Stem Cell Use in Horses

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A recent television documentary about stem cell fraud in human medicine posed this question: “Are stem cells the ‘snake oil’ of the 21st century?” The documentary focused on the growing, highly lucrative business of fake stem cell cures that reportedly resulted in a federal investigation. With public awareness of failures in stem cell therapy newly heightened, it is important to reflect on our situation in equine medicine.

Stem cell treatments for horses have been available since at least 2005. They have become a relatively common treatment for many equine musculoskeletal injuries, often promoted as a panacea for bone, cartilage and tendon healing. Internet testimonials and videos claiming miraculous cures in individual patients with neurologic and laminitic conditions have fueled often irrational exuberance and extravagant expectations. To date, no published controlled clinical studies show efficacy in use of stem cell treatment for any of the conditions being treated. In fact, the two most recent studies evaluating stem cells--one in a tendonitis model and the other in a cartilage defect model--showed no significant difference with their use, either clinically or histologically, as compared to controls in which stems cells were not used.

Papers have touted stem cells’ miraculous ability in the laboratory; however, once administered to the patient, the situation changes dramatically. A multitude of poorly understood factors likely mitigate the activity of stem cells once administered. Patients have their own stem cells, and wound healing is modulated through a complex array of molecular events, including cytokine signaling. Equally important, stem cell culturing methods and source tissues (bone marrow, adipose, fetal cells and cord blood) vary among laboratories.

Are stem cells from any source good for everything? Most scientists would agree this is unlikely, and future treatment will likely involve selection of stem cells with a particular phenotype or genetic modification in order to treat a specific disease. The most basic questions remain. How do we know that the stem cells from a particular laboratory or process are not terminally differentiated fibroblasts that have absolutely no biologic effect? How do we know they will persist in the wound environment long enough to have a biologic effect? How do we know they are of the correct phenotype? Plasticity, differentiation into the desired tissue type, and/or feeder effects may be present in the petri dish; however, mechanisms once injected into the patient have yet to be elucidated.

With a virtual absence of oversight and regulations, equine veterinary use of stem cells has dramatically increased, resulting in over a dozen university, private enterprise and private practices culturing allogeneic and/or autologous stem cells for use in horses. Expert opinion, testimonials, and anecdotal evidence, are not in short supply. When coupled with a lack of good clinical evidence or even a good understanding of potential mechanisms, they threaten to pull stem cell therapies into the abyss often occupied by nutraceuticals and supplements.

Stem cells hold promise. However, clinical acceptance has greatly outpaced the scientific evidence. That evidence needs to be supplied, with both professional organizations and those producing stem cells taking the lead. Finally, practitioners using stem cells also have a responsibility to accurately represent these therapies to their clients.

Reprinted with permission of Equine Disease Quarterly.