What are Muse cells?

The short answer

Muse cells (multilineage-differentiating stress-enduring cells) are a small population of stem-like cells first described in 2010 by Professor Mari Dezawa’s team at Tohoku University in Japan. They are identified by a surface marker called SSEA-3 and are found in bone marrow, peripheral blood and the connective tissue of many organs. In laboratory cultures of mesenchymal stromal cells (MSCs), they make up only a small fraction, often cited at around 1–3%.

Why researchers are interested

• Stress tolerance. The name comes from their ability to survive harsh laboratory stress that kills many other cells.
• Homing to damage. In animal studies, Muse cells given intravenously tended to travel to injured tissue, guided by signals the damaged tissue releases.
• Multiple cell types. In laboratory and animal experiments they have shown the ability to become cells of different tissue types.
• No tumors in studies so far. Unlike some pluripotent stem cells, they have not formed tumors in the animal studies published to date.
• Donor cells without matching. Small human studies used donor cells without HLA tissue matching and without long-term immunosuppression.

What human studies have shown so far

A donor Muse cell product called CL2020 has been tested in small clinical trials in Japan, including:

• Heart attack (acute myocardial infarction): a first-in-human study in 3 patients.
• Epidermolysis bullosa (a severe skin-blistering disease): a study in 5 adult patients.
• Ischemic stroke: a small randomized, placebo-controlled study.
• ALS: an open-label phase II study in 5 patients at Okayama University, reported in 2023.

These studies reported no serious treatment-related safety problems, and some reported encouraging changes. They were also very small, and most had no control group. The ALS researchers themselves said a larger, double-blind study with longer follow-up is needed before the treatment could be proposed for clinical use.

What that means for patients

Based on the published sources we reviewed, Muse cell therapy is investigational. We are not aware of any regulator, including the U.S. FDA, that has approved a Muse cell product for any condition. Check with the regulator in the country where care would take place, because status can change.

Some clinics now advertise “Muse cell therapy” for long lists of unrelated conditions. Muse cells are rare and must be isolated and verified. A product can be called “Muse” without containing a meaningful number of verified Muse cells.