中科院遗传发育所戴建武研究组利用3D细胞培养技术将小鼠成纤维细胞培养成具有类似于神经前体细胞的特性，而且具有分化能力。相关研究发表在近期"Biomaterials"杂志上。
2006年，山中伸弥(shinya Yamanaka)利用逆转录病毒转基因的方法实现体细胞重编程，产生诱导性多能干细胞(iPS细胞)，开创了基因调控细胞重编程的全新领域。随后大量研究表明，不同基因的联合应用可以诱导体细胞向多种类型细胞转变,如心肌细胞、神经元细胞、神经干细胞、血液祖细胞、胰岛细胞等。这些转分化研究都是通过病毒转染、整合、基因过表达等直接调控细胞内部基因网络调节细胞命运，寻找更为安全的转分化方法是重编程技术临床应用亟待解决的重要问题。
干细胞的命运不仅受到细胞内部基因网络的调控，细胞外部信号、生长方式及所处微环境的调节作用也是极为重要的。三维球状形态(或者克隆形态)与干细胞特性是密切相关的，如胚胎干细胞在滋养层上以克隆形态生长，神经干细胞以神经球的形态生长;克隆形成实验是鉴定干细胞的重要手段,干细胞分化后失去克隆样形态;多项研究也表明三维成球培养可以更好地维持干细胞的自我更新和多向分化特性。那么，三维成球培养对细胞重编程有什么影响呢?
戴建武研究组对小鼠成纤维细胞进行了三维成球培养，发现三维成球培养的小鼠成纤维细胞显著上调了Sox2基因的表达，并且获得了类似于神经前体细胞(neural progenitor cell, NPC)的特性，包括相似的细胞形态、NPC标志物的表达及自我更新能力。并具有分化为神经元、星形胶质细胞和少突胶质细胞的能力。当注射到鼠大脑海马部位后，可以存活并在体内分化为神经元、星形胶质细胞和少突胶质细胞。这些结果首次表明不依赖基因、RNA及蛋白的导入，三维成球培养可以诱导成纤维细胞发生重编程，获得神经前体细胞特性，为寻找更安全的转分化方法提供了新的思路。苏冠男,赵燕南和魏建树为共同第一作者。该项工作受到科技部重大科学研究计划和中科院干细胞与再生医学战略先导科技专项资助。
原文摘要：
Direct conversion of fibroblasts into neural progenitor-like cells by forced growth into 3D spheres on low attachment surfaces
Guannan Su,Yannan Zhao,Jianshu Wei,Zhifeng Xiao,Bing Chen,Jin Han,Lei Chen,Jian Guan,Renzhi Wang,Qun Dong,Jianwu Dai
Many stem cells grow into three-dimensional (3D) spheres or colonies, such as neural progenitor cells (NPCs) and embryonic stem cells (ESCs). Sphere morphology helps maintaining the stemness of stem cells. Our previous study demonstrated that forced growth of RT4 and HEK293 cells into 3D sphere on low attachment surface could induce stem cell properties. The close relationship between 3D sphere morphology and stem cell stemness drives us to hypothesize that 3D sphere formation induces fibroblasts reprogramming. The key gene Sox2 for reprogramming fibroblasts into NPCs was found to be overexpressed in 3D sphere cultured mouse fibroblasts. These cells exhibited similar morphological and molecular features to NPCs in vitro, were capable of differentiating into neurons, astrocytes and oligodendrocytes, and could generate long-term expandable neurospheres while maintaining differentiation capability. When engrafted into hippocampus of adult rat brain, the 3D sphere cells differentiated into neural cells. Thus, NPCs can be generated from fibroblasts directly through a physical approach without introducing exogenous reprogramming factors.
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