In vitro development of bovine embryos cultured in a frozen-thawed commercial culture medium

Abstract

As in vitro fertilization (IVF) becomes more acceptable for the treatment of human infertility, it is essential for clinics to have in place an optimal embryo culture system. The objective of this study was to evaluate whether freezing and storing human embryo culture medium will alter embryo post-thaw viability. In consecutive experiments, commercial culture medium was frozen at -20°C and at -80°C and stored at 4°C until its use in IVF. Each IVF-derived replicate of bovine embryos contained a laboratory control group, a fresh commercial culture medium group(s) and a frozen-thawed commercial culture medium group(s). The commercial culture medium was supplemented with 15% of BSA for days 1 through 4 of in vitro culture and on day 4 was supplemented with 9% of glucose. Embryos were cultured to day 8 of the experiment and then embryo development was evaluated and morphology was evaluated using the RED Score system. In Experiment 1, zygotes (n=2,094) were in vitro cultured in medium that had been frozen (-20°C) with storage times ranging from 3 days to 10 weeks. It was found that embryo culture medium frozen at -20°C and stored for up to 10 weeks did not cause a decrease in 8- to 16-cell embryo or blastocyst development for those embryos cultured in medium frozen for 3 days to 6 weeks over the fresh medium (0 weeks). In Experiment 2, zygotes (n=3,727) were in vitro cultured in both fresh and frozen commercial culture medium (-80°C) that was stored for 0, 1 or 2 weeks before use. This study indicated embryo culture medium frozen at -80°C stored for up to 2 weeks did not cause a decrease in 8- to 16-cell embryo or blastocyst development over that of the fresh medium (0 week). In summary, it was concluded that there was no difference in the blastocyst development rate or morphology at the end of the culture period in medium frozen at -20°C for up to 10 weeks or in medium frozen at -80°C for up to 2 weeks.