Are your stem cells fresh or frozen?

Your dose is then prepared for your scheduled treatment date and handled under controlled conditions until the moment of application. Cryopreservation is the standard way to keep cell products stable, safe and ready for use, and it allows us to deliver cells with viability greater than 97%.

The words "fresh" and "frozen" can sound like a matter of quality, as if fresh were always better. In cell therapy, the reality is different. Controlled cryopreservation is the method used worldwide to store cells safely, from cord blood banks to clinical trials. This guide explains what cryopreservation is, why it is used, how cells are prepared for your treatment and what this means for you.

What is cryopreservation?

Cryopreservation is the process of cooling cells to very low temperatures to stop their biological activity, so they can be stored without deteriorating. It is not the same as putting something in a household freezer. The process is carefully controlled:

1. Protective solution: the cells are suspended in a solution with a cryoprotectant, a substance that protects them from ice crystals that could damage their membranes.
2. Controlled-rate cooling: the temperature is lowered gradually, at a specific rate, to protect the cells during freezing.
3. Storage at very low temperatures: the cells are stored at extremely low temperatures, often in the vapor phase of liquid nitrogen, where biological activity is practically stopped.
4. Controlled thawing and preparation: when the cells are needed, they are thawed following a validated protocol and prepared in the dose and format needed for the treatment.

At these temperatures, cells can remain stable for long periods while keeping their characteristics.

Why cryopreservation is used in cell therapy

Cryopreservation is not a shortcut. It is what makes a safe, consistent cell product possible:

• Complete quality testing: some quality tests, such as sterility tests, take days to complete. Cryopreservation allows the laboratory to hold the cells until all tests are finished and the batch is approved for release.
• Consistency: a batch can be produced, tested and characterized as a whole, so every dose from that batch meets the same specifications.
• Availability on your date: cells can be ready for your scheduled treatment, instead of depending on a production cycle that must match your trip exactly.
• Donor screening: cryopreservation allows time for complete donor screening and testing before the cells are used.

A concise review in Stem Cells Translational Medicine on the clinical development of mesenchymal stromal cells discusses how production and storage conditions affect product consistency, and why standardized handling is one of the key challenges in the field. Cryopreservation under validated protocols is one of the main tools used to address it.

Is cryopreservation common?

Yes. Some examples:

• Cord blood banks around the world store cord blood cells cryopreserved for years before they are used in transplants.
• Bone marrow and blood stem cell transplants frequently use cryopreserved cells.
• Clinical trials of mesenchymal stem cells often use cryopreserved products, because they allow standardized doses across many patients and sites.
• Fertility medicine uses cryopreservation for eggs, sperm and embryos.

The two large meta-analyses on the safety of intravascular mesenchymal stromal cells, published in EClinicalMedicine in 2020 and in Stem Cells Translational Medicine in 2026, included trials that used a wide range of products, many of them cryopreserved, and reported that this type of administration continues to appear safe.

Does freezing affect the cells?

Freezing without proper protection can damage cells, which is why cryopreservation follows strict protocols. When it is done correctly:

• The cells keep their identity. Thawed MSCs keep the characteristics defined by the International Society for Cell and Gene Therapy (ISCT): adherence to plastic in culture, expression of the markers CD73, CD90 and CD105, absence of blood cell markers, and the ability to differentiate into bone, cartilage and fat cells.
• The cells keep high viability. In the information we share with our patients, our cells are described as having viability greater than 97% through exclusive cryopreservation protocols.
• The cells keep their signaling activity. MSCs work largely through the growth factors, cytokines and extracellular vesicles they release, which help regulate inflammation and support tissue repair.

How your dose is prepared

Before your treatment:

1. Your plan is defined: the doctor reviews your case and prescribes a dose and a route, such as 20 to 40 million cells per area for a joint, or 100 to 200 million cells for an IV infusion.
2. The dose is prepared for your date: the laboratory prepares the cells in the prescribed dose for your scheduled treatment day.
3. Quality checks: the cells are checked before release, including viability.
4. Controlled handling: the cells are handled under controlled temperature and timing until the application.
5. Application: the medical team applies the cells by direct injection, IV infusion or both, according to your plan.

This is one reason why your arrival day and your treatment day are organized carefully. The schedule, with laboratory tests and your evaluation on arrival and the treatment the following day, allows the team to confirm your plan and coordinate the preparation of your cells.

What about "fresh" cells?

Some clinics advertise "fresh" cells. The term is not standardized and can mean different things, from cells that were never frozen to cells that were recently thawed. A product that is never frozen must be applied shortly after production, which can limit the time available for complete quality testing. What matters most for patients is not the word "fresh" or "frozen," but three questions:

• Where do the cells come from?
• How are they produced and tested?
• How many living cells will I receive?

At Stem Cell Mexico, the answers are: Wharton's jelly from donated umbilical cords, produced and tested under quality standards, and a defined dose of cells with high viability.

What happens on treatment day

On the morning of your treatment, the team confirms your plan and your laboratory results from the previous day. The cells prepared for you are applied according to your plan: under ultrasound guidance for joints, with fluoroscopy for the spine, or by IV infusion with a calm, monitored drip. After the procedure, you stay a night at our facilities under nursing and medical monitoring, and you receive written aftercare instructions before discharge.

Why this question matters

The International Society for Stem Cell Research (ISSCR) encourages patients to ask where cells come from, how they are processed and how their quality is checked before any treatment. Asking whether cells are fresh or frozen is a good starting point, and it is a question we are always glad to answer. It naturally leads to the more important questions about source, testing and dose that any responsible provider should be able to answer clearly.

Laboratory standards

In the information we share with our patients, our partner laboratories are described as operating under Good Manufacturing Practice (GMP) and Good Laboratory Practice (GLP) standards, with ISO 9001 quality management systems. Cells undergo screening, testing and quality-control processes before being released for clinical use.

Common questions

Are the cells stored for a long time? Cryopreserved cells can be stored for long periods under the right conditions. Your dose is prepared for your scheduled date.

Will thawed cells work as well as never-frozen cells? When cryopreservation and thawing follow validated protocols, the cells keep their identity, high viability and signaling activity.

Is the cryoprotectant injected into my body? Laboratories prepare the cells after thawing following their protocols. You can ask about the preparation process during your consultation.

Do frozen cells cause more reactions? The safety meta-analyses of intravascular MSCs included many cryopreserved products and reported that this administration continues to appear safe, with transient fever as the most frequently associated event.

Can I choose fresh cells instead? Our treatments use cells preserved and prepared under our partner laboratory's protocols, which is how we ensure consistent quality.

Questions to ask during your consultation

• What dose will I receive, and by which route?
• How are the cells prepared for my treatment date?
• What quality checks are done before release?
• What should I do before and after treatment to support the results?

Bottom line

Our Wharton's jelly mesenchymal stem cells are preserved through a controlled cryopreservation process at our partner laboratory and prepared for your scheduled treatment date. Cryopreservation is the standard way to store cell products safely and consistently, and it allows complete quality testing before release. Our cells are delivered with viability greater than 97%. Results vary between patients and depend on many factors beyond how the cells are stored. A medical evaluation can help determine whether this type of regenerative treatment is appropriate for your condition, goals and medical history.