Reduced hydrophobicity of the colonic mucosal surface in ulcerative colitis as a hint at a physicochemical barrier defect

There is increasing evidence that a defect of the gastrointestinal mucosal barrier is important for the development of inflammatory bowel diseases (IBD). The hydrophobicity of the colonic mucosal surface is a measure of its resistance to luminal antigens, e.g. of bacterial origin. Therefore, the purpose of this study was to determine this parameter in patients suffering from IBD. Nineteen patients with ulcerative colitis (UC), ten patients with Crohn's disease (CD) and 20 controls were examined. All underwent colonic surgery at the University Hospital Heidelberg. Clinical disease activity was determined. From every subject, colonic tissue specimens were obtained, and hydrophobicity of the mucosal surface was determined with a goniometer by multiple plateau contact angle measurements. Histological evaluation of disease activity was performed in directly adjacent tissue specimens. Hydrophobicity of the colonic mucosal surface, expressed as plateau contact angles, was significantly reduced in patients with UC (mean +/- SEM, 47.8A degrees A +/- 3.4A degrees) compared to those with CD (72.0A degrees A +/- 5.2A degrees) and controls (72.5A degrees A +/- 5.6A degrees; over-all P = 0.0004; UC versus controls, P < 0.001; UC versus CD, P < 0.05; CD versus controls, P > 0.05). Between mucosal hydrophobicity and clinical disease activity, as well as mucosal hydrophobicity and histological disease activity, no significant correlation was found. The results suggest a defective physicochemical barrier as an essential factor in the pathogenesis of UC, but not CD. The fact that no correlation was found between mucosal hydrophobicity and disease activity may indicate that the loss of mucosal hydrophobicity in UC is not exclusively a secondary effect due to inflammation.