Jeong Mook Lim

Engineering integrin signaling for promoting embryonic stem cell self-renewal in a precisely defined niche

We present development and use of a 3D synthetic extracellular matrix (ECM) analog with integrin-specific adhesion ligands to characterize the microenvironmental influences in embryonic stem cell (ESC) self-renewal. Transcriptional analysis of 24 integrin subunits followed by confirmation at the translational and functional levels suggested that integrins alpha(5)beta(1), alpha(v)beta(5), alpha(6)beta(1) and alpha(9)beta(1) play important roles in maintenance of stemness in undifferentiated mouse ESCs. Using the well-defined matrix as a tool to activate integrins alpha(5)beta(1) plus alpha(v)beta(5), alpha(6)beta(1) and alpha(9)beta(1), individually and in combination, differential integrin activation was demonstrated to exert exquisite control over ESC fate decisions. Simultaneous ligation of these four integrin heterodimers promoted self-renewal, as evidence by prolonged SSEA-1, Oct4 and Nanog expression, and induced Akt1 kinase signaling along with translational regulation of other stemness-related genes. The biofunctional network we have designed based on this knowledge may be useful as a defined niche for regulating ESC pluripotency through selective cell-matrix interactions, and the method we present may be more generally useful for probing matrix interactions in stem cell self-renewal and differentiation.

Improved Germline Transmission in Chicken Chimeras Produced by Transplantation of Gonadal Primordial Germ Cells into Recipient Embryos

Abstract In the avian species, germline chimera production could be possible by transfer of donor germ cells into the blood vessel of recipient embryos. This study was conducted to establish an efficient transfer system of chicken gonadal primordial germ cells (gPGCs) for producing the chimeras having a high capacity of germline transmission. Gonadal PGCs retrieved from 5.5-day-old embryos (stage 28) of Korean Ogol chicken (KOC with i/i gene) were transferred into the dorsal aorta of 2.5-day-old embryos (stage 17) of White Leghorn chicken (WL with I/I gene). Prospective evaluations of whether culture duration (0, 5, or 10 days) and subsequent Ficoll separation of gPGCs before transfer affected chimera production and germline transmission in the chimeras were made while retrospective analysis was conducted for examining the effect of chimera sexuality. A testcross analysis by artificial insemination of presumptive chimeras with adult KOC was performed for evaluating each treatment effect. First, comparison was made for evaluating whether experimental treatments could improve chimera production, but none of the treatments were significantly (P = 0.6831) influenced (5.1%–14.4%). Second, it was determined whether each treatment could enhance germline transmission in produced chimeras. More (P < 0.0001) progenies with black feathers (i/i) were produced in the germline chimeras derived from the transfer of 10-day-cultured gPGCs than from the transfer of 0- or 5-day-cultured gPGCs (0.6%–7.8% vs. 10.7%–49.7%). Ficoll separation was negatively affected (P < 0.0001), whereas there was no effect in chimera sexuality (P = 0.6011). In conclusion, improved germline transmission of more than a 45% transmission rate was found in chicken chimeras produced by transfer of 10-day-cultured gPGCs being separated without Ficoll treatment.

Production of germline chimeras by transfer of chicken gonadal primordial germ cells maintained in vitro for an extended period

We previously reported that germline chimeras could be produced by transfer of chicken gonadal primordial germ cells (gPGCs) cultured for a short term (5 days). This study was subsequently undertaken to examine whether gPGCs maintained in vitro for an extended period could retain their specific characteristics to induce germline transmission. Chicken (White Leghorn, WL) gPGCs were retrieved from embryos at stage 28 (5.5 days of incubation) and continuously cultured for 2 months in modified Dulbeccos minimal essential medium without subpassage and changing of the feeder cell layer. After the identification of gPGC characteristics using Periodic acid-Shiffs (PAS) reaction and anti stage-specific embryonic antigen-1 (SSEA-1) antibody staining at the end of the culture, cultured gPGCs were injected into the dorsal aorta of Korean Ogol Chicken (KOC) recipient embryos at stage 17 (2.5 days of incubation). Nineteen chickens (13 males and 6 females) were hatched, grown to sexual maturity, and subsequently subjected to testcross analysis employing artificial insemination with adult KOC. Of these, four (three males and one female) hatched chickens with white coat color. The percentage of germline chimerism was 21% (4/19). The results of this study demonstrated that gPGCs could maintain their specific characteristics for up to 2 months in vitro, resulting in the birth of germline chimeras following transfer to recipient embryos.

Development of Novel Markers for the Characterization of Chicken Primordial Germ Cells

This study was undertaken to develop novel markers for chicken primordial germ cells (PGCs), which are of potentially enormous value in transgenic research. Gonadal cells collected from 5.5‐day‐old chicken embryos were cultured in a Dulbeccos minimal essential medium and the PGC colonies formed during the primary culture period were subcultured three times. Characterization of the PGCs with the candidate marker reagents was performed on the mixed cell population 2 hours after seeding, after the primary culture period (day 10), and after the third passage (day 40). Mouse embryonic stem (ES) cells were used as controls. The cytochemical reagents investigated included periodic acid‐Schiff (PAS) stain, antibodies to stage‐specific embryonic antigens (SSEA‐1, SSEA‐3, and SSEA‐4), antibody to epithelial membrane antigen (EMA)‐1, antibodies to integrins α6 and β1, several lectins (Solanum tuberosum agglutinin [STA], Dolichos biflorus agglutinin [DBA], concanavalin A agglutinin [ConA], and wheat germ agglutinin [WGA]), and double staining with antibodies to SSEA‐1, SSEA‐3, SSEA‐4, integrin α6, or integrin β1 and then with the lectin STA. Densitometric quantification was used to identify PGC‐specific markers. The results showed that chicken PGCs were stained selectively by PAS and by antibodies to SSEA‐1, SSEA‐3, SSEA‐4, EMA‐1, integrin α6, and integrin β1. The control mouse ES cells reacted with PAS, anti‐SSEA‐1, and anti‐EMA‐1 antibodies, as well as with antibodies to integrins α6 and β1, but not with antibodies to SSEA‐3 and SSEA‐4. Chicken PGCs reacted with the lectins STA and DBA, but mouse ES cells reacted with STA and WGA. The results of double staining of PGC colonies subcultured three times showed that the intensity of staining was not altered by concomitant use of the marker reagents. This study demonstrated that, in addition to PAS and antibodies to SSEA‐1 and EMA‐1, new specific markers of chicken PGCs are recognized by the lectins STA and DBA and by antibodies to SSEA‐3 and SSEA‐4 and inte‐grins α6 and β1. Double staining using these newly developed markers might be the method of choice for rapid characterization of chicken PGCs.

Anthocyanin stimulates in vitro development of cloned pig embryos by increasing the intracellular glutathione level and inhibiting reactive oxygen species

The objective was to examine the nuclear maturation of oocytes, embryonic development after parthenogenetic activation (PA) and somatic cell nuclear transfer (SCNT), and gene expression in SCNT embryos in pigs (Sus scrofa) when anthocyanin was added to oocytes during maturation and in vitro culture (IVC) of embryos. Immature oocytes were untreated or treated with 0.1 microg/mL anthocyanin during in vitro maturation (IVM). Next, PA and SCNT embryos were produced from oocytes and cultured in medium supplemented with or without 0.1 microg/mL anthocyanin for 7 d. Anthocyanin treatment during IVM did not improve the nuclear maturation of oocytes, but significantly increased intracellular glutathione (GSH) levels and reduced reactive oxygen species (ROS). Oocytes treated with anthocyanin during IVM had higher (P < 0.05) rates of blastocyst formation after PA (55.7 vs. 44.9 %) and SCNT (32.2 vs. 16.1%) compared to untreated oocytes. In PA and SCNT embryos, anthocyanin treatment during IVM or IVC significantly increased the intracellular GSH level, which led to the reduced ROS level. Somatic cell nuclear transfer embryos derived from anthocyanin-treated oocytes had increased (P < 0.05) expression of DNMT1, PCNA, FGFR2, and POU5F1 mRNA compared to control embryos. In conclusion, anthocyanin treatment during IVM improved developmental competence of SCNT embryos, most likely by increasing intracellular GSH synthesis, reducing ROS level, and stimulating nuclear reprogramming via increased transcription factor expression.

Improvement of a porcine somatic cell nuclear transfer technique by optimizing donor cell and recipient oocyte preparations

This study was conducted to improve a porcine somatic cell nuclear transfer (SCNT) technique by optimizing donor cell and recipient oocyte preparations. Adult and fetal fibroblasts, and cumulus and oviduct cells were used as donor cells, and in vivo- and in vitro-matured oocytes were employed as recipient oocytes. The percentages of fusion and development to the blastocyst stage, the ratio of blastocysts to 2-cell embryos, and cell number of blastocysts were monitored as experimental parameters. In Experiment 1, donor cells of four different types were transferred to enucleated oocytes matured in vitro, and more (P < 0.05) blastocysts were derived from SCNT of fetal fibroblasts than from that of other cells (15.9% versus 3.1-7.9%). For SCNT using fetal fibroblasts, increasing the number of subcultures up to 15 times did not improve developmental competence to the blastocyst stage (12.2-16.7%). In Experiment 2, fetal fibroblasts were transferred to enucleated oocytes that matured in vivo or in vitro. When parthenogenetic activation of both types of oocytes was conducted as a preliminary control treatment, a significant increase in blastocyst formation was found for in vivo-matured compared with in vitro-matured oocytes (36.4% versus 29.5%). However, no improvement was achieved in SCNT using in vivo-matured oocytes. In conclusion, the type of donor somatic cell is important for improving development after porcine SCNT, and fetal fibroblasts were the most effective among examined cells. A system with good reproducibility has been established using fetal fibroblasts as the donor karyoplast after subculturing 1-10 times, and using both in vivo and in vitro-matured oocytes as the recipient cytoplast.

Reproduction of Wild Birds via Interspecies Germ Cell Transplantation

Abstract The present study was conducted to apply an interspecies germ cell transfer technique to wild bird reproduction. Pheasant (Phasianus colchicus) primordial germ cells (PGCs) retrieved from the gonads of 7-day-old embryos were transferred to the bloodstream of 2.5-day-old chicken (Gallus gallus) embryos. Pheasant-to-chicken germline chimeras hatched from the recipient embryos, and 10 pheasants were derived from testcross reproduction of the male chimeras with female pheasants. Gonadal migration of the transferred PGCs, their involvement in spermatogenesis, and production of chimeric semen were confirmed. The phenotype of pheasant progenies derived from the interspecies transfer was identical to that of wild pheasants. The average efficiency of reproduction estimated from the percentage of pheasants to total progenies was 17.5%. In conclusion, interspecies germ cell transfer into a developing embryo can be used for wild bird reproduction, and this reproductive technology may be applicable in conserving endangered bird species..

Generation of transgenic quail through germ cell-mediated germline transmission

Here, we describe the production of transgenic quail via a germline transmission system using postmigratory gonadal primordial germ cells (gPGCs). gPGCs retrieved from the embryonic gonads of 5‐day‐old birds were transduced with a lentiviral vector and subsequently transferred into recipient embryos. Testcross and genetic analyses revealed that among three germline chimeric G0 quail, one male produced transgenic offspring;of 310 hatchlings from the transgenic germline chimera, 24 were identified as donor‐derived offspring, and 6 were transgenic (6/310, 1.9%). Conventional transgenesis using stage × blastodermal embryos was also conducted, but the efficiency of transgenesis was similar between the two systems (<1.6 vs. 1.9% for the conventional and gPGC‐mediated systems, respectively). However, substantial advantages can be gained from gPGC‐mediated method in that it enables an induced germline modification, whereas direct retroviral transfer to stage X embryos causes mosaic integration. The use of gonadal PGCs for transgenesis may lead to the production of bioreactors.—Shin, S. S., Kim, T. M., Kim, S. Y., Kim, T. W., Seo, H. W., Lee, S. K., Kwon, S. C., Lee, G. S., Kim, H., Lim, J. M., Han, J. Y. Generation of transgenic quail through germ cell‐mediated germline transmission. FASEB J. 22, 2435–2444 (2008)

A Testis-Mediated Germline Chimera Production Based on Transfer of Chicken Testicular Cells Directly into Heterologous Testes

Abstract In this study, we proposed a testis-mediated germline chimera production system based on the transplantation of testicular cells directly into heterologous testes. The testicular cells of juvenile (4-wk-old) or adult (24-wk-old) Korean Ogol chickens with a recessive pigmentation inhibitory gene, with or without prior culture, were injected (2 × 107 cells/head) into the seminiferous tubules of juvenile or adult recipients with White Leghorn with a dominant pigmentation inhibitory gene in a 2 × 2 factorial arrangement. The localization of transplanted cells into the inner space of the seminiferous tubules was confirmed within 24 h after injection. Subsequent testcross analyses showed that 7.8% (5/64) of the recipients had chimeric status in their testes. The periods of time from transfer to hatching of the first progeny with black feathers were 38 and 45 days for adult cells transplanted into an adult recipient, 188 days for adult cells into a juvenile recipient, and 137 days for juvenile cells into a juvenile recipient. Culture of the testicular cells derived both colony-forming and monolayer-forming cells. The colony-forming cells were stained positively for periodic acid Schiff solution, and further reacted with anti-SSEA-1, anti-SSEA-3, and anti-SSEA-4 antibodies both before and after culture for 15 days. In conclusion, it may be possible to develop the testis-mediated germline chimera production technique, which extends the feasibility of genetic manipulations in avian species.

Embryonic stem cell-like cells established by culture of adult ovarian cells in mice

OBJECTIVE To suggest an alternative strategy for deriving histocompatible stems cells without undertaking genetic manipulation. DESIGN Prospective approach using an animal model. SETTING Stem cell and bioevaluation laboratory, Seoul National University. ANIMAL(S) F1 (C57BL6 X DBA2) and outbred (ICR) mice. INTERVENTION(S) Ovarian stroma cells of less than 40 mum in diameter were subcultured with fibroblast monolayer, and colony-forming cells were characterized. MAIN OUTCOME MEASURE(S) Stemness, genotype, and imprinted gene methylation. RESULT(S) Two-lines of colony-forming cells were established, which expressed markers specific for embryonic stem cells (ESC) and formed embryoid bodies and teratomas. Complete matching of microsatellite markers with the cell donor strain confirmed their establishment from ovarian tissue, and identification of both homozygotic and heterozygotic chromosomes raised the possibility of their derivation from parthenogenetic oocytes. However, the use of cells smaller than mature oocytes for primary culture, the difference in imprinted gene methylation compared with parthenogenetic ESCs, and failure to establish the ESC-like cells by primary follicle culture collectively suggested the irrelevancy to gametes. CONCLUSION(S) Coculture of adult ovarian cells with somatic fibroblasts can yield colony-forming cells having ESC-like activity, which may provide an alternative for establishing autologous stem cells from adults that can be obtained without genetic manipulation.