title: The effect of minimal concentration of ethylene glycol (EG) combined with polyvinylpyrrolidone (PVP) on mouse oocyte survival and subsequent embryonic development following vitrification.
abstract: OBJECTIVE
  Vitrification techniques employ a relatively high concentration of cryoprotectant in vitrification solutions. Exposure of oocytes to high concentrations of cryoprotectant is known to damage the oocytes via both cytotoxic and osmotic effects. Therefore, the key to successful vitrification of oocytes is to strike a balance between the usage of minimal concentration of cryoprotectant without compromising their cryoprotective actions.
  
  
  METHODS
  The minimal concentration of ethylene glycol (EG) on mouse oocyte survival and subsequent embryonic development was evaluated following vitrification-warming and parthenogenetic activation. Polyvinylpyrrolidone (PVP) combined with EG on mouse oocyte survival and subsequent embryonic development as well as morphology of the spindle and chromosome alignment were also evaluated. Vitrification system was adapted with JY Straw and the cooling rate was approximately 442-500 °C/min. In contrast, the warming rate was approximately 2,210-2,652 °C/min.
  
  
  RESULTS
  Survival rate of oocytes increased significantly when 15 % EG was combined with 2 % PVP in vitrification solution (VS). The effect of combination of EG and PVP was not significant when the concentration of EG was 20 % and higher. Although there were no significant differences in embryonic development, the percentage of abnormal spindle and chromosome alignment was significantly higher in the oocytes without 2 % PVP in VS.
  
  
  CONCLUSIONS
  Our data provide a proof of principle for oocyte vitrification that may not require a high concentration of cryoprotectant. There are synergic effects of EG combined with PVP for oocyte vitrification, which may provide important information to the field in developing less cytotoxic VS.
authors.affiliation: Center for Reproductive Medicine, Key Laboratory for Assisted Reproduction and Genetics, Department of Obstetrics and Gynecology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Wang
authors.forename: Osamu
authors.initials: O
authors.lastname: Okitsu
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Zhao
authors.forename: Yun
authors.initials: Y
authors.lastname: Sun
authors.forename: Wen
authors.initials: W
authors.lastname: Di
authors.forename: Ri-Cheng
authors.initials: RC
authors.lastname: Chian
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D047108:Embryonic Development / Q000187:drug effects*; D019855:Ethylene Glycol / Q000494:pharmacology*; D005260:Female; D005307:Fertilization in Vitro; D059471:In Vitro Oocyte Maturation Techniques; D051379:Mice; D009865:Oocytes / Q000187:drug effects* / Q000502:physiology; D011205:Povidone / Q000494:pharmacology*; D058989:Vitrification / Q000187:drug effects*
chemical_list: D003451:Cryoprotective Agents; D019855:Ethylene Glycol; D011205:Povidone