Ectopically Expressed IL-34 Can Efficiently Induce Macrophage Migration to the Liver in Zebrafish

Interleukin-34 (IL-34) is a known cytokine that plays an important role in the survival, proliferation, and differentiation of macrophages. In previous studies, IL-34 can induce macrophage migration through syndecan-1 or focal adhesion kinase and extracellular signal-related kinase 1 and 2 pathway. These studies mainly focused on in vitro experiments, but the effect of IL-34 on macrophage migration in vivo is less understood. In our study, we artificially induced macrophage, but not neutrophil, enrichment in the skin or liver by overexpressing IL-34 in epidermal cells or hepatocytes in zebrafish. Live imaging showed that the enrichment of macrophages in the liver is due to the direct attraction of macrophages by IL-34. Our results demonstrated that ectopically expressed IL-34 can induce macrophage migration to liver in vivo.