Extracellular vesicles (EVs) (a.k.a.Exosomes ) are small protected packets of extracellular RNA that are produced on the cell membrane of most eukaryotic cells. They can separate from the cell wall and travel freely in any bodily fluid.

For many years, double-layer phospholipid membrane vesicles, released by most cells, were not considered to be of biological significance. This stance has dramatically changed with the recognition of extracellular vesicles (EVs) as carriers of biologically active molecules that can traffic to local or distant targets and execute defined biological functions."

Source : PLOS Biology, 2019

150 years ago, Charles Darwin theorised that every cell type in the body might generate 'germules' - which he suggested, were particles that could contain molecules used to 'communicate' with other cell types.

Largely dismissed as 'cell dust' in the intervening period, they are now again the subject of research as a possible communication system between cells.

It's now known that extracellular vesicles (microscopic fatty packages which contain proteins etc) - are not only released by bacteria, but by virtually every cell in multicellular organisms. They entrap nucleic acids, diverse cellular proteins, and metabolites - and are predicted to transfer their packaged molecules from one cell to another.

The following types of RNA have been so far detected outside cells, within EVs.

Messenger RNA (mRNA) Transfer RNA (tRNA) MicroRNA (miRNA) Small interfering RNA (siRNA) Long non-coding RNA (lncRNA)

Their precise function however, if there is one, is yet to be described. If it's confirmed that they are a means of chemical and/or genetic 'communication' between cells, it could have very profound implications for biological, and especially medicinal, research.

Further info :The International Society For Extracellular Vesicles

Technical details (listing seven 'unsolved mysteries' of EVs) here : PLoS Biol 17(7): e3000363

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