Establishment of germline-competent embryonic stem cell lines from the MSM/Ms strain

MSM/Ms is an inbred mouse strain established from the Japanese wild mouse, Mus musculus molossinus, which has been phylogenetically distinct from common laboratory mouse strains for about 1 million years. The nucleotide substitution rate between MSM/Ms and C57BL/6 is estimated to be 0.96%. MSM/Ms mice display unique characteristics not observed in the commonly used laboratory strains, including an extremely low incidence of tumor development, high locomotor activity, and resistance to high-fat-diet-induced diabetes. Thus, functional genomic analyses using MSM/Ms should provide a powerful tool for the identification of novel phenotypes and gene functions. We report here the derivation of germline-competent embryonic stem (ES) cell lines from MSM/Ms blastocysts, allowing genetic manipulation of the M. m. molossinus genome. Fifteen blastocysts were cultured in ES cell medium and three ES lines, Mol/MSM-1, -2, and -3, were established. They were tested for germline competency by aggregation with ICR morulae and germline chimeras were obtained from all three lines. We also injected Mol/MSM-1 ES cells into blastocysts of ICR or C57BL/6 × BDF1 mice and found that blastocyst injection resulted in a higher production rate of chimeric mice than did aggregation. Furthermore, Mol/MSM-1 subclones electroporated with a gene trap vector were also highly efficient at producing germline chimeras using C57BL/6 × BDF1 blastocyst injection. This Mol/MSM-1 ES line should provide an excellent new tool allowing the genetic manipulation of the MSM/Ms genome.     

胚胎干细胞向造血干/祖细胞定向诱导分化的研究进展

胚胎干细胞(embryonic stem cell,ES细胞)是指由胚胎内细胞团(inner cell mass,ICM)细胞经体外抑制培养而筛选得到的细胞,具有无限增殖潜能,在体外可以向造血细胞分化,有可能为造血干细胞移植和血细胞输注开辟新的来源．此外,ES细胞向造血干/祖细胞的定向诱导分化也为阐明哺乳动物造血发育的细胞和分子机制提供了良好的体外模型．对ES细胞向造血干/祖细胞定向分化的研究进展进行了综述．     

Keratinocytes derived from embryonic stem cells induce wound healing in mice

The skin plays an important role in defending the body against the environment. Treatments for burns and skin injuries that use autologous or allogenic skin grafts derived from adult or embryonic stem cells are promising. Embryonic stem cells are candidates for regenerative and reparative medicine. We investigated the utility of keratinocyte-like cells, which are differentiated from mouse embryonic stem cells, for wound healing using a mouse surgical wound model. Mice were allocated to the following groups: experimental, in which dressing and differentiated cells were applied after the surgical wound was created; control, in which only the surgical wound was created; sham, in which only the dressing was applied after the surgical wound was created; and untreated animal controls with healthy skin. Biopsies were taken from each group on days 3, 5 and 7 after cell transfer. Samples were fixed in formalin, then stained with Masson’s trichrome and primary antibodies to interleukin-8 (IL-8), fibroblast growth factor-2 (FGF-2), monocyte chemoattractant protein-1 (MCP-1), collagen-1 and epidermal growth factor (EGF) using the indirect immunoperoxidase technique for light microscopy. Wound healing was faster in the experimental group compared to the sham and control groups. The experimental group exhibited increased expression of IL-8, FGF-2 and MCP-1 during early stages of wound healing (inflammation) and collagen-1 and EGF expression during late stages of wound healing (proliferation and remodeling). Keratinocytes derived from embryonic stem cells improved wound healing and influenced the wound healing stages.     

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。     

Rapid selection of XO embryonic stem cells using Y chromosome-linked GFP transgenic mice

We developed a transgenic mouse line with Y chromosome-linked green fluorescent protein expressing transgenes (Y-GFP) by the conventional microinjection into the pronucleus of C57BL/6J fertilized oocytes. Embryonic stem (ES) cells derived from Y-GFP mice enabled not only sexing but also the identification of 39, XO karyotype by the lack of Y chromosome. Actually, when fluorescence activated cell sorting (FACS) was applied to Y-GFP ES cells, non-fluorescent ES cells were conveniently collected and showed the lack of Y chromosome by PCR genotyping and Southern blot analysis. FACS analysis revealed Y chromosome loss occurred at 2.9 % of 40, XY ES cells after five passages. These Y-GFP ES cells are potentially applicable to reduce the time, cost and effort needed to generate the gene-targeted mice by the production of male and female mice derived from the same ES cell clone.     

Vascular engineering using human embryonic stem cells

Engineering vascularized tissue constructs remains a major problem in regenerative medicine. The formation of such a microvasculature—like the vasculogenesis in early embryogenesis that it closely resembles—is guided by biochemical and biophysical cues, such as growth factors, extracellular matrix proteins, hypoxia, and hydrodynamic shear. As they undergo spontaneous and directed vascular differentiation, human embryonic stem cells can be used as a model system to explore central issues in engineering vascularized tissue constructs and, potentially, to elucidate vasculogenic and angiogenic mechanisms involved in such vascular diseases as limb and cardiac ischemia. Because the conventional spontaneous differentiation approach can only isolate small quantities of vascular cells, recent efforts have sought to develop controlled approaches, including the development of three‐dimensional scaffolds to reengineer the microenvironments of early embryogenesis. This review focuses on emerging approaches to deriving and directing vasculatures from human embryonic stem cells and efforts to engineer 3D vasculatures from such derivatives. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Hybridization of testis-derived stem cells with somatic cells and embryonic stem cells in mice

Somatic cell hybridization is widely used to study the control of gene regulation and the stability of differentiated states. In contrast, the application of this method to germ cells has been limited in part because of an inability to culture germ cells. In this study, we produced germ cell hybrids using germ-line stem (GS) cells and multipotent germ-line stem (mGS) cells. While GS cells are enriched for spermatogonial stem cell (SSC) activity, mGS cells are similar to embryonic stem (ES) cells and originally derived from GS cells. Hybrids were successfully obtained between GS cells and ES cells, between GS cells and mGS cells, and between mGS cells and thymocytes. All exhibited ES cell markers and a behavior similar to ES cells, formed teratomas, and differentiated into somatic cell tissues. However, none of the hybrid cells were able to reconstitute spermatogenesis after microinjection into seminiferous tubules. Analyses of the DNA methylation patterns of imprinted genes also showed that mGS cells do not possess a DNA demethylation ability, which was found in embryonic germ cells derived from primordial germ cells. However, mGS cells reactivated the X chromosome and induced Pou5f1 expression in female thymocytes in a manner similar to ES cells. These data show that mGS cells possess ES-like reprogramming potential, which predominates over-SSC activity.     

Derivation of hematopoietic stem cells from murine embryonic stem cells

A stem cell is defined as a cell with the capacity to both self-renew and generate multiple differentiated progeny. Embryonic stem cells (ESC) are derived from the blastocyst of the early embryo and are pluripotent in differentiative ability. Their vast differentiative potential has made them the focus of much research centered on deducing how to coax them to generate clinically useful cell types. The successful derivation of hematopoietic stem cells (HSC) from mouse ESC has recently been accomplished and can be visualized in this video protocol. HSC, arguably the most clinically exploited cell population, are used to treat a myriad of hematopoietic malignancies and disorders. However, many patients that might benefit from HSC therapy lack access to suitable donors. ESC could provide an alternative source of HSC for these patients. The following protocol establishes a baseline from which ESC-HSC can be studied and inform efforts to isolate HSC from human ESC. In this protocol, ESC are differentiated as embryoid bodies (EBs) for 6 days in commercially available serum pre-screened for optimal hematopoietic differentiation. EBs are then dissociated and infected with retroviral HoxB4. Infected EB-derived cells are plated on OP9 stroma, a bone marrow stromal cell line derived from the calvaria of M-CSF-/- mice, and co-cultured in the presence of hematopoiesis promoting cytokines for ten days. During this co-culture, the infected cells expand greatly, resulting in the generation a heterogeneous pool of 100 s of millions of cells. These cells can then be used to rescue and reconstitute lethally irradiated mice.     

Generation of skeletal muscle from transplanted embryonic stem cells in dystrophic mice

Embryonic stem (ES) cells have great therapeutic potential because of their capacity to proliferate extensively and to form any fully differentiated cell of the body, including skeletal muscle cells. Successful generation of skeletal muscle in vivo, however, requires selective induction of the skeletal muscle lineage in cultures of ES cells and following transplantation, integration of appropriately differentiated skeletal muscle cells with recipient muscle. Duchenne muscular dystrophy (DMD), a severe progressive muscle wasting disease due to a mutation in the dystrophin gene and the mdx mouse, an animal model for DMD, are characterized by the absence of the muscle membrane associated protein, dystrophin. Here, we show that co-culturing mouse ES cells with a preparation from mouse muscle enriched for myogenic stem and precursor cells, followed by injection into mdx mice, results occasionally in the formation of normal, vascularized skeletal muscle derived from the transplanted ES cells. Study of this phenomenon should provide valuable insights into skeletal muscle development in vivo from transplanted ES cells.     

Generation of progeny from embryonic stem cells by microinsemination of male germ cells from chimeric mice

Mice chimeric for embryonic stem (ES) cells have not always successfully produced ES-derived offspring. Here we show that the male gametes from ES cells could be selected in male chimeric mice testes by labeling donor ES cells or host blastocytes with GFP. Male GFP-expressing ES-derived germ cells occurred as colonies in the chimeric testes, where the seminiferous tubules were separated into green and non-green regions. When mature spermatozoa from green tubules were used for microinsemination, GFP-expressing offspring were efficiently obtained. Using a reverse study, we also obtained ES-derived progeny from GFP-negative ES cells in GFP-labeled host chimeras. Furthermore, we showed this approach could be accelerated by using round spermatids from the testes of 20-day-old chimeric mice. Thus, this technique allowed us to generate the ES cell-derived progeny even from the low contributed chimeric mice, which cannot produce ES-origin offspring by natural mating.     

Translational deregulation in PDK-1-/- embryonic stem cells

PDK-1 is a protein kinase that is critical for the activation of many downstream protein kinases in the AGC superfamily, through phosphorylation of the activation loop site on these substrates. Cells lacking PDK-1 show decreased activity of these protein kinases, including protein kinase B (PKB) and p70S6K, whereas mTOR activity remains largely unaffected. Here we show, by assessing both association of cellular RNAs with polysomes and by metabolic labeling, that PDK-1-/- embryonic stem (ES) cells exhibit defects in mRNA translation. We identify which mRNAs are most dramatically translationally regulated in cells lacking PDK-1 expression by performing microarray analysis of total and polysomal RNA in these cells. In addition to the decreased translation of many RNAs, a smaller number of RNAs show increased association with polyribosomes in PDK-1-/- ES cells relative to PDK-1+/+ ES cells. We show that PKB activity is a critical downstream component of PDK-1 in mediating translation of cystatin C, RANKL, and Rab11a, whereas mTOR activity is less important for effective translation of these targets.     

Decreased surfactant protein B expression in mice derived completely from embryonic stem cells

ES mice that are derived completely from embryonic stem (ES) cells can be obtained by tetraploid embryo complementation. Many neonate ES mice die because of respiratory distress, but it is not clear what contributes to the phenomenon. Using five microsatellite DNA markers, we confirmed that our ES mice were completely derived from ES cells and contained no tetraploid component. The neonatal ES mice that exhibited respiratory distress were tested for surfactant protein B (SP-B) expression by Western blotting. These mice had no SP-B expression, and even apparently healthy adult ES mice had decreased SP-B levels and aberrant SP-B phenotypes. These data suggest that the expression of SP-B protein is an important factor in the survival of ES mice to term and adulthood.     

Study of hepatocyte differentiation using embryonic stem cells

The liver has many crucial functions including metabolizing dietary molecules, detoxifying compounds, and storing glycogen. The hepatocytes, comprising most of the liver organ, progressively modify their gene expression profile during the fetal development according to their roles in the different phases of development. Embryonic stem (ES) cells serve as a major tool in understanding liver development. These cells may also serve as a source of hepatic cells for cellular therapy. In this review, we aim to summarize the research that has been performed in the field of hepatocyte differentiation from mouse and human ES cells. We discuss the various methodologies for the differentiation of ES cells towards hepatic cells using either spontaneous or directed differentiation protocols. Although many protocols for differentiating ES cells to hepatic cells have been developed, the analysis of their status is not trivial and can lead to various conclusions. Hence, we discuss the issues of analyzing hepatocytes by means of the specificity of the markers for hepatocytes and the status of the cells as fetal or adult hepatocytes.