title: Effects of duration of cryo-storage of mouse oocytes on cryo-survival, fertilization and embryonic development following vitrification.
abstract: OBJECTIVE
  To investigate the effects of cryo-storage duration in liquid nitrogen on oocyte cryo-survival, fertilization and embryonic development following vitrification and warming.
  
  
  METHODS
  Mature mouse oocytes were vitrified with McGill Cryoleaf and stored in liquid nitrogen for a period of 8-10 days, 90-92 days and 180-182 days, respectively. After warming, the survived oocytes were inseminated by intracytoplasmic sperm injection (ICSI) and cultured for 120 h. The rates of oocyte cryo-survival, cleavage and embryonic development were compared.
  
  
  RESULTS
  The oocyte cryo-survival rate declined following cryo-storage duration for 180-182 days (90.4 ± 7.9%) compared to that of the other two groups (97.4 ± 3.0% and 98.0 ± 3.3%). The fertilization rate in the group of 180-182 days (66.6 ± 22.0%) was also significantly reduced (P < 0.05) compared with the groups of 8-10 days (92.2 ± 10.8%) and 90-92 days (94.7 ± 9.1%). In addition, the number of embryos developed to the blastocyst stage declined significantly (P < 0.05) following long cryo-storage duration (72.1 ± 8.2%, 25.2 ± 3.8% and 5.5 ± 13.6%, respectively).
  
  
  CONCLUSIONS
  The cryo-survival, fertilization rate and embryonic development of mouse oocytes are affected significantly, in an adverse manner, by the cryo-storage duration in liquid nitrogen.
authors.affiliation: Department of Obstetrics and Gynecology, Peking University Third Hospital, Beijing, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Yan
authors.forename: Joao
authors.initials: J
authors.lastname: Suzuki
authors.forename: Xiao-Min
authors.initials: XM
authors.lastname: Yu
authors.forename: Jie
authors.initials: J
authors.lastname: Qiao
authors.forename: Frederick W K
authors.initials: FW
authors.lastname: Kan
authors.forename: Ri-Cheng
authors.initials: RC
authors.lastname: Chian
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology*; D015925:Cryopreservation; D046149:Embryo Culture Techniques / Q000379:methods; D047108:Embryonic Development / Q000502:physiology*; D005260:Female; D005307:Fertilization in Vitro / Q000706:statistics & numerical data; D008297:Male; D051379:Mice; D009865:Oocytes / Q000166:cytology / Q000254:growth & development*; D011247:Pregnancy; D020554:Sperm Injections, Intracytoplasmic / Q000379:methods; D013094:Spermatozoa / Q000166:cytology; D058989:Vitrification