Developmental assessment of human vitrified-warmed blastocysts based on oxygen consumption

BACKGROUND In this study, we aimed to develop a model for embryo selection based on oxygen consumption following cryopreservation, the relationship between the developmental competence of blastocysts and their oxygen consumption was assessed. METHODS Oxygen consumption of vitrified-warmed human blastocysts was measured at 0, 1.5, 3, 4.5, 6, 7.5, 9 and 24 h after warming using scanning electrochemical microscopy. On the basis of their developmental stage at 24 h, blastocysts were classified into four groups (hatched, hatching, arrested and degenerated). Moreover, cytochrome c oxidase (CCO) activity in vitrified-warmed blastocysts was assessed at 0 and 24 h. RESULTS The oxygen consumption rate of blastocysts just after warming was significantly lower than that of non-vitrified blastocysts (P< 0.05). The oxygen consumption rate of blastocysts was significantly higher in the hatched group than in the arrested and the degenerated groups after 1.5 h (P< 0.05) and than in the hatching group (P< 0.05) at 7.5 and 9 h. Moreover, CCO activity was absent in vitrified-warmed blastocysts at 0 h, but was detected at 24 h. CONCLUSIONS The respiratory rate of vitrified blastocysts after warming was significantly lower than non-cryopreserved blastocysts. Oxygen consumption of blastocysts with high developmental potential was restored earlier than that of blastocysts with low developmental potential. The results of this study suggest that it is possible to select vitrified-warmed blastocysts with high developmental potential based on their respiratory activity.