Labeling, isolation and characterization of cell-type-specific exosomes derived from mouse skin tissue

Extracellular vesicles are a heterogeneous group of membrane-bound vesicles involved in cell-cell communication, formed at the plasma membrane (ectosomes) or by endocytosis (exosomes). Most exosome studies so far have focused on in vitro systems or exosomes derived from bodily fluids, while tissue-derived exosomes remain underexplored. Here we present a protocol using cell-type-specific promoter-driven reporter constructs for the targeted labeling and subsequent isolation of exosomes from specific cell types in vivo from mouse tissues. The differentiation between exosomes and ectosomes remains challenging due to limitations of current isolation techniques that are primarily based on size, density or surface markers. To address this issue, our approach leverages genetic engineering to mark exosomes specifically, enabling their precise identification and isolation from a complex biological pool of heterogenous extracellular vesicles. The isolated cell-type-specific exosomes are characterized by electron microscopy, nanoparticle tracking analysis, antibody exosome array assay and other established techniques. The labeling and isolation of exosomes spans 2-3 days and is designed to be accessible to researchers with fundamental laboratory competencies. This protocol facilitates the study of exosome-mediated cellular communication by enabling the isolation of cell-type-specific exosomes from either individual cell types or multiple cell types in combination. Most experiments within the protocol have used murine wound-edge skin tissue, but the protocol can, in principle, also be applied to other tissues to isolate exosomes, with a few modifications as required. This methodology opens new avenues for exploring the functional roles of cell-type-specific exosomes in intercellular communication.