4. Roles of platelets in wound healing

A lot of proteins are found within the alpha granules of platelets that strongly influence wound healing process, including transforming growth factor (TGF)-beta, platelet-derived growth factor (PDGF), platelet-derived endothelial growth factor (PDEGF), platelet-derived angiogenesis


factor (PDAF), platelet factor 4 (PF4), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), epithelial cell growth factor (ECGF), insulin-like growth factor (IGF), interleukin (IL)-1, osteocalcin, osteonectin, vitronectin, fibrinogen, fibronectin, and thrombospondin (TSP)-1 [8, 11, 13, 16, 20, 21, 23, 24]. Collectively, these proteins mentioned are members of the growth factor, cytokine, and chemokine families. Each of these proteins takes a position in different steps of wound healing (Table 1) [9, 21]. Platelets begin to actively secrete these mediators within 10 minutes after clotting, and more than 95% of these presynthesized

Platelet-Rich Plasma in Burn Treatment http://dx.doi.org/10.5772/intechopen.70835 91

As a general definition, PRP is the concentration of autologous human platelets in a small amount of plasma. There are many different names, types, and PRP-like products (Table 2)

Some investigators have suggested that the platelet concentration in PRP should be at least 3–5 times the normal platelet concentration in the blood (Table 3) [29–32], although the dependence of clinical benefit on platelet concentration versus total number of platelets delivered may need to await further investigation [33]. Platelet concentration ratios of less than twofold to 8.5-fold have been reported [21, 29–31, 34–36]. Weibrich et al. [24] recommend that different individuals may need different platelet concentration ratios to obtain comparable biological

PRP comprises not only high levels of platelets but also all components of clotting factors. For PRP to be clinically effective, it is emphasized that each 1 microliter of PRP should have at least

Platelet-rich plasma (PRP) Nonactivated plasma with amount of platelets above baseline

Platelet lysate Activated PRP by lyses, e.g., by freeze-thawing or Triton-X

/L) 519.6 214.3

/L) 2139.3 1401.6

Platelet releasate Activated PRP by thrombin and calcium chloride

Ratio thrombocytes PRP/baseline whole blood 3.9 1.8

Platelet-rich fibrin (PRF) Platelet-rich product with 3D structure

Plasma rich in growth factors Type of pure PRP, no leukocytes

growth factors are secreted within 1 h [9, 21].

[2–28]. PRP was first described by Marx et al. [2–28].

1,000,000 thrombocytes. (Tables 3 and 4) [29–32, 37].

Platelet concentrate Platelet-rich plasma

Platelet gel Activated PRP

Table 2. An overview of different names, types, and PRP-like products.

Thrombocytes baseline whole blood (<sup>10</sup><sup>9</sup>

Table 3. Platelets of the whole blood and PRP.

Thrombocytes PRP (<sup>10</sup><sup>9</sup>

5. Platelet-rich plasma (PRP)

effect.

Table 1. Growth factors in platelet and their function.

factor (PDAF), platelet factor 4 (PF4), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), epithelial cell growth factor (ECGF), insulin-like growth factor (IGF), interleukin (IL)-1, osteocalcin, osteonectin, vitronectin, fibrinogen, fibronectin, and thrombospondin (TSP)-1 [8, 11, 13, 16, 20, 21, 23, 24]. Collectively, these proteins mentioned are members of the growth factor, cytokine, and chemokine families. Each of these proteins takes a position in different steps of wound healing (Table 1) [9, 21]. Platelets begin to actively secrete these mediators within 10 minutes after clotting, and more than 95% of these presynthesized growth factors are secreted within 1 h [9, 21].
