Interest and subsequent research into exosomes is continuing in the fields of science and medicine, due in large part to the recent discovery that exosomes contain functional RNA. Exosomes, in a living organism, are present in several bodily fluids, for example: joint membrane, saliva, urine, amniotic fluids, plasma and many cells in the human body are able to produce and release exosomes into their neighbouring environment.
As we now know that exosomes can act as a mediator of biological functions through delivery of RNA to cells, including antigen presentation, one example of research into this area was into the determining of the presence of RNA in saliva and an investigation into whether exosomes in saliva can be absorbed by macrophages (the phagocytic cells found stationary in tissue or fluid in white blood cells).
The study revealed a positive result which endorsed the theory that exosomal RNA can be transported between cells. The research was done using fluorescence microscopy, flow cytometry and showed mRNA to be present in plasma exosomes alongside findings confirming that exosomal RNA can, as hypothesized, be shuttled between cells. Immunogold staining was used to show the presence of a tetraspanin (CD63), (a known exosome marker) and the stained exosomes were seen to have been take up by macrophages.
The relevance of in vivo uptake of exosomes deriving from body fluids (in this case the saliva testing) was deemed important when considering that fact that acidic conditions increase ingestion of tumour exosomes, leading research to believe that saliva exosomes could be taken up in the acidic conditions of the gut area.
Exploration was undertaken of three fluids in total: saliva, plasmas and breast milk. Interesting and extremely important findings were reported on the latter in terms of mother/offspring cellular connection which, with respect to the presence of exosomes, is something that had not previously been look at .
However, given that the consensus is still that most of the shuttling of RNA is taking place in the immediate micro environment of cells so no conclusions on any exosome being beneficial to offspring were made in the particular study, which was featured in the Journal of Translational Medicine.