HUMAN FETAL ENTEROCYTES IN-VITRO - MODULATION OF THE PHENOTYPE BY EXTRACELLULAR-MATRIX

The differentiation of small intestinal epithelial cells may require s timulation by microenvironmental factors in vivo. In this study, the e ffects of mesenchymal and luminal elements in nonmalignant epithelial cells isolated from the human fetus were studied in vitro. Enterocytes from the human fetus were cultured and microenvironmental factors wer e added in stages, each stage more closely approximating the microenvi ronment in vivo. Four stages were examined: epithelial cells derived o n plastic from intestinal culture and grown as a cell clone, the same cells grown On connective tissue support, primary epithelial explants grown on fibroblasts with a laminin base, and primary epithelial expla nts grown on fibroblasts and laminin with n-butyrate added to the incu bation medium. The epithelial cell clone dedifferentiated when grown o n plastic; however, the cells expressed cytokeratins and villin as evi dence of their epithelial cell origin. Human connective tissue matrix from Engelbreth-Holm-Swarm sarcoma cells (Matrigel) modulated their ph enotype: alkaline phosphatase activity increased, microvilli developed on their apical surface, and the profile of insulin-like growth facto r binding proteins resembled that secreted by differentiated enterocyt es. Epithelial cells taken directly from the human fetus as primary cu ltures and grown as explants on fibroblasts and laminin expressed grea ter specific enzyme activities in brush border membrane fractions than the cell clone. These activities were enhanced by the luminal molecul e sodium butyrate. Thus the sequential addition of connective tissue a nd luminal molecules to nonmalignant epithelial cells in vitro induces a spectrum of changes in the epithelial cell phenotype toward full di fferentiation.