Growth and differentiation of intestinal endodermal cells in a coculture system.

To investigate the role of epithelial-mesenchymal interactions on intestinal maturation, we cultured embryonic epithelial cells in several experimental conditions. Microexplants of 14-15 days fetal rat intestinal endoderm, separated from the mesenchyme by collagenase, were seeded on dishes coated with different extracellular matrix components (collagens I, III, IV, fibronectin, laminin) 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 substrata and their survival never exceeded one week. When cocultured with intestinal or skin fibroblasts, however, endodermal cells grew, formed a monolayer, survival time was prolonged up to two to three weeks, and differentiation occurred. This differentiation was assessed by cell polarisation, morphological maturation of apical brush borders, synthesis of microvillar digestive enzymes and of extracellular matrix molecules seen immunocytochemically. Finally, glucocorticoids which are known to stimulate or induce brush border enzymes, accelerated the morphological and enzymatic maturation only in the cocultures.