Spontaneous and induced dome formation by two clonal cell populations derived from a human adenocarcinoma cell line, HT29.

The replacement of glucose by galactose in the culture medium resulted in partial structural and functional enterocytic differentiation of HT29 cells. In order to characterize populations of homogeneously differentiated HT29 cells we have selected two clonal cell lines HT29-D4 and HT29-D9 with the following functional and structural characteristics when grown in a galactose-containing medium: the two clonal cell populations were permanently morphologically differentiated as shown by the presence of mature junctional complexes and a well-organized brush border (especially for HT29-D4 cells); HT29-D4 and HT29-D9 cells were able to form domes early in confluency, which indicated a functional state of differentiation; the process of differentiation was fully reversible when glucose was added to the culture medium. The induction of domes was investigated in these two cell populations and we demonstrated for the first time that proteolytic enzymes are potent inducers of dome formation. The architecture of domes either obtained spontaneously or induced by proteolytic enzymes was not maintained in the presence of ouabain (a specific inhibitor of the Na+/K+-ATPase). In conclusion, HT29-D4 and HT29-D9 cells can be maintained permanently in a differentiated state in a glucose-free medium and were able to form domes at confluency. The observation that proteolytic enzymes were able to induce dome formation can help in the comprehension of the mechanism involved in the establishment of the differentiated state.