AJP - Lung Cellular and Molecular Physiology, Vol 266, Issue 4 476-L484, Copyright © 1994 by American Physiological Society
Regulation of alveolar epithelial cell ICAM-1 expression by cell shape and cell-cell interactions
R. Paine 3rd, P. Christensen, G. B. Toews and R. H. Simon
Department of Internal Medicine, University of Michigan, Ann Arbor 48109-0360.
In normal lung, intercellular adhesion molecule 1 (ICAM-1) is expressed at
high levels on thin type I alveolar epithelial cells, but is minimally
expressed on cuboidal type II cells. ICAM-1 is induced in primary culture
on tissue culture-treated plastic as type II cells undergo transition
toward a type I cell-like phenotype. We hypothesized that alveolar
epithelial cell expression of ICAM-1 might be regulated in part by signals
that influence the state of differentiation of these cells. We found that
rat type II cells that were cultured as aggregates of cuboidal cells on a
hydrated basement membrane gel (Matrigel) or on floating type I collagen
gels, expressed markedly less ICAM-1 protein and mRNA compared with cells
that had spread on plastic. In contrast, type II cells that had spread as
monolayers on dishes coated with basement membrane proteins in planar
configuration demonstrated ICAM-1 expression comparable to that of cells on
plastic alone. Thus regulation of alveolar epithelial cell expression of
this immunologically important adhesion molecule involves complex spatial
interactions of the cells with the basement membrane and other epithelial
cells.
