Abstract
The hepatic stellate cells reside in the Disse's space of hepatic sinusoids. They are the center of retinol metabolism in the liver in physiological situation. When liver injuries occur, they undergo activation or transformation and exhibit the characteristic of myofibroblasts in the other organs. Activated stellate cells generate extracel-lular matrix materials, growth factors such as TGF beta, and their contractility in creases the rigidity of sinusoids and disturbs microcirculation. Thus, the activated cells play multiple roles in the development of liver fibrogenesis. PDGF, which derives from local inflammatory sites, is the strongest mitogen for the activated stellate cells whose PDGF receptor beta are fully induced. Besides classical MAP kinase cascade, PI3-kinase-and Akt-dependent signals are found to be essential in the expression of Gl cyclins and the resulting transition to S phase and cell proliferation.
