By Evan Chait, licensed Physical Therapist and Acupuncturist
Quick answer (TL;DR) SSEA-3 (Stage-Specific Embryonic Antigen 3) is a sugar-based molecule on the surface of a cell, and it is the main marker scientists use to identify and isolate MUSE cells. Researchers typically pair it with a second marker such as CD105 to pick MUSE cells out of a mixed population. SSEA-3 is a useful tag, but it is not a complete proof of identity or quality, so patients should know what else a stem cell clinic tests.
When you read about MUSE cells, one odd-looking term appears again and again: SSEA-3. It sounds like a lab code, yet it explains how researchers tell this rare cell apart from millions of ordinary ones.
If you are considering stem cell treatment, understanding this one marker gives you a real advantage. It helps you see how MUSE cells are found, why they are hard to prepare, and what questions to ask before trusting any claim. If you are new to the topic, our guide on what MUSE cells are is a good place to start.
What Is SSEA-3?
SSEA-3 stands for Stage-Specific Embryonic Antigen 3. It is a type of molecule called a glycosphingolipid, which is a fatty molecule with a chain of sugars attached. It sits on the outer surface of the cell membrane, a bit like a name tag pinned to a jacket.
SSEA-3 was first associated with early embryonic development, and it is a well-known marker of undifferentiated human embryonic stem cells. That is one reason it caught researchers’ attention when it showed up on a small group of adult cells.
Two plain-language points help here:
- A marker is a label, not a function. Scientists use markers to sort and identify cells, the same way a barcode identifies a product.
- SSEA-3 sits on the outside. Because it is on the surface, researchers can attach a fluorescent or magnetic antibody to it and use that attachment to pick cells out of a crowd.
Why Do Stem Cell Markers Matter?
A bone marrow sample or a tissue sample contains a huge mix of cell types. Most of them are not stem cells, and only a tiny share are MUSE cells. Without a reliable marker, finding those few would be like searching for one person in a stadium with no way to describe them.
A marker solves that problem in three ways:
- Identification. It lets researchers confirm they are looking at the cell type they think they are.
- Isolation. It lets them separate target cells from everything else.
- Standardization. It gives different labs a shared way to describe and compare their work.
For you as a patient, this matters because quality in cell therapy begins with knowing exactly what is in the vial.
How SSEA-3 Identifies MUSE Cells
Professor Mari Dezawa’s team at Tohoku University described MUSE cells in 2010. In their original PNAS paper on PubMed Central, they reported that these cells can be efficiently isolated as cells positive for both SSEA-3 and CD105.
Here is what each marker tells us:
- SSEA-3 points to the pluripotency-associated side of the cell, the feature that sets MUSE cells apart from ordinary mesenchymal cells.
- CD105 is a marker commonly found on mesenchymal stem cells, so it confirms the cell belongs to the mesenchymal family.
A cell carrying both is treated as a MUSE cell in bone marrow and similar tissues. Researchers write this as SSEA-3 positive and CD105 positive, often shortened to SSEA-3(+)/CD105(+).
The second marker changes depending on where the cells are collected. In blood, for example, research from the Dezawa group identified SSEA-3 positive cells that also carry CD45, a marker found on blood cells. In that peripheral blood study, these cells made up only about 0.04 percent of the mononuclear cells, expressed pluripotency markers, and moved toward the injury signal S1P in lab tests. They were similar to tissue MUSE cells, though not identical in every property.
How Are SSEA-3 Cells Collected?
Once a marker is on the surface, researchers can use it as a handle. The two most common approaches are:
Flow cytometry cell sorting (FACS). Cells are labeled with a fluorescent antibody that binds SSEA-3. A machine then reads each cell one at a time and sorts the glowing ones into a separate tube.
Magnetic-activated cell sorting (MACS). Cells are labeled with antibody-coated magnetic beads, and a magnet pulls the SSEA-3 positive cells away from the rest. An independent research group in Italy used this method to collect MUSE cells from bone marrow mesenchymal stem cells.
There is also a second route that uses the “stress enduring” trait. Because MUSE cells survive harsh conditions that kill many other cells, researchers can expose a population to severe stress first and then sort. One laboratory study on umbilical cord stem cells reported that SSEA-3 positive cells rose from roughly 3 percent in the native culture to over 50 percent after a severe stress protocol. That is a single laboratory report, but it shows why preparation method matters so much.
SSEA-3 Is More Than a Label
For years SSEA-3 was treated as nothing more than a tag. A 2023 study in the journal Cell Proliferation, from a research group at the University of Campania in Italy, suggests it may do more.
The researchers found that SSEA-3 may act as a co-receptor for FGF2, a growth factor important to MUSE cell biology. When they blocked SSEA-3, the cells’ ability to produce many cell types dropped, and some clones lost that ability entirely. You can read the details in the study on PubMed Central.
The authors describe their work as one of the first pieces of evidence that this kind of surface molecule helps govern stem cell behavior. It is early laboratory research, so it should be read as an interesting lead and not as a clinical result.
The Limits: Why SSEA-3 Alone Is Not Enough
Here is where honesty matters most. A marker is useful, but it has limits.
- SSEA-3 is not unique to MUSE cells. It also appears on embryonic stem cells, which is why researchers pair it with a second marker and further tests.
- A positive result does not prove function. A cell can carry the marker without behaving the way MUSE cells are described to behave.
- Purity varies. A preparation can be “enriched” for SSEA-3 positive cells without being nearly pure. Reported percentages differ a great deal between methods and tissue sources.
- Identity takes several checks. In the research literature, MUSE cells are defined by a combination of features: the marker, expression of pluripotency genes, cluster formation in suspension culture, the ability to form cells of all three germ layers, and low growth activity.
In short, SSEA-3 is the front door to identifying a MUSE cell, but a careful lab walks through the rest of the house too.
What This Means for Patients
You do not need to become a lab scientist. But you can use this knowledge to ask sharper questions.
When a provider says they offer MUSE stem cells, consider asking:
- How are the cells identified, and is SSEA-3 testing part of that process?
- What share of the final product is SSEA-3 positive, and how is that measured?
- Where do the cells come from, and who prepares and tests them?
- What quality and safety testing is done before a product is released?
- Can you share published research for my specific condition, and does it involve humans or animals?
A transparent provider will welcome these questions. Vague answers are a warning sign.
Also keep the bigger picture in mind. MUSE cell therapy is not FDA-approved as a standard treatment for any specific condition, and the research is still developing. The FDA’s consumer page, Important Patient and Consumer Information About Regenerative Medicine Therapies, is worth reading before any decision.
To see how SSEA-3 fits into the wider comparison, read our guide to MUSE cells vs regular stem cells.
Frequently Asked Questions
What does SSEA-3 stand for?
SSEA-3 stands for Stage-Specific Embryonic Antigen 3. It is a sugar-based molecule on the cell surface that researchers use as an identification tag for MUSE cells.
Does SSEA-3 mean MUSE cells come from embryos?
No. SSEA-3 was first linked to embryonic cells, but MUSE cells are adult cells collected from tissues such as bone marrow, fat, and skin. They carry the marker without being taken from an embryo.
Can a clinic confirm that my treatment contains MUSE cells?
A qualified provider should be able to explain how the cells are identified and what testing supports that. Ask whether SSEA-3 and a second marker such as CD105 are used, and ask for the measured percentage.
Is a higher SSEA-3 percentage always better?
Not necessarily. A higher percentage can mean a more enriched sample, but the percentage alone does not prove safety, function, or benefit. Quality depends on how the cells are collected, prepared, and tested.
Are all stem cell clinics testing for SSEA-3?
No. Standard mesenchymal stem cell preparations are usually described with general mesenchymal markers, and SSEA-3 testing is specific to MUSE cell work. If a clinic markets MUSE cells, it is reasonable to ask how they verify them.
Does SSEA-3 make MUSE cells safe?
No. SSEA-3 is an identification marker, not a safety guarantee. Published studies describe MUSE cells as non-tumorigenic, but long-term human safety data are still limited.
Talk With Our Team
Understanding the science helps you make a calmer, better-informed choice. If you want an honest conversation about Dezawa MUSE cells and what may or may not fit your situation, our team is happy to help. You can also explore our wider stem cell therapy options, or Inquire About MUSE Cell Therapy to start a conversation. Evan Chait works with patients across the United States.
MUSE cell therapy is an emerging area of regenerative medicine and is not FDA-approved as a standard treatment for any specific condition. Clinical research is ongoing. This content is for educational purposes only and is not medical advice. Evan Chait is a licensed Physical Therapist and Acupuncturist, not a medical doctor (MD). Always consult a qualified healthcare professional before pursuing any cellular therapy. Individual results may vary.