Participation of Cytokines and Growth Factors in Biliary Epithelial Proliferation and Mito-Inhibition during Ductular Reactions
Hepatic reactions to injury are an attempt to maintain functionality and regain homeostasis while adapting to a change in the liver environment. Most reactions involve proliferation and apoptosis of hepatocytes, biliary epithelial cells (BEC), and stromal, hematolymphoid, and endothelial cells. Ductular reactions are also usually accompanied by periductal inflammation, which might be the underlying cause of the reaction, or merely contribute to local tissue damage. Regardless, once homeostasis is disrupted, cytokines and growth factors released by inflammatory, stromal, BEC, and hepatocytes exert various mitogenic, mito-inhibitory, pro- or anti-apoptotic influences on the BEC. The BEC assimilates these various environmental signals and determines the appropriate response by remaining in G0, entering the cell cycle or undergoing apoptosis. These same cytokines and growth factors may or may not have the same effect on normal BEC in an intact liver, or on reactive BEC under different circumstances.