Veterinarians find therapy rich in possibilities

Platelet-rich plasma therapy is being increasingly used for canine orthopedic and sports medicine applications, but numerous questions remain regarding this promising treatment.
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Apr 01, 2014

This is the second article of a two-part dvm360 series focusing on regenerative medicine therapies. For part one, on stem cell therapy in dogs, visit http://dvm360.com/SurgerySTAT.


Dr. Sam Franklin
Platelet-rich plasma therapies have been studied extensively in human clinical medicine and in experimental animal models for facilitating the healing of bone, tendon and ligament as well as for intra-articular treatment of osteoarthritis. Although evidence supporting the efficacy of such treatments isn't always clear, the potential for augmented tissue healing using a simple, relatively inexpensive and autologous therapy is driving continued use and investigation in human medicine. Likewise, the use of platelet-rich plasma (PRP) is on the rise in clinical veterinary medicine, initially with equine patients and more recently with dogs.

Although there are no universal criteria defining what makes plasma "platelet-rich," the most lenient definition is a plasma preparation that contains a higher concentration of platelets than that found in the whole blood from which the PRP is prepared. The proposed mechanism of action is the provision of growth factors, stored within the platelet alpha granules, which may mitigate inflammation and initiate anabolic processes and tissue healing. Many different growth factors are contained in these alpha granules, but those most commonly cited to facilitate tissue healing include vascular endothelial growth factor (VEGF), platelet-derived growth factors (PDGF) and transforming growth factors β (TGFβ), among others.

PRP preparation


Platelet-rich plasma therapy is gaining ground in veterinary medicine for the treatment of orthopedic injuries and diseases. Will this technology soon be a popular option for your patients? (THINKSTOCK/XRENDER)
The primary goals of PRP preparation are to remove erythrocytes, which are inflammatory when extravascular, and increase platelet concentration in plasma. This can be accomplished with basic laboratory supplies and specific centrifugation protocols.1 However, many practitioners (in human and veterinary medicine) use commercially available PRP concentrating systems because they are convenient. In addition, these systems might facilitate maintenance of sterility and could potentially produce a more consistent PRP product, although this has not been demonstrated.

The majority of the commercially available proprietary systems are made for preparing human PRP and are now being sold in the veterinary market, many without published data characterizing the PRP obtained when used with canine blood. This is pertinent because the characteristics of PRP obtained using human blood and canine blood with the same system can differ. Although a comprehensive review of all the characteristics of PRP that a clinician should consider is beyond the scope of this article, the following are several criteria that clinicians should investigate if interested in using PRP:

> What is the platelet concentration, leukocyte concentration, and ratio of platelets to leukocytes in the final PRP preparation using blood from the species of interest? Although all PRP systems are supposed to concentrate platelets, some systems are leukoreductive while others concentrate leukocytes. While the concentration of anabolic growth factors tends to correlate with the platelet concentration, the concentrations of inflammatory cytokines also correlate with leukocyte concentration in human PRP.2 The ideal PRP for a given condition may be a function of platelet concentration, leukocyte concentration or their ratio.3

> How much blood is being taken from the patient for PRP preparation and how much PRP is produced?

> Is addition of calcium chloride, thrombin or some other step used to activate the platelets with the given PRP system of interest? Such treatments can prompt a rapid and abundant release of growth factors from the platelets. This may be beneficial or it may preclude more extended release if activation were allowed to occur naturally in vivo.3


Platelet-rich plasma can be produced from whole blood using a system such as this one from Arthrex Vet Systems in Naples, Fla. (PHOTO COURTESY OF DR. FRANKLIN)
For interested clinicians, reading the excellent but concise review by Arnoczky and Shebani-Rad is strongly encouraged.3 However, to summarize briefly, there is wide variability in different PRP preparations. Therefore the results with use of one PRP may not be representative of the results obtained using a different PRP. Likewise, the ideal PRP may differ depending on the condition being treated, such as intra-articular therapy for osteoarthritis versus intra-lesion injection for treatment of tendon injuries. Therefore, the onus is on clinicians to know the characteristics of the PRP system they are using and the associated evidence for efficacy in treating a specific medical condition in the species they are treating.