Pancreatic hepatocyte differentiation in the copper-deficient adult rat pancreas occurs via discrete phenotypically-defineable stages

Abstract

Hepatocytes have previously been demonstrated in the pancreas of rats maintained on a copper-deficient (CUD) diet for 8 weeks, followed by a copper-repletion (CUR) diet for 8 weeks. Indirect evidence suggests that pancreatic duct cells (PDC) are the progenitor cells for pancreatic hepatocytes (PH). However, the capacity for PDC to differentiate into PH has not been directly demonstrated. Our aim was to establish the ductular origin of PH using immunofiuorescence analysis of the copper-deficient rat pancreas. METHODS: Pancreas was removed from American Fisher rats fed the CuD diet for 5, 6, 7, and 8 weeks and those fed the CuR for 1, 2, and 3 weeks following 8 weeks of the CuD diet. Double-labeled immunofluorescence analysis was performed on acetone-fixed pancreatic sections using a PDCspecific marker (OV6), hepatocyte-specific markers (C-CAM, H.5, H.6), and a pancreatic acinar/duct cell marker (OC2). RESULTS: Immunohistochemical analysis of CuD rat pancreas demonstrated a membrane hepatocyte-specific antigen (C-CAM) on a subpopulation of ductal structures and on newly forming PH. As the PH phenotypically matured, they adquired additional hepatocyte-specific markers (H.5+, H.6+). CONCLUSION: The close proximity of newly developing PH to C-CAM+ ductal structures in the CuD rat pancreas is consistent with the likelihood that PH are derived from PDC. The observation of a transition phenotype (OV6-weakly expressed, C-CAMstrongly expressed) from PDC (OV6+, C-CAM-) to PH (OV6-, C-CAM+) further supports the likelihood that PDC are progenitor cells for PH. Furthermore, the data demonstrates that the process of PH differentiation is characterized by discrete phenotypically definable stages. Future studies will attempt to directly determine whether PDC are the progenitor ceils for PH using transplantation experiments.