Distinct Distribution of Laminin and Its Integrin Receptors in the Pancreas

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Abstract
Tissue function is regulated by the extracellular microenvironment including cell basement membranes, in which laminins are a major component. Previously, we found that laminin-1 promotes differentiation and survival of pancreatic islet cells. Here we characterize the expression pattern of laminins and their integrin receptors in adult pancreas. Although they are expressed in the basement membrane of acinar cells and duct epithelium, no laminin chains examined were detected extracellularly in the pancreatic islets. In contrast to laminin β1- and γ1-chains, the α1-chain, unique to laminin-1, was not detected. Laminin-10 (α5β1γ1) was expressed in acinar tissue, whereas laminins-2 (α2β1γ1) and -10 were expressed in the blood vessels. The laminin connector molecule, nidogen-1, had a distribution similar to that of laminin β1 and γ1, whereas fibulin-1 and -2, which compete with nidogen-1, were mostly confined to blood vessels. Integrin subunits α6 and α3 were detected in acinar cells and duct epithelial cells, but α6 was absent in islet cells. Integrin α6β4 was detected only in duct cells, α6β1 in both acinar and ductal cells, and α3β1 in acinar, duct, and islet cells. These findings are a basis for further investigation of the role of extracellular matrix molecules and their receptors in pancreas function.