The pig has been considered to serve as an appropriate model of human disease. Therefore, establishment of porcine embryonic stem cell lines is important. The purpose of the present study was to further work in this direction. We produced porcine parthenogenetic embryos, and separately aggregated two of each of two-cell (2×2), four-cell (2×4), and eight-cell (2×8) embryos derived by parthenogenesis. After culture for 4 days, the developmental ability of the aggregates and total blastocyst cell numbers were evaluated. The percentage of blastocysts was significantly higher in both 2×4- and 2×8-aggregated embryos (58.3±1.9% and 37.2±2.8%, respectively) than in the control or 2×2-aggregated embryos (23.6±1.1% and 12.5±2.4%, respectively). Total blastocyst cell numbers were increased in the 2×4- and 2×8-aggregated embryos (by 44±3.0% and 45±3.3%, respectively) compared with those of control or 2×2-aggregated embryos (30.5±2.1% and 30.7±2.6%, respectively; p<0.05). The levels of mRNA encoding Oct-4 were higher in both the 2×4- and 2×8-aggregated embryos than in the control. When blastocysts derived from 2×4- aggregated embryos or intact normal embryos were cultured on mouse embryonic fibroblast feeder cells to obtain porcine stem cells, blastocysts from aggregated embryos formed colonies that were better in shape compared with those derived from intact blastocysts. Together, the data show that aggregation of porcine embryos not only improves blastocyst quality but also serves as an efficient procedure by which porcine embryonic stem cells can become established.

ABSTRACT   INTRODUCTION   MATERIALS AND METHODS    Chemicals    In Vitro Maturation    Activation of Porcine Oocytes and In Vitro Culture    Aggregation of Embryos and In Vitro Culture    Preparation of Feeder Cells and Establishment of EmbryonicStem Cells    Real-Time Quantitative Polymerase Chain Reaction    Statistical Analysis   RESULTS    Developmental Ability of Aggregated ParthenogeneticEmbryos    Total Cell Numbers in Aggregated and Intact Embryos    Analysis of Oct-4 Transcription in Aggregated Blastocysts    Establishment of Porcine Embryonic Stem Cells   DISCUSSION   REFERENCES

• Dong Il Jin(Department of Animal Science & Biotechnology, Research Center for Transgenic Cloned Pigs, Chungnam National University, Daejeon 305-764, Korea) Corresponding author
• Je Sok Wo(National Institute of Animal Science, Suwon 441-706, Korea)
• Reza K. Oqani(Department of Animal Science & Biotechnology, Research Center for Transgenic Cloned Pigs, Chungnam National University, Daejeon 305-764, Korea)
• Yun Fei Diao(Department of Animal Science & Biotechnology, Research Center for Transgenic Cloned Pigs, Chungnam National University, Daejeon 305-764, Korea)
• Jin Yu Zhang(Department of Animal Science & Biotechnology, Research Center for Transgenic Cloned Pigs, Chungnam National University, Daejeon 305-764, Korea)