Comparison of Vitrification and Slow Freezing for the Cryopreservation of Mouse Pronuclear Stage Embryos.

Kim,  Mi Young; Lee,  Yu Il

Original Article

Korean Journal of Reproductive Medicine 2007;34(2):117-124.
Published online June 1, 2007.

Comparison of Vitrification and Slow Freezing for the Cryopreservation of Mouse Pronuclear Stage Embryos.

Mi Young Kim, Yu Il Lee

Department of Obstetrics and Gynecology, Chonnam National University Medical School, Gwangju, Korea.

Abstract

OBJECTIVE
The aim of this study was to compare the efficacy of slow freezing with vitrification method for cryopreservation of mouse pronuclear stage embryos. METHODS: Mouse pronuclear embryos obtained from superovulated mice and classified into 2 groups of slow freezing and vitrification. Slow freezing solution consisted of 1.5 M PROH, 0.1 M sucrose, while vitrification solution consisted of 40% ethylene glycol, 18% Ficoll and 0.5 M sucrose diluted in Dulbecco's phosphate-buffered saline supplemented with 10% SSS. Recovery and survival rates after thawing and development rates to hatching balstocyst stage were compared between two groups. RESULT: After freezing and thawing, recovery rate of slow freezing group was 93.8%, whereas vitrification group was 66.5% (p<0.01). Survival rate of recovered embryos were similar between two groups as 83.2% in slow freezing and 87.6% in vitrification. Embryo development rates to 2-cell stage after 24 hrs (77.0% vs 59.1%), 4-cell after 48 hrs (72.6% vs 53.3%), blastocyst after 96 hrs (53.1% vs 40.1%) of thawing were significantly higher in vitrification group than those of slow freezing group, respectively. CONCLUSION: The vitrification method may provide better developmental competence of frozen-thawed embryos than that of slow freezing method for cryopreservation of mouse pronuclear stage embryos.

Key Words: Mouse pronuclear embryo; Vitrification; Slow freezing; Embryo development; Blastocyst