FETAL-RAT GLANDULAR STOMACH EPITHELIAL-CELLS DIFFERENTIATE INTO SURFACE MUCOUS CELLS WHICH EXPRESS CATHEPSIN-E IN THE ABSENCE OF MESENCHYMAL CELLS IN PRIMARY CULTURE

It is well established that the differentiation of glandular stomach epithelial cells is affected by many factors including epithelial-mesenchymal interactions. To clarify the control mechanism of their differentiation, we developed a primary culture system for fetal rat glandular stomach epithelial cells, and examined their differentiation in the absence of mesenchyme. Pure glandular stomach epithelial tissues obtained from 16.5-day fetal rats proliferated rapidly, increasing their number about 20 times in the first 7 days. The epithelial nature of the cells was confirmed by the presence of cytokeratin in the cells. Glandular stomach epithelial cells formed simple cuboidal/squamous epithelia with many mucous granules in their cytoplasm, and exhibited epithelial polarity with microvilli on the luminal surface, basal lamina-like material on the basal surface, and junctional complexes in the apical region. Biochemical analysis showed that the cells expressed acid protease activity in culture. Previous studies showed that glandular stomach epithelial cells specifically expressed two types of acid proteases: pepsinogens in chief and mucous neck cells, and cathepsin E in surface mucous cells. Immunohistochemical studies using specific antibodies showed that the cultured cells expressed cathepsin E but not pepsinogens, and the result was confirmed by zymogram and Western blotting analysis. We thus concluded that fetal rat glandular stomach epithelial cells differentiated into surface mucous cells that expressed cathepsin E in primary culture in the absence of mesenchyme.