Reply

Abstract

Sir: The letter from Kakudo et al. indicated the “low yield” (75.1 percent) of platelets in our platelet-rich plasma preparation. In addition, they commented that the double-spin procedure described in the book by Marx and Garg is a standard preparation method for platelet-rich plasma at present1,2 and that the definition of platelet-rich plasma in our article3 is not appropriate because the growth factor concentrations are much lower in our platelet-rich plasma than in the product of the double-spin method. We must explain the difference between the platelet-rich plasma in our article and the platelet-rich plasma that Kukudo et al. describe as the “real” platelet-rich plasma. Platelet-rich plasma is a medical term originated not from orthodontic surgery or from Marx and Garg but from the field of blood transfusion medicine and hematology. Indeed, many scientific articles,4,5 even recently, use the term “platelet-rich plasma” for a product obtained through a single light spin of whole blood, as we used. The American Association of Blood Banks technical manual,6 a typical textbook of blood transfusion medicine, states that “Platelet-rich plasma is separated from whole blood by light-spin centrifugation and the platelets are concentrated by heavy-spin centrifugation with subsequent removal of supernatant plasma” (Fig. 1). Thus, we propose the term “concentrated platelet-rich plasma” or “therapeutic platelet-rich plasma” in scientific articles for the platelet-concentrated plasma product to avoid any confusion or misunderstanding.Fig. 1.: Preparation processes of various serums and plasmas from whole blood. Concentrated/therapeutic platelet-rich plasma can be obtained through heavy-spin centrifugation of platelet-rich plasma; although the concentration of platelets (and platelet-derived cytokines) in concentrated/therapeutic platelet-rich plasma is much higher than that of platelet-rich plasma, the volume of concentration/therapeutic platelet-rich plasma is much smaller than that of platelet-rich plasma, and platelet yield is also smaller in concentration/therapeutic platelet-rich plasma (30 to 60 percent) compared with platelet-rich plasma (70 to 80 percent). White numbers indicate platelet yield of each blood product. The concentration of platelet-derived factors is influenced by both platelet yield and the volume of each product. PRP, platelet-rich plasma; PPP, platelet-poor plasma; SWB, serum from whole blood; SPRP, serum from platelet-rich plasma; SPPP, serum from platelet-poor plasma.In our study, we employed three preparations of human serum: serum from whole blood, serum from platelet-rich plasma, and serum from platelet-poor plasma (Fig. 1). Fetal bovine serum is widely used in research as a standard additive of cell culture, and it is actually bovine serum from whole blood. We attempted to compare human serum from platelet-rich plasma to bovine and human serum from whole blood and human serum from platelet-poor plasma to accurately evaluate the value of serum from platelet-rich plasma for expansion of various types of human cells. For therapeutic use, concentrations of beneficial factors such as platelet-derived cytokines is an important index, and concentrated platelet-rich plasma obtained through the double-spin procedure is more useful than platelet-rich plasma. However, for the purpose of culture additive, either for research or for clinical cell therapy, not only the concentration but also the volume of the product is important; in other words, platelet yield (total amount of platelets) is a critical factor when using human blood with limited availability. Marx reported that the mean platelet yield of the concentrated platelet-rich plasma ranged from 29 to 62 percent that of whole blood, depending on the separation devices used,2 whereas the platelet yield of platelet-rich plasma that we prepared in our study was 75.1 percent that of whole blood. Thus, platelet yield in platelet-rich plasma obtained after a single light spin is much greater than that from concentrated/therapeutic platelet-rich plasma (Fig. 1). Finally, we have to add a note on an error in our article3 that we noticed in the reviewing process for this Reply. We reported that the centrifugation force we used for preparation of platelet-rich plasma and platelet-poor plasma was 93 g and 841 g, respectively; however, 186 g and 1682 g, respectively, are the accurate values. The authors regret the error in calculation. Masakazu Kurita, M.D. Emiko Aiba-Kojima, M.D. Kotaro Yoshimura, M.D. Department of Plastic Surgery University of Tokyo Graduate School of Medicine Tokyo, Japan