Exosomes are 30-100 nm microvesicles which contain complex cellular signals of RNA, protein and lipids. Because of this, exosomes are implicated as having limitless therapeutic potential for the treatment of cancer, pregnancy complications, infections, and autoimmune diseases. To date we know a considerable amount about exosome biogenesis and secretion, but there is a paucity of data regarding the uptake of exosomes by immune and non-immune cell types (e.g., cancer cells) and the internal signalling pathways by which these exosomes elicit a cellular response. Answering these questions is of paramount importance.
Schematic of exosome biogenesis, internalization and cellular response
The adhesion of exosomes to the recipient cell utilizes the interaction of various exosomal surface proteins and cellular receptors. Once bound, the exosome may (i) elicit transduction of the signal via intracellular signalling pathways and be released (juxtacrine signalling); (ii) fuse with the cellular membrane transferring protein and genetic contents, into the cytoplasm of the recipient cell (fusion); or (iii) be endocytosed via phagocytosis, macropinocytosis or receptor-mediated endocytosis.