Plasma

Fig. 25.1

Platelet physiology. Platelets are not cells, but rather 1–4 μm anucleated cytoplasmic fragments of megakaryocytes. Platelets contain dense granules and alpha granules. The latter contain adhesion molecules, coagulation and fibrinolytic factors, growth factors, cytokines, antibacterial proteins, and other factors, totaling more than 1000. These factors are released with platelet activation as shown on the schematics. ∗AG – Alpha granules, DG – Dense granules, PDGF – Platelet-derived growth factor, IGF-1 – Insulin-like growth factor-1, TGF-b1 – Transforming growth factor beta-1, CTGF – Connective tissue growth factor, VEGF – Vascular endothelial growth factor, b-FGF – Basic fibroblastic growth factor, EGF – Epidermal growth factor

Table 25.1

Platelet-rich plasma proteins

Biologically active proteins released from platelet-rich plasma and their effects on tissue repair
Platelet-derived growth factor (PDGF) – fibroblast production, chemotaxis, collagen production
Insulin-like growth factor-1 (IGF-1) – cell growth, differentiation
Transforming growth factor beta-1 (TGF-b1) angiogenesis, extracellular matrix formation, cell viability
Connective tissue growth factor (CTGF) – connective tissue growth
Vascular endothelial growth factor (VEGF) – new blood vessel growth and anti-apoptosis of blood vessel cells
Fibroblastic growth factor (b-FGF) – tissue repair, collagen production, myoblast proliferation
Epidermal growth factor (EGF) – cell recruitment, proliferation, differentiation, promotion of epithelial cells

../images/457420_1_En_25_Chapter/457420_1_En_25_Fig2_HTML.png — Fig. 25.2

Typical pattern of healing. An initial reaction to injury starts immediately with hemostasis. The inflammatory phase followed by proliferation and then remodeling. The healing of tissue may last more than a year

../images/457420_1_En_25_Chapter/457420_1_En_25_Fig3_HTML.png — Fig. 25.3

Why use platelet-rich plasma (PRP)? The normal or physiologic platelet concentration in blood is 150–450,00 per μL. It is characteristically three to eight times greater in the PRP. Subsequently, the concentration of growth factors and other signaling molecules is significantly higher, which may potentially explain some of the mechanisms of accelerated tissue regeneration with platelet-rich plasma application. PRP seems to produce simultaneous anti-inflammatory and pro-inflammatory effects, which diverge it from corticosteroids, widely used to hold up inflammatory cascade, and from prolotherapy, which typically aggravates inflammatory reaction after its injection

The mechanisms of effects of PRP on repair are complex but appear to resemble a typical pattern of healing, facilitated with PRP (Figs. 25.2 and 25.3). There are a number of factors, producing impact on its effect, including volume of blood used for PRP preparation, PRP concentration, use of anticoagulant during PRP preparation, platelet count, white blood cell (WBC) count, type of injury or disease, PRP equipment used, number of PRP injections, interval between PRP injections, and many others (Table 25.2). The recent studies suggest that the release of PRP growth factors may be dependent on such remote factors and the microbiota and immune status of the host.

Table 25.2

Factors influencing platelet-rich plasma effect

Factors affecting PRP injection outcomes
Volume of blood used for PRP preparation
PRP concentration
Use of anticoagulant
Pre-procedure platelet count
WBC count
Type of injury or disease treated with PRP
Equipment used in PRP preparation
Number of PRP injections
Interval between PRP injections
Host microbiota
Host immune status
Others