202209Ito

研究発表を行った学会；
Society for the Study of Reproduction 55th Annual Meeting
2022年7月26-29日　（ワシントン州 スポケーン, USA）
タイトル； Synchronizing ovulation and mating timing achieved triple yield of two-cell embryos in superovulated female mice.
発表者；伊藤　琴乃氏
（熊本大学　生命資源研究・支援センター　資源開発分野）
要旨；
In mammals, sperm ejected into the vagina travels from the uterus to the oviduct and reaches the ovulated oocyte and has success in fertilization. In mature female mice, 8-10 oocytes are ovulated following the estrus cycle and almost all oocytes are fertilized by mating with male mice. On the other hand, there is the limitation of fertilized oocytes ovulated by superovulation treatment. Previously, we developed an ultrasuperovulation technique using inhibin antiserum and equine chorionic gonadotropin (IASe) that allows producing 100 oocytes from a single female mouse at 4-weeks old. After mating with the superovulated female mouse using IASe and matured male mice, about 20 oocytes were fertilized. We hypothesized that the low efficiency of fertilization in superovulated female mice may be lacking enough number of sperm in the ampulla. In this study, we examined the effects of ovulation and mate timing on fertilization rate. First, we checked the ovulation timing and classified the three periods, pre- (conventional mating time), during-, and post-ovulation. Mated female mice at during- and post-ovulation showed higher fertilization rates than female mice at pre-ovulation (pre: 20.0±20.5% vs during: 71.2±23.5% vs post: 75.6±17.2%). The number of embryos obtained at post-ovulation was three times higher than at pre-ovulation. After embryo transfer, the fertilized oocytes were normally developed into live pups. These results suggested that synchronizing the timing of ovulation and mating increased the fertilization rate. The technique will be applicable to efficiently produce in vivo fertilized oocytes used for making genetically modified mice and achieve the reduction of animal numbers following the 3Rs principle.