cell–cell communication |
Exosomes
can participate in an autocrine, paracrine, or endocrine
communication reaching their target cells via the systemic or local
circulation. They are important participants in cell communication
including cell migration, proliferation, and senescence.66,67
|
immune response |
The cells
of the immune system are known to release exosomes.29 Exosomes mediate immune modulation, both immunosuppression
and immunostimulation.68
|
signal transduction |
Exosomes enable intercellular
communication between various
types of cells, regulating gene expressions and cellular signaling
pathways of recipient cells by delivering their components, such as
specific lipids, proteins, and RNAs. Certain lipid components including
sphingomyelin, cholesterol, and ceramides have been involved in signaling;69,70 phosphatidylinositol-3-phosphate (PI3P) is also known to participate
in regulating cell signaling.71 The presence
of multiple kinds of signaling molecules—lipids, proteins, and RNAs—results in rapid signal changes in the target cell. |
material (cargo) transport |
Exosomes transport their
constituents involving proteins, nucleic
acids, lipids, and metabolites between cells, both in the close vicinity
of the parent cell and at distant sites in the body carried by biofluids.
It has been reported that RNA cargo of exosomes can modify gene expression
in recipient cells.72,73
|
pathogenesis |
Viruses are known to make use of exosome biogenesis pathways
to release a variety of pathogenic factors. Thus, a number of pathogen-derived components have been detected
on exosomes after infection. These include, e.g., human immunodeficiency virus, Epstein–Barr virus, cytomegalovirus, hepatitis C virus, and herpes simplex virus.74 Exosomes
play multiple roles in the progression of cancer via various communication
pathways.75 Exosomes are more often released
by tumor cells than by healthy ones and facilitate communication within
the tumor microenvironment.76
|
blood–brain communication |
Exosomes are able to cross the BBB in both directions—from the brain to the bloodstream and from the blood to the CNS. Moreover,
exosomes can interact with the BBB, leading to changes in the barrier’s
properties.77
|
target cell delivery |
The delivery of cargos such as
bioactive RNAs, proteins, metabolites, and/or lipid makes the capture of exosomes by target
cells of vital importance in a variety
of key biological processes such as angiogenesis,78 bone development,79 and cell
migration.80
|