Joost Peerbooms

54 Chapter 4 Table 1 Function of Growth Factors Within Platelet-Rich Plasma PDGF, platelet-derived growth factor; TGF, transforming growth factor; IGF, insulin-like growth factor; VEGF, vascular endothelial growth factor CELLULAR EVIDENCE FOR PRP The three general stages of healing (wound, bone, tendon) are inflammation, proliferation and remodelling. The inflammatory phase begins with tissue injury. Platelets are then stimulated to release growth factors, cytokines and haemostatic factors which are required in the initial phase of the clotting process. Histamine and serotonin are issued by the platelets. Both increase capillary permeability, thus improving accessibility to the inflammatory cells to the wound surface and the activation of macrophages. Polymorphonucleaire leukocytes migrate into the tissue where the inflammation occurs. Soon, the cells begin to proliferate, and fibroblasts form a base substance. Activation of adenosine receptor promotes the inflammatory process during wound healing. 7 Repetitive use of the tendon can lead to changes in the collagen fibre matrix predisposing the tendons to microtears and scarring, affecting functionality and increasing risk for re-injury. In chronic conditions, histologically, there is no further inflammatory response seen. It is a degenerative condition, affecting the metabolic and healing process in a negative manner, and prolonging their chronicities. 8,9