Expression of ICAM-1 in colon epithelial cells: an ultrastructural study performed on in vivo and in vitro models.
BACKGROUND
Studies have suggested that in ulcerative colitis (UC), intercellular adhesion molecule-1 (ICAM-1) is involved in migration of leukocytes toward the colonic epithelium. A suitable in vitro model of chronic colonic inflammation does not exist, and the role of the epithelium is based on monolayers of cancer cells. Conflicting results exist on epithelial ICAM-1 expression, and the aim of this study was to compare the expression in various models of colonic epithelium.


METHODS
Colonic biopsies from four UC patients and four controls were examined by cryoimmuno-electron microscopy using ICAM-1-antibodies. In four other controls, the epithelium was isolated from colonic biopsies, embedded in collagen, and evaluated similarly. Isolated crypts and cultured cancer cells were stimulated with interferon-gamma (IFN-gamma) or tumor necrosis factor-alpha (TNF-alpha).


RESULTS
ICAM-1 was not expressed in the biopsies. In contrast, HT29 cells and the collagen-embedded crypts expressed ICAM-1 on the apical membranes proximal to the junctional complexes when stimulated with IFN-gamma or TNF-alpha in a dose-related manner.


CONCLUSIONS
ICAM-1 is not expressed on colonic epithelium in vivo. However, both colonocytes and HT29 cells were capable of expressing ICAM-1 on their apical membranes in response to supraphysiologic cytokine concentrations. These observations question the justification of extrapolating observations from colon cancer cell lines to in vivo inflammatory conditions.
Vainer
Ben
B
Department of Pathology, Herlev Hospital, University of Copenhagen, Denmark. vainer@rh.dk
Sørensen
Susanne
S
Seidelin
Jakob
J
Nielsen
Ole Haagen
OH
Horn
Thomas
T
D000328:Adult; D003093:Colitis, Ulcerative / Q000378:metabolism / Q000473:pathology; D003106:Colon / Q000737:chemistry* / Q000648:ultrastructure; D003110:Colonic Neoplasms / Q000737:chemistry / Q000473:pathology; D005260:Female; D019073:HT29 Cells; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000032:analysis*; D007371:Interferon-gamma / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000737:chemistry / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1; D007371:Interferon-gamma