Endocrine differentiation of rat enterocytes in long-term three-dimensional co-culture with intestinal myofibroblasts

The proliferation and differentiation of the small intestinal epithelium depends on the microenvironment surrounding the stem cells, such as intestinal subepithelial myofibroblasts. Although there have been many culture studies of intestinal epithelial–mesenchymal interaction, a culture which allows long-term observations has been difficult. This study investigated the influence of intestinal subepithelial myofibroblasts on the proliferation and differentiation of intestinal epithelial cells with a relatively long-term observation of 3 wk using a 3D co-culture system. Cultured rat intestinal subepithelial myofibroblasts, obtained from the duodenum, were embedded in collagen gel and cells from the rat intestinal epithelial cell line IEC-6 seeded onto it. Histologic sections of the cell-embedded gels were made and histochemical and immunohistochemical examinations were carried out in conjunction with expression analysis of the pancreatic duodenal homeobox 1 (pdx-1) transcription factor in IEC-6 cells. The IEC-6 cells showed increased proliferation and displayed characteristic endocrine features when co-cultured with rat intestinal subepithelial myofibroblasts, arranging themselves into multilayer structures and becoming cuboidal, with abundant cytoplasm and oval nuclei. Some IEC-6 cells were immunohistochemically positive for chromogranin A and glicentin. They also expressed the pdx-1 transcription factor at both the mRNA and protein levels. The number and percentage of chromogranin A-positive cells increased with culture time, whereas no increase was observed in cells cultured without rat intestinal subepithelial myofibroblasts. The present study using a long-term 3D co-culture model has obtained evidence of the participation of intestinal subepithelial myofibroblasts in enteroendocrine differentiation, supported by the expression of pdx-1 and glicentin production.