Small extracellular vesicles that carry molecular cargo between cells — and a distinct category from the stem cells that often produce them.
Exosomes form through a specific intracellular pathway: they originate as intraluminal vesicles inside larger structures called multivesicular bodies (MVBs) within the cell. When an MVB fuses with the cell's outer membrane, its internal vesicles are released into the extracellular space as exosomes. This origin distinguishes exosomes from other extracellular vesicle types, such as microvesicles, which bud directly from the outer cell membrane.
Exosomes are bounded by a lipid bilayer membrane — structurally similar to a cell membrane — but contain no nucleus, cannot replicate, and are not alive in the sense that a cell is.
Exosomes carry a molecular cargo that can include:
This cargo is delivered to other cells when the exosome is taken up — through membrane fusion, receptor-mediated uptake, or endocytosis — allowing exosomes to transmit molecular signals between cells without direct cell-to-cell contact.
Exosome-based products used in regenerative applications are typically derived from the secretions of cultured mesenchymal stem cells, isolated from the surrounding culture medium rather than administered as whole cells. Because the source cells remain in culture and are not part of the final product, exosome preparations are considered acellular.
This page is educational reference material for licensed healthcare providers and does not constitute medical, legal, or regulatory advice. HCT/P products are not FDA-approved.