title: IGFBP-4 and -5 are expressed in first-trimester villi and differentially regulate the migration of HTR-8/SVneo cells.
abstract: BACKGROUND
  Adverse gestational outcomes such as preeclampsia (PE) and intrauterine growth restriction (IUGR) are associated with placental insufficiency. Normal placental development relies on the insulin-like growth factors -I and -II (IGF-I and -II), in part to stimulate trophoblast proliferation and extravillous trophoblast (EVT) migration. The insulin-like growth factor binding proteins (IGFBPs) modulate the bioavailability of IGFs in various ways, including sequestration, potentiation, and/or increase in half-life. The roles of IGFBP-4 and -5 in the placenta are unknown, despite consistent associations between pregnancy complications and the levels of two IGFBP-4 and/or -5 proteases, pregnancy-associated plasma protein -A and -A2 (PAPP-A and PAPP-A2). The primary objective of this study was to elucidate the effects of IGFBP-4 and -5 on IGF-I and IGF-II in a model of EVT migration. A related objective was to determine the timing and location of IGFBP-4 and -5 expression in the placental villi.
  
  
  METHODS
  We used wound healing assays to examine the effects of IGFBP-4 and -5 on the migration of HTR-8/SVneo cells following 4 hours of serum starvation and 24 hours of treatment. Localization of IGFBP-4, -5 and PAPP-A2 was assessed by immunohistochemical staining of first trimester placental sections.
  
  
  RESULTS
  2 nM IGF-I and -II each increased HTR-8/SVneo cell migration with IGF-I increasing migration significantly more than IGF-II. IGFBP-4 and -5 showed different levels of inhibition against IGF-I. 20 nM IGFBP-4 completely blocked the effects of 2 nM IGF-I, while 20 nM IGFBP-5 significantly reduced the effects of 2 nM IGF-I, but not to control levels. Either 20 nM IGFBP-4 or 20 nM IGFBP-5 completely blocked the effects of 2 nM IGF-II. Immunohistochemistry revealed co-localization of IGFBP-4, IGFBP-5 and PAPP-A2 in the syncytiotrophoblast layer of first trimester placental villi as early as 5 weeks of gestational age.
  
  
  CONCLUSIONS
  IGFBP-4 and -5 show different levels of inhibition on the migration-stimulating effects of IGF-I and IGF-II, suggesting different roles for PAPP-A and PAPP-A2. Moreover, co-localization of the pappalysins and their substrates within placental villi suggests undescribed roles of these molecules in early placental development.
authors.forename: Erin J
authors.initials: EJ
authors.lastname: Crosley
authors.forename: Caroline E
authors.initials: CE
authors.lastname: Dunk
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Beristain
authors.affiliation: Biological Sciences, Simon Fraser University, V5A 1S6 Burnaby, Canada. julian_christians@sfu.ca.
authors.forename: Julian K
authors.initials: JK
authors.lastname: Christians
mesh_terms: D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005865:Gestational Age; D006801:Humans; D007150:Immunohistochemistry; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000096:biosynthesis* / Q000494:pharmacology; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000096:biosynthesis* / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011266:Pregnancy-Associated Plasma Protein-A / Q000096:biosynthesis; D014327:Trophoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
chemical_list: D018974:Insulin-Like Growth Factor Binding Protein 4; D018975:Insulin-Like Growth Factor Binding Protein 5; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; C430889:PAPPA2 protein, human; D011266:Pregnancy-Associated Plasma Protein-A