Sascha Birkner, Susanne Weber, Angelika Dohle, Günter Schmahl and Wolfram Föllmann
Epithelial crypts from the bovine colon were obtained by using a combined mechanical and enzymatic isolation method, followed by differential D-sorbitol gradient centrifugation. By using this isolation technique, a pure fraction of epithelial crypts with minimal mesenchymal contamination was obtained. The crypts were seeded in collagen-coated plastic flasks. The attached epithelial cells proliferated and formed a confluent monolayer after 6 days in culture. Under low-serum culture conditions (1% fetal calf serum), the cells had a population doubling time of 21–22 hours. During the culture period, the colonocytes were characterised morphologically and enzymatically. The morphology of the cultured cells was confirmed by scanning electron microscopy and transmission electron microscopy. The presence of microvilli, tight junctions and desmosomes demonstrated the ability of the cultured cells to restore an epithelial-like cell monolayer. The epithelial origin of the cells was demonstrated by labelling the cells with antibodies against epithelial-specific cytokeratins 7 and 13. The functional integrity of the cells was evaluated by measuring various marker enzymes (γ-glutamyltranspeptidase, acid phosphatase, alkaline phosphatase, NADH-dehydrogenase) and membrane-associated Na+–K+-ATPase activity. Membrane integrity was determined by measuring the leakage of lactate dehydrogenase into the culture medium. This new culture system for bovine colon epithelial cells could be used as an in vitro model of the colon epithelium in physiological and toxicological studies.
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