Mechanisms in Decorin Regulation of Vascular Endothelial Growth Factor-Induced Human Trophoblast Migration and Acquisition of Endothelial Phenotype

Extravillous trophoblast (EVT) cells of the human placenta invade the uterine decidua and utero-placental arteries to establish an efficient exchange of key molecules between maternal and fetal blood. Trophoblast invasion is stringently regulated in situ both positively and negatively by a variety of factors at the fetal-maternal interface to maintain a healthy utero-placental homeostasis. One such factor, decorin, a transforming growth factor (TGF)-beta binding, leucine-rich proteoglycan produced by the decidua, negatively regulates EVT proliferation, migration, and invasiveness independent of TGFbeta. We reported that these decorin actions were mediated by its binding to multiple tyrosine kinase receptors, including vascular endothelial growth factor receptor (VEGFR)-2. The present study explores the mechanisms underlying decorin antagonism of VEGF (VEGF-A) stimulation of endovascular differentiation of EVT using our EVT cell line, HTR-8/SVneo. We observe that decorin inhibits VEGF-induced EVT cell migration and endothelial-like tube formation on matrigel. VEGF activates MAPKs (p38 MAPK, MEK3/6, and ERK1/2) in EVT cells, and the activation is blocked in both cases by decorin. Employing selective MAPK inhibitors, we show that both p38 and ERK pathways contribute independently to VEGF-induced EVT migration and capillary-like tube formation. VEGF upregulates the vascular endothelial (VE) markers VE-cadherin and beta-catenin in EVT and endothelial cells, and this upregulation is blocked by decorin and MAPK inhibitors. These results suggest that decorin inhibits VEGF-A stimulation of trophoblast migration and endovascular differentiation by interfering with p38 MAPK and ERK1/2 activation. Thus decorin-mediated dual impediment of endovascular differentiation of the EVT and angiogenesis may have implications for pathogenesis of pre-eclampsia, a hypoinvasive trophoblast disorder in pregnancy.