Platelet-Rich Plasma: The Importance of Platelet Separation and Concentration

Abstract

Sir: We are impressed by the article entitled “Differential Effects of Three Preparations of Human Serum on Expansion of Various Types of Human Cells” by Kurita et al. (Plast Reconstr Surg. 2008;122:438–448).1 This report describes biomedical components and the potential of platelet-rich plasma as a culture additive. However, we think there might be a mistake regarding the way the authors produced platelet-rich plasma and in its definition, because the amount of platelet contained in platelet-rich plasma, which had been prepared in their way, is only 75.1 percent (0.75×) of the whole blood. The methods of producing platelet-rich plasma and its clinical applications have been studied for a long time, mainly in the fields of oral and maxillofacial surgery. There are many oral surgeons who have conducted studies regarding platelet-rich plasma, and the pioneer in this field is Marx. His work regarding the method of platelet-rich plasma production and its clinical applications has been widely published, and his textbook2 has been considered a must-read book for those who use platelet-rich plasma. The textbook states the following: The double-spin method is more recommended than the single-spin method in platelet-rich plasma production. It is not possible to separate and concentrate platelets to a therapeutic level with the single-spin method. After platelet-rich plasma separation, a red blood cell “button” appears at the bottom of the test tube, followed by a thin buffy coat layer just above, and clear yellow platelet-poor plasma. The concentrated platelets are located in the red blood cell button, in the buffy coat, and in the bottommost few milliliters of the plasma fraction (Fig. 1).Fig. 1.: Platelet-rich plasma, a red blood cell “button,” buffy coat, and platelet-poor plasma.It has been shown that a concentration of approximately 1 million platelets/liter, or approximately four to seven times more than the usual baseline platelet count (i.e., 200,000 platelets/liter) produces clinical benefits. We would like to make the following three points. First, Kurita et al. have produced platelet-rich plasma by the single-spin method.1 However, the double-spin method is preferable in platelet-rich plasma production.2 Second, they have determined that platelet-poor plasma and platelet-rich plasma are prepared by changing the centrifuge speed,1 although platelet-poor plasma is naturally produced by platelet-rich plasma as mentioned earlier.2 Third, we consider that platelet-rich plasma produced by their method might not contain the entire buffy coat layer, which holds a large amount of platelets, because the platelet concentration rate in platelet-rich plasma that they prepared is only 0.75×, and the growth factor is not concentrated at all compared with the whole blood. In platelet-rich plasma production, various automatic separation devices (e.g., Smart PReP, PCCS) have been recommended. However, if there is no device available in the laboratory, it is still possible to produce platelet-rich plasma with condensed platelets by using the manual double-spin method. The platelet concentration rate of platelet-rich plasma obtained by the manual double-spin method in our laboratory was 7.9×.3 Platelet-rich plasma means “abundant platelets that are concentrated into a small volume of plasma.”2 The terms concerning platelet-rich plasma are sometimes used interchangeably in presentations and in the literature, which often confuses the audience. Therefore, we consider that an accurate definition and method of production, which is based on the textbook, should be provided for platelet-rich plasma, and that studies should be conducted by using this method. The textbook for platelet-rich plasma written by Marx has been published in both English and Japanese. We recommend that all researchers dealing with platelet-rich plasma should skim through this book. Natsuko Kakudo, M.D., Ph.D. Satoshi Kushida, M.D. Kenji Kusumoto, M.D., Ph.D. Department of Plastic and Reconstructive Surgery Kansai Medical University Osaka, Japan