Effect of human chorionic gonadotropin and progesterone administration on the developmental potential of mouse somatic cell nuclear-transferred oocytes

Somatic cell nuclear-transferred (SCNT) oocytes have a relatively high potential to develop into blastocysts in vitro, but a large proportion embryos die at various pre- and postimplantation stages after transfer to recipients. Although the reason for the high mortality of SCNT embryos at the peri- and postimplantation stages is not clear, epigenetic abnormalities of SCNT embryos are considered to be the main cause. Such abnormalities of SCNT embryos may decrease their ability to maintain the corpora lutea, which is necessary for initiating implantation and maintaining fetal development. To examine this hypothesis, human chorionic gonadotropin (hCG) and progesterone were administered at different times to recipients that received SCNT embryos. When hCG was administered daily from day 3.5 to day 6.5 of pregnancy, the implantation and fetal development rates increased significantly compared to those of controls. The potential of SCNT embryos to develop to full term, however, was not greater than that of controls, even if hCG administration was continued to day 11.5 or day 17.5 and progesterone was administered from day 7.5 to day 17.5 after hCG injection. These findings demonstrated that administering hCG to recipients protects the in vivo development of SCNT embryos until day 10.5, but other treatment is necessary to support the progression of the embryos to full-term development.