Upregulation of Fas-Fas-L (CD95/CD95L)-mediated epithelial apoptosis--a putative role in pouchitis?

Introduction: Ileal pouch-anal anastomosis (IPAA) remains the gold standard for patients with refractory ulcerative colitis. Pouchitis causes considerable morbidity in 40% of patients with IPAA. This study examined the role of increased epithelial apoptosis in the etiology of pouchitis.
Methods: Following ethical approval pouch biopsies taken from patients with a history of pouchitis were compared with age-matched controls from patients who were pouchitis free. Apoptosis was detected immunohistochemically using a monoclonal antibody (M30) and terminal deoxyribonucleotidyl transferase (TDT)-mediated dUTP-digoxigenin end labeling (TUNEL). Villous atrophy was assessed histologically and correlated with levels of apoptosis. Epithelial Fas-ligand (L) was also assessed immunohistochemically.
Results: A significant increase in TUNEL staining was seen at the epithelial but not at the lamina propria level for known pouchitis patients versus controls (0.091 vs 0.035; P < 0.01). Similarly, epithelial M30 immunoreactivity (0.225 vs 0.082; P < 0.05) and villous atrophy (0.035 vs 0.10; P < 0.05) were significantly increased in pouches with previous pouchitis when compared with normal pouches. Upregulation of Fas-L expression was characteristic of this epithelium. Mononuclear cells were strongly positive for Fas-L. Increased epithelial levels of apoptosis correlated with increased levels of villous atrophy.
Conclusions: Our data suggest a role for elevated Fas-Fas-L (CD95-CD95L)-mediated epithelial apoptosis in the etiology of pouchitis. Increased levels of villous atrophy may result from increased apoptosis and thereby predispose to infection by otherwise apathogenic organisms.
(Copyright 2001 Academic Press.)