Topographical associations between islet endocrine cells and duct epithelial cells in the adult human pancreas

Abstract

The pancreatic ducts, endocrine islets and exocrine acini are three functionally related components. From birth to adulthood, the islets and ducts are regarded as independent entities. The objective of this study is to investigate the topographical associations between the islet endocrine cells and duct epithelial cells in the adult human pancreas. Panels of immunomarkers for the exocrine acinar cells (amylase), duct cells [cytokeratin 19 (CK19)], endocrine cells (chromogranin A, neurone specific enolase, synaptophysin) and islet hormones (glucagon, insulin, somatostatin, pancreatic polypeptide) were applied to sequential pancreatic tissue sections obtained from autopsy specimens of 10-nondiabetic human adults. Double immunofluorescent staining with CK19 and islet hormones was performed to confirm the islet to duct interrelationship. Sequential sectioning and immunostaining showed that 45% of the 172 islets examined appeared as single endocrine cell units or small clusters of < 10 endocrine cells on at least one plane of section. A topographical association was found between the islet endocrine cells and duct epithelial cells. Topographical associations with CK 19-stained duct cells occurred in 10.9% of the islet insulin-containing beta-cells and in 8.9% of the islet glucagon-producing alpha-cells. The frequency of topographical associations increased toward the more distally located duct systems. The CK19-stained duct cells and amylase-labelled acinar cells were less frequently in association with other islet hormone-producing cells. Topographical associations between islet endocrine cells and pancreatic duct cells are frequent in adult human pancreas. The islet-duct association suggests possible functional interactions between the two interrelated pancreatic compartments.