HT-29 cells are an in vitro model for the generation of cell polarity in epithelia during embryonic differentiation.

A monoclonal antibody that recognizes a membrane glycoprotein specific for the apical membrane of human colonic epithelial cells has been used to follow the differentiation and polarization of a cell line, HT-29, derived from a human colon adenocarcinoma. When these cells formed a polarized epithelium, the antigen was concentrated at the apical plasma membrane. It was also found intracellularly in vesicles and vacuoles. When HT-29 cells were undifferentiated and unpolarized, the antigen was not expressed significantly at the plasma membrane but was found concentrated in the membranes of intracellular vacuoles. Cells not yet organized into an epithelium may thus synthesize a membrane protein specific for their future apical membranes and store it intracellularly until the polarization process takes place. Intermediary stages of differentiation were occasionally recognized. They are characterized by a small number of cells surrounding an intercellular lumen. These lumina displayed apical membrane features (the presence of the apical antigen, of some microvilli, and of junctional complexes), although the cells were not fully differentiated. The differentiation process in HT-29 cells is apparently similar to that observed during embryonic development of the intestine. Therefore, HT-29 cells represent a useful model system to study epithelial differentiation in vitro.