Figure 1.

Model of myofibroblast differentiation. Stromal and granulation tissue in vivo contains several cell types, including fibroblasts, characterized by the presence of cortical, but not stress actin, fibers. Upon mechanical tension, transduced by integrins and their associated proteins, such as integrin-linked kinase (ILK), fibroblasts change into protomyofibroblasts, which exhibit actin-containing stress fibers. The joint presence of mechanical stress and transforming growth factor beta (TGF-β) induces transition of protomyofibroblasts into differentiated myofibroblasts. The latter possess contractile properties due, in part, to the formation of robust stress fibers containing α-smooth muscle actin. “?” indicates poorly understood molecular pathways.