While the mammalian macrophage phenotypes have been intensively studied in vitro,the dynamic of their phenotypic polarization has never been investigated in live vertebrates. Weused the zebrafish as a live model to identify and trail macrophage subtypes. We generateda transgenic line whose macrophages expressingtumour necrosis factor alpha(tnfa), a key feature ofclassically activated (M1) macrophages, express fluorescent proteinsTg(mpeg1:mCherryF/tnfa:eGFP-F). Using 4D-confocal microscopy, we showed that both aseptic wounding andEscherichia coliinoculation triggered macrophage recruitment, some of which started to expresstnfa. RT-qPCR onFluorescence Activated Cell Sorting (FACS)-sorted tnfa+and tnfa−macrophages showed that they,respectively, expressed M1 and alternatively activated (M2) mammalian markers. Fate tracing oftnfa+macrophages during the time-course of inflammation demonstrated that pro-inflammatorymacrophages converted into M2-like phenotype during the resolution step. Our results reveal thediversity and plasticity of zebrafish macrophage subsets and underline the similarities withmammalian macrophages proposing a new system to study macrophage functional dynamic
© Nguyen Chi et al.