Reproduction Abstracts

Introduction: The human placenta continuously extrudes, into the maternal circulation, vast quantities of extracellular vesicles (EVs) which have the ability to alter maternal physiology. There are three sizes of placental EVs multinucleated macro-EVs, subcellular micro- and nano- EVs. Macro-EVs are trapped in the maternal lungs due to their large size. We investigated the organs with which micro- and nano- EVs interact in vivo and their potential effects EVs on vascular function.

Methods: Placental micro- and nano- EVs, isolated from cultured human placentae by sequential ultracentrifugation (20,000 g and 100,000 g, respectively), were labelled and injected into groups of 4–6 female CD1 mice via the tail vein. After 2 minutes, 30 minutes or 24 hours, fluorescence in the brain, thymus, lungs, heart, liver, spleen, kidneys was quantified using an IVIS Kinetic Imager at 605/640 nm. Mesenteric resistance artery function was assessed using wire myography. Statistical significance was assessed by the Fisher Exact test and two-way ANOVA.

Results and Discussion: At two minutes post-injection, micro-EVs were detected in the lungs, while nano-EVs were detected in the lungs, liver and kidneys (P=0.026). At 30 minutes, the distribution of nano-EVs was unchanged whereas, micro-EVs remained in the lungs but had also spread to the liver and kidneys. By 24 hours, micro-EVs remained only in the liver and kidneys while nano-EVs were cleared from the kidneys but remained in the lungs and liver (P=0.005). Myography indicated that there was no effect of nano-EVs on the ability of mesenteric arteries to vasoconstrict or undergo endothelium-dependent and –independent relaxation, in response to U46619, acetylcholine or sodium nitroprusside respectively (n=5). We have shown that placental micro- and nano- EVs have distinct patterns of distribution in vivo possibly reflecting their different targeting receptors. Preliminary work indicates that nano-EVs from normal placentae do not affect resistance artery function, at least in non-pregnant animals.