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Journal of Oral Science & Rehabilitation Volume 2 | Issue 2/2016 43 C o m p o s i t i o n o f P R P Introduction Tissue integrity and blood vessel repair are es- sential after destructive and reconstructive events,suchassurgery,traumaandregenerative procedures. The seeking for and identification of reliableandsafetechniquesortherapeuticmeth- ods that would predictably enhance the regen- erative capacity in damaged tissue has become amajorfocusofcurrentresearch.Alargenumber of cells are involved in wound healing, including platelets, which play a crucial role in controlling coagulation and releasing growth factors and cytokines related to tissue regeneration. Plate- let-derived products isolated from the patient’s own blood have been extensively studied and tested because platelets are considered a source of cytokines and growth factors, which amplify wound healing and tissue repair.1 Platelet-rich plasma (PRP) offers much po- tential owing to its autogenous nature and a supposed molecular content. PRPwas originally defined as a product with a high concentration ofplatelets,obtainedfromautologousblood,that contains different growth factors that may po- tentiallyinfluencecellsinvolvedinwoundhealing and bone regeneration.2 Besides its adhesive and hemostatic properties, from a biological stand- point, the rationale for the use of PRP is rooted in the idea that regenerative advantages are ob- tained afterthe application ofthis product, given the modulating activity that is supposed to be exerted by molecules released from the ƴ-gra- nules, which are stored in the cytoplasm of pla- telets.3, 4 A wide variety of molecules with diffe- rent biological roles are known to be contained inthe different platelet granules, such as seroto- nin, coagulation factors, proteoglycans, mem- brane-associated proteins and different types of proteases.1, 5 However, some researchers believe that the activity of specific mitogenic/growth factors, concretelystored inthe ƴ-granules, is of major importance in regenerative events.6, 7 Growth factors, including those that have been classically associated with PRP, are included in a family of polypeptides of low molecular weight with a very short life span. Growth factors can modulate cell behavior, alter gene expression of target cells and ultimately lead to promotion of cell migration, proliferation, differentiation and eventually maturation.8 The growth factors that have been reportedto be in PRPincludevascular endothelial growth factor (VEGF), platelet-deri- ved growth factor (PDGF), transforming growth factor-beta (TGF-ʹ1), fibroblast growth factor (FGF), insulin-like growth factor-1 (IGF-1) and epidermal growth factor (EGF).2, 6, 9 When PRPwas introduced in dentistry, most of the knowledge that justified its attributed regenerative potential came from experimental animal models10, 11 and several human case re- ports.12–15 Nowadays, clinicaltrials conducted to assess the clinical validity of PRP have shown controversial results, many of them advocating for no significant effect when PRP is used alone.16–18 However, it has been reportedthatthe addition of PRP to bone substitutes promotes enhancement of osseointegration of dental im- plants, optimizing the expansion of new bone cells, and improvement of the aggregation and cohesiveness of particulate-based bone substi- tutes.19, 20 In orderto understand howPRPworks, it is important to know its structure and mole- cular composition.21 It is important to know whether the described factors are present in an amountthat can be easilydetectable and inwhat proportion of the population. However, only li- mited evidence is currently available. Hence, it was the aim of this study to conduct a qualita- tive analysis to screen the molecular composi- tion of PRP. Materials and methods P r e p a r a t i o n o f P R P Venous bloodwas obtainedfrom 20 healthyvol- unteers (16 males and fourfemales; mean age of 27.4), who gave their informed consent and met the following inclusion criteria after a complete medical history recording and examination: no medication taken in the last two weeks, no dentalorintra-oralsurgicaltreatmentwithinthe last month, and no vaccine received and no in- fection history within the last three months. Briefly, 20cm3 of blood was drawn per patient and 5cm3 placed into each of four Vacutainer tubes (Becton Dickinson, Oxford, U.K.), which contained 0.1cm3 of 3.8% (w/v) sodium citrate. In order to minimize platelet activation during bloodcollection,a19-gaugebutterflyneedlewith a light tourniquet was used and the first 2mL of blood was discarded. For the preparation of the PRP,amodificationoftheoriginalprocedurepro- posed byAnitua in 1999wasfollowed.4 Immedi- ately after collection, the tubes were placed in a centrifugemachinetospinat1,500rpmfor7min Volume 2 | Issue 2/201643