New method for forming large embryoid bodies using the wall of the culture dish along with an analysis of their structural characteristics

Early embryonic stem (EES) cells, which were established from 2 cell stage embryos obtained from ddY mice, had similar characteristics as embryonic stem (ES) cells. These cells were maintained in an undifferentiated stage in growth media supplemented with leukemia inhibitory factor (LIF) and were capable of differentiating into triploblastic tissues under various growth factors. It has been known that normal sized embryoid bodies (EBs) are formed by removing LIF. In this study, large EBs gradually formed along the side wall of a culture dish, particularly at the boundary between the air and the growth medium when cells were cultured for a considerable period of time and without subculturing. We call this method the “wall adhesion culture” procedure. The method itself is simple and do not need any instruments except plastic dishes because only the side walls of the dishes were utilized. The mean thickness of the large EBs was about 1.5 mm 3 months after establishing the static culture. Their surface was covered with a monolayer of cells and they contained an eosinophilic cell matrix. By electron microscopy, some characteristic structures was observed, such as intracisternal A particles which were present inside the swelling of the rough endoplasmic reticulum. Since many tissues derived from ES cells are obtained through EBs, it is expected that efficient acquisition of sufficient quantities of these structures using the wall adhesion culture procedure will be a shortcut for using ES cells in regenerative medicine.     

长期培养小鼠胚胎干细胞拟胚体(EB)的观察

胚胎干细胞在体外培养条件下能够维持自我更新,并具有向多种细胞类型分化的能力,因此被广泛用于研究细胞分化的分子机理以及药物筛选.形成拟胚体(Embryoid body,EB)是胚胎干细胞分化常用的技术手段.为了便于今后利用EB做进一步的药物筛选及分化研究,严格规范了形成EB的条件,得到了分化状态均一性很高的EB.利用这一条件,观察到在分化条件下长期培养(长达60 d)的EB中仍有表达各项多能性指标的细胞集落.有关这一现象的进一步分析工作正在进行中.     

Embryoid bodies formation and differentiation from mouse embryonic stem cells in collagen/Matrigel scaffolds

Embryonic stem (ES) cells have the potential to develop into any type of tissue and are considered as a promising source of seeding cells for tissue engineering and transplantation therapy. The main catalyst for ES cells differentiation is the growth into embryoid bodies (EBs), which are utilized widely as the trigger of in vitro differentiation. In this study, a novel method for generating EBs from mouse ES cells through culture in collagen/Matrigel scaffolds was successfully established. When single ES cells were seeded in three dimensional collagen/Matrigel scaffolds, they grew into aggregates gradually and formed simple EBs with circular structures. After 7 days' culture,they formed into cystic EBs that would eventually differentiate into the three embryonic germ layers. Evaluation of the EBs in terms of morphology and potential to differentiate indicated that they were typical in structure and could generate various cell types; they were also able to form into tissue-like structures. Moreover, with introduction of ascorbic acid, ES cells differentiated into cardiomyocytes efficiently and started contracting synchronously at day 19. The results demonstrated that collagen/Matrigel scaffolds supported EBs formarion and their subsequent differentiation in a single three dimensional environment.     

New approach for the establishment of mouse early embryonic stem cells and induction of their differentiation

Eleven early embryonic stem (EES) cell lines were established using a new novel method. Two cell stage embryos from the ddY mouse strain were cultured in alpha-MEM supplemented with 10% fetal calf serum (FCS) and embryotrophic factors (ETFs) and allowed to develop to the trilaminal germ disc embryonic stage. Only small round cells (EES cells) were isolated by the colony isolating technique and subsequently cultured in the same medium containing the ETFs and leukemia inhibitory factors (LIF-10 ng/ml). The newly established embryonic stem (ES) cells isolated from inner cell mass of blastocysts differentiated from two cell stage embryo in culture. The EES and ES cell lines were maintained in an undifferentiated state using Ham's F12 medium supplemented with 10% FCS and 1 ng/ml of LIF. The EES cells maintained their normal genetic and morphological features as well as their potential to differentiate into a broad spectrum of cell types as well as their ability to contribute to all cell lineages in chimeric mice. Moreover, these cell lines changed and differentiated into various kinds of cells by removing LIF and by the addition of ETFs to the vitro culture system. All 11 EES cell lines and 3 ES cell lines formed embryoid bodies; however, cell line EES-4 formed tube-like structures which extended, anastomosed with each other, and finally formed networks when the LIF were absent. Primitive germ organ-like structures composed of 3 germ layers were recognized in the cultures following the administration of ETFs. In conclusion, the new method devised by us is a novel, easy and reliable technique for establishing EES cell lines.     

Cryopreservation of mouse embryoid bodies

Cryopreservation of embryonic stem (ES) cells is essential to establish them as a resource for regenerative therapy. We evaluated survival adhesion rate, cell structure, gene expression, and multipotency of frozen and thawed embryoid bodies (EBs) derived from mouse ES cells. EBs were cryopreserved using the BICELL and the Program Freezer. After one week the EBs were thawed and cultured. EBs prepared in the Program Freezer had the highest survival adhesion (Program Freezer; 55-69%, BICELL; 30-38%). Though many cells in the thawed EBs were damaged, some were not, especially those prepared in the Program Freezer. RT-PCR analysis showed that genes characteristic of the three embryonic germ layers were expressed in thawed EBs cultured for one week. EBs transplanted into mice formed teratomas consisting of cells derived from the three germ layers. In conclusion, EBs frozen in the Program Freezer had higher survival adhesion rates compared to the BICELL and formed differentiated cells characteristic of the three embryonic germ layers.     

Generation of embryoid bodies from mouse embryonic stem cells cultured on STO feeder cells

Embryoid bodies, which are similar to post-implantation egg-cylinder stage embryos, provide a model for the study of embryo development and stem cell differentiation. We describe here a novel method for generating embryoid bodies from murine embryonic stem (ES) cells cultured on the STO feeder layer. The ES cells grew into compact aggregates in the first 3 days of coculture, then became simple embryoid bodies (EBs) possessing primitive endoderm on the outer layer. They finally turned into cystic embryoid bodies after being transferred to Petri dishes for 1-3 days. Evaluation of the EBs in terms of morphology and differentiating potential indicates that they were typical in structure and could generate cells derived from the three germ layers. The results show that embryoid bodies can form not only in suspension culture but also directly from ES cells cultured on the STO feeder layer.     

An improved protocol that induces human embryonic stem cells to differentiate into neural cells in vitro

Human embryonic stem (ES) cells have the capacity for self-renewal and are able to differentiate into any cell type. However, obtaining high-efficient neural differentiation from human ES cells remains a challenge. This study describes an improved 4-stage protocol to induce a human ES cell line derived from a Chinese population to differentiate into neural cells. At the first stage, embryonic bodies (EBs) were formed in a chemically-defined neural inducing medium rather than in traditional serum or serum-replacement medium. At the second stage, rosette-like structures were formed. At the third stage, the rosette-like structures were manually selected rather than enzymatically digested to form floating neurospheres. At the fourth stage, the neurospheres were further differentiated into neurons. The results show that, at the second stage, the rate of the formation of rosette-like structures from EBs induced by noggin was 88+/-6.32%, higher than that of retinoic acid 55+/-5.27%. Immunocytochemistry staining was used to confirm the neural identity of the cells. These results show a major improvement in obtaining efficient neural differentiation of human ES cells.     

LIF基因转染的ES细胞生长与分化特性的研究

我们将人D型LIF cDNA以正反两种方向分别克隆到载体pKCR 3,并引入neo~r基因,构建成pSVLD( )和pSVLD(-)质粒,按磷酸钙沉淀法分别转染ES-5胚胎干细胞,经G418和不同浓度LIF条件培液共同筛选、Nor-thern和Southern分析以及ES-5细胞集落分化抑制能力测定,建立了过度表达分泌LIF的ESL( )细胞株和表达外源反义LIF RNA的ESL(-)细胞株。我们发现,ESL( )A2细胞能够在无外源LIF常规培液下至少传13代以上,仍能正常生长和传代,并保持与ES-5细胞同样的体外生长的特征性形态,以及具有干细胞特点和发育多潜能性,表明过度表达LIF确实能使ES细胞完全脱离对外源LIF条件培液的依赖性;而表达反义LIP RNA的ESL(-)细胞对培液中LIF浓度的依赖性明显升高,也更易分化,说明ES细胞内源LIF基因的表达水平虽低,但对于抑制ES细胞的分化仍可能是必需的。形态学观察发现,体外悬滴培养中经10~(-6)mol/L RA诱导后,过度表达LIF并未产生抑制ESL( )A2细胞分化的现象,和亲本ES-5细胞比较,也未发现其明显改变了10~(-6)mol/L RA对ESL( )A2细胞诱导分化的方向;而相同条件下,表达外源反义LIF RNA,则使ESL(-)B5细胞更易于向形态明确的细胞包括成纤维样和梭样细胞分化。上述细胞株的建立,提供了一个研究在不添加LIF的常规培液中生长的ES细胞或表达外源反义LIF RNA的ES细胞的生长分化的模型。     

Gene expression profiles during early differentiation of mouse embryonic stem cells

Background  

Understanding the mechanisms controlling stem cell differentiation is the key to future advances in tissue and organ regeneration. Embryonic stem (ES) cell differentiation can be triggered by embryoid body (EB) formation, which involves ES cell aggregation in suspension. EB growth in the absence of leukaemia inhibitory factor (LIF) leads EBs to mimic early embryonic development, giving rise to markers representative of endoderm, mesoderm and ectoderm. Here, we have used microarrays to investigate differences in gene expression between 3 undifferentiated ES cell lines, and also between undifferentiated ES cells and Day 1–4 EBs     

Supplementation-dependent differences in the rates of embryonic stem cell self-renewal, differentiation, and apoptosis

Although it is known that leukemia inhibitory factor (LIF) supports the derivation and expansion of murine embryonic stem (ES) cells, it is unclear whether this is due to inhibitory effects of LIF on ES cell differentiation or stimulatory effects on ES cell survival and proliferation. Using an ES cell line transgenic for green fluorescent protein (GFP) expression under control of the Oct4 promoter, we were able to simultaneously track the responses of live Oct4-GFP-positive (ES) and -negative (differentiated) fractions to LIF, serum, and other growth factors. Our findings show that, in addition to inhibiting differentiation of undifferentiated cells, the administration of LIF resulted in a distinct dose-dependent survival and proliferation advantage, thus enabling the long-term propagation of undifferentiated cells. Competitive responses from the differentiated cell fraction could only be elicited upon addition of serum, fibroblast growth factor-4 (FGF-4), or insulin-like growth factor-1 (IGF-1). The growth factors did not induce additional differentiation of ES cells, but rather they significantly improved the proliferation of already differentiated cells. Our analyses show that, by adjusting culture conditions, including the type and amount of growth factors or cytokines present, the frequency of media exchange, and the presence or absence of serum, we could selectively and specifically alter the survival, proliferation, and differentiation dynamics of the two subpopulations, and thus effectively control population outputs. Our findings therefore have important applications in engineering stem cell culture systems to predictably generate desired stem cells or their derivatives for various regenerative therapies.     

Collagen-IV supported embryoid bodies formation and differentiation from buffalo (Bubalus bubalis) embryonic stem cells

Embryoid bodies (EBs) are used as in vitro model to study early extraembryonic tissue formation and differentiation. In this study, a novel method using three dimensional extracellular matrices for in vitro generation of EBs from buffalo embryonic stem (ES) cells and its differentiation potential by teratoma formation was successfully established. In vitro derived inner cell masses (ICMs) of hatched buffalo blastocyst were cultured on buffalo fetal fibroblast feeder layer for primary cell colony formation. For generation of EBs, pluripotent ES cells were seeded onto four different types of extracellular matrices viz; collagen-IV, laminin, fibronectin and matrigel using undifferentiating ES cell culture medium. After 5days of culture, ESCs gradually grew into aggregates and formed simple EBs having circular structures. Twenty-six days later, they formed cystic EBs over collagen matrix with higher EBs formation and greater proliferation rate as compared to other extracellular matrices. Studies involving histological observations, fluorescence microscopy and RT-PCR analysis of the in vivo developed teratoma revealed that presence of all the three germ layer derivatives viz. ectoderm (NCAM), mesoderm (Flk-1) and endoderm (AFP). In conclusion, the method described here demonstrates a simple and cost-effective way of generating EBs from buffalo ES cells. Collagen-IV matrix was found cytocompatible as it supported buffalo EBs formation, their subsequent differentiation could prove to be useful as promising candidate for ES cells based therapeutic applications.     

Establishment of a human embryonic germ cell line and comparison with mouse and human embryonic stem cells

Human embryonic stem (ES) cells and embryonic germ (EG) cells are pluripotent and are invaluable material for in vitro studies of human embryogenesis and cell therapy. So far, only two groups have reported the establishment of human EG cell lines, whereas at least five human ES cell lines have been established. To see if human EG cell lines can be reproducibly established, we isolated primordial germ cells (PGCs) from gonadal ridges and mesenteries (9 weeks post-fertilization) and cultured them on mouse STO cells. As with mouse ES colonies, the PGC-derived cells have given rise to multilayered colonies without any differentiation over a year of continuous culture. They are karyotypically normal and express high levels of alkaline phosphatase, Oct-4, and several cell-surface markers. Histological and immunocytochemical analysis of embryoid bodies (EBs) formed from floating cultures of the PGC-derived cell colonies revealed ectodermal, endodermal, and mesodermal tissues. When the EBs were cultured in the presence of insulin, transferrin, sodium selenite, and fibronectin for 1 week, markers of primitive neuroectoderm were expressed in cells within the EBs as well as in cells growing out from the EBs. These observations indicate that our PGC-derived cells satisfy the criteria for pluripotent stem cells and hence may be EG cells.     

Isolation and characterization of embryonic stem-like cells from canine blastocysts

Embryonic stem (ES) cells are pluripotent cells with the capacity to generate any type of cell. Here we describe the isolation of ES-like cells from canine blastocysts. Canine embryos were collected from beagle bitches at day 11-16 of first estrus. A total of 80 normal embryos were obtained from 15 dogs. Of the embryos, 13 were at the morulae stage, 39 at the blastocyst stage, and 28 at the hatched blastocyst stage. The inside of morulae or inner cell masses (ICMs) of blastocysts were isolated mechanically, and cultured onto mouse embryonic fibroblasts (MEF) as feeder layers. Primary cell colonies were formed in 0% (0/13) of morulae, 25.6% (10/39) of blastocysts, and 67.9% (19/28) of hatched blastocysts. These colonies were separated either by enzymatic dissociation or by mechanical disaggregation. Dissociation with collagenase resulted in immediate differentiation, but with mechanical disaggregation these cells remained undifferentiated, and two ES-like cell lines (cES1, cES2) continued to grow in culture after eight passages. These cells had typical stem cell-like morphology and expressed specific markers such as alkaline phosphatase activity, stage specific embryonic antigen-1 and Oct-4. These cells formed embryoid bodies (EBs) in a suspension culture; extended culture of EBs resulted in the formation of cystic EBs. When the simple EBs were cultured on tissue culture plates, they differentiated into several types of cells including neuron-like, epithelium-like, fibroblast-like, melanocyte-like, and myocardium-like cells. These observations indicate that we successfully isolated and characterized canine ES-like cells.     

Derivation and characterization of pluripotent embryonic germ cells in chicken

Embryonic germ (EG) cell lines established from primordial germ cells (PGCs) are undifferentiated and pluripotent stem cells. To date, EG cells with proven germ-line transmission have been completely established only in the mouse with embryonic stem (ES) cells. We isolated PGCs from 5.5-day-old (stage 28) chicken embryonic gonads and established a putative chicken EG cell line with EG culture medium supplemented with stem cell factor (SCF), leukemia inhibitory factor (LIF), basic fibroblast growth factor (bFGF), interleukin-11 (IL-11), and insulin-like growth factor-I (IGF-I). These cells grew continuously for ten passages (4 months) on a feeder layer of mitotically active chicken embryonic fibroblasts. After several passages, these cells were characterized by screening with the periodic acid-Schiff reaction, anti-SSEA-1 antibody, and a proliferation assay. The chicken EG cells maintained characteristics of gonadal PGCs and undifferentiated stem cells. When cultured in suspension, the chicken EG cells successfully formed an embryoid body and differentiated into a variety of cell types. The chicken EG cells were injected into stage X blastodermal layer and produced chimeric chickens with various differentiated tissues derived from the EG cells. Chicken EG cells will be useful for the production of transgenic chickens and for studies of germ cell differentiation and genomic imprinting.     

Formation of germ-line chimeras from embryonic stem cells maintained with recombinant leukemia inhibitory factor

Murine embryonic stem (ES) cells can be maintained as stem cells in vitro only in the presence of feeder cells or a soluble factor produced by a number of cell lines. We have previously demonstrated that leukemia inhibitory factor (LIF) is the molecule which prevents ES cell differentiation in culture. In this report we demonstrate that recombinant LIF can substitute for feeder cells in maintaining the full developmental potential of ES cells. The totipotent D3 ES cell line, previously isolated and maintained on growth-arrested primary embryo fibroblasts, was transferred to media supplemented with 1000 U/ml (10 ng/ml) recombinant LIF. In the presence of LIF the ES cells were maintained for over 2 months as undifferentiated cells in the absence of any feeder cells. When injected into blastocysts the ES cells which had been maintained in LIF-supplemented media efficiently formed germ-line chimeras.     

Differentiation of mouse embryonic stem cells to hepatocyte-like cells by co-culture with human liver nonparenchymal cell lines

This protocol describes a co-culture system for the in vitro differentiation of mouse embryonic stem cells into hepatocyte-like cells. Differentiation involves four steps: (i) formation of embryoid bodies (EB), (ii) induction of definitive endoderm from 2-d-old EBs, (iii) induction of hepatic progenitor cells and (iv) maturation into hepatocyte-like cells. Differentiation is completed by 16 d of culture. EBs are formed, and cells can be induced to differentiate into definitive endoderm by culture in Activin A and fibroblast growth factor 2 (FGF-2). Hepatic differentiation and maturation of cells is accomplished by withdrawal of Activin A and FGF-2 and by exposure to liver nonparenchymal cell-derived growth factors, a deleted variant of hepatocyte growth factor (dHGF) and dexamethasone. Approximately 70% of differentiated embryonic stem (ES) cells express albumin and can be recovered by albumin promoter-based cell sorting. The sorted cells produce albumin in culture and metabolize ammonia, lidocaine and diazepam at approximately two-thirds the rate of primary mouse hepatocytes.     

The SHB adapter protein is required for normal maturation of mesoderm during in vitro differentiation of embryonic stem cells

Definitive mesoderm arises from a bipotent mesendodermal population, and to study processes controlling its development at this stage, embryonic stem (ES) cells can be employed. SHB (Src homology 2 protein in beta-cells) is an adapter protein previously found to be involved in ES cell differentiation to mesoderm. To further study the role of SHB in this context, we have established ES cell lines deficient for one (SHB+/-) or both SHB alleles (SHB-/-). Differentiating embryoid bodies (EBs) derived from these ES cell lines were used for gene expression analysis. Alternatively, EBs were stained for the blood vessel marker CD31. For hematopoietic differentiation, EBs were differentiated in methylcellulose. SHB-/- EBs exhibited delayed down-regulation of the early mesodermal marker Brachyury. Later mesodermal markers relatively specific for the hematopoietic, vascular, and cardiac lineages were expressed at lower levels on day 6 or 8 of differentiation in EBs lacking SHB. The expression of vascular endothelial growth factor receptor-2 and fibroblast growth factor receptor-1 was also reduced in SHB-/- EBs. SHB-/- EBs demonstrated impaired blood vessel formation after vascular endothelial growth factor stimulation. In addition, the SHB-/- ES cells formed fewer blood cell colonies than SHB+/+ ES cells. It is concluded that SHB is required for appropriate hematopoietic and vascular differentiation and that delayed down-regulation of Brachyury expression may play a role in this context.     

Isolation and characterization of embryonic stem cell-like cells from in vitro-produced buffalo (Bubalus bubalis) embryos

This study was carried out to isolate and characterize buffalo embryonic stem (ES) cell-like cells from in vitro-produced embryos. Inner cell mass (ICM) cells were isolated either mechanically or by enzymatic digestion from 120 blastocysts whereas 28 morulae were used for the isolation of blastomeres mechanically. The ICM cells/ blastomeres were cultured on mitomycin-C-treated feeder layer. Primary cell colony formation was higher (P < 0.05) for hatched blastocysts (73.1%, 30/41) than that for early/expanded blastocysts (25.3%, 20/79). However, no primary cell colonies were formed when blastomeres obtained from morulae were cultured. Primary colonies were formed in 14.1% (12/85) of intact blastocyst culture, which was significantly lower (P < 0.05) than that of 41.6% for ICM culture. These colonies were separated by enzymatic or mechanical disaggregation. Using mechanical disaggregation method, the cells remained undifferentiated and two buffalo ES cell-like cell lines (bES1, bES2) continued to grow in culture up to eight passages. However, disassociation through enzymatic method resulted in differentiation. Undifferentiated cells exhibited stem cell morphological features, normal chromosomal morphology, and expressed specific markers such as alkaline phosphatase (AP) and Oct-4. Cells formed embryoid bodies (EBs) in suspension culture; extended culture of EBs resulted in formation of cystic EBs. Following prolonged in vitro culture, these cells differentiated into several types of cells including neuron-like and epithelium-like cells. Furthermore, the vitrified-thawed ES cell-like cells also exhibited typical stem cell characteristics. In conclusion, buffalo ES cell-like cells could be isolated from in vitro-produced blastocysts and maintained in vitro for prolonged periods of time.