The alteration of protease activity is not the only feature of the chronic wound bed
environment.Alterations in many other proteins include decreased levels of intact
fibronectin,increased fibronectin degradation products,loss of type II transforming growth factor-beta (TGF-b) receptors on fibroblasts,reduced levels of platelet-derived growth factor (PDGF) and down-regulation of keratins in epithelial cells.Keratinocytes at the wound edges tend to be hyperproliferative and non-migratory,while fibroblasts in the base of the wound become senescent.