Distribution and ultrastructure of interstitial cells of Cajal in the mouse colon, using antibodies to Kit and Kit(W-lacZ) mice

The roles of the interstitial cells of Cajal in the stomach and intestine a re becoming increasingly clear. Interstitial cells of Cajal in the colon ar e less well known, however. We studied the development and distribution of the interstitial cells of Cajal in the mouse colon, using the tyrosine kina se receptor Kit as a marker. Sections and whole mounts were studied by conf ocal microscopy after double immunofluorescence with specific antibodies. T he ultrastructure of Kit-expressing cells was examined by electron microcop y in Kit(W-lacz)/+ transgenic mice, which carry the lacz gene inserted in p lace of the first exon of the Kit gene. In the subserosa, the interstitial cells of Cajal formed a two-dimensional plexus. In the myenteric area, the interstitial cells of Cajal formed a dense plexus that gradually merged wit h the interstitial cells of Cajal in the outer half of the circular muscle. The inner half of the circular layer was devoid of interstitial cells of C ajal whereas in the submuscular region the interstitial cells of Cajal form ed a two-dimensional plexus. Tertiary nerves with various chemical codings closely followed interstitial cell of Cajal processes. By electron microsco py, Kit-expressing cells in the outer parts of the musculature had scattere d caveolae, inconspicuous basal lamina and numerous mitochondria, whereas i n the submuscular region they had more pronounced myoid features. Kit-expre ssing cells in the mouse colon are identifiable as interstitial cells of Ca jal by their ultrastructure. The interstitial cells of Cajal in the mouse c olon mature postnatally. They are organized into a characteristic plexus, c lose to the nerves with various chemical codings.