Extracellular Vesicles in Veterinary Medicine

SIMPLE SUMMARY: Extracellular vesicles (EVs) are small vesicles released by human and animal cells, parasites, microorganisms, and plants. They travel within bodily fluids, transferring the content of their cell of origin to other cells, being both intra- and inter-organism messengers. This EV-mediated method of communication governs many normal functions as well as disease processes. Because of this important role, EVs have been largely studied since 1984, mainly in humans, but more recently also in animals, parasites, and bacteria. In this review, we explore the literature on EVs in animals between 1984 and 2021 and summarize the most important results of approximately 220 scientific papers. Results are presented based on the main topic of research, such as EVs in physiology and pathophysiology, use of EVs as markers to diagnose diseases, or as possible natural transporters of therapies or vaccines. Since working with EVs is challenging, we also address the critical technical points found in the veterinary literature. Finally, we included a brief summary on EVs shed within animal milk, an area of large interest for the multiple applications for human health. ABSTRACT: Extracellular vesicles (EVs) are cell-derived membrane-bound vesicles involved in many physiological and pathological processes not only in humans but also in all the organisms of the eukaryotic and prokaryotic kingdoms. EV shedding constitutes a fundamental universal mechanism of intra-kingdom and inter-kingdom intercellular communication. A tremendous increase of interest in EVs has therefore grown in the last decades, mainly in humans, but progressively also in animals, parasites, and bacteria. With the present review, we aim to summarize the current status of the EV research on domestic and wild animals, analyzing the content of scientific literature, including approximately 220 papers published between 1984 and 2021. Critical aspects evidenced through the veterinarian EV literature are discussed. Then, specific subsections describe details regarding EVs in physiology and pathophysiology, as biomarkers, and in therapy and vaccines. Further, the wide area of research related to animal milk-derived EVs is also presented in brief. The numerous studies on EVs related to parasites and parasitic diseases are excluded, deserving further specific attention. The literature shows that EVs are becoming increasingly addressed in veterinary studies and standardization in protocols and procedures is mandatory, as in human research, to maximize the knowledge and the possibility to exploit these naturally produced nanoparticles.