Interstitial cells of Cajal: Transcriptional profiling and fate in gastrointestinal dysmotilities

Interstitial cells of Cajal (ICC) play key roles in gastrointestinal (GI) motility, and undergo depletion in, and contribute to the pathophysiology of, a variety of GI motor disorders.We developed a technique to selectively harvest from murine small intestinal muscles ICC located in the myenteric region (ICC-MY) and ICC associated with the deep muscular plexus (ICC-DMP). ICC-DMP were detected in suspension by fluorescent microscopy and harvested for RT-PCR using micropipettes. ICC-DMP expressed receptors for a variety of excitatory and inhibitory neurotransmitters and genes related to postreceptor signaling. ICC-DMP and ICC-MY were also simultaneously detected and enumerated by flow cytometry and sorted to purity by fluorescence-activated cell sorting. The sorted ICC-DMP and ICC-MY cells were processed for microarray analysis. The function of ICC-MY as pacemaker cells was reflected by the more abundant expression of certain genes that may be involved in the generation and propagation of electrical slow waves, such as Trpm7, Cacna1h, Kcnk3 and mitochondrial genes. In contrast, there was no difference in the transcriptional expression of neurotransmitter receptors and postsynaptic proteins between ICC classes and intestinal muscle. The higher expression of genes related to G protein signaling in ICC-DMP may contribute to their role in mediating neuromuscular neurotransmission.We also investigated murine models of GI dysmotilites that involve ICC loss. We verified the previously reported smooth muscle atrophy, ICC loss, and reduced neuron-specific gene expression in diabetic GI muscles using microarray analysis. There were also signs of reduced intercellular communication including reduced expression of GTP-binding proteins. We also identified a number of growth factors and receptor tyrosine kinases for which gene expression was reduced in diabetic muscles. In the second set of pathophysiological studies we investigated possible causes of ICC depletion in a murine model of partial intestinal obstruction. We found subtle signs of increased activity of CD11b + cells in the intestinal muscles oral to the site of obstruction. These cells are known to release inflammatory mediators that may play a role in the pathogenesis of ICC loss. The findings in these studies help to understand the function of ICC in GI motility and their fate in GI dysmotility.