title: The location of "8"-shaped hatching influences inner cell mass formation in mouse blastocysts.
abstract: The hatching of a blastocyst where the blastocyst portions on the inside and the outside of the zona pellucida feature a figure-of-eight shape is termed "8"-shaped hatching; this type of hatching has been reported to affect the proper presentation of the inner cell mass (ICM) in both human and mouse embryos. Here, our aim was to investigate the factors that affect ICM presentation during "8"-shaped hatching. We performed IVF by using B6D2F1 female mice and ICR male mice, and used the 104 captured blastocysts. Embryos were maintained in KSOM at 37°C in a 5% CO2, 5% O2, and 90% N2 environment, and their growth behavior was monitored individually and continuously using time-lapse cinematography. At 120 h after insemination, embryos were immunostained and examined under a confocal microscope. We used the hatching form to identify "8"-shaped hatching, and we classified the "8"-shaped-hatching blastocysts into two groups, one in which the hatching site was near the ICM center, and the other in which the hatching site was far from the ICM center. We measured each group for ICM size and the number of Oct3/4-positive cells. Of the 95 hatching or hatched embryos, 74 were "8"-shaped-hatching blastocysts, and in these embryos, the ICM was significantly wider when the hatching site was near the ICM than when the hatching site was far from the ICM (P = 0.0091). Moreover, in the "8"-shaped-hatching blastocysts in which the ICM was included in the blastocyst portion outside the zona pellucida-the portion defined as the "outside blastocyst"-after the collapse of this outside blastocyst, the ICM adhered to the trophectoderm of the outside blastocyst, opposite the hatching site. Our results indicate that in "8"-shaped-hatching blastocysts, the hatching site and the collapse of outside blastocyst affect ICM formation. Thus, the assessment of "8"-shaped hatching behaviors could yield indices for accurately evaluating embryo quality.
authors.affiliation: Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan.
authors.forename: Yohei
authors.identifier: http://orcid.org/0000-0002-2357-8804
authors.initials: Y
authors.lastname: Onodera
authors.affiliation: Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan.
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Takahashi
authors.affiliation: Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Goto
authors.affiliation: Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan.
authors.forename: Mibuki
authors.initials: M
authors.lastname: Anzai
authors.affiliation: Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan.
authors.forename: Natsuki
authors.initials: N
authors.lastname: Ono
authors.affiliation: Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan.
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Shirasawa
authors.affiliation: Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Sato
authors.affiliation: Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Miura
authors.affiliation: Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Sato
authors.affiliation: Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Sato
authors.affiliation: Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan.
authors.forename: Yukiyo
authors.initials: Y
authors.lastname: Kumazawa
authors.affiliation: Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan.
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Terada
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology*; D047108:Embryonic Development; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence