title: An in-vitro model for stromal invasion during implantation of the human blastocyst.
abstract: BACKGROUND
  Implantation failure is likely to be a major cause of infertility. Studies in mice have identified a number of molecules that are involved in implantation, but the mechanisms of implantation in the human remain unclear, largely due to the lack of models for implantation in the human that provide functional information.
  
  
  METHODS
  Human hatched blastocysts were co-cultured with human endometrial stromal cell monolayers. Time-lapse photography of implanting blastocysts, immunostaining for cytokeratin and actin, and measurement of hCG secreted into the culture supernatants were performed.
  
  
  RESULTS
  Blastocysts attached to and implanted into the stromal cell layer. Trophoblast outgrowth onto, and invasion into, the stromal cell layer occurred largely at two opposite poles, the orientation of which was aligned to that of the stromal cell fibroblasts. High-resolution image analysis demonstrated that the trophoblast completely penetrated the stromal cell layer. Immunostaining of whole-mounts of implantation sites revealed distinctive actin and cytokeratin-positive anchoring structures adjacent to the basal surface of the trophoblast. Blastocysts implanting into stromal cells secreted higher levels of hCG compared with those cultured on plastic.
  
  
  CONCLUSIONS
  A robust model for the study of mechanisms of implantation of the human embryo into the endometrial stroma has been established.
authors.affiliation: Nuffield Department of Obstetrics and Gynaecology, University of Oxford, Women's Centre, John Radcliffe Hospital, Oxford, UK.
authors.forename: Janet
authors.initials: J
authors.lastname: Carver
authors.forename: Karen
authors.initials: K
authors.lastname: Martin
authors.forename: Isabella
authors.initials: I
authors.lastname: Spyropoulou
authors.forename: David
authors.initials: D
authors.lastname: Barlow
authors.forename: Ian
authors.initials: I
authors.lastname: Sargent
authors.forename: Helen
authors.initials: H
authors.lastname: Mardon
mesh_terms: D000199:Actins / Q000378:metabolism; D000328:Adult; D002448:Cell Adhesion; D016764:Cell Polarity; D002478:Cells, Cultured; D006063:Chorionic Gonadotropin / Q000378:metabolism; D018920:Coculture Techniques; D010064:Embryo Implantation / Q000502:physiology*; D004717:Endometrium / Q000166:cytology / Q000502:physiology*; D005109:Extracellular Matrix / Q000502:physiology; D005260:Female; D006801:Humans; D007633:Keratins / Q000378:metabolism; D008875:Middle Aged; D017154:Stromal Cells / Q000502:physiology; D014327:Trophoblasts / Q000502:physiology
chemical_list: D000199:Actins; D006063:Chorionic Gonadotropin; D007633:Keratins