Pancreatic duct obstruction itself induces expression of alpha smooth muscle actin in pancreatic stellate cells
Pancreatic stellate cells (PSCs) are thought to be responsible for pancreatic fibrosis. Although fibrosis is a major characteristic of chronic pancreatitis (CP) induced by pancreatic duct obstruction, it is unclear whether pancreatic duct obstruction itself activates PSCs. To test the hypothesis that pancreatic duct obstruction activates PSCs, clinical and experimental analyses were performed using alpha smooth muscle actin (alpha-SMA) as a marker of their activation. In clinical analysis, surgical specimens from the patients with pancreatic cancer or cancer of the papilla Vater were classified into two groups with or without duct obstruction. alpha-SMA expression was examined on these specimens, and the difference between two groups was evaluated. In animal experiment, duct ligation-induced pancreatitis was developed in rats by ligating the secondary pancreatic duct in duodenal segment, and the expression of alpha-SMA was examined. In clinical analysis, the specimens from the pancreas with duct obstruction (14 cases) expressed alpha-SMA significantly stronger than those from the pancreas without duct obstruction (7 cases). All specimens in the former expressed alpha-SMA, but 4 specimens from the latter did not at all (P < 0.05). In animal experiment, alpha-SMA expression was detected 7 days after the ligation and was increased on the 10th day. We can assume that pancreatic duct obstruction itself activates PSCs. This mechanism may play roles in the development of CP from multiple origins.