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 e pithelial cells is affected by many factors including epithelial-mesen chymal interactions. To clarify the control mechanism of their differe ntiation, we developed a primary culture system for fetal rat glandula r stomach epithelial cells, and examined their differentiation in the absence of mesenchyme. Pure glandular stomach epithelial tissues obtai ned from 16.5-day fetal rats proliferated rapidly, increasing their nu mber about 20 times in the first 7 days. The epithelial nature of the cells was confirmed by the presence of cytokeratin in the cells. Gland ular stomach epithelial cells formed simple cuboidal/squamous epitheli a with many mucous granules in their cytoplasm, and exhibited epitheli al 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 prot ease activity in culture. Previous studies showed that glandular stoma ch epithelial cells specifically expressed two types of acid proteases : pepsinogens in chief and mucous neck cells, and cathepsin E in surfa ce mucous cells. Immunohistochemical studies using specific antibodies showed that the cultured cells expressed cathepsin E but not pepsinog ens, and the result was confirmed by zymogram and Western blotting ana lysis. We thus concluded that fetal rat glandular stomach epithelial c ells differentiated into surface mucous cells that expressed cathepsin E in primary culture in the absence of mesenchyme.