title: Fetal esophageal ligation induces expression of vascular endothelial growth factor messenger ribonucleic acid in fetal membranes.
abstract: OBJECTIVE
  Obstruction of the fetal esophagus does not always produce the expected polyhydramnios. This is because of increased intramembranous absorption of amniotic fluid into the fetal circulation. A possible mediator for this increased absorption is vascular endothelial growth factor (VEGF). The present objective was to explore whether VEGF gene expression and action would be induced in fetal membranes and placentas of ovine fetuses after esophageal ligation.
  
  
  METHODS
  Five late-gestation fetal sheep underwent esophageal ligation and 5 served as control animals. On postoperative day 9, amnion, chorion, and placenta were collected for cellular localization and quantitation of VEGF messenger ribonucleic acid by in situ hybridization and Northern blot analysis. Reverse-transcription polymerase chain reaction was used to identify the VEGF molecular forms. Immunostaining with Ki-67 antibody was used to determine the proliferation of vascular endothelium in the fetal membranes and placentas.
  
  
  RESULTS
  VEGF messenger ribonucleic acid was localized in amniotic epithelium, chorionic cytotrophoblast, and cytotrophoblast of the placenta. VEGF164 was the major transcript expressed in these tissues. The abundance of VEGF messenger ribonucleic acid in the amnion and chorion, but not in the placenta, was significantly increased in the ligated fetuses in comparison with the control fetuses. The proliferation of the intramembranous blood vessel endothelium was greater in the ligated fetuses than in the control fetuses.
  
  
  CONCLUSIONS
  The levels of VEGF messenger ribonucleic acid and the proliferation of vascular endothelium in the amnion and chorion increased after fetal esophageal ligation. This provides a possible mechanism for the enhanced intramembranous absorption of amniotic fluid through increased vascularity and permeability of the fetal membranes, thus ameliorating the development of polyhydramnios. We speculate that the signal(s) that mediate the increase in VEGF expression is present in either the fetal urine or the fetal lung secretions, or both.
authors.affiliation: Division of Perinatal Medicine, Department of Reproductive Medicine, University of California at San Diego, 92093-0802, USA.
authors.forename: L C
authors.initials: LC
authors.lastname: Matsumoto
authors.forename: L
authors.initials: L
authors.lastname: Bogic
authors.forename: R A
authors.initials: RA
authors.lastname: Brace
authors.forename: C Y
authors.initials: CY
authors.lastname: Cheung
mesh_terms: D000650:Amnion / Q000737:chemistry; D000818:Animals; D015152:Blotting, Northern; D002455:Cell Division; D002823:Chorion / Q000737:chemistry; D016228:Endothelial Growth Factors / Q000235:genetics*; D004730:Endothelium, Vascular / Q000166:cytology; D004848:Epithelium / Q000737:chemistry; D004947:Esophagus / Q000196:embryology* / Q000503:physiopathology / Q000601:surgery; D005321:Extraembryonic Membranes / Q000737:chemistry* / Q000166:cytology; D005260:Female; D015870:Gene Expression; D005865:Gestational Age; D017403:In Situ Hybridization; D019394:Ki-67 Antigen / Q000032:analysis; D008026:Ligation; D008222:Lymphokines / Q000235:genetics*; D023421:Models, Animal; D006831:Polyhydramnios / Q000209:etiology; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014327:Trophoblasts / Q000737:chemistry; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
chemical_list: D016228:Endothelial Growth Factors; D019394:Ki-67 Antigen; D008222:Lymphokines; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors