Hyperacute rejection (from pig to human) is thought to result from activation of complement initiated by the binding of host natural antibodies to α‐galactosyl (α‐Gal) epitopes of donor endothelial cells. However, α‐Gal epitope shares a common precursor with H antigen in humans. This means that H antigens as well as α‐Gal epitopes are synthesized in a competitive manner by different enzymes. We thought that it would be possible to convert α‐Gal epitopes into H antigens by introducing cDNA of α(1,2)‐fucosyltransferase (α1–2FT) into porcine cells, and so, pig embryos were microinjected with αl‐2FT cDNA. Transgenic pigs that carried α1–2FT were thus established. Cytotoxicity of fibrocytes derived from skin of transgenic pig was measured by 51Cr release assay, which showed that H antigen‐expressing cells were significantly resistant to a challenge with human sera. These experiments indicate that our method provides a new strategy which contributes to a successful discordant xenotransplantation.

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Conventionally, in vitro-fertilized (IVF) bovine embryos for transfer are morphologically evaluated at day 7-8 of embryo culture. This method is, however, subjective and results in unreliable selection. We previously described a novel selection system for IVF bovine blastocysts for transfer that traces the development of individual embryos with time-lapse monitoring in our specially developed microwell culture dishes (LinKID micro25). The system can noninvasively identify prognostic factors that reflect viability after transfer. By assessing a combination of identified prognostic factors-timing of the first cleavage; number of blastomeres at the end of the first cleavage; and number of blastomeres at the onset of lag-phase, which results in temporary developmental arrest during the fourth or fifth cell cycle-the pregnancy rate was improved over using conventional morphological evaluation. Time-lapse monitoring with LinKID micro25 could facilitate objective and reliable selection of healthy IVF bovine embryos. Here, we review the novel bovine embryo selection system that allows for prediction of viability after transfer.

In this study, the quality (number of cells) and pregnancy rates of bovine blastocysts produced by in vitro maturation/in vitro fertilization (IVM/IVF) following cultivation in either cell-free culture or co-culture were compared. Bovine one-cell IVM/IVF embryos obtained 6 h after insemination were stripped of cumulus cells and assigned to either cell-free culture or co-culture with granulosa cell monolayers for 9 days (Expt 1) or 10 days (Expts 2 and 3). In Expt 3, day-7 (day 0 = day of insemination) blastocysts, day-8 expanded blastocysts and day-9 hatched blastocysts were air-dried, fixed and stained to determine the number of cells. Expanded blastocysts obtained in Expt 1 were cryopreserved using propylene glycol as a cryoprotectant and were used later for embryo transfer. There were no significant differences between cell-free culture and co-culture in the percentage of one-cell

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