Discipline: Animal Science
Preantral follicles which were enzymatically or mechanically isolated from mouse ovaries were exposed either to 2-mole ethylene glycol (EG) for 2 or 5 min or to ascending concentration (0.15 then 0.3 mole) of raffinose for 2 and 5 min each before exposure to the vitrification solution (VS) for 0.5,1, or 2 min and then vitrified. After warming, the mechanically isolated follicles showed higher survival than enzymatically isolated follicles, regardless of the periods of exposure to EG or raffinose and exposure to VS. Mechanically isolated follicles exposed to 2-mole EG for 5 min and then to VS for 0.5 or 1 min showed the highest survival. They were then treated with collagenase and cultured in vitro for 10 days. After culture in vitro, the proportion of viable oocyte-ganulosa cell complexes from vitrified follicles was 10% lower than that of the fresh preantral follicles. There was no difference in the rates of maturation, fertilization, and subsequent development to blastocysts between the oocytes derived from vitrified preantral follicles and fresh preantral follicles. One of the 5 recipients which received 20 blastocysts derived from vitrified preantral follicles gave birth to 6 live pups. The results of the present study demonstrate for the first time that mouse preantral follicles can be vitrified and that some of the embryos derived from vitrified preantral follicles can develop to live pups.