Studies on the mechanisms of mucous cell depletion in experimental colitis

Mucous cell depletion is an important histological discriminator in favour of ulcerative colitis. The mechanism of this change was investigated in guinea pigs with experimental colitis induced by intrarectal instillation of acetic acid or dinitrochlorobenzene (DNCB) in sensitized animals. Both models showed mucous cell depletion. Increased numbers of mucous cells were flash-labelled with tritiated thymidine (3HTdR), indicating an increased pool of proliferating (oligo-) mucous cells; mucous cell production was in fact increased absolutely compared with control animals, and there was a marked increase in the rate of turnover of mucous cells. The results indicate that in colitis there is (i) increased mucous cell production and (ii) an increased rate of mucous cell turnover due to increased loss of older mucous cells. It is concluded that the disease process in experimental colitis leads to premature discharge of mucin, so that mucous cells are no longer recognizable by light microscopy. This explains the increase in mucin production in ulcerative colitis, which occurs even in the presence of significant mucous cell depletion.