High survival and hatching rates following vitrification of embryos at blastocyst stage: a bovine model study

Cryopreservation of embryos at the blastocyst stage may provide an effective method to increase the cumulative pregnancy rate for each treatment cycle of ovarian-stimulated IVF. The objective of this study was to evaluate the survival rate and hatching rate of bovine blastocysts following vitrification using a method designed for oocytes, with a view to introducing this methodology into human assisted reproduction technology and reproductive medicine. Bovine blastocysts were produced from abattoir materials subjected to in-vitro maturation and in-vitro fertilization. Survival rate of the bovine blastocysts was 100% (94/94) following vitrification using a method designed for oocyte cryopreservation. There was no difference in the hatching rate of the bovine blastocysts between control (62.5%: 60/96) and vitrified (61.7%: 58/94) groups. The number of dead cells in the blastocysts was not significantly different between control (5.0 +/- 2.9) and vitrified (9.5 +/- 4.0) groups. In conclusion, the results of this study indicate that bovine blastocysts can be vitrified successfully using a procedure designed for oocyte cryopreservation. It is possible that this method may also be successful for the cryopreservation of human embryos. A further study into this is currently being organized.