诱导性多能干细胞的研究概况

诱导性多能干细胞（induced pluripotent stem cells,iPS细胞）是通过在分化的体细胞中表达特定的几个转录因子,以诱导体细胞的重编程而获得的可不断自我更新且具有多向分化潜能的细胞。诱导性多能干细胞具有获取方便、能向各类细胞分化及无限增殖等特性。本文就诱导性多能干细胞的产生、制备技术的优化及应用前景等方面作一概述。     

体细胞重编程中miRNA的鉴定及功能研究

该研究针对非编码RNA研究中的核心科学问题,研究体细胞重编程微RNA功能及调控网络。研究的5年预期目标是:利用分子生物学、细胞生物学、生物化学和信息生物学手段,完成重编程和体细胞重编程和多能性细胞分化多个阶段的微RNA的表达谱,鉴定出在以上多个阶段表达变化显著的微RNA。找到影响重编程或多能干细胞分化过程的几种微RNA及鉴定其靶基因,并揭示这些基因在上述过程的作用。鉴定到在转录后加工水平和核质转运过程受调控的微RNA,阐明这些特定微RNA的作用机理,揭示其核质转运变化与重编程和多能性细胞分化之间的关联,阐明其分子机制。阐明上述相关微RNA在胚胎发育、细胞分化和重编程过程中的作用及其自身生物合成规律,并揭示其在器官发育中的作用。近3年,已建立体细胞重编程和多能性细胞分化及体细胞转分化的研究系统。采用核移植技术,建立了可用于研究体细胞重编程中mi RNA功能的新系统——来自孤雄囊胚的单倍体胚胎干细胞系。已经建立了研究mi RNA核质转运和转录后加工调控的研究体系。制作了mi RNA敲除小鼠。系统鉴定了体细胞重编程过程中差异表达的mi RNA。系统鉴定了体细胞向肝细胞转分化过程中显著差异表达的mi RNA。发现了RNA结合蛋白在转录后加工水平调控的特定miR NA的表达。发现在哺乳动物细胞核内存在一种读码机制,可能参与调控非编码RNA的核质转运。揭示了mi R-126在小鼠胚胎血管新生和血管完整性维持中的作用,探究了其发挥作用的分子机制。     

将人成纤维细胞直接转化为造血前体细胞

利用重编程得到的人诱导性多能干细胞分化为所需要的细胞受制于人们对世系特异性的了解程度。加拿大McMaster大学Mickie Bhatia与合作者,演示了不需要建立多能性,而是将真皮成纤维细胞直接转化为     

高糖诱导人脐血间充质干细胞向胰岛样细胞分化

目的:探讨脐血间充质干细胞向胰岛样细胞分化的潜能.方法:分离脐血有核细胞,将其置于MesencultTM培养基中进行培养,并利用贴壁法进行纯化、扩增.扩增后的脐血间充质干细胞用含体积分数5%胎牛血清的H-DMEM持续诱导.采用胰岛素免疫荧光染色对诱导后的细胞进行鉴定,定量检测胰岛素分泌水平及其对葡萄糖刺激的反应性.结果:诱导后,细胞形态发生明显变化,变圆而且聚集成团;细胞的胰岛素免疫荧光染色为阳性;而且细胞能分泌少量胰岛素,并对糖刺激具有反应性.结论:在高糖环境中,脐血间充质干细胞具有向胰岛样细胞分化的潜能.     

诱导肿瘤细胞HeLa为多能性干细胞的研究

将携带4种转录因子的逆转录病毒共同感染HeLa细胞,感染后的细胞铺到滋养层细胞MEF上培养,细胞长出类似胚胎干细胞的克隆团,这种克隆团可以扩增,并进一步诱导分化为神经元,同时免疫荧光检测细胞分化不同天数后Pax6,Sox1和βⅢ-tubulin的表达.结果表明,肿瘤细胞HeLa在Oct4、Sox2、c-Myc、Klf4等4种转录因子的作用下成功重编程为多能干细胞,同时可进一步分化为神经元.     

诱导性多能干细胞研究及应用

诱导性多能干细胞(iPS细胞)是通过向体细胞中导入Oct4,Sox2,c-myc 和 Klf4 等基因,使体细胞重编程获得具有胚胎干细胞样特性的多能干细胞.iPS细胞的产生可谓干细胞领域的新里程碑.近两年,iPS细胞的研究突飞猛进,文中结合最新的研究结果,综述了iPS细胞的研究现状、进展,如新的iPS细胞诱导方法的建立、诱导iPS细胞产生效率的提高、iPS细胞的定向诱导分化及其在疾病模型治疗中的作用等.针对iPS细胞研究领域存在的问题,包括如何提高iPS细胞生成的效率、解决其临床应用的安全性、iPS细胞重编程的机制等进行了讨论,为今后进一步开展iPS细胞的研究提供了帮助.     

代谢流分析技术及其在肿瘤代谢中的应用进展

代谢重编程是肿瘤的一大特征.研究肿瘤代谢有助于解析肿瘤的发生机制并实现个性化治疗.近年来兴起的代谢组学技术,通过全局分析内源性小分子代谢物,表征细胞、组织和体液的代谢轮廓,从而理解生理与病理变化;但稳定同位素标记的代谢流分析技术更能体现细胞代谢网络的动态变化,反映遗传或环境因素扰动下的代谢重编程规律.代谢流分析技术不仅...     

一种基于虚拟力导向和细胞分化的免疫网络分类算法

针对传统免疫网络分类算法中抗体细胞进化缺乏有效指导的问题,提出了一种基于虚拟力导向和细胞分化的免疫网络分类算法(VCAINC).算法引入虚拟力场区的概念,基于虚拟力场区定义抗体所受的虚拟作用力以指导抗体的进化过程,并根据移动收敛条件判定抗体的合理位置;对于无法达到收敛条件的抗体,采用细胞分化策略提高免疫网络的分类性能;分析了算法在UCI标准数据集的分类效果.实验结果表明,VCAINC对于多个标准数据集均具有良好的分类性能,能够有效指导抗体细胞的进化.     

胚胎干细胞向心肌细胞分化研究进展(综述)

胚胎干细胞(embryonic stem cells,ES)在体外分化培养条件下可以分化出各种组织细胞，其中包括心肌细胞。ES细胞在体外向心肌细胞分化与体内完整胚胎心肌发育过程相符合。该细胞在体外分化过程中顺序表达心肌细胞特有结构蛋白和离子通道，如肌球蛋白轻链和重链、特异性肌动蛋白、电压依赖性Ca^2 通道、K^ 通道等。ES细胞分化来源的心肌细胞具有体内心肌细胞的生理学特点，如产生的动作电位、表现自发性收缩等。因此，ES细胞是研究心肌细胞发育分化机制及鉴定其关键基因的理想模型。     

诱导性多潜能干细胞(iPS)研究：现状与展望

通过特定的基因组合与转染可以将已分化的体细胞诱导重编程为多潜能干细胞（iPS）,是近年来干细胞研究领域最令人瞩目的一项新的干细胞制造技术。与胚胎干细胞（ES）不同,iPS细胞的制造不需要毁损胚胎,因而不会涉及更多的伦理学问题。iPS的出现不仅为体细胞重编程去分化机制的研究注入了新的活力,而且为疾病发生发展相关机制研究与特异的细胞治疗,特别是再生医学带来新的曙光。目前,iPS的研究尚处于初级阶段,文章就iPS的研究现状与应用前景进行综述和展望。     

Regulatory networks define phenotypic classes of human stem cell lines

Stem cells are defined as self-renewing cell populations that can differentiate into multiple distinct cell types. However, hundreds of different human cell lines from embryonic, fetal and adult sources have been called stem cells, even though they range from pluripotent cells-typified by embryonic stem cells, which are capable of virtually unlimited proliferation and differentiation-to adult stem cell lines, which can generate a far more limited repertoire of differentiated cell types. The rapid increase in reports of new sources of stem cells and their anticipated value to regenerative medicine has highlighted the need for a general, reproducible method for classification of these cells. We report here the creation and analysis of a database of global gene expression profiles (which we call the 'stem cell matrix') that enables the classification of cultured human stem cells in the context of a wide variety of pluripotent, multipotent and differentiated cell types. Using an unsupervised clustering method to categorize a collection of approximately 150 cell samples, we discovered that pluripotent stem cell lines group together, whereas other cell types, including brain-derived neural stem cell lines, are very diverse. Using further bioinformatic analysis we uncovered a protein-protein network (PluriNet) that is shared by the pluripotent cells (embryonic stem cells, embryonal carcinomas and induced pluripotent cells). Analysis of published data showed that the PluriNet seems to be a common characteristic of pluripotent cells, including mouse embryonic stem and induced pluripotent cells and human oocytes. Our results offer a new strategy for classifying stem cells and support the idea that pluripotency and self-renewal are under tight control by specific molecular networks.     

Nanog promotes transfer of pluripotency after cell fusion

Through cell fusion, embryonic stem (ES) cells can erase the developmental programming of differentiated cell nuclei and impose pluripotency. Molecules that mediate this conversion should be identifiable in ES cells. One candidate is the variant homeodomain protein Nanog, which has the capacity to entrain undifferentiated ES cell propagation. Here we report that in fusions between ES cells and neural stem (NS) cells, increased levels of Nanog stimulate pluripotent gene activation from the somatic cell genome and enable an up to 200-fold increase in the recovery of hybrid colonies, all of which show ES cell characteristics. Nanog also improves hybrid yield when thymocytes or fibroblasts are fused to ES cells; however, fewer colonies are obtained than from ES x NS cell fusions, consistent with a hierarchical susceptibility to reprogramming among somatic cell types. Notably, for NS x ES cell fusions elevated Nanog enables primary hybrids to develop into ES cell colonies with identical frequency to homotypic ES x ES fusion products. This means that in hybrids, increased Nanog is sufficient for the NS cell epigenome to be reset completely to a state of pluripotency. We conclude that Nanog can orchestrate ES cell machinery to instate pluripotency with an efficiency of up to 100% depending on the differentiation status of the somatic cell.     

Formation of haematopoietic microenvironment and haematopoietic stem cells from single human bone marrow stem cells.

Haematopoietic stem cells are a population of cells capable both of self renewal and of differentiation into a variety of haematopoietic lineages. Enrichment techniques of human haematopoietic stem cells have used the expression of CD34, present on bone marrow progenitor cells. But most CD34+ bone marrow cells are committed to their lineage, and more recent efforts have focused on the precise characterization of the pluripotent subset of CD34+ cells. Here we report the characterization of two distinct subsets of pluripotent stem cells from human fetal bone marrow, a CD34+, HLA-DR+, CD38- subset that can differentiate into all haematopoietic lineages, and a distinct more primitive subset, that is CD34+, HLA-DR-, CD38-, that can differentiate into haematopoietic precursors and stromal cells capable of supporting the differentiation of these precursors. These data represent, to our knowledge, the first identification of a single cell capable of reconstituting the haematopoietic cells and their associated bone marrow microenvironment.     

干细胞与心肌再生

由于成年心肌细胞通常不能再生,严重的心肌损伤会导致心肌不可逆的重构坏死, 从而发生心功能失调. 干细胞再生治疗为心肌再生提供了很好的策略. 为了寻找合适的干细胞类型, 促进心肌再生, 有效改善心功能, 需要更好地了解心肌修复和再生的分子基础. 已有研究发现多种干细胞可促进心肌再生. 描述了骨髓干细胞的促血管新生及心肌分化的能力在心梗治疗中的作用, 还讨论了心脏侧群干细胞以及诱导型多能干细胞在心肌再生中的作用和分子机制. 所阐述的最新数据有利于拓展干细胞治疗的有效潜能及临床影响.     

Inhibition of pluripotential embryonic stem cell differentiation by purified polypeptides

Murine embryonic stem (ES) cells are pluripotent cell lines established directly from the early embryo which can contribute differentiated progeny to all adult tissues, including the germ-cell lineage, after re-incorporation into the normal embryo. They provide both a cellular vector for the generation of transgenic animals and a useful system for the identification of polypeptide factors controlling differentiation processes in early development. In particular, medium conditioned by Buffalo rat liver cells contains a polypeptide factor, ES cell differentiation inhibitory activity (DIA), which specifically suppresses the spontaneous differentiation of ES cells in vitro, thereby permitting their growth as homogeneous stem cell populations in the absence of heterologous feeder cells. ES cell pluripotentiality, including the ability to give rise to functional gametes, is preserved after prolonged culture in Buffalo rat liver media as a source of DIA. Here, we report that purified DIA is related in structure and function to the recently identified hematopoietic regulatory factors human interleukin for DA cells and leukaemia inhibitory factor. DIA and human interleukin DA/leukaemia inhibitory factor have thus been identified as related multifunctional regulatory factors with distinct biological activities in both early embryonic and hematopoietic stem cell systems.     

Properties and applications of embryonic stem cells

Mouse embryonic stem (ES) cells are pluripotent cells derived from the early embryo and can be propagated stably in undifferentiated state in vitro. They retain the ability to differentiate into all cell types found in the embryonic and adult body in vivo, and can be induced to differentiate into many cell types under appropriate culture conditions in vitro. Using these properties, people have set up various differentiated systems of many cell types and tissues in vitro. Through analysis of these systems, one can identify novel bioactive factors and reveal mechanisms of cell differentiation and organogenesis. ES cell-derived differentiated cells can also be applied to cell transplantation therapy. In addition, we summarized the features and potential applications of human ES cells.     

IGF and FGF cooperatively establish the regulatory stem cell niche of pluripotent human cells in vitro

Distinctive properties of stem cells are not autonomously achieved, and recent evidence points to a level of external control from the microenvironment. Here, we demonstrate that self-renewal and pluripotent properties of human embryonic stem (ES) cells depend on a dynamic interplay between human ES cells and autologously derived human ES cell fibroblast-like cells (hdFs). Human ES cells and hdFs are uniquely defined by insulin-like growth factor (IGF)- and fibroblast growth factor (FGF)-dependence. IGF 1 receptor (IGF1R) expression was exclusive to the human ES cells, whereas FGF receptor 1 (FGFR1) expression was restricted to surrounding hdFs. Blocking the IGF-II/IGF1R pathway reduced survival and clonogenicity of human ES cells, whereas inhibition of the FGF pathway indirectly caused differentiation. IGF-II is expressed by hdFs in response to FGF, and alone was sufficient in maintaining human ES cell cultures. Our study demonstrates a direct role of the IGF-II/IGF1R axis on human ES cell physiology and establishes that hdFs produced by human ES cells themselves define the stem cell niche of pluripotent human stem cells.     

诱导多能干细胞与心脏再生

诱导多能干细胞(induced pluripotent stem cells, iPSCs)研究的快速发展为心血管转化医学研究领域提供了新的策略. 诱导多能干细胞不仅具有与胚胎干细胞类似的多能性, 且巧妙地回避了胚胎干细胞面临的伦理学问题和免疫排斥反应. 心肌细胞等成体心血管细胞在发生心血管疾病后增殖能力有限, 而iPSCs 来源的心血管细胞在心脏再生治疗中颇具应用前景,是理想的细胞来源, 因此在基础医学和转化医学研究领域受到广泛关注. 就iPSCs 的发展过程及其在心脏再生中的应用作一综述, 并探讨目前iPSCs 在心脏再生临床转化中亟待解决的问题.