title: Cryopreservation of human embryos using ethylene glycol in controlled slow freezing.
abstract: BACKGROUND
  Ethylene glycol (EG) has been successfully used as a cryoprotectant for vitrification of mammalian formula embryos (including human embryos) due to its low formula weight and high permeation into cells compared with other cryoprotectants, including propylene glycol (PROH). This study was carried out to evaluate the permeation and toxicity of EG and to investigate the effects of its use in a slow-freezing protocol on post-thaw development of mouse embryos and on pregnancy outcome of frozen human embryos.
  
  
  METHODS
  Spare human embryos after embryo transfer were cryopreserved using 1.5 mol/l EG or PROH using a slow-freezing protocol which had been tested previously in mouse experiments.
  
  
  RESULTS
  The post-thaw survival rate of human embryos in the EG group (80.6%) was significantly higher than that in the PROH group (65.2%, P < 0.05). The implantation and clinical pregnancy rates of human embryos in the EG group (20.3 and 46.9%) were significantly higher than those in the PROH group (7.5 and 24.6%, P < 0.05).
  
  
  CONCLUSIONS
  Ethylene glycol may be a good substitute for PROH to cryopreserve human embryos using a slow-freezing protocol.
authors.affiliation: IVF Center, Hanna Women's Clinic and Department of Animal Sciences, Kon-Kuk University, Seoul, Korea. hanna129@hanmail.net
authors.forename: Hee-Jun
authors.initials: HJ
authors.lastname: Chi
authors.forename: Jung-Jin
authors.initials: JJ
authors.lastname: Koo
authors.forename: Moon-Young
authors.initials: MY
authors.lastname: Kim
authors.forename: Jin-Young
authors.initials: JY
authors.lastname: Joo
authors.forename: Sang-Sik
authors.initials: SS
authors.lastname: Chang
authors.forename: Kil-Saeng
authors.initials: KS
authors.lastname: Chung
mesh_terms: D000328:Adult; D000818:Animals; D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents / Q000493:pharmacokinetics / Q000633:toxicity; D010064:Embryo Implantation; D004624:Embryo Transfer; D004622:Embryo, Mammalian / Q000187:drug effects / Q000502:physiology; D019855:Ethylene Glycol / Q000493:pharmacokinetics / Q000633:toxicity; D005260:Female; D006801:Humans; D051379:Mice; D011247:Pregnancy; D011256:Pregnancy Outcome; D018873:Pregnancy Rate; D011446:Prospective Studies; D013997:Time Factors; D014022:Tissue Survival
chemical_list: D003451:Cryoprotective Agents; D019855:Ethylene Glycol