title: Comparison of ethylene glycol and propylene glycol for the vitrification of immature porcine oocytes.
abstract: Our aim was to optimize a cryoprotectant treatment for vitrification of immature porcine cumulus-oocyte complexes (COCs). Immature COCs were vitrified either in 35% ethylene glycol (EG), 35% propylene glycol (PG) or a combination of 17.5% EG and 17.5% PG. After warming, the COCs were in vitro matured (IVM), and surviving oocytes were in vitro fertilized (IVF) and cultured. The mean survival rate of vitrified oocytes in 35% PG (73.9%) was higher (P<0.05) than that in 35% EG (27.8%). Oocyte maturation rates did not differ among vitrified and non-vitrified control groups. Blastocyst formation in the vitrified EG group (10.8%) was higher (P<0.05) than that in the vitrified PG group (2.0%) but was lower than that in the control group (25.0%). Treatment of oocytes with 35% of each cryoprotectant without vitrification revealed a higher toxicity of PG on subsequent blastocyst development compared with EG. The combination of EG and PG resulted in 42.6% survival after vitrification. The maturation and fertilization rates of the surviving oocytes were similar in the vitrified, control and toxicity control (TC; treated with EG+PG combination without cooling) groups. Blastocyst development in the vitrified group was lower (P<0.05) than that in the control and TC groups, which in turn had similar development rates (10.7%, 18.1% and 23.3%, respectively). In conclusion, 35% PG enabled a higher oocyte survival rate after vitrification compared with 35% EG. However, PG was greatly toxic to oocytes. The combination of 17.5% EG and 17.5% PG yielded reasonable survival rates without toxic effects on embryo development.
authors.affiliation: NARO Institute of Livestock and Grassland Science, Ibaraki 305-0901, Japan.
authors.forename: Tamás
authors.initials: T
authors.lastname: Somfai
authors.forename: Michiko
authors.initials: M
authors.lastname: Nakai
authors.forename: Fuminori
authors.initials: F
authors.lastname: Tanihara
authors.forename: Junko
authors.initials: J
authors.lastname: Noguchi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kaneko
authors.forename: Naomi
authors.initials: N
authors.lastname: Kashiwazaki
authors.forename: István
authors.initials: I
authors.lastname: Egerszegi
authors.forename: Takashi
authors.initials: T
authors.lastname: Nagai
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kikuchi
mesh_terms: D000818:Animals; D015925:Cryopreservation / Q000662:veterinary*; D003451:Cryoprotective Agents / Q000494:pharmacology*; D047108:Embryonic Development / Q000502:physiology; D019855:Ethylene Glycol / Q000494:pharmacology*; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods / Q000662:veterinary; D008297:Male; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D019946:Propylene Glycol / Q000494:pharmacology*; D013552:Swine / Q000502:physiology*; D058989:Vitrification
chemical_list: D003451:Cryoprotective Agents; D019946:Propylene Glycol; D019855:Ethylene Glycol