title: Characterization of invasive trophoblasts generated from human embryonic stem cells.
abstract: BACKGROUND
  Abnormal human embryo implantation leads to poor foetal development and miscarriage, or pre-eclampsia. Ethical and practical considerations concerning implantation limit its investigation, and it is often difficult to extrapolate findings in laboratory animals when implantation processes show diverse species differences. Therefore, it is important to develop new in vitro models to study the earliest events of human implantation. The aim of this study was to derive trophoblast cell lines from human embryonic stem cells (hESCs) by a robust protocol and co-culture of these cells with an established endometrial cell culture system to validate a model of trophoblast invasion at implantation.
  
  
  METHODS
  Derivation of trophoblast cell lines from hESC lines was established by spontaneous and induced differentiation of embryoid bodies and by initial measurement of hCGβ secretion by enzyme-linked immunosorbent assay and their phenotype investigated using gene- and protein-expression markers. Vesicles formed from an aggregating trophoblast were co-cultured with decidualized human endometrial stromal cells in hypoxic (2% oxygen) and normoxic (20% oxygen) environments.
  
  
  RESULTS
  Derived villous cytotrophoblast cell (CTB) lines further differentiated to invasive, extra-villous CTBs. Eventually, cells lost their proliferative capacity, with some lines acquiring karyotypic changes, such as a gain in the X chromosome. Cell-invasion assays confirmed that the extra-villous CTBs were invasive and erosion of the endometrial stromal layer occurred, particularly under hypoxic conditions in vitro.
  
  
  CONCLUSIONS
  Trophoblast cell lines derived from hESCs differentiate and adapt in vitro and can be used as a model to study the mechanisms of early trophoblast invasion.
authors.affiliation: Centre for Stem Cell Biology, University of Sheffield, Sheffield S10 2TN, UK. ramya.udayashankar@ge.com
authors.forename: R
authors.initials: R
authors.lastname: Udayashankar
authors.forename: D
authors.initials: D
authors.lastname: Baker
authors.forename: E
authors.initials: E
authors.lastname: Tuckerman
authors.forename: S
authors.initials: S
authors.lastname: Laird
authors.forename: T C
authors.initials: TC
authors.lastname: Li
authors.forename: H D
authors.initials: HD
authors.lastname: Moore
mesh_terms: D002454:Cell Differentiation; D002460:Cell Line; D002869:Chromosome Aberrations; D018920:Coculture Techniques; D010064:Embryo Implantation / Q000502:physiology*; D053595:Embryonic Stem Cells / Q000166:cytology*; D005260:Female; D015870:Gene Expression; D006801:Humans; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis; D008954:Models, Biological; D011247:Pregnancy; D014327:Trophoblasts / Q000166:cytology / Q000502:physiology*
chemical_list: D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9