A morphological study of a human adenocarcinoma cell line (HT29) differentiating in culture. Similarities to intestinal embryonic development.

HT29 cells, a human adenocarcinoma cell line, when grown in Dulbecco's modified Eagle's medium (DMEM), form a multilayer of morphologically undifferentiated and unpolarized cells. However, when DMEM is replaced by RPMI medium, after 1-4 passages, a large amount of intracellular (ICL) and intercellular (ITCL) or secondary lumina (SL) are observed. These are detected in the light microscope and appear in the electron microscope as spherical structures embedded inside a multilayer of cells and bordered with microvilli. After 4-15 passages in RPMI, the cells retain the same pattern of cell growth but in addition exhibit apical brush-border microvilli and reveal a well developed belt of tight junctions. After 15 passages a single layer of polarized cells is clearly observed and a large number of 'domes' appeared. These results show that each of these culture types mimics morphologically specific stages described during intestinal ontogenesis between the 9th and the 16th week in the human embryo.