Towards routine detection of extracellular vesicles in clinical samples

Abstract

Extracellular vesicles (EVs) are cell-derived particles secreted by both eukaryotic and prokaryotic cells, as well as in the majority, if not all, body fluids. Such vesicles, initially described as “platelet dust”, have been extensively investigated in the last few decades. Based on their biogenesis, four main types of EVs can be distinguished: exosomes, microvesicles, retrovirus-like particles (RLPs) and apoptotic bodies. EVs are key mediators of intercellular communication and involved in fundamental biological processes such as blood coagulation, tissue regeneration, stem cell maintenance and immune response modulation. Furthermore, they have been implicated in the pathology underlying several diseases. So far, EVs have been linked to cancer development, infectious and neurodegenerative diseases as well as the spread of viruses and other pathogens. These vesicles are therefore gaining much attention as potential therapeutic targets and source of clinically relevant and noninvasive biomarkers that enable monitoring of physiology and diagnosis of several diseases. Despite the growing interest in EVs, a number of challenges persist regarding the application of EVs for clinical diagnostics. Standardized protocols for sample collection, analysis and processing are essential for study-to-study comparison. So far, a number of techniques to analyze EVs are utilized in mostly research laboratories. Depending on the information required, there are several detection options including EV number and size distribution, molecular surface markers and RNA content. Here, the focus is on recent findings in understanding EV biology, functions, detection methods as well as their potential in clinical diagnostics.