Objective: To measure the mRNA levels of vascular endothelial growth factor and its receptor in the placenta following delivery after uncomplicated pregnancy and after pregnancies complicated by pre-eclampsia.
Setting: Rosie Maternity Hospital, Cambridge.
Material: Placental biopsies were obtained following delivery by caesarean section in 23 cases of pregnancy presenting at a range of gestational ages with pre-eclampsia. These were compared with biopsies from 20 appropriately matched women with uncomplicated pregnancies.
Main outcome measure: mRNA levels of vascular endothelial growth factor (VEGF) and its receptor the fins-like tyrosine kinase (flt), were quantified in total RNA isolated from placental biopsies using the RNAse protection assay. The amount of RNA was compared with that of the housekeeping gene glyceraldehyde 3-phosphate dehydrogenase (GAPDH), used as a standard. Results were expressed as arbitrary optical density units of VEGF/GAPDH and flt/GAPDH.
Results: In both control and pre-eclamptic women regression analysis showed that the level of mRNA encoding VEGF declined significantly with gestational age (P < 0.0001). However, levels of VEGF mRNA were significantly lower in the pre-eclamptic women compared with the control women (P < 0.023).
Conclusions: This study provides evidence of an abnormality of growth factor expression in the placenta during pregnancies complicated by pre-eclampsia. Such placentae exhibit deficient growth and differentiation of terminal villi and reduced fetal capillary branching and reduced levels of VEGF could well account for these morphometric changes. This finding provides a molecular explanation for this abnormal placental development and points to VEGF as a factor in the aetiology of pre-eclampsia and its complications.