title: The role of chorionic cytotrophoblasts in the smooth chorion fusion with parietal decidua.
abstract: OBJECTIVE
  Human placenta and chorion are rapidly growing transient embryonic organs built from diverse cell populations that are of either, ectodermal [placenta and chorion specific trophoblast (TB) cells], or mesodermal origin [villous core and chorionic mesenchyme]. The development of placenta and chorion is synchronized from the earliest phase of implantation. Little is known about the formative stages of the human chorion, in particular the steps between the formation of a smooth chorion and its fusion with the parietal decidua.
  
  
  METHODS
  We examined the available histological material using immunohistochemistry, and further analyzed in vitro the characteristics of the recently established and reported human self-renewing trophoblast progenitor cells (TBPC) derived from chorionic mesoderm.
  
  
  RESULTS
  Here, we provided evidence that the mechanism by which smooth chorion fuses with parietal decidua is the invasion of smooth chorionic cytotrophoblasts (schCTBs) into the uterine wall opposite to the implantation side. This process, which partially replicates some of the mechanisms of the blastocyst implantation, leads to the formation of a new zone of contacts between fetal and maternal cells.
  
  
  CONCLUSIONS
  We propose the schCTBs invasion of the parietal decidua as a mechanism of 'fusion' of the membranes, and that schCTBs in vivo contribute to the pool of the invasive schCTB.
authors.affiliation: The Ely and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, USA; Center for Reproductive Sciences, USA; Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, San Francisco, CA, USA. Electronic address: genbacev@comcast.net.
authors.forename: O
authors.initials: O
authors.lastname: Genbačev
authors.affiliation: Laboratory for Biology of Reproduction, Institute INEP, University of Belgrade, Belgrade, Serbia.
authors.forename: L
authors.initials: L
authors.lastname: Vićovac
authors.affiliation: The Ely and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, USA; Center for Reproductive Sciences, USA; Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, San Francisco, CA, USA; Department of Biology, San Francisco State University, San Francisco, CA, USA.
authors.forename: N
authors.initials: N
authors.lastname: Larocque
mesh_terms: D001755:Blastocyst / Q000502:physiology; D002823:Chorion / Q000166:cytology* / Q000502:physiology; D003656:Decidua / Q000166:cytology* / Q000502:physiology; D010064:Embryo Implantation; D047108:Embryonic Development; D005260:Female; D005865:Gestational Age; D006801:Humans; D007150:Immunohistochemistry; D010920:Placenta / Q000166:cytology; D011247:Pregnancy; D013234:Stem Cells; D014327:Trophoblasts / Q000166:cytology* / Q000502:physiology; D014599:Uterus / Q000166:cytology
keywords: Chorionic cytotrophoblast; Human pregnancy; Invasive CTBs; Smooth chorion; Trophoblast progenitor cells