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The ultrastructure of mouse embryonic stem cells.

The fine structure of mouse embryonic stem (ES) cell colonies was analysed by scanning and transmission electron microscopy. Most of the ES cells had numerous microvilli of different lengths. Coated pits and vesicles were also seen along areas of the peripheral cytoplasm and plasma membranes. Junctional complexes including gap junctions were observed between adjacent ES cells. These cells had Golgi complexes, spherical to oval mitochondria, lysosomes and typical centrioles, microfilaments and microtubules and large nuclei containing reticulated nucleoli. These results are consistent with the ultrastructural features of undifferentiated cells.

Animals↗

Use of chemical mutagenesis in mouse embryonic stem cells.

The chemical mutagenesis of mouse embryonic stem (ES) cells is an approach complementary to chemical mutagenesis of spermatogonia in whole animals. It has great potential to contribute significantly to the generation of a comprehensive collection of multiple alleles for most mammalian genes and to facilitate the progression from gene sequence to gene functional analyses. The general strategy includes the treatment of ES cells with a chemical mutagen and the isolation of individual mutagenized clones that are then cultured in duplicate. Whereas one set of samples is cryopreserved for archiving and subsequent generation of germline chimeras by means of blastocyst injection, the second set is used for genotype- or phenotype-driven screens to identify mutant alleles.

Alleles↗

Transplantation of motoneuron-enriched neural cells derived from mouse embryonic stem cells improves motor function of hemiplegic mice.

Embryonic stem (ES) cells are expected to be a potential donor source for neural transplantation. We have obtained motoneuron-enriched neural progenitor cells by culturing mouse ES cells with retinoic acid (RA). The cells also expressed mRNA of a neurotrophic factor, neurotrophin-3 (NT-3). The left motor cortex area of mice was damaged by cryogenic brain injury, and the neural cells were transplanted underneath the injured motor cortex, neighboring to the paraventricular region. We found that the cells expressing neuronal phenotypes not only remained close to the implantation site, but also exhibited substantial migration penetrating into the damaged lesion, in a seemingly directed manner up to cortical region. We found that some of the neural cells differentiated into Islet1-positive motoneurons. It seems likely that the ability of the ES cell-derived neural progenitor cells to respond in vivo to guidance cues and signals that can direct their migration and differentiation may contribute to functional recovery of the recipient mice. We found that an "island of the mature neuronal cells" of recipient origin emerged in the damaged motor cortex. This may be associated with the neuroprotective effects of the ES cell-derived neural cells. The ES cells differentiated into CD31+ vasculoendothelial cells with the RA treatment in vitro. Furthermore, the grafted cells may provide sufficient neurotrophic factors such as NT-3 for neuroprotection and regeneration. The grafted neural cells that migrated into residual cortex and differentiated into neurons had purposefully elongated axons that were stained with anti-neurofilament middle chain (NFM) antibody. Our study suggests that motoneurons can be induced from ES cells, and ES cells become virtually an unlimited source of cells for experimental and clinical neural cell transplantation.

Animals↗

Fate of pre-differentiated mouse embryonic stem cells transplanted in unilaterally 6-hydroxydopamine lesioned rats: histological characterization of the grafted cells.

We transplanted mouse embryonic stem (ES) cells pre-differentiated on a PA6 feeder cell layer into the striatum of 6-hydroxydopamine hemi-lesioned adult rats and studied the fate of the grafted cells 1 and 5 weeks post-grafting. At both time points, ES cell grafts contained tyrosine hydroxylase positive (TH+) and 5-HT immunoreactive cells. Between 1 and 5 weeks, there was an enlargement of the grafts and an increase in number of TH+ cells although the differences between the two time points were not significant. The mean number of TH+ neurons per striatum was 330 +/- 73 after 1 week and 1220 +/- 400 after 5 weeks. Over the same time period, mean soma profile area of the TH+ neurons increased significantly by 25.2%. Neurites were longer after 5 weeks (by 24.9%), but the difference to 1 week post-grafting was not reliable. The percentage of TH+ somata without neurites increased from 6.7% after 1 week to 38.3% after 5 weeks (not significant). After 5 weeks, two out of fifteen graft recipients had tumors indicating that pre-differentiation of mouse embryonic stem cells using this differentiation protocol is not sufficient to prevent tumor formation.

Animals↗

[Bone marrow endothelial cell-conditioned medium promotes hematopoietic differentiation of mouse embryonic stem cells].

The purpose of this study was to observe the bone marrow endothelial cell-conditioned medium (BECM) and cytokines, i.e. vascular endothelial growth factor (VEGF), stem cell factor (SCF) and EPO promoting the generation of hematopoietic precursor cells from mouse embryonic stem cells (ESC) in vitro. Day 4 embryoid body (4dEB) cells were derived from ESC-D3 cell line, a murine ESC line, and then induced with BECM and/or cytokines. Four groups, i.e. BECM, BECM + VEGF + SCF + EPO, VEGF + SCF + EPO and control (spontaneous differentiation), were designed. Immunochemistry staining and flow cytometry were adopted to observe the antigen expression, RT-PCR to detect hematopoietic transcription factors, and hematopoietic progenitor assay to examine hematopoietic differentiation. The results showed that the cells induced from ESC expressed hematopoietic precursor cell antigens (c-kit, Sca-1, Thy-1 and CD34), transcription factors (c-myb, SCL and beta-H1) and generated HPP-CFC and BFU-E. The effect of BECM + VEGF + SCF + EPO was the most potent in the inducing groups according to the numbers of hematopoietic precursor cells and colonies. It is concluded that BECM promotes the differentiation of ESC into hematopoietic precursor cells in vitro, and this effect is the strongest when BECM combining with VEGF + SCF + EPO.

Animals↗

Neural precursor cells differentiated from mouse embryonic stem cells relieve symptomatic motor behavior in a rat model of Parkinson's disease.

Pluripotent embryonic stem (ES) cells are the most versatile cells, with the potential to differentiate into all types of cell lineages including neural precursor cells (NPCs), which can be expanded in large numbers for significant periods of time to provide a reliable cell source for transplantation in neurodegenerative disorders such as Parkinson's disease (PD). In the present study, we used the MESPU35 mouse ES cell line, which expresses enhanced green fluorescent protein that enables one to distinguish between transplanted cells and cells of host origin. Embryoid bodies (EBs) were formed and were induced to NPCs in N2 selection medium plus fibronectin. Praxiology and immunohistochemistry methods were used to observe the survival, differentiation, and therapeutic effect of NPCs after grafted into the striatum of PD rats. We found that mouse ESc were differentiated into nestin-positive NPCs 6 days after the EBs formed and cultured in the N2 selection medium. The number of survival NPCs was increased significantly by fibronectin. About 23.76+/-2.29% of remaining cells were tyrosine hydroxylase (TH)-positive 12 days after NPCs were cultured in N2 selective medium. The survival rates of NPCs were 2.10+/-0.41% and about 90.90+/-3.00% of the engrafted NPCs were TH-positive 6 weeks after transplantation into the striatum of PD rats. The rotation of PD rats was relieved 3 weeks after the NPCs transplantation and this effect was kept for at least 6 weeks. It suggests that most of the survival NPCs derived from ES cells differentiated into TH-positive neurons after grafted into the striatum of PD rats, which produces therapeutic effect on PD.

Animals↗

A modified method for generation of neural precursor cells from cultured mouse embryonic stem cells.

The pluripotency and high proliferative capacity of embryonic stem (ES) cells make them an attractive source of different cell types for biomedical research and cell replacement therapies. It has been demonstrated that ES cells can be induced into neural precursor cells (NPCs) under conditions. NPCs can be expanded in large numbers for significant periods of time to provide a reliable source of cells for transplantation in neurodegenerative disorders and injury of the central nervous system. This study describes a modified method for generation of NPCs from cultured mouse ES cells.

Alkaline Phosphatase↗

Glucagon-like peptide-1 enhances production of insulin in insulin-producing cells derived from mouse embryonic stem cells.

Embryonic stem cells (ESCs) can be differentiated into insulin-producing cells by a five-stage procedure involving altering culture conditions and addition of nicotinamide. The amounts of insulin in these cells are lower than those found in pancreatic beta cells. Glucagon-like peptide-1 (GLP-1) induces the differentiation of beta cells from ductal progenitor cells. We examined the possibility of GLP-1, and its long-acting agonist exendin-4, enhancing the differentiation of insulin-producing cells from mouse ESCs (mESCs). A five-stage culturing strategy starting with embryoid bodies (EBs) was used in this study. mRNA for pancreatic duodenal homeobox gene 1 (PDX-1) and neurogenic differentiation (NeuroD) was detected from stage 1, hepatocyte nuclear factor 3 beta (HNF3beta) and insulin 2 from stage 2, Ngn3 and glucose transporter 2 (GLUT2) from stage 3, and insulin 1 and other beta-cell markers, at stages 4-5. Cells at stage 5 secreted C-peptide, being 0.68 +/- 0.01 pmol/10(6) cells per 2 days, and had an immunoreactive insulin content of 13.5 +/- 0.7 pmol/10(6) cells. Addition of GLP-1 (100 nM) and nicotinamide (10 mM) at stage 5 resulted in a 50% and 48% increase in insulin content and C-peptide secretion respectively compared with nicotinamide alone. Glucose-induced insulin secretion was enhanced 4-fold by addition of both growth factors. The GLP-1 receptor was present at all five stages of the culture. Addition of exendin-4 to cells at stage 2 resulted in a 4.9-fold increase in expression of the gene for insulin 1 and a 2-fold increase in insulin content compared with the effect of nicotinamide alone at stage 5. It is concluded that both GLP-1 and exendin-4 enhance the level of expression of insulin in glucose-responsive insulin-producing cells derived from the R1 mESC line.

Animals↗

Contrasting patterns of retinoblastoma protein expression in mouse embryonic stem cells and embryonic fibroblasts.

The expression of the retinoblastoma susceptibility (RB-1) gene was investigated in highly proliferating mouse embryonic stem (ES) cells and in slowly proliferating mouse embryonic fibroblasts. The RB protein was expressed at the same level in these two cell types. Mainly hyperphosphorylated RB was detected in exponentially-growing ES cells. Embryonic fibroblasts and embryonic stem cells were synchronized by colcemid block followed by mitotic shake-off. In embryonic fibroblasts, DNA replication started 10-15 h after exit from mitosis and RB was transiently dephosphorylated during the G1 phase as previously described. In ES cells, DNA replication started 2 h after release from the colcemid block but virtually no hypophosphorylated RB was observed after the release. Instead, there was a dramatic decrease in the total RB protein level between exit from mitosis and entry into S phase. These observations were made by using two different monoclonal antibodies, both in immunoblotting and immunoprecipitation experiments. Absence of hypophosphorylated RB and cell cycle-dependent change in total RB protein level may be relevant to the high proliferation rate and to the tumorigenic nature of mouse embryonic stem cells.

Animals↗

Available human feeder cells for the maintenance of human embryonic stem cells.

Mouse embryonic fibroblasts (MEFs) have been previously used as feeder cells to support the growth of human embryonic stem cells (hESCs). In this study, human adult uterine endometrial cells (hUECs), human adult breast parenchymal cells (hBPCs) and embryonic fibroblasts (hEFs) were tested as feeder cells for supporting the growth of hESCs to prevent the possibility of contamination from animal feeder cells. Cultured hUECs, hBPCs and hEFs were mitotically inactivated and then plated. hESCs (Miz-hES1, NIH registered) initially established on mouse feeder layers were transferred onto each human feeder layer and split every 5 days. The morphology, expression of specific markers and differentiation capacity of hESCs adapted on each human feeder layer were examined. On hUEC, hBPC and hEF feeder layers, hESCs proliferated for more than 90, 50 and 80 passages respectively. Human feeder-based hESCs were positive for stage-specific embryonic antigen (SSEA)-3 and -4, and Apase; they also showed similar differentiation capacity to MEF-based hESCs, as assessed by the formation of teratomas and expression of tissue-specific markers. However, hESCs cultured on hUEC and hEF feeders were slightly thinner and flatter than MEF- or hBPC-based hESCs. Our results suggest that, like MEF feeder layers, human feeder layers can support the proliferation of hESCs without differentiation. Human feeder cells have the advantage of supporting more passages than when MEFs are used as feeder cells, because hESCs can be uniformly maintained in the undifferentiated stage until they pass through senescence. hESCs established and/or maintained under stable xeno-free culture conditions will be helpful to cell-based therapy.

Adult↗

Neuronal differentiation of cryopreserved neural progenitor cells derived from mouse embryonic stem cells.

Embryonic stem cells (ES cells) are developmentally pluripotent cells isolated from pre-implantation mammalian embryos. In cell culture ES cells can be easily differentiated to generate cultures of neural progenitors. We present a simple method for the cryopreservation of these ES-derived neural progenitors. Cryopreserved neural progenitor stocks can be thawed, expanded with FGF2, and differentiated into functional neurons. This method will facilitate studies using ES-derived neural progenitor cells as a cell culture model system for neural development and differentiation. It will also aid studies designed to test the ability of these progenitor cells to functionally engraft and repair damaged neural tissue.

Animals↗

Flk1+ cells derived from mouse embryonic stem cells reconstitute hematopoiesis in vivo in SCID mice.

OBJECTIVE: Embryonic stem (ES) cells are pluripotent and can differentiate into any cell type, including the hematopoietic lineage. We examined whether hematopoietic progenitor cells derived from ES cells reconstitute hematopoiesis in irradiated SCID mice. MATERIALS AND METHODS: ES cells (E14.1, H2K(b)) were cultured for 4 days in semisolid medium containing methylcellulose. Irradiated SCID mice were used as recipients of hematopoietic progenitor cells. Cell surface antigen expression was analyzed by flow cytometry. The spleens of the recipient mice were studied by hematoxylin and eosin staining and immunohistochemical staining. RESULTS: After cell culture of ES cells in methylcellulose for 4 days, the cells expressing Flk1 (VEGF receptor 2), a tentative marker of hemangioblasts, were increased, whereas cells expressing CD31 (PECAM-1) and E-cadherin (nonmesodermal adhesion molecule) were dramatically reduced. Flk1+ cells expressed c-kit predominantly. Circulating leukocytes and thrombocytes were increased in irradiated SCID (H2K(d)) mice transplanted with ES cell-derived Flk1+ cells compared with vehicle-injected control mice. H2K(b+) and VE-cadherin(+) vascular endothelial cells were prominent in spleens of the recipient mice. Flow cytometric analysis demonstrated that H2K(b+) cells were increased in the bone marrow of recipient mice. In addition, Flk1+ cells accompanying enhanced c-kit expression preferentially repopulated in the bone marrow, and leukopoiesis and thrombopoiesis of the recipient mice were evident. CONCLUSION: The Flk1+ hematopoietic cells derived from ES cells reconstitute hematopoiesis in vivo and may become an alternative donor source for bone marrow transplantation.

Animals↗

Modulation of hematopoietic and endothelial cell differentiation from mouse embryonic stem cells by different culture conditions.

Embryonic stem (ES) cells can differentiate into many different somatic cells in culture. To better correlate hematopoietic and endothelial cell differentiation of ES cells in currently available protocols, we compared fetal liver kinase-1 (Flk-1)-, stem cell leukemia (Scl)-, and vascular endothelial-cadherin (VE-cadherin)-expressing cells generated in embryoid bodies (EBs) and on OP9 cells. We report that the kinetics of Scl and Flk-1 expression were similar in EBs and OP9 cells, although Flk-1 expression was extended on OP9 cells. CD45+ and Ter-119+ cells developed more efficiently in EBs, whereas VE-cadherin+ cells developed largely on OP9 cells. Cell sorting and replating studies showed that Scl+ cells, not Flk-1+ or VE-cadherin+ cells, were enriched for primitive and definitive hematopoietic progenitors. Our studies indicate that optimal hematopoietic and endothelial cell differentiation occur in EBs and on OP9 cells, respectively. Regardless of the culture systems used, Scl is the most relevant marker for enriching primitive and definitive hematopoietic progenitors.

Animals↗

[Immortalization of endothelial cells differentiated from mouse embryonic stem cells].

This study is designed to immortalize endothelial cells differentiated from embryonic stem cells. The embryoid bodies (EB) formed in vitro from embryonic stem cells, were induced to differentiate into many "round cells" (the precursor of endothelial cells) by retinoic acid (RA) and transforming growth factor-beta1 (TGF-beta1). These "round cells" later formed the vascular tube-like structures. Studies by scanning electronic microscopy and light microscopy and immunocytochemistry, demonstrated that these tube-like structures were constituted by a large number of round and flat cells, which were positive for "vWF" and "CD34"staining. These results indicate they are vascular endothelial cells. To immortalize these cells, human telomerase reverse transcriptase (hTERT) cDNA was transfected into "round cells" by lipofectine. hTERT mRNA expression in transfected cells was confirmed by Dot blot, RT-PCR. Furthermore, 95% these transfected cells maintain the characteristic of endothelial cell, can proliferate in large quantity in vitro, and are able to form tubular structures. These results suggest that hTERT cDNA transfection can immortalize the induced endothelial cells and therefore may provide a new source of seed cells for vascular engineering.

Animals↗

Specification of the retinal fate of mouse embryonic stem cells by ectopic expression of Rx/rax, a homeobox gene.

With the goal of generating retinal cells from mouse embryonic stem (ES) cells by exogenous gene transfer, we introduced the Rx/rax transcription factor, which is expressed in immature retinal cells, into feeder-free mouse ES cells (CCE). CCE cells expressing Rx/rax as well as enhanced green fluorescent protein (CCE-RX/E cells) proliferated and remained in the undifferentiated state in the presence of leukemia inhibitory factor, as did parental ES cells. We made use of mouse embryo retinal explant cultures to address the differentiation ability of grafted ES cells. Dissociated embryoid bodies were treated with retinoic acid for use as donor cells and cocultured with retina explants for 2 weeks. In contrast to the parental CCE cells, which could not migrate into host retinal cultures, CCE-RX/E cells migrated into the host retina and extended their process-like structures between the host retinal cells. Most of the grafted CCE-RX/E cells became located in the ganglion cell and inner plexiform layers and expressed ganglion and horizontal cell markers. Furthermore, these grafted cells had the electrophysiological properties expected of ganglion cells. Our data thus suggest that subpopulations of retinal neurons can be generated in retinal explant cultures from grafted mouse ES cells ectopically expressing the transcription factor Rx/rax.

Animals↗

Serological characterization of a pluripotent mouse embryonal stem cell line, two transformed derivatives, and an endoderm-like cell line.

The pluripotent mouse embryonal stem cell line BLC 1 and two transformants derived from it by DNA transformation (T1 and T2/K26) as well as the blastocyst-derived cell line BLC 3 were tested for the presence of cell surface antigens recognized by the monoclonal antibodies ECMA-7, anti-SSEA-1 and M 1/22.25, and intermediate filament proteins labeled by the monoclonal antibodies TROMA 1 and TROMA 2 using a three-step indirect immunofluorescence technique. According to present concepts and in agreement with previous data (Wobus et al., 1984a), the results obtained indicate that BLC 1, T1 and T2/K26 are undifferentiated embryonal stem cells, and BLC 3 is an endoderm-like cell line.

Animals↗

Control of mouse U1 snRNA gene expression during in vitro differentiation of mouse embryonic stem cells.

Early in mouse development, two classes of U1 RNAs, mU1a and mU1b, are synthesized, but as development proceeds, transcription of the embryo-specific mU1b genes is selectively down-regulated to a barely detectable level. We show here that during in vitro differentiation of mouse embryonic stem (ES) cells, both exogenously introduced and endogenous U1b genes are subject to normal developmental regulation. Thus, ES cells represent a convenient isogenic system for studying the control of expression of developmentally regulated snRNA genes. Using this system, we have identified a region in the proximal 5'flanking region, located outside the PSE element, that is responsible for differential transcription of the mU1a and mU1b genes in both developing cells and transiently transfected NIH 3T3 cells.

3T3 Cells↗