title: Human trophectoderm cells are not yet committed.
abstract: OBJECTIVE
  Are human trophectoderm (TE) cells committed or still able to develop into inner cell mass (ICM) cells?
  
  
  CONCLUSIONS
  Human full blastocyst TE cells still have the capacity to develop into ICM cells expressing the pluripotency marker NANOG, thus they are not yet committed.
  
  
  BACKGROUND
  Human Day 5 full blastocyst TE cells express the pluripotency markers POU5F1, SOX2 and SALL4 as well as the TE markers HLA-G and KRT18 but not yet CDX2, therefore their developmental direction may not yet be definite.
  
  
  METHODS
  The potency of human blastocyst TE cells was investigated by determining their in vitro capacity to develop into a blastocyst with ICM cells expressing NANOG; TE cells were isolated either by aspiration under visual control or after labeling with fluorescent 594-wheat germ agglutinin. Further on, aspirated TE cells were also labeled with fluorescent PKH67 and repositioned in the center of the original embryo.
  
  
  METHODS
  Human preimplantation embryos were used for research after obtaining informed consent from IVF patients. The experiments were approved by the Local Ethical Committee and the 'Belgian Federal Committee on medical and scientific research on embryos in vitro'. Outer cells were isolated and reaggregated by micromanipulation. Reconstituted embryos were analyzed by immunocytochemistry.
  
  
  RESULTS
  Isolated and reaggregated TE cells from full human blastocysts are able to develop into blastocysts with ICM cells expressing the pluripotency marker NANOG. Moreover, the majority of the isolated TE cells which were repositioned in the center of the embryo do not sort back to their original position but integrate within the ICM and start to express NANOG.
  
  
  CONCLUSIONS
  Owing to legal and ethical restrictions, manipulated human embryos cannot be transferred into the uterus to determine their totipotent capacity. The definitive demonstration that embryos reconstructed with TE cells are a source of pluripotent cells is to obtain human embryonic stem cell 'like' line(s), which will allow full characterization of the cells.
  
  
  CONCLUSIONS
  Our finding has important implications in reproductive medicine and stem cell biology because TE cells have a greater developmental potential than assumed previously.
  
  
  BACKGROUND
  Scientific Research Foundation-Flanders (FWO-Vlaanderen) and Research Council (OZR) of the Vrije Universiteit Brussel. None of the authors declared a conflict of interest.
authors.affiliation: Department of Reproduction and Genetics, Vrije Universiteit Brussel, Belgium.
authors.forename: Caroline
authors.initials: C
authors.lastname: De Paepe
authors.forename: Greet
authors.initials: G
authors.lastname: Cauffman
authors.forename: An
authors.initials: A
authors.lastname: Verloes
authors.forename: Johan
authors.initials: J
authors.lastname: Sterckx
authors.forename: Paul
authors.initials: P
authors.lastname: Devroey
authors.forename: Herman
authors.initials: H
authors.lastname: Tournaye
authors.forename: Inge
authors.initials: I
authors.lastname: Liebaers
authors.forename: Hilde
authors.initials: H
authors.lastname: Van de Velde
mesh_terms: D001755:Blastocyst / Q000166:cytology* / Q000378:metabolism; D053624:Blastocyst Inner Cell Mass / Q000166:cytology / Q000378:metabolism; D002469:Cell Separation; D004477:Ectogenesis; D046149:Embryo Culture Techniques; D053595:Embryonic Stem Cells / Q000166:cytology* / Q000378:metabolism; D005456:Fluorescent Dyes / Q000737:chemistry; D018398:Homeodomain Proteins / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008846:Micromanipulation; D000071317:Nanog Homeobox Protein; D039904:Pluripotent Stem Cells / Q000166:cytology* / Q000378:metabolism; D055746:Stage-Specific Embryonic Antigens / Q000378:metabolism; D014327:Trophoblasts / Q000166:cytology / Q000378:metabolism
chemical_list: D005456:Fluorescent Dyes; D018398:Homeodomain Proteins; C486780:NANOG protein, human; D000071317:Nanog Homeobox Protein; D055746:Stage-Specific Embryonic Antigens