title: In-straw cryoprotectant dilution for bovine embryos vitrified using Cryotop.
abstract: The aim of this study was to develop an in-straw dilution method suitable for 1-step bovine embryo transfer of vitrified embryos using the Cryotop vitrification-straw dilution (CVSD) method. The development of embryos vitrified using the CVSD method was compared with those of embryos cryopreserved using in-straw vitrification-dilution (ISVD) and conventional slow freezing, outside dilution of straw (SFODS) methods. In Experiment 1, in vitro-produced (IVP) embryos cryopreserved using the CVSD method were diluted, warmed and exposed to the dilution solution at various times. When vitrified IVP embryos were exposed to the dilution solution for 30 min after warming, the rates of embryos developing to the hatched blastocyst stage after 72 h of culture (62.0-72.5%) were significantly lower (P<0.05) than those of embryos exposed to the solution for 5 and 10 min (82.4-94.3%), irrespective of supplementation with 0.3 M sucrose in the dilution solution. In Experiment 2, the rate of embryos developing to the hatching blastocyst stage after 48 h of culture in IVP embryos cryopreserved using the SFODS method (75.0%) was significantly (P<0.05) lower than those of embryos cryopreserved using the CVSD and ISVD methods (93.2 and 97.3%, respectively). In Experiment 3, when in vivo-produced embryos that had been cryopreserved using the CVSD, ISVD and SFODS methods and fresh embryos were transferred to recipient animals, no significant differences were observed in the conception and delivery rates among groups. In Experiment 4, when IVP embryos derived from oocytes collected by ovum pick-up that had been cryopreserved using the CVSD and ISVD methods and fresh embryos were transferred to recipient animals, no significant differences were observed in the conception rates among groups. Our results indicate that this simplified regimen of warming and diluting Cryotop-vitrified embryos may enable 1-step bovine embryo transfer without the requirement of a microscope or other laboratory equipment.
authors.affiliation: National Livestock Breeding Center, Fukushima, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Inaba
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Aikawa
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Hirai
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Hashiyada
authors.forename: Tadayuki
authors.initials: T
authors.lastname: Yamanouchi
authors.forename: Koji
authors.initials: K
authors.lastname: Misumi
authors.forename: Masaki
authors.initials: M
authors.lastname: Ohtake
authors.forename: Tamas
authors.initials: T
authors.lastname: Somfai
authors.forename: Shuji
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Norio
authors.initials: N
authors.lastname: Saito
authors.forename: Satoko
authors.initials: S
authors.lastname: Matoba
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Konishi
authors.forename: Kei
authors.initials: K
authors.lastname: Imai
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology; D002417:Cattle; D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents / Q000494:pharmacology; D046149:Embryo Culture Techniques / Q000379:methods*; D004624:Embryo Transfer; D004867:Equipment Design; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods; D005615:Freezing; D013997:Time Factors; D058989:Vitrification
chemical_list: D003451:Cryoprotective Agents