bFGF在人胚胎干细胞中自我更新的研究进展

人胚胎干细胞具有自我更新和多向分化的独特生物学特性。维持人和小鼠胚胎干细胞增殖的生长因子不同,白血病抑制因子（LIF）不能维持人胚胎干细胞的生长。目前已经确定了数种维持人胚胎干细胞（hESCs）自我更新的生长因子,其中碱性成纤维细胞生长因子（bFGF）信号系统是人胚胎干细胞自我更新中最重要的调节因素之一。将从bFGF及其受体在人胚胎干细胞中的表达和作用的最新进展进行综述。     

Basic fibroblast growth factor support of human embryonic stem cell self-renewal

Human embryonic stem (ES) cells have most commonly been cultured in the presence of basic fibroblast growth factor (FGF2) either on fibroblast feeder layers or in fibroblast-conditioned medium. It has recently been reported that elevated concentrations of FGF2 permit the culture of human ES cells in the absence of fibroblasts or fibroblast-conditioned medium. Herein we compare the ability of unconditioned medium (UM) supplemented with 4, 24, 40, 80, 100, and 250 ng/ml FGF2 to sustain low-density human ES cell cultures through multiple passages. In these stringent culture conditions, 4, 24, and 40 ng/ml FGF2 failed to sustain human ES cells through three passages, but 100 ng/ml sustained human ES cells with an effectiveness comparable to conditioned medium (CM). Two human ES cell lines (H1 and H9) were maintained for up to 164 population doublings (7 and 4 months) in UM supplemented with 100 ng/ml FGF2. After prolonged culture, the cells formed teratomas when injected into severe combined immunodeficient beige mice and expressed markers characteristic of undifferentiated human ES cells. We also demonstrate that FGF2 is degraded more rapidly in UM than in CM, partly explaining the need for higher concentrations of FGF2 in UM. These results further facilitate the large-scale, routine culture of human ES cells and suggest that fibroblasts and fibro-blast-conditioned medium sustain human ES cells in part by stabilizing FGF signaling above a critical threshold.     

人胚胎成纤维细胞对人胚胎干细胞生长的作用

目的：比较人和小鼠胚胎成纤维细胞对人胚胎干细胞生长的作用,为胚胎干细胞定向诱导各系统细胞应用于临床,消除异种蛋白污染打下基础。方法：分别采用人胚胎成纤维细胞和小鼠胚胎成纤维细胞为饲养层细胞,支持人受精卵的培养,观察其增殖和分化情况。结果：人和小鼠胚胎成纤维细胞分别加入白血病抑制因子（hLIF）均能很好支持人胚胎干细胞生长增殖,并保持未分化状态。结论：完全可以使用人胚胎成纤维细胞支持人胚胎干细胞增殖,消除异种蛋白污染的可能性,为胚胎干细胞定向诱导分化发育应用于临床打下坚实基础。     

bFGF和EGF对胚胎神经干细胞分化为神经元及神经胶质细胞的影响

目的：观察碱性成纤维生长因子（bFGF）和表皮生长因子（EGF）对体外培养胚胎神经管神经干细胞生长和分化的影响。方法：从孕12天大鼠胚胎神经管分离神经干细胞，进行原代培养，分为bFGF组、EGF组、bFGF＋EGF组及对照组：培养过程中观察干细胞的生长，培养2小时做nestin染色鉴定神经干细胞，培养第5天用免疫组化方法检测培养细胞神经元特异烯醇化酶（NSE）和胶质纤维酸性蛋白（GFAP）的表达，以观察神经干细胞分化为神经元及神经胶质细胞的状况。结果：取材细胞大部分为nestin免疫阳性细胞；各实验组均可促进培养细胞的生长和分 化。免疫组化中，EGF使神经干细胞增殖成团，增加GFAP的表达（P＜0．01）；bFGF能明显增加NSE及GFAP的表达（P＜0．01）；两种因子联合应用，神经元和神经胶质细胞均比对照组增多（P＜0．01）。结论：EGF和bFGF两类生长因子均能促进胚胎神经干细胞的生长，在分化方面，EGF倾向于诱导干细胞增并向着胶质细胞分化，bFGF则诱导干细胞分 成更多的神经元。     

Basic fibroblast growth factor controls migration in human mesenchymal stem cells

Little is known about the migration of mesenchymal stem cells (MSCs). Some therapeutic approaches had demonstrated that MSCs were able to regenerate injured tissues when applied from different sites of application. This implies that MSCs are not only able to migrate but also that the direction of migration is controlled. Factors that are involved in the control of the migration of MSCs are widely unknown. The migratory ability of isolated MSCs was tested in different conditions. The migratory capability was examined using Boyden chamber assay in the presence or absence of basic fibroblast growth factor (bFGF), erythropoietin, interleukin-6, stromal cell-derived factor-beta, and vascular endothelial growth factor. bFGF in particular was able to increase the migratory activity of MSCs through activation of the Akt/protein kinase B (PKB) pathway. The results were supported by analyzing the orientation of the cytoskeleton. In the presence of a bFGF gradient, the actin filaments developed a parallelized pattern that was strongly related to the gradient. Surprisingly, the influence of bFGF was not only an attraction but also routing of MSCs. The bFGF gradient experiment showed that low concentrations of bFGF lead to an attraction of the cells, whereas higher concentrations resulted in repulsion. This ambivalent effect of bFGF provides the possibility to a purposeful routing of MSCs.     

Secreted proteoglycans directly mediate human embryonic stem cell-basic fibroblast growth factor 2 interactions critical for proliferation

Human embryonic stem (ES) cells can be maintained in an undifferentiated state if the culture medium is first conditioned on a layer of mouse embryonic fibroblast (MEF) feeder cells. Here we show that human ES cell proliferation is coordinated by MEF-secreted heparan sulfate proteoglycans (HSPG) in conditioned medium (CM). These HSPG and other heparinoids can stabilize basic fibroblast growth factor (FGF2) in unconditioned medium at levels comparable to those observed in CM. They also directly mediate binding of FGF2 to the human ES cell surface, and their removal from CM impairs proliferation. Finally, we have developed a purification scheme for MEF-secreted HSPG in CM. Using column chromatography, immunoblotting, and mass spectrometry-based proteomic analysis, we have identified multiple HSPG species in CM. The results demonstrate that HSPG are key signaling cofactors in CM-based human ES cell culture.     

Autocrine fibroblast growth factor 2 increases the multipotentiality of human adipose-derived mesenchymal stem cells

Multipotent mesenchymal stem cells (MSCs), first identified in the bone marrow, have subsequently been found in many other tissues, including fat, cartilage, muscle, and bone. Adipose tissue has been identified as an alternative to bone marrow as a source for the isolation of MSCs, as it is neither limited in volume nor as invasive in the harvesting. This study compares the multipotentiality of bone marrow-derived mesenchymal stem cells (BMSCs) with that of adipose-derived mesenchymal stem cells (AMSCs) from 12 age- and sex-matched donors. Phenotypically, the cells are very similar, with only three surface markers, CD106, CD146, and HLA-ABC, differentially expressed in the BMSCs. Although colony-forming units-fibroblastic numbers in BMSCs were higher than in AMSCs, the expression of multiple stem cell-related genes, like that of fibroblast growth factor 2 (FGF2), the Wnt pathway effectors FRAT1 and frizzled 1, and other self-renewal markers, was greater in AMSCs. Furthermore, AMSCs displayed enhanced osteogenic and adipogenic potential, whereas BMSCs formed chondrocytes more readily than AMSCs. However, by removing the effects of proliferation from the experiment, AMSCs no longer out-performed BMSCs in their ability to undergo osteogenic and adipogenic differentiation. Inhibition of the FGF2/fibroblast growth factor receptor 1 signaling pathway demonstrated that FGF2 is required for the proliferation of both AMSCs and BMSCs, yet blocking FGF2 signaling had no direct effect on osteogenic differentiation. Disclosure of potential conflicts of interest is found at the end of this article.     

胚胎干细胞关键因子Nanog在胶质瘤中的表达及意义

目的 探讨胚胎干细胞关键因子Nanog在人胶质瘤中的表达及意义。方法 通过免疫荧光双标技术,分析40例胶质瘤组织内胚胎干细胞关键因子Nanog与肿瘤干细胞相关基因Nestin、CD133及胚胎干细胞全能性相关基因Oct4 的共表达情况,并通过RT-PCR、Western blotting技术分析胶质瘤组织内Nanog与脑胶质瘤恶性程度之间的关系。结果 Nanog在胶质瘤组织中的表达随着胶质瘤病理级别增高而升高,而且超过50%的Nanog阳性细胞同时表达Nestin和CD133。95%以上的Nanog阳性细胞都同时表达胚胎干细胞全能性相关基因Oct4。结论 胶质瘤组织中Nanog多表达在肿瘤干细胞中,与胶质瘤的恶性程度呈正相关,在胶质瘤的发生、发展过程中起着重要作用,为研究胶质瘤的起源及胶质瘤的诊断和预后判断提供帮助。     

人胚胎成纤维细胞对人胚胎生殖细胞生长的作用

目的：研究人胚胎成纤维细胞对人胚胎生殖细胞（EG细胞）生长的作用。方法：采用组织块体外培养法体外培养人EG细胞,不添加任何细胞因子,利用源于胚胎组织自身的成纤维细胞作为饲养层,收集培养3d和9d的上清液,用抗体夹心ABC-ELISA法定量检测其白血病抑制因子（LIF）、干细胞生长因子（SCF）和碱性成纤维细胞生长因子（bFGF）的含量。培养的细胞用免疫细胞化学法进行SSEA-3、OCT-4的检测。结果：培养9d的上清液中3种因子均含量为LIF55．25pg／ml、SCF90．39pg／ml、bFGF26．06pg／ml．均高于培养3d相应的平均含量。培养的细胞SSEA-3、OC-4呈强阳性表达。结论：上清液中LIF、SCF和bFGF的含量与胚胎成纤维细胞的生长呈正比,胚胎成纤维细胞能分泌这些细胞因子,以维持EG细胞体外增殖并抑制其分化。     

Differentiation of human embryonic stem cells in serum-free medium reveals distinct roles for bone morphogenetic protein 4, vascular endothelial growth factor, stem cell factor, and fibroblast growth factor 2 in hematopoiesis

We have utilized a serum- and stromal cell-free "spin embryoid body (EB)" differentiation system to investigate the roles of four growth factors, bone morphogenetic protein 4 (BMP4), vascular endothelial growth factor (VEGF), stem cell factor (SCF), and basic fibroblast growth factor (FGF2), singly and in combination, on the generation of hematopoietic cells from human embryonic stem cells (HESCs). Of the four factors, only BMP4 induced expression of genes that signaled the emergence of the primitive streak-like population required for the subsequent development of hematopoietic mesoderm. In addition, BMP4 initiated the expression of genes marking hematopoietic mesoderm and supported the generation of hematopoietic progenitor cells at a low frequency. However, the appearance of robust numbers of hematopoietic colony forming cells and their mature progeny required the inclusion of VEGF. Finally, the combination of BMP4, VEGF, SCF, and FGF2 further enhanced the total yield of hematopoietic cells. These data demonstrate the utility of the serum-free spin EB system in dissecting the roles of specific growth factors required for the directed differentiation of HESCs toward the hematopoietic lineage.     

Basic fibroblast growth factor activates ERK and induces c-fos in human embryonic stem cell line MizhES1

Human embryonic stem (hES) cells can be maintained in a proliferative undifferentiated state in vitro by growing them on feeder layers of mouse embryonic fibroblast (MEF) cells along with basic fibroblast growth factor (bFGF/FGF-2). To understand the molecular mechanisms involved in the requirement of bFGF in human ES cells, we investigated expression of FGF receptors and intracellular signaling events in response to bFGF in human ES cell line MizhES1. On the basis of the results of RT-PCR, clear expression of FGF receptors FGFR1, FGR2, and FGFR3 was noticed. Because MAPK, PI3K, and PKC pathways are well-known pathways triggered by bFGF in other cells, these pathways were investigated after stimulation with bFGF. bFGF did not induce activation of PI3K or PKC, but induced activation of ERK (extracellular signal-regulated kinase). To monitor the consequences of ERK activation, we examined expression of the immediate early gene c-fos, one downstream target of the MEK1/ERK pathway. mRNA and protein levels of the c-fos gene were increased by bFGF. Induction of c-Fos was dependent on MEKl. Therefore, it is likely that bFGF contributes to maintenance of human ES cells, at least in part, through the MEK1/ERK pathway.     

Autocrine fibroblast growth factor 2 signaling is critical for self-renewal of human multipotent adipose-derived stem cells

Adipose tissue-derived stem cells offer tremendous potential for regenerative medicine. However, characterization of their self-renewal ability has not been performed yet, although it is a crucial feature for in vitro expansion of undifferentiated cells and in vivo maintenance of stem cell pools. We have undertaken the identification of molecular events that are involved in in vitro self-renewal of human multipotent adipose-derived stem (hMADS) cells from young donors, by assessing their proliferation rate, their ability to grow at the single-cell level (clonogenicity), and their differentiation potential. As hMADS cells are propagated in culture, cell morphology changes dramatically, concomitantly to a progressive decrease in proliferation, clonogenicity, and differentiation potential. This decrease is associated with a decrease in fibroblast growth factor 2 (FGF2) expression and can be circumvented by chronic treatment with exogenous FGF2. Moreover, analysis of FGF2 secretion revealed that it is exported to hMADS cell surface without being released into the culture medium, suggesting a strictly autocrine loop. Indeed, treatment of FGF2-expressing hMADS cells with PD173074, a specific FGF receptor inhibitor, decreases dramatically their clonogenicity and differentiation potential. Thus, hMADS cells express a functional autocrine FGF loop that allows maintenance of their self-renewal ability in vitro. Finally, inhibition of mitogen-activated protein kinase kinase 1 reduces the clonogenic potential of hMADS cells but does not affect their differentiation potential, indicating that the extracellular signal-related kinases 1/2 signaling pathway is partly involved in FGF2-mediated self-renewal. Together, our data clearly identify the key function of FGF2 in the maintenance of self-renewal of adipose tissue-derived stem cells.     

肝细胞生长因子促进人胚胎干细胞向神经前体细胞分化

目的:研究肝细胞生长因子(HGF)诱导人胚胎干细胞(hESCs)定向分化为神经前体细胞(NPs)的作用。方法:诱导拟胚体(EBs)生成,随机将EBs分为正常对照组、G5 supplement组、HGF组和HGF+G5 supple-ment组,悬浮培养诱导7d,转移至多聚赖氨酸/层黏连蛋白(20mg/L)包被的24孔培养板中继续培养7-10d。免疫荧光染色鉴定NPs和体外分化能力,流式细胞仪检测各组巢蛋白(nestin)阳性细胞的比例,RT-PCR检测音猥因子(Shh)对NPs的脑区标记基因表达的影响。结果:HGF+G5可诱导hESCs定向分化为NPs,HGF+G5组的nestin阳性的NPs比例(87.3%±3.9%)显著高于其它组(P0.05),NPs具有分化成神经元、少突和星形胶质细胞的能力;HGF+G5诱导时间对于NPs的分化有影响,7d时nestin+细胞比例达到最大;Shh可使NPs表达腹侧化基因,后脑标记表达上调,而前脑标记表达下调。结论:含HGF和G5的无血清神经分化体系可有效诱导hESCs神经分化,是研究神经诱导的良好体系。     

Activin A maintains self-renewal and regulates fibroblast growth factor, Wnt, and bone morphogenic protein pathways in human embryonic stem cells

Human embryonic stem cells (hESCs) self-renew indefinitely while maintaining pluripotency. The molecular mechanism underlying hESCs self-renewal and pluripotency is poorly understood. To identify the signaling pathway molecules that maintain the proliferation of hESCs, we performed a microarray analysis comparing an aneuploid H1 hESC line (named H1T) versus euploid H1 hESC line because the H1T hESC line demonstrates a self-renewal advantage while maintaining pluripotency. We find differential gene expression for the Nodal/Activin, fibroblast growth factor (FGF), Wnt, and Hedgehog (Hh) signaling pathways in the H1T line, which implicates each of these molecules in maintaining the undifferentiated state, whereas the bone morphogenic protein (BMP) and Notch pathways could promote hESCs differentiation. Experimentally, we find that Activin A is necessary and sufficient for the maintenance of self-renewal and pluripotency of hESCs and supports long-term feeder and serum-free growth of hESCs. We show that Activin A induces the expression of Oct4, Nanog, Nodal, Wnt3, basic FGF, and FGF8 and suppresses the BMP signal. Our data indicates Activin A as a key regulator in maintenance of the stemness in hESCs. This finding will help elucidate the complex signaling network that maintains the hESC phenotype and function.     

成纤维细胞生长因子2、成纤维细胞生长因子受体4蛋白在人甲状腺乳头状癌中的表达及意义

目的探讨甲状腺乳头状癌(PTC)组织中成纤维细胞生长因子2(FGF-2)和成纤维细胞生长因子受体4(FGFR-4)的表达及其是否存在相关性。方法收集89例甲状腺乳头状癌及30例癌旁正常甲状腺组织标本,采用免疫组织化学和免疫印迹法(Western blotting)检测FGF-2和FGFR-4蛋白在标本中的表达,并进行统计学分析。结果免疫组织化学方法结果显示,与癌旁正常组织相比,FGF-2及FGFR-4在人类甲状腺乳头状癌组织中均高表达(P0.01,P0.01),两者差异有统计学意义;FGF-2和FGFR-4在甲状腺乳头状癌中的表达与淋巴结转移(χ2=14.798,P0.01;χ2=7.27,P0.01)和分化程度(χ2=13.824,P0.01;χ2=16.921,P0.01)相关,而与性别、年龄、肿瘤大小无关(P0.05);通过Western blotting技术分析,FGF-2和FGFR-4癌组织中的表达明显高于正常组织,随着癌组织分化程度的降低,表达明显上调(P0.05),其结果和免疫组织化学染色的检测结果一致;并且两者在甲状腺乳头状癌中的表达呈正相关(rs=0.434,P0.01)。结论 FGF-2和FGFR-4与甲状腺乳头状癌的发生、侵袭和转移有关,两者具有正协同作用,联合检测对判断甲状腺乳头状癌的恶性程度及生物学行为是一项有意义的综合性指标。     

Anti-apoptotic effect of sphingosine-1-phosphate and platelet-derived growth factor in human embryonic stem cells

Human embryonic stem (hES) cells hold great promise for use in regenerative medicine. However, technologies first need to be established to maintain hES cells efficiently in vitro. Understanding the signaling networks involved in hES cell maintenance will prove to be essential to the development of such culture systems. Previously, we described a serum-free medium capable of supporting prolonged hES cell maintenance using sphingosine-1-phosphate (S1P) and platelet-derived growth factor (PDGF). Here, we describe an anti-apoptotic effect of S1P and PDGF in hES cells and demonstrate a direct effect of S1P in preventing hES cell apoptosis. Western blot analysis shows that S1P stimulates the phosphorylation of the mitogen-activated protein (MAP) kinases Erk1/2 but not of Akt, whereas PDGF stimulates both Erk1/2 and Akt phosphorylation. Moreover, our study suggests that the Erk1/2 and PI3K/Akt signaling pathways act independently of each other. Furthermore, neither S1P nor PDGF modify intracellular calcium concentration ([Ca(2+)]( i )) and Smad2 phosphorylation. Using pharmacological inhibitors of Erk1/2 and PI3K, our results demonstrate a critical role of the Erk1/2 and PI3K/Akt signaling pathways in mediating the anti-apoptotic effect of S1P and PDGF on hES cells. However, inhibition of the mammalian target of rapamycin (mTOR), a common downstream effector of Erk1/2 and PI3K/Akt, has no effect on hES cell apoptosis.