Fetal membrane extracellular vesicle profiling reveals distinct pathways induced by infection and inflammation in vitro

Problem: Fetal inflammatory signals can be propagated to maternal tissues to initiate labor via exosomes (extracellular vesicles; 30-150 nm). We tested the hypothesis that fetal membrane cells exposed to infectious and inflammatory mediators associated with preterm birth (PTB) produce exosomes with distinct protein cargo contents indicative of underlying pathobiology. Methods of study: Fetal membrane explants (FM) as well as primary amnion epithelial (AEC) and mesenchymal cells (AMC), and chorion cells (CC) from term deliveries were maintained in normal conditions (control) or exposed to LPS 100 ng/mL or TNF-α 50 ng/mL for 48 hours. Exosomes were isolated from media by differential centrifugation and size exclusion chromatography and characterized using cryo-electron microscopy (morphology), nanoparticle tracking analysis (size and quantity), Western blot (markers), and mass spectroscopy (cargo proteins). Ingenuity pathway analysis (IPA) determined pathways indicated by differentially expressed proteins. Results: Irrespective of source or treatment, exosomes were spherical, had similar size, quantities, and markers (ALIX, CD63, and CD81). However, exosome cargo proteins were different between FM and individual fetal membrane cell-derived exosomes in response to treatments. Several common proteins were seen; however, there are several unique proteins expressed by exosomes from different cell types in response to distinct stimuli indicative of unique pathways and physiological functions in cells. Conclusions: We demonstrate collective tissue and independent cell response reflected in exosomes in response to infectious and inflammatory stimuli. These cargoes determined underlying physiology and their potential in enhancing inflammation in a paracrine fashion.