Modulation of extracellular conditions prevents the multilayering of the simple epithelium.

Simple epitheliums in normal glandular systems are regulated not to stratify even though the constituent cells proliferate and will rise from the epithelium. Since epithelial cells have the potential to establish cell-cell adhesions, the avoidance of stratification must be related to the intracellular signal cascades and the extracellular conditions. The contributions of the former are becoming clarified, but the influence of the latter is poorly understood. In the present study, we examined whether the frequency of cell-on-cell adhesion, which mimics the early stage of multilayering, is dependent on the type of the extracellular scaffold protein. Wild-type epithelial cells were cultured on E-cadherin-Fc (a cell-cell adhesion protein) or collagen (an extracellular matrix protein), and then, green fluorescent protein (GFP)-positive cells were seeded onto these wild-type cells. We observed that the cell-on-cell adhesion (adhesion of the GFP-positive cell to the wild-type cells) was more frequent in the E-cadherin-Fc treatment than the collagen treatment. The cell-on-cell adhesions that were observed in the E-cadherin treatment were transient and decreased in frequency to that of the collagen treatment after the 12 h of cell culture. We observed the disappearance of E-cadherin-Fc but not collagen during cell culture. These results suggest that transient multilayering in simple epithelium is possible, depending on the types of extracellular scaffold protein, and they imply that cells can modify the extracellular conditions to meet normal cellular conditions.