We know that exosomes are tiny particles that break out of cells, and that their contents can vary greatly depending on the source of the cell (some popular options include human umbilical cord, salmon testes, 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—that content might be.

The world of exosome treatments has been likened to a “Wild West” by some researchers. No rigorous studies have been done, so we don’t know how safe it is to spray or inject these mysterious little 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 use in Japan or South Koreatwo 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. “The risks are usually downplayed and the benefits are usually exaggerated.”

That hasn’t stopped customers from flocking to the growing number of beauty salons, stem cell clinics and medical spas offering exosome treatments in hopes of a miracle cure. Global Exosome Skin Care Products Market was valued at $256 million in 2023 and is projected to grow to $674 million over the next six years.

Mystery spots

Technically called vesicles, exosomes are manufactured inside cells before being released. They have long been mysterious. The term “exosome” was introduced in the 1980s. Before that, tiny particles thought to be exosomes were described as “platelet dust” or “matrix vesicles”.

At first, scientists assumed that exosomes functioned as garbage bags, carrying waste out of the cell. But research in 1996 suggested that exosomes might also function to help cells communicate by providing signals to each other. If a cell is dying, for example, it could send a signal to neighboring cells, giving them a chance to produce more protective substances to save themselves from the same fate. Cancer cells, on the other hand, could use exosomes to send signals that co-opt other cells to support a tumor’s growth. However, it is not fully understood what signals are actually being sent.

Another major mystery is what exactly is inside the exosomes. “It depends on 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 cellular metabolism. Some believe they also contain DNA and RNA, but not everyone is convinced. “It’s just very hard to prove or disprove,” says Edgar.

That’s partly because exosomes are so small — only about 70 nanometers wide, about one-hundredth the size of a red blood cell. While the first pictures of them were published in the 1970swe still don’t know for sure what it looks like; Raghu Kalluri of MD Anderson Cancer Center in Houston and colleagues study the shape of exosomes to figure out whether they are round, oval or rod-like, for example.