Reprod. Nutr. Dev. 42 (2002) 73-80
DOI: 10.1051/rnd:20020008

Cryopreservation of bovine oocytes: is cryoloop vitrification the future to preserving the female gamete?

Andreas Mavrides^a and David Morroll<sup>b

a</sup>  Department of Human Development, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
^b  NURTURE, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK

(Received 24 October 2001; accepted 30 January 2002)

Abstract
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.

Key words: bovine / cryoloop / ICSI / oocyte / vitrification

Correspondence and reprints: Andreas Mavrides andreas@mavrides.com

© INRA, EDP Sciences 2002