title: Activin A, B, and AB increase human trophoblast cell invasion by up-regulating N-cadherin.
abstract: BACKGROUND
  Inhibin β-subunits and activin receptors are expressed by human trophoblast cells. Although activin A has been shown to enhance human trophoblast cell invasion, whether two additional activin isoforms, activin B and AB, exert similar effects remains unknown. Moreover, whether the expression of mesenchymal adhesion molecule neural cadherin (N-cadherin) is essential for this proinvasive effect of activin has yet to be determined.
  
  
  OBJECTIVE
  To examine the effects of all three activin isoforms on human trophoblast cell invasion and the involvement of N-cadherin.
  
  
  METHODS
  HTR8/SVneo immortalized extravillous cytotrophoblast cells and primary cultures of human extravillous cytotrophoblast cells were used as study models. Small interfering RNA-mediated knockdown approaches were used to investigate the molecular determinants of activin-mediated functions.
  
  
  METHODS
  An academic research center.
  
  
  METHODS
  Reverse transcription-quantitative real-time PCR and Western blot analysis were used to examine mRNA and protein levels, respectively. Cell invasiveness was assessed by Matrigel-coated transwell assays.
  
  
  RESULTS
  All three activin isoforms produced comparable increases in HTR8/SVneo cell invasion as well as N-cadherin expression. In addition, the up-regulatory effect of activin isoforms on N-cadherin was confirmed in primary cultures of human trophoblast cells. Interestingly, small interfering RNA-mediated down-regulation of N-cadherin attenuated basal and activin-induced invasion of both HTR8/SVneo and primary trophoblast cells. All three activin isoforms induced equivalent phosphorylation of SMAD2 and SMAD3. Importantly, activin-stimulated cell invasion, up-regulation of N-cadherin, as well as activation of SMAD2/SMAD3 were abolished by the TGF-β type I receptor inhibitor SB431542 in HTR8/SVneo cells. Furthermore, knockdown of SMAD2/3 or common SMAD4 abolished the stimulatory effects of all three activin isoforms on N-cadherin expression.
  
  
  CONCLUSIONS
  Activin A, B, and AB produce comparable increases in human trophoblast cell invasion by up-regulating N-cadherin expression in a SMAD2/3-SMAD4-dependent manner.
authors.affiliation: Department of Obstetrics and Gynaecology, Child and Family Research Institute, University of British Columbia, Vancouver, BC V5Z 4H4, Canada.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Christian
authors.initials: C
authors.lastname: Klausen
authors.forename: Jung-Chien
authors.initials: JC
authors.lastname: Cheng
authors.forename: Hua
authors.initials: H
authors.lastname: Zhu
authors.forename: Peter C K
authors.initials: PC
authors.lastname: Leung
mesh_terms: D028341:Activins / Q000235:genetics / Q000378:metabolism*; D015820:Cadherins / Q000378:metabolism*; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology*; D006801:Humans; D028322:Inhibin-beta Subunits / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D034741:RNA, Small Interfering; D051899:Smad2 Protein / Q000235:genetics / Q000378:metabolism; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism; D014327:Trophoblasts / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D015820:Cadherins; C422402:INHBB protein, human; D034741:RNA, Small Interfering; D051899:Smad2 Protein; D051900:Smad3 Protein; C422405:activin A; C044147:activin B; D028341:Activins; D028322:Inhibin-beta Subunits