Early provisional matrix is primarily composed of fibrin. Fibrin interacts with macrophage-1 antigen (Mac-1) to upregulate proinflammatory cytokines that signal to resident and invading immune cells as well as stromal cell populations. The degradation products of fibrin play a key role in angiogenesis, leading to persistent activation of the coagulation cascade and promoting fibrin persistence. Increases in fibronectin indicate a shift to late provisional extracellular matrix (ECM) and serve as scaffolding for growth factors and mechanical signaling. At this stage, an increasingly stiff ECM serves as a template for collagen (Col) deposition. Finally, mature ECM is characterized by increased density of type I collagen as well as the ability to resist degradation and repetitive mechanical stress. FN, fibronectin; MIP-2, macrophage inhibitory protein-2; PAI-1, plasminogen activator inhibitor-1.