Characterization of Insulin-Immunoreactive Cells and Endocrine Cells Within the Duct System of the Adult Human Pancreas

Objective: The adult pancreatic duct system accommodates endocrine cells that have the potential to produce insulin. Here we report the characterization and distribution of insulin-immunoreactive cells and endocrine cells within the ductal units of adult human pancreas. Methods: Sequential pancreas sections from 12 nondiabetic adults were stained with biomarkers of ductal epithelial cells (cytokeratin 19), acinar cells (amylase), endocrine cells (chromogranin A; neuron-specific enolase), islet hormones (insulin, glucagon, somatostatin, pancreatic polypeptide), cell proliferation (Ki-67), and neogenesis (CD29). Results: The number of islet hormone-immunoreactive cells increased from large ducts to the terminal branches. The insulin-producing cells outnumbered endocrine cells reactive for glucagon, somatostatin, or pancreatic polypeptide. The proportions of insulin-immunoreactive count compared with local islets (100% as a baseline) were 1.5% for the main ducts, 7.2% for interlobular ducts, 24.8% for intralobular ducts, 67.9% for intercalated ducts, and 348.9% for centroacinar cells. Both Ki-67-and CD29-labeled cells were predominantly localized in the terminal branches around the islets. The terminal branches also showed cells coexpressing islet hormones and cytokeratin 19. Conclusions: The adult human pancreatic ducts showed islet hormone-producing cells. The insulin-reactive cells predominantly localized in terminal branches where they may retain potential capability for beta-cell neogenesis.