Veterinarians find therapy rich in possibilities
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.
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
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