Interplay between neutrophils and trophoblast cells conditions trophoblast function and triggers vascular transformation signals

Abstract

Normal placentation entails highly regulated interactions of maternal leukocytes with vascular and trophoblast cells to favor vascular transformation. Neutrophil activation and neutrophil extracellular trap (NET) formation associate with poor placentation and severe pregnancy complications. To deepen into the mechanisms of trophoblast–neutrophil interaction, we explored the effects of NETs on trophoblast cell function and, conversely, whether trophoblast cell‐derived factors condition neutrophils to favor angiogenesis and anti‐inflammatory signals required for fetal growth. NETs isolated from activated neutrophils hindered trophoblast cell migration. Trophoblast conditioned media prevented the effect as well as the vasoactive intestinal peptide (VIP) known to regulate trophoblast and neutrophil function. On the other hand, factors released by trophoblast cells and VIP shaped neutrophils to a proangiogenic profile with increased vascular endothelial growth factor synthesis and increased capacity to promote vascular transformation. Results presented here provide novel clues to reconstruct the interaction of trophoblast cells and neutrophils in vivo during placentation in humans.

Neutrophils in pregnancy: New insights into innate and adaptive immune regulation

“…In pre‐eclampsia, the increase in neutrophil activation and elevated release of syncytiotrophoblast microparticles from the placenta result in a noticeable increase in NET release at the maternal–fetal interface [ 56 ]. Excessive NETosis that characterizes this pregnancy complication hinders trophoblast migration and could be a contributor to defective placental development, scarce perfusion and increased inflammation [ 56 , 59 ]. NETs are also well renowned for their pro‐inflammatory effects and have also been shown to induce endothelial damage [ 60 ].…”

“…Other than localizing in proximity of these structures, they were shown to acquire a pro‐angiogenic phenotype, producing VEGF‐A, ARG‐1 and CCL2 and inducing formation of vascular networks [ 9 ]. This phenotype is also favoured by the release of trophoblast‐derived factors [ 59 ].…”

Decidual factors and vasoactive intestinal peptide guide monocytes to higher migration, efferocytosis and wound healing in term human pregnancy

“…Phagocytosis of apoptotic neutrophils by autologous CD14 + cells (efferocytosis) from non‐pregnant (NON‐P) or pregnant (P) blood samples was carried out as previously reported 5,7 . Neutrophils were obtained after the Ficoll‐Hypaque gradient and subsequent Dextran purification 7,8 . Apoptotic neutrophils were obtained after 20 hours incubation in RPMI 1640 (spontaneous apoptosis) and stained with 3 µM/10 6 cells of CFSE (Life Technologies, Buenos Aires) for 10 minutes in RPMI without FCS.…”

“…5,7 Neutrophils were obtained after the Ficoll-Hypaque gradient and subsequent Dextran purification. 7,8 Apoptotic neutrophils were obtained after 20 hours incubation in RPMI 1640 (spontaneous apoptosis) and stained with 3 µM/10 6 cells of CFSE (Life Technologies, Buenos Aires) for 10 minutes in RPMI without FCS. Excess of CFSE was eliminated by serial washes with RPMI 10% FCS.…”

“…VIP expression in syncyciotrophoblast of first and third trimester placentas was formerly reported 6 and it was shown to induce progesterone release in placental explants and BeWo trophoblast cell line. VIP has been assigned a regulatory role in early human pregnancy through targeting trophoblast, decidual cells and macrophages, 4,5 neutrophils 7,8 and Treg cells 9 . VIP modulated trophoblast cell function exhibiting a promigratory and pro‐invasive effect that depended on specific glucose uptake and mTOR activation in human cytotrophoblast cell lines in vitro 10,11 .…”