BACKGROUND Crohn's disease (CD) is a chronic relapsing inflammatory bowel disease of unknown origin. It is characterised by chronic mucosal ulcerations which affect any part of the intestine but most commonly are found in the ileum and proximal colon.

AIMS Studies were undertaken to provide information regarding cell specific expression of mucin genes in the ileum of patients with CD.

PATIENTS AND METHODS Expression of mucin genes was analysed in the ileal mucosa of patients with CD and controls by in situ hybridisation and immunohistochemistry.

RESULTS In healthy ileal mucosa, patients with CD showed a pattern identical to normal controls with main expression of MUC2 andMUC3, lesser expression ofMUC1 and MUC4, and no expression of MUC5AC,MUC5B, MUC6, orMUC7. In the involved mucosa, the pattern was somewhat comparable although heterogeneous to that observed in healthy ileal mucosa. Importantly, a particular mucin gene expression pattern was observed in ileal mucosa close to the ulcer margins in ulcer associated cell lineage, with the appearance ofMUC5AC and MUC6mRNAs and peptides, which are normally restricted to the stomach (MUC5AC and MUC6) and duodenum (MUC6), and disappearance ofMUC2.

CONCLUSIONS Our results suggest that gel forming mucins (more particularly MUC5AC and MUC6) may have a role in epithelial wound healing after mucosal injury in inflammatory bowel diseases in addition to mucosal protection.