Inflammation and Immunity in Radiation Damage to the Gut Mucosa
Left panel ((a) to (e)): Radiation-induced damage to the rectal wall following localized exposure to 27 Gy single dose in the rat. (a) Healthy mucosa. (b) Two weeks after exposure, tissue shows mucosal and submucosal inflammation, with mucosal ulceration (u) and submucosal (sm) oedema. Glandular recovering (arrow) alternates with ulcerated areas. (c) Height weeks after exposure, underlying the ulcerated areas, the entire rectal wall is pathologic. The mucosa and submucosa show still severe inflammation, with tissue necrosis at the luminal frontier (purple coloration). Inflammation reaches the oedematous and dystrophic external muscular layers. Note that the muscularis mucosa disappeared. (e) Eight weeks after exposure, severe epithelial, submucosal, and muscular damage is associated with dystrophic submucosal and mesenteric vessels. The elastic layer is dystrophic (arrow) compared to the healthy vessels ((d), arrow) and, neointimal hyperplasia reduces the vessel lumen (double arrow). HeS staining, original magnification ×100 ((a), (d), (e)) or ×40 ((b), (c)), pictures Agnès Francois. Right panel radiation-induced damage to the rectal wall in patients treated for rectal adenocarcinoma, 5 to 7 weeks following the end of radiation therapy (45 Gy). (f) Healthy rectal mucosa. (g): Epithelial atypia with mucosal oedema and inflammation. Crypt positioning is disorganized and some are bifid and show hyperplasia, both signing epithelial regeneration. (h) Severe mucosal ulceration with submucosal oedema and dense inflammatory infiltrate. Crypt number is drastically reduced. (j) Dystrophic submucosal arteriole, with collagen deposition in the vessel wall and neointimal hyperplasia reducing the vascular lumen. (f), (g), (h) HeS staining, (i), (j) Sirius Red staining. Original magnification ×40, pictures Agnès François.