Syncytiotrophoblast-derived extracellular products associated with preeclampsia

Abstract

The maternal-embryo-fetal interface is a site of exchange of biochemical and immune information. In a normal pregnancy, the syncytiotrophoblast releases different trophoblastic components including extracellular vesicles (EVs), microparticles (MPs), exosomes, and microRNA. These products exert local changes in the microenvironment and can impair different maternal functions. Placental exosomes can normally be detected in maternal blood from the first trimester of pregnancy and their levels increase until the end of gestation. The development of preeclampsia is partly related to abnormal secretion of these products and thus alteration of normal maternal mechanisms. Syncytiotrophoblastic MPs play an important role in the occurrence of thrombotic complications of pregnancy. Trophoblastic cells also release microRNA encapsulated within EVs or bound to Argonaute proteins, which are then passed onto the maternal circulation where they are highly stable. These proteins are specialized binding molecules that adapt to microRNA and participate in the silencing of genes and also interact with other proteins. Finally, the increased release of trophoblastic products causes alterations that contribute to maternal morbidity (preeclampsia) or the development of diseases in adult life in both the mother and newborn long after pregnancy has ended.