Concentration of free vascular endothelial growth factor and its soluble receptor, sFlt-1 in the maternal and fetal circulations of normal term pregnancies at high and low altitudes.

OBJECTIVE: Vascular endothelial growth factor (VEGF) is regulated by hypoxia that is essential for placental development. It is antagonized by a soluble form of its receptor (sFlt-1). The purpose of this study was to measure these factors in the maternal and the cord bloods, at low and high altitude. METHODS: Samples were collected from full term births normal pregnant women. Free (unbound) VEGF and sFlt-1 levels were measured in plasma samples from cord and maternal blood for each subject by enzyme-linked immunosorbent assay (ELISA) using commercially available kits from R&D systems, UK (Cat # DVE00 and Cat # SVR100B, respectively). RESULTS: At high altitude, the average maternal free VEGF in pg/ml was significantly (p < 0.001) lower than that of the cord level (71.30 ± 282.14 and 431.35 ± 424.31, respectively). On the other hand, the average maternal sFlt-1 was significantly (p < 0.001) higher than that of the cord level (8205.41 ± 6244.72 and 1811.74 + 3469.30, respectively). At low altitude, the average maternal free VEGF was significantly lower than that of the cord level (0.47 ± 0.89 and 483.44 ± 457.31, respectively, p < 0.001). On the other hand, the average maternal sFlt-1 was significantly higher than that of the cord level (9267.82 ± 6345.68 and 958.66 ± 1359.92, respectively, p < 0.001). There were no significant differences by altitude. CONCLUSION: Secretion of sFlt-1 appears to be polarized, in that concentrations are higher in the maternal compartment than on the fetal side at both high and low altitudes. This may be a normal physiological phenomenon to permit angiogenesis in the placenta and fetus while protecting the mother. Chronic exposure to hypobaric hypoxia at high altitude does not affect these distributions.

Concentrations of free vascular endothelial growth factor in the maternal and foetal circulations during pregnancy: a cross-sectional study.

OBJECTIVE: To investigate the concentrations of free plasma vascular endothelial growth factor (VEGF) in the maternal and foetal circulations of normal term pregnancies. METHODS: Free plasma VEGF was measured from plasma of umbilical cord and maternal blood by ELISA for each of 20 normal pregnancies delivering at term at an altitude of 3100 m. Spearman's correlation coefficient was used to test for correlation between values and clinical maternal and neonatal data. Student's 't' test was used to test for differences between samples from male and female neonates. RESULTS: Free plasma VEGF was undetectable from maternal samples, but it was detectable in the cord blood (mean, 560.3775 pg/ml, median, 145.84 pg/ml, range, 22.56-2653.5). No differences were found between neonates sex, and no correlation was found with clinical maternal and neonatal data. CONCLUSION: Circulating VEGF is usually bound to the soluble form of its receptor 1 (sFlt-1). High levels of sFlt-1 are secreted by the syncytiotrophoblast during pregnancy, and so free plasma VEGF is undetectable in the maternal circulation. In contrast, our findings are the first to show free plasma VEGF in the umbilical circulation. We speculate that this free VEGF may promote angiogenesis in the foetus and placenta. Our data imply that sFlt-1 is not present in the cord blood, and that secretion by the syncytiotrophoblast is polarised to its apical surface. Further investigations are required to test this hypothesis.