Mouse blastocyst previtrification interventions and DNA integrity.

Objective: To assess the effect of implementing different previtrification interventions on the postwarming DNA integrity of vitrified blastocysts.

Design: Prospective in vitro study.

Setting: Center for Reproductive Medicine laboratory in a tertiary hospital setting.

Animals: A total of 70 expanded and 46 nonexpanded mouse blastocysts were used for the study.

Intervention(s): [1] Twenty-two expanded blastocysts were blastocele aspirated and immediately vitrified. [2] Twelve expanded blastocysts were spontaneously hatched before vitrification. [3] Twenty-two expanded blastocysts were vitrified without intervention. [4] Sixteen nonexpanded blastocysts underwent assisted hatching using acidified Tyrode's solution. [5] Seventeen nonexpanded blastocysts were vitrified without intervention. [6] Thirteen nonexpanded blastocysts and 14 expanded were used as fresh controls. Vitrification was done using a cryotip loading device.

Main Outcome Measure(s): DNA integrity index using terminal deoxynucleotide transferase [TdT]-mediated dUTP-digoxigenin nick-end labeling staining and confocal imaging.

Result(s): [1] Intervention by blastocele aspiration for expanded blastocysts or assisted hatching of nonexpanded blastocysts significantly improved the postwarming results in each blastocyst stage. [2] Allowing spontaneous hatching before vitrification is a noninvasive technique that can improve the postwarming integrity of expanded blastocysts similar to blastocele aspiration.

Conclusion(s): Blastocele aspiration or spontaneous hatching of expanded blastocysts and assisted hatching of nonexpanded blastocysts before vitrification helps minimize blastomere DNA damage.