The effect of maternal NODAL on STOX1 expression in extravillous trophoblasts is mediated by IGF1

The number of molecules identified to be involved in communication between placenta and decidua is fast expanding. Previously, we showed that NODAL expressed in maternal endometrial stromal cells is able to affect NODAL and STOX1 expression in placental extravillous trophoblasts. The effect of maternal NODAL on placental NODAL expression is achieved via Activin A, while preliminary data suggests that maternal NODAL affects STOX1 expression in trophoblasts potentially via IGF1. In the current study, T-HESC endometrial stromal cells were treated with siRNAs against NODAL after which IGF1 mRNA expression was determined by quantitative RT-PCR, while IGF1 secretion was measured by ELISA. Recombinant IGF1 and inhibitors of the MAPK and PI3K/AKT pathways were added to SGHPL-5 extravillous trophoblasts after which the effects on STOX1 mRNA and STOX1 protein expression were determined. The effect of IGF1 and the MAPK and PI3K/AKT inhibitors on the invasive capacity of SGHPL-5 cells was investigated by performing invasion assays. We found that T-HESC cells treated with NODAL siRNAs showed significant upregulation of IGF1 mRNA expression and IGF1 protein secretion. Addition of IGF1 to SGHPL-5 cell media significantly upregulated STOX1 mRNA and protein expression. Using inhibitors of the PI3K/AKT and MAPK pathway showed that the effect of IGF1 on STOX1 expression is accomplished via MAPK signaling. Secondly, PI3K inhibition independently leads to reduced STOX1 expression which can be rescued by adding IGF1. IGF1 was unable to influence the invasive capacity of SGHPL-5 cells, while inhibiting the PI3K/AKT pathway did reduce the invasion of these cells. To conclude, here we show that downregulated NODAL expression in endometrial stromal cells, previously associated with pre-eclampsia like symptoms in mice, increases IGF1 secretion. Increased levels of IGF1 lead to increased expression levels of STOX1 in extravillous trophoblasts via the MAPK pathway, hereby identifying a novel signaling cascade involved in maternal-fetal communication.