title: Relationship between reactive oxygen species and autophagy in dormant mouse blastocysts during delayed implantation.
abstract: OBJECTIVE
  Under estrogen deficiency, blastocysts cannot initiate implantation and enter dormancy. Dormant blastocysts live longer in utero than normal blastocysts, and autophagy has been suggested as a mechanism underlying the sustained survival of dormant blastocysts during delayed implantation. Autophagy is a cellular degradation pathway and a central component of the integrated stress response. Reactive oxygen species (ROS) are produced within cells during normal metabolism, but their levels increase dramatically under stressful conditions. We investigated whether heightened autophagy in dormant blastocysts is associated with the increased oxidative stress under the unfavorable condition of delayed implantation.
  
  
  METHODS
  To visualize ROS production, day 8 (short-term dormancy) and day 20 (long-term dormancy) dormant blastocysts were loaded with 1-µM 5-(and-6)-chloromethyl-2', 7'-dichlorodihydrofluorescein diacetate, acetyl ester (CM-H2DCFDA). To block autophagic activation, 3-methyladenine (3-MA) and wortmannin were used in vivo and in vitro, respectively.
  
  
  RESULTS
  We observed that ROS production was not significantly affected by the status of dormancy; in other words, both dormant and activated blastocysts showed high levels of ROS. However, ROS production was higher in the dormant blastocysts of the long-term dormancy group than in those of the short-term group. The addition of wortmannin to dormant blastocysts in vitro and 3-MA injection in vivo significantly increased ROS production in the short-term dormant blastocysts. In the long-term dormant blastocysts, ROS levels were not significantly affected by the treatment of the autophagy inhibitor.
  
  
  CONCLUSIONS
  During delayed implantation, heightened autophagy in dormant blastocysts may be operative as a potential mechanism to reduce oxidative stress. Further, ROS may be one of the potential causes of compromised developmental competence of long-term dormant blastocysts after implantation.
authors.affiliation: Department of Biomedical Science and Technology, Institute of Biomedical Science and Technology, Konkuk University, Seoul, Korea.
authors.forename: Hyejin
authors.initials: H
authors.lastname: Shin
authors.affiliation: Department of Biomedical Science and Technology, Institute of Biomedical Science and Technology, Konkuk University, Seoul, Korea.
authors.forename: Soyoung
authors.initials: S
authors.lastname: Choi
authors.affiliation: Department of Biomedical Science and Technology, Institute of Biomedical Science and Technology, Konkuk University, Seoul, Korea. ; Department of Veterinary Medicine, Institute of Biomedical Science and Technology, Konkuk University, Seoul, Korea.
authors.forename: Hyunjung Jade
authors.initials: HJ
authors.lastname: Lim
keywords: Autophagy; Delayed implantation; Dormant blastocyst; Reactive oxygen species