What Is the MSC Secretome?
Mesenchymal stromal cells (MSCs) are the "signaling" cells found in bone marrow, fat, and perinatal tissue. For years they were called "stem cells," but research has shown they rarely turn into new tissue themselves. Instead, they work mainly by releasing a mix of biologically active molecules - growth factors, cytokines, and tiny membrane-bound packages called extracellular vesicles (including exosomes).
That collection of secreted signals is called the secretome. Because the secretome does much of the actual work, MSCs are sometimes described as "medicinal signaling cells." Secretome-based therapy aims to deliver those repair signals directly, without transplanting living cells - a "cell-free" approach.
How Is It Thought to Work?
The secretome is studied for its ability to calm inflammation and support the local environment for healing. Proposed effects include:
- Shifting an inflamed, painful joint toward a more anti-inflammatory state
- Signaling nearby resident cells to support cartilage and soft-tissue maintenance
- Delivering growth factors and micro-RNA-carrying vesicles that coordinate local repair
Because it contains no living cells, a secretome preparation avoids concerns tied to cell survival, immune rejection, or uncontrolled cell growth. It is important to understand that this is a mechanism supported by laboratory and animal studies - it is not proof of a cure.
Secretome vs. Stem Cells vs. Exosomes
These terms overlap and are often confused. Stem cell (MSC) therapy delivers the cells themselves. The secretome is everything those cells secrete. Exosomes are one specific component of the secretome - nanoscale vesicles (30 - 150 nm) that carry signaling cargo. In short: exosomes are part of the secretome, and the secretome is what MSCs produce.
What Is It Being Studied For?
Most orthopedic interest centers on knee osteoarthritis, cartilage injury, and tendon healing. Preclinical models show reductions in cartilage-degrading enzymes and inflammatory signals, and early-phase human safety studies have been encouraging. However, the strongest human evidence remains small and early, and results have not consistently shown structural cartilage regrowth.
How Is It Given?
When offered, a secretome preparation is delivered as an in-office injection, typically guided by ultrasound to place it precisely in the target joint. The procedure is outpatient and takes a short time.
What to Expect and Possible Risks
Mild soreness or swelling at the injection site is the most commonly reported effect and usually settles within a few days. As with any injection, there is a low risk of infection or bleeding. There is no guaranteed result, and outcomes are still being studied.
Evidence and Regulatory Status
Secretome and exosome-based therapies are considered investigational by the FDA and are not FDA-approved to treat arthritis, tendon injuries, or joint degeneration outside of a formal clinical trial. Dr. Rahman's approach is to discuss what the current evidence does and does not show, so patients can make an informed decision.
FAQ
Is the MSC secretome the same as stem cells? No. Stem cell therapy delivers living cells. The secretome is the set of signals those cells release, given without the cells themselves. It is a "cell-free" approach.
Are secretome or exosome injections FDA-approved? No. In orthopedics they are considered investigational and are not FDA-approved for any joint or tendon condition outside of a clinical trial.
What conditions is it being studied for? Primarily knee osteoarthritis, cartilage injury, and tendon problems. Early human data focus on short-term safety and symptom relief, not proven cartilage regrowth.
Does it hurt, and what is recovery like? It is an outpatient injection. Most people have only mild soreness or swelling for a few days and return to normal activity quickly.
Physician-Authored Review. The science on this page is drawn from Dr. Rahman's peer-reviewed review, Umbilical Cord - Derived Biologics in Orthopaedics: Wharton's Jelly, Mesenchymal Stromal Cells, and Extracellular Vesicles (Journal of Orthopaedic Experience & Innovation, 2026).
FDA Disclaimer: MSC secretome and exosome therapies are considered investigational and have not been evaluated or approved by the U.S. Food and Drug Administration to diagnose, treat, cure, or prevent any disease. This content is for educational purposes only and does not replace professional medical advice.