Degeneration of the pericryptal myofibroblast sheath by proinflammatory cytokines in inflammatory bowel diseases.
OBJECTIVE
Inflammatory bowel diseases (IBDs) are characterized by remodeling of the intestinal mucosa, which is associated with excessive cytokine release. Previous studies have shown that the epithelium in the crypt region of the mucosa in patients with Crohn's disease is susceptible to proinflammatory cytokines. We investigated whether the subepithelial myofibroblasts in this region were affected by these inflammatory conditions.


METHODS
Immunofluorescence and immunohistochemistry were performed on inflamed and uninflamed specimens from patients with IBD to detect alpha-smooth muscle actin (alphaSMA), desmin, and tenascin-C. The effects of the proinflammatory cytokines interleukin-1beta, tumor necrosis factor-alpha, and interferon-gamma were analyzed in human intestinal myofibroblast cultures by immunoblotting and apoptosis assays.


RESULTS
Immunofluorescence analysis revealed decreased levels of the extracellular matrix molecule tenascin-C in pericryptal sheaths and alphaSMA in the immediate vicinity of the crypts in the inflamed specimens, indicating that the myofibroblast pericryptal sheath is affected by proinflammatory cytokines. Although individual cytokines did not affect myofibroblast proliferation or survival, cytokine combinations triggered caspase-dependent apoptosis. alphaSMA levels were reduced significantly in cells exposed to cytokines, either alone or in combination, suggesting dedifferentiation of myofibroblasts. Proinflammatory cytokines did not affect tenascin-C expression, suggesting that the decrease observed in the inflamed mucosa resulted from myofibroblast apoptosis.


CONCLUSIONS
The subepithelial myofibroblasts of the epithelial sheath are disrupted in the intestinal mucosa of patients with IBD. A loss of myofibroblasts appears to result from the susceptibility of these cells to proinflammatory cytokines.
Francoeur
Caroline
C
Canadian Institutes of Health Research Team on the Digestive Epithelium, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada.
Bouatrouss
Yamina
Y
Seltana
Amira
A
Pinchuk
Iryna V
IV
Vachon
Pierre H
PH
Powell
Don W
DW
Sawan
Basem
B
Seidman
Ernest G
EG
Beaulieu
Jean-François
JF
D017209:Apoptosis / Q000187:drug effects; D002454:Cell Differentiation; D049109:Cell Proliferation; D002470:Cell Survival; D016207:Cytokines / Q000502:physiology*; D005347:Fibroblasts / Q000473:pathology; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007150:Immunohistochemistry; D015212:Inflammatory Bowel Diseases / Q000473:pathology*; D007371:Interferon-gamma / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000473:pathology*; D019063:Tenascin / Q000096:biosynthesis; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D016207:Cytokines; D019063:Tenascin; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma