Niche-independent symmetrical self-renewal of a mammalian tissue stem cell.
Niche-independent symmetrical self-renewal of a mammalian tissue stem cell.
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DOI：
10.1371/journal.pbio.0030283
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发表时间：
2005-09
期刊：
影响因子：
9.8
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中科院分区：
文献类型：
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多能小鼠胚胎干（ES）细胞在简单的单一培养中通过对称分裂繁殖。然而，在体内，干细胞通常被认为依赖于专门的细胞微环境，并进行主要的不对称分裂。组织干细胞的纯群体的离体扩增已被证明是难以实现的。神经祖细胞与分化的后代在称为神经球的漂浮簇中繁殖。然而，神经球中干细胞的比例很低，并且它们不能被直接观察或询问。在这里，我们证明了复杂的神经球环境是干细胞的维护，成纤维细胞生长因子2（FGF-2）和表皮生长因子（EGF）的组合是足够的衍生和连续扩展的神经干细胞（NS）的纯培养物的对称分裂。NS细胞首先来源于小鼠ES细胞。神经谱系诱导之后，在基础培养基中添加生长因子。在仅EGF和FGF-2存在下，所得NS细胞连续增殖，是二倍体和克隆形成的。经过长时间的扩增，它们仍然能够在体外和移植到成人大脑中后有效地分化为神经元和星形胶质细胞。从单个NS细胞产生的集落在生长因子撤除后都产生神经元。NS细胞均匀地表达放射状胶质细胞的形态学、细胞生物学和分子特征，放射状胶质细胞是神经元和胶质细胞的发育前体。与该特征一致，贴壁NS细胞系可以容易地从胎鼠脑建立。类似的NS细胞可以从人ES细胞和人胎脑产生。外源因子EGF加FGF-2足以维持NS细胞的纯对称自我更新分裂。由此产生的培养物构成了第一个已知的组织特异性干细胞的例子，它可以在不伴随分化的情况下繁殖。这些均质培养物将能够描绘定义组织特异性干细胞的分子机制，并允许与多能ES细胞进行直接比较。Austin Smith及其同事从小鼠胚胎干细胞中获得神经干细胞，并证明了它们在体外的长期繁殖。
Pluripotent mouse embryonic stem (ES) cells multiply in simple monoculture by symmetrical divisions. In vivo, however, stem cells are generally thought to depend on specialised cellular microenvironments and to undergo predominantly asymmetric divisions. Ex vivo expansion of pure populations of tissue stem cells has proven elusive. Neural progenitor cells are propagated in combination with differentiating progeny in floating clusters called neurospheres. The proportion of stem cells in neurospheres is low, however, and they cannot be directly observed or interrogated. Here we demonstrate that the complex neurosphere environment is dispensable for stem cell maintenance, and that the combination of fibroblast growth factor 2 (FGF-2) and epidermal growth factor (EGF) is sufficient for derivation and continuous expansion by symmetrical division of pure cultures of neural stem (NS) cells. NS cells were derived first from mouse ES cells. Neural lineage induction was followed by growth factor addition in basal culture media. In the presence of only EGF and FGF-2, resulting NS cells proliferate continuously, are diploid, and clonogenic. After prolonged expansion, they remain able to differentiate efficiently into neurons and astrocytes in vitro and upon transplantation into the adult brain. Colonies generated from single NS cells all produce neurons upon growth factor withdrawal. NS cells uniformly express morphological, cell biological, and molecular features of radial glia, developmental precursors of neurons and glia. Consistent with this profile, adherent NS cell lines can readily be established from foetal mouse brain. Similar NS cells can be generated from human ES cells and human foetal brain. The extrinsic factors EGF plus FGF-2 are sufficient to sustain pure symmetrical self-renewing divisions of NS cells. The resultant cultures constitute the first known example of tissue-specific stem cells that can be propagated without accompanying differentiation. These homogenous cultures will enable delineation of molecular mechanisms that define a tissue-specific stem cell and allow direct comparison with pluripotent ES cells. Austin Smith and colleagues derive neural stem cells from mouse embryonic stem cells and demonstrate their long-term propagation in vitro.