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

Abstract

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.

Keywords::

• Altitude
• cord blood
• maternal blood
• VEGF and sFlt-1

Acknowledgement

K.Z.M. conceived of the study, its design and coordination and draft the manuscript and was ultimately responsible for this work., K.Z.M., G.B., A.M., M.A., A.A. have made substantial contributions to analysis and interpretation of data, R.A., S.A., A.G.A., A.M.B. collected samples, results and carried out the laboratory procedures, A.A. Mahfouz carried out the statistical analysis of the data and G.B. have given final approval of the version to be published. All authors read and approved the final manuscript.

Declaration of Interest: The authors report no conflict of interest.