胚胎干细胞体外分化的研究进展

从一个受精卵发育为完整机体的过程中,具有相同基因的未分化干细胞如何产生形态和 功能各异的许多细胞?这是数十年来生物学家所一直关注的细胞分化问题。随着生命科学研究的发展,现在普遍认为细胞分化是基因差异性表达的结果,完全取决于哪些基因被激活,在什么时间和空间被激活。哺乳动物胚胎体积小,又在子宫内发育,实验研究较困难。在八十年代初,从小鼠早期胚胎的内细胞团(inner cellmass)或桑椹胚分离建立了具发育全能性的胚胎干细胞(embryonic stem cell,简称ES细     

胚胎干细胞向血液干细胞定向分化的研究进展

骨髓移植是目前治疗恶性白血病以及遗传性血液病最有效的方法之一。但是HLA相匹配的骨髓捐献者严重短缺,骨髓造血干细胞（hematopoietic stem cells,HSCs）体外培养困难,在体外修复患者骨髓造血干细胞技术不成熟,这些都大大限制了骨髓移植在临床上的应用。多能性胚胎干细胞（embryonic stem cells,ESCs）具有自我更新能力,在合适的培养条件下分化形成各种血系细胞,是造血干细胞的另一来源。在过去的二十多年里,血发生的研究是干细胞生物学中最为活跃的领域之一。小鼠及人的胚胎干细胞方面的研究最近取得了重大进展。这篇综述总结了近年来从胚胎干细胞获得造血干细胞的成就,以及在安全和技术上的障碍。胚胎干细胞诱导生成可移植性血干细胞的研究能够使我们更好地了解正常和异常造血发生的机制,同时也为造血干细胞的临床应用提供理论和实验依据。     

猕猴胚胎干细胞的诱导分化和凋亡

采用单层培养法研究维生素A酸(RA)、神经生长因子(NGF)、上皮生长因子(EGF)和碱性成纤维生长因子(bFGF)对猕猴胚胎干细胞系R366．4的诱导分化和凋亡的作用。结果表明：①不添加任何生长因子的条件下,细胞分化不定向,各种细胞所占的比例表现出明显的随机性;②添加单一生长因子能促进细胞的分化进程,并使某一类或某几类的分化细胞比例上升,RA和NGF均能促进神经样细胞的形成,EGF促进内皮样细胞的形成,bFGF提高成纤维样细胞的比例;③在分化的过程中伴有细胞早期和晚期凋亡的发生,RA和NGF可增加细胞凋亡的数量。这种由生长因子诱导的动物胚胎干细胞的分化可能存在种间差异。     

胚胎干细胞诱导分化的研究进展

胚胎干细胞(embryonic stem cell,ESC)因其具有自我更新能力和发育的多能性,成为当前医学研究的热点。ESC不但可以自发分化,而且在诱导因素作用下可以定向分化为某一种特定的成熟细胞。因此,ESC在移植医学、发育生物学等领域有着广阔的应用前景。本文对几种定向诱导ESC分化的策略进行了综述。     

人胚胎干细胞向滋养层分化的研究进展

哺乳动物胚胎发育产生的第一个细胞系的分离是内细胞团和滋养层的分离,不同哺乳动物之间胚胎干细胞向滋养层细胞分化不同,滋养层细胞对胚胎的植入、促进胚胎在子宫内的生存和生长至关重要.人胚胎干细胞为研究人类胚胎发育及向滋养层分化提供了一个独特的模型.人胚胎干细胞可以在实验室条件下保持无限期稳定的培养,用于最初胚胎和滋养外胚层发生的机制研究.目前人胚胎干细胞分化为滋养层细胞在体外可以通过自发分化、基因敲除、分离EB小体和BMP4诱导等几种途径实现.不同哺乳动物之间胚胎干细胞向滋养层分化机制,主要通过信号通路如BMP4,LIF等以及某些标志基因如OCT4,CDX2,Eomes等的变化调节.人胚胎干细胞向滋养层分化的研究为临床应用提供了一定的基础.     

胚胎干细胞向胰岛素分泌细胞定向分化的研究进展

I型糖尿病是胰岛β细胞破环的自身免疫性疾病.I型糖尿病胰岛移植是治疗I型糖尿病的有效方法.胚胎干细胞能够分化为包括胰岛素分泌细胞在内的多种细胞类型.胚胎干细胞是治疗I型糖尿病的潜在来源.综述了近年来胚胎干细胞分化为胰岛素分泌细胞的研究进展,主要阐述了胰腺发育的转录因子和不同的分化方法.     

胚胎干细胞分化为肝细胞的研究进展

目前 ,细胞移植作为终末期肝病的辅助治疗方法 ,移植的细胞必须满足在受体肝脏中存活、增殖并可分化为成熟肝细胞两个重要条件 ,但目前应用的肝细胞来源有限 ,其功能随着培养时间的延长而逐渐下降等问题限制了这一治疗策略的广泛开展。作为具有发育全能性和无限增殖能力的细胞 ,胚胎干细胞向肝细胞的分化研究近年来引起了广泛的关注 ,并取得了较大的进展 ,寻找合适、高效的分化诱导方法是目前研究的热点之一。胚胎干细胞向肝细胞的分化研究既可以为临床细胞替代治疗提供合适的细胞来源 ,也可以在药物评估和肝脏发育分化基础研究方面起到重要的作用。通过概括肝脏和拟胚体分化发育的分子机制 ,对体外胚胎干细胞向肝细胞分化的几种诱导体系作了介绍 ,并对分化肝细胞的应用前景和存在的问题进行了讨论。     

动物胚胎干细胞诱导分化的研究进展

胚胎干细胞 (ES细胞 )是从动物早期胚胎的内细胞团或原始生殖细胞分离出来的具有发育全能性的一种未分化的无限增殖细胞系 ,ES细胞能体外诱导分化为神经细胞、肌肉细胞、成纤维细胞等各种细胞。综述了动物的ES细胞的分化诱导机理及目前体外诱导分化的研究现状     

胚胎干细胞体外分化为造血干细胞

造血干细胞移植已成为治疗白血病、再生障碍性贫血、重症免疫缺陷征、地中海贫血、急性放射病、某些恶性实体瘤和淋巴瘤等造血及免疫系统功能障碍性疾病的成熟技术和重要手段,另外这一技术还被尝试用于治疗艾滋病,已取得积极的效果。但是由于移植需要配型相同的供体,并且过程复杂,使得造血干细胞移植因缺少配型相同的供体来源以及费用昂贵而不能被广泛应用。胚胎干细胞是一种能够在体外保持未分化状态并且能进行无限增殖的细胞,在适合条件下能够分化为体内各种类型的细胞,研究胚胎干细胞分化为造血干细胞,不仅可作为研究动物的早期造血发生的模型,而且可以增加造血干细胞的来源,还可以通过基因剔除、治疗性克隆等方法来解决移植排斥的问题,从而为造血干细胞移植的发展扫除了障碍,因此有着重要的研究价值和应用前景。现对胚胎干细胞体外分化为造血干细胞的诱导方法,诱导过程中的调控机制,并对胚胎干细胞分化为造血干细胞的存在问题和发展前景进行讨论。     

胚胎干细胞体外分化心肌细胞的研究

胚胎干细胞是从动物胚胎内细胞团分离的具有全能性的细胞.研究证明分离的小鼠胚胎干细胞在体外可以分化成心肌细胞,这一发现为小鼠胚胎干细胞向各种特化心脏细胞(动脉样细胞、血管样细胞、窦样细胞、心室样细胞、蒲肯野氏样细胞)分化提供了依据,使基因功能的研究在体外成为可能.1998年末人类ES细胞的成功培养奠定了心脏细胞的再生性治疗的战略基础.主要综述了目前ES细胞体外分化心肌细胞的进程,讨论了此进程对心脏基因研究的促进作用.     

Progress in studies on the induction and differentiation of embryonic stem cells

Embryonic stem cells (ESCs), which are isolated from the inner cell mass of the blastocyst stage embryo, have the potential to give rise to an entire organism and to generate every body cell type. Much improvement has been made in the field of induction and differentiation of ESCs during the last two years, such as the ESCs differentiation into germ cells (2003) and the cloning of human ESCs (2004), both of which were chosen respectively as one of the top ten achievements evaluated by academic journals. Great attention was also paid to the research of the new genes which could maintain ESCs in the undifferentiated state and the research of the induction and differentiation of ESCs.     

Progress in studies on the induction and differentiation of embryonic stem cells

Embryonic stem cells (ESCs), which are isolated from the inner cell mass of the blastocysts, have the potential to give rise to an entire organism and to gen-erate every body cell type. During the last two years, much progress has been made in ESCs field, espe-cially in the induction and differentiation of ESCs. 1 ESCs differentiate into cells of different types 1.1 ESCs differentiate into germ cells In 2003, it was reported that mouse ESCs could differentiate into oocyte[1]. Oct-4 was …     

Neural differentiation of human embryonic stem cells

Availability of human embryonic stem cells (hESC) has enhanced human neural differentiation research. The derivation of neural progenitor (NP) cells from hESC facilitates the interrogation of human embryonic development through the generation of neuronal subtypes and supporting glial cells. These cells will likely lead to novel drug screening and cell therapy uses. This review will discuss the current status of derivation, maintenance and further differentiation of NP cells with special emphasis on the cellular signaling involved in these processes. The derivation process affects the yield and homogeneity of the NP cells. Then when exposed to the correct environmental signaling cues, NP cells can follow a unique and robust temporal cell differentiation process forming numerous phenotypes.     

胚胎干细胞诱导分化为雄性生殖细胞的研究进展

胚胎干细胞（embryonic stem cells,ES细胞）具有自我更新及无限分化潜能,理论上可以分化为生殖细胞。目前,在人及鼠中已有体外诱导ES细胞分化为成熟精子的报道。系统阐述影响ES细胞分化为雄性生殖细胞的内源性及外源性因素,并结合国内外最新研究进展总结其诱导分化方法,展望应用前景,期望为从事相关研究的学者提供参考。     

Supplementation-dependent differences in the rates of embryonic stem cell self-renewal, differentiation, and apoptosis

Although it is known that leukemia inhibitory factor (LIF) supports the derivation and expansion of murine embryonic stem (ES) cells, it is unclear whether this is due to inhibitory effects of LIF on ES cell differentiation or stimulatory effects on ES cell survival and proliferation. Using an ES cell line transgenic for green fluorescent protein (GFP) expression under control of the Oct4 promoter, we were able to simultaneously track the responses of live Oct4-GFP-positive (ES) and -negative (differentiated) fractions to LIF, serum, and other growth factors. Our findings show that, in addition to inhibiting differentiation of undifferentiated cells, the administration of LIF resulted in a distinct dose-dependent survival and proliferation advantage, thus enabling the long-term propagation of undifferentiated cells. Competitive responses from the differentiated cell fraction could only be elicited upon addition of serum, fibroblast growth factor-4 (FGF-4), or insulin-like growth factor-1 (IGF-1). The growth factors did not induce additional differentiation of ES cells, but rather they significantly improved the proliferation of already differentiated cells. Our analyses show that, by adjusting culture conditions, including the type and amount of growth factors or cytokines present, the frequency of media exchange, and the presence or absence of serum, we could selectively and specifically alter the survival, proliferation, and differentiation dynamics of the two subpopulations, and thus effectively control population outputs. Our findings therefore have important applications in engineering stem cell culture systems to predictably generate desired stem cells or their derivatives for various regenerative therapies.     

Promoting human embryonic stem cell renewal or differentiation by modulating Wnt signal and culture conditions

We previously showed that Wnt3a could stimulate human embryonic stem （hES） cell proliferation and affect cell fate determination. In the absence of feeder cell--derived factors, hES cells cultured under a feeder-free condition survived and proliferated poorly. Adding recombinant Wnt3a in the absence of feeder cell derived-factors stimulated hES cell proliferation but also differentiation. In the present study, we further extended our analysis to other Wnt ligands such as Wntl and Wnt5a. While Wntl displayed a similar effect on hES cells as Wnt3a, Wnt5a had little effect in this system. Wnt3a and Wntl enhanced proliferation of undifferentiated hES cells when feeder-derived self-renewal factors and bFGF are also present. To explore the possibility to promote the proliferation of undifferentiated hES cells by activating the Wnt signaling, we overexpressed Wnt3a or Wntl gene in immortalized human adult fibroblast （HAFi） cells that are superior in supporting long-term growth of undifferentiated hES cells than primary mouse embryonic fibroblasts. HAFi cells with or without a Wnt tmnsgene can be propagated indefinitely. Over-expression of the Wnt3a gene significantly enhanced the ability of HAFi feeder cells to support the undifferentiated growth of 3 different hES cell lines we tested. Co-expression of three commonly-used drug selection genes in Wnt3a-overpressing HAFi cells further enabled us to select rare hES clones after stable transfection or transduction. These immortalized engineered feeder cells （W3R） that co-express growth-promoting genes such as Wnt3a and three drug selection genes should empower us to efficiently make genetic modified hES cell lines for basic and translational research.     

The cellular form of the prion protein guides the differentiation of human embryonic stem cells into neuron-, oligodendrocyte-, and astrocyte-committed lineages

Prion protein, PrP^C, is a glycoprotein that is expressed on the cell surface beginning with the early stages of embryonic stem cell differentiation. Previously, we showed that ectopic expression of PrP^C in human embryonic stem cells (hESCs) triggered differentiation toward endodermal, mesodermal, and ectodermal lineages, whereas silencing of PrP^C suppressed differentiation toward ectodermal but not endodermal or mesodermal lineages. Considering that PrP^C might be involved in controlling the balance between cells of different lineages, the current study was designed to test whether PrP^C controls differentiation of hESCs into cells of neuron-, oligodendrocyte-, and astrocyte-committed lineages. PrP^C was silenced in hESCs cultured under three sets of conditions that were previously shown to induce hESCs differentiation into predominantly neuron-, oligodendrocyte-, and astrocyte-committed lineages. We found that silencing of PrP^C suppressed differentiation toward all three lineages. Similar results were observed in all three protocols, arguing that the effect of PrP^C was independent of differentiation conditions employed. Moreover, switching PrP^C expression during a differentiation time course revealed that silencing PrP^C expression during the very initial stage that corresponds to embryonic bodies has a more significant impact than silencing at later stages of differentiation. The current work illustrates that PrP^C controls differentiation of hESCs toward neuron-, oligodendrocyte-, and astrocyte-committed lineages and is likely involved at the stage of uncommitted neural progenitor cells rather than lineage-committed neural progenitors.