Cryopreservation of bovine oocytes: is cryoloop vitrification the future to preserving the female gamete?
The cryoloop is a technique where a thin nylon loop is used to suspend a film of cryoprotectant containing the oocytes and directly immersing them in liquid nitrogen. 508 bovine oocytes were collected, of these 351 were cryopreserved by slow freezing using standard straws or a new vitrification method using our self-constructed cryoloops and the remainder were controls. After thawing, the oocytes were inseminated by ICSI or standard IVF. The cryoloop vitrification method yielded a survival rate of 90.5% and the slow freezing technique a rate of 54.4% (p < 0.0001). When ICSI was performed, cryopreservation by the cryoloop vitrification method resulted in very similar cleavage rate to controls (16.0% vs. 17.3%) but slow freezing produced a slightly lower rate (9.4%). Cleavage rates after IVF in fresh oocytes was higher than the cryopreservation groups (49.5% vs. 15.4% and 25.8%), whereas after ICSI the rates were similar in all groups (17.3% vs. 9.4% and 16%). It is concluded that the new cryoloop vitrification technique followed by ICSI produce good embryo formation results and they could hold the future for effective oocyte cryopreservation.
Department of Human Development, University of Nottingham, Queen's Medical Centre, UK. andreas@mavrides.com
Andreas
A
Mavrides
David
D
Morroll
D000818:Animals; D002417:Cattle; D002470:Cell Survival; D015925:Cryopreservation / Q000295:instrumentation / Q000379:methods / Q000662:veterinary*; D003451:Cryoprotective Agents / Q000494:pharmacology; D019855:Ethylene Glycol; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods / Q000662:veterinary*; D005615:Freezing; D008845:Microinjections / Q000662:veterinary; D009865:Oocytes / Q000166:cytology*; D011247:Pregnancy
D003451:Cryoprotective Agents; D019855:Ethylene Glycol