The main mechanism of action of PRP is through platelets, which besides their well-known function in homeostasis, release also factors that promotes angiogenesis and tissue repair [5]. Secretory granules of the platelets contain growth factors, coagulation factors, cytokines, adhesion molecules and integrins. Releasing of the active growth factors is realized through degranulation of alfa granules [1].

The main growth factors included in alfa granules are: platelet derived growth factor (PDGF), platelet derived endothelial growth factor (PDEGF), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), insulin like growth factor (IGF) , platelet derived angiogenesis factor (PDAF), transforming growth factor(TGF), keratinocyte growth factor (KGF), fibroblast growth factor (FGF), connective tissue growth factor (CTGF), tumor necrosis factor alpha (TNF-α), interleukin 1 β (IL 1 β) and interleukin 8 (IL8) [5] .

All these growth factors stimulate healing by attracting cells in the new formed matrix and triggering division of the cells. Another process involved in wound healing might be the role of PRP in suppressing the cytokine release that limits inflammation, and also in interaction with macrophages to promote tissue healing, regeneration and epithelialization [1].

Platelet rich plasma also contains a small quantity of leucocytes which synthesize interleukins and antimicrobial peptides with an antibacterial role [4, 6].

Platelet rich plasma has a safety profile being produced from autologous blood with minimal risks for disease transmission, immunogenic reactions and cancer [7, 8]. Patients who are considered to be candidates for using PRP must undergo a minor hematological evaluation to exclude blood disorders or platelet dysfunction [9].

PRP can be produced very easy using patient’s blood, a centrifuge and an activator formed of thrombin or calcium [10]. Nowadays there are several kits for producing PRP and the process is simple. Apart from injections, PRP might be also use as a gelatinous platelet gel by activation with thrombin or calcium, being easier to use in soft tissue injuries and wounds [11].

Clinically valuable PRP contains approximately one million platelets per microliter, lesser or greater concentrations have not been shown to have better results in improving wound healing [12].

In the last two decades platelet rich plasma was largely used in maxillofacial surgery. Recent developments in research of the regenerative effects of PRP on bones, tendons, cartilage, muscle and skin have attracted interest in fields as orthopedic and plastic surgery [13].

Nowadays PRP has an important use in orthopedic surgery, especially in tendon injuries accelerating tendon healing through growth factors [14], even though there are some studies that show no improvement in arthroscopic rotator cuff repair [15], in tendinopathies or muscle injuries [16, 17]. PRP action in tendon injuries might be explained through the higher concentrations of VEGF which stimulates angiogenesis and tendon vascularization. Furthermore, leucocytes stimulate macrophage migration and reduce tissue inflammation. PRP plays also a therapeutic role for cartilage pathology, especially in conservative treatment of cartilage degenerative lesions and osteoarthritis [18, 19].

Apart from the important use in orthopedic and trauma surgery, platelet rich plasma plays an important role in plastic surgery as an adjuvant therapy for chronic, diabetic and pressure ulcers. Some studies showed a benefic action of PRP applied on ulcers. For example, a retrospective cohort study showed that PRP improves healing in severe diabetic neuropathic ulcers compared with standard of care [20, 21]. Another paper described improvement in healing a patient with a diabetic ulcer that failed to heal using other treatment modalities [22]. Two studies involving patients with chronic ulcers showed that PRP improves local vascularization and promotes epithelization [23, 24].

Studying the way of action, it has been shown that PRP stimulates the activity of keratinocytes, cells with important roles in epithelization during the healing processes [4]. This effect improved epithelization not only in acute wounds, but also in chronic wounds or burns. Treatment of pressure ulcers was also improved by PRP compared with classical saline solution, minimizing complications and the time of healing [25]. Regarding soft tissues defects, PRP plays an important role in diminishing edema, ecchymosis, bacterial load through its antibacterial and anti- inflammatory proprieties, reducing infections and additional complications [5].

The sustained release of large quantities of growth factors, cytokines, and other mediators found in platelet rich plasma may help in stimulating wound healing and resolving chronic inflammation [1]

Not all studies support the use of PRP in wound healing. For example, two studies from 1991 and 2002 showed no significant improvement in diabetic foot ulcerations in comparison with classical treatment [26, 27].

PRP is used as an adjuvant therapy for chronic wounds. The most important steps in wound healing are debridement, offloading and frequent dressing changes, procedures that transform a chronic wound into an acute wound [1].

Debridement represents an important step, removing all the devitalized and necrotic tissues, reducing also the bacterial load, and leaving a healthy tissue [21]. It is also important to eliminate other factors which impede healing like pressure, friction and sheer. After preparing the wound bed, PRP is applied as a gel or injected in the wound [1].

Even though studies showed that PRP brings an improvement in orthopedic treatments and wound healing it is difficult to compare its efficacy in multiple studies due to additional factors. The composition of PRP is different for every patient, for every device involved in preparation, including the time and method of storage and the interaction with other materials [7].

Further studies are required to optimize its preparation and use, and to evaluate the best effective technique of using it to improve healing.