Embryonic Stem Cell-like Colonies Research Articles

Semi-3D cultures using Laminin 221 as a coating material for human induced pluripotent stem cells.

It was previously believed that human induced pluripotent stem cells (hiPSCs) did not show adhesion to the coating material Laminin 221, which is known to have specific affinity for cardiomyocytes. In this study, we report that human mononuclear cell-derived hiPSCs, established with Sendai virus vector, form peninsular-like colonies rather than embryonic stem cell-like colonies; these peninsular-like colonies can be passaged more than 10 times after establishment. Additionally, initialization-deficient cells with residual Sendai virus vector adhered to the coating material Laminin 511 but not to Laminin 221. Therefore, the expression of undifferentiated markers tended to be higher in hiPSCs established on Laminin 221 than on Laminin 511. On Laminin 221, hiPSCs15M66 showed a semi-floating colony morphology. The expression of various markers of cell polarity was significantly lower in hiPSCs cultured on Laminin 221 than in hiPSCs cultured on Laminin 511. Furthermore, 201B7 and 15M66 hiPSCs showed 3D cardiomyocyte differentiation on Laminin 221. Thus, the coating material Laminin 221 provides semi-floating culture conditions for the establishment, culture and induced differentiation of hiPSCs.

Generation and characterization of human induced pluripotent stem cells (iPSCs) from hand osteoarthritis patient-derived fibroblasts

Knowledge and research results about hand osteoarthritis (hOA) are limited due to the lack of samples and animal models of the disease. Here, we report the generation of two induced pluripotent stem cell (iPSC)-lines from patients with radiographic hOA. Furthermore, we wondered whether these iPSC-lines carried single nucleotide polymorphisms (SNPs) within genes that have been associated with hOA. Finally, we performed chondrogenic differentiation of the iPSCs in order to prove their usefulness as cellular models of the disease. We performed a non-integrative reprogramming of dermal fibroblasts obtained from two patients with radiographic rhizarthrosis and non-erosive hOA by introducing the transcriptional factors Oct4, Sox2, Klf4 and c-Myc using Sendai virus. After reprogramming, embryonic stem cell-like colonies emerged in culture, which fulfilled all the criteria to be considered iPSCs. Both iPSC-lines carried variants associated with hOA in the four studied genes and showed differences in their chondrogenic capacity when compared with a healthy control iPSC-line. To our knowledge this is the first time that the generation of iPSC-lines from patients with rhizarthrosis and non-erosive hOA is reported. The obtained iPSC-lines might enable us to model the disease in vitro, and to deeper study both the molecular and cellular mechanisms underlying hOA.

Embryonic germ cell extracts erase imprinted genes and improve the efficiency of induced pluripotent stem cells

Patient-specific induced pluripotent stem cells (iPSCs) have the potential to be useful in the treatment of human diseases. While prior studies have reported multiple methods to generate iPSCs, DNA methylation continues to limit the totipotency and reprogramming efficiency of iPSCs. Here, we first show the competency of embryonic germ cells (EGCs) as a reprogramming catalyst capable of effectively promoting reprogramming induced by four defined factors, including Oct4, Sox2, Klf4 and c-Myc. Combining EGC extracts with these four factors resulted in formation of more embryonic stem cell-like colonies than did factors alone. Notably, expression of imprinted genes was higher with combined induction than with factors alone. Moreover, iPSCs derived from the combined inductors tended to have more global hypomethylation. Our research not only provides evidence that EGC extracts could activate DNA demethylation and reprogram imprinted genes, but also establishes a new way to enhance reprogramming of iPSCs, which remains a critical safety concern for potential use of iPSCs in regenerative medicine.

Abnormal Neural Progenitor Cells Differentiated from Induced Pluripotent Stem Cells Partially Mimicked Development of TSC2 Neurological Abnormalities.

SummaryTuberous sclerosis complex (TSC) is a disease featuring devastating and therapeutically challenging neurological abnormalities. However, there is a lack of specific neural progenitor cell models for TSC. Here, the pathology of TSC was studied using primitive neural stem cells (pNSCs) from a patient presenting a c.1444-2A>C mutation in TSC2. We found that TSC2 pNSCs had higher proliferative activity and increased PAX6 expression compared with those of control pNSCs. Neurons differentiated from TSC2 pNSCs showed enlargement of the soma, perturbed neurite outgrowth, and abnormal connections among cells. TSC2 astrocytes had increased saturation density and higher proliferative activity. Moreover, the activity of the mTOR pathway was enhanced in pNSCs and induced in neurons and astrocytes. Thus, our results suggested that TSC2 heterozygosity caused neurological malformations in pNSCs, indicating that its heterozygosity might be sufficient for the development of neurological abnormalities in patients.

Alpha-A-Crystallin Protects Lens Epithelial Cell-Derived iPSC-Like Cells Against Apoptosis Induced by Oxidative Stress.

Cataract, the leading cause of blindness worldwide, is caused by the apoptosis of lens epithelial cells (LECs). αA-crystallin is a major structural protein of the lens. However, the antiapoptotic function of αA-crystallin in lens stem cells remains unclear. In this study, primary LECs were isolated from postnatal 3-5 days of SD rats and transfected by Sendai virus loaded with four factors, OCT3/4, Sox2, c-Myc, and Klf4, to induced pluripotent stem cells (iPSCs). LEC-iPSC-like cells were identified by immunofluorescent staining. CryαA-specific shRNA lentivirus was used to knockdown αA-crystallin in LEC-derived iPSC-like cells, which were treated with tert-Butyl hydroperoxide. The apoptosis of LEC-iPSC-like cells was examined by flow cytometry. We reprogrammed LECs and obtained embryonic stem cell-like colonies. LEC-iPSC-like cells with normal karyotype expressed pluripotent markers such as SSEA-4, TRA-1-60, and TRA-1-81. Knockdown of αA-crystallin increased the apoptosis of LEC-iPSC-like cells and rendered them less resistant to oxidation stress induced by tert-Butyl hydroperoxide. In conclusion, LECs could be reprogrammed into iPSC-like cells and αA-crystallins could protect LEC-iPSC-like cells from oxidation stress-induced apoptosis.

Rad51 Regulates Reprogramming Efficiency through DNA Repair Pathway.

Rad51 is a key component of homologous recombination (HR) to repair DNA double-strand breaks and it forms Rad51 recombinase filaments of broken single-stranded DNA to promote HR. In addition to its role in DNA repair and cell cycle progression, Rad51 contributes to the reprogramming process during the generation of induced pluripotent stem cells. In light of this, we performed reprogramming experiments to examine the effect of co-expression of Rad51 and four reprogramming factors, Oct4, Sox2, Klf4, and c-Myc, on the reprogramming efficiency. Co-expression of Rad51 significantly increased the numbers of alkaline phosphatase-positive colonies and embryonic stem cell-like colonies during the process of reprogramming. Co-expression ofRad51 significantly increased the expression of epithelial markers at an early stage of reprogramming compared with control cells. Phosphorylated histone H2AX (γH2AX), which initiates the DNA double-strand break repair system, was highly accumulated in reprogramming intermediates upon co-expression of Rad51. This study identified a novel role of Rad51 in enhancing the reprogramming efficiency, possibly by facilitating mesenchymal-to-epithelial transition and by regulating a DNA damage repair pathway during the early phase of the reprogramming process.

Abstract 5011: generation of rejuvenated murine antigen-specific T cells by reprogramming to pluripotency and redifferentiation

Abstract Background: Adoptive cell therapy with autologous antigen-specific T cells is a promising approach for treating patients with chronic viral infections and various cancers. A major limitation of this approach is the difficulty of obtaining sufficient numbers of T cells with the characteristics necessary for in vivo effectiveness. Less-differentiated T cells with long telomeres would be an ideal T-cell subset for adoptive T cell therapy; however, generating large numbers of these “young” T cells is problematic. This limitation of adoptive T cell therapy can be overcome by using induced pluripotent stem cells (iPSCs) that self-renew, maintain pluripotency, and provide an unlimited source of autologous T cells for immunotherapy. However, in vivo antitumor reactivity of iPSC-rejuvenated T cells remains unknown due to the lack of animal model. Methods: To establish preclinical model of evaluating iPSC-rejuvenated antigen-specific T cells, we reprogrammed OT-1 T cell receptor (TCR) transgenic CD8 T cells using Sendai virus vectors encoding Oct3/4, Sox2, Klf4 and c-Myc transcription factors. Pluripotency and differentiation capacity of generated iPSCs were evaluated. Results: Twenty days after infection with Sendai virus vectors, we obtained murine embryonic stem cell-like colonies from OT-1 CD8 T cells. Immunofluorescence staining and RT-PCR analyses revealed pluripotency of established colonies. The iPSCs formed embryoid bodies in vitro, and upregulation of marker genes for all three germ layers was detected. The iPSCs differentiated into teratomas in vivo comprising all three embryonic germ layers in immune-deficient NOD/SCID mice. The iPSCs retained the same rearranged configuration of TCR chain genes as the original OT-1 T cells. Furthermore, OT-1 T cell-derived iPSCs differentiated into T cells on delta-like ligand 1 expressing OP9 (OP9/DL1) murine bone marrow stromal cells. Conclusions: Generation of rejuvenated T cells by reprogramming to pluripotency and redifferentiation is feasible. This type of approach may be useful for adoptive T cell therapy. We acknowledge DNAVEC Corporation for kindly providing Sendai virus vectors. This study was supported by the University of Michigan Start-up fund. Citation Format: Fumito Ito, Noemi Fusaki, Hidehito Saito. generation of rejuvenated murine antigen-specific T cells by reprogramming to pluripotency and redifferentiation. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5011. doi:10.1158/1538-7445.AM2015-5011

Neural stem cells differentiated from iPS cells spontaneously regain pluripotency.

Differentiated somatic cells can be reprogrammed into pluripotent stem cells by transduction of exogenous reprogramming factors. After induced pluripotent stem (iPS) cells are established, exogenous genes are silenced. In the pluripotent state, retroviral genes integrated in the host genome are kept inactive through epigenetic transcriptional regulation. In this study, we tried to determine whether exogenous genes remain silenced or are reactivated upon loss of pluripotency or on differentiation using an in vitro system. We induced differentiation of iPS cells into neural stem cells (NSCs) in vitro; the NSCs appeared morphologically indistinguishable from brain-derived NSCs and stained positive for the NSC markers Nestin and Sox2. These iPS cell-derived NSCs (iPS-NSCs) were also capable of differentiating into all three neural subtypes. Interestingly, iPS-NSCs spontaneously formed aggregates on long-term culture and showed reactivation of the Oct4-GFP marker, which was followed by the formation of embryonic stem cell-like colonies. The spontaneously reverted green fluorescent protein (GFP)-positive (iPS-NSC-GFP(+) ) cells expressed high levels of pluripotency markers (Oct4 and Nanog) and formed germline chimeras, indicating that iPS-NSC-GFP(+) cells had the same pluripotency as the original iPS cells. The reactivation of silenced exogenous genes was tightly correlated with the downregulation of DNA methyltransferases (Dnmts) during differentiation of iPS cells. This phenomenon was not observed in doxycycline-inducible iPS cells, where the reactivation of exogenous genes could be induced only by doxycycline treatment. These results indicate that pluripotency can be regained through reactivation of exogenous genes, which is associated with dynamic change of Dnmt levels during differentiation of iPS cells.

Dynamics associated with spontaneous differentiation of ovarian stem cells in vitro

BackgroundRecent studies suggest that ovarian germ line stem cells replenish oocyte-pool in adult stage, and challenge the central doctrine of ‘fixed germ cell pool’ in mammalian reproductive biology. Two distinct populations of spherical stem cells with high nucleo-cytoplasmic ratio have been recently identified in the adult mammalian ovary surface epithelium (OSE) including nuclear OCT-4A positive very small embryonic-like (VSELs) and cytoplasmic OCT-4 expressing ovarian germ stem cells (OGSCs). Three weeks culture of scraped OSE cells results in spontaneous differentiation of the stem cells into oocyte-like, parthenote-like, embryoid body-like structures and also embryonic stem cell-like colonies whereas epithelial cells attach and transform into a bed of mesenchymal cells. Present study was undertaken, to further characterize ovarian stem cells and to comprehend better the process of spontaneous differentiation of ovarian stem cells into oocyte-like structures in vitro.MethodsOvarian stem cells were enriched by immunomagnetic sorting using SSEA-4 as a cell surface marker and were further characterized. Stem cells and clusters of OGSCs (reminiscent of germ cell nests in fetal ovaries), were characterized by immuno-localization for stem and germ cell specific markers and spontaneous differentiation in OSE cultures was studied by live cell imaging.ResultsDifferential expression of markers specific for pluripotent VSELs (nuclear OCT-4A, SSEA-4, CD133), OGSCs (cytoplasmic OCT-4) primordial germ cells (FRAGILIS, STELLA, VASA) and germ cells (DAZL, GDF-9, SCP-3) were studied. Within one week of culture, stem cells became bigger in size, developed abundant cytoplasm, differentiated into germ cells, revealed presence of Balbiani body-like structure (mitochondrial cloud) and exhibited characteristic cytoplasmic streaming.ConclusionsPresence of germ cell nests, Balbiani body-like structures and cytoplasmic streaming extensively described during fetal ovary development, are indeed well recapitulated during in vitro oogenesis in adult OSE cultures along with characteristic expression of stem/germ cell/oocyte markers. Further studies are required to assess the genetic integrity of in vitro derived oocytes before harnessing their clinical potential. Advance in our knowledge about germ cell differentiation from stem cells will enable researchers to design better in vitro strategies which in turn may have relevance to reproductive biology and regenerative medicine.

Reprogramming of Mouse Cochlear Cells by Transcription Factors to Generate Induced Pluripotent Stem Cells

As an initial step for using technology derived from induced pluripotent stem cells (iPSCs) in the field of inner ear therapeutics, we examined the potential of four transcription factors, Oct3/4, Sox2, Klf4, and c-Myc, which are employed in the generation of iPSCs, for dedifferentiating cochlear epithelial cells. Otospheres, which are sphere-forming cells derived from dissociated cochlear epithelial cells of neonatal mice, were used as a cell source. The four transcription factors were introduced into otospheres using retroviral vectors. Virally transduced otospheres formed embryonic stem cell-like colonies that expressed markers for pluripotent stem cells and were capable of differentiating into the three germ layers in vivo and in vitro. These findings illustrate that viral transduction of four transcription factors can lead to reprogramming of cochlear epithelial cells, which may contribute to future studies of dedifferentiation of cochlear epithelial cells in tissue and identification of key molecules for otic induction.

Abstract 17216: Aquaporin-1 is Required for Vascular Differentiation of Human Induced Pluripotent Stem Cells Following Exposure to Glucose-Induced Hyperosmolarity

Background and objective: Diabetic hyperglycemia increases plasma osmolarity, leading to adaptive cell reponses. Aquaporin-1 (AQP1) is induced by hyperosmolarity and plays a role in the vascular permeability. Induced pluripotent stem (iPS) cells offer a disease-relevant cellular model for the interplay of risk factors in the vascular complications of diabetes. We tested the hypothesis that glucose-induced hyperosmolarity promotes angiogenesis in human iPS cells through activation of AQP1 and downstream osmosignaling pathway, thus orchestrating cell sprouting and migration. Methods and results: Human iPS cells were generated from skin fibroblasts by lentiviral transduction of four reprogramming factors (Oct4, SOX2, Klf4 and c-Myc). Following 3 weeks compact refractive embryonic stem cell-like colonies emerged. All the iPS cell colonies expressed OCT4, SSEA3, SSEA4 and SOX2, characteristic of successful dedifferentiation. After reprogramming, iPS cells were transfected with siRNA-AQP1 or scrambled controls, and exposed to 5.5 mmol/L glucose (normoglycemia), high glucose (HG) at 12.5, 25 and 45 mmol/L or with high mannitol (HM) at 12.5, 25 and 45 mmol/L for 24-72 hours. Exposure to either HG or HM increased expression of AQP1 and tonicity enhancer binding protein (TonEBP) while decreasing the iPS cell numbers. In iPS cells, AQP1 could be co-immunoprecipitated with β-catenin. HG and HM strongly induced the expression of β-catenin (n=3, p<0.001 vs normal glucose by ANOVA). Under these conditions, proteins co-immunoprecipitated with anti-AQP1 and β-catenin showed increased ratio of F-actin vs G-actin (n=3, p<0.01 vs normal glucose by ANOVA). iPS cells formed bundles in methylcellulose matrix and tubing networks in matrigel, especially when they were exposed to HG and HM (HG 2.8±0.2 fold; HM 3.3±0.5 fold; n=3, p<0.01 by ANOVA. SiRNA to AQP1 reverted the inducing effects of HG and HM on β-catenin expression, actin polymerization and angiogenic activities. Conclusions: The hyperosmolarity serves as a biophysical factor that promotes angiogenesis in human iPS cells. This effect may occur through an AQP1-associated cytoskeleton remodeling. Targeting the osmosignaling pathway offers a novel strategy to reduce vascular complications of diabetes.

Detection, characterization, and spontaneous differentiation in vitro of very small embryonic-like putative stem cells in adult mammalian ovary.

The present study was undertaken to detect, characterize, and study differentiation potential of stem cells in adult rabbit, sheep, monkey, and menopausal human ovarian surface epithelium (OSE). Two distinct populations of putative stem cells (PSCs) of variable size were detected in scraped OSE, one being smaller and other similar in size to the surrounding red blood cells in the scraped OSE. The smaller 1-3 μm very small embryonic-like PSCs were pluripotent in nature with nuclear Oct-4 and cell surface SSEA-4, whereas the bigger 4-7 μm cells with cytoplasmic localization of Oct-4 and minimal expression of SSEA-4 were possibly the tissue committed progenitor stem cells. Pluripotent gene transcripts of Oct-4, Oct-4A, Nanog, Sox-2, TERT, and Stat-3 in human and sheep OSE were detected by reverse transcriptase-polymerase chain reaction. The PSCs underwent spontaneous differentiation into oocyte-like structures, parthenote-like structures, embryoid body-like structures, cells with neuronal-like phenotype, and embryonic stem cell-like colonies, whereas the epithelial cells transformed into mesenchymal phenotype by epithelial-mesenchymal transition in 3 weeks of OSE culture. Germ cell markers like c-Kit, DAZL, GDF-9, VASA, and ZP4 were immuno-localized in oocyte-like structures. In conclusion, as opposed to the existing view of OSE being a bipotent source of oocytes and granulosa cells, mammalian ovaries harbor distinct very small embryonic-like PSCs and tissue committed progenitor stem cells population that have the potential to develop into oocyte-like structures in vitro, whereas mesenchymal fibroblasts appear to form supporting granulosa-like somatic cells. Research at the single-cell level, including complete gene expression profiling, is required to further confirm whether postnatal oogenesis is a conserved phenomenon in adult mammals.

The timing of retroviral silencing correlates with the quality of induced pluripotent stem cell lines

Background Induced pluripotent stem (iPS) cells can be generated from somatic cells by introducing the four transcription factors Oct4, Sox2, Klf4, and c-Myc. Given that iPS cell technology may be useful for medical applications, the quality of iPS cells needs to be maintained during prolonged cultivation. However, it is unclear whether there are any differences in stability among different iPS clones. Methods We infected mouse embryonic and adult fibroblasts with retroviruses encoding Oct4, Sox2, Klf4, c-Myc, and green fluorescent protein ( GFP). We obtained embryonic stem (ES) cell-like colonies with silenced retroviral transgenes and divided these colonies into two groups: ES cell-like colonies that underwent retroviral silencing (i) on around day 14 (called early iPS) or (ii) on around day 30 (called late iPS), after infection. We compared morphology, proliferation efficiency, pluripotency marker expression, and karyotype between early iPS and late iPS cells. Results Early iPS cells were more stable than late iPS cells. At passage 20, most of the early iPS clones maintained ES cell-like morphology, expressed pluripotency markers, and showed proliferation efficiency similar to ES cells. Furthermore, early iPS clones derived from both embryonic and adult fibroblasts gave rise to chimeras and could show germ line competency. In contrast, late iPS clones tended to lose their ES cell-like morphology and normal karyotype in prolonged culture. General Significance Our results provide useful information on the efficient derivation of stable iPS cells that may be useful for germline transmission in mouse. This study suggests that early completion of full reprogramming allows for superior iPS cell generation.

Effective generation of iPS cells from CD34 + cord blood cells by inhibition of p53

Cord blood banks provide fully human leukocyte antigen-typed cells, from which a set of standard induced pluripotent stem (iPS) cells for use in allogenic transplantation can be derived. Hence, the ability to generate iPS cells from cord blood cells has the potential to provide a suitable source for clinical transplantation. The aim of this work is to determine the reprogramming methods, culture conditions, and cell fractions that can be used to generate iPS cells from cord blood cells effectively. CD34(+), mononucleated, and derived adherent cells from cord blood were cultured in hematopoietic medium (X-vivo10 containing 50 ng/mL interleukin-6, 50 ng/mL soluble interleukin-6 receptor, 50 ng/mL stem cell factor, 10 ng/mL thrombopoietin, and 20 ng/mL Flit3/4 ligand) 3 days prior to viral infection. Cells were then infected with retroviral constructs driving the expression of OCT3/4, SOX2, Krüppel-like factor 4, c-MYC, and enhanced green fluorescent protein together with or without the p53 knockdown lentiviral construct Shp53 pLKO.1-puro. Infected cells were then cultured for an additional 4 days in hematopoietic culture medium before being transferred onto mouse embryonic fibroblast (MEF) or SNL76/7 feeder cells in human embryonic stem cell medium (Dulbecco's modified Eagle medium/F-12 containing 20% knockout serum replacement, 200 mM L-glutamine, 1% non-essential amino acids (NEAA), 0.1 mM 2-mercaptoethanol, and 4 ng/mL basic fibroblast growth factor). Subsequently, the number of embryonic stem cell-like colonies that emerged in the following 4 weeks was scored. Expression of a number of pluripotency makers were examined by immunochemistry and reverse transcriptase polymerase chain reaction. Finally, the differentiation potential of selected colonies was determined by teratoma formation in severe combined immunodeficient mice and in vitro culture. Repression of p53 expression by the addition of a lentiviral p53 short-hairpin RNA expression vector increased the frequency of formation of iPS-like colonies from 1 (on average) to around 100 per 2 x 10(4) cells when infected cells were grown on SNL feeder cells. iPS cells can be generated easily from CD34(+) cord blood cells through the addition of p53 inhibition to standard reprogramming conditions.

Derivation of developmentally competent oocytes by the culture of preantral follicles retrieved from adult ovaries: maturation, blastocyst formation, and embryonic stem cell transformation

To determine whether the preantral follicles in adult ovaries can generate developmentally competent oocytes after in vitro culture. Prospective, animal-model study. Gamete and Stem Cell Biotechnology Laboratory, Seoul National University, Seoul, Korea. B6CBAF1 mice. Preantral follicles collected from 8-week-old mice were cultured in vitro. Follicle development, embryogenesis, and embryonic stem cell characterization. A mean of 50.3 preantral follicles were retrieved from one adult animal, which is significantly less than the number (88.7 follicles) retrieved from a prepubertal female. Extension of the culture period greatly improved oocyte maturation; increased follicular growth to the pseudo-antral (89%-91% vs. 32%) or mature oocyte stage (65%-77% vs. 13%) was observed after 12 or 13 days of culture compared with 9 days of culture. Blastocyst formation after parthenogenesis was detected in only one case; in comparison, the use of IVF yielded a large number of embryos that developed into blastocysts. A mean of 14.7 intrafollicular oocytes per animal were produced after 13 days of culture, and 41% of those developed into blastocysts after IVF. Embryonic stem cell-like colonies were established by subculturing the inner cell mass cells from the blastocysts. Developmentally competent oocytes can be generated by culturing adult preantral follicles. These results may help increase the feasibility of follicle culture systems.

A Transcriptional Logic for Nuclear Reprogramming

Limitations on a differentiated cell's pluripotency can be erased by nuclear transfer or by fusion with embryonic stem cells, but attempts to recapitulate this process of nuclear reprogramming by molecular means have failed. In this issue of Cell, Takahashi and Yamanaka (2006) take a rational approach to identifying a suite of embryonic transcription factors whose overexpression restores pluripotency to adult somatic cells.

Osteogenic Differentiation of Mouse Embryonic Stem Cells and Mouse Embryonic Fibroblasts in a Three-Dimensional Self-Assembling Peptide Scaffold

In the present work, we studied the differentiation capacity of mouse embryonic stem cells (mESCs) and mouse embryonic fibroblasts (MEFs) to differentiate into osteoblast-like cells in a 3-dimensional (3D) self-assembling peptide scaffold, a synthetic nanofiber biomaterial with potential applications in regenerative medicine. We demonstrated that 2D and 3D systems promoted differentiation of mESCs into cells with an osteoblast-like phenotype consisting of osteopontin and collagen I marker expression, as well as high alkaline phosphatase (ALP) activity and calcium phosphate deposits. In 3D cultures the frequency of appearance of embryonic stem cell-like colonies was substantially greater, suggesting that the 3D microenvironment promoted the generation of a stem cell-like niche that allows undifferentiated stem cell maintenance. On the other hand, after MEFs were cultured in the 3D system with their regular growth medium, but not in the 2D system, they expressed osteopontin, up-regulated metalloproteinase activities, and acquired a distinct phenotype consisting of small, elongated cells with remaining mitotic activity. Furthermore, only 3D MEF cultures underwent osteoblast differentiation after osteogenic induction, based on matrix mineralization, collagen I synthesis, ALP activity, and expression of the osteoblast transcription factor Runx2, suggesting that the 3D environment promotes differentiation of MEFs into osteoblast-like cells. We propose that the 3D system provides a unique microenvironment that promotes differentiation of mESCs and MEFs into osteoblast-like cells.

194 ESTABLISHMENT OF GOAT EMBRYONIC STEM CELL-LIKE LINES DERIVED FROM IN VIVO-PRODUCED BLASTOCYST-STAGE EMBRYOS

Pluripotent embryonic stem cells (ESC) derived from the inner cell mass (ICM) of mammalian blastocysts provide AN unlimited number of cells that can be used in gene targeting and be of great value to agriculture and medicine. Embryonic stem cells with capacity for germ line transmission have been verified only in mouse despite many efforts to derive ESC from other mammalian species. The methods for the derivation, propagation and differentiation of ESC from domestic animals have not been fully established. The objective of this study was the generation and initial characterization of goat embryonic stem cells (GESC) derived from in vivo-produced blastocyst-stage embryos. Goat compact morulae and blastocysts were collected from superovulated adult Saanen crossbreed donors 7 days after insemination with a fertile male. Embryos were collected by uterine flushing using a 12Fr. Foley catheter by means of a laparoscopically assisted mid-ventral laparotomy under general anesthesia. Twenty eight in vivo-derived blastosyst-stage embryos were cultured on a goat fetal fibroblast feeder layer (inactivated by Mitomycin C) in a medium of DMEM containing 0.1 mm �-mercaptoethanol, 0.1 mm MEM nonessential amino acids, 200 mm l-glutamine, and 10% FCS. Following three days in culture 25 of 28 embryos hatched. Ten embryos attached to the feeder layer, nine degenerated, and nine embryos were floating in the medium and expanding in size. After 5-7 days in culture four of the tehn attached embryos appeared with a prominent an ICM outgrowth and 3 of the nine floating embryos formed structures resembling ICM disc surrounded by trophectoderm cells. The ICM and the embryonic discs were isolated mechanically and cultured on goat feeder cells in DMEM medium containing 10 ng/mL horse leukemia inhibitory factor (hLIF) and 10% FCS. The ICM and embryonic disc outgrew into colonies on Day 4 post-culture. Compact colonies of cells from these outgrowths were isolated mechanically and passed onto fresh goat feeder cells every 4-5 days with the addition of 10 ng/mL hLIF to the culture media. Established colonies at passage 6 were tested for immunoreactivity against alkaline phosphatase (AP) and Oct-1 using standard protocols. The result was the estabilshment of embryonic stem cell-like colonies (57%) from both ICM and embryonic discs cultured on goat fetal fibroblast feeder cells. Colonies forming from these outgrowths (50%) of either ICM or embryonic disc stained positive for both AP and Oct-4. Embryoid bodies formed from colonies of either ICM or embryonic disc in suspension (DMEM containing 10% FCS with no hLIF). Two cell lines (one from ICM and one from embryonic disc) have been maintained so far through passage 8 and have been cryopreserved. These GESC-like lines will be used in further characterization and ultimately in transgenic animal production studies.

Survival of porcine inner cell masses in culture and after injection into blastocysts

Isolation of embryonic stem cells has been documented only in the mouse and perhaps the hamster and cow. We report results of experiments designed to determine the effect of age of porcine embryos (6 through 10 d after the first day of estrus) on isolation of cell lines with embryonic stem cell-like morphology. The capacity of fresh and short-term cultured inner cell mass (ICM) cells to differentiate into normal tissues after injection into blastocysts was also measured. Few Day-6 ICM survived in culture to the first passage onto fresh feeder cells, but cell lines with embryonic stem cell-like morphology developed from Day-7 through Day-10 ICM. Isolation of embryonic stem cell-like colonies was achieved at a higher frequency from ICM isolated from older embryos, but embryonic stem cell-like colonies from older embryos also tended to differentiate spontaneously in culture. Viable porcine chimeras were born after injection of fresh ICM into blastocysts that were transferred to recipients for development to term; no chimeras were born from blastocysts injected with ICM subjected to short-term (1 to 6 d) culture. Germ-cell chimerism was confirmed in one of the chimeras. These results document that undifferentiated cells can be removed from porcine blastocysts, transplanted to other embryos, and contribute to development of normal differentiated tissues, including germ cells. Cells with embryonic stem-like morphology can be isolated in culture from ICM at various embryonic ages, but ICM from young blastocysts (e.g., Day-7 embryos) yield embryonic stem cell-like colonies at lower frequency than do ICM from older blastocysts (e.g., Day-10 embryos).