Effect of Vitrification on Survival and Chromosomal Abnormalities of Frozen- Thawed 8-Cell Mouse Embryos

Cryopreservation of supernumerary human embryos derived from assisted reproduction technology (ART) procedures has provided patients the option of storage of gametes and embryos for future treatment. However, because of technical problems embryo freezing is not a routine procedure in all ART centers. This study was designed to compare the post-thaw survival and chromosomal aberrations caused by vitrification on vitrified 8-cell mouse embryos by control group. In this exprimental study using flashing method eight-cell mouse embryos were obtained from NMRI mouse 3 days after mating. Retrieved embryos were transferred in to vitrification solution containing ethylene glycol as cryoprotectant, then transferred into a vitrification straw using standard technique, and vitrified in liquid Nitrogen. Four groups of embryos including controls according to the time of vitrification, from 24 hours to 1 month were frozen. After appropriate freezing time embryos were thawed and studied for their viability and chromosomal abnormalities after thawing. Viability of frozen embryos reduced from 98.2% to 79.2% after 1 month vitrification. Furthermore, chromosomal aberrations significantly increased with increasing freezing time (p<0.01). This study indicates that freezing affects viability of embryos and chromosome structure compared to the control group. Effects of vitrification might produce chromosomal alterations leading to cell death. These alterations might probably be due to cytoskeleton, spindle or other cellular organelle damages.