文摘
To improve the vitrification of mouse oocytes using straws, we attempted to estimate the type and extent of injuries during vitrification with a vitrification solution EAFS10/10. Injuries in oocytes were assessed based on cellular viability, the integrity of the plasma membrane, the status of the meiotic spindle/chromosomes, and morphological appearance. For morphologically normal oocytes, the ability to be fertilized and to develop into blastocysts was examined. Morphological assessment revealed 15 % of oocytes to be injured by intracellular ice formed during vitrification, and 10 % by osmotic swelling during removal of the cryoprotectant. When assessed by the status of spindles/chromosomes, the most sensitive criterion, damage was found in 16 % of oocytes without any treatment. This value was similar to the proportion of fresh oocytes that did not cleave after insemination (13 % ). On exposure to EAFS10/10, the spindles/chromosomes were affected in 33 % of oocytes. The exposure reduced the rate of cleavage by 18 % points and the rate of development into blastocysts by 19 points. Vitrification reduced these rates by 15 % and 36 % points, respectively. Although the mechanism responsible for this moderate toxic effect on developmental ability is not known, information obtained in the present study will be useful to develop a practical method for the vitrification of mouse oocytes using straws.