When searching for information about cultured mesenchymal cells (CMC), it is common to encounter a mix of terms that sound equivalent: cellular concentrate, stromal fraction, platelet-rich plasma, progenitor cell therapy. They all share a similar vocabulary. None of them are the same.
One of the most determining differences between a procedure and a regulated medicinal product does not lie in the name of the product or in the application technique. It lies in a specific, measurable, and certifiable parameter: the cellular dose. How many cells are administered, with what viability, with what characterization, under what manufacturing conditions, and with what documentation to certify it.
This parameter is not a minor technical detail. It is, in practice, the line that separates an advanced therapy medicinal product manufactured under pharmaceutical regulations from a procedure that uses the same vocabulary without the same regulatory framework, without the same manufacturing process, and without the same clinical evidence base.
Understanding what the cellular dose implies in the context of cultured mesenchymal stem cells allows asking the right questions before any clinical decision. And, frequently, also obtaining answers that many centers cannot provide.
Why does the cellular dose define the product category?
In pharmacology, the dose is one of the essential parameters of any medicinal product. It determines the amount of active substance administered, ensures reproducibility across patients, and allows evaluation of the dose-response relationship.
In an advanced therapy medicinal product with cultured mesenchymal cells (CMC), the active substance is the cells themselves. Therefore, the cellular dose is the number of viable mesenchymal cells contained in the medicinal product at the time of application.
A practice cannot be considered a medicinal product if it does not define, control, and certify its dose. Without a verified dose, there is no medicinal product. There is a procedure.
This distinction is not semantic: it is regulatory, scientific, and ultimately, clinical.
At ITRT, the medicinal product can be formulated from autologous CMC — obtained from the patient — or from allogeneic CMC, derived from a previously characterized healthy donor. The AEMPS recognizes equivalent efficacy between both modalities. The process of culture, expansion, certification, and individual authorization is identical in both cases; only the origin of the starting material differs.
How the cellular dose is defined and certified in cultured mesenchymal cells
Mesenchymal stem cells represent approximately one in every 10,000 to 100,000 mononuclear cells present in bone marrow. To obtain a therapeutic dose, a cell culture and expansion process under controlled conditions is essential.
The process applied by ITRT includes the following phases:
1. Extraction and isolation
From 100 ml of bone marrow aspirate, mononuclear cells are isolated using a density gradient technique (Ficoll). Cultured mesenchymal cells are selected based on their ability to adhere to the culture plastic.
2. Culture and expansion in a GMP cleanroom
Cells are expanded in a GMP-certified laboratory until they reach the exact therapeutic dose established for each clinical indication. Doses are protocolized and authorized by the AEMPS: 20 million CMC for tendon pathology, 40 million for joints, and 40 million for the spine (distributed at 20 million per disc). In multi-zone interventions, where different anatomical structures are treated simultaneously, the total dose may reach 120 million CMC in a single surgical procedure.
3. Manufactured product certification
Prior to application, the medicinal product undergoes a thorough quality control process that includes:
- Verification of the exact dose of viable mesenchymal stem cells
- Cell viability ≥ 90%
- Characterization of cellular identity markers (CD73, CD90, CD105 positive; CD14, CD34, CD45 negative)
- Absence of mycoplasma and sterility control
- Container compliance and triple sterile packaging
All of this is certified in the Certificate of Manufactured Product, the pharmaceutical equivalent of the quality specification sheet of any conventional medicinal product. Only after its issuance can the application to the patient be authorized.
See also: What cellular treatments can be considered legal and regenerative?
The cellular dose in tendons, cartilage, and lumbar disc: clinical evidence by indication
The definition of dose is not universal: it depends on the target tissue, the degree of injury, and the results accumulated in authorized clinical trials. ITRT has developed and sponsored clinical trials with cultured mesenchymal cells in the following indications:
Tendon injuries
The tendon is the indication with the longest clinical and scientific track record at ITRT. The protocol includes ultrasound-guided CMC application in injuries of the patellar tendon, Achilles tendon, hamstrings, and supraspinatus. Structural regeneration documented by MRI across successive clinical follow-ups represents the differential evidence of this approach.
Cartilage (osteoarthritis)
ITRT has participated in several clinical trials in knee osteoarthritis, including randomized and multicenter designs. The autologous phase I-II trial was sponsored directly by ITRT; the randomized phase IIb trial with allogeneic CMC was sponsored by the Science Park of the University of Valladolid, with ITRT as a participating research center.
Lumbar intervertebral disc
Lumbar degenerative disc disease was one of the first indications explored by ITRT. The sponsored clinical trial (EudraCT: 2008-001191-68) evaluated the intradiscal application of autologous CMC in patients with lumbar degeneration, with results published in Transplantation Journal (2011) and in The Journal of Orthopaedics Trauma Surgery and Related Research (2010).
In all of these indications, the cellular dose is not an accessory data point: it is the parameter that allows comparing results across patients, reproducing the protocol, and evaluating efficacy within a rigorous scientific framework.
What you will not find in an unregulated practice
A variety of procedures exist in the market that are presented with terminology similar to that of advanced therapy medicinal products. Understanding the differences allows for informed decision-making.
| Parameter | Advanced therapy medicinal product (CMC) | Unregulated practice (same-day concentrate) |
| Defined cellular dose | Yes. Between 20 and 120 million CMC, certified by a GMP laboratory | No. The actual number of viable cultured mesenchymal cells is unknown |
| Cell culture and expansion | Yes. A weeks-long process in a GMP cleanroom | No. Concentrate obtained and applied on the same day |
| Cellular characterization | Yes. Identity markers analytically verified | No. Mixed cell populations without characterization |
| Certificate of manufactured product | Yes. Viability, sterility, absence of mycoplasma | No equivalent documentation exists |
| AEMPS authorization | Yes. Individual authorization prior to each application | Not applicable. The procedure is not regulated as a medicinal product |
| Published clinical evidence | Yes. Publications in indexed international journals | Generally nonexistent or of low methodological quality |
This comparison is not intended to discredit any practice, but to provide patients and professionals with objective criteria to evaluate what is being proposed to them.
ITRT: over 20 years defining the dose with pharmaceutical precision
ITRT operates at Centro Médico Teknon, in Barcelona, as a pharmaceutical laboratory specialized in advanced therapy medicinal products. Since the beginning of its research activity in 2002, dose control has been a central pillar of its clinical methodology.
Every medicinal product developed at ITRT includes:
- Manufacturing protocol validated under GMP regulations in a cleanroom
- Individual authorization by the AEMPS for each application
- Dose defined by the corresponding authorized clinical trial protocol
- Clinical and imaging follow-up (MRI) to document structural changes
The result of this rigor is not promises: it is scientific publications, MRI imaging, and a history of clinical trials under continuous regulatory supervision.
Frequently asked questions about cellular dose and mesenchymal cells
It is the number of viable cultured mesenchymal cells (CMC) contained in the medicinal product at the time of application. At ITRT, this figure ranges between 20 and 120 million cells, analytically verified in a GMP laboratory and certified in the product certificate prior to any clinical application.
Because only products manufactured under pharmaceutical regulations and classified as advanced therapy medicinal products are required to define and certify their dose. Cellular concentrates applied on the same day of extraction — without culture or expansion — are not classified as medicinal products under European regulations and do not require this certification.
Not necessarily. The dose is defined based on the target tissue, the clinical protocol, and the results obtained in the authorized clinical trials for each indication. This adaptation is part of the methodological rigor of a regulated medicinal product.
It means that, for each patient and each dose of cultured mesenchymal cells, the Spanish Agency of Medicines and Medical Devices validates the request for use of the medicinal product. This individual authorization is distinct from a centralized marketing authorization: it is specific, traceable, and linked to the history of the authorized clinical trial.
Mesenchymal stem cells is the reference scientific term for this cell population. Cultured mesenchymal cells (CMC) is the regulatory designation used in Spain under AEMPS regulations to identify the medicinal product manufactured from these cells once isolated and expanded in culture. Both terms refer to the same biological reality, but in different contexts: one scientific, the other pharmaceutical-regulatory.
Legal disclaimer
Advanced therapy medicinal products with cultured mesenchymal cells (CMC) require a medical prescription and individual authorization by the AEMPS. This content is for informational purposes only and does not substitute medical advice. The clinical results mentioned correspond to patients treated in the context of authorized clinical trials and are not extrapolatable to other patients.
