50 Development of a Modified Straw Loading Method for Vitrification of in Vitro-Produced Bovine Blastocysts

Abstract

This study evaluated a modified plastic straw method for vitrification of in vitro-produced (IVP) bovine blastocysts. A modified straw was used that has a depressed area on its inner surface to which embryos attach. The IVP blastocysts were randomly assigned into 3 groups: (1) attachment of embryos to the inner surface of a plastic straw (aV), (2) attachment of embryos to the inner surface of a modified plastic straw (maV), and (3) non-vitrified (control). The recovery rates of blastocysts were not significantly different between the aV and maV groups (95.8 v. 94.3%; P > 0.05). The survival of post-thaw blastocysts did not significantly differ between the aV and maV groups (86.4 v. 88.2%; P > 0.05). The total cell number of blastocysts was significantly higher in the control group than in the aV and maV groups (142 ± 21.8 v. 117 ± 29.7 and 120 ± 25.2; P < 0.05), but not different between the aV and maV groups. The mRNA levels of the pro-apoptosis-related genes Bax and caspase-3 were significantly higher in the aV and maV groups than in the control group. By contrast, the mRNA levels of Bcl-2 and Mcl-1, which are anti-apoptotic genes, and of MnSOD and Prdx5, which are antioxidant-related genes, were significantly lower in the aV and maV groups than in the control group (P < 0.05). In conclusion, the aV and maV methods can be used to vitrify IVP bovine blastocysts, and embryos are more easily loaded using the maV method than using the aV method. This work was partly supported by the Next-Generation BioGreen 21 Program (grant no. PJ009587022013), IPET (grant no. 110020-5 and 112020-3), and a scholarship from the BK21 Program, Republic of Korea.