REGULATION OF FIBROPLASIA IN CUTANEOUS WOUND REPAIR

Fibroblast accumulation in a cutaneous wound requires phenotypic modul ation of fibroblasts. In response to injury, resident fibroblasts in t he surrounding tissue proliferate for the first 3 days and then at day 4 migrate into the wounded site. Once within the wound, they produce type I procollagen as well as other matrix molecules and deposit these extracellular matrix molecules in the local milieu. By day 7, abundan t extracellular matrix has accumulated and fibroblasts switch to a myo fibroblast phenotype replete with actin bundles along the cytoplasmic face of the plasma membrane. Wound contraction occurs as these myofibr oblast gather in the wound extracellular matrix by extending pseudopod ia, attaching to extracellular matrix molecules, such as fibronectin a nd collagen, then retracting the pseudopodia. Once these processes hav e been accomplished, the fibroblasts appear to undergo apoptosis. Ther efore, during cutaneous wound repair, fibroblasts appear to progress t hrough four phenotypes: first proliferating, second migrating, third s ynthesizing extracellular matrix molecules, and fourth expressing thic k actin bundles as myofibroblasts.