title: Effects of oxygen tension and IGF-I on HIF-1α protein expression in mouse blastocysts.
abstract: OBJECTIVE
  Hypoxia inducible factors (HIFs) are key regulators of oxygen homeostasis in response to reduced oxygenation in somatic cells. In addition, HIF-1α protein can be also induced by insulin-like growth factor I (IGF-I) treatment in various cell lines under normoxic condition. However, the expression and function of HIF-1α in embryogenesis are still unclear. Therefore, the objectives of this study were to examine the expression of HIF-1α in mouse blastocysts cultured under hypoxic and normoxic conditions, and to determine whether oxygen tension and IGF-I influence embryonic development through stimulation of HIF-1α expression.
  
  
  METHODS
  Mouse embryos were cultured from the 1-cell to blastocyst stage under 5 % or 20 % O(2) in both the absence and presence of IGF-I.
  
  
  RESULTS
  The embryonic development rates to the blastocyst stage were not affected by oxygen tension or IGF-I treatment. HIF-1α protein was localized to the cytoplasm of blastocysts, and its levels were independent of oxygen concentration or IGF-I treatment. Blastocysts cultured under 5 % O(2) exhibited significantly higher total cell numbers (83.4 ± 18.1) and lower apoptotic index (3.7 ± 1.5) than those cultured under 20 % O(2) (67.4 ± 15.6) (6.9 ± 3.5) (P<0.05). IGF-I reduced the apoptotic index in both oxygen conditions, but a significant decrease was detected in the 20 % O(2) group.
  
  
  CONCLUSIONS
  HIF-1α may not be a major mediator that responds to change in oxygen tension within blastocysts, inconsistent with that of somatic cells. Supplementation of culture media with IGF-I has been shown to promote embryo development by an anti-apoptotic effect, instead of increasing HIF-1α protein expression.
authors.affiliation: Korea University, Anam-dong, Seongbuk-gu, Seoul, 136-713, South Korea. jeong7@mariababy.com
authors.forename: Jeong
authors.initials: J
authors.lastname: Yoon
authors.forename: Kyoung-Mi
authors.initials: KM
authors.lastname: Juhn
authors.forename: Jin-Kyung
authors.initials: JK
authors.lastname: Ko
authors.forename: San-Hyun
authors.initials: SH
authors.lastname: Yoon
authors.forename: Yong
authors.initials: Y
authors.lastname: Ko
authors.forename: Chul-Young
authors.initials: CY
authors.lastname: Lee
authors.forename: Jin-Ho
authors.initials: JH
authors.lastname: Lim
mesh_terms: D000818:Animals; D017209:Apoptosis; D001755:Blastocyst / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002452:Cell Count; D015687:Cell Hypoxia; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D006063:Chorionic Gonadotropin / Q000008:administration & dosage; D003470:Culture Media / Q000378:metabolism; D053938:DNA Fragmentation; D046149:Embryo Culture Techniques; D047108:Embryonic Development / Q000187:drug effects; D005260:Female; D005455:Fluorescent Antibody Technique; D018507:Gene Expression Regulation, Developmental; D006367:HeLa Cells; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008297:Male; D051379:Mice; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism*; D011247:Pregnancy
chemical_list: D006063:Chorionic Gonadotropin; D003470:Culture Media; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007334:Insulin-Like Growth Factor I; D010100:Oxygen