title: Highly efficient vitrification method for cryopreservation of human oocytes.
abstract: Two experiments were performed to develop a method to cryopreserve MII human oocytes. In the first experiment, three vitrification methods were compared using bovine MII oocytes with regard to their developmental competence after cryopreservation: (i) vitrification within 0.25-ml plastic straws followed by in-straw dilution after warming (ISD method); (ii) vitrification in open-pulled straws (OPS method); and (iii) vitrification in <0.1 microl medium droplet on the surface of a specially constructed fine polypropylene strip attached to a plastic handle (Cryotop method). In the second experiment, the Cryotop method, which had yielded the best results, was used to vitrify human oocytes. Out of 64 vitrified oocytes, 58 (91%) exhibited normal morphology after warming. After intracytoplasmic sperm injection, 52 became fertilized, and 32 (50%) developed to the blastocyst stage in vitro. Analysis by fluorescence in-situ hybridization of five blastocysts showed that all were normal diploid embryos. Twenty-nine embryo transfers with a mean number of 2.2 embryos per transfer on days 2 and 5 resulted in 12 initial pregnancies, seven healthy babies and three ongoing pregnancies. The results suggest that vitrification using the Cryotop is the most efficient method for human oocyte cryopreservation.
authors.affiliation: Kato Ladies' Clinic, Tokyo, Japan. masaabc@bokkoame.ne.jp
authors.forename: Masashige
authors.initials: M
authors.lastname: Kuwayama
authors.forename: Gábor
authors.initials: G
authors.lastname: Vajta
authors.forename: Osamu
authors.initials: O
authors.lastname: Kato
authors.forename: Stanley P
authors.initials: SP
authors.lastname: Leibo
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology / Q000502:physiology; D002417:Cattle; D015925:Cryopreservation / Q000295:instrumentation / Q000379:methods*; D004624:Embryo Transfer; D019855:Ethylene Glycol / Q000494:pharmacology; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D011247:Pregnancy; D011256:Pregnancy Outcome; D018873:Pregnancy Rate; D020554:Sperm Injections, Intracytoplasmic
chemical_list: D019855:Ethylene Glycol