Proliferation and differentiation of fetal rat intestinal epithelial cells in primary serum-free culture

It has been a subject of controversy whether fibroblastic cells are necessary for the proliferation of intestinal epithelial cells in primary culture. To answer this question, we have developed a serum-free primary culture system which allows reproducible and quantitative assays of proliferation and differentiation of fetal rat intestinal epithelial cells in the absence of fibroblastic cells. Pure intestinal epithelial tissues were obtained from 16.5-day fetal rats without contamination of mesenchymal cells, and were successfully cultured on a collagen gel in a medium consisting of Ham's F12, bovine serum albumin, epidermal growth factor (EGF), insulin, cholera toxin, transferrin and hydrocortisone. The epithelial nature of the cultured cells was confirmed by the presence of cytokeratin in the cells. Under optimal culture conditions, intestinal epithelial cells readily attached to the substratum in a day, and proliferated rapidly in vitro, increasing their number about 10 times in the first 5 days. EGF, insulin, cholera toxin, transferrin and hydrocortisone synergistically induced the epithelial proliferation, and lack of any one of them resulted in a significant reduction of the proliferation. In contrast, fetal bovine or horse serums, which have been widely used to supplement culture media, severely inhibited the epithelial proliferation. Histological examination showed that the epithelial cells formed simple cuboidal epithelia with basally-located nuclei when cultured on collagen gels. The intestinal epithelial nature of the cells was affirmed by the presence of villin on their luminal surface. Ultrastructurally, cells were connected by tight junctions and desmosomes at the subluminal region, and microvilli were projecting on the luminal surface, indicating that the cells in primary culture retained some characteristics of absorptive epithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)