title: Extravillous trophoblast and decidual natural killer cells: a remodelling partnership.
abstract: BACKGROUND
  During pregnancy, maternal uterine spiral arteries (SAs) are remodelled from minimal-flow, high-resistance vessels into larger diameter vessels with low resistance and high flow. Fetal extravillous trophoblasts (EVT) have important roles in this process. Decidual natural killer cells (dNK cells) are the major maternal immune component of the decidua and accumulate around SAs before trophoblast invasion. A role for dNK cells in vessel remodelling is beginning to be elucidated. This review examines the overlapping and dissimilar mechanisms used by EVT and dNK cells in this process and how this may mirror another example of tissue remodelling, namely cancer development.
  
  
  METHODS
  The published literature was searched using Pubmed focusing on EVT, dNK cells and SA remodelling. Additional papers discussing cancer development are also included.
  
  
  RESULTS
  Similarities exist between actions carried out by dNK cells and EVT. Both interact with vascular cells lining the SA, as well as with each other, to promote transformation of the SA. EVT differentiation has previously been likened to the epithelial-mesenchymal transition in cancer cells, and we discuss how dNK-EVT interactions at the maternal-fetal interface can also be compared with the roles of immune cells in cancer.
  
  
  CONCLUSIONS
  The combined role that dNK cells and EVT play in SA remodelling suggests that these interactions could be described as a partnership. The investigation of pregnancy as a multicellular system involving both fetal and maternal components, as well as comparisons to similar examples of tissue remodelling, will further identify the key mechanisms in SA remodelling that are required for a successful pregnancy.
authors.affiliation: Reproductive and Cardiovascular Disease Research Group, Division of Biomedical Sciences, St George's University of London, London, UK. awallace@sgul.ac.uk
authors.forename: Alison E
authors.initials: AE
authors.lastname: Wallace
authors.forename: Rupsha
authors.initials: R
authors.lastname: Fraser
authors.forename: Judith E
authors.initials: JE
authors.lastname: Cartwright
mesh_terms: D002454:Cell Differentiation; D003656:Decidua / Q000098:blood supply* / Q000166:cytology*; D058750:Epithelial-Mesenchymal Transition; D005260:Female; D006801:Humans; D007694:Killer Cells, Natural / Q000502:physiology*; D011247:Pregnancy; D014327:Trophoblasts / Q000502:physiology*; D055988:Uterine Artery / Q000502:physiology*