Effects of the pre-artificial shrinkage and subsequent assisted hatching on the survival and hatching rate of the vitrified mouse expanding blastocysts

Abstract

OBJECTIVE: This study was conducted to investigate the effects of the artificial shrinkage and subsequent assisted hatching(PZD;patial zona dissetion) before vitrification on the survival and hatching rate of mouse expanding blastocyst. DESIGN: Mouse 2-cell embryos were collected and cultured in G1.1 and G2.2 to expanding blastocyst. For artificial shrinkage(AS) the micro injection pipette was inserted into blastocoele cavity and blastocoele fluid was aspirated. MATERIALS AND METHODS: For assisted hatching(AH) PZD method was used. Control group was -AS/-AH and treatment groups were -AS/+AH, +AS/-AH and +AS/+AH. After AS and AH mouse blastocysts were equillibrated in G10 and G10E20 for 3min, respectively, and vitrified in G25E25 after loading on capped pulled straw. Vitrified mouse blastocysts were thawed and culture for 24hrs. The survival and hatching rate was compared among one control and three treatment groups. RESULTS: The survival rates were 99%, 92% in +AS/+AH and +AS/-AH groups and 54%, 58% in -AS/-AH and -AS/+AH group, respectively. The survival rate was higher in +AS group than in -AS group(p<0.01). Hatching rates were 34%, 96% in -AS/-AH and -AS/+AH groups and 41%, 100% in +AS/-AH and +AS/+AH, respectively. The hatching rates was higher in +AH group than in -AH group(p<0.01). After thawing recovery rates were 100%. CONCLUSIONS: This study showed that artificial shrinkage of blastocoele cavity and assisted hatching(PZD) significantly improved the survival and hatching rate of the vitrified mouse expanding blastocsts. It was considered that the capped pulled straw vitrification procedure was available for vitrification of blastocysts.