Extracellular vesicles in physiological and pathological conditions in humans

Extracellular vesicles (EVs) are small vesicles (or membrane-bound organelles) that can be found in blood and other biofluids (urine, breast milk, cerebrospinal fluid, saliva, etc.) and their internal content and surface reflect their origin and potential function. EVs are classified depending on their size in exosomes (< 150 nm) and microvesicles (> 150 nm) or ectosomes (up to 1000 nm). EVs may contain genetic material such as DNA (e.g., cell free DNA [cfDNA] and circulating tumor DNA [ctDNA]), RNA (e.g., microRNAs, small nucleolar RNAs, piwi-interacting RNAs, long non-coding RNAs), proteins, and metabolites (e.g., lipids). EVs have been suggested to play a role in intercellular signaling and cell-to-cell communication, and have been associated with many physiological functions, including immune function, development, normal homeostasis, and aging. In addition, EVs have also been suggested to play a role in human diseases, especially cancer, which potentially contributes to oncogenesis, tumor immunity, metastasis, and in the development of chemoresistance. EVs may also play a role in inflammation, and infectious, neurological and cardiometabolic diseases. Due to their presence in biofluids and the biological information they carry, EVs have been identified as potential non-invasive biomarkers in several diseases (i.e., liquid biopsy). Other applications of EVs include using them as biomarkers of toxicity between environmental toxicants (e.g., air pollution or endocrine disruptors) and human health (e.g., blood pressure or metabolism). In this chapter, we summarize the most recent findings about the potential role of EVs in human health and diseases and discuss future directions.