P44. Syncytiotrophoblast extracellular membrane vesicles from preeclamptic placentae show reduced abilities to guide monocyte maturation and activation as well as reduced activation of cytotoxicity of regulatory T-cells and NK-cells

Abstract

Introduction Syncytiotrophoblast extracellular membrane vesicles (STBEV) are thought to be involved in the pathogenesis of preeclampsia (PE). They might play a role in directing the immune response and monocyte activation in PE. Objectives We hypothesize, that STBEV from preeclamptic placentae induced an altered activation pattern of peripheral immune cells compared to normal STBEV. Methods STBEV were gathered after 2 hours of ex vivo placenta perfusion and isolated from perfusion suspension by centrifugation (microvesicles, 30 min 19.000 g) or ultra-centrifugation (exosomes, 70 min 100.000 g). Peripheral blood of healthy non-pregnant women was stimulated for 24 hours with either microvesicles or exosomes. Distribution and activation of immune cell subsets were analyzed via flow-cytometry. Monocytes and granulocytes were stained for monocytes (CD115, CD14, CD16), granulocytes (CD66b) and the activation marker CD11b. Lymphocyte subsets were stained for T-cells, NK-cells and NKT-cells (CD3, CD8, CD16, CD56); T-helper cells (Th1 – Tbet, Th2 – CD294, Th17 – RoRgt); regulatory T-cells (FoxP3) and markers for activation (CD69), memory function (CD45Ro) and cytotoxicity (Perforin, GranzymeB, GranzymeK). Results Normal STBEV upregulated the number of intermediate monocytes (CD14++CD16+) and activated monocytes and granulocytes, while monocyte maturation and activation was reduced with PE STBEV. Also, normal STBEV promoted a Th1 phenotype whereas PE STBEV supported a Th2/Th17 phenotype. Cytotoxicity was induced in memory T-cells, NKT-cells and CD16+CD56++ NK-cells by normal STBEV. PE STBEV induced reduced cytotoxicity, especially in regulatory immune cell subsets like CD8+ memory Treg- and CD16+CD56++ NK-cells. The effects of normal placentae were induced by both STBEV types, still exosomes showed a more prominent impact. Although PE STBEV in general led to a reduced immune activation compared to normal STBEV, PE microvesicles showed increased activation abilities. Conclusion Incubation with normal STBEV led to activation of monocytes, granulocytes, memory T-cells, NKT-cells and CD16+CD56++ NK-cells. PE STBEV showed reduced abilities to activate these cell types, especially Treg- and NK-cells. We suggest that this reduction of regulatory immune subsets supports an impairment of the immune system as seen for example in PE. However, PE STBEV does not induce the increased activation of monocytes apparent in PE. Concluding, our data show that placental exosomes have a more prominent effect in healthy pregnancy, while the deregulatory effect of microvesicles increases in PE.