Matrix metalloproteinases in wound repair (review).

Wound repair is initiated with the aggregation of platelets, formation of a fibrin clot, and release of growth factors from the activated coagulation pathways, injured cells, platelets, and extracellular matrix (ECM), followed by migration of inflammatory cells to the wound site. Thereafter, keratinocytes migrate over the wound, angiogenesis is initiated, and fibroblasts deposit and remodel the granulation tissue. Cell migration, angiogenesis, degradation of provisional matrix, and remodeling of newly formed granulation tissue, all require controlled degradation of the ECM. Disturbance in the balance between ECM production and degradation leads to formation of chronic ulcers with excessive ECM degradation, or to fibrosis, for example hypertrophic scars or keloids characterized by excessive accumulation of ECM components. Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases, which as a group can degrade essentially all ECM components. So far, 20 members of the human MMP family have been identified. Based on their structure and substrate specificity, they can be divided into subgroups of collagenases, stromelysins, stromelysin-like MMPs, gelatinases, membrane-type MMPs (MT-MMPs), and other MMPs. In this review, the role of MMPs in normal wound repair as well as in chronic ulcers is discussed. In addition, the role of signaling pathways, in particular, mitogen-activated protein kinases (MAPKs) in regulating MMP expression is discussed as possible therapeutical targets for wound healing disorders.