Differential gene expression in the murine gastric fundus lacking interstitial cells of Cajal.

BACKGROUND: The muscle layers of murine gastric fundus have no interstitial cells of Cajal at the level of the myenteric plexus and only possess intramuscular interstitial cells and this tissue does not generate electric slow waves. The absence of intramuscular interstitial cells in W/WV mutants provides a unique opportunity to study the molecular changes that are associated with the loss of these intercalating cells. METHOD: The gene expression profile of the gastric fundus of wild type and W/WV mice was assayed by murine microarray analysis displaying a total of 8734 elements. Queried genes from the microarray analysis were confirmed by semi-quantitative reverse transcription-polymerase chain reaction. RESULTS: Twenty-one genes were differentially expressed in wild type and W/WV mice. Eleven transcripts had 2.0-2.5 fold higher mRNA expression in W/WV gastric fundus when compared to wild type tissues. Ten transcripts had 2.1-3.9 fold lower expression in W/WV mutants in comparison with wild type animals. None of these genes have ever been implicated in any bowel motility function. CONCLUSIONS: These data provides evidence that several important genes have significantly changed in the murine fundus of W/WV mutants that lack intramuscular interstitial cells of Cajal and have reduced enteric motor neurotransmission

Differential gene expression profile in the small intestines of mice lacking pacemaker interstitial cells of Cajal.

BACKGROUND: We previously identified eight known and novel genes differentially expressed in the small intestines of wild type and W/WV mice, which have greatly reduced populations of the interstitial cells of Cajal, that are responsible for the generation of electrical slow waves, by using a differential gene display method. METHODS: By using the same method we isolated additional candidate genes that were specifically down- or up-regulated in W/WV mice. Novel transcripts were designated as DDWMEST. RESULTS: We isolated seven candidates that were specifically down- or up-regulated in W/WV mice. Two novel transcripts, DDWMEST 1 and -91 were increased in both fed and fasted W/WV mice. Expression of another five genes was suppressed in W/WV mice: ARG2 (Arginase II), ONZIN (encoding leukemia inhibitory factor regulated protein), and three novel transcripts: DDWMEST62, -84, and -100. Together with the previous report, we identified fifteen differentially expressed genes in total in the small intestines of W/WV mice. Eight of these genes were reduced in the jejunums of W/WV mice compared to age matched wild type mice, whereas the other seven genes showed an increase in expression. Differential expression was the same in fasted and fed animals, suggesting that the differences were independent of the dietetic state of the animal. CONCLUSIONS: Several known and novel genes are differentially expressed in the small intestines of W/WV mice. Differential gene comparison might contribute to our understanding of motility disorders associated with the loss of the interstitial cells of Cajal.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Role of detrusor PDGFRα+ cells in mouse model of cyclophosphamide-induced detrusor overactivity

Cyclophosphamide (CYP)-induced cystitis is a rodent model that shares many features common to the cystitis occurring in patients, including detrusor overactivity (DO). Platelet-derived growth factor receptor alpha positive (PDGFRα(+)) cells have been proposed to regulate muscle excitability in murine bladders during filling. PDGFRα(+) cells express small conductance Ca(2+)-activated K(+) channels (predominantly SK3) that provide stabilization of membrane potential during filling. We hypothesized that down-regulation of the regulatory functions of PDGFRα(+) cells and/or loss of PDGFRα(+) cells generates the DO in CYP-treated mice. After CYP treatment, transcripts of Pdgfrα and Kcnn3 and PDGFRα and SK3 protein were reduced in detrusor muscle extracts. The distribution of PDGFRα(+) cells was also reduced. Inflammatory markers were increased in CYP-treated detrusor muscles. An SK channel agonist, CyPPA, increased outward current and hyperpolarization in PDGFRα(+) cells. This response was significantly depressed in PDGFRα(+) cells from CYP-treated bladders. Contractile experiments and ex vivo cystometry showed increased spontaneous contractions and transient contractions, respectively in CYP-treated bladders with a reduction of apamin sensitivity, that could be attributable to the reduction in the SK conductance expressed by PDGFRα(+) cells. In summary, PDGFRα(+) cells were reduced and the SK3 conductance was downregulated in CYP-treated bladders. These changes are consistent with the development of DO after CYP treatment

Interstitial cells of cajal mediate cholinergic neurotransmission from enteric motor neurons

Copyright © 2000 Society for NeuroscienceInterstitial cells of Cajal (ICC) are interposed between enteric neurons and smooth muscle cells in gastrointestinal muscles. The role of intramuscular ICC (IC-IM) in mediating enteric excitatory neural inputs was studied using gastric fundus muscles of wild-type animals and W/Wv mutant mice, which lack IC-IM. Excitatory motor neurons, labeled with antibodies to vesicular acetylcholine transporter or substance-P, were closely associated with IC-IM. Immunocytochemistry showed close contacts between enteric neurons and IC-IM. IC-IM also formed gap junctions with smooth muscle cells. Electrical field stimulation yielded fast excitatory junction potentials in the smooth muscle that were blocked by atropine. Neural responses were greatly reduced in muscles of W/Wv animals. Loss of cholinergic responses in W/Wv muscles seemed to be caused by the loss of close synaptic contacts between motor neurons and IC-IM, because these muscles were not less responsive to exogenous acetylcholine than were wild-type muscles. W/Wv muscles also responded to excitatory nerve stimulation when the breakdown of acetylcholine was blocked by neostigmine. The density of cholinergic nerve bundles within the muscles was not significantly different in wild-type and W/Wv muscles, and similar amounts of 14[C]choline were released from preloaded wild-type and W/Wv muscles in response to nerve stimulation. The impact of losing IC-IM on gastric compliance was also evaluated in intact stomachs. Pressure increased as a function of fluid volume and infusion rate in wild-type animals, but W/Wv animals showed little basal tone and minimal increases in pressure with fluid infusions. These data suggest that IC-IM play a major role in receiving cholinergic excitatory inputs from the enteric nervous system in the murine fundus.Sean M. Ward, Elizabeth A. H. Beckett, XuanYu Wang, Fred Baker, Mohammad Khoyi, and Kenton M. Sander

Differential gene expression profile in the small intestines of mice lacking pacemaker interstitial cells of Cajal

BACKGROUND: We previously identified eight known and novel genes differentially expressed in the small intestines of wild type and W/W(V )mice, which have greatly reduced populations of the interstitial cells of Cajal, that are responsible for the generation of electrical slow waves, by using a differential gene display method. METHODS: By using the same method we isolated additional candidate genes that were specifically down- or up-regulated in W/W(V )mice. Novel transcripts were designated as DDWMEST. RESULTS: We isolated seven candidates that were specifically down- or up-regulated in W/W(V )mice. Two novel transcripts, DDWMEST 1 and -91 were increased in both fed and fasted W/W(V )mice. Expression of another five genes was suppressed in W/W(V )mice: ARG2 (Arginase II), ONZIN (encoding leukemia inhibitory factor regulated protein), and three novel transcripts: DDWMEST62, -84, and -100. Together with the previous report, we identified fifteen differentially expressed genes in total in the small intestines of W/W(V )mice. Eight of these genes were reduced in the jejunums of W/W(V )mice compared to age matched wild type mice, whereas the other seven genes showed an increase in expression. Differential expression was the same in fasted and fed animals, suggesting that the differences were independent of the dietetic state of the animal. CONCLUSIONS: Several known and novel genes are differentially expressed in the small intestines of W/W(V )mice. Differential gene comparison might contribute to our understanding of motility disorders associated with the loss of the interstitial cells of Cajal

MicroRNAs Dynamically Remodel Gastrointestinal Smooth Muscle Cells

Smooth muscle cells (SMCs) express a unique set of microRNAs (miRNAs) which regulate and maintain the differentiation state of SMCs. The goal of this study was to investigate the role of miRNAs during the development of gastrointestinal (GI) SMCs in a transgenic animal model. We generated SMC-specific Dicer null animals that express the reporter, green fluorescence protein, in a SMC-specific manner. SMC-specific knockout of Dicer prevented SMC miRNA biogenesis, causing dramatic changes in phenotype, function, and global gene expression in SMCs: the mutant mice developed severe dilation of the intestinal tract associated with the thinning and destruction of the smooth muscle (SM) layers; contractile motility in the mutant intestine was dramatically decreased; and SM contractile genes and transcriptional regulators were extensively down-regulated in the mutant SMCs. Profiling and bioinformatic analyses showed that SMC phenotype is regulated by a complex network of positive and negative feedback by SMC miRNAs, serum response factor (SRF), and other transcriptional factors. Taken together, our data suggest that SMC miRNAs are required for the development and survival of SMCs in the GI tract

Measuring Gastrointestinal Electrical Activity With Extracellular Electrodes: Author's Reply

Letter to the Edito