Pancreatic stellate cells--multi-functional cells in the pancreas.

There is accumulating evidence that activated pancreatic stellate cells (PSCs) play a pivotal role in pancreatic fibrosis in chronic pancreatitis and pancreatic cancer. In addition, we have seen great progress in our understanding of the cell biology of PSCs and the interactions between PSCs and other cell types in the pancreas. In response to pancreatic injury or inflammation, quiescent PSCs are activated to myofibroblast-like cells. Recent studies have shown that the activation of intracellular signaling pathways such as mitogen-activated protein kinases plays a role in the activation of PSCs. microRNAs might also play a role, because the microRNA expression profiles are dramatically altered in the process of activation. In addition to producing extracellular matrix components such as type I collagen, PSCs have a wide variety of cell functions related to local immunity, inflammation, angiogenesis, and exocrine and endocrine functions in the pancreas. From this point of view, the interactions between PSCs and other cell types such as pancreatic exocrine cells, endocrine cells, and cancer cells have attracted increasing attention of researchers. PSCs might regulate exocrine functions in the pancreas through the cholecystokinin-induced release of acetylcholine. PSCs induce apoptosis and decrease insulin expression in β-cells, suggesting a novel mechanism of diabetes in diseased pancreas. PSCs promote the progression of pancreatic cancer by multiple mechanisms. Recent studies have shown that PSCs induce epithelial-mesenchymal transition and enhance the stem-cell like features of pancreatic cancer cells. In conclusion, PSCs should now be recognized as not only profibrogenic cells but as multi-functional cells in the pancreas.