title: Nerve growth factor induces vascular endothelial growth factor expression in granulosa cells via a trkA receptor/mitogen-activated protein kinase-extracellularly regulated kinase 2-dependent pathway.
abstract: BACKGROUND
  Acquisition of ovulatory competence by antral follicles requires development of an adequate vascular supply. Although it is well established that ovarian angiogenesis is cyclically regulated by vascular endothelial growth factor (VEGF), the factors controlling VEGF production by ovarian follicles remain largely unknown. Nerve growth factor (NGF) may be one of these factors, because NGF promotes angiogenesis and synthesis of angiogenic factors in other tissues and is produced by human granulosa cells (hGCs).
  
  
  OBJECTIVE
  The aim of the study was to determine whether NGF influences the production of VEGF by hGCs and to identify a potential signaling pathway underlying this effect.
  
  
  METHODS
  We conducted a prospective experimental study.
  
  
  METHODS
  hGCs were obtained from 41 women participating in the in vitro fertilization program of our institution.
  
  
  METHODS
  Changes in VEGF mRNA after exposure to NGF were evaluated in cultured hGCs by PCR and real-time PCR. The effect of NGF on VEGF secretion was determined by ELISA. The involvement of trkA, the high affinity NGF receptor, was examined by inhibiting the receptor's tyrosine kinase activity with K252a. The contribution of an ERK1/ERK2-mediated signaling pathway was identified by detecting NGF-dependent phosphorylation of these proteins and by blocking their activity with the inhibitor U0126.
  
  
  RESULTS
  NGF promotes VEGF production in cultured hGCs. Blockade of trkA receptor tyrosine kinase activity blocks this effect. NGF induces MAPK-ERK2 phosphorylation, and blockade of this signaling pathway prevents the NGF-induced increase in VEGF production.
  
  
  CONCLUSIONS
  NGF promotes ovarian angiogenesis by enhancing the synthesis and secretion of VEGF from hGCs via a trkA- and ERK2-dependent mechanism.
authors.affiliation: Laboratorio de Endocrinología y Biología de la Reproducción, Hospital Clínico Universidad de Chile, Santos Dumont 999 Independencia, Santiago, Chile.
authors.forename: Marcela
authors.initials: M
authors.lastname: Julio-Pieper
authors.forename: Patricia
authors.initials: P
authors.lastname: Lozada
authors.forename: Veronica
authors.initials: V
authors.lastname: Tapia
authors.forename: Margarita
authors.initials: M
authors.lastname: Vega
authors.forename: Cristián
authors.initials: C
authors.lastname: Miranda
authors.forename: David
authors.initials: D
authors.lastname: Vantman
authors.forename: Sergio R
authors.initials: SR
authors.lastname: Ojeda
authors.forename: Carmen
authors.initials: C
authors.lastname: Romero
mesh_terms: D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology*; D005260:Female; D006107:Granulosa Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology*; D020932:Nerve Growth Factor / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D020917:Receptor, trkA / Q000502:physiology*; D015398:Signal Transduction; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D020932:Nerve Growth Factor; D020917:Receptor, trkA; D048049:Extracellular Signal-Regulated MAP Kinases