Interstitial cells of Cajal in the striated musculature of the mouse esophagus

Interstitial cells of Cajal (ICC) are important regulatory cells in the smo oth muscle coats of the digestive tract. Expression of the Kit receptor tyr osine kinase was used in this study as a marker to study their distribution and development in the striated musculature of the mouse esophagus. Sectio ns and whole-mounts were studied by immunohistochemistry. Kit(w-lacZ) trans genic mice, which carry the lacZ reporter gene inserted in place of the fir st exon of the Kit gene, were processed for Xgal histochemistry, for quanti tative analysis and for ultrastructural studies. Spindle-shaped ICC were sc arce in both muscle layers of the thoracic esophagus, while their number in creased steeply toward the cardia in the striated portion of the intraabdom inal esophagus. They did not form networks and had no relationship with int rinsic myenteric ganglia and motor end-plates. They were often close to ner ve fibers immunoreactive for neuronal nitric oxide synthase (nNOS), vasoact ive intestinal polypeptide (VIP) or neuropeptide Y (NPY), but not to fibers immunoreactive for substance P (SP), calcitonin gene related peptide (CGRP ), enkephalin, or the capsaicin receptor VR1. They were present in the fetu s but absent in adult ICC-deficient Kit(W-lacZ)/Kit(Wv) mice. Interstitial cells of Cajal were identified by electron microscopy by their ultrastructu re in the striated muscle of the esophagus and exhibited Xgal labeling, whi le fibroblasts and muscle cells were unlabeled. Interstitial cells of Cajal are scattered between striated muscle cells in the mouse esophagus. They a re close to nerves with defined neurochemical coding and could possibly rep resent specialized esophageal spindle proprioceptors.