Comparison of mechanical artificial shrinkage methods in mouse blastocyst vitrification

This study was designed to determine which mechanical artificial shrinkage (AS) method, conducted by puncture, pipetting, or aspiration, was effective in increasing the re-expansion rate of mouse blastocysts.

In each group, 30 mouse blastocysts were used. Before vitrification, the blastocoelic cavity was collapsed by puncture with a micro-needle, pipetting with a micro-glass pipette, and direct aspiration with an ICSI pipette. After thawing, the re-expansion rate of blastocysts was examined for each AS method. Re-expansion rate was checked at three, five, and seven hours after thawing.

The number of re-expanded mouse blastocysts at five hours after thawing was 12 in the puncture with a micro-needle group, 11 in the pipetting with a micro-glass pipette group, and 24 in the direct aspiration with an ICSI pipette group. The cumulative number of re-expanded mouse blastocysts at seven hours after thawing was 20 in the puncture with a micro-needle group, 20 in the pipetting with a micro-glass pipette group, and 28 in the direct aspiration with an ICSI pipette group. There were statistically significant differences in the cumulative number of re-expanded mouse blastocysts between five and seven hours after thawing (p = 0.001 and 0.021, respectively).

Direct aspiration with an ICSI pipette resulted in a higher re-expansion rate than the puncture and pipetting methods. It can be considered that the direct aspiration method is more convenient and simpler than the other two methods.