An Implanted Device Enables In Vivo Monitoring Of Extracellular Vesicle-Mediated Spread Of Pro-Inflammatory Mast Cell Response In Mice

Mast cells have been shown to release extracellular vesicles (EVs) in vitro. However, EV-mediated mast cell communication in vivo remains unexplored. Primary mast cells from GFP-transgenic and wild type mice, were grown in the presence or absence of lipopolysaccharide (LPS), and the secreted EVs were separated from the conditioned media. Mast cell-derived EVs were next cultured with LPS-naive mast cells, and the induction of TNF-alpha expression was monitored. In addition, primary mast cells were seeded in diffusion chambers that were implanted into the peritoneal cavities of mice. Diffusion chambers enabled the release of GFP(+) mast cell-derived EVs in vivo into the peritoneal cavity. Peritoneal lavage cells were assessed for the uptake of GFP(+) EVs and for TNF-alpha production. In vitro, LPS-stimulated mast cell-derived EVs were efficiently taken up by non-stimulated mast cells, and induced TNF-alpha expression in a TLR4, JNK and P38 MAPK dependent manner. In vivo, using implanted diffusion chambers, we confirmed the release and transmission of mast cell-derived EVs to other mast cells with subsequent induction of TNF-alpha expression. These data show an EV-mediated spreading of pro-inflammatory response between mast cells, and provide the first in vivo evidence for the biological role of mast cell-derived EVs.