title: Growth retardation in human blastocysts increases the incidence of abnormal spindles and decreases implantation potential after vitrification.
abstract: OBJECTIVE
  Does the human embryo growth rate affect the outcome of vitrified-warmed blastocyst transfer?
  
  
  CONCLUSIONS
  Following vitrification, the incidence of abnormal spindle morphology was increased and the implantation competence was decreased in growth-retarded embryos compared with normally developing embryos.
  
  
  BACKGROUND
  Various types of spindle abnormality occur in human cleavage- and blastocyst-stage embryos. However, the incidence of abnormal spindle morphology in growth-retarded blastocysts is not known. Furthermore, there is conflicting data about the implantation potential of such blastocysts.
  
  
  METHODS
  This was a retrospective cohort study including 878 single vitrified-warmed blastocyst transfers between 9 January 2010 and 10 July 2012, and an experimental study using 121 vitrified-warmed blastocysts donated to research. A comparison on the implantation potential and spindle shape of vitrified-warmed blastocysts was made between normally developing and growth-retarded blastocysts.
  
  
  METHODS
  In the clinical study, we compared the implantation rates of vitrified-warmed embryos that developed to the blastocyst stage on Day 5 after insemination (normally developing embryos) with those that required culture to Day 6 (growth-retarded embryo). In the experimental study, donated vitrified-warmed blastocysts were immunostained with an anti-α-tubulin antibody to visualize microtubules, an anti-γ-tubulin antibody to image centrosomes and Hoechst 33342 or 4,6-diamidino-2-phenylindole to visualize DNA. Confocal image analysis captured a z-series stack of 0.5-µm-thick optical sections encompassing the entire blastocyst. Only spindles with fusiform poles and with chromosomes aligned at the equator were classified as normal.
  
  
  RESULTS
  The implantation rate of growth-retarded embryos (47%, n = 270) was significantly lower (P < 0.05) than that of normally developing embryos (57%, n = 608). A total of 533 spindles were analyzed in Day 5 and 6 vitrified-warmed blastocysts. The incidence of abnormal spindles in the growth-retarded embryos (47%, n = 274) was significantly higher (P < 0.01) than in the normally developing embryos (30%, n = 259).
  
  
  CONCLUSIONS
  Further studies are required to clarify the link between an increase in abnormal spindle formation and a decrease in embryonic implantation potential.
  
  
  CONCLUSIONS
  This study provided new insights into the possible implications of abnormalities in spindle formation in growth-retarded human blastocysts.
authors.affiliation: IVF Namba Clinic, 1-17-28 Minamihorie, Nishi-ku, Osaka 550-0015, Japan. hashimoto@ivfnamba.com
authors.forename: Shu
authors.initials: S
authors.lastname: Hashimoto
authors.forename: Ami
authors.initials: A
authors.lastname: Amo
authors.forename: Satoko
authors.initials: S
authors.lastname: Hama
authors.forename: Keijiro
authors.initials: K
authors.lastname: Ito
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Nakaoka
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Morimoto
mesh_terms: D001755:Blastocyst / Q000502:physiology / Q000648:ultrastructure*; D015925:Cryopreservation; D003599:Cytoskeleton / Q000648:ultrastructure; D010064:Embryo Implantation / Q000502:physiology*; D004624:Embryo Transfer; D047108:Embryonic Development; D006801:Humans; D012189:Retrospective Studies; D008941:Spindle Apparatus / Q000502:physiology / Q000648:ultrastructure; D013997:Time Factors; D058989:Vitrification
keywords: blastocyst; embryo transfer; growth retardation; implantation; spindle formation