The Multifaceted Functions of Exosomes in Health and Disease: An Overview
Exosomes are extracellular vesicles of 50–150 nm in diameter secreted by basically all cell types. They mediate micro-communication among cells, tissues, and organs under both healthy and disease conditions by virtue of their ability to deliver macromolec
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The Multifaceted Functions of Exosomes in Health and Disease: An Overview Claudia Arenaccio and Maurizio Federico
1.1 Introduction Cytoplasm of eukaryotic cells contains several compartments, including trans- Golgi network, mitochondria, peroxisomes, endoplasmic reticulum, having different functions. Transport of macromolecules among these dynamic structures is mediated by vesicles moving in a densely populated microenvironment [1, 2]. In some instances, part of these vesicles are released into the extracellular milieu. Extracellular vesicles (EVs) are part of mechanism of intercellular communication, a function of vital importance for multicellular organisms. For decades, intercellular communication has been thought to be solely regulated by cell-to-cell contact and release of soluble molecules into the extracellular space. These molecules transmit the signal through their uptake or binding to specific receptors on target cells. However, the discovery of vesicular structures released into the extracellular space containing a multitude of factors including signaling molecules, proteins and nucleic acids, has opened a new frontier in the study of signal transduction, thereby adding a new level of complexity to our understanding of cell-to-cell communication. Body fluids (e.g., blood, urine, saliva, amniotic fluid, bronchoalveolar lavage fluid, synovial fluid, breast milk) contain various types of membrane-enclosed vesicles [3] recognizing different pathways of biogenesis. These vesicles possess different biophysical features and functions in health, e.g., protein clearance [4], immune regulation [5], cell signaling [6–8], as well as in disease, such as in infections [9–12] and cancer [13, 14]. Originally, EVs were thought to be garbage bags through which cells eject their waste. Today, it is widely accepted that EVs are key components of the intercellular communication network.
C. Arenaccio (*) • M. Federico National Center for Global Health, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2017 J. Xiao, S. Cretoiu (eds.), Exosomes in Cardiovascular Diseases, Advances in Experimental Medicine and Biology 998, DOI 10.1007/978-981-10-4397-0_1
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C. Arenaccio and M. Federico
All EV subtypes are limited by a lipid bilayer membrane surrounding a specific cargo of molecules, and having different sizes and buoyant densities. The variety of vesicles released from cells as well as the methods used to isolate them led to some confusion in their nomenclature. Current research mainly considers two types of EVs according to their biogenesis, i.e., ectosomes and exosomes. The term ectosomes indicates vesicles of 150–1000 nm in diameter directly budding from plasma membrane, whereas exosomes refer to vesicles of 30–150 nm in diameter generated intracellularly by inward invagination of endosome membranes leading to formation of intraluminal vesicles (ILVs). ILVs became part of multivesicular bodies (MVBs) which are released in th
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