title: A closed system supports the developmental competence of human embryos after vitrification : Closed vitrification of human embryos.
abstract: OBJECTIVE
  Closed-system vitrification may enable the risk of contamination to be minimised. We performed three studies to compare the developmental competence of human embryos vitrified using either a closed vitrification system (CVS; Rapid-i®) or an open vitrification system (OVS; Cryo-top®).
  
  
  METHODS
  The first study was performed in vitro using 66 zygotes previously vitrified at pronuclear stage. These were warmed and randomised 1:1 to revitrification using either the OVS or the CVS. After re-warming, embryo development and blastocyst cell number were assessed. For the second study, also performed in vitro, 60 vitrified-warmed blastocysts were randomised 1:1:1 into three groups (OVS or CVS revitrification, or no revitrification). The proportion of dead cells was assessed by staining. The third study was performed in vivo, using 263 high-grade blastocysts randomly assigned to vitrification using either the CVS (n = 100) or the OVS (n = 163). After warming, single blastocyst transfer was performed.
  
  
  RESULTS
  There were no differences between the CVS and the OVS in survival rate (100 % vs. 97 %), blastulation rate (96 h: 50 % vs. 50 %; 120 h: 68 % vs. 56 %), proportion of good blastocysts (96 h: 32 % vs. 22 %, 120 h: 47 % vs. 41 %), or mean number of cells (137 vs. 138). The proportion of dead cells in blastocysts re-vitrified by CVS (31 %) was similar to that for OVS (38 %) and non-revitrification (32 %). In vivo, the implantation rate for blastocysts vitrified using the CVS (54 %) was similar to that with the OVS (53 %).
  
  
  CONCLUSIONS
  Our studies consistently indicate that human embryos may be vitrified using a CVS without impairment of developmental competence.
authors: IVF Namba Clinic, Osaka, Japan. hashimoto@ivfnamba.com
authors: Shu
authors: S
authors: Hashimoto
authors: Ami
authors: A
authors: Amo
authors: Satoko
authors: S
authors: Hama
authors: Kanako
authors: K
authors: Ohsumi
authors: Yoshiharu
authors: Y
authors: Nakaoka
authors: Yoshiharu
authors: Y
authors: Morimoto
mesh_terms: D001755:Blastocyst / Q000166:cytology*; D002452:Cell Count; D015925:Cryopreservation; D010064:Embryo Implantation; D004624:Embryo Transfer; D047108:Embryonic Development; D005260:Female; D006801:Humans; D011247:Pregnancy; D058989:Vitrification