What is the viability of the stem cells at the time of application?

From release to application, the cells are handled under controlled conditions of temperature and time, so that the dose your doctor prescribes reaches you in optimal condition.

Viability is one of the most common questions patients ask, and it is a good one. A dose of 100 million cells only works as a dose of 100 million cells if those cells are alive. This guide explains what viability means, how it is measured, what can affect it and how we protect it from the laboratory to the moment of application.

What does "viability" mean?

In cell therapy, viability is the proportion of living cells in a sample. If a vial contains 100 million cells and 97 million are alive, the viability is 97%.

Viability matters because mesenchymal stem cells (MSCs) work through their activity. Living MSCs release growth factors, cytokines and extracellular vesicles that help regulate inflammation and support tissue repair. Dead or damaged cells cannot do this, and a high proportion of dead cells can also trigger a local inflammatory response. That is why viability is one of the core quality checks for any cell product.

How viability is measured

Laboratories use standardized methods to measure viability. The most common are:

• Dye exclusion tests: a dye, such as trypan blue, is mixed with a sample of cells. Living cells have intact membranes that keep the dye out, while dead cells absorb it and appear colored under the microscope. The ratio of uncolored to total cells gives the viability.
• Fluorescent viability stains and flow cytometry: fluorescent dyes bind to the DNA of cells with damaged membranes. A flow cytometer, an instrument that analyzes thousands of cells per second, counts living and dead cells with high precision.
• Automated cell counters: many laboratories use automated instruments that combine imaging and staining to count cells and calculate viability in a standardized way.

These methods are routine in cell therapy laboratories, and viability is usually measured together with the total cell count, so the laboratory can confirm that the dose contains the number of living cells prescribed.

Our viability figures

In the information we share with our patients:

• Our cells are described as having viability greater than 97% when released by the laboratory.
• Our cells are grown under hypoxic conditions, which support viability of up to 98%.

These figures are well above the minimum thresholds commonly used for cell therapy products, which in many settings are around 70%.

Why hypoxic conditions matter

Inside the body, mesenchymal stem cells live in tissues with relatively low oxygen levels, much lower than the oxygen in the air. When cells are grown in standard laboratory conditions, they are exposed to more oxygen than they are used to. Growing the cells under hypoxic, or low-oxygen, conditions resembles their natural environment more closely. Laboratories use this approach to support cell health, survival and function, and in our proposals we describe it as one of the reasons for the high viability of our cells.

Viability and cell identity are different checks

Viability tells you how many cells are alive. Identity tells you what kind of cells they are. The International Society for Cell and Gene Therapy (ISCT) defined minimal criteria for mesenchymal stromal cells in 2006: the cells must adhere to plastic in culture, express the surface markers CD73, CD90 and CD105, lack blood cell markers such as CD34, CD45 and HLA-DR, and be able to differentiate into bone, cartilage and fat cells in the laboratory. A quality cell product needs both: the right cells, and cells that are alive.

What can affect viability

Several factors can reduce the viability of a cell product between production and application:

• Temperature: cells are sensitive to heat and to uncontrolled temperature changes.
• Time: cells outside optimal storage conditions gradually lose viability, so the time between preparation and application matters.
• Handling: rough handling, inappropriate needles or high injection pressure can damage cells.
• Storage method: cells must be stored and prepared following validated protocols.
• Some medications: laboratory research has shown that some corticosteroids can be toxic to mesenchymal stem cells. This is one reason why your doctor may ask about recent steroid injections in the treated area and may recommend avoiding them around the time of your treatment.

A concise review in Stem Cells Translational Medicine on the clinical development of MSCs highlights that product consistency, including how cells are handled before application, is one of the key factors in cell therapy. Our protocols are designed with this in mind.

How we protect viability

From the laboratory to your treatment:

• Production under quality standards: our partner laboratories are described as operating under Good Manufacturing Practice (GMP) and Good Laboratory Practice (GLP) standards, with ISO 9001 quality management systems.
• Quality control before release: each batch is checked for identity, sterility and viability before it is released for clinical use.
• Controlled handling: the cells are kept under controlled temperature and handled according to established protocols until the moment of application.
• Scheduling around your treatment: your dose is prepared for your scheduled treatment date, and the timing of your arrival day and treatment day is organized so that the cells are applied in optimal condition.
• Gentle application technique: the medical team uses appropriate needles and controlled injection speed, and image guidance in targeted applications.

Does viability guarantee results?

High viability is a basic condition for a quality product, but it is not the only factor that influences results. The response to treatment also depends on:

• Your diagnosis and the stage of your condition.
• Your age, general health and lifestyle.
• The route of application and the dose.
• Your recovery and how you follow aftercare instructions.

This is why results vary from patient to patient, even when the cells meet the same quality standards. No figure can guarantee a specific outcome, but high viability helps ensure that you receive the full prescribed dose of living cells.

Is my individual case taken into account?

Yes. Your treatment plan, including the number of cells and the route, is defined by the doctor based on your in-person evaluation, your imaging and your laboratory results. In the explanations we send to patients, we describe this as a personalized approach that tailors the protocol to each patient's needs while ensuring the quality and viability of the cells used.

Common questions

What does 97% viability mean in practice? It means that 97 out of every 100 cells in the dose are alive and intact at release.

Do the cells lose viability after they are applied? Once in the body, cells interact with the surrounding tissue, and their activity over time depends on the environment of the treated area. Researchers describe the benefit of MSCs as coming largely from the signals they release, which influence the tissue even after the cells themselves are no longer present.

Should I avoid anything that could affect the cells? Follow your doctor's instructions. These often include avoiding anti-inflammatory drugs and corticosteroid injections in the treated area for a period of time before and after treatment, staying hydrated and avoiding alcohol and smoking around your treatment days.

Is viability the same for joint and IV applications? The cells come from the same source and go through the same quality checks. The preparation is adapted to the route of application.

Can I ask about quality control during my consultation? Yes. You can discuss the quality checks and the handling of your cells with the doctor and the stem cell specialist during your evaluation.

Questions to ask during your consultation

• How many cells will I receive, and by which route?
• How is the dose prepared for my treatment date?
• Should I pause any medication or avoid any injection before my treatment?
• What aftercare steps help me get the most from my treatment?

Why this question matters

The International Society for Stem Cell Research (ISSCR) encourages patients to ask how a cell product is prepared and how its quality is checked. Viability is one of the clearest, most concrete quality indicators of a cell product, and it is reasonable to ask about it before any treatment.

Bottom line

Viability is the percentage of living, intact cells in a dose. The Wharton's jelly mesenchymal stem cells we use are released with viability greater than 97%, grown under hypoxic conditions that support viability of up to 98%, and handled under controlled conditions until the moment of application. High viability helps ensure that you receive the full dose your doctor prescribes, although results vary between patients and depend on many factors. A medical evaluation can help determine whether this type of regenerative treatment is appropriate for your condition, goals and medical history.