Extracellular Vesicles: The Challenges on the Way and Engineering Perspectives

Extracellular vesicles (EVs) are found in every body fluid and are known to be released by every human cell. So far, EVs have been classified into three subclasses: Exosomes, microvesicles, and the less-studied apoptotic bodies. EVs are becoming increasingly acknowledged as crucial players in intercellular communication in various physiological and pathological conditions. The last two decades have witnessed the emergence of a plethora of research studies on the mechanisms by which EVs can regulate multiple biological functions (e.g., tissue homeostasis, immune response, tumor growth and metastasis, etc.). Therefore, they appear to hold substantial promise as therapeutic and drug/gene delivery agents, as proved by pre-clinical and clinical research. However, a complete understanding of cellular and molecular mechanisms governing the myriad functions of EVs still needs to be achieved. In this chapter, we give a brief overview of the classification and synthesis of EVs. Then we provide a few examples of the clinical trials using them to treat various disorders. Consequently, we highlight the main obstacles to the clinical translation of these subcellular therapeutic entities. We aim to define the knowledge gaps and to pinpoint critical questions. Furthermore, we address various engineering procedures for EVs that maximize their therapeutic potential and minimize their challenges.