Cryoloop vitrification in assisted reproduction: analysis of survival rates in > 1000 human oocytes after ultra-rapid cooling with polymer augmented cryoprotectants.
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 survival and/or morphology.
Liebermann
J
J
Department of Gynecology and Obstetrics, University of Würzburg, Würzburg, Germany.
Tucker
M J
MJ
Sills
E S
ES
D002470:Cell Survival; D002478:Cells, Cultured; D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents; D005260:Female; D005307:Fertilization in Vitro; D006358:Hot Temperature; D006801:Humans; D009865:Oocytes / Q000502:physiology*; D011108:Polymers; D027724:Reproductive Techniques, Assisted; D020554:Sperm Injections, Intracytoplasmic
D003451:Cryoprotective Agents; D011108:Polymers