5. Platelet-rich plasma (PRP)

Growth factor Function in wound healing

and angiogenesis

endothelial cells

matrix synthesis, and epithelization

• Chemoattractant for neutrophils

proliferation of BM progenitor cells Insulin-like growth factor (IGF) • Growth factors for normal fibroblasts, promotes the synthesis of collagenase and prostaglandin E2 in fibroblasts

Interleukin-1b (IL-1b) • Activates osteoclasts in high concentrations and suppresses the formation of

growth of endothelial cells and hepatocytes

• Most potent GF for skin keratinocytes

Platelet-derived growth factor (PDGF) • Activates TGF-b and stimulates neutrophils, macrophages, and mitosis of

collagen and release of calcium • More potent than EGF

metabolism of joint cartilage

Interleukin-8 (IL-8) • Stimulates mitosis of epidermal cells and supports angiogenesis

cell migration

angiogenesis

osteogenesis

Tumor necrosis factor alpha (TNFa) • Growth factor for fibroblasts and promotes angiogenesis

macrovascular endothelial cells

collagen types 1, 2, and 3

cells

keratinocytes, and chondrocytes

• Proliferation, migration, and tube formation of vascular endothelial cells

• Proliferation and differentiation of osteoblasts and matrix mineralization

• Participates in proliferation, differentiation, angiogenesis, and cell migration

• Growth of fibroblasts, myoblasts, osteoblasts, neural cells, endothelial cells,

• Participates in the proliferation and differentiation of osteoblasts and in the

• Induces collagen and matrix synthesis by bone cells, regulating the

the new bone. In low concentrations, however, promotes new bone growth • Enhances inflammatory reactions and collagenase activity and inhibits the

• Promotes wound healing via proliferation, differentiation, angiogenesis, and

fibroblasts and smooth muscle cells, collagen synthesis, collagenase activity, and

• Chemoattractant for hematopoietic and mesenchymal cells, fibroblasts, and

• Promotes the generation of osteoblasts and deposition of bone matrix during

muscle cells. Stimulates chemotaxis toward a gradient of PDGF

• Affects bone formation and remodeling by inhibition of synthesis of

• Stimulates mesenchymal, epithelial, and endothelial cell growth. Endothelial chemotaxis controls the epidermal development

• Induces neovascularization by stimulating the proliferation of

cells, hematopoietic cell types, and keratinocyte

• Fibroblast chemotaxis, proliferation, and stimulates collagen synthesis • Growth inhibitor for epithelial and endothelial cells, fibroblasts, neuronal

• Stimulates the synthesis of metalloproteinase that helps degrade interstitial

• Stimulates mitosis of epithelial cells except for fibroblasts and endothelial

• Promotes angiogenesis, endothelial cell proliferation, collagen synthesis,

• Promotes skin-derived keratinocytes, dermal fibroblasts, and vascular

Connective tissue growth factor

90 Hot Topics in Burn Injuries

aFGF or FGF-1 (fibroblast growth

bFGF or FGF-2 (fibroblast growth

GM-CDF or CSF a (granulocyte/ macrophage colony-stimulating factor)

Keratinocyte growth factor (KGF or

Transforming growth factor alpha

Transforming growth factor beta

Vascular endothelial growth factor

Table 1. Growth factors in platelet and their function.

(CTGF)

factor; acidic)

factor; basic)

FGF-7)

(TGF-a)

(TGF-b1)

(VEGF/VEP)

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

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 effect.

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


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


Table 3. Platelets of the whole blood and PRP.


granules in the platelets, PRP must be activated. For this purpose, most commonly, 1000 units of topical bovine thrombin per milliliter of 10% calcium chloride solution is added to the

There are studies evaluating the effects of PRP on wound healing (Table 5) [37, 46, 47]. In the early phase of wound healing, the clot formed in the injury area serves as a matrix for cell migration, and this phase is primarily effected by platelets. Platelets contain over 1100 proteins, including growth factors, immune system mediators, enzymes, enzyme inhibitors, and bioactive compounds involved in the wound healing process. PRP contains important growth

PRP was sprayed on the wound

The cavity was completely filled with PRP 24/36 h after surgery and covered with Vaseline gas

Application of PRP gel once

PRP is sprayed during wound

Application on the wound of PG on postoperative days 4 and 12

Application on the wound bed on postoperative days 0 and 7

Application of PRP on the sternum, on the subcutaneous tissue, and on

the wound edges

No difference for the infection rate and

Platelet-Rich Plasma in Burn Treatment http://dx.doi.org/10.5772/intechopen.70835 93

Significant difference for the test group on a pain relief scale and regarding the time to

Significant difference for the test group regarding the time before reconstructive

Significant difference for the test group regarding the complete healing time and

regarding epithelialization at the tenth day

regarding epithelialization at day 7 but not

Significant difference for the test group

No difference regarding the saphenous vein harvest site infection rate Significant difference for the test group regarding chest and leg excessive drainage

regarding chest infection

Significant difference for test group regarding the healing time

No difference for the infection rate

cosmetic scale

return to work

quality of life

Application on the wound Significant difference for the test group

Application on the wound No difference regarding the healing rate

Application on the wound Significant difference for the test group

at day 28

surgery by skin graft

No healing time difference

Name Type of wound Method of use Results

weekly

closure

before closure

platelet-rich plasma [16, 34, 39, 45].

6. PRP in wound healing

Saphenous vein harvest

Acute limb soft tissue

Surgical incisions for vascular surgery

Surgical excision of pilonidal sinus left opened for secondary

2.5 cm skin wounds

Full-thickness 6 mm punch wounds

Sternal closure and saphenous vein harvest

Table 5. Some studies using PRP for wound healing.

site

Bahar et al. Acute pilonidal abscess surgical site

wounds

healing

Han et al. Full-thickness 5 mm punch wounds

Hom et al. Full-thickness 4 mm punch wounds

Lee et al. Full-thickness 2.5

site

Almdahl et al.

Kazakos et al.

Lawlor et al.

Spyridakis et al.

Molina-Minafio et al.

Khalafi et al.

Table 4. Levels of some growth factors in blood versus PRP.

PRP acts through the degradation of alpha granules in the platelets. Secretion of growth factors begins from alpha granules within 10 min after clotting and more than 95% of the presynthesized growth factors secreted within 1 hour. In practice, after the PRP is prepared, it is necessary to induce the alpha granules in platelets for the release of growth factors. This induction is made by adding calcium and/or thrombin into PRP prepared in vitro. For this reason, the PRP should be prepared without clotting and should be applied within 10 minutes after clot initiation [9]. Basically, PRP is acquired by centrifuging autologous blood at a certain cycle. To keep the integrity of platelet membrane, acid citrate dextrose type A is used as anticoagulant agent [38].

While preparing the PRP, common points in clinical preparation techniques are like that: The blood is collected from the patient and is taken into the tube containing anticoagulant agent, and immediately centrifuge operation is initiated. When blood containing anticoagulant agent is centrifuged, three layers form as a result of the density: the deep layer containing red blood cells (gravity, 1.09), the middle layer containing white blood cells and platelets (buffy coat; gravity, 1.06), and the top layer (platelet poor plasma; gravity, 1.03) [11].

In the second stage, different techniques are applied, but basically, acellular plasma layer and the red cell layer are removed, and only "buffy coat" layer which contains dense platelet and white blood cells is obtained. So, the PRP becomes ready to be applied after addition of calcium and/or thrombin to activate thrombocytes [9].

Additionally, approximately 6 ml of platelet-rich plasma can be produced from 45 to 60 ml of blood thanks to newly developed small, compact office systems [14, 21, 39–41]. Numerous of such systems are available in use, including the PCCS (Implant Innovations, Inc., Palm Beach Gardens, Fla.), the Symphony II (DePuy, Warsaw, Ind.), the GPS (Biomet, Warsaw, Ind.), the Magellan (Medtronic, Minneapolis, Minn.), and the SmartPReP (Harvest Technologies Corp., Norwell, Mass.). Though, all these systems work on a small volume of obtained blood (45–60 ml) and on the principle of centrifugation, they have many differences in their capacity to collect and concentrate platelets, with about 30–85% of the available platelets collected and from a less than twofold to an approximately eightfold rise in the concentration of platelets over baseline [15, 30, 33, 35, 40, 42].

Although it is possible to produce PRP by using standard laboratory centrifuge, this process needs much effort, usually requiring multiple transfers and two spins; therefore, it may be difficult to maintain the sterility [14, 31, 43]. Moreover, these techniques may not be reliable to maximize platelet concentration or the levels of key secretory proteins [21].

PRP is stable, in the anticoagulated state, for up to 8 h after preparation. This duration allows to be used even during long operations [14, 21, 44]. In order to release the contents of alpha granules in the platelets, PRP must be activated. For this purpose, most commonly, 1000 units of topical bovine thrombin per milliliter of 10% calcium chloride solution is added to the platelet-rich plasma [16, 34, 39, 45].
