Joost Peerbooms

26 Chapter 2 DISCUSSION The objective of this review was to assess the differences between the concentrations of blood components and growth factors in PRP between the various PRP separation systems. The findings in this review demonstrate that there is a large heterogeneity among various systems regarding the concentrations of platelets and leukocytes. Regarding the concentrations of growth factors, there is a large heterogeneity both between and within the different systems. Furthermore, the concentration of VEGF tended to be higher in PRP produced by systems that produce higher concentrations of platelets and leukocytes. Concentration of Platelets There was a large difference in the concentration of platelets between the systems studied in this review. Roughly, the systems studied in this review can be divided into high- and low-yielding devices. This division into high- and low-yielding devices has been described before by Dhurat and Sukesh. 11 Dhurat and Sukesh 11 described that PRP devices can usually be divided into lower (2.5-3 times the baseline concentration) and higher (5-9 times the baseline concentration) systems. The low-yielding devices in this review produce PRP with a platelet concentration around 500 x 10 3 µL, whereas the high-yielding devices generally produce a platelet concentration over 750 x 10 3 µL. Among the high-yielding devices were the GPS III, SmartPrep, and Magellan systems; the lower concentration systems were the ACP, Cascade, Endoret, and RegenPRP. These findings correlate well with the findings in this review. The concentration of platelets in PRP is of importance, as the mechanism of action of PRP is mainly based on the growth factors and cytokines found in the alpha-granules in the platelets. However, there is no consensus about the optimal concentration of platelets in PRP: some authors have reported platelet concentrations greater than 200 x 10 3 µL 37 to be therapeutic, whereas others have reported concentrations of 1000 x 10 3 µL. 34 In the present study, the platelet concentrations of all of the PRP separation systems exceeded a platelet concentration of > 200 x 10 3 µL, which implies that all the devices met the definition for therapeutic and effective PRP as defined by Mazzucco et al. 37 Concentration of Leukocytes Comparable with the concentration of platelets in PRP, the concentration of leukocytes differed largely between the systems studied in this review. Additionally, no large differences within the systems were found. PRP separation systems can be divided into systems producing a high and a low concentration of leukocytes. The concentration of leukocytes in PRP is a direct result of the preparation method that is used. Buffy coat- based systems, for example, produce PRP with a high concentration of leukocytes, as the buffy coat is rich in leukocytes. Plasma-based systems, in contrast, are designed to separate only the platelet and plasma portions of whole blood and therefore contain a