Do antiphospholipid antibodies alter the targeting of placental extracellular vesicles in the maternal body?

Abstract

A healthy placenta is not only fundamental to delivering a healthy baby at term, but also to the health of the mother during pregnancy. The human placenta extrudes extracellular vesicles (EVs) containing cargo reflective of the health of the placenta, into the maternal blood. These EVs can be targeted to specific maternal organs where they may influence maternal adaptations during pregnancy. Antiphospholipid antibodies (aPL) are autoantibodies that are associated with adverse pregnancy outcomes and have been shown to induce changes in the syncytiotrophoblast, causing changes to the cargo of placental EVs. I hypothesize that exposing human first trimester placentae to aPL, may affect the bio-distribution of the aPL-affected EVs in the maternal body. To investigate whether aPL change the bio-distribution of placental EVs, a protocol was first established to produce fluorescently-labelled placental EVs suitable for in vivo experiments. Human first trimester placentae were treated with CellTracker™ Red CMTPX and either ID2 or control IgG antibody. Extracellular vesicles harvested from these placentae were then stained with the near-infrared fluorescent stain, sulfo-cyanine 7 NHS-ester (Cy7), and methods to separate the stained EVs from free stain were optimised. The double-labelled EVs were injected intravenously into pregnant CD1 mice. Organs/tissues of those mice were collected 30 minutes after injection, and Cy7 fluorescence was quantified using an AMI HTX whole-organ imager, to determine EV bio-distribution. The bio-distribution of aPL-affected first trimester placental micro-vesicles was increased in the liver of pregnant CD1 mice compared with control micro-vesicles. No differences were found in the bio-distribution of aPL-affected placental nano-vesicles compared with control. These findings coincide with current clinical knowledge that pregnant women with aPL have increased risks of developing pregnancy complications involving liver damage. These findings suggest micro-vesicles may be a mechanism contributing to development of some of the pregnancy complications that are associated with aPL, possibly by effects on the liver.