الفهرس 
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Abstract
Platelet-rich plasma (PRP) is an autologous biomaterial obtained by centrifuging whole blood. PRP may be defined as a fraction of autologous plasma with platelet concentration above baseline level. Studies have shown that ideal concentration is at least a fourfold increase in initial concentration, or around 1,000,000/mm3 (Marx et al.,2005)
Essentially, there are 2 main types of PRP produced. The first is from the plasma layer. It aims to exclude red and white cells from the preparation and to collect as many platelets from the remaining ‘‘plasma’’ layer as possible. The resultant product is low in red and white cells and has a low level of platelets (1.5 to 3 times baseline levels). The second type of product is made from the buffy coat layer. It aims to take platelets from both the plasma and the cellular layer and thus is generally much higher in platelet count, yielding approximately 3 to 8 times the baseline level of platelets (Fitzpatrick et al., 2017)
Many of the cytokines and growth factors are believed to be responsible for the effects of PRP, are contained within the α-granules of platelets .Platelet activation triggers degranulation and release of these growth factors. The timing and cumulative release of growth factors is determined by the activation method but may continue throughout the platelet’s 8–10 day lifespan (Foster et al., 2009)
Multiple studies have demonstrated a role for platelet-rich plasma (PRP) in accelerating and facilitating response to injury. The cellular response to injury progresses through four general stages: hemostasis, inflammation, proliferation, and finally remodeling. Each phase is characterized by enhanced cellular or molecular activity, all of which involve platelets. Blood plasma and platelets are responsible for hemostasis, while leukocytes and activated platelets mediate inflammation, and growth factors derived from platelet α-granules influence tissue regeneration. Specifically, the leukocyte content of PRP is thought influence the inflammatory phase (Rozman et al., 2007)
Given what is found in PRP, it has been used for many applications, from cosmetics to wound healing to treating pain conditions. Theoretically, PRP should work well on any soft tissue structure (such as ligaments, tendons, or cartilage) that needs help in healing. It has been reported that musculoskeletal injuries are the most common cause of long-term pain and physical disability (Woolf et al., 2003)
The medical field is advancing towards the development of less-invasive and cost-effective treatments to enhance functional recovery. The use of PRP has had a potential impact in reducing economic costs for standard medical treatments, although it should not be considered as a therapy that replaces certain essential conventional treatments, such as debridement of necrotized tissue, but as a complementary therapy (Anitua et al., 2007).