Fibrogenesis in alcoholic chronic pancreatitis: The role of tissue necrosis, macrophages, myofibroblasts and cytokines

Myofibroblasts and cytokines such as transforming growth factor-β1 (TGF-β1) and platelet-derived growth factor (PDGF)-B have been found to play an important role in pancreatitis-associated fibrogenesis. It is still unclear, however, where in the inflamed pancreas and when these fibrogenic cells and cytokines can be detected. In this study we examined pancreatic tissue from patients with alcoholic chronic pancreatitis to determine the localization and distribution of myofibroblasts and the expression of cytokines in relation to the tissue damage and the activity of the inflammatory process. In tissue from pancreatic specimens from 59 patients with alcoholic chronic pancreatitis the inflammatory process was histologically staged. Myofibroblasts and the cytokines latency-associated peptide, a TGF-β propeptide, TGF-β receptor II, PDGF-B and the α-isoform of the PDGF receptor were immunohistochemically identified in 10 selected cases representing the four defined stages of alcoholic chronic pancreatitis. In stage I, the stage with overt tissue injury, myofibroblasts were numerous and especially associated with macrophages around areas of necrosis. In stage II, the stage with cellular fibrosis, myofibroblasts were the main component of the interlobular tissue. In stage III, the stage with dense fibrosis, myofibroblasts were rare, and in stage IV, when calculi were present, myofibroblasts were only detected adjacent to duct ulcerations caused by calculi. Latency-associated peptide and TGF-β receptor II as well as PDGF-B and PDGF receptor-α were mainly expressed by macrophages, myofibroblasts and epithelial cells in stages I and II. The results suggest that the fibrogenic process in alcoholic chronic pancreatitis is initiated by a cytokine-based interplay of macrophages and myofibroblasts that follows tissue injury.