Ca2+ sensitivity of the maxi chloride channel in interstitial cells of Cajal

Yangyin Runchang Decoction Improves Intestinal Motility in Mice with Atropine/Diphenoxylate-Induced Slow-Transit Constipation

This study assessed the efficacy and mechanism of action of Yangyin Runchang decoction (YRD) in the treatment of slow-transit constipation (STC). ICR mice were randomly divided into four groups (n = 10/group) and treated with saline (normal control; NC), atropine/diphenoxylate (model control; MC; 20 mg/kg), or atropine/diphenoxylate plus low-dose YRD (L-YRD; 29.6 g/kg) or high-dose YRD (H-YRD; 59.2 g/kg). Intestinal motility was assessed by evaluating feces and the intestinal transit rate (ITR). The serum level of stem cell factor (SCF) and changes in interstitial cells of Cajal (ICCs) were also evaluated. Additionally, the expression of SCF and c-kit and the intracellular Ca²⁺ concentration [Ca²⁺]_I were investigated. Fecal volume and ITR were greater in the L-YRD and H-YRD groups than in the MC group. The serum SCF level was lower in the MC group than in the NC group; this effect was ameliorated in the YRD-treated mice. Additionally, YRD-treated mice had more ICCs and elevated expression of c-kit and membrane-bound SCF, and YRD also increased [Ca²⁺]_I in vitro in isolated ICCs. YRD treatment in this STC mouse model was effective, possibly via the restoration of the SCF/c-kit pathway, increase in the ICC count, and enhancement of ICC function by increasing [Ca²⁺]_i.

The Potential for Gut Organoid Derived Interstitial Cells of Cajal in Replacement Therapy

Effective digestion requires propagation of food along the entire length of the gastrointestinal tract. This process involves coordinated waves of peristalsis produced by enteric neural cell types, including different categories of interstitial cells of Cajal (ICC). Impaired food transport along the gastrointestinal tract, either too fast or too slow, causes a range of gut motility disorders that affect millions of people worldwide. Notably, loss of ICC has been shown to affect gut motility. Patients that suffer from gut motility disorders regularly experience diarrhoea and/or constipation, insomnia, anxiety, attention lapses, irritability, dizziness, and headaches that greatly affect both physical and mental health. Limited treatment options are available for these patients, due to the scarcity of human gut tissue for research and transplantation. Recent advances in stem cell technology suggest that large amounts of rudimentary, yet functional, human gut tissue can be generated in vitro for research applications. Intriguingly, these stem cell-derived gut organoids appear to contain functional ICC, although their frequency and functional properties are yet to be fully characterised. By reviewing methods of gut organoid generation, together with what is known of the molecular and functional characteristics of ICC, this article highlights short- and long-term goals that need to be overcome in order to develop ICC-based therapies for gut motility disorders.

A Personal Perspective on the Development of Our Understanding of the Myogenic Control Mechanisms of Gut Motor Function

Myogenic control mechanisms play a role in all motor activities of the gut. Myogenic control systems are defined here as control systems that are intrinsic to the smooth muscle cells and/or interstitial cells of Cajal (ICC) and that can operate without an essential contribution of the intrinsic (ENS) and extrinsic nervous systems. In vivo however, the ENS and the myogenic control systems always work in cooperation. Although myogenic control plays a role in every gut organ, this review focuses on the peristaltic and segmentation activity of the small intestine. It provides some historical perspectives and some discussion on the development of our understanding of the cooperative nature of the myogenic and neurogenic control mechanisms. It highlights how some influential papers inadvertently provided hindrance to full understanding, it discusses how the guinea pig model has hampered acceptance of myogenic control systems and it provides some background into the genesis of our understanding of control mechanisms involving ICC.

Interstitial cells of Cajal: update on basic and clinical science

The basic science and clinical interest in the networks of interstitial cells of Cajal (ICC) keep growing, and here, research from 2010 to mid-2013 is highlighted. High-resolution gastrointestinal manometry and spatiotemporal mapping are bringing exciting new insights into motor patterns, their function and their myogenic and neurogenic origins, as well as the role of ICC. Critically important knowledge is emerging on the partaking of PDGFRα+ cells in ICC pacemaker networks. Evidence is emerging that ICC and PDGFRα+ cells have unique direct roles in muscle innervation. Chronic constipation is associated with loss and injury to ICC, which is stimulating extensive research into maintenance and repair of ICC after injury. In gastroparesis, high-resolution electrical and mechanical studies are beginning to elucidate the pathophysiological role of ICC and the pacemaker system in this condition. Receptors and ion channels that play a role in ICC function are being discovered and characterized, which paves the way for pharmacological interventions in gut motility disorders through ICC.

Roles of interleukin-9 in the growth and cholecystokinin-induced intracellular calcium signaling of cultured interstitial cells of Cajal

Interstitial cells of Cajal (ICC) are pacemaker cells in the gastrointestinal (GI) tract and loss of ICC is associated with many GI motility disorders. Previous studies have shown that ICC have the capacity to regenerate or restore, and several growth factors are critical to their growth, maintenance or regeneration. The present study aimed to investigate the roles of interleukin-9 (IL-9) in the growth, maintenance and pacemaker functions of cultured ICC. Here, we report that IL-9 promotes proliferation of ICC, and culturing ICC with IL-9 enhances cholecystokinin-8-induced Ca²⁺ transients, which is probably caused by facilitating maintenance of ICC functions under culture condition. We also show co-localizations of cholecystokinin-1 receptor and IL-9 receptor with c-kit by double-immunohistochemical labeling. In conclusion, IL-9 can promote ICC growth and help maintain ICC functions; IL-9 probably performs its functions via IL-9 receptors on ICC.

Computational modeling of anoctamin 1 calcium-activated chloride channels as pacemaker channels in interstitial cells of Cajal

Interstitial cells of Cajal (ICC) act as pacemaker cells in the gastrointestinal tract by generating electrical slow waves to regulate rhythmic smooth muscle contractions. Intrinsic Ca(2+) oscillations in ICC appear to produce the slow waves by activating pacemaker currents, currently thought to be carried by the Ca(2+)-activated Cl(-) channel anoctamin 1 (Ano1). In this article we present a novel model of small intestinal ICC pacemaker activity that incorporates store-operated Ca(2+) entry and a new model of Ano1 current. A series of simulations were carried out with the ICC model to investigate current controversies about the reversal potential of the Ano1 Cl(-) current in ICC and to predict the characteristics of the other ion channels that are necessary to generate slow waves. The model results show that Ano1 is a plausible pacemaker channel when coupled to a store-operated Ca(2+) channel but suggest that small cyclical depolarizations may still occur in ICC in Ano1 knockout mice. The results predict that voltage-dependent Ca(2+) current is likely to be negligible during the slow wave plateau phase. The model shows that the Cl(-) equilibrium potential is an important modulator of slow wave morphology, highlighting the need for a better understanding of Cl(-) dynamics in ICC.

Cholinergic signalling-regulated KV7.5 currents are expressed in colonic ICC-IM but not ICC-MP

Interstitial cells of Cajal (ICC) and the enteric nervous system orchestrate the various rhythmic motor patterns of the colon. Excitation of ICC may evoke stimulus-dependent pacemaker activity and will therefore have a profound effect on colonic motility. The objective of the present study was to evaluate the potential role of K(+) channels in the regulation of ICC excitability. We employed the cell-attached patch clamp technique to assess single channel activity from mouse colon ICC, immunohistochemistry to determine ICC K(+) channel expression and single cell RT-PCR to identify K(+) channel RNA. Single channel activity revealed voltage-sensitive K(+) channels, which were blocked by the KV7 blocker XE991 (n = 8), which also evoked inward maxi channel activity. Muscarinic acetylcholine receptor stimulation with carbachol inhibited K(+) channel activity (n = 8). The single channel conductance was 3.4 ± 0.1 pS (n = 8), but with high extracellular K(+), it was 18.1 ± 0.6 pS (n = 22). Single cell RT-PCR revealed Ano1-positive ICC that were positive for KV7.5. Double immunohistochemical staining of colons for c-Kit and KV7.5 in situ revealed that intramuscular ICC (ICC-IM), but not ICC associated with the myenteric plexus (ICC-MP), were positive for KV7.5. It also revealed dense cholinergic innervation of ICC-IM. ICC-IM and ICC-MP networks were found to be connected. We propose that the pacemaker network in the colon consists of both ICC-MP and ICC-IM and that one way of exciting this network is via cholinergic KV7.5 channel inhibition in ICC-IM.

Gating of maxi channels observed from pseudo-phase portraits

Phase space has been used to visualize and analyze the dynamic behavior of stochastic and chaotic systems. We applied this concept to maxi channels recorded from excised inside-out patches of in situ interstitial cells of Cajal. Pseudo-phase portraits of channel current were fairly homogeneous from patch to patch. They showed three main peaks, α, β, and γ, in increasing conductance. These represented single or near aggregated states. The α-peak was the closed state. The β-peak was small, consisting of a single conductance state, or in some cases two (a doublet). The β-peak state(s) had a long lifetime and displayed a characteristic behavior of frequent short transitions to γ but not to α. It was always preceded by a short series of α/γ-transitions. The γ-peak was the largest and consisted of a large number of conductance states with fast state transitions, sometimes to the extent of causing a diffusive-type behavior. Phase portraits allowed us to construct a provisional gating scheme for the maxi channel and suggest that further analysis of recordings in higher dimensional phase space and with related techniques may be promising.