Mesenchymal stem cells (MSCs) are multipotent cells that can turn into bone, cartilage, and fat cells, and that release molecules which calm inflammation and adjust the immune response. They come from bone marrow, fat, and umbilical cord tissue. MSCs are the cells behind most joint and pain injections sold today, even though those uses are not FDA approved.
This explainer covers what MSCs are, where they come from, why clinics use them, and what the evidence does and does not show. It does not claim MSCs repair, regrow, or cure anything. It reports the science and the regulatory status as they stand in 2026.
What MSCs are
Mesenchymal stem cells are adult stem cells with two defining traits. First, they are multipotent, meaning they can become a limited set of cell types: bone, cartilage, and fat. Second, they are strong signalers.
That second trait now drives most research interest. MSCs release anti-inflammatory and immune-regulating molecules, which is why early trials tested them in graft-versus-host disease and autoimmune conditions. As our how it works guide explains, this signaling role matters more than direct tissue-building.
MSCs are not embryonic stem cells and cannot become any cell in the body. That limit is important when a clinic implies MSCs can rebuild a whole joint.
Where MSCs come from
MSCs come from several tissues, and the source changes their behavior, cost, and risk. Three sources dominate clinical use.
| Source | Key traits | Trade-off |
|---|---|---|
| Bone marrow | Most studied; your own cells | Painful harvest; quality declines with age |
| Adipose (fat) | Abundant; easy to collect via liposuction | Less standardized; processing varies |
| Umbilical cord | Young cells; multiply fast; low aging markers | Donor tissue; small infection/immune risk |
Smaller amounts of MSCs also exist in dental pulp, placenta, and amniotic tissue. Research summarized on PubMed finds umbilical cord MSCs proliferate fastest and show the fewest senescence markers, while bone marrow MSCs have the deepest track record.
Autologous vs donor MSCs
The source also decides whether the cells are yours or a donor’s. Bone marrow and fat MSCs are autologous, taken from your own body the same day. Umbilical cord MSCs are allogeneic, from a donor.
Autologous cells carry almost no rejection risk. Donor cells are marketed as “younger and stronger,” but potency claims do not remove the donor-related infection and immune questions. Neither source is proven better for joints.
Why clinics use MSCs
Clinics use MSCs mainly for their anti-inflammatory signaling, not because the cells become new tissue. The pitch has quietly shifted over the years, and knowing the current version helps you read a claim.
The older pitch was that MSCs “turn into” fresh cartilage. The newer, better-supported view is that MSCs briefly signal to nearby cells and calm inflammation, then clear from the body. That is a weaker, more temporary mechanism than regrowth.
A common failure mode is a clinic page that describes MSCs as “regenerative,” then lets the reader assume that means cartilage regrowth. Regenerative is a research label about signaling potential, not a promise your knee will rebuild.
What the evidence shows
The evidence for MSCs is a split picture: safety looks reasonable, but proof of benefit is thin outside a few approved uses. This is the 2026 status.
- Safety in early-phase trials has generally looked acceptable, with mostly mild, short-term side effects.
- Efficacy is the open question. A Cochrane review of stem cell injections for knee osteoarthritis rated the evidence low-certainty and the benefit uncertain.
- Scale of research. More than 1,000 MSC clinical trials have been registered worldwide, yet only about a dozen MSC therapies are approved anywhere, which shows how often promising trials do not translate into approved products.
So MSCs are heavily studied and rarely approved. That gap is the key fact for any patient weighing a joint injection.
FDA status of MSC treatments
Only one MSC drug is FDA approved, and it is not for joints. In December 2024, the FDA approved Ryoncil (remestemcel-L), the first MSC therapy, for steroid-refractory acute graft-versus-host disease in children.
Every other MSC use sold in US clinics, including all knee, hip, back, and anti-aging injections, is unapproved. The FDA has warned that many products marketed as MSC injections contain few or no living stem cells. Our FDA status page covers what approval means here.
MSCs vs exosomes and PRP
MSCs are often confused with two related products clinics also sell: exosomes and PRP. Knowing the difference helps you understand what you are actually buying.
| Product | What it is | Contains living cells? |
|---|---|---|
| MSCs | The stem cells themselves | Yes, when the product is genuine |
| Exosomes | Tiny signaling packets released by cells | No |
| PRP | Concentrated platelets from your own blood | No stem cells |
Exosomes and PRP skip the cells and use their signals or growth factors instead. That is telling: if MSCs mainly work by signaling, some clinics reason, why not sell the signals directly? None of these are FDA approved for joints. Our PRP and exosomes hub and PRP vs stem cell guide compare them in detail.
What this means before you pay
Knowing what MSCs are should sharpen the questions you ask a clinic. Ask which source the cells come from, whether they are living, and what published trial supports that exact use for your condition.
Then set expectations to match the evidence: possible short-term, anti-inflammatory relief for some people, not proven regrowth. Weigh that against a cheaper, proven option, and check the real cost of the full recommended course.
The bottom line
Mesenchymal stem cells are multipotent, strongly signaling cells drawn from bone marrow, fat, or umbilical cord tissue, and they power most joint injections on the market. Their likely role is short-term anti-inflammatory signaling, not cartilage regrowth, and only one MSC drug is FDA approved, for a childhood condition. Treat MSC joint therapy as experimental, check the source and the evidence, and read “regenerative” as a research term, not a cure.
Frequently asked questions
What are mesenchymal stem cells?
Mesenchymal stem cells (MSCs) are multipotent cells that can develop into bone, cartilage, and fat cells, and that release anti-inflammatory and immune-signaling molecules. They come from bone marrow, fat, and umbilical cord tissue. Clinics use them for joints and pain, though most such uses are not FDA approved.
Where do mesenchymal stem cells come from?
MSCs come mainly from bone marrow, adipose (fat) tissue, and umbilical cord tissue, with smaller amounts in dental pulp and placenta. Bone marrow MSCs are the most studied. Umbilical cord MSCs are younger and multiply faster but come from a donor.
Are mesenchymal stem cell treatments FDA approved?
Only one MSC drug is FDA approved: Ryoncil (remestemcel-L), cleared in December 2024 for a graft-versus-host condition in children. No MSC product is approved for knees, arthritis, back pain, or anti-aging. Those uses are experimental.
Why do clinics use mesenchymal stem cells?
Clinics use MSCs mainly for their anti-inflammatory and immune-signaling effects, not because they rebuild tissue. Research suggests MSCs work by signaling to nearby cells rather than becoming new cartilage. The benefit for joints and pain is still unproven in strong trials.
What is the difference between MSCs from bone marrow and umbilical cord?
Bone marrow MSCs are your own cells, most studied, but decline with age. Umbilical cord MSCs come from donated tissue, multiply faster, and show fewer aging markers, but they carry a small donor-related infection and immune risk. Neither is proven superior for joints.
Do mesenchymal stem cells regrow cartilage?
No strong evidence shows MSC injections regrow cartilage in patients. Most injected cells clear within days and act by signaling, not by becoming new tissue. Claims of cartilage regrowth go beyond what current trials support.
Medical disclaimer. Medical Frontier is an independent educational resource. This page is for general information only and is not medical advice, diagnosis, or treatment, and does not create a doctor–patient relationship. Most regenerative therapies discussed here are not FDA-approved for the uses described and may be offered under limited exemptions or in clinical trials only. Always consult a licensed physician before making any treatment decision.