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Stem cells

Stem cells in dogs and cats

Stem cells are cells that have not yet decided what kind of cell to become. The ones used in pets are usually mesenchymal stem cells, taken from fat, bone marrow, umbilical cord or other tis

What it is

Stem cells are cells that have not yet decided what kind of cell to become. The ones used in pets are usually mesenchymal stem cells, taken from fat, bone marrow, umbilical cord or other tissue. They can come from your own pet, from a donor animal of the same species, or, in one licensed European product, from a horse. Researchers think they work less by turning into new cartilage and more by releasing signals that calm inflammation, which is a different idea from the word regenerate. In dogs they are usually injected into a sore joint. In cats, the most studied use is two infusions into a vein for severe mouth inflammation, which is a completely different disease and a completely different route.

What the evidence shows

For arthritis in dogs there are five randomized controlled trials, covering roughly 250 to 260 dogs in total. Four of the five found improvement on scores given by owners and veterinarians. In the three trials that also measured walking with force plates, the objective measurement did not improve. The best single study, in 74 dogs across nine clinics, found 79.2% success on the owner score against 55.4% in the placebo group. That is a real difference and it was statistically significant, and the placebo group still succeeded more than half the time, which tells you how easy it is to feel that a treatment worked. For cats, the strongest evidence is for severe, treatment-resistant mouth inflammation: 46 cats received two infusions, about three-quarters of owners reported improvement at 90 days, and 35 cats followed for a full year had no serious side effects linked to the treatment. The most recent authoritative review of all of this concluded that the most robust data are for tendon injuries in horses and arthritis in dogs and horses, and that for other conditions the evidence is pilot studies, case series or single trials.

What it does not show

Here is what we cannot tell you, and we would rather say so. No stem cell product for animals is FDA-approved in the United States, and FDA states that marketing an unapproved one is illegal. Because the published studies used different cells, different doses and different measurements, researchers could not combine them, so nobody can tell you how much improvement to expect for your animal or how long it would last. Two independent reviews graded this evidence weak to moderate with a high risk of bias. The objective walking measurements have not backed up the owner scores, so a claim that stem cells rebuild or regrow cartilage in a dog is not supported, and the authors of the best trial said outright that they did not address cartilage regeneration. In cats, much less is known than in dogs, and cats cannot be assumed to respond like dogs because they handle many medicines differently. FDA also names real risks for this class of product: disease passed from a donor animal, serious infection, and severe allergic reactions including anaphylaxis and death. Before you agree to anything, it is fair to ask your veterinarian what approved treatments have already been tried, what improvement they would expect to see in your animal and by when, and what the plan is if it does not work.

On "immune-privileged"

In a randomised safety trial in dogs, both equine and canine MSCs raised antibody titres, with no adverse events after single or repeated administration. Umbilical-cord MSCs are immune-evasive, not immune-invisible — and we will not tell you otherwise.

Punzón et al., Front Vet Sci 2023;10:1098029. PMID 37266387

Sources

  1. FDA: no animal cell or tissue product is approved — U.S. FDA, FDA's Role in Veterinary Regenerative Medicine, content current as of 03/31/2025. 'Currently, no ACTPs are FDA-approved.' https://www.fda.gov/animal-veterinary/cell-and-tissue-products-a
  2. FDA: risks and owner Q&A — U.S. FDA, Q&A for Pet Owners on Animal Cells, Tissues, and Cell- and Tissue-Based Products (ACTPs), content current as of 02/27/2025. https://www.fda.gov/animal-veterinary/cell-and-tissue-products-a
  3. Authoritative current review of MSC use in real pets — Zayed M, Jeong BH. Mesenchymal stem cells in veterinary clinical practice: evidence from naturally occurring diseases. The Veterinary Journal 2026;320:106837. PMID 42624276. https://doi.org/10.1016/j.tvjl.2026.106837
  4. Best canine osteoarthritis randomized controlled trial — Harman R, et al. A prospective, randomized, masked, and placebo-controlled efficacy study of intraarticular allogeneic adipose stem cells for the treatment of osteoarthritis in dogs. Front Vet Sci 2016;3:81. PMID 27695698. 74 dogs; 79.2% vs 55.4% placebo, p=0.029; cartilage regeneration not addressed. https://doi.org/10.3389/fvets.2016.00081
  5. Systematic review: evidence could not be pooled — Olsson DC, et al. Administration of mesenchymal stem cells from adipose tissue at the hip joint of dogs with osteoarthritis: a systematic review. Res Vet Sci 2020. Six studies included; risk of bias moderate to high; meta-analysis not possible. https://doi.org/10.1016/j.rvsc.2020.11.014
  6. Independent knowledge summary: strength of evidence weak — Moloney M. In dogs with osteoarthritis, is intra-articular allogenic mesenchymal stem cell therapy more effective than placebo effect? Veterinary Evidence 2022;7(3). RCVS Knowledge Summary; strength of evidence graded weak. https://doi.org/10.18849/ve.v7i3.473
  7. Strongest feline cell therapy trial — Williams VS, et al. Clinical field study evaluating the safety and efficacy of allogeneic uterine-derived mesenchymal stem cells for refractory feline chronic gingivostomatitis. J Feline Med Surg 2025;27(11). PMID 40999564. 46 cats, 90 days, baseline-controlled. https://pmc.ncbi.nlm.nih.gov/articles/PMC12640453/
  8. One-year feline safety follow-up — Williams VS, et al. Long-term field safety study evaluating allogeneic, uterine-derived mesenchymal stem cells for refractory feline chronic gingivostomatitis. J Feline Med Surg 2026;28(4). PMID 41757710. 35 cats to day 365; no serious treatment-associated adverse events. https://pmc.ncbi.nlm.nih.gov/articles/PMC13111817/
  9. The only licensed canine stem cell medicine (EU/UK, not US) — European Medicines Agency, DogStem EPAR. Marketing authorisation 17 June 2022, procedure EMEA/V/C/005829. Pivotal trial: Punzon E, et al. JAVMA 2022;260(15):1947-1955. PMID 36198051. 80 dogs, double-blinded, randomized, placebo-controlled. https://www.ema.europa.eu/en/medicines/veterinary/EPAR/dogstem
  10. The veterinary profession's own caution — American Veterinary Medical Association policy, Regenerative medicine. 'The AVMA supports the continued scientific development of these modalities while at the same time encouraging its members to employ caution with respect to their use.' https://www.avma.org/resources-tools/avma-policies/regenerative-
ProtocolsClaims & evidence policy