title: The effect of artificial shrinkage and assisted hatching on the development of mouse blastocysts and cell number after vitrification.
abstract: OBJECTIVE
  The goal of this study was to ascertain optimal assisted hatching (AH) method in frozen embryo transfer. We compared the effect of depending on whether mechanical or laser-AH was performed before or after the vitrification of embryo development rate and blastocyst cell numbers.
  
  
  METHODS
  In order to induce superovulation, pregnant mare's serum gonadotropin followed by human chorionic gonadotropin were injected into 4- to 5-week-old female mice. 2-cell embryos were then collected by flushing out the oviducts. The Expanded blastocysts were recovered after the collected embryos were incubated for 48 hours, and were then subjected to artificial shrinkage (AS) and cross-mechanical AH (cMAH) or quarter-laser zona thinning-AH (qLZT-AH) were carried out using the expanded blastocysts before or after vitrification. After 48 hours of incubation, followed by vitrification and thawing (V-T), and blastocysts were fluorescence stained and observed.
  
  
  RESULTS
  The rate of formation of hatched blastocysts after 24 and 72 hours of incubation was significantly higher in the AS/qLZT-AH/V-T group than in the other groups (p<0.05). The cell number of the inner cell mass was higher in AS/V-T/non-AH and AS/V-T/cMAH groups than those of others (p<0.05). In the control group, the number of trophectoderm and the total cell number were higher than in the AS-AH group (p<0.05).
  
  
  CONCLUSIONS
  The above results suggest that AS and AH in vitrification of expanded blastocysts lead to the more efficient formation of hatched blastocysts in mice.
authors.affiliation: Department of Obstetrics and Gynecology, Chungnam National University Hospital, Daejeon, Korea.
authors.forename: Hye Jin
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Department of Obstetrics and Gynecology, Chungnam National University Hospital, Daejeon, Korea.
authors.forename: Ki Hwan
authors.initials: KH
authors.lastname: Lee
authors.affiliation: Fertility Clinic, Mirae Ladies Hospital, Daejeon, Korea.
authors.forename: Sung Baek
authors.initials: SB
authors.lastname: Park
authors.affiliation: Fertility Clinic, Mirae Ladies Hospital, Daejeon, Korea.
authors.forename: Young Bae
authors.initials: YB
authors.lastname: Choi
authors.affiliation: Department of Obstetrics and Gynecology, Chungnam National University Hospital, Daejeon, Korea.
authors.forename: Jung Bo
authors.initials: JB
authors.lastname: Yang
keywords: Artificial shrinkage; Assisted hatching; Mouse blastocyst; Vitrification