Updated: April 2024
As the field of biologics (using natural substances from the body to heal itself) and regenerative medicine has advanced in recent years, athletes have increasingly shown interest in therapies that utilize biological substances, such as stem cells, to heal sports injuries faster. Researchers are still investigating the use of such treatments and their potential efficacy, but given the complicated and rapidly evolving nature of regenerative medicine, the questions below have been compiled to address some of the most important information that athletes need to know about stem cell therapies.
What are stem cells?
Sometimes called the body’s “master cells,” stem cells can turn into many different cell types depending on the type of stem cell and the surrounding chemical/hormonal environment. Stem cells exist in almost all tissues of the body, even in adults. There are many different types of stem cells with differing abilities to turn into other cell types. Stem cells have been successfully isolated from bone marrow, adipose tissue (fat), blood, lung, heart, placenta, amniotic fluid, umbilical cord, and early-stage human embryos (embryonic stem cells). While there are many types of stem cells, they are all able to self-replicate and differentiate into different cell types.
Do stem cell therapies work to accelerate healing?
Stem cells are being investigated for their ability to repair, restore, replace, and regenerate cells, and could possibly be used to treat various medical conditions in the future. However, there are many clinics that offer various stem cells therapies now, and some athletes might be interested in such therapies to treat acute injuries rapidly, or chronic injuries that won’t get better. In theory, stem cells seem like an attractive treatment option because of the potential for stem cells to “turn into” or renew the tissue that is injured, or secrete other factors to aid in healing.
The American College of Sports Medicine has published an article on the responsible use of stem cell therapies in sport 1. It is freely available to the public, and any athlete considering such therapies may review the article for a data-driven point of view on the effectiveness of stem cell therapies for various conditions. Currently, there are no proven, FDA-approved stem cell treatments for muscle, joint, or tendon injuries.
Are all stem cell therapies legal?
There are some FDA-approved stem cell therapies 2 solely for treating certain blood disorders, but there are also many stem cell treatments that have not been evaluated or approved by the FDA.
Some clinics might tell patients that their stem cell therapies fall outside of FDA regulations, or that FDA regulations do not apply to their procedures. However, this is not true. Some uses of stem cells are exempt from pre-market approval by the FDA, such as procedures where stem cells are extracted from the patient (e.g., from bone marrow), and then reinjected during the same surgical procedure. These cells are “autologous,” meaning they are the patient’s own cells, and are “minimally manipulated” before reinjection, meaning they may be concentrated or handled briefly but the cells aren’t cultured or grown over many days and no additional substances or drugs are added to them. Use of stem cells in this way does not require a clinic to have the FDA approve each use of the stem cells, but the clinic still has to abide by FDA regulations relating to stem cells.
However, some clinics perform stem cell procedures that do not meet the above criteria! Some clinics offer “off the shelf” stem cell preparations, which are harvested from donor patients (e.g., umbilical cord extraction from mothers during elective c-section births). These stem cell cells are isolated using proprietary procedures, so it is often very difficult to know how much the cells have been manipulated, or if other substances and growth factors have been added. The FDA has issued warnings to consumers about stem cell therapies (including stem cell exosome therapies) because, for almost all these products, the safety and benefits are unproven. Any athlete considering a stem cell treatment of any type should read the recommendations from the FDA 3 by asking for proof that a stem cell product is FDA approved or that the FDA has issued an Investigational New Drug Application number.
More advice from the FDA on this topic is available here.
Are there risks associated with using stem cells?
Yes. The FDA has received reports of serious problems as a result of stem cell use, including a patient who became blind after a stem cell injection into the eye, a patient who developed a tumor after a stem cell injection into the spinal cord, and other adverse events. There have also been reports of serious adverse effects like tumor formation following “stem cell tourism” where patients travel to other countries to receive stem cell treatments that are not approved in the US 4.
The FDA also points out other safety concerns, including injection site reactions, the ability of stem cells injected into one part of the body to migrate to another part, failure of cells to work as expected, and the growth of tumors.
Athletes should also be aware that some physicians or clinics may not follow FDA guidelines on safety. The FDA has identified many clinics that are misusing stem cells or using them in ways not allowed under current regulations.
Are stem cell treatments prohibited in sport?
It depends. Stem cells that are extracted from the athlete and then reinjected in the same surgical procedure, with no growth factors or other prohibited substances added after harvesting, are not prohibited as long as they only return the functioning of the affected area back to normal and do not enhance it. Stem cell treatments like this that are “minimally manipulated” do not require FDA pre-market approval before it is used, but the stem cell treatment is still regulated by the FDA.
Stem cell injections are prohibited by WADA if they are modified in a way that causes the stem cells to be performance enhancing, or if prohibited substances, such as growth factors or hormones, are added to the stem cell preparation after it has been harvested (whether from the athlete or another donor). Make sure to check the status of any substance added to the stem cell preparation on GlobalDRO.com to see if a Therapeutic Use Exemption is required prior to receiving the treatment.
There are also commercially available stem cell products from donors that may be prohibited if any substances prohibited in sport were added to the stem cells. Keep in mind, any commercially available stem cell product by law must also be FDA approved, as it is considered a drug.
It is not possible for USADA to evaluate every product or procedure to provide an anti-doping status in every case. Athletes should work with their doctors to ensure the harvested stem cells are minimally manipulated and no prohibited substances are added. As long as this is the case, they are permitted in sport.
For the use of any other stem cell procedure or commercially prepared stem cell product, athletes should apply for a Therapeutic Use Exemption (TUE).
Is a TUE required for stem cell therapy?
Maybe. Stem cell procedures where the athlete’s own cells are harvested and then reinjected in the same day/same surgical procedure, and where no prohibited substances are added to the preparation, are not prohibited and do not require a TUE.
Athletes with a blood disorder who require an FDA-approved stem cell therapy should contact USADA to learn about the most up-to-date anti-doping rules.
Athletes wishing to participate in a registered clinical trial that involves stem cell therapy should also contact USADA, as a TUE may be required.
If in doubt, athletes and athlete support personnel should discuss the prohibited or permitted status of a procedure by calling USADA’s Drug Reference Team at (719) 785-2000 option 2, or emailing drugreference@USADA.org.
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More questions?
For questions about specific products, substances, and methods, contact USADA’s Drug Reference Line at drugreference@USADA.org or call (719) 785-2000, option 2.
References
1 Finnoff, J. T. et al. American Medical Society for Sports Medicine Position Statement: Principles for the Responsible Use of Regenerative Medicine in Sports Medicine. Clin J Sport Med 31, 530-541, doi:10.1097/JSM.0000000000000973 (2021).
2 Approved Cellular and Gene Therapy Products, <https://www.fda.gov/vaccines-blood-biologics/cellular-gene-therapy-products/approved-cellular-and-gene-therapy-products> US Food and Drug Administration, Accessed on 3/10/2024.
3 FDA Warns About Stem Cell Therapies, <https://www.fda.gov/consumers/consumer-updates/fda-warns-about-stem-cell-therapies> US Food and Drug Administration, Accessed on 3/7/2024.
4 Berkowitz, A. L. et al. Glioproliferative Lesion of the Spinal Cord as a Complication of “Stem-Cell Tourism”. N Engl J Med 375, 196-198, doi:10.1056/NEJMc1600188 (2016).