Current status of human embryonic stem cell research

Human embryonic stem cells (ESC) attract profound scientific and public attention due to their far-reaching potential applications in the study of early human development, the development of new drugs and regenerative medicine. Given the capability of human ESC to proliferate extensively in culture and their pluripotent potential, human ESC may serve as a renewable unlimited source of cells for transplantation therapy. In addition, genetically manipulated transplanted human ESC may serve as a vector to carry and express genes in target organs in the course of gene therapy. While human ESC show great promise, bulk cultures of standardized cells suitable for clinical trials should be developed, and additional research is required to control the growth and differentiation of the cells and to overcome the risk of tumour formation and graft rejection. The recent development of humanized, feeder-free culture systems to derive and culture human ESC, methods to genetically modify the cells, and strategies to derive highly enriched populations of functional differentiated cells of a specific type are encouraging. It is anticipated that these achievements will set the stage for further developments that may eventually allow the exploitation of the considerable potential of human ESC for cell and gene therapy.     

The debate surrounding human embryonic stem cell research in the USA

Despite its potential for reducing human suffering, the advancement of human embryonic stem cell research has not been given top priority by the US government, and the scientific community has been engaged in a debate on this issue in the USA and beyond. The central question in this debate is whether the promise of stem cells justifies the destruction of human embryos - mainly embryos that are surplus to the needs of patients undergoing infertility treatment. It is argued here that this debate belongs in the same category as the debates on global warming and evolution, because it has much in common with both. It is conducted with a heavy load of scientifically uninformed views and beliefs and framed largely by an implacable opposition with the aim of creating public confusion and doubt. It is primarily politically motivated and, as is true about the debate on evolution, it is rooted in religion. A human embryo is not a human being or person even if it is deserving of - and receives - respect and extraordinary care in the context of assisted human reproduction. Rather than engaging in a futile debate that clouds the way forward in a vital branch of biology, scientists ought to continue to emphasize the importance of human embryo research.     

人类胚胎干细胞的研究近况

人类胚胎于细胞（human embryonic stemcell，hES）研究始于1998年，它已成为继人类基因组计划后生命科学中最活跃的研究领域。利用hES细胞修复或替代因各种因素所造成的人体组织器官缺损和功能障碍是人类疾病治疗模式划时代的革新。用于细胞替代治疗的hES细胞必须具备安全性、有效性、免疫豁免性三大特点，因而很多研究集中于以下课题：（1）纯化hES细胞培养环境，避免动物源性物质的污染。（2）hES细胞诱导分化为各种成体细胞及其前体细胞以及移植。（3）体细胞核移植与hES细胞系的建立。（4）hES细胞与基因治疗。     

Stable embryonic stem cell lines in rabbits: potential small animal models for human research

Although embryonic stem (ES) cell lines derived from mice and primates are used extensively, the development of such lines from other mammals is extremely difficult because of their rapid decline in proliferation potential and pluripotency after several passages. This study describes the establishment of rabbit ES cell lines with indefinite proliferation potential. It was found that the feeder cell density determines the fate of rabbit ES cells, and that maximum proliferation potential was obtained when they were cultured on a feeder cell density of one-sixth of the density at confluency. Higher and lower densities of feeder cells induced ES cell differentiation or division arrest. Under optimized conditions, rabbit ES cells were passaged 50 times, after which they still possessed high telomerase activity. This culture system enabled efficient gene transduction and clonal expansion from single cells. During culture, rabbit ES cells exhibited flattened monolayer cell colonies, as reported for monkey and human ES cells, and expressed pluripotency markers. Embryoid bodies and teratomas formed readily in vitro and in vivo respectively. These ES cell lines can be safely cryopreserved for later use. Thus, rabbit ES cells can be added to the list of stable mammalian ES cells, enabling the rabbit to be used as a small animal model for the study of human cell transplantation therapy.     

胚胎干细胞体外分化为生殖细胞的研究进展

鼠胚胎干细胞体外已成功诱导分化为生殖细胞和配子,人胚胎干细胞也表现出相似的分化能力。本文重点综述了原始生殖细胞(PGC)的起源和发育、PGC发育的相关因素、体外胚胎干细胞分化为原始生殖细胞和配子的过程及其影响因素、多能成体干细胞分化为生殖细胞等方面。     

单细胞克隆人胚胎干细胞系的建立及其生物学特性的鉴定

目的建立单细胞克隆人胚胎干细胞系,并对其生物学特性进行鉴定。方法采取分离自人囊胚内细胞团并传代20代的细胞,用胰酶消化将细胞分散成单细胞悬液,将单个细胞接种至96孔板,生长出的细胞集落用胶原酶消化传代,采用细胞化学法和免疫荧光法检测细胞表面标志物;采用常规G带法分析细胞染色体核型;将细胞接种至严重联合免疫缺陷小鼠后腿肌肉内,观察细胞多向分化潜能。结果接种的96个细胞生长出2个细胞集落,扩增建立了2个单细胞克隆人胚胎干细胞系,稳定增殖了12个月,传代48代。细胞呈集落状生长,细胞核大、核仁明显;具有稳定的46XX核型;细胞的碱性磷酸酶、阶段特异性胚胎抗原（SSEA）4、肿瘤识别抗原（TRA）1-60、TRA-1-81等特征性细胞表面标志物呈阳性;接种至严重联合免疫缺陷小鼠后腿肌肉内的细胞,形成了包含神经组织、软骨组织、鳞状上皮组织及柱状上皮组织等来源于3个胚层组织细胞的畸胎瘤。结论本研究成功建立了单细胞克隆人胚胎干细胞系,其生物学特性稳定。     

Establishment and characterization of new human embryonic stem cell lines

Human embryonic stem cells (hESC), with their ability to differentiate into all cell types in the human body, are likely to play a very important therapeutic role in a variety of neurodegenerative and life-threatening disorders in the near future. Although more than 120 different human embryonic stem cell lines have been reported worldwide, only a handful are currently available for researchers, which limits the number of studies that can be performed. This study reports the isolation, establishment and characterization of new human embryonic stem cell lines, as well as their differentiation potential into variety of somatic cell types. Blastocyst-stage embryos donated for research after assisted reproductive techniques were used for embryonic stem cell isolation. A total of 31 blastocysts were processed either for immunosurgery or direct culture methods for inner cell mass isolation. A total of nine primary stem cell colonies were isolated and of these, seven cell lines were further expanded and passaged. Established lines were characterized by their cellular and colony morphology, karyotypes and immunocytochemical properties. They were also successfully cryopreserved/thawed and showed similar growth and cellular properties upon thawing. When induced to differentiate in vitro, these cells formed a variety of somatic cell lineages including cells of endoderm, ectoderm and mesoderm origin. There is now an exponentially growing interest in stem cell biology as well as its therapeutic applications for life-threatening human diseases. However, limited availability of stem cell lines as well as financial or ethical limitations restrict the number of research projects. The establishment of new hESC lines may create additional potential sources for further worldwide and nationwide research on stem cells.