title: The CryoLoop facilitates re-vitrification of embryos at four successive stages of development without impairing embryo growth.
abstract: BACKGROUND
  Vitrification has been shown to be an effective method of cryopreservation, but little is known about re-vitrification of embryos. This study investigated the effect of re-vitrification on mouse embryo preimplantation development and viability post-transfer.
  
  
  METHODS
  Mouse embryos at the 1-cell stage were vitrified using the CryoLoop technique. Embryos were warmed and then re-vitrified successively at the 2-, 8-cell and blastocyst stages. The effects of multiple rounds of vitrification on development, differentiation and viability were assessed and compared with non-vitrified embryos.
  
  
  RESULTS
  Development to the 8-cell stage on day 3 and blastocyst on day 5 were not affected by re-vitrification. However, better hatching rates were observed in the non-vitrified control group. Total cell number and the number of cells allocated to the inner cell mass (ICM) were not different between treatments. The percentage of ICM development was also not different between treatments. Implantation rate and fetal weights were the same between treatments. However, overall there were fewer fetuses per embryo transferred in the re-vitrified group.
  
  
  CONCLUSIONS
  Re-vitrification of mouse embryos has minimal effect on preimplantation embryo development or implantation potential.
authors.affiliation: Research Department, Colorado Center for Reproductive Medicine, Englewood, CO 80113, USA.
authors.forename: Courtney B
authors.initials: CB
authors.lastname: Sheehan
authors.forename: Michelle
authors.initials: M
authors.lastname: Lane
authors.forename: David K
authors.initials: DK
authors.lastname: Gardner
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000502:physiology; D002470:Cell Survival; D015925:Cryopreservation / Q000379:methods*; D004475:Ectoderm / Q000502:physiology; D004624:Embryo Transfer; D047108:Embryonic Development; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D009924:Organ Culture Techniques / Q000379:methods; D011247:Pregnancy