Connective tissue changes in ileal Crohn's disease: relationship to disease phenotype and ulcer-associated cell...

Abnormalities of enteric collagen and smooth-muscle cell content have been documented in Crohn's disease. We studied the relationships among connective tissue changes, disease "type," and other disease features using immunohistochemistry and image analysis.

Twenty consecutive ileal resections for Crohn's disease and ten normal terminal ileal specimens were evaluated using conventional histopathologic examination. Monoclonal antibodies to smooth-muscle actin and Type III collagen fibers were used to determine the percentage area of the submucosa occupied by these constituents using image analysis.

There were no significant differences in smooth-muscle content among stenosed, perforated, and ulcerated specimens. There was a significantly increased submucosal Type III collagen content in stenosed vs. other types. The only factor that correlated with smooth-muscle cell content was the amount of ulcer-associated cell lineage present.

Increased deposition of Type III collagen fibers rather than smooth-muscle proliferation is associated with a stenotic phenotype. Loss of Type III collagen fibers may play a role in the development of perforating complications. We have found no evidence that smooth-muscle cells are the source of Type III collagen fiber production although there is evidence that ulcer-associated cell lineage may be related to the stimulus leading to submucosal neomuscularization.