We do know that exosomes are tiny particles that bud off from cells and that their contents can vary hugely, depending on the source of the cell (some popular options include human umbilical cords, salmon testicles, and roses) and how healthy or stressed it is. Even cell biologists can’t agree on what, exactly, is inside them, and how beneficial—or dangerous—those contents may be.
The world of exosome treatments is being likened to a “Wild West” by some researchers. Rigorous trials have not been conducted, so we don’t know how safe it is to spray on or inject these tiny mystery blobs. Exosome products have not been approved by regulatory agencies in the US, UK, or Europe, where the treatments are growing in popularity. Nor have they been approved for medical uses in Japan or South Korea, two other countries where exosome treatments are popular. Still, “exosomes have emerged as a sort of panacea for almost everything,” says Leigh Turner, a bioethicist and public health researcher at the University of California, Irvine, who tracks direct-to-consumer marketing of unapproved health products. “Risks are commonly minimized, and benefits are commonly exaggerated.”
This hasn’t stopped customers from flocking to the growing number of aesthetic centers, stem-cell clinics, and medspas offering exosome treatments, hoping for a miracle fix. The global market for exosome skin-care products was valued at $256 million in 2023 and is forecast to grow to $674 million in the next six years.
Mystery blobs
Technically referred to as vesicles, exosomes are made inside cells before being released. They’ve long been mysterious. The term “exosome” was introduced in the 1980s. Before that, tiny particles that are now thought to have been exosomes were described as “platelet dust” or “matrix vesicles.”
At first, scientists assumed that exosomes functioned as trash bags, shuttling waste out of the cell. But research in 1996 suggested that exosomes might also work to help cells communicate by delivering signals between them. If a cell is dying, for instance, it could perhaps send a signal to neighboring cells, giving them a chance to produce more protective substances in order to save themselves from the same fate. Cancer cells, on the other hand, could potentially use exosomes to send signals that co-opt other cells to support the growth of a tumor. Still, it’s not fully understood what signals are actually being sent.
Another major mystery is what, exactly, is inside exosomes. “It depends who you ask,” says James Edgar, who studies exosomes and similar vesicles at the University of Cambridge, UK. Cell biologists agree that exosomes contain proteins, lipids, and other molecules that result from cell metabolism. Some believe they also contain DNA and RNA, but not everyone is convinced. “It’s just very difficult to prove or disprove,” says Edgar.
That’s partly because exosomes are so small—only about 70 nanometers wide, around one-hundredth the size of a red blood cell. While the first images of them were published in the 1970s, we still don’t even know for sure what they look like; Raghu Kalluri at MD Anderson Cancer Center in Houston and his colleagues are studying the shape of exosomes to figure out if they are round, oval, or rod-like, for example.