| Summary: | A successful strategy in regenerative medicine
over the last decade has been the translation of stem cell
therapy to repair diseased or damaged tissue in a wide
range of indications, despite limited evidence attributing
any therapeutic benefit to cell survival or differentiation.
Recent findings, however, have demonstrated that the
conditioned media from stem cell cultures can produce
similar efficacious effects compared to those observed for
cells. This has led to the stem cell paracrine hypothesis,
proposing that secreted factors released from the stem
cells contribute significantly to their beneficial effects. It
has been well documented that stem cells have the ability
to release a range of growth factors, cytokines and
chemokines relevant to their function; however, these
factors are released at levels too low to account for the
reported therapeutic effects. Further purification of the
conditioned media has since identified that not only are
small molecules released by the stem cells, but so too are
a large quantity of membrane-bound vesicles, including
exosomes, in a functionally relevant manner. In this
review, we present our current understanding and
explore the evidence supporting the development of stem
cell-derived exosomes as a cell-free regenerative
medicine.
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