Macrophage- but not monocyte-derived extracellular vesicles induce placental pro-inflammatory responses.

The placenta sheds extracellular vesicles (EVs), including exosomes, into the maternal circulation. We recently demonstrated that this trafficking of EVs is bi-directional; with uptake of macrophage exosomes by the placenta inducing cytokine release. The specificity of this response is currently unknown. THP-1 cells were cultured as monocytes or differentiated to macrophages, and EVs isolated by ultra-centrifugation. The effect of EVs on human placental explants was measured by cytokine ELISA/luminex. Macrophage, but not monocyte, EVs induce the release of pro-inflammatory cytokines by the placenta. Thus, placental responses to immune cell EVs, including exosomes, reflects the phenotype of the source cell.