Chromosome analysis of human refrozen embryos following fluorescence in situ hybridization
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ORIGINAL ARTICLE
Chromosome analysis of human refrozen embryos following fluorescence in situ hybridization Eiko Otsu Æ Akiko Sato Æ Takafumi Utsunomiya Æ Yasuhisa Araki Æ Seiji Ujiie
Received: 22 September 2008 / Accepted: 21 April 2009 / Published online: 19 May 2009 Ó Japan Society for Reproductive Medicine 2009
Abstract Purpose Several recent reports have discussed refrozen and thawed embryo transfer; however, the process may cause a degree of chromosomal damage and subtle genomic mutation. In view of this possibility, the purpose of this study was to investigate the incidence of aneuploidy in refrozen embryos. Methods In order to investigate the incidence of aneuploidy and mosaicism observed in chromosome 1, fluorescent in situ hybridization (FISH) was used on surviving embryos that first underwent one freeze-thaw cycle, then were allowed to develop to the blastocyst stage, and subsequently survived a second freeze-thaw cycle. Results Of 1,132 blastomeric nuclei analyzed from 15 refrozen embryos, disomy was found in 82.9%. In contrast, for the 11 blastocysts subjected to only one freeze-thaw cycle, disomy was noted in 78.4%. Of the 197 blastomeric nuclei analyzed in all arrested embryos, disomy was found in 51.8%. Conclusions The refreezing process did not increase aneuploidy. The good and fair morphology groups demonstrated a higher percentage of disomy than the poor morphology group regardless of whether they were frozen once or twice. E. Otsu (&) A. Sato T. Utsunomiya St. Luke Clinic, 5-kumi, Tomioka, Tsumori, Oita 870-0945, Japan e-mail: [email protected]
Keywords Blastocyst Chromosomal abnormalities FISH Refrozen Vitrification
Introduction Although in vitro fertilization (IVF) pregnancy rates have improved at many centers in recent years, multiple gestation remains a challenging problem. An approach that can reduce this risk is limited embryo transfer with cryopreservation of supernumerary embryos. Many patients have achieved a pregnancy using frozen embryos, and recently, investigators have reported the successful transfer of embryos subjected to two freeze-thaw cycles [1–4]. In these studies, the developmental stages of the embryos ranged from the pronuclei (2PN) stage to the blastocyst stage. However, freezing and thawing significantly reduced not only embryo viability but also the number of embryos available for uterine transfer. Furthermore, investigators cautioned that freezing and thawing of embryos may cause chromosomal damage [5]. In view of these issues, this study was designed to investigate the incidence of aneuploidy and mosaicism observed in chromosome 1 by performing fluorescent in situ hybridization (FISH) on surviving embryos that first underwent one freeze-thaw cycle, then were allowed to develop to the blastocyst stage, and subsequently survived a second freeze-thaw cycle.
Y. Araki The Institute for ARMT, 909-21, Ishii, Fujimi, Setagun, Gunma 371-0105, Japan
Materials and methods
E. Otsu S. Ujiie Department of Applied Chemistry Faculty of Engineering, Oita Univer
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