Closed-system solid surface vitrification versus slow programmable freezing of mouse 2-cell embryos

Abstract

To compare closed-system solid surface vitrification with slow freezing. Mouse 2-cell embryos (n = 348) were divided into vitrification, slow freezing and non-frozen groups. For vitrification, embryos were exposed to 10% ethylene glycol (EG), 10% dimethylsulfoxide (DMSO) and 10% fetal bovine serum (FBS) in phosphate-buffered saline (PBS) for 10 min, then transferred into 17.5% EG, 17.5% DMSO, 0.25 M trehalose and 10% FBS in PBS. They were placed on hemi-straws and inserted into 0.5 ml straws inside a previously cooled aluminum cylinder. Slow freezing was done in straws by the conventional method. Vitrified embryos had significantly higher survival, further cleavage and blastocyst formation rates than those in the slow freezing group (p < 0.001) and were comparable to controls. Blastocysts in the vitrification and control groups had significantly more cells than those in the slow freezing group (p < 0.05). Closed-system vitrification was more effective than conventional slow freezing.