Decreased circulating soluble Tie2 levels in preeclampsia may result from inhibition of vascular endothelial growth factor (VEGF) signaling.

OBJECTIVES: Recent studies have found dysregulation in circulating levels of a number of angiogenic factors and their soluble receptors in preeclampsia. In this study, we examined the mechanism of production of soluble Tie2 (sTie2) and its potential connection to the failure of vascular remodeling in preeclamptic pregnancies. DESIGN/SETTING/PATIENTS: Serum samples were collected prospectively from 41 pregnant subjects at five different time points throughout pregnancy. Five of these subjects developed preeclampsia. For a second study, serum and placental samples were collected at delivery from preeclamptic and gestational age-matched controls. We examined serum sTie2 levels, and angiopoietin 1, angiopoietin 2, and Tie2 mRNA expression and localization in placental samples from the central basal plate area. We also examined the effects of vascular endothelial growth factor (VEGF) and a matrix metalloproteinase (MMP) inhibitor on proteolytic shedding of Tie2 in uterine microvascular endothelial cells. RESULTS: Serum sTie2 levels were significantly lower in preeclamptic subjects starting at 24-28 wk of gestation and continued to be lower through the time of delivery. In culture experiments, VEGF treatment significantly increased sTie2 levels in conditioned media, whereas the MMP inhibitor completely blocked this increase, suggesting that VEGF-induced Tie2 release is MMP dependent. CONCLUSIONS: Our data suggest, for the first time, an interaction between VEGF and Tie2 in uterine endothelial cells and a potential mechanism for the decrease in circulating sTie2 levels in preeclampsia, likely through inhibition of VEGF signaling. Further studies on VEGF-Tie2 interactions during pregnancy should provide new insights into the mechanisms underlying the failure of vascular remodeling in preeclampsia and other pregnancy complications.

Variable expression of soluble fms-like tyrosine kinase 1 in patients at high risk for preeclampsia.

OBJECTIVE: To explore angiogenic factor differences in preeclamptic patients according to the absence or presence of underlying vascular disease. METHODS: We prospectively compared serum soluble fms-like tyrosine kinase 1 (sFlt1), soluble endoglin, and placental growth factor (PlGF) from 41 normal-risk and 32 high-risk (preexisting conditions) subjects at serial gestational ages. RESULTS: Median sFlt1 was lower at delivery in preeclamptic patients with underlying chronic hypertension and/or chronic proteinuria (5115 pg/ml) compared with normal risk preeclamptic patients (16375 pg/ml). PlGF was consistently low in patients who developed preeclampsia. CONCLUSIONS: Effects of sFlt1 may be contextual, varying according to the health or disease state of vascular endothelium.