不同ES细胞系体定量神经分化的比较

利用视黄酸（RA）诱导小鼠胚胎干细胞通过悬浮类胚培养体外定量分化为神经样细胞,结果显示能够进行种系嵌合的MESPU22细胞系与不能进行种系统嵌合的MESPU13细胞系的体外神经分化比例在统计学上没有明显差异,此结果对于人的胚胎干细胞全能性的鉴定和检测有重要启示。     

Advances in cell lineage reprogramming

As a milestone breakthrough of stem cell and regenerative medicine in recent years,somatic cell reprogramming has opened up new applications of regenerative medicine by breaking through the ethical shackles of embryonic stem cells.However,induced pluripotent stem(iPS) cells are prepared with a complicated protocol that results in a low reprogramming rate.To obtain differentiated target cells,iPS cells and embryonic stem cells still need to be induced using step-by-step procedures.The safety of induced target cells from iPS cells is currently a further concerning matter.More broadly conceived is lineage reprogramming that has been investigated since 1987.Adult stem cell plasticity,which triggered interest in stem cell research at the end of the last century,can also be included in the scope of lineage reprogramming.With the promotion of iPS cell research,lineage reprogramming is now considered as one of the most promising fields in regenerative medicine,will hopefully lead to customized,personalized therapeutic options for patients in the future.     

ES cells derived from cloned embryos in monkey--a jump toward human therapeutic cloning

Therapeutic cloning refers to the derivation of embryonic stem cells （ntESC） from embryos derived from somatic cell nuclear transfer （SCNT） also known as cloning. Cloning involves transplanting a differentiated cell into an oocyte that has had its nucleus （DNA） removed. The reconstructed oocyte can be activated to divide and develop into an embryo. The process that allows this to happen is termed nuclear reprogramming, and is defined as the mechanism through which a differentiated cell de-differentiates or returns to a totipotent state （capable of giving rise to any cell type, including extra-embryonic） and directs embryonic development [1]. Cells from blastocyst stage cloned embryos can be used to generate ntESC lines. Such cell lines can differentiate into any adult cell type, and have tremendous potential for patient-specific disease therapy [2].     

小鼠精原干细胞与胚胎干细胞样细胞

近年来,通过培养小鼠精原干细胞(spermatogonial stem cells,SSCs)获得了胚胎干细胞样细胞(,embryonic stem cell-like cells,ES样细胞).这些研究表明小鼠精原干细胞不仅具备特异分化为精子的干细胞潜能,而且具备胚胎干细胞(embryonic stem cell,ES)分化为三胚层的多向分化潜能.因此.这将有助于研究干细胞的分化调控机制,并且这些研究成果延伸至人类精原干细胞,也将为再生医学获取特殊的胚胎干细胞样细胞或特异分化的精子细胞开辟了蹊径.     

Body Building on Diamonds

Whereas conservative therapies aim to stall the advance of disease,regenerative medicine strives to reverse it.The capacityof most tissues to regenerate derives from stem cells,but there are a number of barriers which have to be circumvented before itwill be possible to use stem-cell-based therapies.Such therapies,however,are expected to improve human health enormously,and knowledge gained from studying stem cells in culture and in model organisms is now laying the groundwork for a new eraof regenerative medicine.One of the most prominent methods to study stem cell differentiation is to let them to form embryoidbodies.Under favourable conditions any stem cell line will form embryoid bodies.However,the mechanism of the formation ofembryoid bodies is not very well understood,and to produce them in the laboratory is in no way trivial-an important technicalbarrier in stem cell research.Recently,the embryoid body cultivation step has been successfully circumvented for the derivationof osteogenic cultures of embryonic stem cells.Here we report on a simple and reusable system to cultivate embryoid bodies inextremely short times.The method is inspired by the principles that lead to the establishment of the biomimetic triangle.     

Human embryonic stem cells create their own niche

Experimental evidence demonstrates that the ability of stem cells to self-renew and to differentiate into different types of mature cells depends on both their intrinsic genetic programs and external control from their microenvironment or niche. The concept of stem cell niche was first proposed by Schofield in 1978 to describe a microenvironment that supports stem cells in a mammalian hematopoietic system. Over the last 30 years, more stem cell niches have been identified in the mammalian system, including the hematopoietic stem cell niche in bone marrow, the epithelial stem cell niche in skin, the intestinal stem cell niche, the neural stem cell niche and the germ line stem cell niche in mice ）. Recently, the concept of stem cell niche is further defined. The niche must have both anatomic and functional dimensions and may be composed of heterologous cell types, extracellular matrix, paracrine factors or non-protein metabolites . More recently, it was shown that disruption in the niche of hematopoietic stem cells leads to the development ofmyeloproliferative disease . It becomes obvious that a stem cell niche is not static, but dynamic, and can be modified or even created. Although stem cell niche has emerged as critical as stem cell autonomous functions for both our understanding of stem cell biology and the application of stem cells in medicine, a niche for human embryonic stem （hES） cells was not clearly shown until recently Bendall et al demonstrated that IGF and FGF cooperatively establish the regulatory stem cell niche of pluriootent human cells in vitro.[第一段]     

Molecular cloning and functional analysis of ESGP, an embryonic stem cell and germ cell specific protein

Several putative Oct-4 downstream genes from mouse embryonic stem （ES） cells have been identified using the suppression-subtractive hybridization method. In this study, one of the novel genes encoding an ES cell and germ cell specific protein （ESGP） was cloned by rapid amplification of cDNA ends. ESGP contains 801 bp encoding an 84 amino acid small protein and has no significant homology to any known genes. There is a signal peptide at the N-terminal of ESGP protein as predicted by SeqWeb （GCG） （SeqWeb version 2 ttp：//gcg.biosino.org：8080/）. The result of immunofluorescence assay suggested that ESGP might encode a secretory protein. The expression pattern of ESGP is consistent with the expression of Oct-4 during embryonic development. ESGP protein was detected in fertilized oocyte, from 3.5 day postcoital （dpc） blastocyst to 17.5 dpc embryo, and was only detected in testis and ovary tissues in adult. In vitro, ESGP was only expressed in pluripotent cell lines, such as embryonic stem cells, embryonic carcinoma cells and embryonic germ cells, but not in their differentiated progenies. Despite its specific expression, forced expression of ESGP is not indispensable for the effect of Oct-4 on ES cell self-renewal, and does not affect the differentiation to three germ layers.     

Determination of stoichiometry of radioiodination of proteins

A sensitive method for the detection of small quantities of hydrophobic antioxidant free radical scavengers such as butylatedhydroxytoluene (BHT) and butylatedhydroxyanisole (BHA) in aqueous samples is described. The procedure involves extraction of the hydrophobic free radical scavenger into an organic solvent phase, followed by the subsequent reaction of an aliquot of this extract with the stable cation radical tris(p-bromophenyl)amminium hexachloroantimonate (TBACA). In experiments with BHT and BHA, the loss of TBACA absorbance at 730 nm was found to be linearly proportional to the amount of antioxidant added, with quantities of BHT as small as 200 pmol being easily detectable. In aqueous suspensions of dimyristoylphosphatidylcholine vesicles, assays of the aqueous BHT concentration showed that BHT partitioned strongly into the membrane phase, achieving very high BHT/phospholipid ratios. For a given concentration of BHT, partitioning into the membrane phase was greater in large, multilamellar liposomes than in either small, single-walled vesicles or in purified rat brain synaptic vesicle membranes. Direct assay of BHT and BHA in phospholipid membranes, however, was complicated by a nonspecific interaction between TBACA and the phospholipid.