Vascular endothelial growth factor gene expression in ovine placenta and fetal membranes

OBJECTIVE: The purpose of this study was to explore the gene expression of vascular endothelial growth factor (VEGF) in placental cotyledon, chorion, and amnion of the ovine fetus. STUDY DESIGN: Time-dated pregnant sheep with singleton or twin fetuses at a gestational age ranging from 100 to 140 days were used for the study. Placental cotyledonary, chorionic, and amniotic tissues were collected and processed for messenger ribonucleic acid analysis by Northern blotting and reverse transcription-polymerase chain reaction. RESULTS: By use of a phosphorus 32-labeled human VEGF complementary deoxyribonucleic acid probe, a prominent VEGF messenger ribonucleic acid transcript of 3.7 kb was detected in the cotyledon, chorion, and amnion. A minor band of 1.7 kb was also found but only in the cotyledon and chorion. The abundance of mesenger ribonucleic acid encoding VEGF was highest (p < 0.001) in the cotyledon and lowest in the amnion. In these tissues polymerase chain reaction-amplified products corresonding to VEGF₁₂₁, VEGF₁₆₅, VEGF₁₈₉, and VEGF₂₀₆ were identified by ethidium bromide. In addition, a polymerase chain reaction fragment corresponding to VEGF₁₄₅ was observed. These fragments produced specific hybridization signals with the human VEGF radioactive probe where the intensity of the signal was strongest for VEGF₁₆₅ and weakest for VEGF₁₈₉. CONCLUSIONS: VEGF gene expression was detected in the cotyledon, chorion, and amnion of the near-term ovine fetus. These findings suggest that vascular endothelial growth factor may play a role in the induction of angiogenesis and promotion of permeability in the microvessels that perfuse the placental and fetal membranes.