic stem (ES) sphere assay, where ES cells were cultured in serum-free media in the presence of leukemia inhibitory factor (LIF) to form floating spheres. LIF-dependent ES cell-derived sphere cells showed self-renewal and neural multipotentiality, cardinal features of the neural stem cell, but retained some non-neural properties and broader potential. We dabbed the cells in the ES cell-derived sphere of primitive neural stem cells. LIF-dependent sphere-forming cells were also present in the epiblast of embryonic day 5.5-7.5 mouse embryos. The generation of the in vivo primitive neural stem cell was independent of Notch signaling but the activation of Notch pathway was necessary for the transition from the primitive neural stem cell to the neural stem cell. We propose that the neural stem cell originates from the pluripotent inner cell mass/epiblast cell via the primitive neural stem cell stage under the control of Notch signaling.     

Brain tumor stem cells

The concept of brain tumor stem cells is gaining increased recognition in neuro-oncology. Until recently, the paradigm of a tumor-initiating stem cell was confined to hematopoietic malignancies where the hierarchical lineages of stem progenitor cells are well established. The demonstration of persistent stem cells and cycling progenitors in the adult brain, coupled with the expansion of the cancer stem cell concept to solid tumors, has led to the exploration of “stemness” within gliomas. Emerging data are highly suggestive of the subsistence of transformed multipotential cells within a glioma, with a subfraction of cells exhibiting increased efficiency at tumor initiation. However, data in support of true glioma stem cells are inconclusive to date, particularly with respect to functional characterization of these cells. Ongoing work aims at the identification of unique pathways governing self-renewal of these putative stem cells and at their validation as ultimate therapeutic targets.     

Quite amusing stem cells:Muse cells

<正>Stem cells may be the future of therapeutics for stroke due to their regenerative and immunomodulatory capabilities.Major barriers faced when employing stem cells,however,include faulty migration,low cell survival,and diminished proliferation.M ultilineage-differentiating stress ensuring (Muse) cells,a subset of mesenchymal stem cells,overcome these barriers.Muse cells aid in neuroregeneration,have immense regenerative potential,and are pluripotent,non-tumorigenic,and immunomodulatory.I...     

In vitro differentiation of adipose-derived stem cells and bone marrow-derived stromal stem cells into neuronal-like cells

Adipose-derived stem cells and bone marrow-derived stromal stem cells were co-cultured with untreated or Aβ1-40-treated PC12 cells, or grown in supernatant derived from untreated or Aβ1-40-treated PC12 cells. Analysis by western blot and quantitative real-time PCR showed that protein levels of Nanog, Oct4, and Sox2, and mRNA levels of miR/125a/3p were decreased, while expression of insulin-like growth factor-2 and neuron specific enolase was increased. In comparison, the generation of neuron specific enolas...     

骨髓间充质干细胞作为干细胞参与生物材料异位诱导成骨

背景：体内骨组织工程是在骨或非骨部位植入具有骨诱导活性的生物材料,利用机体作为生物反应器去构建组织工程骨,以修复骨缺损。骨移植物所具备的优良生物相容性和机械性能为骨移植开辟新的治疗途径。然而,其相关干细胞来源尚不清楚。 目的：探索骨髓间充质干细胞作为干细胞是否参与生物材料的异位诱导成骨。 方法：分离纯化雄性beagle犬的骨髓间充质干细胞。将培养至第3代骨髓间充质干细胞移植入雌性beagle犬体内,建立同种异体骨髓移植模型,同期将双相钙磷陶瓷植入受体犬竖脊肌内。6周后,获取骨构建物标本,利用原位荧光杂交技术对骨移植物Y染色体进行示踪。 结果与结论：原位荧光杂交结果显示Y染色体在骨构建物中有荧光信号表达,表明骨髓间充质干细胞可通过血液循环途径募集到异位生物材料处,形成骨组织。结果提示骨髓间充质干细胞参与生物材料异位诱导成骨,是生物材料异位诱导成骨干细胞来源之一。 关键词：双相钙磷陶瓷;骨髓间充质干细胞;骨缺损;组织工程;生物材料 doi:10.3969/j.issn.1673-8225.2010.21.005