Abstract
Located within the tunica muscularis of the gastrointestinal (GI) tract are networks of cells known as interstitial cells of Cajal (ICC). ICC are critical for important basic functions of GI motility such as generation and propagation of slow-wave pacemaker activity and reception of regulatory inputs from the enteric nervous system. We have developed a novel procedure to identify and isolate individual ICC from freshly dispersed cell preparations of the murine small intestine and gastric fundus and to determine differential transcriptional expression We have compared the expression profiles of pacemaker ICC isolated from the murine small intestine (IC-MY) and ICC involved in neurotransmission from the gastric fundus (IC-IM). We have also compared expression profiles between ICC and smooth muscle cells (SMC) and between freshly isolated ICC and cultured ICC. Cultured ICC express smooth muscle myosin, whereas freshly dispersed ICC do not. All cell types express muscarinic receptor types M(2) and M(3), neurokinin receptors NK(1) and NK(3), and inhibitory receptor VIP-1, whereas only cultured ICC and SMC express VIP-2. Both cultured and freshly dispersed IC-IM and IC-MY express the soluble form of stem cell factor, whereas SMC from the gastric fundus express only the membrane-bound form.
Highlights
Cultured INTERSTITIAL CELLS OF CAJAL (ICC) isolated from the murine small intestine retain the ability to generate electrical rhythmicity, and they may be a powerful model for studying the pacemaker mechanism
We developed a technique that labeled ICC in situ and performed enzymatic dispersion after identification of Kit-like immunoreactivity (Kit-LI). These experiments were performed on muscles of the murine gastric fundus and the myenteric region of the small intestine
Previous studies have shown that muscarinic receptors M2 and M3 are expressed in muscles of the GI tract [47, 48], and we found that both receptor subtypes were expressed in ICC and smooth muscle cells (SMC) from freshly dispersed and cultured preparations (Fig. 4) [48]
Summary
We have compared expression profiles between ICC and smooth muscle cells (SMC) and between freshly isolated ICC and cultured ICC. Cultured ICC express smooth muscle myosin, whereas freshly dispersed ICC do not. INTERSTITIAL CELLS OF CAJAL (ICC) are a unique class of cells found dispersed in gastrointestinal (GI) muscles These cells are mesenchymal in origin, and as ICC develop, they assume major roles in GI motility [29]. Studies to characterize the differences in ICC have been difficult to perform because of the problems in identifying ICC in cultures and in fresh dispersions of GI muscles. Dispersed ICC from the submucosal surface of the circular muscle layer of the canine colon are electrically rhythmic [19] and express inward and outward currents that are distinct from those of colonic smooth muscle cells [21]. It is important to perform basic characterizations of phenotype and function on fresh cells because it is possible that cells change in culture and express genes that do not necessary contribute to the mature phenotype in situ
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