Distribution and ultrastructure of interstitial cells of Cajal in the gastric antrum of wild-type and Ws/Ws rats.

Interstitial cells of Cajal (ICC) in the stomach of wild-type and Ws/Ws mutant rats that are deficient in c-kit were studied by immunohistochemistry and electron microscopy to elucidate their regional specialization in the gastric antrum. Immunohistochemistry for Kit protein demonstrated that in wild-type rats ICC were located at the submucosal border of the circular muscle layer (ICC-SM) in a limited extension of the antrum from the pyloric sphincter towards the corpus, as well as within both the circular (ICC-CM) and longitudinal (ICC-LM) muscle layers and in the myenteric plexus region (ICC-AP). In c-kit mutant Ws/Ws rats while ICC-CM and ICC-LM were not observed, but unexpectedly, a few ICC-SM and ICC-AP were found. By electron microscopy, ICC-SM and ICC-AP were characterized by abundant mitochondria, many caveolae, a distinct basal lamina and formed gap junctions with other ICC or with smooth muscle cells and make close contacts with nerves. Thus, ICC-SM and ICC-AP of the rat antrum were classified as Type 3 ICC, the type most similar to smooth muscle cells. The functional significance of ICC-SM and their survival in the c-kit mutant animals is discussed in reference to the role of the c-kit/stem cell factor system for their cellular maturation.