Crohn's disease of the colon: ultrastructural changes in submuscular interstitial cells of Cajal.

Interstitial cells of Cajal (ICC) at the submuscular border of the human colon (ICC-SMP) are the proposed pacemaker cells of the musculature. In patients with Crohn's disease (CD) of the colon, ICC-SMP showed characteristic cytological changes from controls. The changes comprised secondary lysosomes in connection with lipid droplets and cytoplasmic vacuoles or multiple empty, confluent and often outbulging vacuoles merging with cisterns of granular endoplasmic reticulum and clusters of glycogen granules. These changes were most pronounced in patients with macroscopical mucosal inflammation but were also demonstrable in uninvolved colonic segments. Relationships of ICC to other cells were undisturbed. The changes were selective to ICC-SMP, as glial cells, muscle cells and fibroblast-like cells at the submuscular border showed no cytological alterations compared with controls. Varicosities of the submuscular plexus were often empty and dilated. Fibroblast-like cells selectively encased macrophages and mast cells. The cytological changes in ICC-SMP in CD are thus similar to changes seen in ulcerative colitis and may be of pathophysiological significance with regard to the motility and sensory disturbances seen in patients with CD.