Colonic Dysmotility in Murine Partial Colonic Obstruction Due to Functional Changes in Interstitial Cells

Abstract

Background/Aims Interstitial cells play important roles in gastrointestinal (GI) neuro-smooth muscle transmission. The underlying mechanisms of colonic dysmotility have not been well illustrated. We established a partial colon obstruction (PCO) mouse model to investigate the changes of interstitial cells and the correlation with colonic motility. Methods Western blot technique was employed to observe the protein expressions of Kit, platelet-derived growth factor receptor-α (Pdgfra), Ca 2+-activated Cl-(Ano1) channels, and small conductance Ca 2+-activated K + (SK) channels. Colonic migrating motor complexes (CMMCs) and isometric force measurements were employed in control mice and PCO mice. Results PCO mice showed distended abdomen and feces excretion was significantly reduced. Anatomically, the colon above the obstructive silicone ring was obviously dilated. Kit and Ano1 proteins in the colonic smooth muscle layer of the PCO colons were significantly decreased, while the expression of Pdgfra and SK3 proteins were significantly increased. The effects of a nitric oxide synthase inhibitor (L-NAME) and an Ano1 channel inhibitor (NPPB) on CMMC and colonic spontaneous contractions were decreased in the proximal and distal colons of PCO mice. The SK agonist, CyPPA and antagonist, apamin in PCO mice showed more effect to the CMMCs and colonic smooth muscle contractions. Conclusions Colonic transit disorder may be due to the downregulation of the Kit and Ano1 channels and the upregulation of SK3 channels in platelet-derived growth factor receptor-α positive (PDGFRα +) cells. The imbalance between interstitial cells of Cajal-Ano1 and PDGFRα-SK3 distribution might be a potential reason for the colonic dysmotility.

Injury of Partial Colon Obstruction in Colonic Interstitial Cells With/Without Interstitial Cells of Cajal

“…As shown in Figure 2B, application of NPPB (5-Nitro-2-[3-phenylpropylamino] benzoic acid, 10 µM) inhibited slow wave, which is consistent to the study. 4 As shown in Figure 2C, the application of apamin (1 µM) did not affect the slow wave frequency illustrating that ICC are without SK3 channel, consistent with other studies. 5,6 Note, the slow wave amplitude shown is above the half of average, thus not counted as change.…”

“…Secondly, electrophysiological measurements have shown that a specific antagonist of SK chan-nels on CMMCs which cannot be accounted for the targeting on PDGFRα + cells since SMCs and neurons are also enriched with SK3. We provide here an example as shown in Figure 2 to illustrate isolated slow wave which may support the study of Wang et al 4 Slow wave activity was recorded in normal mice under the similar conditions as described by Wang et al, 4 except for the presence of tetrodotoxin (TTX) 1 µM (neuronal activity blocker) and nifedipine 1 µM (L-type calcium channel blocker inhibiting muscular activity). This is the classic activity for slow waves reflecting ICC unique activity.…”

“…1E and 1F). 4 Here, what was found by Wang et al 4 in the study is apparently new but there are some vaguenesses to be clarified such as interstitial cells and ICC, colonic migrating motor complexes (CMMCs), and slow waves. Firstly, whole muscle extracts would have contained protein from all cells of the layer including smooth muscle cells (SMCs), PDGFRα + , and neurons with which western blot for SK3 protein expression was not proper for PDGFRα + cells, unless measured in cells sorted, or someway purified.…”

“…The alteration or ablation of such motility inhibitory device may result in colonic motility function disorder and/or anatomic injury. [1][2][3] Wang et al 4 recently published a study "Colonic dysmotility in murine partial colonic obstruction due to functional changes in interstitial cells" in which a partial colon obstruction mouse model was evaluated. After 7 days of partial colon obstruction an astonishing observation was found, ie, colonic smooth muscle layers were increased as hypertrophic in both weight and thickness, compared to the control model at the same length scale ( Fig.…”

Interstitial cells of Cajal and human colon motility in health and disease

“…The dilated sections showed muscle hypertrophy but normal responses to cholinergic stimulation, whereas the transition zone with luminal narrowing showed a marked reduction in response to cholinergic stimulation with loss of ganglia and variable levels of ICC network reduction (218). In a murine model of partial obstruction and proximal dilation, ICC were reduced and PDGFR-a þ cells upregulated, correlated with a decrease in the generation of colonic motor complexes (219). ICC loss in the hypertrophic muscle in the dilated segment was correlated with loss of stem cell factor and an increase in TNF-a (220).…”