View article

While human oocytes have been successfully cryopreserved using traditional slow-rate freezing protocols, inconsistent results post-thaw have limited the routine clinical application of oocyte cryopreservation. Despite interest in the potential benefits of vitrification as an alternative laboratory approach to long-term oocyte preservation in assisted reproduction, there is little agreement on how best to configure such cryopreservation protocols to optimize oocyte viability. To comparepost-thaw oocyte survival rates, we performed cryoloop vitrification of human oocytes utilizing two different cryoprotectant mixtures that included polymer macromolecules. Human oocytes (n= 1120) were obtained from consenting patients undergoing in vitro fertilization, but only failed-matured (uninseminated) or failed-fertilized (inseminated but without 2pn development) were included in this investigation. Protocol A consisted of 20% ethylene glycol and 20% dimethyl sulphoxide+ 0.4 M sucrose and 20% synthetic serum substitute. Protocol B consisted of 20% ethylene glycol and 20% dimethyl sulphoxide+ 0.65 M sucrose, 1 mg/ml polyethylene glycol, 10 mg/ml Ficoll and 20% synthetic serum substitute. Following cryostorage for 10-14 d at-196 degrees C, the survival rate for oocytes vitrified with protocol A was 80.9%, whereas the post-thaw viability among protocol B oocytes was 80.6%(p> 0.005). Our results indicate that an ethylene glycol+ dimethyl sulphoxide mixture (with or without polymer macromolecules) can be an effective cryoprotectant strategy for human oocyte vitrification; either approach can be employed without any observed compromise in post-warming …