In the past decade, extracellular vesicles (EVs) have been recognized as potent vehicles of intercellular communication, both in prokaryotes and eukaryotes. This is due to their capacity to transfer proteins, lipids and nucleic acids, thereby influencing various physiological and pathological functions of both recipient and parent cells. While intensive investigation has targeted the role of EVs in different pathological processes, for example, in cancer and autoimmune diseases, the EV-mediated maintenance of homeostasis and the regulation of physiological functions have remained less explored. Here, we provide a comprehensive overview of the current understanding of the physiological roles of EVs, which has been written by crowd-sourcing, drawing on the unique EV expertise of academia-based scientists, clinicians and industry based in 27 European countries, the United States and Australia. This review is intended to be of relevance to both researchers already working on EV biology and to newcomers who will encounter this universal cell biological system. Therefore, here we address the molecular contents and functions of EVs in various tissues and body fluids from cell systems to organs. We also review the physiological mechanisms of EVs in bacteria, lower eukaryotes and plants to highlight the functional uniformity of this emerging communication system.

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Biological properties of extracellular vesicles and their physiological functions

Essential fatty acids in growth and development

Geigy Scientific Tables

Lipids of nervous tissue: composition and metabolism.

Lipids in exosomes: Current knowledge and the way forward.

Prostasomes are membranous vesicles (150–200 nm diameter) present in human semen. They are secreted by the prostate and contain large amounts of cholesterol, sphingomyelin and Ca2+. In addition, some of their proteins are enzymes. Prostasomes enhance the motility of ejaculated spermatozoa and are involved in a number of additional biological functions. The possibility that they may fuse to sperm has never been proved. In this work, we studied the fusion of sperm to prostasomes by using various methods (relief of octadecyl Rhodamine B fluorescence self-quenching, fluorescence microscopy and flow cytometry) and we found that it occurs at acidic pH (4–5), but not at pH 7.5 pH-dependent fusion relies on the integrity of one or more proteins and is different from the Ca2+-stimulated fusion between rat liver liposomes and spermatozoa that does not require any protein and occurs at neutral pH.
 We think that the H+-dependent fusion of prostasomes to sperm may have physiological importance by modifying the lipid and protein pattern of sperm membranes.

Fusion of Human Sperm to Prostasomes at Acidic pH

Fusion of sperm with prostasomes: effects on membrane fluidity.

Fatty acid pattern of human prostasome lipid

— The calcium-dependent incorporation of L-[3-14C]serine and [1,2−14C]ethanolamine into the phospholipid of isolated neuronal and glial cells from rabbit brain was studied, and the distribution of the enzymic system among the correspondent subfractions was examined. The neuronal cell-enriched fraction was found to possess a much higher rate of exchange of both bases than the glial cell-enriched fraction. Among the sub-fractions isolated from the neuronal and glial cells, those corresponding to neuronal plasma membranes and microsomes showed a noticeably higher exchange of serine and ethanolamine compared to the corresponding subfractions from glia. Neuronal/glial ratios of about 6–8 were found for the exchange activity in both plasma membrane-enriched fraction and in microsomes. Synaptosomes and synaptosomal subfractions contained low activities. It is concluded that the calcium-dependent enzymic system for the exchange of serine, ethanolamine and other nitrogenous bases with endogenous phospholipid is concentrated mostly in the neuronal perikaryal membranes, and could be used as a neuronal marker.

Base-exchange enzymic system for the synthesis of phospholipids in neuronal and glial cells and their subfractions: a possible marker for neuronal membranes.

Giuseppe Arienti

Papers

Fusion of Human Sperm to Prostasomes at Acidic pH

Fusion of sperm with prostasomes: effects on membrane fluidity.

Fatty acid pattern of human prostasome lipid

Base-exchange enzymic system for the synthesis of phospholipids in neuronal and glial cells and their subfractions: a possible marker for neuronal membranes.

The motility of human spermatozoa as influenced by prostasomes at various pH levels.