Existence of c-Kit negative cells with ultrastructural features of interstitial cells of Cajal in the subserosal layer of the W/W(v) mutant mouse colon.

Interstitial cells of Cajal (ICC) are mesenchymal cells that are distributed along the gastrointestinal tract and function as pacemaker cells or intermediary cells between nerves and smooth muscle cells. ICC express a receptor tyrosine kinase c-Kit, which is an established marker for ICC. The c-kit gene is allelic with the murine white-spotting locus (W), and some ICC subsets were reported to be missing in heterozygous mutant W/W(v) mice carrying W and W(v) mutated alleles. In this study, the characterization of interstitial cells in the subserosal layer of W/W(v) mice was analyzed by immunohistochemistry and electron microscopy. In the proximal and distal colon of W/W(v) mutant mice, no c-Kit-positive cells were detected in the subserosal layer by immunohistochemistry. By electron microscopy, the interstitial cells, which were characterized by the existence of caveolae, abundant mitochondria and gap junctions, were observed in the W/W(v) mutant colon. The morphological characteristics were comparable to those of the multipolar c-Kit positive ICC seen in the subserosa of proximal and distal colon of wild-type mice. Fibroblasts were also located in the same layers, but the morphology of the fibroblasts was distinguishable from that of ICC in wild type mice or of ICC-like cells in W/W(v) mutant mice. Collectively, it is concluded that c-Kit-negative interstitial cells showing a typical ICC ultrastructure exist in the proximal and distal colon of W/W(v) mutant mice.