31 PORCINE SKIN-DERIVED STEM CELLS MAY BE A SUPERIOR SOURCE OF DONOR NUCLEI FOR EFFICIENT GENETIC MODIFICATION OF CLONED EMBRYOS

Somatic cell nuclear transfer (SCNT) in pigs relies primarily on the utilization of fetal-derived fibroblast cells, and the resultant clones tend to exhibit a significant level of phenotypic instability, which may be due to epigenetic reprogramming and/or genomic damage in the donor cells. In addition to the compromised phenotypic stability, production of transgenic clones through SCNT is inefficient, because the restricted lifespan of somatic donor cells in culture can be limiting when the genetic modification requires selection. In contrast, stem cells proliferate rapidly and do not undergo senescence at a high rate, so the selection process can be extended. Since there is no report of an embryonic stem cell line derived in the pig that could contribute to the germ line, we decided to investigate the utility of porcine skin-derived stem cells (SSCs). Porcine SSCs were isolated from the skin on the back of day 35 to 50 Yorkshire fetuses. The SSCs were cultured continually in SSCs medium (DMEM/F12 containing B-27, 20 ng mL–1 of epidermal growth factor, and 40 ng mL–1 of basic fibroblast growth factor) at 37.8°C, 5% CO2, 95% air. The SSCs expressed the neural progenitor marker nestin, as well as genes that are critical for pluripotency, such as Oct4 and Stat3. The SSCs proliferated actively in vitro and retained a normal karyotype after long-term culture. Electron microscopy revealed 2 distinct cell types within the spheres; elongated cells at the sphere periphery had invaginated nuclear envelopes and prominent nucleoli, and these cells displayed few, but large elongated mitochondria with transversal cristae as well as large cisternae of rough endoplasmic reticulum. In contrast, the cells in the center of the spheres were predominantly round-shaped, with a large round nucleus or cuboidal. The SSCs can be genetically modified with long-term positive selection, and 50 μg mL–1 G418 appeared to be an appropriate dose of G418 for selection of the transfected SSCs. Finally, NT embryos reconstructed with SSCs showed high rates of pre- and post-implantation development.The cell number in the blastocyst stage embryos derived from cloning with the SSC was significantly higher than those of the blastocysts derived from IVF (28.5 ± 1.9, 16.8 ± 4.0, respectively, P < 0.05), although there was no significant difference in blastocyst formation rates between these groups (21 to 25%). Three of the animals became pregnant in 4 surrogate gilts which received cloned embryos and reached to term. Two healthy male cloned piglets and 1 healthy female cloned piglet are genetically identical to the SSCs. Funding for this study was provided by the National Institutes of Health.

33 PRE-AND POST-IMPLANTATION DEVELOPMENT OF EMBRYOS CLONED FROM PORCINE SKIN-DERIVED SPHERE STEM CELLS

Although transgenic animals have been successfully cloned, the process is still inefficient. One of the limitations is the use of somatic donor cells that have a limited lifespan. If a genetic modification is made, the selection process must be initiated and completed rapidly or the cells will undergo senescence. Identification of a stem cell that would proliferate rapidly and not undergo senescence would prove to be very valuable. Here we report attempts at cloning by using porcine skin-derived sphere stem cells to determine if they are a suitable donor cell type. Skin-derived stem cells were isolated from fetal skin and express the neural progenitor marker NES, as well as genes that may be critical for pluripotency such as POU5F1 and STAT3. The skin-derived stem cells proliferate rapidly in vitro and retain a normal karyotype after long-term culture. In the present study, skin-derived stem cells were cultured and frozen in liquid nitrogen from passage 1 to passage 8. To investigate the developmental potential of the skin-derived stem cells, we performed nuclear transfer (NT) and compared their preimplantation developmental efficiency to that of the embryos derived from in vitro fertilization (IVF). Cumulus–oocyte complexes (COCs) were aspirated from antral follicles of ovaries from prepubertal gilts. Approximately, groups of 50-70 COCs were matured in vitro in 500 µL TCM-199 per culture well for 40–44 h at 38.5�C, in a humidified atmosphere of 5% CO2 in air. The donor cells were thawed and cultured one day before NT; skin-derived stem cells were pipetted vigorously in PBS-EDTA to isolate individual cells. For IVF, cryopreserved ejaculated spermatozoa were thawed and washed and then resuspended with fertilization medium (mTBM). The MII oocytes were co-incubated with sperm for 6 h, and then transferred to PZM3 and cultured. For NT and IVF, respectively, the percent cleavage at 48 h in PZM3 was 64.9 � 8.2% (169/208) and 62.1 � 3.1% (94/184) (P > 0.05), the percent blastocysts after 6 days was 21.5 � 5.8% (53/208) and 25.2 � 3.4% (46/184) (P > 0.05), and the number of nuclei per blastocyst was 28.5 � 1.9 (NT, maximum was 58) and 16.8 � 4.0 (IVF, maximum was 31) (P < 0.05). To determine development post-implantation, some cloned embryos were cultured in PZM3 for 15.5 h and an average of 112 cloned embryos were transferred to the oviducts of four naturally cycling gilts on Day 0–1 of standing estrus. Three of the animals were pregnant: one of them farrowed two male piglets on August 14th, with the other two due on September 8th and 9th. Future studies will involve performing NT and ET on skin-derived stem cells from a higher passage number to determine if they would be suitable for genetic modification prior to NT.

[Expression of bcl-2 in the normal endometrium and endometrium of adenomyosis]

Using immunohistochemical ABC staining, we detected the expression and role of bcl-2 in normal endometrium(n = 17) and eutopic and ectopic endometrium with adenomyosis(n = 16) during the menstrual cycle. The first result was that the expressions of bcl-2 in the eutopic endometrium were the same as the normal endometrium, showing predominantly in the glandular epithelial cells, and obviously cyclic changes throughout the menstrual cycle. This result suggests that these changes may be regulated by ovarian hormone and play an important role in the proliferation and physiologic death of normal endometrial glandular epithelial cells to regulate the menstrual cycle. Bcl-2 expression in the glandular cells of ectopic endometrium of adenomyosis had no cyclic change and bcl-2 staining had remained in the whole menstrual cycle. The second result suggests that the above mentioned phenomena may play an important role in the pathogenesis of adenomyosis.

[Effects of c-erbB(2) on the hCG-induced progesterone production of rat luteal cells]

The effects of c-erbB(2) antisense oligodeoxynucleotides (antisense c-erbB(2) ODN) on hCG-induced progesterone production of isolated rat luteal cells in relation to cAMP, Ca(2+) and cycloheximide (CYX) were investigated. Antisense c-erbB(2) ODN inhibited hCG-induced progesterone production in a dose-dependent manner; and the percentage of luteal cells stained for c-erbB(2) protein was decreased. But nonsense tat ODN had no similar effect. The effect of dbcAMP was in contrast with that of antisense c-erbB(2) ODN, which suppressed the progesterone production and reduced the percentage of luteal cells stained for c-erbB(2) protein. On the other hand, both verapamil and CYX enhanced the inhibition of antisense c-erbB(2) ODN. The result of the present investigation suggests that cAMP, Ca(2+)-dependent pathway participates in the expression of protooncogene.