Effects of the Artificial Shrinkage and Assisted Hatching Before Vitrification on the Development of the Vitrified Mouse Expanding Blastocysts

Jo, Deok Hyeon; Ko, Gyoung Rae; Jung, Ji Hye; Choi, Jong Ryeol; Joo, Jong Kil; Lee, Kyu Sup

Abstract

OBJECTIVE
This study was conducted to investigate the effects of the artificial shrinkage and assisted hatching (PZD; patial zona dissetion) before vitrification on the development of vitrified mouse expanding blastocyst.
METHODS
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. 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 3 mins, respectively, and vitrified in G25E25 after loading on capped pulled-straw. Vitrified mouse blastocysts were thawed and cultured for 24 hrs. 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 significantly 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%. Loading on capped pulled-straw, that is effective and useful method on vitrification.
CONCLUSION
This study showed that artificial shrinkage of blastocoele cavity and assisted hatching (PZD) significantly improved the development of the vitrified mouse expanding blastocysts.