Exosomes and extracellular vesicles, explained plainly

The definition

Extracellular vesicles are membrane-bound particles released by nearly every cell type. They carry proteins, lipids and nucleic acids, and they are one of the ways cells signal to each other. Exosomes are one size class of these vesicles.

The key structural fact: an exosome product contains no living cells. It is a cell-free preparation, which makes it a different kind of product from a cell therapy, not a refined version of one.

Where they come from

Commercial preparations are typically harvested from the fluid that cultured cells have been grown in — frequently mesenchymal stromal cells, sometimes placental or amniotic material. The parent cell source, the culture conditions and the isolation method all change what ends up in the final vial.

Studied uses versus marketed uses

The research literature on extracellular vesicles is genuinely large and genuinely interesting, concentrated in laboratory and animal work on tissue repair, immune modulation and drug delivery. Reviews in this area consistently identify the same translational bottlenecks: isolation methods are not standardised, potency is hard to define, and dosing has no accepted unit.

Marketed uses run well ahead of that. Products are sold for joints, skin, hair, fatigue and neurological conditions, none of which is supported by an approved product anywhere.

Evidence and regulatory reality

The FDA states plainly that there are currently no FDA-approved exosome products. Any exosome product being administered in the United States is unapproved.

Because there is no agreed potency assay, two vials labelled with the same particle count can differ substantially in content. This is a measurement problem, not a marketing quibble: it limits what any published study can tell you about the specific product in front of you.

Questions worth asking a provider

• What cells produced these vesicles, and who manufactured the product?
• How was the preparation isolated and characterised?
• What is the dose, and in what unit is it expressed?
• Can I see a certificate of analysis, including sterility and endotoxin testing, for this lot?
• Under which regulatory pathway is this being supplied here?