MECHANISMS AND FACTORS INVOLVED IN DEVELOPMENT OF HYPERTROPHIC SCARS

Fibroblasts in granulation tissue (myofibroblasts) develop several ult rastructural and biochemical features of smooth muscle cells, such as the presence of microfilament bundles and the expression of alpha-smoo th muscle actin. The mechanisms leading to the development of such myo fibroblastic features remain unclear. Both in vivo and in vitro invest igations suggest the participation of growth factors, cytokines, and e xtracellular matrix in the regulation of alpha-smooth muscle actin exp ression. During normal wound healing, myofibroblasts disappear when th e wound is fully re-epithelialized. In contrast, the expression of alp ha-smooth muscle actin is a permanent feature of myofibroblasts presen t in fibrocontractive diseases. In hypertrophic scars, the presence of these cells may represent an important element in the pathogenesis of retraction. Different therapeutic modalities available for the treatm ent of hypertrophic scars cause a decrease in the number of alpha-smoo th muscle actin expressing myofibroblasts. Further studies regarding t he expression of cytoskeleton markers in fibroblastic cells are needed to understand the mechanisms of scarring and fibrosis.