GROWTH OF FETAL-RAT GASTROINTESTINAL EPITHELIAL-CELLS IS REGION-SPECIFICALLY CONTROLLED BY GROWTH-FACTORS AND SUBSTRATA IN PRIMARY CULTURE

The mammalian gastro-intestinal tract can be divided into three parts: esophagus and forestomach, glandular stomach, and intestine. We have previously reported primary culture systems for duodenal and glandular stomach epithelial cells in which the cells express tissue-specific m arker proteins. However, the effects of growth factors and substrata o n cell growth have not been fully investigated. In this study a primar y culture system was established for forestomach epithelial cells and the mechanism by which the growth of gastro-intestinal epithelial cell s is controlled in primary culture was examined. Forestomach, glandula r stomach and duodenal epithelial cells proliferated rapidly in cultur e, increasing their numbers about 30-, 20- and 10-fold, respectively, in the first 5 days. Scanning electron microscopy showed that these th ree types of epithelial cells exhibited region-specific morphologies i n culture; Results on the effects of growth factors and substrata on t he proliferation of the epithelial cells revealed that the culture con ditions required to induce maximal epithelial growth differed. Foresto mach and glandular stomach epithelial cells required similar combinati ons of growth factors to proliferate, and these were quite different f rom those required for duodenal epithelial cells. Glandular stomach an d duodenal epithelial cells could proliferate in a serum-free conditio n while forestomach epithelial cells could not. Thus, glandular stomac h epithelial cells exhibited intermediate characteristics between fore stomach and duodenal epithelial cells regarding their growth factor re quirement. Glandular stomach and duodenal epithelial cells could not p roliferate on plastic without collagen substrata while forestomach epi thelial cells could. Duodenal epithelial cells proliferated faster on collagen gels than on collagen films, and forestomach epithelial cells faster on collagen films than on collagen gels. Glandular stomach epi thelial cells proliferated similarly on both substrata. Thus again, gl andular stomach epithelial cells exhibited intermediate characteristic s between forestomach and duodenal epithelial cells regarding their su bstratum dependency. We conclude that the growth of gastro-intestinal epithelial cells is affected by both growth factors and substrata, and that glandular stomach epithelial cells exhibit intermediate characte ristics between forestomach and duodenal epithelial cells in respondin g to these factors. These results suggest that a head-to-tail gradient exists in the gastro-intestinal tract which controls the epithelial r esponse to growth factors and substrata.