Studying the fate of tumor extracellular vesicles at high spatio-temporal resolution using the zebrafish embryo

Abstract

SummaryTumor extracellular vesicles (tumor EVs) mediate the communication between tumor and stromal cells mostly to the benefit of tumor progression. Notably, tumor EVs have been reported to travel in the blood circulation, reach specific distant organs and locally modify the microenvironment. However, visualizing these eventsin vivostill faces major hurdles. Here, we show a new method for tracking individual circulating tumor EVs in a living organism: we combine novel, bright and specific fluorescent membrane probes, MemBright, with the transparent zebrafish embryo as an animal model. We provide the first description of tumor EVs’ hemodynamic behavior and document their arrest before internalization. Using transgenic lines, we show that circulating tumor EVs are uptaken by endothelial cells and blood patrolling macrophages, but not by leukocytes, and subsequently stored in acidic degradative compartments. Finally, we prove that the MemBright can be used to follow naturally released tumor EVsin vivo. Overall, our study demonstrates the usefulness and prospects of zebrafish embryo to track tumor EVsin vivo.HighlightsMemBright, a new family of membrane probes, allows for bright and specific staining of EVsZebrafish melanoma EVs are very similar to human and mouse melanoma EVs in morphology and protein contentThe zebrafish embryo is an adapted model to precisely track tumor EVs dynamics and fate in a living organism from light to electron microscopyCirculating tumor EVs are rapidly uptaken by endothelial cells and patrolling macrophagesCorrelated light and electron microscopy can be used in zebrafish to identify cells and compartments uptaking tumor EVsBlurbDispersion of tumor extracellular vesicles (EVs) throughout the body promotes tumor progression. However the behavior of tumor EVs in body fluids remains mysterious due to their small size and the absence of adapted animal model. Here we show that the zebrafish embryo can be used to track circulating tumor EVsin vivoand provide the first high-resolution description of their dissemination and uptake.