Derivation of human embryonic stem cell lines, towards clinical quality

2006 ◽  
Vol 18 (8) ◽  
pp. 823 ◽  
Author(s):  
Outi Hovatta
Keyword(s):  
Cell Lines ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Calf Serum ◽  
Embryonic Stem ◽  
Quality Criteria ◽  
Good Manufacturing Practice ◽  
Clinical Quality ◽  
Serum Replacement ◽  
Hes Cells

Human embryonic stem (hES) cells offer an excellent source of cells for transplantation in the treatment of severe diseases. To be clinically safe, the lines have to be derived using strict quality criteria and good manufacturing practice. Animal proteins are immunogenic and may contain microbes, and they should not be used in establishing or propagating hES cells. Derivation systems have been improved towards clinical quality by establishing all 25 hES cell lines using human skin fibroblasts as feeder cells instead of mouse fibroblasts. A further 21 cell lines have been established using synthetic serum instead of fetal calf serum in the medium. In the five latest derivations, the inner cell mass was isolated mechanically instead of by immunosurgery (animal antibodies). Feeder-free derivation would be optimal, but it is not yet considered safe. Clinical-quality lines can be derived by establishing the skin fibroblast feeders in the good manufacturing practice laboratory with human serum in the medium, and by establishing the hES cells on such feeders. In this process, a serum replacement that contains only human protein can be used, the inner cell mass has to be isolated mechanically, and the colonies have to be split mechanically for passaging. Somatic cell nuclear transfer would help to overcome rejection of transplanted cells.

293 EMBRYONIC STEM-LIKE CELLS DERIVED FROM PORCINE INNER CELL MASS CELLS ISOLATED BY DIFFERENT METHODS

2008 ◽  
Vol 20 (1) ◽  
pp. 226
Author(s):  
X. A. Wolf ◽  
M. A. Rasmussen ◽  
K. Schauser ◽  
P. Maddox-Hyttel
Keyword(s):  
Inner Cell Mass ◽  
Cell Mass ◽  
Calf Serum ◽  
Embryonic Stem ◽  
Culture Conditions ◽  
Embryonic Fibroblasts ◽  
Serum Replacement ◽  
Sox2 Expression ◽  
Differentiated Cells

The aim was to examine isolation methods and culture conditions for the establishment of embryonic stem-like cells derived from the inner cell mass (ICM) of porcine embryos. A total of 83 zona pellucida-enclosed (ZPE) and 88 hatched (ZPH) porcine in vivo Days 5–7 blastocysts were assigned for ICM isolation by: (A) manual dissection by needles (ZPE: n = 10; ZPH, n = 15), (B) immunosurgical isolation (ZPE: n = 30; ZPH: n = 10), (C) immunosurgery and manual cleaning (ZPE: n = 11; ZPH: n = 40), and (D) culture of whole blastocysts (ZPE: n = 42; ZPH: n = 23). Culture was done on mouse embryonic fibroblasts (MEF) at 5% O2 (for A–C) and 20% O2 (for D) in DMEM with fetal calf serum (FCS), serum replacement, and leukemia inhibitory factor (LIF). Outgrowth colonies (OC) were evaluated by phase contrast and subjected to either (1) physical passage and RT-PCR for Oct-4, Nanog, and Sox2; or (2) immunocytochemical localization of Oct-4 at Days 6–7. Five OC categories were defined: (I) epiblast-like colonies (multilayered ICM-like with homogeneous nuclear Oct-4 staining), (II) ES-like colonies with few surrounding cells (ES-like cells with homogeneous nuclear Oct-4 staining surrounded by few cells), (III) clearly delineated ES-like colonies (ES-like cells with homogeneous or heterogeneous nuclear Oct-4 staining and clear demarcation to many differentiated cells), (IV) poorly delineated ES-like colonies (ES-like cells with homogeneous or heterogeneous nuclear Oct-4-staining and poor demarcation to many differentiated cells), and (V) differentiated colonies (heterogeneous cell populations lacking nuclear Oct-4 staining). Oct-4 staining was supported by expression of Oct-4, often associated with Nanog and Sox2. The attachment rates were similar for methods A, B, and C, being higher for ZPH (75–80%) than for ZPE (40–50%) blastocysts. Method D gave 42% attachment for ZPE, but only 23% for ZPH blastocysts at 5% O2, whereas the figures at 20% O2 were 63% and 80%, respectively. Methods B and C gave the highest proportion of OCs in categories II–IV (ES-like cell-containing), and the ZPE-derived OCs exhibited a more homogeneous nuclear Oct-4 staining than the ZPH-derived. Method D gave the highest proportion of category II colonies. Passage was performed from OC categories II–IV (with ES-like cells). For method C, 24 OCs resulted in 18 (75%) passage 1 (P1) colonies. In 11, 6, 3, and 2 cases, they were passed to P2, P3, P4, and P5, respectively, maintaining ES-like morphology before they went into quiescence or differentiation. However, most colonies attained cytoplasmic Oct-4 staining and lost Oct-4, Nanog, and Sox2 expression at P1 or P2; only a single colony maintained Nanog and Sox2 expression up to P3. For isolation method D, 10 OCs resulted in 3 (30%) P1 colonies, but only one continued to P2 before differentiation. In conclusion, all methods consistently gave ES-like OCs. Whole blastocysts at 20% O2 gave the highest attachment rates. However, immunosurgery, eventually followed by manual cleaning, tended to result in the highest proportion of OCs presenting ES-like cells, with the ZPE-derived OCs exhibiting the most homogeneous Oct-4 staining. When subjected to passage, a few colonies maintained ES-like morphology up to P5, but expression of pluripotency markers was lost during the initial passages.

Derivation of human embryonic stem cell lines after blastocyst microsurgery

2010 ◽  
Vol 88 (3) ◽  
pp. 479-490 ◽  
Author(s):  
Guoliang Meng ◽  
Shiying Liu ◽  
Xiangyun Li ◽  
Roman Krawetz ◽  
Derrick E. Rancourt
Keyword(s):  
Stem Cells ◽  
Embryonic Stem Cells ◽  
Cell Lines ◽  
Clinical Medicine ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Embryonic Stem ◽  
Hesc Lines

Embryonic stem cells (ESCs) are derived from the inner cell mass (ICM) of the blastocyst. Because of their ability to differentiate into a variety of cell types, human embryonic stem cells (hESCs) provide an unlimited source of cells for clinical medicine and have begun to be used in clinical trials. Presently, although several hundred hESC lines are available in the word, only few have been widely used in basic and applied research. More and more hESC lines with differing genetic backgrounds are required for establishing a bank of hESCs. Here, we report the first Canadian hESC lines to be generated from cryopreserved embryos and we discuss how we navigated through the Canadian regulatory process. The cryopreserved human zygotes used in this study were cultured to the blastocyst stage, and used to isolate ICM via microsurgery. Unlike previous microsurgery methods, which use specialized glass or steel needles, our method conveniently uses syringe needles for the isolation of ICM and subsequent hESC lines. ICM were cultured on MEF feeders in medium containing FBS or serum replacer (SR). Resulting outgrowths were isolated, cut into several cell clumps, and transferred onto fresh feeders. After more than 30 passages, the two hESC lines established using this method exhibited normal morphology, karyotype, and growth rate. Moreover, they stained positively for a variety of pluripotency markers and could be differentiated both in vitro and in vivo. Both cell lines could be maintained under a variety of culture conditions, including xeno-free conditions we have previously described. We suggest that this microsurgical approach may be conducive to deriving xeno-free hESC lines when outgrown on xeno-free human foreskin fibroblast feeders.

216 EMBRYONIC AND INDUCED PLURIPOTENT STEM CELLS ANALOGOUS TO INNER CELL MASS-DERIVED LIF-DEPENDENT MOUSE EMBRYONIC STEM CELLS ESTABLISHED FROM THE DOMESTIC PIG, SUS SCROFA

2012 ◽  
Vol 24 (1) ◽  
pp. 220
Author(s):  
B. P. Telugu ◽  
T. Ezashi ◽  
A. Alexenko ◽  
S. Lee ◽  
R. S. Prather ◽  
...  
Keyword(s):  
Stem Cells ◽  
Embryonic Stem Cells ◽  
Induced Pluripotent Stem Cells ◽  
Cell Lines ◽  
Umbilical Cord ◽  
Pluripotent Stem Cells ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Embryonic Stem ◽  
Induced Pluripotent

Authentic embryonic stem cells (ESC) may never have been successfully derived from the inner cell mass (ICM) of pig and other ungulates, despite over 25 years of effort. Recently, porcine induced pluripotent stem cells (piPSC) were generated by reprogramming somatic cells with a combination of four factors OCT4, SOX2, KLF4 and c-MYC (OSKM) delivered by lentiviral transduction. The established piPSC are analogous to FGF2-dependent human (h) ESC and murine “epiblast stem cells,” and are likely to advance swine as a model in biomedical research. Here, we report for the first time, the establishment of LIF-dependent, so called naïve type pluripotent stem cells (1) from the inner cell mass (ICM) of porcine blastocysts by up-regulating the expression of KLF4 and POU5F1; and (2) from umbilical cord mesenchyme (Wharton's jelly) by transduction with OSKM factors and subsequent culture in the presence of LIF-based medium with inhibitors that substitute for low endogenous expression of c-MYC and KLF4 and promote pluripotency. The 2 compounds that have been used in this study are, CHIR99021 (CH), which substitutes c-MYC by inhibiting GSK3B and activating WNT signalling and Kenpaullone (KP), which inhibits both GSK3B and CDK1 and supplants KLF4 function. The lentiviral vectors employed for introducing the re-programming genes were modified for doxycycline-mediated induction of expression (tet-on) and are ‘floxed’ for Cre-mediated recombination and removal of transgenes following complete reprogramming. Two LIF-dependent cell lines have been derived from the ICM cells of late d 5.5 in vitro produced blastocysts and four from umbilical cord mesenchyme recovered from fetuses at d 35 of pregnancy. The derived stem cell lines are alkaline phosphatase-positive, resemble mouse embryonic stem cells in colony morphology, cell cycle interval, transcriptome profile and expression of pluripotent markers, such as POU5F1, SOX2 and surface marker SSEA1. They are dependent on LIF signalling for maintenance of pluripotency, can be cultured over extended passage (>50) with no senescence. Of importance, the ICM-derived lines have been successful in their ability to form teratomas. The cells could be cultured in feeder free conditions on a synthetic matrix in the presence of chemically defined medium and can be coaxed to differentiate under xeno-free conditions. Currently, the piPSC lines are being investigated for their ability to give rise to teratomas and to produce a live offspring by nuclear transfer. Supported by Addgene Innovation Award, MO Life Sciences Board Grant 00022147 and NIH grant HD21896.

287 ACTIVE MITOCHONDRIA ARE PRESENT IN MOUSE AND MONKEY EMBRYONIC STEM CELL LINES

2008 ◽  
Vol 20 (1) ◽  
pp. 223 ◽  
Author(s):  
T. Lonergan ◽  
A. Harvey ◽  
J. Zhao ◽  
B. Bavister ◽  
C. Brenner
Keyword(s):  
Cell Lines ◽  
Complex I ◽  
Inner Cell Mass ◽  
Es Cells ◽  
Cell Mass ◽  
Embryonic Stem ◽  
Mouse Fibroblast ◽  
Es Cell ◽  
Cell Content ◽  
Stem Cell Lines

The inner cell mass (ICM) of the blastocyst develops into the fetus after uterine implantation. Prior to implantation, ICM cells synthesize ATP by glycolytic reactions. We now report that cells of the ICM in 3.5-day-old mouse embryos have too few mitochondria to be visualized with either Mitotracker red (active mitochondria) or an antibody against complex I of OXPHOS. By comparison, all of the surrounding trophectoderm cells reveal numerous mitochondria throughout their cytoplasm. It has largely been assumed that embryonic stem (ES) stem cells derived from the ICM also have few mitochondria, and that replication of mitochondria in the ES cells does not begin until they commence differentiation. We further report that mouse E14 ES cells and monkey ORMES 7 ES cells have considerable numbers of active mitochondria when cultured under standard conditions, i.e., 5% CO2 in air. Both the mouse E14 and monkey ES cell lines expressed two markers of undifferentiated cells, Oct-4 and SSEA-4, and monkey ES cells expressed the undifferentiated cell marker Nanog; however, Oct-4 is nonspecific in monkey ES cells because trophectoderm also expresses this marker, unlike in mice. Ninety-nine percent of the E14 cells examined, and 100% of the ORMES 7 cells, have a visible mitochondrial mass when stained with either Mitoracker red or with an antibody against OXPHOS complex I. The ATP content in the mouse E14 cells (4.13 pmoles ATP/cell) is not significantly different (P = 0.76) from that in a mouse fibroblast control (3.75 pmoles ATP/cell). Cells of the monkey ORMES 7 cell line had 61% of the ATP/cell content (7.55 pmoles ATP/cell) compared to the monkey fibroblast control (12.38 pmoles ATP/cell). Both cell lines expressed two proteins believed to indicate competence of mitochondria to replicate: PolG, the polymerase used to replicate the mitochondrial genome, and TFAM, a nuclear-encoded transcription factor reported to regulate several aspects of mitochondrial function. Both proteins were found to co-localize in the mitochondria. We conclude that when the ICMs are isolated from blastocysts and used to establish these two ES cell lines in cell culture, mitochondrial biosynthesis is activated.

54 Effect of Different Cryopreservation Protocols for Sheep Embryonic Stem Cells

2018 ◽  
Vol 30 (1) ◽  
pp. 166
Author(s):  
N. Ibraimova ◽  
A. Seisenbayeva ◽  
Y. Toishibekov
Keyword(s):  
Stem Cells ◽  
Embryonic Stem Cells ◽  
Ethylene Glycol ◽  
Dimethyl Sulfoxide ◽  
Fetal Calf Serum ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Calf Serum ◽  
Embryonic Stem ◽  
Slow Freezing

Particular attention is required to improve cryopreservation of embryonic stem cells (ESC) and study their characteristics. Stem cells were obtained from the inner cell mass of Day 5-6 blastocysts. The ESC were then cultured on mTeSR™1 medium (Stemcell Technologies, Cambridge, MA, USA). We studied the survival of ESC after slow freezing and vitrification. Slow freezing was carried out using a Planer Kryo 360-3.3 freezer (Planer plc, Sunbury-on-Thames, United Kingdom), using various cryoprotectants: 1.5 M dimethyl sulfoxide (Me2SO), 1.5 M ethylene glycol (EG), or 1.5 M propylene glycol (PG). Six vitrification solutions (VS) were used to vitrify ESC: VS1 = 20% Me2SO + 20% EG + 0.5 M sucrose; VS2 = 20% Me2SO + 20% PROH + 0.5 M sucrose; VS3 = 20% EG + 20% PG + 0.5 M sucrose; VS4 = 20% Me2SO + 20% EG + 0.5 M sucrose + 10% FCS; VS5 = 20% Me2SO + 20% PROH + 0.5 M sucrose + 10% FCS; and VS6 = 20% EG + 20% PG + 0.5 M sucrose + 10% FCS. For the dehydration of cells and the addition of vitrification solutions, a 3-step equilibration was used. The proliferative properties of the cells were determined using an Apel PD-303S spectrophotometer (Apel Co. Ltd., Kawaguchi, Japan), using an MTT test (staining with methylthiazolyl-diphenyl tetrazolium). After slow freezing, the highest percentage of frozen–thawed cells proliferating was observed when using 1.5 M EG (P > 0.05). At the same time, the highest cell doubling after thawing was observed when using 1.5 M EG, and 1.5 M Me2SO. After vitrification, the highest percentage of proliferation was observed in the VS2 and VS4 groups (49.7 ± 3.2% and 53.2 ± 3.8%, respectively). It should be noted that the addition of fetal calf serum to the vitrification solution also increased the proliferation of ESC after vitrification and thawing.

Establishment of rat embryonic stem-like cells from the morula using a combination of feeder layers

Zygote ◽  
2009 ◽  
Vol 17 (3) ◽  
pp. 229-237 ◽  
Author(s):  
Chiaki Sano ◽  
Asako Matsumoto ◽  
Eimei Sato ◽  
Emiko Fukui ◽  
Midori Yoshizawa ◽  
...  
Keyword(s):  
Cell Lines ◽  
Inner Cell Mass ◽  
Es Cells ◽  
Cell Mass ◽  
Embryonic Stem ◽  
Preimplantation Embryos ◽  
Long Term Culture ◽  
Oct4 Expression ◽  
Feeder Layers

SummaryEmbryonic stem (ES) cells are characterized by pluripotency, in particular the ability to form a germline on injection into blastocysts. Despite numerous attempts, ES cell lines derived from rat embryos have not yet been established. The reason for this is unclear, although certain intrinsic biological differences among species and/or strains have been reported. Herein, using Wistar-Imamichi rats, specific characteristics of preimplantation embryos are described. At the blastocyst stage, Oct4 (also called Pou5f1) was expressed in both the inner cell mass (ICM) and the trophectoderm (TE), whereas expression of Cdx2 was localized to the TE. In contrast, at an earlier stage, expression of Oct4 was detected in all the nuclei in the morula. These stages were examined using a combination of feeder layers (rat embryonic fibroblast [REF] for primary outgrowth and SIM mouse embryo-derived thioguanine- and ouabain-resistant [STO] cells for passaging) to establish rat ES-like cell lines. The rat ES-like cell lines obtained from the morula maintained expression of Oct4 over long-term culture, whereas cell lines derived from blastocysts lost pluripotency during early passage. The morula-derived ES-like cell lines showed Oct4 expression in a long-term culture, even after cryogenic preservation, thawing and EGFP transfection. These results indicate that rat ES-like cell lines with long-term Oct4 expression can be established from the morula of Wistar-Imamichi rats using a combination of feeder layers.

scholarly journals Mechanical isolation of the inner cell mass is effective in derivation of new human embryonic stem cell lines

2007 ◽  
Vol 22 (12) ◽  
pp. 3051-3058 ◽  
Author(s):  
S. Strom ◽  
J. Inzunza ◽  
K.-H. Grinnemo ◽  
K. Holmberg ◽  
E. Matilainen ◽  
...  
Keyword(s):  
Stem Cell ◽  
Embryonic Stem Cell ◽  
Cell Lines ◽  
Human Embryonic Stem Cell ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Embryonic Stem ◽  
Stem Cell Lines ◽  
Mechanical Isolation

scholarly journals Clonal culturing of human embryonic stem cells on laminin-521/E-cadherin matrix in defined and xeno-free environment

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Sergey Rodin ◽  
Liselotte Antonsson ◽  
Colin Niaudet ◽  
Oscar E. Simonson ◽  
Elina Salmela ◽  
...  
Keyword(s):  
Inner Cell Mass ◽  
Cell Mass ◽  
Embryonic Stem ◽  
Cell Types ◽  
A Cell ◽  
Hes Cells ◽  
Free Environment ◽  
Different Cell Types ◽  
E Cadherin

Abstract Lack of robust methods for establishment and expansion of pluripotent human embryonic stem (hES) cells still hampers development of cell therapy. Laminins (LN) are a family of highly cell-type specific basement membrane proteins important for cell adhesion, differentiation, migration and phenotype stability. Here we produce and isolate a human recombinant LN-521 isoform and develop a cell culture matrix containing LN-521 and E-cadherin, which both localize to stem cell niches in vivo. This matrix allows clonal derivation, clonal survival and long-term self-renewal of hES cells under completely chemically defined and xeno-free conditions without ROCK inhibitors. Neither LN-521 nor E-cadherin alone enable clonal survival of hES cells. The LN-521/E-cadherin matrix allows hES cell line derivation from blastocyst inner cell mass and single blastomere cells without a need to destroy the embryo. This method can facilitate the generation of hES cell lines for development of different cell types for regenerative medicine purposes.

228 ESTABLISHMENT OF EMBRYONIC STEM-LIKE CELL LINES IN RABBITS

2007 ◽  
Vol 19 (1) ◽  
pp. 230 ◽  
Author(s):  
Y.-W. Ou ◽  
K.-H. Lee ◽  
L.-R. Chen ◽  
P.-C. Tang ◽  
H.-F. Guu ◽  
...  
Keyword(s):  
Cell Lines ◽  
Inner Cell Mass ◽  
Es Cells ◽  
Cell Mass ◽  
Embryonic Stem ◽  
Embryoid Bodies ◽  
Immunocytochemical Staining ◽  
Es Cell ◽  
Feeder Layers ◽  
Feeder Group

Embryonic stem (ES) cells are pluripotent cells from the inner cell mass (ICM) of the blastocyst. They are capable of differentiating to various cell types, such as neural cells, cardiocytes, hepatic cells, and germ cells. The aim of this study was to establish rabbit ES cell lines as an animal model for human diseases. Blastocysts were collected from New Zealand White rabbits during Days 4 to 5 after breeding. After removal of the mucin coat and the zona pellucida by pronase, the embryos were directly cultured in ES cell medium on mitomycin C-treated mouse embryonic fibroblast (MEF) or STO feeder layers. In Experiment 1, the efficiencies of 2 different feeder layers, MEF and STO, in generating rabbit ES cell lines were compared. Six blastocysts were used for each STO and MEF feeder group. The primary ICM colonies were formed in 67% (4/6) of the cultures on the STO and 83% (5/6) on the MEF. Sixty percent of those primary colonies (3/5) were successfully grown into ES-like cell lines in the MEF feeder group. However, no cell lines were established on the STO feeder. In Experiment 2, whole blastocysts or ICMs isolated by immunosurgery were cultured to establish ES cell lines. A total of 21 blastocysts were recovered from 2 does. Eighteen whole blastocysts and 3 isolated ICMs were cultured on the MEF feeders. Twelve (67%) of the cultured whole blastocysts formed primary ICM colonies, of which 5 (42%) of the cultures continuously propagated and formed ES-like cell lines. In the immunosurgical group, 2 of the 3 isolated ICMs formed primary colonies but only 1 ES-like cell line was established. A total of 9 ES-like cell lines maintained morphological undifferentiation after 14 passages and expressed alkaline phosphatase activity. Seven of the 9 ES-like cells expressed Oct-4 and the stage-specific embryonic antigen-4 (SSEA-4) as detected by immunocytochemical staining. Two cell lines were further induced to differentiate into embryoid bodies in suspension culture. Another 3 cell lines were injected into SCID mice and one of them formed a teratoma. The competence of generating chimeric rabbits and the teratogenicity of the established ES-like cell lines are under evaluation. In conclusion, rabbit ES-like cells were efficiently generated and whole-blastocyst culturing on the MEF feeder appeared to be a preferred method for the isolation and maintenance of rabbit ES-like cell lines.

215 COMPARATIVE ANALYSIS OF PORCINE PLURIPOTENT CELL LINES DERIVED FROM SOMATIC CELLS AND VARIOUS EMBRYONIC ORIGINS

2012 ◽  
Vol 24 (1) ◽  
pp. 220
Author(s):  
J. K. Park ◽  
H. S. Kim ◽  
K. J. Uh ◽  
K. H. Choi ◽  
H. M. Kim ◽  
...  
Keyword(s):  
Stem Cell ◽  
Embryonic Stem Cell ◽  
Cell Lines ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Embryonic Stem ◽  
Pluripotent Cells ◽  
Differentiation Potential

Since pluripotent cells were first derived from the inner cell mass (ICM) of mouse blastocysts, tremendous efforts have been made to establish embryonic stem cell (ESC) lines in several domestic species including the pig; however, authentic porcine ESCs have not yet been established. It has proven difficult to derive pluripotent cells of naïve state that represents full pluripotency, due to the frequent occurrence of spontaneous differentiation into an EpiSC-like state during culture in pigs. We have been able to derive EpiSC-like porcine embryonic stem cell (pESC) lines of a differentiated non-ES cell state from blastocyst stage porcine embryos of various origins, including in vitro fertilized (IVF), in vivo derived, IVF aggregated and parthenogenetic embryos. In addition, we have generated induced pluripotent stem cells (piPSCs) via plasmid transfection of reprogramming factors (Oct4, Sox2, Klf4 and c-Myc) into porcine fibroblast cells. In this study, we analysed characteristics such as marker expression, pluripotency and the X chromosome inactivation (XCI) status of our EpiSC-like pESC lines along with our piPSC line. Our results show that these cell lines demonstrate the expression of genes associated with the Activin/Nodal and FGF2 pathways along with the expression of pluripotent markers Oct4, Sox2, Nanog, SSEA4, TRA 1-60 and TRA 1-81. Furthermore all of these cell lines showed in vitro differentiation potential; female XCI activity and a normal karyotype. Here we provide preliminary results that suggest that, as a nonpermissive species, the porcine species undergoes reprogramming into a primed state during the establishment of pluripotent stem cell lines. This work was supported by the BioGreen 21 Program (#20070401034031, PJ0081382011), Rural Development Administration, Republic of Korea.

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