An EG-VEGF-dependent decrease in homeobox gene NKX3.1 contributes to cytotrophoblast dysfunction: a possible mechanism in human fetal growth restriction.

Idiopathic fetal growth restriction (FGR) is frequently associated with placental insufficiency. Previous reports have provided evidence that EG-VEGF (endocrine gland derived-vascular endothelial growth factor), a placental secreted protein, is expressed during the first trimester of pregnancy, controls both trophoblast proliferation and invasion, and its increased expression is associated with human FGR. In this study, we hypothesise that EG-VEGF-dependent change in placental homeobox gene expressions contribute to trophoblast dysfunction in idiopathic FGR. The changes in EG-VEGF-dependent homeobox gene expressions were determined using a Homeobox gene cDNA array on placental explants of 8-12 weeks' gestation after stimulation with EG-VEGF in vitro for 24 hours. The Homeobox gene array identified a >5-fold increase in HOXA9, HOXC8, HOXC10, HOXD1, HOXD8, HOXD9 and HOXD11, while NKX 3.1 showed a >2 fold-decrease in mRNA expression compared to untreated controls. Homeobox gene NKX3.1 was selected as a candidate because it is a downstream target of EG-VEGF and its expression and functional role are largely unknown in control and idiopathic FGR-affected placentae. Real-time PCR and immunoblotting showed a significant decrease in NKX3.1 mRNA and protein levels, respectively, in placentae from FGR compared to control pregnancies. Gene inactivation in vitro using short-interference RNA specific for NKX3.1 demonstrated an increase in BeWo cell differentiation and a decrease in HTR8-SVneo proliferation. We conclude that the decreased expression of homeobox gene NKX3.1 down-stream of EG-VEGF may contribute to the trophoblast dysfunction associated with idiopathic FGR pregnancies.