Stellate cells were first described in the mechanism of liver cirrhosis. In the liver, Ito cells are present as storage cells, which contain lipids such as vitamin A. Ito cells are stellate cells in the liver and can metamorphose into myofibroblasts under various conditions. Myofibroblasts play many roles in inflammatory processes. In the liver, viral infections, such as hepatitis B or C, induce Ito cells and stellate cells into becoming myofibroblasts to proliferate around Glisson's sheath. Stimulated myofibroblasts produce collagen fibers to form fibrosis in the liver. In the skin, lung, prostate gland and many other organs, the fibrotic process, i.e. wound healing, is associated with myofibroblasts. In the pancreas, stellate cells are present around the lobules and/or pancreatic ducts. They can transform into activated myofibroblasts. Myofibroblasts are smooth-muscle-like fibroblasts. Immunohistochemically, myofibroblasts are characterized by immunopositivities for a-smooth muscle actin (a-SMA), vimentin, desmin, and CD34 . Stellate cells metamorphose into myofi-broblasts in the pancreas as same as in the liver by being induced by various stimulators, such as tumor necrosis factor-alpha (TNF-a), interleukin (IL)-1P, macrophage inflammatory protein (MIP)-1, and IL-8, all of which are inflammatory cytokines or chemokines, as well as transforming growth factor-beta (TGF-P), fibroblast growth factor (FGF), platelet-derived growth factor (PDGF), and insulin-like growth factor (IGF), all of which are associated with increasing cell mobility, proliferation, and differentiation. Myo-fibroblasts are capable of synthesizing collagen types I, III and fibronectin [10-15].
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