The state of the art and future of PRP therapy

This series of state of the art mini-reviews focuses on the increasingly popular and topical subject of Platelet-rich plasma (PRP) therapy. In the last few years, there has been a significant increase in the number of manuscript submissions related to PRP therapy to scientific journals including Platelets. Despite many efforts to improve standardization, few well-designed clinical trials have been performed and the preparation, quality and contents of platelet preparations in most studies are not often fully defined [1–6]. Our recent new editorial policy and recent guidelines highlight this with the goal of addressing and improving the quality of the science and submitted manuscripts to journals including Platelets related to PRP [7]. PRP is defined as an autologous or allogeneic derivative of whole blood containing a supra-physiological concentration of platelets [8]. PRP therapy is becoming increasingly popular in regenerative medicine and can be easily and safely prepared from relatively low volumes of blood. Autologous preparations are the preferred choice for most therapies to reduce the risk of infection and immunological reactions. PRP has therefore now gained a huge profile in scientific literature and popular media as a natural regenerative therapy with many potential diverse clinical applications [4,9]. The global market in PRP therapy is estimated to be worth 5 USD billion in 2025 with an annual growth rate of 12.5% [10]. Allogeneic platelet concentrates prepared by blood banks are normally used for transfusions but are also increasingly used for regenerative medicine. They also have the advantage that they are prepared only from healthy donors (typical high counts between 0.8 and 1.6 x 10/L) and produced under Good Manufacturing Practice (GMP) regulations [11]. As regulatory authorities now discourage the use of fetal bovine serum (FBS), mass produced and standardized off the shelf human platelet lysates manufactured from platelet concentrates are increasingly used as an alternative in cell culture for the preparation of GMP cellular-derived therapies [12]. In this issue, Professor Thierry Burnouf and his colleagues therefore provide an update on “Platelet lysates in human cell propagation” [13]. Furthermore, we include a recent peerreviewed paper from the same group entitled “Extensive characterization of the composition and functional activities of five preparations of human platelet lysates for dedicated clinical uses” [14]. The potential beneficial effects of PRP exerted by producing a local environment for tissue regeneration are supported by in vitro studies that demonstrate many positive effects on wound healing. As platelet α-granules contain a large number of growth factors and cytokines, platelets can therefore play important role(s) in tissue regeneration by regulating angiogenesis, stem cell homing, cell migration, proliferation, and differentiation coupled with the appropriate deposition of matrix proteins [15]. The regenerative clinical potential of PRP has therefore been widely explored within the orthopedic, cosmetic, dermatology, plastic, and general surgical communities for regeneration of injury to bone, cartilage, tendons, joints, skin, eyes, the gut, nervous system and muscle, etc. PRP therapy is now widely used for treating sport injuries, highlighted by its use by a number of high-profile sports personalities [9,16]. PRP is also popular as a beauty or rejuvenation therapy by dermatologists and for treating alopecia. A number of important clinical applications of PRP are therefore presented in this series including articles by a number of distinguished experts in the field including Dr. Peter Everts and colleagues “The use of PRP in Orthopaedic Medicine” [17]; Dr. Eduardo Anitua and colleagues “Platelet Rich Plasma in Oral and Maxillofacial surgery from the perspective of composition” [18]; Dr. Ahmad Reza Farmani and colleagues “Platelet Rich Fibrin in Tissue Engineering – focus on bone regeneration” [19]; and Dr. Paula Oneto and Dr. Julia Etulain “PRP in wound healing applications” [20]. Although many in vitro studies support the theoretical potential of PRP in tissue regeneration [21], the in vivo evidence is often anecdotal and inconclusive [22]. Given the growth of interest, a number of commercial devices are now available for preparing sterile PRP for clinical therapies. As these devices often use different separation principles, the resulting PRP preparations are not standardized and therefore exhibit varying quantities, purity, and quality of the platelets obtained [23]. For example, many products often contain plasma but may sometimes also contain both white and red cells. PRP preparations may also be activated via a variety of methods prior to clinical use and therefore can contain fibrin and released platelet granular proteins which are of course important for their biological efficacy in wound healing. Defining the cellular and bioactive factor contents of different PRP preparations is therefore essential to understand the variables associated with the potential biological activity/efficacy of PRP preparations. Dr. Jeremy Magalon and colleagues therefore provide us with an up-to-date overview of “Technical and biological review of authorized medical devices for plateletrich plasma preparation in the field of regenerative medicine” Correspondence: Paul Harrison Institute of Inflammation and Ageing, University of Birmingham, Birmingham B15 2TT, UK. p.harrison. 1@bham.ac. uk http://www.tandfonline. com/iplt ISSN: 0953-7104 (print), 1369-1635 (electronic)