Assessment of innate immune response activation following the injection of extracellular vesicles isolated from human cell cultures in zebrafish embryos.

The release of extracellular vesicles (EVs) is a common feature of cells but the specific functional role of this secretion still remains poorly understood. EVs carry on their surface and in their lumen several molecules that act as signals, making EVs abundant and effective messengers for cell-to-cell communications. For instance, EVs released from cancer cells can modulate tumor invasiveness, and EVs produced in autoinflammatory diseases can improperly activate the immune system. We recently described an effect of EVs released from colorectal cancer cells in the immune-modulation of cytokine expression in zebrafish. Here, we detail a simple methodological approach to purify EVs from human cell media and to inject them in the zebrafish embryo circulation to follow in vivo the response of the innate immune system to EVs injection.