Cryopreservation of hamster oocytes: effects of vitrification or freezing on human sperm penetration of zona-free hamster oocytes.
Three experiments were conducted for evaluation of the efficacy of conventional freezing or vitrification of hamster oocytes for use in a human sperm penetration assay (hSPA). In experiment 1, oocytes were cryopreserved and evaluated for survival on the basis of morphologic criteria. Survival of vitrified oocytes and that of frozen oocytes were not different, whereas all cryopreserved groups had lower survival than noncryopreserved controls. In experiment 2, oocytes were conventionally frozen or vitrified and evaluated in an hSPA. Vitrified oocytes had a lower frequency of sperm penetration than frozen oocytes, and all cryopreserved groups had lower penetration rates than untreated controls. In experiment 3, oocytes were exposed to the cryoprotectant used to vitrify (VS1) or freeze (DMSO) but not cooled prior to evaluation in an hSPA. Exposure to DMSO but not VS1 reduced hSPA values. It is concluded from these experiments that while all cryopreserved oocytes do not survive, at current stages of development conventionally frozen oocytes perform better than vitrified oocytes in the hSPA and losses associated with conventional freezing procedures may be related to cryoprotectant exposure, whereas vitrification losses are more probably due to events associated with rapid cooling and/or warming of the oocytes.
D000818:Animals; D006224:Cricetinae; D003451:Cryoprotective Agents / Q000494:pharmacology; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D005260:Female; D005615:Freezing; D006801:Humans; D007248:Infertility, Male / Q000175:diagnosis; D008297:Male; D008647:Mesocricetus; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D013084:Sperm-Ovum Interactions / Q000187:drug effects
D003451:Cryoprotective Agents; D004121:Dimethyl Sulfoxide