The release of RNA-containing extracellular vesicles (EV) into the extracellular milieu
has been demonstrated in a multitude of different in vitro cell systems and in a variety
of body fluids. RNA-containing EV are in the limelight for their capacity to communicate
genetically encoded messages to other cells, their suitability as candidate biomarkers
for diseases, and their use as therapeutic agents. Although EV-RNA has attracted enormous
interest from basic researchers, clinicians, and industry, we currently have limited
knowledge on which mechanisms drive and regulate RNA incorporation into EV and on
how RNA-encoded messages affect signalling processes in EV-targeted cells. Moreover,
EV-RNA research faces various technical challenges, such as standardisation of EV
isolation methods, optimisation of methodologies to isolate and characterise minute
quantities of RNA found in EV, and development of approaches to demonstrate functional
transfer of EV-RNA in vivo. These topics were discussed at the 2015 EV-RNA workshop
of the International Society for Extracellular Vesicles. This position paper was written
by the participants of the workshop not only to give an overview of the current state
of knowledge in the field, but also to clarify that our incomplete knowledge - of
the nature of EV(-RNA)s and of how to effectively and reliably study them - currently
prohibits the implementation of gold standards in EV-RNA research. In addition, this
paper creates awareness of possibilities and limitations of currently used strategies
to investigate EV-RNA and calls for caution in interpretation of the obtained data.
