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.
Mavrides
Andreas
A
Department of Human Development, University of Nottingham, Queen's Medical Centre, UK. andreas@mavrides.com
Morroll
David
D
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