Biodistribution of Modified Extracellular Vesicles In Normal and Tumor-Bearing Animal Models

Abstract

Exosomes are one of the extracellular vesicles (EVs) that range in diameter from 30-150 nm. They are formed by early budding into early endosomes then released by the cell from late endosome. The content of EVs includes proteins, mRNA, miRNA, and DNA derived from the original cell where they were released. Due to the membrane structure of EVs, which resemble the original cell, and the ability to alter the EVs cargo, EVs are extensively studied as an approach for the development of drug delivery system and as immunotherapy. miR-424/322 is a microRNA that present in some tumor-derived EVs and plays a role in regulating anti-tumor immune response. Our lab has shown that modified EVs with miR-424/322 blockade prevented the initiation of tumor in colorectal cancer (CRC) animal model through inducing the antitumor immune response. One of the critical aspects of using EVs as a therapy and/or a drug delivery system is to understand their biodistribution in vivo. In this thesis, we systemically injected modified EVs labeled with the lipophilic dye DiO to both normal and orthotopic-tumor animal models. We harvested the following tissues: blood, heart, lung, spleen, liver, kidney, lymph nodes, bone marrow, GI, muscle, and tumor 30 min post-injection and analyzed their single-cell suspension preparations using flow cytometry analysis. Our data showed that EVs are mainly distributed to the lung, liver and spleen in naïve animals. For tumor-bearing animals more data is required to determine the potential difference between the two groups. In conclusion, EVs administered intravenously to the animal generally followed the biodistribution pattern of previously published studies that used the same rout of injection.