Soluble fms-like tyrosine kinase 1 and soluble endoglin are elevated circulating anti-angiogenic factors in pre-eclampsia

Pre-eclampsia, characterized by hypertension and proteinuria, affects approximately 3-5% of all pregnancies worldwide and is a major cause of maternal and fetal morbidity and mortality. Maternal endothelial dysfunction is associated with disease pathogenesis. Recently, reports have shown that elevated levels of circulating soluble fms-like tyrosine kinase 1 [sFlt1] and soluble endoglin [sEng] are associated with pre-eclampsia. Flt1 is a receptor for vascular endothelial growth factor receptor [VEGF], whereas endoglin [Eng] is an auxiliary receptor for transforming growth factor-β [TGF-β] super-family members. Both signaling pathways modulate angiogenesis and are involved in vascular homeostasis. Increased levels of sFlt1 and sEng dysregulate VEGF and TGF-β signaling respectively, resulting in endothelial dysfunction of maternal blood vessels. This review summarizes our current knowledge of Flt1 and endoglin and soluble forms in pre-eclampsia. Furthermore, it highlights the predictive and early-screening value of circulating levels of sFlt1 and sEng for the risk of developing pre-eclampsia.