人胚胎干细胞向内皮细胞的分化诱导

BACKGROUND:Human embryonic stem cells exhibit self-renewal and multi-differentiation potential, and can differentiate into endothelial cells under certain induction conditions. OBJECTIVE:To explore induced conditions of the human embryonic stem cells differentiating into endothelial cells and to investigate the effect of vascular endothelial growth factors on the endothelial differentiation of human embryonic stem cells. METHODS:After resuscitation, passage 40 human embryonic stem cell lines H9 were subjected to suspension culture to prepare embryos, and after 5-day culture, these cells were cultured in attachment medium to differentiate into embryoid bodies, followed by induction with 50 µg/L vascular endothelial growth factors. Passage 2 and 15 embryonic stem cells after induced differentiation were taken for Dil-Ac-LDL uptake test and immunohistochemical staining, respectively. RESULTS AND CONCLUSION:After 1-day culture, cord-like or polygonal monolayer cells around embryoid bodies showed bud-like and radial growth with a relative rapid speed merging into surrounding colonies; at 2-3 days, the number of suspension cells increased further, but the small-round cells in the center began to die; at 5 days, embryoid bodies started to passage, and aggregated cells exhibited typical paving stone-like appearance. Moreover, some human embryonic cells after induced differentiation could actively take up fluorescent labeled LDL, and red fluorescent particles appeared. Additionally, passage 15 embryonic stem cells after induced differentiation could express CD31 and FLK-1. These findings suggest that human embryonic stem cells induced by vascular endothelial growth factors can differentiate into endothelial cells.     

人孤雌胚胎干细胞与正常胚胎干细胞分化能力的比较

目的 比较人类孤雌胚胎干细胞(pESCs)系与正常胚胎干细胞(nESCs)系的分化能力,探讨pESCs是否和nESCs一样具有多向分化潜能.方法 将pESCs和nESCs分别注射到重症联合免疫缺陷(SCID)小鼠体内形成畸胎瘤,瘤体组织切片和HE染色后进行组织学分析;将pESCs和nESCs体外悬浮培养形成拟胚体(EB),利用RT-PCR检测3个胚层主要器官以及滋养层细胞发育关键基因的表达;将pESCs和nESCs定向诱导分化为滋养层细胞,通过流式细胞仪测定人绒毛膜促性腺激素-β(hCG-β)阳性细胞比例以及通过酶联免疫吸附测定(ELISA)进行hCG-β的定量分析.结果 在体内生长和体外培养过程中,pESCs和nESCs均能够向3个胚层的细胞类型分化.在SCID小鼠体内可形成畸胎瘤,有神经上皮、软骨、腺上皮等3个胚层的衍生物产生;pESCs和nESCs来源的EB在体外自发分化5~21d后,均检测到3个胚层主要器官以及滋养层细胞发育关键基因的表达;pESCs定向分化为滋养细胞后,可以检测到hCG-β的表达,但其阳性细胞比例和分泌量均低于nESCs.结论 pESCs具有向3个胚层以及滋养层细胞分化的能力,但是向滋养层细胞分化的能力仍低于nESCs.     

Derivation and spontaneous differentiation of human embryonic stem cells

Embryonic stem (ES) cells are unique cells derived from the inner cell mass of the mammalian blastocyst. These cells are immortal and pluripotent, retain their developmental potential after prolonged culture, and can be continuously cultured in an undifferentiated state. Many in vitro differentiation systems have been developed for mouse ES cells, including reproducible methods for mouse ES cell differentiation into haematopoietic and neural precursors, cardiomyocytes, insulin‐secreting cells, endothelial cells and various other cell types. The derivation of new human ES cell lines provides the opportunity to develop unique models for developmental research and for cell therapies. In this review we consider the derivation and spontaneous differentiation of human ES cells.     

Signaling mechanisms regulating self-renewal and differentiation of pluripotent embryonic stem cells

An ability to propagate pluripotent embryonic cells in culture is the foundation both for defined germline modification in experimental rodents and for future possibilities for broad-based cellular transplantation therapies in humans. Yet, the molecular basis of the self-renewing pluripotent phenotype remains ill-defined. The relationship between factors that influence embryonic stem cell propagation in vitro and mechanisms of stem cell regulation operative in the embryo is also uncertain. In this article we discuss the role of intracellular signalling pathways in the maintenance of pluripotency and induction of differentiation in embryonic stem cell cultures and the mammalian embryo.     

Human motor neuron differentiation from human embryonic stem cells

The therapeutic potential of embryonic stem (ES) cells is promising, but in many cases limited by our inability to promote their differentiation to specific cell types, such as motor neurons. Here we provide the first report of the successful differentiation of human ES cells to cells of a motor neuron phenotype. A renewable source of neuroepithelial cells was generated from human ES cells. Extracellular signals were then employed to induce motor neuron differentiation and related gene expression by these cells. OLIG2 and HLXB9 gene expression increased upon the addition of basic fibroblast growth factor, retinoic acid, and sonic hedgehog, as a motor neuron phenotype expressing Islet1 and choline acetyltransferase (ChAT) developed. This study demonstrates that neuroepithelial cells derived from human ES cells are renewable progenitors capable of generating motor neurons at levels that may be therapeutically useful. Sonic hedgehog, basic fibroblast growth factor, and retinoic acid differentially influence human motor neuron differentiation by mechanisms that remain to be defined.     

体外直接诱导人胚胎干细胞向神经细胞分化的研究

目的探讨体外直接诱导HSF6人胚胎干细胞（humanem bryonic stem cells,hESCs）分化为神经细胞的方法。方法采用直接的方法,在1%血清培养条件下,顺序添加bFGF、RA和Forskolin,诱导HSF6人ESCs分化为神经细胞。结果细胞发生神经样形态学改变,免疫荧光细胞化学分析结果显示,分化细胞表达神经干细胞特异性标志分子——巢蛋白（nestin）,以及神经元标志分子——β微管蛋白Ⅲ（neuron-specific class Ⅲ beta-tubulin,TuJ1）。实验组nestin阳性细胞数占（95.2±3.03）%,明显高于未添加诱导因子组的（31.6±4.93）%,差异有统计学意义（P〈0.05）。结论本研究直接诱导hESCs分化为神经细胞,减少了常规经胚胎体（embryoid body,EB）的诱导方法而产生其它胚层细胞的机会,为进一步探索hESCs源性神经细胞的功能,以及为细胞替代治疗提供高纯度的hESCs源性神经细胞奠定了基础。     

Abnormal CpG island methylation occurs during in vitro differentiation of human embryonic stem cells

Directed differentiation of human embryonic stem cells (hESCs) into specific somatic cells holds great promise for cell replacement therapies. However, it is unclear if in vitro hESC differentiation causes any epigenetic abnormality such as hypermethylation of CpG islands. Using a differential methylation hybridization method, we identified 65 CpG islands (out of 4608 CpG islands or 1.4%) that exhibited increased DNA methylation during the conversion of hESCs into neural progenitor/stem cells (NPCs). These methylated CpG islands belong to genes in cell metabolism, signal transduction and cell differentiation, which are distinctively different from oncogenic CpG island hypermethylation observed in cancer-related genes during tumorigenesis. We further determined that methylation in these CpG islands, which is probably triggered by de novo DNA methyltransferase Dnmt3a, is abnormally higher in hESC-NPCs than in primary NPCs and astrocytes. Correlating with hypermethylation in promoter CpG islands of metabolic enzyme gene CPT1A and axoneme apparatus gene SPAG6, levels of CPT1A and SPAG6 mRNAs are significantly reduced in hESC-NPCs when compared with hESCs or primary neural cells. Because CPT1A is involved in lipid metabolism and CPT1A deficiency in human is associated with the hypoketotic hypoglycemia disorder, the reduced CPT1A expression in hESC-NPCs raises a potential concern for the suitability of these cells in cell transplantation. Collectively, our data show that abnormal CpG island methylation takes place in a subset of genes during the differentiation/expansion of hESC derivatives under current culture conditions, which may need to be monitored and corrected in future cell transplantation studies.     

Cardiomyocyte differentiation of mouse and human embryonic stem cells*

Ischaemic heart disease is the leading cause of morbidity and mortality in the western world. Cardiac ischaemia caused by oxygen deprivation and subsequent oxygen reperfusion initiates irreversible cell damage, eventually leading to widespread cell death and loss of function. Strategies to regenerate damaged cardiac tissue by cardiomyocyte transplantation may prevent or limit post‐infarction cardiac failure. We are searching for methods for inducing pluripotent stem cells to differentiate into transplantable cardiomyocytes. We have already shown that an endoderm‐like cell line induced the differentiation of embryonal carcinoma cells into immature cardiomyoctyes. Preliminary results show that human and mouse embryonic stem cells respond in a similar manner. This study presents initial characterization of these cardiomyocytes and the mouse myocardial infarction model in which we will test their ability to restore cardiac function.     

Monitoring differentiation of human embryonic stem cells using real-time PCR

There is a general lack of rapid, sensitive, and quantitative methods for the detection of differentiating human embryonic stem cells (hESCs). Using light microscopy and immunohistochemistry, we observed that morphological changes of differentiating hESCs precede any major alterations in the expression of several commonly used hESC markers (SSEA-3, SSEA-4, TRA-1-60, TRA-1-81, Oct-4, and Nanog). In an attempt to quantify the changes during stochastic differentiation of hESCs, we developed a robust and sensitive multi-marker quantitative real-time polymerase chain reaction (QPCR) method. To maximize the sensitivity of the method, we measured the expression of up- and downregulated genes before and after differentiation of the hESCs. Out of the 12 genes assayed, we found it clearly sufficient to determine the relative differentiation state of the cells by calculating a collective expression index based on the mRNA levels of Oct-4, Nanog, Cripto, and alpha-fetoprotein. We evaluated the method using different hESC lines maintained in either feeder-dependent or feeder-free culture conditions. The QPCR method is very flexible, and by appropriately selecting reporter genes, the method can be designed for various applications. The combination of QPCR with hESC-based technologies opens novel avenues for high-throughput analysis of hESCs in, for example, pharmacological and cytotoxicity screening.     

人胚胎干细胞体外培养并分化为心肌细胞

目的 :体外培养并鉴定人胚胎干细胞 (EG细胞 ) ,在不添加细胞因子的条件下 ,观察细胞集落分化情况。方法 :取 4～ 6周人胚胎生殖嵴、肠背系膜和中肾嵴 ,进行组织块培养 ,利用组织化学和免疫组织化学技术对培养的细胞进行鉴定。结果 :培养 7～ 8小时 ,在组织块周围出现成纤维细胞 ;5～ 7天后 ,在成纤维细胞上出现EG细胞集落 ,集落内细胞表达阶段特异性胚胎表面抗原SSEA 1和SSEA 3,并表达碱性磷酸酶 (ALP)活性 ;培养 1 8天后 ,有6个集落分化为有节律跳动的心肌细胞 ,这些细胞集落在继续培养 1 5天后 ,仍能有节律收缩。此时集落内细胞ALP表达呈阴性 ,但仍有少量细胞表达SSEA 1和SSEA 3。结论 :体外培养人胚生殖嵴、肠背系膜和中肾嵴组织块 ,以内源性的成纤维细胞作为饲养层 ,可以分离得到EG细胞集落 ,一些EG细胞集落可以自发地分化成心肌细胞。     

Efficient differentiation of functional hepatocytes from human embryonic stem cells

Differentiation of human embryonic stem cells (hESCs) to specific functional cell types can be achieved using methods that mimic in vivo embryonic developmental programs. Current protocols for generating hepatocytes from hESCs are hampered by inefficient differentiation procedures that lead to low yields and large cellular heterogeneity. We report here a robust and highly efficient process for the generation of high-purity (70%) hepatocyte cultures from hESCs that parallels sequential hepatic development in vivo. Highly enriched populations of definitive endoderm were generated from hESCs and then induced to differentiate along the hepatic lineage by the sequential addition of inducing factors implicated in physiological hepatogenesis. The differentiation process was largely uniform, with cell cultures progressively expressing increasing numbers of hepatic lineage markers, including GATA4, HNF4alpha, alpha-fetoprotein, CD26, albumin, alpha-1-antitrypsin, Cyp7A1, and Cyp3A4. The hepatocytes exhibited functional hepatic characteristics, such as glycogen storage, indocyanine green uptake and release, and albumin secretion. In a mouse model of acute liver injury, the hESC-derived definitive endoderm differentiated into hepatocytes and repopulated the damaged liver. The methodology described here represents a significant step toward the efficient generation of hepatocytes for use in regenerative medicine and drug discovery.     

Neurotrophin-induced differentiation of human embryonic stem cells on three-dimensional polymeric scaffolds

Human embryonic stem (hES) cells have the potential to form various cell types, including neural cells for the treatment of diseases such as Parkinson's, spinal cord injury, and glaucoma. Here, we have investigated the neuronal differentiation of hES cells on three-dimensional scaffolds fabricated from degradable poly(alpha-hydroxy esters) including poly(lactic-co-glycolic acid) and poly(L-lactic acid). When cultured in vitro, neural rosette-like structures developed throughout the scaffolds with differentiation dependent on factors in the medium (e.g., retinoic acid [RA], nerve growth factor [NGF], and neurotrophin 3 [NT-3]) and the differentiation stage of the cells. Specifically, enhanced numbers of neural structures and staining of nestin (a marker of neural precursors) and beta(III)-tubulin (indicative of neural differentiation) were observed with hES cell-seeded polymer scaffolds when cultured with both NGF and NT-3 when compared with control medium. In addition, vascular structures were found throughout the engineered tissues when cultured with the neurotrophins, but not in the presence of RA.