Transfer of Inner Cell Mass Cells Derived from Bovine Nuclear Transfer Embryos into the Trophoblast of Bovine In Vitro-Produced Embryos

Abstract

Presence of placental tissues from more normal noncloned embryos could reduce the preg­ nancy failure of somatic cloning in cattle. In this study, inner cell mass (ICM) cells of in vitro-produced UVP) embryos was replaced with those of nuclear transfer (NT) embryos to reconstruct bovine blastocysts with ICM and trophoblast cells from NT and IVP embryos, re­ spectively. A total of 65 of these reconstructed embryos were nonsurgically transferred to 20 recipient beef females. Of those, two females were diagnosed pregnant by ultrasonography on day 30 of gestation. One pregnancy was lost at 6G-90 days of gestation, and the other re­ cipient cow remained pregnant at day 240.of gestation; however, this female died on day 252 of gestation.Gross pathology of the internal organs of the recipient female, a large fetus, and a large placental tissue mass suggested the massive size of the fetus and placental tissue were likely involved in terminating the life of the recipient female. Biopsy samples were harvested from the skin of the dead recipient cow, the fetus and from cotyledonary tissue. Microsatel­ lite DNA analysis of these samples revealed that the genotype of the fetus was the same as that of the NT donor cells and different from that of the recipient cow. Correspondingly, nei­ ther the fetus nor recipient cow had the same genotype with that of the fetal cotyledonary tis­ sue. These results present the first known documented case of a bovine somatic NT preg­ nancy with nonclone placental tissues after transfer of a blastocyst reconstructed by a microsurgical method to exchange of ICM cells and trophoblast tissue between NT and IVP blastocysts.