Induction of oocyte-like cells from mouse embryonic stem cells by co-culture with ovarian granulosa cells

Abstract In vitro derivation of oocytes from embryonic stem (ES) cells has the potential to be an important tool for studying oogenesis as well as advancing the field of therapeutic cloning by providing an alternative source of oocytes. Here, we demonstrate a novel, two-step method for inducing mouse ES cells to differentiate into oocyte-like cells using mouse ovarian granulosa cells. First, primordial germ cells (PGCs) were differentiated within the embryonic body (EB) cells around day 4 as defined by the expression of PGC-specific markers and were distinguished from undifferentiated ES cells. Second, day 4 EB cells were co-cultured with ovarian granulosa cells. After 10 days, these cells formed germ cell colonies as indicated by the expression of the two germ cell markers Mvh and SCP3. These cells also expressed the oocyte-specific genes Fig α, GDF-9 , and ZP1-3 but not any testis-specific genes by RT-PCR analysis. EB cultured alone or cultured in granulosa cell-conditioned medium did not express any of these oocyte-specific markers. In addition, EB co-cultured with Chinese hamster ovary (CHO) cells or cultured in CHO cell-conditioned medium did not express all of these oocyte-specific markers. Immunocytochemistry analysis using Mvh and GDF-9 antibodies confirmed that some Mvh and GDF-9 double-positive oocyte-like cells were generated within the germ cell colonies. Our results demonstrate that granulosa cells were effective in inducing the differentiation of ES cell-derived PGCs into oocyte-like cells through direct cell-to-cell contacts. Our method offers a novel in vitro system for studying oogenesis; in particular, for studying the interactions between PGCs and granulosa cells.     

Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors

Differentiated cells can be reprogrammed to an embryonic-like state by transfer of nuclear contents into oocytes or by fusion with embryonic stem (ES) cells. Little is known about factors that induce this reprogramming. Here, we demonstrate induction of pluripotent stem cells from mouse embryonic or adult fibroblasts by introducing four factors, Oct3/4, Sox2, c-Myc, and Klf4, under ES cell culture conditions. Unexpectedly, Nanog was dispensable. These cells, which we designated iPS (induced pluripotent stem) cells, exhibit the morphology and growth properties of ES cells and express ES cell marker genes. Subcutaneous transplantation of iPS cells into nude mice resulted in tumors containing a variety of tissues from all three germ layers. Following injection into blastocysts, iPS cells contributed to mouse embryonic development. These data demonstrate that pluripotent stem cells can be directly generated from fibroblast cultures by the addition of only a few defined factors.     

Chondrocytes derived from mouse embryonic stem cells

Our knowledge of cellular differentiation processes during chondro- and osteogenesis, in particular the complex interaction of differentiation factors, is still limited. We used the model system of embryonic stem (ES) cell differentiation in vitro via cellular aggregates, so called embryoid bodies (EBs), to analyze chondrogenic and osteogenic differentiation. ES cells differentiated into chondrocytes and osteocytes throughout a series of developmental stages resembling cellular differentiation events during skeletal development in vivo. A lineage from pluripotent ES cells via mesenchymal, prechondrogenic cells, chondrocytes and hypertrophicchondrocytes up to osteogenic cells was characterized. Furthermore, we found evidence for another osteogenic lineage, bypassing the chondrogenic stage. Together our results suggest that this in vitro system will be helpful to answer so far unacknowledged questions regarding chondrogenic and osteogenic differentiation. For example, we isolated an as yet unknown cDNA fragment from ES cell-derived chondrocytes, which showed a developmentally regulated expression pattern during EB differentiation. Considering ES cell differentiation as an alternative approach for cellular therapy, we used two different methods to obtain pure chondrocyte cultures from the heterogenous EBs. First, members of the transforming growth factor (TGF)-β family were applied and found to modulate chondrogenic differentiation but were not effective enough to produce sufficient amounts of chondrocytes. Second, chondrocytes were isolated from EBs by micro-manipulation. These cells initially showed dedifferentiation into fiboblastoid cells in culture, but later redifferentiated into mature chondrocytes. However, a small amount of chondrocytes isolated from EBs transdifferentiated into other mesenchymal cell types, indicating that chondrocytes derived from ES cells posses a distinct differentiation plasticity. This revised version was published online in July 2006 with corrections to the Cover Date.     

Generation of insulin-expressing cells from mouse embryonic stem cells

The therapeutic potential of transplantation of insulin-secreting pancreatic beta-cells has stimulated interest in using pluripotent embryonic stem (ES) cells as a starting material from which to generate insulin secreting cells in vitro. Mature beta-cells are endodermal in origin so most reported differentiation protocols rely on the identification of endoderm-specific markers. However, endoderm development is an early event in embryogenesis that produces cells destined for the gut and associated organs in the embryo, and for the development of extra-embryonic structures such as the yolk sac. We have demonstrated that mouse ES cells readily differentiate into extra-embryonic endoderm in vitro, and that these cell populations express the insulin gene and other functional elements associated with beta-cells. We suggest that the insulin-expressing cells generated in this and other studies are not authentic pancreatic beta-cells, but may be of extra-embryonic endodermal origin.     

Induction of pluripotency in mammalian fibroblasts by cell fusion with mouse embryonic stem cells

BackgroundCell fusion is a phenomenon that is observed in various tissues in vivo, resulting in acquisition of physiological functions such as liver regeneration. Fused cells such as hybridomas have also been produced artificially in vitro. Furthermore, it has been reported that cellular reprogramming can be induced by cell fusion with stem cells.MethodsFused cells between mammalian fibroblasts and mouse embryonic stem cells were produced by electrofusion methods. The phenotypes of each cell lines were analyzed after purifying the fused cells.ResultsColonies which are morphologically similar to mouse embryonic stem cells were observed in fused cells of rabbit, bovine, and zebra fibroblasts. RT-PCR analysis revealed that specific pluripotent marker genes that were never expressed in each mammalian fibroblast were strongly induced in the fused cells, which indicated that fusion with mouse embryonic stem cells can trigger reprogramming and acquisition of pluripotency in various mammalian somatic cells.ConclusionsOur results can help elucidate the mechanism of pluripotency maintenance and the establishment of highly reprogrammed pluripotent stem cells in various mammalian species.     

Directed differentiation of dendritic cells from mouse embryonic stem cells

Dendritic cells (DCs) are uniquely capable of presenting antigen to naive T cells, either eliciting immunity [1] or ensuring self-tolerance [2]. This property identifies DCs as potential candidates for enhancing responses to foreign [3] and tumour antigens [4], and as targets for immune intervention in the treatment of autoimmunity and allograft rejection [1]. Realisation of their therapeutic potential would be greatly facilitated by a fuller understanding of the function of DC-specific genes, a goal that has frequently proven elusive because of the paucity of stable lines of DCs that retain their unique properties, and the inherent resistance of primary DCs to genetic modification. Protocols for the genetic manipulation of embryonic stem (ES) cells are, by contrast, well established [5], as is their capacity to differentiate into a wide variety of cell types in vitro, including many of hematopoietic origin [6]. Here, we report the establishment, from mouse ES cells, of long-term cultures of immature DCs that share many characteristics with macrophages, but acquire, upon maturation, the allostimulatory capacity and surface phenotype of classical DCs, including expression of CD11c, major histocompatibility complex (MHC) class II and co-stimulatory molecules. This novel source should prove valuable for the generation of primary, untransformed DCs in which candidate genes have been overexpressed or functionally ablated, while providing insights into the earliest stages of DC ontogeny.     

Cloned transgenic mouse fetuses from embryonic stem cells

Development of efficient efficient system for genetic modification and large-scale cloning of livestock is of importance for agriculture, biotechnology, or human medicine. The mouse, on the other hand, is an ideal model in the basic studies of genetic modification. In this study, we investigated about production of clone mice from established embryonic stem (ES) cell line by nuclear transfer. Further, we had try of production of cloned transgenic mouse fetuses/offspring using ES cells modified with a marker gene, EGFP. With the ES cell line TT2 which is at least 15 passages, reconstructed oocytes developed to 2-8 cell embryos, morulae, or blastocysts (44.8%), and 17.2% of them developed to term (19.5 days post-coitum, dpc). When 40 embryos with the marker gene transferred to 11 surrogate mothers (pseudopregnant females), 5 live fetuses were recognized in the uteli at 13.5 dpc and in these fetuses expression of GFP was observed, but none developed beyond 19.5 dpc. The present results suggest that ES cells can be used tg produce cloned mice.     

小鼠胚胎干细胞分化为血管内皮细胞的永生化研究

本文探讨了小鼠胚胎干细胞（ES细胞）、诱导分化的血管内皮细胞永生化。在体外培养系统中,以维甲酸（RA）和转化生长因子－β1（TGF－β1）诱导小鼠胚胎干细胞（ES细胞）的拟胚体（EB）分化为“圆形细胞”和由这些“圆形细胞”组成的血管样结构。经光学和扫描电镜及免疫荧光等法分析检测,证明组成血管样结构的细胞具有专一性vWF荧光染色,表明是血管内皮样细胞。利用脂质体将人端粒酶催化亚基逆转录酶（hTERT)基因转染诱导分化中的“圆形细胞”。应用Dot-blot,RT－PCR,Western blot及免疫组织化学等方法分析、观察和证明了诱导分化的组成血管样结构的园形细胞和被hTERT基因转染的“圆形”细胞的形态和生物学特性。结果表明,携带hTERT基因的从ES细胞分化来的圆形细胞在体外可大量增殖,持续传代,95％具有血管内皮细胞的一些特有标志和管道化生长特征。因此,通过人端粒酶基因的转染途径可解决由ES细胞诱导分化而来的内皮细胞扩增和永生化问题,为构建组织工程化血管及其它人工血管的内皮化提供种子细胞来源打下基础。     

Induction of melanocytes from embryonic stem cells and their therapeutic potential

Embryonic stem (ES) cells from many organisms have the capacity to generate in vitro a wide variety of cell types depending on their environment. Understanding precisely how such toti- or pluripotent cells may be driven towards a specific lineage represents a major challenge if our ambition of using ES cells to generate a ready supply of healthy cells for cell-based therapies for a range of diseases is to be realized. Recent advances have demonstrated that melanocytes and retinal pigmented epithelial (RPE) cells exhibiting the characteristics of their natural counterparts can be induced from undifferentiated ES cells grown on monolayers of specific stromal cell lines or by using a combination of Wnt3a, Endothelin-3 and SCF. The ability to induce pigment cells from ES cells promises to facilitate our understanding of the precise molecular mechanisms underlying this process and moreover enable us to distinguish the program of gene expression that underpins the choice made between generating a nerual crest-type melanocyte versus an RPE cell. Moreover, once the combination of signals required to induce a particular type of pigment cell are characterized, the way may be open for future cell-based therapy for various diseases caused by defective pigment cells.     

Generation of lung epithelial-like tissue from human embryonic stem cells

Background

Human embryonic stem cells (hESC) have the capacity to differentiate in vivo and in vitro into cells from all three germ lineages. The aim of the present study was to investigate the effect of specific culture conditions on the differentiation of hESC into lung epithelial cells.

Methods

Undifferentiated hESC, grown on a porous membrane in hESC medium for four days, were switched to a differentiation medium for four days; this was followed by culture in air-liquid interface conditions during another 20 days. Expression of several lung markers was measured by immunohistochemistry and by quantitative real-time RT-PCR at four different time points throughout the differentiation and compared to appropriate controls.

Results

Expression of CC16 and NKX2.1 showed a 1,000- and 10,000- fold increase at day 10 of differentiation. Other lung markers such as SP-C and Aquaporin 5 had the highest expression after twenty days of culture, as well as two markers for ciliated cells, FOXJ1 and β-tubulin IV. The results from qRT-PCR were confirmed by immunohistochemistry on paraffin-embedded samples. Antibodies against CC16, SP-A and SP-C were chosen as specific markers for Clara Cells and alveolar type II cells. The functionality was tested by measuring the secretion of CC16 in the medium using an enzyme immunoassay.

Conclusion

These results suggest that by using our novel culture protocol hESC can be differentiated into the major cell types of lung epithelial tissue.     

Stable propagation of human embryonic and induced pluripotent stem cells on decellularized human substrates

Human pluripotent stem cells (hPSCs) that include human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) have gained enormous interest as potential sources for regenerative biomedical therapies and model systems for studying early development. Traditionally, mouse embryonic fibroblasts have been used as a supportive feeder layer for the sustained propagation of hPSCs. However, the use of nonhuman‐derived feeders presents concerns about the possibility of xenogenic contamination, labor intensiveness, and variability in experimental results in hPSC cultures. Toward addressing some of these concerns, we report the propagation of three different hPSCs on feeder‐free extracellular matrix (ECM)‐based substrates derived from human fibroblasts. hPSCs propagated in this setting were indistinguishable by multiple criteria, including colony morphology, expression of pluripotency protein markers, trilineage in vitro differentiation, and gene expression patterns, from hPSCs cultured directly on a fibroblast feeder layer. Further, hPSCs maintained a normal karyotype when analyzed after 15 passages in this setting. Development of this ECM‐based culture system is a significant advance in hPSC propagation methods as it could serve as a critical component in the development of humanized propagation systems for the production of stable hPSCs and its derivatives for research and therapeutic applications. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Mutator phenotype of MUTYH-null mouse embryonic stem cells

To evaluate the antimutagenic role of a mammalian mutY homolog, namely the Mutyh gene, which encodes adenine DNA glycosylase excising adenine misincorporated opposite 8-oxoguanine in the template DNA, we generated MUTYH-null mouse embryonic stem (ES) cells. In the MUTYH-null cells carrying no adenine DNA glycosylase activity, the spontaneous mutation rate increased 2-fold in comparison with wild type cells. The expression of wild type mMUTYH or mutant mMUTYH protein with amino acid substitutions at the proliferating cell nuclear antigen binding motif restored the increased spontaneous mutation rates of the MUTYH-null ES cells to the wild type level. The expression of a mutant mMUTYH protein with an amino acid substitution (G365D) that corresponds to a germ-line mutation (G382D) found in patients with multiple colorectal adenomas could not suppress the elevated spontaneous mutation rate of the MUTYH-null ES cells. Although the recombinant mMUTYH(G365D) purified from Escherichia coli cells had a substantial level of adenine DNA glycosylase activity as did wild type MUTYH, no adenine DNA glycosylase activity was detected in the MUTYH-null ES cells expressing the mMUTYH(G365D) mutant protein. The germ-line mutation (G382D) of the human MUTYH gene is therefore likely to be responsible for the occurrence of a mutator phenotype in these patients.     

Metastable primordial germ cell-like state induced from mouse embryonic stem cells by Akt activation

Specification to primordial germ cells (PGCs) is mediated by mesoderm-induction signals during gastrulation. We found that Akt activation during in vitro mesodermal differentiation of embryonic stem cells (ESCs) generated self-renewing spheres with differentiation states between those of ESCs and PGCs. Essential regulators for PGC specification and their downstream germ cell-specific genes were expressed in the spheres, indicating that the sphere cells had commenced differentiation to the germ lineage. However, the spheres did not proceed to spermatogenesis after transplantation into testes. Sphere cell transfer to the original feeder-free ESC cultures resulted in chaotic differentiation. In contrast, when the spheres were cultured on mouse embryonic fibroblasts or in the presence of ERK-cascade and GSK3 inhibitors, reversion to the ESC-like state was observed. These results indicate that Akt signaling promotes a novel metastable and pluripotent state that is intermediate to those of ESCs and PGCs.     

Multicolor karyotype analyses of mouse embryonic stem cells

Summary The manipulation of embryonic stem (ES) cells to introduce directional genetic changes into the genome of mice has become an important tool in biomedical research. Monitoring of cell morphology before and after DNA manipulation and special culture conditions are a prerequisite to preserve the pluripotent properties of ES cells and thus their ability to generate chimera and effective germline transmission (GLT). It has been reported that prolonged cell culturing may affect the diploid chromosomal composition of cells and therefore the percentage of chimerism and GLT. Herein, we report multicolor-fluorescence in situ hybridization (M-FISH) analysis of four different ES cell lines/clones. Although the morphology of all four ES cell lines/clones appeared normal and all four expressed the early markers Oct-3/4 and Nanog, two cell lines presented consistent numerical and structural chromosome aberrations. We demonstrate that M-FISH is a sensitive and accurate method for a comprehensive karyotype analysis of ES cells and may minimize time, costs, and disappointment due to inadequate ES cell sources. Both authors contributed equally to this work.