Authors: Lee EY, Stenson WF, DeSchryver-Kecskemeti K.

Instiution: Division of Surgical Pathology, Washington University Medical School, St. Louis, Missouri.

Summary: Crohn's disease (CD) of the bowel showed a statistically significant thickening of the muscularis mucosae when compared with disease controls. In areas of gross stricture in CD, the muscularis mucosae comprised almost 10% of total wall thickness. Similar findings were also present in a previously characterized experimental model of CD (trinitrobenzene sulfonic acid-induced colitis in rats), particularly in what appeared to be grossly strictured areas.

Taken together, these findings suggest that increased mass of muscularis mucosae smooth muscle may be responsible in part for the commonly observed stricture formation in CD. As extreme muscularis mucosae hyperplasia appears to be peculiar to CD, it may serve as an additional marker differentiating CD from other diseases.

Study link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2020666&dopt=Abstract

Authors: Graham MF, Diegelmann RF, Elson CO, Lindblad WJ, Gotschalk N, Gay S, Gay R.

Institution: Department of Pediatrics (Children's Medical Center), Medical College of Virginia, Richmond.

Summary: The collagen content and the relative amount of collagen types were quantitated in control intestine as well as in both inflamed and strictured intestine resected from patients with Crohn's disease. The major collagen type in control intestine was type I (68%), followed by types III (20%) and V (12%).

In strictured intestine both collagen content and the relative amount of type V collagen were significantly increased compared with control intestine. Histologic studies demonstrated that in strictured specimens there was a striking proliferation of smooth muscle cells of the muscularis mucosae associated with an accumulation of collagen in the submucosa. The thickness of the muscularis propria was also increased.

Immunohistochemical studies demonstrated small amounts of type V collagen in the submucosa of control bowel. In contrast, large amounts of type V collagen were seen in the fibrotic, expanded submucosa of strictured bowel, particularly in the areas where smooth muscle cells of the muscularis mucosae had proliferated. Intestinal strictures in Crohn's disease are therefore characterized by an accumulation of collagen, a proliferation of smooth muscle cells, and an increase in type V collagen, a collagen type produced in relatively large amounts by smooth muscle cells. These changes appear to result in both a loss of the normal compliance of the intestine and a thickening of the intestine wall, resulting ultimately in the intestinal obstruction so frequently seen in patients with Crohn's disease.

Study link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=3335305&query_hl=30&itool=pubmed_docsum