Effect of vitrification on apoptotic changes in feline embryos

The aim of this study was to evaluate the influence of a vitrification-warming procedure on the viability of cat embryos and blastocysts and the incidence of apoptotic changes in blastocysts subjected to vitrification and blastocyst that developed from vitrified embryos. In the first part of the experiment, post-thaw embryo development and blastocyst viability were evaluated based on morphological appearance and the ability to develop (embryos) or re-expand (blastocyst) compared to control. In the second part, blastocysts that were viable after vitrification-warming and blastocysts that developed from vitrified-warmed embryos were stained with Annexin-V and TUNEL to evaluate apoptotic changes. Most of the vitrified-warmed embryos were viable after thawing, 36.3% developed to morula, and 14.7% to the blastocyst stage. The overall re-expansion rate of blastocysts that were vitrified on day 7 was 55.6%. Vitrification significantly increased apoptotic and necrotic changes in blastocysts, but did not influence late apoptotic and necrotic changes in blastocysts that developed from vitrified-warmed embryos. The total number of blastomeres in blastocysts was similar in blastocysts that developed from vitrified-warmed embryos (99.1 ± 23.1), but lower in blastocysts vitrified on day 7 (82.1 ± 16.8), if compared to the control group (107.9 ± 24.2). These results show that the vitrification-warming procedure returns embryos capable of further development to a good quality blastocyst in vitro. Whereas, vitrification of blastocysts caused the progression of apoptotic changes in some blastomeres, however it did not affect the overall blastocyst viability.