The ISCT minimal criteria are the three-part definition researchers apply before calling a cell a mesenchymal stromal cell. They were published in 2006 so that results from different laboratories could be compared. This article quotes all three criteria, gives the numeric thresholds, and explains what they do not establish.
TLDR: In 2006 the International Society for Cellular Therapy set three minimal criteria for a mesenchymal stromal cell: plastic adherence in standard culture, a defined surface marker profile, and differentiation into three lineages in vitro. The marker rule is numeric. At least 95 percent of the population must express CD105, CD73 and CD90, and no more than 2 percent may express CD45, CD34, CD14 or CD11b, CD79a or CD19, and HLA class II. The criteria standardize research reporting. They are not a safety or efficacy finding, and banking adipose tissue does not guarantee eligibility, access, or clinical benefit.
Important Disclaimer: Save My Fat connects patients and providers to a U.S. tissue bank. Save My Fat does not provide FDA-approved treatments or cures and does not guarantee eligibility, access, or clinical benefit. Adipose tissue and stromal vascular fraction are investigational and not FDA approved. The criteria described here are a research definition, not a regulatory approval and not a measure of clinical usefulness. This content is for educational purposes only, and readers should consult their own licensed healthcare professionals.
Read enough about cell therapy and the phrase mesenchymal stem cell starts to sound like a fixed biological category, the way red blood cell is fixed. It is not. The definition most scientists use is a checklist agreed on in 2006, and it is far more modest than the marketing around it.
That checklist also explains a quirk on laboratory reports. The 2006 statement says mesenchymal stromal cell, not mesenchymal stem cell. The word swap was deliberate, and for a patient it is the most useful detail here.
Where the ISCT Minimal Criteria Came From
By the mid-2000s the phrase mesenchymal stem cell appeared in study after study without meaning the same thing twice. One group grew cells from bone marrow, another from fat, a third from cord tissue. Comparing two papers meant guessing whether the teams had studied the same kind of cell.
The International Society for Cellular Therapy answered with a short position paper. Dominici and colleagues published the 2006 ISCT position statement in Cytotherapy, volume 8, issue 4, pages 315 to 317. The goal was comparability across laboratories. The committee did not set out to certify that a cell population was safe or useful, and that distinction gets lost constantly.
The Three Criteria, Word for Word
The statement is short enough to read in the original language rather than in paraphrase. Here are all three criteria exactly as published.
The paper states: “First, MSC must be plastic-adherent when maintained in standard culture conditions. Second, MSC must express CD105, CD73 and CD90, and lack expression of CD45, CD34, CD14 or CD11b, CD79alpha or CD19 and HLA-DR surface molecules. Third, MSC must differentiate to osteoblasts, adipocytes and chondroblasts in vitro.”
Three sentences, three kinds of measurement. The first describes behavior in a culture flask, where the cells of interest stick to plastic and others do not. The second describes proteins on the cell surface. The third asks the cells to take on bone, fat, and cartilage lineages in a dish, using stains that a later IFATS and ISCT joint statement detailed in 2013.
The Numbers Behind Criterion Two: Positive and Negative Marker Panels
The second criterion is quoted most and understood least. In the published statement it reads as a plain list of markers, but the accompanying table attaches hard numbers to that list. Those numbers are what a flow cytometry report is checked against.
Greater than or equal to 95 percent of the population must express CD105, CD73 and CD90. Less than or equal to 2 percent may express CD45, CD34, CD14 or CD11b, CD79a or CD19, and HLA class II. Both figures are measured by flow cytometry.
| Surface marker | Panel | Threshold by flow cytometry |
|---|---|---|
| CD105 | Positive | 95 percent or more of the population |
| CD73 | Positive | 95 percent or more |
| CD90 | Positive | 95 percent or more |
| CD45 | Negative | 2 percent or less |
| CD34 | Negative | 2 percent or less |
| CD14 or CD11b | Negative | 2 percent or less |
| CD79a or CD19 | Negative | 2 percent or less |
| HLA class II | Negative | 2 percent or less |
Read the table as one statement rather than eight rows: a qualifying population is overwhelmingly one thing and nearly free of several others, because the negative panel rules out blood, immune, and endothelial cells in the sample. A report naming markers without percentages has answered half the criterion.
Why the Statement Says Stromal and Not Stem
The ISCT used mesenchymal stromal cell on purpose. The term stem cell was being applied loosely to populations never shown to behave like stem cells, so the committee chose the more conservative word. The abbreviation MSC survived and the words behind it changed.
The reason sits inside the criteria. Plastic adherence, a marker profile, and differentiation in a dish do not test self-renewal, and none establishes how a cell behaves inside a living body. The statement declined to claim what it had not measured. Anyone comparing mesenchymal stromal cells across tissue sources meets this nomenclature right away.
Careful naming is a habit across the field. The extracellular vesicle community maintains its own reporting standard, and MISEV2023 is the current edition after MISEV2014 and MISEV2018. When a marketing page says stem cell where the source paper says stromal cell, that is not a small edit.
What Meeting the Criteria Does Not Tell You
The criteria describe a population, but they do not endorse it. Nothing in the three items speaks to whether a cell population helps anyone. Definition and clinical usefulness are separate questions, answered by separate studies.
ADIPOA2 shows the gap. In that Phase 2b study of a single knee injection of autologous adipose-derived MSCs against placebo in mild to moderate knee osteoarthritis, published by Pers and colleagues in the Annals of the Rheumatic Diseases in December 2025, “26 patients (47.3%) versus 23 patients (54.8%) were strict OARSI/OMERACT responders (relative risk 0.86 [95% CI: 0.58-1.28]; P =.46).” The authors concluded that the injection “did not significantly improve pain and function”, and the placebo group scored numerically higher.
Regulatory status makes the same point. RYONCIL, proper name remestemcel-L-rknd, is the first FDA-approved mesenchymal stromal cell therapy, approved December 18, 2024 for steroid-refractory acute graft versus host disease in pediatric patients 2 months of age and older. The FDA’s consumer alert on these products separately warns they are not approved for conditions including arthritis, back pain, and Alzheimer’s. Adipose-derived cells remain investigational, the evidence is preliminary, and outcomes cannot be predicted.
How to Read a Marker Claim Without a Biology Degree
Once you know the checklist, marketing language is easier to audit. A specific claim names the markers, the percentages, the method, and the passage number. A vague claim leans on the phrase stem cell instead.
Passage number matters. Wagner and colleagues reported in PLoS One in 2008 that within 43 to 77 days of cultivation, or 7 to 12 passages, cultures showed morphological abnormalities, enlargement, and attenuated expression of specific surface markers before proliferation stopped. A marker profile is a snapshot, not a permanent label.
Save My Fat is a connector service linking patients and providers to a U.S. tissue bank, and banking is a storage decision rather than a treatment decision. Readers weighing tissue sources can review how MSC sources compare and the patient guide to adipose-derived stem cells, then take questions to a licensed provider.
Frequently Asked Questions
Who created the ISCT minimal criteria and why?
The International Society for Cellular Therapy published them in 2006, with Dominici as lead author, in Cytotherapy volume 8, issue 4, pages 315 to 317. Laboratories were describing very different cell populations under one name, which made studies impossible to compare. The criteria set a shared minimum for reporting.
What are the three specific requirements a cell must meet?
Plastic adherence in standard culture, a defined surface marker profile, and differentiation to osteoblasts, adipocytes and chondroblasts in vitro. The marker rule carries numbers: at least 95 percent expressing CD105, CD73 and CD90, and no more than 2 percent expressing CD45, CD34, CD14 or CD11b, CD79a or CD19, and HLA class II.
Why did the terminology shift from stem cell to stromal cell?
Because the stem cell label was being applied loosely to populations that had not been shown to behave that way. The ISCT chose mesenchymal stromal cell while keeping the familiar MSC abbreviation. The three criteria test adherence, markers, and differentiation in a dish, none of which establishes stem cell behavior in a person.
How does this affect how Save My Fat and other companies describe banked cells?
It sets the vocabulary a careful company should use. Save My Fat is a connector linking patients and providers to a U.S. tissue bank and does not collect, process, store, or treat. Adipose tissue and stromal vascular fraction are investigational and not FDA approved, and characterization describes a sample rather than promising anything.
Does meeting these criteria mean the cells will help a patient?
No. The criteria are a research definition written for comparability, and no regulator treats them as approval. The ADIPOA2 Phase 2b trial reported no significant improvement in pain and function against placebo in knee osteoarthritis. Meeting a definition and benefiting a patient are different questions.
What does plastic adherence mean in a laboratory?
It means that in a standard culture flask, the population of interest attaches to the plastic surface while other cells do not. That behavior is how these populations were originally isolated, and it remains criterion one because any laboratory can reproduce it cheaply. It is a starting filter, nothing more.
Key Takeaways
The ISCT minimal criteria are three items published in Cytotherapy in 2006. Cells must be plastic-adherent in standard culture, must express CD105, CD73 and CD90 while lacking CD45, CD34, CD14 or CD11b, CD79alpha or CD19 and HLA-DR, and must differentiate to osteoblasts, adipocytes and chondroblasts in vitro. The numbers behind the second criterion are 95 percent or more for the positive panel and 2 percent or less for the negative panel, by flow cytometry.
The committee wrote this to make research comparable between laboratories, not to certify that a product is safe or effective, and meeting the criteria says nothing about clinical usefulness. The deliberate use of stromal cell instead of stem cell is the detail patients should carry away, marking the line between what was measured and what was assumed. Adipose-derived cells remain investigational and not FDA approved, individual results may vary, and outcomes cannot be predicted.
Save My Fat operates as a tissue preservation service, not a medical practice or treatment provider. Stem cell and regenerative medicine regulations vary by state, including specific informed-consent and disclosure requirements in Florida, Utah, and Nevada governing tissue and stem cell services. Banking adipose tissue does not connect patients to any treatment pathway, and any future use depends on FDA regulatory status, physician guidance, and the availability of approved or investigational pathways at that time.
Patients considering adipose tissue banking for potential future use can review current pricing or contact our team with questions about collection and storage logistics.
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This article is for educational purposes only and does not constitute medical or legal advice. Legal and medical review including neurology and neurosurgery input is required before publication. Please consult your neurologist or neurosurgeon before making any decisions about banking, treatment, or research participation.
About the author: Oscar Tellez is the founder and CEO of Save My Fat. He holds a Bachelor of Science in Exercise Science and Health Promotion from Florida Atlantic University. He has spent more than a decade in the regenerative medicine industry across product distribution, laboratory and vendor relationships, and provider training. He is not a licensed clinician, and this article is educational, not medical advice.
Related guide: the stem cell science glossary.
