Importance of a fibroblastic support for in vitro differentiation of intestinal endodermal cells and for their response to glucocorticoids.

Microexplants of 14- or 15-day-old fetal rat intestinal endoderm, separated from mesenchyme by collagenase, were placed on culture dishes coated with different extracellular matrix components or on confluent monolayers of intestinal mesenchymal cells or of fetal skin fibroblasts. Only small variations in the attachment or spreading of the endodermal cells could be observed when they were cultured on the different acellular substrata, and their survival never exceeded one week. When cocultured with intestinal or skin fibroblasts, endodermal cells proliferated and the survival time was prolonged to 2 or 3 weeks. Furthermore, differentiation, as assessed by the polarization of the cells, occurred and was characterized by the maturation of apical brush borders and by the synthesis of microvillar digestive enzymes visualized immunocytochemically with monoclonal antibodies. Glucocorticoids accelerated structural differentiation and stimulated or induced brush border enzymes only in the coculture conditions. These experiments emphasize the role of a fibroblastic support without tissue specificity on the cytodifferentiation of intestinal endodermal cells. They also suggest a mesenchymal dependence on the hormonal response.