Interstitial Cells Of Cajal Networks Research Articles

Supervised Machine Learning Segmentation and Quantification of Gastric Pacemaker Cells.

Interstitial Cells of Cajal (ICC) are specialized pacemaker cells that generate and actively propagate electrophysiological events called slow waves. Slow waves regulate the motility of the gastrointestinal tract necessary for digesting food. Degradation in the ICC network structure has been qualitatively associated to several gastrointestinal motility disorders. ICC network structure can be obtained using confocal microscopy, but the current limitations in imaging and segmentation techniques have hindered an accurate representation of the networks. In this study, supervised machine learning techniques were applied to extract the ICC networks from 3D confocal microscopy images. The results showed that the Fast Random Forest classification method using Trainable WEKA Segmentation outperformed the Decision Table and Naïve Bayes classification methods in sensitivity, accuracy, and F-measure. Using the Fast Random Forest classifier, 12 gastric antrum tissue blocks were segmented and variations in ICC network thickness, density and process width were quantified for the myenteric plexus ICC network (the primary pacemakers). Our findings demonstrated regional variation in ICC network density and thickness along the circumferential and longitudinal axis of the mouse antrum. An inverse relationship was observed in the distal and proximal antrum for density (proximal: 9.8±4.0% vs distal: 7.6±4.6%) and thickness (proximal: 15±3 μm vs distal: 24±10 μm). Limited variation in ICC process width was observed throughout the antrum (5±1 μm).Clinical Relevance- Detailed quantification of regional ICC structural properties will provide insights into the relationship between ICC structure, slow waves and resultant gut motility. This will improve techniques for the diagnosis and treatment of functional GI motility disorders.

Design of a closed-loop gastric pacemaker for modulating dysrhythmic conduction patterns via extracellular potentials.

A potential treatment option for chronic and severe motility disorders such as gastroparesis is the implantation of a Gastric Electrical Stimulator (GES), which is designed to modulate the bio-electric slow waves. However, the effectiveness of current GESs remains uncertain since they do not work in a closed-loop by sensing, processing, and modulating the dysrhythmic patterns. This work presents the design of a GES model working in closed-loop with the network of the Interstitial Cells of Cajal (ICC). A pre-existing two-dimensional ICC network is enhanced by proposing an extracellular potential generation model, which can precisely capture the timing behaviour of slow wave propagation pattern of the simulated ICC network. The GES senses the extracellular potential, detects bradygastric patterns and finally modulates the activity to ensure normal conduction. The GES is designed to be practical for ease of validation and implementation.

On a coupled electro-chemomechanical model of gastric smooth muscle contraction

The stomach is a central organ in the gastrointestinal tract that performs a variety of functions, in which the spatio-temporal organisation of active smooth muscle contraction in the stomach wall (SW) is highly regulated. In the present study, a three-dimensional model of the gastric smooth muscle contraction is presented, including the mechanical contribution of the mucosal and muscular layer of the SW. Layer-specific and direction-dependent model parameters for the active and passive stress-stretch characteristics of the SW were determined experimentally using porcine smooth muscle strips. The electrical activation of the smooth muscle cells (SMC) due to the pacemaker activity of the interstitial cells of Cajal (ICC) is modelled by using FitzHugh-Nagumo-type equations, which simulate the typical ICC and SMC slow wave behaviour. The calcium dynamic in the SMC depends on the SMC membrane potential via a gaussian function, while the chemo-mechanical coupling in the SMC is modelled via an extended Hai-Murphy model. This cascade is coupled with an additional mechano-electrical feedback-mechanism, taking into account the mechanical response of the ICC and SMC due to stretch of the SW. In this way the relaxation responses of the fundus to accommodate incoming food, as well as the typical peristaltic contraction waves in the antrum for mixing and transport of the chyme, have been well replicated in simulations performed at the whole organ level. Statement of SignificanceIn this article, a novel three-dimensional electro-chemomechanical model of the gastric smooth muscle contraction is presented. The propagating waves of electrical membrane potential in the network ofinterstitial cells of Cajal (ICC) and smooth muscle cells (SMC) lead to a global pattern of change in the calciumdynamics inside the SMC. Taking additionally into account the mechanical response of the ICC and SMC due to stretch of the stomach wall, also referred to as mechanical feedback-mechanism, the result is a complex spatio-temporal regulation of the active contraction and relaxation of the gastric smooth muscle tissue. Being a firstapproach, in future view such a three-dimensional model can give an insight into the complexload transferring system of the stomach wall, as well as into the electro-chemomechanicalcoupling process underlying smooth muscle contraction in health and disease.

Altered Distribution of Interstitial Cells of Cajal in Normoganglionic and Transitional Zone of Hirschsprung Disease and Their Clinical Significance

Objective − The aim of this study was to evaluate interstitial cells of Cajal (ICC) in Hirschsprung disease (HD), especially in children who had postsurgical problems. Material and Methods − The study included tissue samples of normoganglionic (NZ) and transitional zone (TZ) of 33 HD pediatric patients. Samples of bowel from 10 autopsy controls who did not have dysmotility were also analyzed. Hematoxylin-eosin (H&E) and immunohistochemical (MAP-2 and c-Kit (CD117)) staining were performed. Myenteric ganglia were analyzed at 5 microscopic fields H&E and MAP-2 stained sections (magnification 400×). The diameters of the submucosal nerves were measured at 3 microscopic H&E fields (magnification 400×). The ICC were analyzed on c-Kit immunostained slides at 3 microscopic fields per each bowel layer (magnification 200×): deep submucosa, circular and longitudinal muscular layer and zone of myenteric plexus. Results − The myenteric ganglion cell count was significantly lower in TZ of all children with HD, while there were no significant differences in NZ between the study group and age-matched controls. The ICC network was affected in all cases of HD. The total ICC count was significantly lower in NZ than in control (P<0.001). A critically lower ICC count (<50% of minimal ICC count in the control group) in the NZ was found in patients with postoperative problems (constipation and enterocolitis). Conclusion − Decreased count of the ICC in the NZ could be the cause of intestinal motility difficulties in the postoperative period in children with HD.

A118 GUT MICROBIOTA TRANSPLANTATION FROM A PATIENT WITH SEVERE CONSTIPATION INDUCED CHANGES IN COLONIC FUNCTION AND STRUCTUR OF GNOTOBIOTIC MICE

Abstract Background Increasing evidence suggests that gut microbiota play a key role in gastrointestinal (GI) tract function. We have previously shown that fecal microbiota transplantation diarrhea predominant IBS patients into germ-free mice induces faster GI transit, increased permeability and innate immune activation. However, it is unknown whether gut dysfunction is induced by microbiota from patients with chronic constipation. Aims Here, we investigated the role of the intestinal microbiota in the expression of severe slow transit constipation in a patient with previous C difficile infection and extensive antibiotic exposure. Methods Germ-free (GF) mice (14 weeks old) were gavaged with diluted fecal content from the patient with constipation (PA) or a sex and age-matched healthy control (HC). 12 weeks later, we assessed gut motility and GI transit using videofluoroscopy and a bead expulsion test.. We then investigated intestinal and colonic smooth muscle isometric contraction in vitro using electric field stimulation (EFS), and acetylcholine (Ach) release was assessed by superfusion using [3H] choline. Histological changes were evaluated by H&amp;E and immunohistochemistry. Results Mice with PA microbiota had faster whole GI transit (score 18.9 ± 0.9 (N=9) than mice with HC microbiota (15.4 ± 1.0, N=10, p=0.032), with markers located mainly in the distal small bowel and cecum. However, bead expulsion from the colon was significantly longer in PA mice (420.8 s ± 124.6 s, N=9) than in HC mice (82.6 s ± 20.0 s, N=10, p=0.026). This delayed colonic transit was likely due to colonic retroperistalsis visualized videofluoroscopically by retrograde flow of barium in the right colon of PA mice. There was no difference between the two groups in small intestinal or colonic tissues in Ach release or contractility induced by carbachol or KCl,. EFS caused transient biphasic relaxation and contraction in small intestine and colon, with the colonic contraction being stronger in the PA group. Microscopic tissue analysis showed disruption of the interstitial cells of Cajal (ICC) network and increased lymphocyte infiltration in colonic mucosa and submucosa in PA mice. Conclusions These results indicate that the microbiota is a driver of delayed colonic transit in a patient whose constipation started following extensive antibiotic exposure for C. difficile infection. The observed dysmotility pattern was not due to lower muscle contractility but likely caused by immune mediated changes in the ICC network. Funding Agencies CIHR

A novel approach for model-based design of gastric pacemakers

Understanding the slow wave propagation patterns of Interstitial Cells of Cajal (ICC) is essential when designing Gastric Electrical Stimulators (GESs) to treat motility disorders. A GES with the ability to both sense and pace, working in closed-loop with the ICC, will enable efficient modulation of Gastrointestinal (GI) dysrhythmias. However, existing GESs targeted at modulating GI dysrhythmias operate in an open-loop and hence their clinical efficacy is uncertain. This paper proposes a novel model-based approach for designing GESs that operate in closed-loop with the GI tract. GES is modelled using Hybrid Input Output Automata (HIOA), a well-known formal model, which is suitable for designing safety-critical systems. A two-dimensional ICC network working in real-time with the GES is developed using the same compositional HIOA framework. The ICC network model is used to simulate normal and diseased action potential propagation patterns akin to those observed during GI dysrhythmias. The efficacy of the proposed GES is then validated by integrating it in closed-loop with the ICC network. Results show that the proposed GES is able to sense the propagation patterns and modulate the dysrhythmic patterns of bradygastria back to its normal state automatically. The proposed design of the GES is flexible enough to treat a variety of diseased dysrhythmic patterns using closed-loop operation.

Hyperglycemia in the early stages of type 1 diabetes accelerates gastric emptying through increased networks of interstitial cells of Cajal.

Gastric emptying (GE) can be either delayed or accelerated in diabetes mellitus (DM). However, most research has focused on delayed GE mediated by a chronic hyperglycemic condition in DM. As such, the function of GE in the early stages of DM is not well understood. Interstitial cells of Cajal (ICC) are pacemaker cells in the gastrointestinal tract. In the present study, we investigated changes in GE and ICC networks in the early stages of DM using a streptozotocin-induced type 1 diabetic mouse model. The changes in GE were measured by the 13C-octanoic acid breath test. ICC networks were immunohistochemically detected by an antibody for c-Kit, a specific marker for ICC. Our results showed that GE in type 1 DM was significantly accelerated in the early stages of DM (2–4 weeks after onset). In addition, acute normalization of blood glucose levels by a single administration of insulin did not recover normal GE. ICC networks of the gastric antrum were significantly increased in DM and were not affected by the acute normalization of blood glucose. In conclusion, our results suggest that GE is accelerated in the early stages of DM, and it is associated with increased ICC networks. This mechanism may help to clarify a link between the onset of DM and GE disorders.

Myenteric networks of interstitial cells of Cajal are reduced in horses with inflammatory bowel disease.

Inflammatory bowel disease (IBD) is a well-recognised but poorly understood disease complex in the horse. Clinical signs may vary but often include weight loss, diarrhoea and colic. The effect this disease process may have on the gastrointestinal pacemaker cells (the interstitial cells of Cajal), enteric neurons and glial cells has not been previously evaluated in the horse. To compare the density of the interstitial cells of Cajal (ICC), enteric neurons and glial cells in horses with IBD to those of normal horses using immunohistochemical markers. Retrospective, quantitative immunohistochemical study. Ileal samples were collected during post-mortem examinations from 14 horses with a clinical and histopathological diagnosis of IBD and from eight normal controls. All horses were Standardbreds 1-15years of age. Six of the IBD cases had eosinophilic gastroenteritis (EG) while the remaining eight had granulomatous enteritis (GE). Tissue sections were labelled with anti-CD117 (c-Kit), anti-TMEM16 (TMEM16), anti-protein gene product (PGP9.5) and anti-glial fibrillary acidic protein (GFAP) using standard immunohistochemical labelling techniques. Image analysis was performed to quantify the presence of ICC (CD117, TMEM16) as well as neuronal (PGP9.5) and enteroglial (GFAP) networks. Interstitial cells of Cajal networks were significantly reduced in the myenteric plexus (MP) region in IBD horses compared with the controls for both markers (P<0.05). There was no significant difference in the density of the neuronal or glial cell markers between the two groups (P>0.05). The number of horses included in the study. Disruption to ICC networks may contribute to the clinical signs of colic in some horses with IBD. Further studies are needed to establish the pathophysiological mechanisms involved and the functional effects of the reduced ICC networks.

Da-Cheng-Qi Decoction () Combined with Lactobacillus Acidophilus Improves Gastrointestinal Function of Traumatic Brain-Injured Model Mice.

To investigate the effects of Da-Cheng-Qi Decoction (DCQD, ) combined with Lactobacillus acidophilus (LA) on the recovery of gastrointestinal (GI) function in traumatic brain-injured (TBI) mice. A total of 150 male C57BL/6 mice were randomly divided into sham-injury, normal saline (NS), DCQD (0.4 mL/day), LA (⩾1 × 1010 cfu/day LA), DCQD+LA (LA administration at the same dosage after 4 h of feeding DCQD), and ½ DCQD+LA groups (LA administration at the same dosage after 4 h of feeding ½ DCQD dose) by a random number table, 5-8 mice in each group. The sever TBI model was constructed according to Feeney's enhanced gravitational forces of free falling. On days 1, 3, and 7 post-TBI, plasma diamine oxidase (DAO) and D-lactic acid levels were assessed by enzyme-linked immunosorbent assay (ELISA). Occludin expression in the intestinal epithelium was assessed by Western blot analysis. Transmission electron microscopy (TEM) was used to observe the morphological changes in the network structure of interstitial cells of Cajal (ICC) and change of enteric nervous system-ICC-smooth muscle cell (ENS-ICC-SMC). Immunofluorescence staining was used to detect changes in the network structure of the ICC. Compared with the NS group, occludin expression in the DCQD+LA group significantly increased on Day 1, 3, and 7 post-TBI (P<0.05 or P<0.01). The concentration of DAO significantly decreased in the LA, DCQD, and DCQD+LA groups on Day 3 and 7, whilst the D-lactate concentrations in the LA and ½ DCQD+LA groups decreased on Day 1 and 3 post-injury (P<0.05 or P<0.01). The NS group experienced a great damage on the ENS-ICC-SMC network morphology and ICC network structure, and all treatment groups had some improvements, among which the DCQD+LA group presented relatively intact network morphology. DCQD combined with LA treatment could effectively repair the intestinal mucosal barrier and improve GI motility in mice after TBI. The combination of DCQD and LA was more effective than their respective monotherapies.

Electroacupuncture Accelerates the Delayed Intestinal Transit in POI by Suppressing M1 Like Muscularis Macrophages and IL6 Secretion

Background: Electroacupuncture (EA) at ST-36 could accelerate the delayed gastrointestinal (GI) motility in many GI motility dysfunction models, but the definite effect and mechanisms are unclear. In this study, We intended to investigate the effects of EA on intestinal manipulation (IM) mice model and involved mechanisms. Methods: Male C57BL/6 mice were randomized into five groups: normal control, intestinal manipulation (IM), IM with sham EA (SEA), IM with high-frequency EA (HEA) and IM with low-frequency EA (LEA). The GI transit was evaluated. The infiltration of muscularis macrophages (MMφ) and its phenotype were analysed with flow cytometry. Magnetic-activated cell sorting was applied to isolate MMφ, and the relationship between the MMφ and interstitial cells of Cajal (ICCs) was further investigated. Results: (1) Compared with the IM group, HEA and LEA attenuated the delayed intestinal transit. (2) Both the HEA and LEA obviously reduced the MMφ and supressed the M1 activation of the MMφ in the ileum. (3) EA restored the disrupted ICC networks through inhibiting the release of IL6 by the MMφ. Conclusion: (1)EA at acupoint ST-36 could accelerate the delayed intestinal transit in the IM murine model by restoring the ICC networks. (2)EA protected the ICCs through reducing the MMφ, inhibiting its M1 polarization and its IL6 secretion. Funding Statement: The work was supported by grants from the National Natural Science Foundation of China (nos. 81570488; nos. 81770536). Declaration of Interests: The authors declare they have no conflict interests. Ethics Approval Statement: This study was carried out in accordance with the principles of the Guide for the Care and Use of Laboratory Animals of Tongji Medical College, the Committee of Experimental Animals of Tongji Medical College of Huazhong University of Science and Technology.

Pacemaker network properties determine intestinal motor pattern behaviour.

Pacemaker network properties determine intestinal motor pattern behaviour.

Spontaneous Electrical Activity and Rhythmicity in Gastrointestinal Smooth Muscles.

The gastrointestinal (GI) tract has multifold tasks of ingesting, processing, and assimilating nutrients and disposing of wastes at appropriate times. These tasks are facilitated by several stereotypical motor patterns that build upon the intrinsic rhythmicity of the smooth muscles that generate phasic contractions in many regions of the gut. Phasic contractions result from a cyclical depolarization/repolarization cycle, known as electrical slow waves, which result from intrinsic pacemaker activity. Interstitial cells of Cajal (ICC) are electrically coupled to smooth muscle cells (SMCs) and generate and propagate pacemaker activity and slow waves. The mechanism of slow waves is dependent upon specialized conductances expressed by pacemaker ICC. The primary conductances responsible for slow waves in mice are Ano1, Ca2+-activated Cl- channels (CaCCs), and CaV3.2, T-type, voltage-dependent Ca2+ channels. Release of Ca2+ from intracellular stores in ICC appears to be the initiator of pacemaker depolarizations, activation of T-type current provides voltage-dependent Ca2+ entry into ICC, as slow waves propagate through ICC networks, and Ca2+-induced Ca2+ release and activation of Ano1 in ICC amplifies slow wave depolarizations. Slow waves conduct to coupled SMCs, and depolarization elicited by these events enhances the open-probability of L-type voltage-dependent Ca2+ channels, promotes Ca2+ entry, and initiates contraction. Phasic contractions timed by the occurrence of slow waves provide the basis for motility patterns such as gastric peristalsis and segmentation. This chapter discusses the properties of ICC and proposed mechanism of electrical rhythmicity in GI muscles.

Intestinal involvement in amyloidosis is a sequential process.

Gastrointestinal amyloidosis causes dysmotility. A comprehensive histological analysis to explain these symptoms is lacking. Therefore, we systematically examined histological features of intestinal dysmotility in patients with AL and AA amyloidosis, compared to controls. Autopsy tissue material from small bowel and colon was used for histological (semiquantitative) evaluation of the mucosa, blood vessels, muscular layers, enteric nervous system (ENS) and the interstitial cells of Cajal (ICC), using hematoxylin and eosin, periodic acid Schiff, Elastic von Gieson and Congo red staining, and immunohistochemistry with α-smooth muscle actin, HuC/D, S100 and CD117 antibodies, according to guidelines of the Gastro 2009 International Working Group. Amyloid deposits were present in the vascular walls of all amyloidosis patients. In the mucosa, amyloid was found in 67% of AA patients. The muscular layers were involved in 64% of amyloidosis patients, most prominent in AA patients, associated with the presence of polyglucosan inclusion bodies, but not with either abnormal α-actin patterns or fibrosis. Amyloid in the muscularis propria surrounding the myenteric plexus was found, but not inside the myenteric plexus. These deposits might be related to loss of the ICC network, but there was no association with decreased neuronal or nerve fiber density. We hypothesize that intestinal dysmotility in amyloidosis patients is a sequential process: amyloid deposition starts in the vasculature, followed by involvement of the muscular layers, ICC loss, and potentially affect the myenteric plexus. This final stage may be accompanied by clinical symptoms of severe intestinal dysmotility.

Bioengineering functional smooth muscle with spontaneous rhythmic contraction in vitro

Oriented smooth muscle layers in the intestine contract rhythmically due to the action of interstitial cells of Cajal (ICC) that serve as pacemakers of the intestine. Disruption of ICC networks has been reported in various intestinal motility disorders, which limit the quality and expectancy of life. A significant challenge in intestinal smooth muscle engineering is the rapid loss of function in cultured ICC and smooth muscle cells (SMC). Here we demonstrate a novel approach to maintain the function of both ICC and SMC in vitro. Primary intestinal SMC mixtures cultured on feeder cells seeded electrospun poly(3-caprolactone) scaffolds exhibited rhythmic contractions with directionality for over 10 weeks in vitro. The simplicity of this system should allow for wide usage in research on intestinal motility disorders and tissue engineering, and may prove to be a versatile platform for generating other types of functional SMC in vitro.

Interstitial cell network volume is reduced in the terminal bowel of ageing mice.

Ageing is associated with impaired neuromuscular function of the terminal gastrointestinal (GI) tract, which can result in chronic constipation, faecal impaction and incontinence. Interstitial cells of cajal (ICC) play an important role in regulation of intestinal smooth muscle contraction. However, changes in ICC volume with age in the terminal GI tract (the anal canal including the anal sphincter region and rectum) have not been studied. Here, the distribution, morphology and network volume of ICC in the terminal GI tract of 3‐ to 4‐month‐old and 26‐ to 28‐month‐old C57BL/6 mice were investigated. ICC were identified by immunofluorescence labelling of wholemount preparations with an antibody against c‐Kit. ICC network volume was measured by software‐based 3D volume rendering of confocal Z stacks. A significant reduction in ICC network volume per unit volume of muscle was measured in aged animals. No age‐associated change in ICC morphology was detected. The thickness of the circular muscle layer of the anal sphincter region and rectum increased with age, while that in the distal colon decreased. These results suggest that ageing is associated with a reduction in the network volume of ICC in the terminal GI tract, which may influence the normal function of these regions.

Disruption of the pacemaker activity of interstitial cells of Cajal via nitric oxide contributes to postoperative ileus.

Interstitial cells of Cajal (ICC) serve as intestinal pacemakers. Postoperative ileus (POI) is a gastrointestinal motility disorder that occurs following abdominal surgery, which is caused by inflammation-induced dysfunction of smooth muscles and enteric neurons. However, the participation of ICC in POI is not well understood. In this study, we investigated the functional changes of ICC in a mouse model of POI. Intestinal manipulation (IM) was performed to induce POI. At 24h or 48h after IM, the field potential of the intestinal tunica muscularis was investigated. Tissues were also examined by immunohistochemistry and electron microscopic analysis. Gastrointestinal transit was significantly decreased with intestinal tunica muscularis inflammation at 24h after IM, which was ameliorated at 48h after IM. The generation and propagation of pacemaker potentials were disrupted at 24h after IM and recovered to the control level at 48h after IM. ICC networks, detected by c-Kit immunoreactivity, were remarkably disrupted at 24h after IM. Electron microscopic analysis revealed abnormal vacuoles in the ICC cytoplasm. Interestingly, the ICC networks recovered at 48h after IM. Administration of aminoguanidine, an inducible nitric oxide synthase inhibitor, suppressed the disruption of ICC networks. Ileal smooth muscle tissue cultured in the presence of nitric oxide donor, showed disrupted ICC networks. The generation and propagation of pacemaker potentials by ICC are disrupted via nitric oxide after IM, and this disruption may contribute to POI. When inflammation is ameliorated, ICC can recover their pacemaker function.

Electroacupuncture at ST36 Increases Bone Marrow-Derived Interstitial Cells of Cajal via the SDF-1/CXCR4 and mSCF/Kit-ETV1 Pathways in the Stomach of Diabetic Mice.

Background The loss of interstitial cells of Cajal (ICC) is observed in diabetic gastroparesis. Electroacupuncture (EA) maintains ICC networks, but the effects and mechanisms of EA on ICC of bone marrow derivation in the stomach have not been investigated. Methods C57BL/6 mice were randomized into six groups: control, diabetic (DM), bone marrow transplantation (BMT) + DM, BMT + DM + sham EA (SEA), BMT + DM + low-frequency EA (LEA), and BMT + DM + high-frequency (HEA). c-Kit+GFP+ cells in the stomach were detected by immunofluorescence staining. Western blotting and qRT-PCR were employed to determine c-Kit, GFP, SDF-1, CXCR4, mSCF, pERK, and ETV1 expression. Results (1) c-Kit+GFP+ cells were elevated in the BMT + DM + LEA and HEA groups. (2) The mRNA and protein levels of GFP, SDF-1, and CXCR4 were increased in the BMT + DM + LEA and BMT + DM + HEA groups. (3) The mRNA and protein levels of mSCF, c-Kit, pERK, and ETV1 were significantly reduced in the DM group but markedly elevated in the BMT + DM + LEA and HEA groups. Conclusion EA at ST36 increases bone marrow-derived ICC in the stomach of diabetic mice via the SDF-1/CXCR4 and mSCF/c-Kit-ETV1 pathways.

The phase response and state space of slow wave contractions in the small intestine.

What is the central question of this study? What are the dynamical rules governing interstitial cell of Cajal (ICC)-generated slow wave contractions in the small intestine, as reflected in their phase response curve and state space? What is the main finding and its importance? The phase response curve has a region of phase advance surrounding a phase delay peak. This pattern is important in generating a stable synchrony within the ICC network and is related to the state space of the ICC; in particular, the phase delay peak corresponds to the unstable equilibrium point that threads the ICC's limit cycle. Interstitial cells of Cajal (ICCs) generate electrical oscillations in the gut. Synchronization of the ICC population is required for generation of coherent electrical waves ('slow waves') that cause muscular contraction and thereby move gut content. The phase response curve (PRC) is an experimental measure of the dynamical rules governing a population of oscillators that determine their synchrony and gives an experimental window onto the state space of the oscillator, its dynamical landscape. We measured the PRC of slow wave contractions in the mouse small intestine by the novel combination of diameter mapping and single pulse electrical field stimulation. Phase change (τ) was measured as a function of old phase (ϕ) and distance from the stimulation electrode (d). Plots of τ(ϕ, d) showed an arrowhead-shaped region of phase advance enclosing at its base a phase delay peak. The phase change mirrored the perturbed pattern of contraction waves in response to a pulse. The (ϕ, d) plane is the surface of a displacement tube extending from the limit cycle through state space. To visualize the state space vector field on this tube, latent phase (ϕlat ) was calculated from τ. At the transition from advance to delay, isochrons made boomerang turns before tightening and winding around the phase delay peak corresponding to the unstable equilibrium point that threads the limit cycle. This isochron foliation had previously been observed in oscillator models such as the Fitzhugh-Nagumo but has not been demonstrated experimentally. The spatial extension of the PRC afforded by diameter mapping allows a better understanding of the dynamical properties of ICCs and how they synchronize as a population.

A framework for simulating gastric electrical propagation in confocal microscopy derived geometries.

Interstitial Cells of Cajal (ICC) initiate and actively propagate electrical events in the gastrointestinal tract known as slow-waves. The slow-waves coordinate the contraction of the gastrointestinal tract necessary for breakdown and mixing of ingested food. Degradation of the ICC numbers has been linked to several gastrointestinal motility disorders. However, limitations in imaging techniques and techniques for the quantification of ICC network structure have hindered our understanding of these disorders. We evaluated different machine learning techniques to segment ICC networks imaged using confocal microscopy. The accuracy the segmented networks were then quantified and compared using numerical metrics. Structurally realistic finite element meshes were constructed and used to simulate the propagation of electrical activation over the tissue blocks. The presented framework provides a system to quantify the structure and function of an ICC tissue sample. These methods are also applicable to other biological tissues and networks.

Effects of Synbiotic2000™ Forte on the Intestinal Motility and Interstitial Cells of Cajal in TBI Mouse Model.

The main objective of this study was to investigate the effects of Synbiotic2000™ Forte on the intestinal motility and interstitial cells of Cajal (ICC) in traumatic brain injury (TBI) mouse model. Kunming mice were randomly divided into sham operation group (S group), enteral nutrition group with TBI (E group), and Synbiotic2000™ Forte group with TBI (P group). The contractile activity of the intestinal smooth muscle, densities and ultrastructure of the ICC, kit protein concentration, weight, and defecation of mice were monitored and analyzed. TBI markedly suppressed contractile activity of the intestinal smooth muscle (P<0.01), which led to a reduction of defecation (P<0.01) and weight (P<0.01). However, application of Synbiotic2000™ Forte significantly improved contractile activity of the small intestine (P<0.01), which may be related to protective effects to the interstitial cells of Cajal, smooth muscle cells, and enteric neurons. TBI impaired ICC networks and densities (P<0.01), events that were protected by the application of Synbiotic2000™ Forte. Synbiotic2000™ Forte may attenuate TBI-mediated inhibition of the kit protein pathway. Synbiotic2000™ Forte may improve intestinal motility and protect the ICC in the TBI mouse. These findings provide a novel support for the application of Synbiotic2000™ Forte in intestinal motility disturbance after TBI.