title: Villous explant culture using early gestation tissue from ongoing pregnancies with known normal outcomes: the effect of oxygen on trophoblast outgrowth and migration.
abstract: BACKGROUND
  Early placental and embryo development occur in a physiologically low oxygen environment, with a rise in oxygen tension within the placenta towards the end of the first trimester. Oxygen is implicated in the regulation of trophoblast differentiation and invasion. This study examined the effects of oxygen tension on extravillous trophoblast outgrowth and migration from normal pregnancies free of significant pathology.
  
  
  METHODS
  Early gestation villous tissue (11-14 weeks gestation), obtained by chorionic villus sampling, was cultured in 3 or 20% oxygen. Maternal and fetal outcomes were ascertained for all samples. The frequency and amount of trophoblast outgrowth and migration from villi were measured for up to 192 h.
  
  
  RESULTS
  Significantly fewer explants produced outgrowths in 3% compared with 20% oxygen. The number of sites of trophoblast outgrowth and the extent of migration were also significantly less in 3% compared with 20% oxygen. In vitro hypoxia/reoxygenation further reduced trophoblast growth compared with 3% oxygen alone. HLA-G expression in extravillous trophoblasts was not affected by oxygen tension, with HLA-G positive extravillous trophoblasts being universally Ki67 negative.
  
  
  CONCLUSIONS
  Human placental villi and extravillous trophoblasts in the late first trimester of pregnancy are sensitive to oxygen tension, with low oxygen inhibiting extravillous trophoblast outgrowth and migration.
authors.affiliation: Perinatal Research, Kolling Institute of Medical Research, The University of Sydney, Northern Clinical School, St Leonards, NSW 2065, Australia. seanseeho@med.usyd.edu.au
authors.forename: S K M
authors.initials: SK
authors.lastname: Seeho
authors.forename: J H
authors.initials: JH
authors.lastname: Park
authors.forename: J
authors.initials: J
authors.lastname: Rowe
authors.forename: J M
authors.initials: JM
authors.lastname: Morris
authors.forename: E D M
authors.initials: ED
authors.lastname: Gallery
mesh_terms: D002465:Cell Movement / Q000187:drug effects; D002824:Chorionic Villi / Q000254:growth & development*; D015193:Chorionic Villi Sampling; D005260:Female; D006680:HLA Antigens / Q000096:biosynthesis; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D019394:Ki-67 Antigen / Q000096:biosynthesis; D010100:Oxygen / Q000008:administration & dosage / Q000494:pharmacology*; D011247:Pregnancy; D046509:Tissue Culture Techniques; D014327:Trophoblasts / Q000187:drug effects* / Q000502:physiology*
chemical_list: D006680:HLA Antigens; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I; D019394:Ki-67 Antigen; D010100:Oxygen