Apoptosis and myofibroblasts in the pathogenesis of systemic sclerosis.

Tissue fibrosis is the result of a complex series of events focusing on regulation of fibroblast proliferation, synthesis of extracellular matrix, and apoptosis. Transforming growth factor-beta is important for the stimulation of the fibrotic response by promoting the production of extracellular matrix proteins, by promoting the differentiation of the myofibroblast cell morphology, and by protecting these cells against apoptotic stimuli. Other cytokines such as interleukin-1 may have stimulatory and counter-regulatory effects on fibrosis. The effects of these signaling molecules depend on cellular environment and are organ specific. Furthermore, intercellular interactions and cell-matrix interactions can stimulate or inhibit the apoptotic pathway. Through selective inhibition of apoptosis in myofibroblasts, fibrosis can become dysregulated and lead to diseases such as systemic sclerosis.