Institute of Livestock and Grassland Science, NARO

Embryo Production Research Unit

The aim of our research is to develop an efficient system of "in vitro production", "cryopreservation" and "selection" of sperm and oocytes of domestic animals, which together can make fertilized eggs with high abilities to develop to term after embryo transfer. Oocytes are the source of future eggs stored in large quantities in the ovaries, though 99.9% of those are to be lost in the ovary. Therefore, we are developing a culture system to provide an artificial condition for such oocytes to grow up and mature to be used for in vitro fertilization. Sperm are prepared abundantly by nature in male animals. Then, selecting only excellent sperm and oocytes that have high abilities among abundant pools will be crucial. We have been working on in the aim of establishing techniques and criteria for such selection. Furthermore, we are also developing technology to preserve the excellent oocytes, sperm and fertilized eggs until they are in need in future without compromising their abilities.

A calf derived from an in vitro grown oocyte cultured for 2 weeks

Unit Leader


Unit Members

Research Publications

  • Morohaku K, Tanimoto R, Sasaki K, Kawahara-Miki R, Kono T, Hayashi K, Hirao Y, Obata Y (2016) Complete in vitro generation of fertile oocytes from mouse primordial germ cells, Proc Natl Acad Sci USA 113(32): 9021-9026
  • Hikabe O, Hamazaki N, Nagamatsu G, Obata Y, Hirao Y, Hamada N, Shimamoto S, Imamura T, Nakashima K, Saitou M, Hayashi K (2016) Reconstitution in vitro of the entire cycle of the mouse female germ line. Nature 539: 299-303
  • Appeltant R, Somfai T, Maes D, VAN Soom A, Kikuchi K (2016) Porcine oocyte maturation in vitro: role of cAMP and oocyte-secreted factors - A practical approach. J Reprod Dev 62(5): 439-449
  • Inaba Y, Abe R, Geshi M, Matoba S, Nagai T, Somfai T (2016) Sex-sorting of spermatozoa affects developmental competence of in vitro fertilized oocytes in a bull-dependent manner. J Reprod Dev 62(5): 451-456
  • Suttirojpattana T, Somfai T, Matoba S, Parnpai R, Nagai T, Geshi M (2016) Effect of medium additives during liquid storage on developmental competence of in vitro matured bovine oocytes. Anim Sci J 2016 May 12. doi: 10.1111/asj.12623
  • Parnpai R, Liang Y, Ketudat-Cairns M, Somfai T, Nagai T (2016) Vitrification of buffalo oocytes and embryos. Theriogenology 86(1): 214-220
  • Inaba Y, Miyashita S, Somfai T, Geshi M, Matoba S, Dochi O, Nagai T (2016) Cryopreservation method affects DNA fragmentation in trophectoderm and the speed of re-expansion in bovine blastocysts.Cryobiology 72(2): 86-92