Effects of vitrification medium composition on the survival of bovine in vitro produced embryos, following in straw-dilution, in vitro and in vivo following transfer.

摘要

This study examined the effects of adding a macromolecule, polyvinylpyrrolidone (10% PVP) and a sugar (0.3 M trehalose) to vitrification solutions (VS) containing 1 (40% ethylene glycol, EG), 2 (25% EG + 25% dimethyl sulphoxide, DMSO) or 3 (20% EG +20% DMSO + 10% 1.3-butanediol, BD) permeable cryoprotectants on the survival and hatching of in vitro produced cattle embryos, following vitrification, warming and in-straw cryoprotectant dilution. Grades 1 and 2 compact morulae and blastocysts were selected on day 7 (day 0 = IVF) of culture in SOFaaBSA and equilibrated for 10 min at room temperature in 10% EG. Following exposure, for up to 1 min at 4oC, to 1 of the VS (with or without PVP + trehalose), the embryos were loaded into straws and immersedin liquid nitrogen. Following warming and in-straw cryoprotectant dilution, the embryos were cultured for 48 h to assess hatching. There was no effect of VS on the survival of embryos after 24 h. However fewer compact morulae than blastocysts survived after 24 h (24 vs. 75%; P<0.001) or hatched after 48 h (15 vs. 59%; P<0.001). When blastocysts only were considered, there was an interaction (P<0.01) between VS and additional PVP + trehalose. Hatching was reduced when they were added to 25% EG + 25% DMSO(70% vs. 45%) but was not affected for 40% EG (44 and 49%) or to 20% EG + 20% DMSO + 10% BD (72 and 72%). Pregnancy rates (day 90 ultrasound) of recipients following transfer of 2 non-vitrified or 2 vitrified (20% EG + 20% DMSO + 10% BD) blastocysts, did not differ (50 (3/6) vs. 55% (11/20)). However, fewer (P<0.02) recipients that received compact morulae maintained pregnancy to day 90 although this was not affected by vitrification (fresh vs. vitrified; 20 (1/5) vs. 17% (3/18)). It is concluded thata VS containing 3 cryoprotectants rather than 1, enables more embryos to hatch during post-thaw culture, and that the survival, following direct transfer of these vitrified embryos, is not different to non-vitrified embryos.