title: Effect of the timing of the first cleavage on the developmental potential of nuclear-transferred mouse oocytes receiving embryonic stem cells.
abstract: The present study examined whether the timing of the first cleavage has an effect on the in vitro and in vivo developmental potential of nuclear-transferred mouse oocytes receiving embryonic stem cells. First, the timing of the first cleavage and the developmental potential of nuclear-transferred oocytes were examined every hour from 12 to 24 h after the start of culture and compared with in vitro-fertilized oocytes. The developmental potential of in vitro-fertilized oocytes decreased gradually according to the time required for cleavage (84% (32/38) for 15 h to 50% (1/2) for 20 h), but intermediate-cleaved (15-16 h) nuclear-transferred oocytes had a higher potential to develop into blastocysts (55% (17/31) to 67% (45/67) versus 0-43% (6/14)]. Second the nuclear-transferred oocytes were divided into three groups according to the timing of the first cleavage; each group was cultured to blastocysts in vitro, and then transferred to recipients. The potential of intermediate-cleaved oocytes (15-16 h) to develop into blastocysts was significantly higher than fast-cleaved (before 15 h) and slow-cleaved (after 16 h) oocytes (65, 46, and 37%). The proportion of fetuses on Day 10.5 of pregnancy was highest in the intermediate-cleaved group (4 versus 2 and 1%, respectively) and a full-term fetus was obtained from this group. The present study demonstrated that the timing of the first cleavage could be used to determine the potential of nuclear-transferred oocytes with embryonic stem cells to develop to the blastocyst stage in vitro, but not to determine post-implantation viability after transfer to recipients.
authors.affiliation: Laboratory of Animal Reproduction, College of Agriculture, Kinki University, 3327-204, Nakamachi, Nara 631-8505, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Y
authors.initials: Y
authors.lastname: Kato
authors.forename: Y
authors.initials: Y
authors.lastname: Tsunoda
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000502:physiology; D002970:Cleavage Stage, Ovum; D019976:Cloning, Organism; D046508:Culture Techniques; D004624:Embryo Transfer; D004622:Embryo, Mammalian / Q000166:cytology*; D005260:Female; D005307:Fertilization in Vitro; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D053652:Nuclear Transfer Techniques; D009865:Oocytes / Q000502:physiology / Q000648:ultrastructure*; D011247:Pregnancy; D013234:Stem Cells / Q000648:ultrastructure*; D013997:Time Factors