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Production of viable piglets for the first time using sperm derived from ectopic testicular xenografts

¹ Division of Animal Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan
² Laboratory of Animal Reproduction, School of Veterinary Medicine, Azabu University, Sagamihara, Kanagawa 229-8501, Japan

Correspondence should be addressed to K Kikuchi; Email: kiku{at}affrc.go.jp

M Nakai, H Kaneko and K Kikuchi contributed equally to this work

Xenografting of testicular tissue into immunodeficient mice is known to be a valuable tool for facilitating the development of immature germ cells present in mammalian gonads. Spermatogenesis in xenografts and/or in vitro embryonic development to the blastocyst stage after ICSI of xenogeneic sperm has already been reported in large animals, including pigs; however, development of the embryos to term has not yet been confirmed. Therefore, in pigs, we evaluated the in vivo developmental ability of oocytes injected after ICSI of xenogeneic sperm. Testicular tissues prepared from neonatal piglets, which contain seminiferous cords consisting of only gonocytes/spermatogonia, were transplanted under the back skin of castrated nude mice. Between 133 and 280 days after xenografting, morphologically normal sperm were recovered, and a single spermatozoon was then injected into an in vitro matured porcine oocyte. After ICSI, the oocytes were electrostimulated and transferred into estrus-synchronized recipients. Two out of 23 recipient gilts gave birth to six piglets. Here, we describe for the first time that oocytes fertilized with a sperm from ectopic xenografts have the ability to develop to viable offspring in large mammals.