Biologically derived therapies are rapidly gaining popularity, especially for treating equine tendon and ligament injuries, and veterinarians have been hard at work determining the best case and therapy selection, dosage, and frequency of administration for each. To this end, at the 2011 American Association of Equine Practitioners Annual Convention, held Nov. 18-22 in San Antonio, Texas, David Frisbie, DVM, PhD, Dipl. ACVS, ACVS-MR, of Colorado State University, presented a study in which he examined platelet-rich plasma (PRP) products derived from several body systems and acellular bone marrow aspirate (ABMA) for treating these types of injuries.

According to Frisbie, PRP is widely used, but current recommendations for treatment dosage, frequency, and timing of administration after tendon and ligament injury vary considerably. Other questions that are not yet clear for practitioners include: the minimum and maximum desirable platelet concentrations; whether to "activate" the PRP (which involves adding components such as calcium or thrombin, an enzyme in the blood clotting cascade, in order to increase platelet growth factor release); and how to select which clinical cases are most likely to benefit from PRP therapy.

Frisbie referenced previous studies showing under laboratory conditions (in vitro) that PRP and ABMA upregulate cartilage oligomeric matrix protein (COMP), a protein in equine tendon that "is necessary for tendon to resist, load."1 In other words, COMP allows the tendon to exert proper force against gravity and the weight of the horse as the horse stands and moves. He also referenced work that showed an upregulation of the genes involved in tendon healing after PRP treatment.

In the current study Frisbie and his team compared three commercially available PRP products--autologous conditioned plasma (ACP), Fibrivet, and fPRP--and ABMA with a plasma control. They examined the ability of each of the products to concentrate platelets, white blood cells, and several growth factors at the injury site. Platelets, normally viewed as the cells responsible for blood clotting, also release growth factors that aid in tissue production and healing. They also evaluated each product's effects on tendon tissue components (tenocyte proliferation and matrix production, both required to rebuild damaged tendon) after 72 hours.

Results were mixed. Only ACP promoted significant tenocyte and matrix proliferation, as compared to the control group. However, only fPRP increased platelet and growth factor concentrations significantly when compared with controls.

Many questions about biologically derived therapies remain, but in this particular study ACP appeared to have the most desirable effect for tendon healing. Frisbie indicated that more research is still needed in this area, particularly in determining dosing frequency and the "therapeutic window" (minimum and maximum concentration range that will provide benefit rather than harm) for these therapies.

1. Smith RK, Zunino L, Webbon PM, Heinegård D., The distribution of cartilage oligomeric matrix protein (COMP) in tendon and its variation with tendon site, age and load. Matrix Biol. 1997 Nov;16(5):255-71.

About the Author

Christy Corp-Minamiji, DVM

Christy Corp-Minamiji, DVM, practices large animal medicine in Northern California, with particular interests in equine wound management and geriatric equine care. She and her husband have three children, and she writes fiction and creative nonfiction in her spare time.

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