Credit: Hiroyasu Nakano
In response to various injuries, TGFb is released from different types of cells, such as macrophages engulfing apoptotic hepatocytes. Then, TGFb induces the production of FGF18 in HSCs and hepatocytes. FGF18 then stimulates the proliferation of HSCs. Proliferating HSCs further respond to stimuli derived from scar-associated macrophages and produce collagens and extracellular matrix, thereby promoting liver fibrosis. aHSCs, activated HSCs; PDGF, platelet-derived growth factor; qHSCs, quiescent HSCs; SAMacs, scar-associated macrophages.