Differentiation of immature enterocytes into enteroendocrine cells by Pdx1 overexpression

The development of a variety of enteroendocrine cells of the gut is poorly understood. We tested whether immature intestinal stem cells were switched to multiple enteroendocrine hormone-producing cells by in vitro transfer of a homeobox gene. We transfected the pancreatic-duodenal homeobox 1 gene (Pdx1) into IEC-6 cells, an embryonic intestinal epithelial cell line derived from a normal rat, and selected the cells that overexpressed Pdx1 by 150-fold compared with control. The cells were examined for differentiation into enteroendocrine cells by immunocytochemical and electron microscopic analyses. Transfected cells cultured on micropore filters formed a trabecular network piled up on monolayer cells. These trabecular cells showed nuclear localization of Pdx1 protein and contained well-developed rough endoplasmic reticulum as well as many secretory granules of pleomorphic shape in the cytoplasm. Antibodies against chromogranin A, serotonin, cholecystokinin, gastrin, and somatostatin stained these secretory granules in the cytoplasm. Furthermore, immunofluorescence double staining analysis showed that different hormones were produced within a cell. These results provide the evidence that immature intestinal epithelial cells can differentiate into multiple hormone-producing enteroendocrine cells in response to overexpression of Pdx1.