Vitrification of mouse oocytes results in aneuploid zygotes and malformed fetuses

Vitrification of mouse oocytes adversely affected the subsequent developmental potential of embryos and fetuses derived from the fertilization of such oocytes after thawing. Only 5% of oocytes vitrified formed viable fetuses on the 15th day of gestation as compared to 47% in the controls. The incidence of chromosomally aneuploid zygotes, derived from cryopreserved oocytes, was approximately threefold higher than the controls irrespective of whether the oocytes were cryopreserved by vitrification or DMSO slow-freezing. Malformed fetuses were obtained from oocytes that had been vitrified as well as those that had been exposed to vitrification solutions only, whereas no malformed fetuses were obtained in oocytes slow-frozen by DMSO or fresh controls--thus demonstrating that the exposure of oocytes to the vitrification chemicals was responsible for the fetal malformations. The data in this study suggest that the vitrification technique should be cautiously applied to human oocyte cryopreservation. Furthermore, the data also demonstrate that the exposure of female gametes to carcinogenic and/or teratogenic chemicals may result in malformed embryos when such oocytes are subsequently fertilized.