Regulation of cytokeratin expression in XXXX lung alveolar epithelial cells in vitro.

@entity35 @entity29973 @entity460 @entity12073
Type II pneumocytes are the stem cells for the alveolar epithelium, proliferating and differentiating into type I cells during lung growth or after injury. The pattern of cytokeratin expression by type II cells in vitro has been linked to the state of differentiation of these cells. In particular, @entity29973 expression has been associated with the type II cell phenotype. We now examine the roles of cell shape and cell-cell interactions in the regulation of cytokeratin expression by @entity35 type II cells in vitro. Type II cell spreading and intercellular contacts were modulated by seeding cultures at high or low density (3.5 or 0.5 x 10(5) cells/cm2). When cultured at high density, cells demonstrated increased @entity29973 protein synthesis and diminished @entity12073 protein synthesis compared with highly spread cells at low density. This effect was a reflection of changes in the abundance of mRNAs for the individual cytokeratins. Alveolar epithelial cells at high density also formed extensive desmosomes between the cells. Desmosome formation was significantly decreased when cells were seeded at low density or in reduced (0.05 mM) @entity460 medium. @entity29973 mRNA and protein expression were also significantly decreased when desmosome formation was inhibited in reduced @entity460 medium, while @entity460 content of the medium had little effect on @entity12073 . These studies suggest that type II cell expression of @entity29973 , a differentiation-related cytokeratin, is regulated by factors influencing cell shape and intercellular contacts between epithelial cells. They further suggest that cell-cell interactions between epithelial cells may play a role in the modulation of epithelial cell phenotype.
