Ultrastructural injury to interstitial cells of Cajal and communication with mast cells in Crohn's disease

Ultrastructural changes in chronic inflammatory enteropathies-a comparison between dogs and humans

Chronic inflammatory enteropathies (CIEs) are an important group of diseases in dogs and involve complex pathogenetic aspects. Endoscopy and histopathology are vital for documenting the disease but are less useful for subclassifying CIEs and predicting the response to treatment. However, healing of the mucosal disease process (deep remission) and ultrastructural evaluation of the mucosa have received little attention in canine CIE. Given that canine CIE shares many similarities with inflammatory bowel diseases (IBDs) in human patients-and presents a good spontaneous disease model for human IBD-this perspective article evaluates the literature on ultrastructural lesions in canine CIE and human IBD and offers future directions for the study of ultrastructural mucosal lesions in canine CIE. Such lesions might have a higher sensitivity of detection than structural changes revealed upon light microscopy and may even precede or remain after the resolution of the clinical signs and histologic lesions.

The critical role of muscularis macrophages in modulating the enteric nervous system function and gastrointestinal motility

Macrophages are the originators of inflammatory compounds, phagocytic purifiers in their local environment, and wound healing protectors in oxidative environments. They are molded by the tissue milieu they inhabit, with gastrointestinal (GI) muscularis macrophages (MMs) being a prime example. MMs are located in the muscular layer of the GI tract and contribute to muscle repair and maintenance of GI motility. MMs are often in close proximity to the enteric nervous system, specifically near the enteric neurons and interstitial cells of Cajal (ICCs). Consequently, the anti-inflammatory function of MMs corresponds to the development and maintenance of neural networks in the GI tract. The capacity of MMs to shift from anti-inflammatory to proinflammatory states may contribute to the inflammatory aspects of various GI diseases and disorders such as diabetic gastroparesis or postoperative ileus, functional disorders such as irritable bowel syndrome, and organic diseases such as inflammatory bowel disease. We reviewed the current knowledge of MMs and their influence on neighboring cells due to their important role in the GI tract.

Role of Mitochondria in Inflammatory Bowel Diseases: A Systematic Review

Mitochondria are key cellular organelles whose main function is maintaining cell bioenergetics by producing ATP through oxidative phosphorylation. However, mitochondria are involved in a much higher number of cellular processes. Mitochondria are the home of key metabolic pathways like the tricarboxylic acid cycle and β-oxidation of fatty acids, as well as biosynthetic pathways of key products like nucleotides and amino acids, the control of the redox balance of the cell and detoxifying the cell from H2S and NH3. This plethora of critical functions within the cell is the reason mitochondrial function is involved in several complex disorders (apart from pure mitochondrial disorders), among them inflammatory bowel diseases (IBD). IBD are a group of chronic, inflammatory disorders of the gut, mainly composed of ulcerative colitis and Crohn's disease. In this review, we present the current knowledge regarding the impact of mitochondrial dysfunction in the context of IBD. The role of mitochondria in both intestinal mucosa and immune cell populations are discussed, as well as the role of mitochondrial function in mechanisms like mucosal repair, the microbiota- and brain-gut axes and the development of colitis-associated colorectal cancer.

Crohn’s disease: Why the ileum?

Crohn’s disease (CD) is an inflammatory bowel disease characterized by immune-mediated flares affecting any region of the intestine alternating with remission periods. In CD, the ileum is frequently affected and about one third of patients presents with a pure ileal type. Moreover, the ileal type of CD presents epidemiological specificities like a younger age at onset and often a strong link with smoking and genetic susceptibility genes. Most of these genes are associated with Paneth cell dysfunction, a cell type found in the intestinal crypts of the ileum. Besides, a Western-type diet is associated in epidemiological studies with CD onset and increasing evidence shows that diet can modulate the composition of bile acids and gut microbiota, which in turn modulates the susceptibility of the ileum to inflammation. Thus, the interplay between environmental factors and the histological and anatomical features of the ileum is thought to explain the specific transcriptome profile observed in CD ileitis. Indeed, both immune response and cellular healing processes harbour differences between ileal and non-ileal CD. Taken together, these findings advocate for a dedicated therapeutic approach to managing ileal CD. Currently, interventional pharmacological studies have failed to clearly demonstrate distinct response profiles according to disease site. However, the high rate of stricturing disease in ileal CD requires the identification of new therapeutic targets to significantly change the natural history of this debilitating disease.

Role of CD34 in inflammatory bowel disease

Inflammatory bowel disease (IBD) is caused by a variety of pathogenic factors, including chronic recurrent inflammation of the ileum, rectum, and colon. Immune cells and adhesion molecules play an important role in the course of the disease, which is actually an autoimmune disease. During IBD, CD34 is involved in mediating the migration of a variety of immune cells (neutrophils, eosinophils, and mast cells) to the inflammatory site, and its interaction with various adhesion molecules is involved in the occurrence and development of IBD. Although the function of CD34 as a partial cell marker is well known, little is known on its role in IBD. Therefore, this article describes the structure and biological function of CD34, as well as on its potential mechanism in the development of IBD.

Telocytes in Cutaneous Biology: A Reappraisal

The telocytes (TCs) are novel interstitial cells that have been overlooked for a long time due to their histologic similarity to other stromal cells. TCs can be separated from the stromal cells based on their distinct immunohistochemical, ultrastructural, and molecular features. Functionally, TCs are involved in the tissue renewal, mechanical support, and immune modulation. These cells are also involved in the signal transduction either through their direct interactions with the neighboring cells or through the paracrine signaling via extracellular vesicles. TCs are damaged in several inflammatory and fibrotic conditions such as ulcerative colitis, Crohn's disease, hepatic fibrosis, psoriasis, and systemic sclerosis. The transplantation of TCs in the damaged tissue can promote tissue regeneration. Therefore, enhancing tissue TCs either by their transplantation or by promoting their survival and growth using novel medications represents novel therapeutic strategy in the future. In this review, we addressed several aspects of TCs including their origin, distribution, morphologic features, and functions. We also discussed their involvement of the cutaneous TCs in the development various pathologic conditions.

Telocytes in Cutaneous Biology: A Reappraisal

The telocytes (TCs) are novel interstitial cells that have been overlooked for a long time due to their histologic similarity to other stromal cells. TCs can be separated from the stromal cells based on their distinct immunohistochemical, ultrastructural, and molecular features. Functionally, TCs are involved in the tissue renewal, mechanical support, and immune modulation. These cells are also involved in the signal transduction either through their direct interactions with the neighboring cells or through the paracrine signaling via extracellular vesicles. TCs are damaged in several inflammatory and fibrotic conditions such as ulcerative colitis, Crohn's disease, hepatic fibrosis, psoriasis, and systemic sclerosis. The transplantation of TCs in the damaged tissue can promote tissue regeneration. Therefore, enhancing tissue TCs either by their transplantation or by promoting their survival and growth using novel medications represents novel therapeutic strategy in the future. In this review, we addressed several aspects of TCs including their origin, distribution, morphologic features, and functions. We also discussed their involvement of the cutaneous TCs in the development various pathologic conditions.

Distributions of Platelet-Derived Growth Factor Receptor-α Positive Cells and Interstitial Cells of Cajal in the Colon of Rats with Diabetes Mellitus Type 2

Background and Objectives: Diabetic gastroenteropathy (DG) is a common complication of diabetes mellitus type 2. Interstitial cells are non-neural cells of mesenchymal origin inserted between nerve elements and smooth muscle cells, necessary for normal function and peristaltic contractions in the gastrointestinal (GI) tract. There are at least two types of interstitial cells within the GI muscle layer-interstitial cells of Cajal (ICC) and interstitial platelet-derived growth factor receptor α-positive cells (IPC). The mechanism of diabetic gastroenteropathy is unclear, and interstitial cells disorders caused by metabolic changes in diabetes mellitus (DM) could explain the symptoms of DG (slow intestinal transit, constipation, fecal incontinence). The aim of this study was to identify PDGFRα and c-kit immunoreactive cells in the colon of rats with streptozotocin-nicotinamide-induced diabetes mellitus type 2, as well as to determine their distribution in relation to smooth muscle cells and enteric nerve structures. Materials and Methods: Male Wistar rats were used, and diabetes type 2 was induced by an intraperitoneal injection of streptozotocin, immediately after intraperitoneal application of nicotinamide. The colon specimens were exposed to PDGFRα and anti-c-kit antibodies to investigate interstitial cells; enteric neurons and smooth muscle cells were immunohistochemically labeled with NF-M and desmin antibodies. Results: Significant loss of the intramuscular ICC, myenteric ICC, and loss of their connection in intramuscular linear arrays and around the ganglion of the myenteric plexus were observed with no changes in nerve fiber distribution in the colon of rats with diabetes mellitus type 2. IPC were rarely present within the colon muscle layer with densely distributed PDGFRα+ cells in the colon mucosa and submucosa of both experimental groups. In summary, a decrease in intramuscular ICC, discontinuities and breakdown of contacts between myenteric ICC without changes in IPC and nerve fibers distribution were observed in the colon of streptozotocin/nicotinamide-induced diabetes type 2 rats.

Role of Macrophages and Mast Cells as Key Players in the Maintenance of Gastrointestinal Smooth Muscle Homeostasis and Disease

The gut contains the largest macrophage pool in the body, with populations of macrophages residing in the mucosa and muscularis propria of the gastrointestinal (GI) tract. Muscularis macrophages (MMs), which are located within the muscularis propria, interact with cells essential for GI function, such as interstitial cells of Cajal, enteric neurons, smooth muscle cells, enteric glia, and fibroblast-like cells, suggesting that these immune cells contribute to several aspects of GI function. This review focuses on the latest insights on the factors contributing to MM heterogeneity and the functional interaction of MMs with other cell types essential for GI function. This review integrates the latest findings on macrophages in other organs with increasing knowledge of MMs to better understand their role in a healthy and diseased gut. We describe the factors that contribute to (muscularis macrophage) MM heterogeneity, and the nature of MM interactions with cells regulating GI function. Finally, we also describe the increasing evidence suggesting a critical role of another immune cell type, the mast cell, in normal and diseased GI physiology.

Telocytes in Fibrosis Diseases: From Current Findings to Future Clinical Perspectives

Telocytes (TCs), a distinct type of interstitial (stromal) cells, have been discovered in many organs of human and mammal animals. TCs, which have unique morphological characteristics and abundant paracrine substance, construct a three-dimensional (3D) interstitial network within the stromal compartment by homocellular and heterocellular communications which are important for tissue homeostasis and normal development. Fibrosis-related diseases remain a common but challenging problem in the field of medicine with unclear pathogenesis and limited therapeutic options. Recently, increasing evidences suggest that where TCs are morphologically or numerically destructed, many diseases continuously develop, finally lead to irreversible interstitial fibrosis. It is not difficult to find that TCs are associated with chronic inflammation and fibrosis. This review mainly discusses relationship between TCs and the occurrence of fibrosis in various diseases. We analyzed in detail the potential roles and speculated mechanisms of TCs in onset and progression of systemic fibrosis diseases, as well as providing the most up-to-date research on the current therapeutic roles of TCs and involved related pathways. Only through continuous research and exploration in the future can we uncover its magic veil and provide strategies for treatment of fibrosis-related disease.

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

Our understanding of human colonic motility, and autonomic reflexes that generate motor patterns, has increased markedly through high-resolution manometry. Details of the motor patterns are emerging related to frequency and propagation characteristics that allow linkage to interstitial cells of Cajal (ICC) networks. In studies on colonic motor dysfunction requiring surgery, ICC are almost always abnormal or significantly reduced. However, there are still gaps in our knowledge about the role of ICC in the control of colonic motility and there is little understanding of a mechanistic link between ICC abnormalities and colonic motor dysfunction. This review will outline the various ICC networks in the human colon and their proven and likely associations with the enteric and extrinsic autonomic nervous systems. Based on our extensive knowledge of the role of ICC in the control of gastrointestinal motility of animal models and the human stomach and small intestine, we propose how ICC networks are underlying the motor patterns of the human colon. The role of ICC will be reviewed in the autonomic neural reflexes that evoke essential motor patterns for transit and defecation. Mechanisms underlying ICC injury, maintenance, and repair will be discussed. Hypotheses are formulated as to how ICC dysfunction can lead to motor abnormalities in slow transit constipation, chronic idiopathic pseudo-obstruction, Hirschsprung's disease, fecal incontinence, diverticular disease, and inflammatory conditions. Recent studies on ICC repair after injury hold promise for future therapies.

Ultrastructural changes of the human enteric nervous system and interstitial cells of Cajal in diverticular disease

BACKGROUND

In spite of numerous advances in understanding diverticular disease, its pathogenesis remains one of the main problems to be solved. We aimed to investigate the ultrastructural changes of the enteric nervous system in unaffected individuals, in asymptomatic patients with diverticulosis and in patients with diverticular disease.

METHODS

Transmission electron microscopy was used to analyse samples of the myenteric, outer submucosal and inner submucosal plexuses from patients without diverticula (n=9), asymptomatic patients with diverticulosis (n=7) and in patients with complicated diverticular disease (n=9). We described the structure of ganglia, interstitial cells of Cajal and enteric nerves, as well as their relationship with each other. The distribution and size of nerve processes were analysed quantitatively.

RESULTS

In complicated diverticular disease, neurons exhibited larger lipofuscin-like inclusions, their membranous organelles had larger cisterns and the nucleus showed deeper indentations. Nerve remodeling occurred in every plexus, characterised by an increased percentage of swollen and fine neurites. Interstitial cells of Cajal had looser contacts with the surrounding cells and showed cytoplasmic depletion and proliferation of the rough endoplasmic reticulum. In asymptomatic patients with diverticulosis, alterations of enteric nerves and ICC were less pronounced.

CONCLUSIONS

In conclusion, the present findings suggest that most ultrastructural changes of the enteric nervous system occur in complicated diverticular disease. The changes are compatible with damage to the enteric nervous system and reactive remodeling of enteric ganglia, nerves and interstitial cells of Cajal. Disrupted architecture of enteric plexuses might explain clinical and pathophysiological changes associated with diverticular disease.

Recently Discovered Interstitial Cell Population of Telocytes: Distinguishing Facts from Fiction Regarding Their Role in the Pathogenesis of Diverse Diseases Called "Telocytopathies"

In recent years, the interstitial cells telocytes, formerly known as interstitial Cajal-like cells, have been described in almost all organs of the human body. Although telocytes were previously thought to be localized predominantly in the organs of the digestive system, as of 2018 they have also been described in the lymphoid tissue, skin, respiratory system, urinary system, meninges and the organs of the male and female genital tracts. Since the time of eminent German pathologist Rudolf Virchow, we have known that many pathological processes originate directly from cellular changes. Even though telocytes are not widely accepted by all scientists as an individual and morphologically and functionally distinct cell population, several articles regarding telocytes have already been published in such prestigious journals as Nature and Annals of the New York Academy of Sciences. The telocyte diversity extends beyond their morphology and functions, as they have a potential role in the etiopathogenesis of different diseases. The most commonly described telocyte-associated diseases (which may be best termed "telocytopathies" in the future) are summarized in this critical review. It is difficult to imagine that a single cell population could be involved in the pathogenesis of such a wide spectrum of pathological conditions as extragastrointestinal stromal tumors ("telocytomas"), liver fibrosis, preeclampsia during pregnancy, tubal infertility, heart failure and psoriasis. In any case, future functional studies of telocytes in vivo will help to understand the mechanism by which telocytes contribute to tissue homeostasis in health and disease.

Process Design of the Antioxidant Shuidouchi and Its Effect on Preventing Dextran Sulfate Sodium (DSS)-Induced Colitis in Mice via Antioxidant Activity

Shuidouchi is a traditionally fermented soybean product in China. Shuidouchi production requires a variety of processes; however, the production process has not been standardized. It can be developed into high-quality products with enhanced health effects by improving the design of its fermentation process and increasing the content of its active ingredients. In this study, a single-factor experiment was conducted that established different process conditions to determine the fermentation conditions that achieve the highest content of active ingredients and the best in vitro antioxidant effect. The effect of Shuidouchi on the prevention of dextran sulfate sodium-induced colitis in mice was also observed. The obtained results indicated that the optimal process conditions involved soaking for 12 h, placement in a glass container, and fermentation at 35 °C for 48 h. Shuidouchi that was fermented under such conditions had the highest level of soybean isoflavones and exerted greater antioxidant effects than if fermented under other conditions. The Shuidouchi extract (soaking twice the quantity of water for 12 h, placing in a glass container, and fermenting at 35 °C for 48 h) obtained by using the optimal fermentation process can prevent the shortening of the colon and increase the weight-to-length ratio of the colon that is caused by colitis. Shuidouchi extraction not only effectively reduces the disease activity index and the levels of serum endothelin (ET), substance P (SP), and interleukin-10 (IL-10), it also increases the levels of somatostatin (SS), vasoactive intestinal peptide (VIP), and interleukin-2 (IL-2) of mice with colitis. In addition, Shuidouchi extraction increased the levels of glutathione (GSH) and superoxide dismutase (SOD) in colitis mice; in contrast, Shuidouchi decreased the levels of myeloperoxidase (MPO) and malondialdehyde (MDA) in the colon of mice with colitis. Further detection of mRNA in colon tissues showed that Shuidouchi extraction can upregulate the expression of neuronal nitric oxide synthase (nNOS), endothelial nitric oxide synthase (eNOS), c-Kit, and the stem cell factor (SCF). Furthermore, it can downregulate the expression of inducible nitric oxide synthase (iNOS), interleukin-8 (IL-8), and C-X-C chemokine receptor type 2 (CXCR2) in the colon of mice with colitis. Further experimental results showed that Shuidouchi could reduce the protein expression of interleukin 6 (IL-6), IL-12, and tumor necrosis factor-α (TNF-α) in colitic mice. Therefore, the improved processing of Shuidouchi inhibits colitis, which is directly related to the high content of soybean isoflavones.

Clostridium butyricum regulates visceral hypersensitivity of irritable bowel syndrome by inhibiting colonic mucous low grade inflammation through its action on NLRP6

Visceral hypersensitivity induced by stress is quite common in irritable bowel syndrome (IBS) patients. Probiotics play an important role in reducing visceral hypersensitivity in IBS patients. However, the mechanism has not been clearly elucidated. In this study, we investigated the role of nod-like receptor pyrin domain-containing protein 6 (NLRP6) in Clostridium butyricum-regulated IBS induced by stress. Our results showed that NLRP6 was down-regulated in IBS group colon tissues. In addition, IL-18, IL-1β, myeloperoxidase (MPO), d-lactic acid (D-LA), and CD172a were up-regulated in the IBS group of colonic mucous. IL-18 and IL-1β were also increased after the NLRP6 gene was silenced. Pathological score suggested low inflammation of colonic mucous rather than terminal ileum. Water-avoidance stress (WAS) showed visceral hypersensitivity to colonic distension. However, treatment with Clostridium butyricum reversed these results, exerting a beneficial effect. In conclusion, Clostridium butyricum may exert a beneficial action on visceral hypersensitivity of IBS by inhibiting low grade inflammation of colonic mucous through its action on NLRP6.

Identification and Distribution of the Interstitial Cells of Cajal in the Abomasum of Goats

The interstitial cells of Cajal (ICCs) are regarded as pacemakers and are involved in neurotransmission in the gastrointestinal tract (GIT) of animals. However, limited information is available about the existence of ICCs within the GIT of ruminants. In this study, we investigated the ultrastructural characteristics and distribution of ICCs in goat abomasum using transmission electron microscopy and c-kit immunohistochemistry. Two different kinds of c-kit immunoreactive cells were observed in the abomasum. The first was identified as ICCs, which appeared to be multipolar or bipolar in shape, with some processes. These c-kit immunoreactive cells were deposited in the submucosal layer, myenteric plexus between the circular and longitudinal muscle layers, and within the longitudinal and circular muscle layers of the abomasum. The second type of cell was round in shape and was identified as mast cells, which were located in the submucosal layer as well as in the lamina propria. Ultrastructurally, ICCs were also observed as stellate or spindle-shaped cells, which were consistent in shape with our c-kit immunoreactive cells. In the cytoplasm of ICCs, numerous mitochondria, rough endoplasmic reticulum, and caveolae were detected. ICCs were located in the myenteric plexus between the longitudinal and circular muscle layers (ICC-MY), with the longitudinal and circular muscle layer was replaced as “intramuscular layers” (ICC-IM), and in the submucosal layer (ICC-SM). In addition, we found ICCs surrounding nerve fibers and smooth muscle cells, where they formed heterocellular junctions in the form of close membrane associations or gap junctions and homocellular junctions among the processes of the ICCs. In the current study, we provide the first complete characterization of ICCs within the goat abomasum and propose that ICCs might have a key role in producing contractions in the ruminant stomach for proper absorption of nutrients.

Telocytes in Chronic Inflammatory and Fibrotic Diseases

Telocytes are a peculiar stromal (interstitial) cell type implicated in tissue homeostasis and development, as well as in the pathophysiology of several disorders. Severe damage and reduction of telocytes have been reported during fibrotic remodeling of multiple organs in various diseases, including scleroderma, Crohn's disease, ulcerative colitis, and liver fibrosis, as well as in chronic inflammatory lesions like those of primary Sjögren's syndrome and psoriasis. Owing to their close relationship with stem cells, telocytes are also supposed to contribute to tissue repair/regeneration. Indeed, telocytes are universally considered as "connecting cells" mostly oriented to intercellular signaling. On the basis of recent promising experimental findings, in the near future, telocyte transplantation might represent a novel therapeutic opportunity to control the evolution of chronic inflammatory and fibrotic diseases. Notably, there is evidence to support that telocytes could help in preventing abnormal activation of immune cells and fibroblasts, as well as in attenuating the altered matrix organization during the fibrotic process. By targeting telocytes alone or in tandem with stem cells, we might be able to promote regeneration and prevent the evolution to irreversible tissue injury. Besides exogenous transplantation, exploring pharmacological or non-pharmacological methods to enhance the growth and/or survival of telocytes could be an additional therapeutic strategy for many disorders.

The involvement of mast cells in the irinotecan-induced enteric neurons loss and reactive gliosis

Background

The irinotecan (CPT-11) causes intestinal mucositis and diarrhea that may be related to changes in the enteric nervous system (ENS). In inflammatory condition, mast cells release a variety of pro-inflammatory mediators that can interact with the ENS cells. It has not been explored whether CPT-11 is able to alter the enteric glial and neuronal cell, and the role of mast cells in this effect. Therefore, this study was conducted to investigate the effect of CPT-11 on the enteric glial and neuronal cells, as well as to study the role of mast cells in the CPT-11-induced intestinal mucositis.

Methods

Intestinal mucositis was induced in Swiss mice by the injection of CPT-11 (60 mg/kg, i.p.) once a day for 4 days following by euthanasia on the fifth day. To investigate the role of mast cells, the mice were pretreated with compound 48/80 for 4 days (first day, 0.6 mg/kg; second day, 1.0 mg/kg; third day, 1.2 mg/kg; fourth day, 2.4 mg/kg) to induce mast cell degranulation before the CPT-11 treatment.

Results

Here, we show that CPT-11 increased glial fibrillary acidic protein (GFAP) and S100β gene and S100β protein expressions and decreased HuC/D protein expression in the small intestine segments. Concomitantly, CPT-11 enhanced tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) levels and inducible nitric oxide synthase (iNOS) gene expression, associated with an increase in the total number macrophages (positive cells for ionized calcium-binding adapter molecule, Iba-1) and degranulated mast cells in the small intestine segments and caused significant weight loss. The pretreatment with compound 48/80, an inductor of mast cells degranulation, significantly prevented these CPT-11-induced effects.

Conclusions

Our data suggests the participation of mast cells on the CPT-11-induced intestinal mucositis, macrophages activation, enteric reactive gliosis, and neuron loss.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0854-1) contains supplementary material, which is available to authorized users.

Calcium Signaling in Interstitial Cells: Focus on Telocytes

In this review, we describe the current knowledge on calcium signaling pathways in interstitial cells with a special focus on interstitial cells of Cajal (ICCs), interstitial Cajal-like cells (ICLCs), and telocytes. In detail, we present the generation of Ca²⁺ oscillations, the inositol triphosphate (IP₃)/Ca²⁺ signaling pathway and modulation exerted by cytokines and vasoactive agents on calcium signaling in interstitial cells. We discuss the physiology and alterations of calcium signaling in interstitial cells, and in particular in telocytes. We describe the physiological contribution of calcium signaling in interstitial cells to the pacemaking activity (e.g., intestinal, urinary, uterine or vascular pacemaking activity) and to the reproductive function. We also present the pathological contribution of calcium signaling in interstitial cells to the aortic valve calcification or intestinal inflammation. Moreover, we summarize the current knowledge of the role played by calcium signaling in telocytes in the uterine, cardiac and urinary physiology, and also in various pathologies, including immune response, uterine and cardiac pathologies.

Reactive oxygen species and antioxidant defense in human gastrointestinal diseases

Crohn's disease and ulcerative colitis, known together as inflammatory bowel diseases (IBDs), and celiac disease are the most common disorders affecting not only adults but also children. Both IBDs and celiac disease are associated with oxidative stress, which may play a significant role in their etiologies. Reactive oxygen species (ROS) such as superoxide radicals (O2•-), hydroxyl radicals (•OH), hydrogen peroxide (H2O2), and singlet oxygen (1O2) are responsible for cell death via oxidation of DNA, proteins, lipids, and almost any other cellular constituent. To protect biological systems from free radical toxicity, several cellular antioxidant defense mechanisms exist to regulate the production of ROS, including enzymatic and nonenzymatic pathways. Superoxide dismutase catalyzes the dismutation of O2•- to H2O2 and oxygen. The glutathione redox cycle involves two enzymes: glutathione peroxidase, which uses glutathione to reduce organic peroxides and H2O2; and glutathione reductase, which reduces the oxidized form of glutathione with concomitant oxidation of nicotinamide adenine dinucleotide phosphate. In addition to this cycle, GSH can react directly with free radicals. Studies into the effects of free radicals and antioxidant status in patients with IBDs and celiac disease are scarce, especially in pediatric patients. It is therefore very necessary to conduct additional research studies to confirm previous data about ROS status and antioxidant activities in patients with IBDs and celiac disease, especially in children.

Neuroimmunomodulation in the Gut: Focus on Inflammatory Bowel Disease

Intestinal immunity is finely regulated by several concomitant and overlapping mechanisms, in order to efficiently sense external stimuli and mount an adequate response of either tolerance or defense. In this context, a complex interplay between immune and nonimmune cells is responsible for the maintenance of normal homeostasis. However, in certain conditions, the disruption of such an intricate network may result in intestinal inflammation, including inflammatory bowel disease (IBD). IBD is believed to result from a combination of genetic and environmental factors acting in concert with an inappropriate immune response, which in turn interacts with nonimmune cells, including nervous system components. Currently, evidence shows that the interaction between the immune and the nervous system is bidirectional and plays a critical role in the regulation of intestinal inflammation. Recently, the maintenance of intestinal homeostasis has been shown to be under the reciprocal control of the microbiota by immune mechanisms, whereas intestinal microorganisms can modulate mucosal immunity. Therefore, in addition to presenting the mechanisms underlying the interaction between immune and nervous systems in the gut, here we discuss the role of the microbiota also in the regulation of neuroimmune crosstalk involved in intestinal homeostasis and inflammation, with potential implications to IBD pathogenesis.

Telocyte implications in human pathology: An overview

Telocytes are a recently described interstitial cell population widely distributed in the stromal compartment of many organs in vertebrates, including humans. Owing to their close spatial relationship with multiple cell types, telocytes are universally considered as 'connecting cells' mostly committed to intercellular signaling by converting the interstitium into an integrated system that drives organ development and contributes to the maintenance of local tissue homeostasis. Increasing evidence indicates that telocytes may cooperate with tissue-resident stem cells to foster organ repair and regeneration, and that telocyte damage and dysfunction may occur in several disorders. The goal of this review is to provide an overview of the most recent findings concerning the implication of telocytes in a variety of pathologic conditions in humans, including heart disease, chronic inflammation and multiorgan fibrosis. Based on recent promising experimental data, there is realistic hope that by targeting telocytes alone or in tandem with stem cells, we might be able to promote organ regeneration and/or prevent irreversible end-stage organ damage in different pathologies.

Is Interstitial Cells of Cajal‒opathy Present in Gastroparesis?

Gastroparesis (GP), defined as delayed gastric emptying in the absence of any mechanical obstruction, is a challenging clinical condition, mainly because of limited treatment options. Studies in animal models of delayed gastric emptying as well as patients with gastroparesis revealed depletion or ultrastructural changes of interstitial cells of Cajal (ICC) in the gastric tissue, recently termed ICC-opathy. ICC are the pacemakers of the gastrointestinal tract and are involved in the transmission of the neuronal signaling to the smooth muscles. Therefore, lack of ICC could be one explanation of delayed gastric emptying in gastroparetic patients. How frequently ICC changes are observed in gastroparesis is not yet clear. In this review, the data on gastric ICC counts and morphology in animal models and patients with gastroparesis are discussed.

Discrepancies between c-Kit positive and Ano1 positive ICC-SMP in the W/Wv and wild-type mouse colon; relationships with motor patterns and calcium transients

BACKGROUND

Interstitial cells of Cajal associated with the submuscular plexus (ICC-SMP) generate omnipresent slow-wave activity in the colon and are associated with prominent motor patterns. Our aim was to investigate colon motor dysfunction in W/W(v) mice in which the ICC are reportedly reduced.

METHODS

Whole organ colon motility was studied using spatio-temporal mapping; immunohistochemical staining was carried out for c-Kit and Ano1; calcium imaging was applied to ICC-SMP.

KEY RESULTS

Discrepancies between Ano1 and c-Kit staining were found in both wild-type and W/W(v) colon. ICC-SMP were reduced to ~50% in the W/W(v) mouse colon according to c-Kit immunohistochemistry, but Ano1 staining indicated a normal network of ICC-SMP. The latter was consistent with rhythmic calcium transients occurring at the submucosal border of the colon in W/W(v) mice, similar to the rhythmic transients in wild-type ICC-SMP. Furthermore, the motor pattern associated with ICC-SMP pacemaking, the so-called 'ripples' were normal in the W/W(v) colon.

CONCLUSIONS & INFERENCES

c-Kit is not a reliable marker for quantifying ICC-SMP in the mouse colon. Ano1 staining revealed a normal network of ICC-SMP consistent with the presence of a normal 'ripples' motor pattern. We detected a class of Ano1 positive c-Kit negative cells that do not depend on Kit expression for maintenance, a feature shared with ICC progenitors.

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.

Neuroanatomy of lower gastrointestinal pain disorders

Chronic abdominal pain accompanying intestinal inflammation emerges from the hyperresponsiveness of neuronal, immune and endocrine signaling pathways within the intestines, the peripheral and the central nervous system. In this article we review how the sensory nerve information from the healthy and the hypersensitive bowel is encoded and conveyed to the brain. The gut milieu is continuously monitored by intrinsic enteric afferents, and an extrinsic nervous network comprising vagal, pelvic and splanchnic afferents. The extrinsic afferents convey gut stimuli to second order neurons within the superficial spinal cord layers. These neurons cross the white commissure and ascend in the anterolateral quadrant and in the ipsilateral dorsal column of the dorsal horn to higher brain centers, mostly subserving regulatory functions. Within the supraspinal regions and the brainstem, pathways descend to modulate the sensory input. Because of this multiple level control, only a small proportion of gut signals actually reaches the level of consciousness to induce sensation or pain. In inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) patients, however, long-term neuroplastic changes have occurred in the brain-gut axis which results in chronic abdominal pain. This sensitization may be driven on the one hand by peripheral mechanisms within the intestinal wall which encompasses an interplay between immunocytes, enterochromaffin cells, resident macrophages, neurons and smooth muscles. On the other hand, neuronal synaptic changes along with increased neurotransmitter release in the spinal cord and brain leads to a state of central wind-up. Also life factors such as but not limited to inflammation and stress contribute to hypersensitivity. All together, the degree to which each of these mechanisms contribute to hypersensitivity in IBD and IBS might be disease- and even patient-dependent. Mapping of sensitization throughout animal and human studies may significantly improve our understanding of sensitization in IBD and IBS. On the long run, this knowledge can be put forward in potential therapeutic targets for abdominal pain in these conditions.

Telocytes in Crohn's disease

Crohn’s disease (CD) is a relapsing chronic inflammatory disorder that may involve all the gastrointestinal tract with a prevalence of terminal ileum. Intestinal lesions have a characteristic discontinuous and segmental distribution and may affect all layers of the gut wall. Telocytes (TC), a peculiar type of stromal cells, have been recently identified in a variety of tissues and organs, including gastrointestinal tract of humans and mammals. Several roles have been proposed for TC, including mechanical support, spatial relationships with different cell types, intercellular signalling and modulation of intestinal motility. The aim of our study was to investigate the presence and distribution of TC in disease-affected and -unaffected ileal specimens from CD patients compared with controls. TC were identified by CD34/PDGFRα immunohistochemistry. In affected CD specimens TC disappeared, particularly where fibrosis and architectural derangement of the intestinal wall were observed. In the thickened muscularis mucosae and submucosa, few TC entrapped in the fibrotic extracellular matrix were found. A discontinuous network of TC was present around smooth muscle bundles, ganglia and enteric strands in the altered muscularis propria. At the myenteric plexus, the loss of TC network was paralleled by the loss of interstitial cells of Cajal network. In the unaffected CD specimens, TC were preserved in their distribution. Our results suggest that in CD the loss of TC might have important pathophysiological implications contributing to the architectural derangement of the intestinal wall and gut dysmotility. Further functional studies are necessary to better clarify the role of TC loss in CD pathophysiology.

Altered distribution of interstitial cells and innervation in the rat urinary bladder following spinal cord injury

Changes in the distribution of interstitial cells (IC) are reportedly associated with dysfunctional bladder. This study investigated whether spinal cord injury (SCI) resulted in changes to IC subpopulations (vimentin-positive with the ultrastructural profile of IC), smooth muscle and nerves within the bladder wall and correlated cellular remodelling with functional properties. Bladders from SCI (T8/9 transection) and sham-operated rats 5 weeks post-injury were used for ex vivo pressure–volume experiments or processed for morphological analysis with transmission electron microscopy (TEM) and light/confocal microscopy. Pressure-volume relationships revealed low-pressure, hypercompliance in SCI bladders indicative of decompensation. Extensive networks of vimentin-positive IC were typical in sham lamina propria and detrusor but were markedly reduced post-SCI; semi-quantitative analysis showed significant reduction. Nerves labelled with anti-neurofilament and anti-vAChT were notably decreased post-SCI. TEM revealed lamina propria IC and detrusor IC which formed close synaptic-like contacts with vesicle-containing nerve varicosities in shams. Lamina propria and detrusor IC were ultrastructurally damaged post-SCI with retracted/lost cell processes and were adjacent to areas of cellular debris and neuronal degradation. Smooth muscle hypertrophy was common to SCI tissues. In conclusion, IC populations in bladder wall were decreased 5 weeks post-SCI, accompanied with reduced innervation, smooth muscle hypertrophy and increased compliance. These novel findings indicate that bladder wall remodelling post-SCI affects the integrity of interactions between smooth muscle, nerves and IC, with compromised IC populations. Correlation between IC reduction and a hypercompliant phenotype suggests that disruption to bladder IC contribute to pathophysiological processes underpinning the dysfunctional SCI bladder.

Interstitial Cells of Cajal: Pathology, injury and repair

Interstitial cells of cajal (ICC) are specialised cells located within the musculature of the gastrointestinal tract (GIT). Although they form only 5% of the cells in the musculature of the GIT, they play a critical role in regulating smooth muscle function and GIT motility in coordination with the enteric nervous system. C-kit is a transmembrane glycoprotein that plays a critical role in ICC development and maturation. Physiological conditions such as ageing, as well as pathological conditions that have different disease processes, negatively affect ICC networks and function. Absent or disordered ICC networks can be associated with disorders in GIT motility. This review highlights the mechanism of ICC recovery from various types of injury which entails understanding the development of ICC and the factors affecting it. ICC transformation into malignant tumours (gastrointestinal stromal tumours) and their potential as contributors to therapeutic resistance is also discussed.

Interstitial cell of Cajal loss correlates with the degree of inflammation in the human appendix and reverses after inflammation

BACKGROUND

Normal gut motility relies on the complex interaction between the interstitial cell of Cajal (ICC) and the enteric nerve networks. Inflammation of the gastrointestinal tract adversely affects both ICC and enteric nerves. We aimed to determine the distribution of ICC and nerve networks in patients with appendicitis.

METHODS

Specimens from controls and patients with appendicitis were examined with immunohistochemistry (c-Kit for ICC, beta III tubulin [Tuj-1] and neuronal nitric oxide synthase [histochemical diaphorase] for nitrergic neurons) and electron microscopy (EM). Data were quantified using image analysis.

RESULTS

We found a profound decrease in c-Kit immunoreactivity (c-Kit IR) in the advanced inflammatory stages of appendicitis, which correlated with the severity of inflammation. Electron microscopy confirmed ultrastructural injury in both ICC and nerve fiber networks during acute inflammation. After the inflammation resolved, interval appendices displayed a recovery in ICC c-Kit IR to control levels and normal ultrastructure. The neuronal network also displayed ultrastructural recovery; however, neuronal nitric oxide synthase activity did not recover.

CONCLUSIONS

Severe inflammation results in significant ultrastructural damage of nerves and ICC networks in appendicitis. The loss of c-Kit IR is likely due to impaired ICC cytophysiology because ICC was still present under EM. After resolution of acute inflammation, ICC recovers their normal ultrastructure and c-Kit IR.

Irritable bowel syndrome and the elusive mast cells

Irritable bowel syndrome (IBS) is the most common condition seen by gastroenterologists. It presents with alternating symptoms of bowel dysfunction that often worsens with stress. The cause of these symptoms eludes investigators and many attempts have been made to discover an underlying pathology. This is a daunting task since symptoms come and go, and change characteristics. Furthermore, the pathology of IBS is unlikely to be identical in all patients. In addition, all symptoms and all features studied thus far have a strong overlap with healthy volunteers. Elsewhere in this issue, Braak et al. report a well-designed clinical investigation in patients with IBS and come to the conclusion that IBS is not characterized by mast cell or other immune cell proliferation, but by immune dysregulation in the colon. Is this the final answer?

Two independent networks of interstitial cells of cajal work cooperatively with the enteric nervous system to create colonic motor patterns

Normal motility of the colon is critical for quality of life and efforts to normalize abnormal colon function have had limited success. A better understanding of control systems of colonic motility is therefore essential. We report here a hypothesis with supporting experimental data to explain the origin of rhythmic propulsive colonic motor activity induced by general distention. The theory holds that both networks of interstitial cells of Cajal (ICC), those associated with the submuscular plexus (ICC-SMP) and those associated with the myenteric plexus (ICC-MP), orchestrate propagating contractions as pacemaker cells in concert with the enteric nervous system (ENS). ICC-SMP generate an omnipresent slow wave activity that causes propagating but non-propulsive contractions ("rhythmic propagating ripples") enhancing absorption. The ICC-MP generate stimulus-dependent cyclic depolarizations propagating anally and directing propulsive activity ("rhythmic propulsive motor complexes"). The ENS is not essential for both rhythmic motor patterns since distention and pharmacological means can produce the motor patterns after blocking neural activity, but it supplies the primary stimulus in vivo. Supporting data come from studies on segments of the rat colon, simultaneously measuring motility through spatiotemporal mapping of video recordings, intraluminal pressure, and outflow measurements.

Crohn's disease: ultrastructure of interstitial cells in colonic myenteric plexus

The role of the interstitial cells of Cajal (ICC) in chronic inflammatory bowel disease, i.e., ulcerative colitis (UC) and Crohn's disease (CD), remains unclear. Ultrastructural alterations in ICC in the colonic myenteric plexus (ICC-MP) have been reported previously in UC, but descriptions of ICC-MP and other interstitial cells in the myenteric region of the colon are lacking for CD. In the present study, we characterized the ultrastructure of interstitial cells, nerves, and glial cells in the myenteric region in Crohn's colitis (CC). In comparison with controls, varicosities of the myenteric bundles were dilated and appeared to be empty. Lipid droplets and lipofuscin-bodies were prominent in glial cells and neurons. ICC-MP were scanty but, as in controls, had caveolae, prominent intermediate filaments, cytoplasmic dense bodies, and membrane-associated dense bands with a patchy basal lamina. ICC-MP were similar in the various colonic regions. ICC-MP in CC showed no signs of degeneration or cytological changes. As in controls, fibroblast-like cells had abundant coated vesicles but lacked prominent intermediate filaments and caveolae. Macrophages also appeared as in controls. In comparison with ICC-MP in UC, the cytology of ICC-MP in CC were thus undisturbed. The ultrastructural differences between UC and CC might reflect pathophysiological differences of importance for understanding pathogenetic differences between CD and UC.

Alterations of Mast Cells in the Esophageal Mucosa of the Patients With Non-Erosive Reflux Disease

BACKGROUND

Mast cells (MCs) are widely distributed in the gastrointestinal tract, which could be involved in visceral hypersensitivity and gut dysmotility. Whether esophageal MCs play a role in non-erosive reflux disease (NERD) has yet to be determined. The aim of this study was to characterize esophageal MCs distribution, degranulation, and ultrastructure.

METHODS

The esophageal mucosa at 5 cm above the end of esophagus was obtained from 26 NERD and 14 healthy volunteers (control) by gastroscopy. Immunohistochemistry was performed and average MC counts per high-power field (HPF) and the percentage of degranulated MCs were obtained. The ultrastructure of MCs was observed by transmission electron microscope (TEM).

RESULTS

More MCs were observed in NERD (7.23 ± 2.41 cells/HPF) as compared with controls (3.79 ± 1.67 cells/HPF) (P < 0.01) and the percentage of degranulated MCs in NERD was also significantly higher than controls (26.85 ± 8.79% vs 11.5 ± 4.18%, P < 0.01). Under TEM, more Golgi apparatus, mitochondria and endoplasmic reticulum were found in MCs in patients with NERD. Special secreting particles were also found in cytoplasm, more vacuoles were left after MCs degranulation in patients with NERD.

CONCLUSIONS

Our results indicate that increased numbers of MCs and MCs activation may be involved in the pathogenesis of NERD.

Ulcerative colitis: ultrastructure of interstitial cells in myenteric plexus

Interstitial cells of Cajal (ICC) are key regulatory cells in the gut. In the colon of patients with severe ulcerative colitis (UC), myenteric ICC had myoid ultrastructural features and were in close contact with nerve terminals. In all patients as opposed to controls, some ICC profiles showed degenerative changes, such as lipid droplets and irregular vacuoles. Nerve terminals often appeared swollen and empty. Glial cells, muscle cells, and fibroblast-like cells (FLC) showed no alterations. FLC enclosed macrophages (MLC), which were in close contact with naked axon terminals. The organization and cytological changes may be of pathophysiological significance in patients with UC.

Crohn's disease of the colon: ultrastructural changes in submuscular interstitial cells of Cajal

Interstitial cells of Cajal (ICC) at the submuscular border of the human colon (ICC-SMP) are the proposed pacemaker cells of the musculature. In patients with Crohn's disease (CD) of the colon, ICC-SMP showed characteristic cytological changes from controls. The changes comprised secondary lysosomes in connection with lipid droplets and cytoplasmic vacuoles or multiple empty, confluent and often outbulging vacuoles merging with cisterns of granular endoplasmic reticulum and clusters of glycogen granules. These changes were most pronounced in patients with macroscopical mucosal inflammation but were also demonstrable in uninvolved colonic segments. Relationships of ICC to other cells were undisturbed. The changes were selective to ICC-SMP, as glial cells, muscle cells and fibroblast-like cells at the submuscular border showed no cytological alterations compared with controls. Varicosities of the submuscular plexus were often empty and dilated. Fibroblast-like cells selectively encased macrophages and mast cells. The cytological changes in ICC-SMP in CD are thus similar to changes seen in ulcerative colitis and may be of pathophysiological significance with regard to the motility and sensory disturbances seen in patients with CD.

Recent advances in studies of spontaneous activity in smooth muscle: ubiquitous pacemaker cells

The general and specific properties of pacemaker cells, including Kit-negative cells, that are distributed in gastrointestinal, urethral and uterine smooth muscle tissues, are discussed herein. In intestinal tissues, interstitial cells of Cajal (ICC) are heterogeneous in both their forms and roles. ICC distributed in the myenteric layer (ICC-MY) act as primary pacemaker cells for intestinal mechanical and electrical activity. ICC distributed in muscle bundles play a role as mediators of signals from autonomic nerves to smooth muscle cells. A group of ICC also appears to act as a stretch sensor. Intracellular Ca2+ dynamics play a crucial role in ICC-MY pacemaking; intracellular Ca2+ ([Ca2+](i)) oscillations periodically activate plasmalemmal Ca2+-activated ion channels, such as Ca2+-activated Cl(-) channels and/or non-selective cation channels, although the relative contributions of these channels are not defined. With respect to gut motility, both the ICC network and enteric nervous system, including excitatory and inhibitory enteric neurons, play an essential role in producing highly coordinated peristalsis.

A model to study the phenotypic changes of interstitial cells of Cajal in gastrointestinal diseases

BACKGROUND & AIMS

Interstitial cells of Cajal (ICC) express the receptor tyrosine kinase, KIT, the receptor for stem cell factor. In the gastrointestinal (GI) tract, ICC are pacemaker cells that generate spontaneous electrical slow waves, and mediate inputs from motor neurons. Absence or loss of ICC are associated with GI motility disorders, including those consequent of diabetes. Studies of ICC have been hampered by the low density of these cells and difficulties in recognizing these cells in cell dispersions.

METHODS

Kit(+/copGFP) mice harboring a copepod super green fluorescent protein (copGFP) complementary DNA, inserted at the Kit locus, were generated. copGFP(+) ICC from GI muscles were analyzed using confocal microscopy and flow cytometry. copGFP(+) ICC from the jejunum were purified by a fluorescence-activated cell sorter and validated by cell-specific markers. Kit(+/copGFP) mice were crossbred with diabetic Lep(+/ob) mice to generate compound Kit(+/copGFP);Lep(ob/ob) mutant mice. copGFP(+) ICC from compound transgenic mice were analyzed by confocal microscopy.

RESULTS

copGFP in Kit(+/copGFP) mice colocalized with KIT immunofluorescence and thus was predominantly found in ICC. In other smooth muscles, mast cells were also labeled, but these cells were relatively rare in the murine GI tract. copGFP(+) cells from jejunal muscles were Kit(+) and free of contaminating cell-specific markers. Kit(+/copGFP);Lep(ob/ob) mice displayed ICC networks that were dramatically disrupted during the development of diabetes.

CONCLUSIONS

Kit(+/copGFP) mice offer a powerful new model to study the function and genetic regulation of ICC phenotypes. Isolation of ICC from animal models will help determine the causes and responses of ICC to therapeutic agents.

Interstitial cells of Cajal, macrophages and mast cells in the gut musculature: morphology, distribution, spatial and possible functional interactions

Interstitial cells of Cajal (ICC) are recognized as pacemaker cells for gastrointestinal movement and are suggested to be mediators of neuromuscular transmission. Intestinal motility disturbances are often associated with a reduced number of ICC and/or ultrastructural damage, sometimes associated with immune cells. Macrophages and mast cells in the intestinal muscularis externa of rodents can be found in close spatial contact with ICC. Macrophages are a constant and regularly distributed cell population in the serosa and at the level of Auerbach's plexus (AP). In human colon, ICC are in close contact with macrophages at the level of AP, suggesting functional interaction. It has therefore been proposed that ICC and macrophages interact. Macrophages and mast cells are considered to play important roles in the innate immune defence by producing pro-inflammatory mediators during classical activation, which may in itself result in damage to the tissue. They also take part in alternative activation which is associated with anti-inflammatory mediators, tissue remodelling and homeostasis, cancer, helminth infections and immunophenotype switch. ICC become damaged under various circumstances - surgical resection, possibly post-operative ileus in rodents - where innate activation takes place, and in helminth infections - where alternative activation takes place. During alternative activation the muscularis macrophage can switch phenotype resulting in up-regulation of F4/80 and the mannose receptor. In more chronic conditions such as Crohn's disease and achalasia, ICC and mast cells develop close spatial contacts and piecemeal degranulation is possibly triggered.

Relaxation patterns of human gastric corporal smooth muscle by cyclic nucleotides producing agents

To elucidate the mechanism of cyclic nucleotides, such as adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5' -cyclic monophosphate (cGMP), in the regulation of human gastric motility, we examined the effects of forskolin (FSK), isoproterenol (ISO) and sodium nitroprusside (SNP) on the spontaneous, high K(+) and acetylcholine (ACh)-induced contractions of corporal circular smooth muscle in human stomach. Gastric circular smooth muscle showed regular spontaneous contraction, and FSK, ISO and SNP inhibited its phasic contraction and basal tone in a concentration-dependent manner. High K(+) (50 mM) produced sustained tonic contraction, and ACh (10 microM) produced initial transient contraction followed by later sustained tonic contraction with superimposed phasic contractions. FSK, ISO and SNP inhibited high K(+)-induced tonic contraction and also ACh-induced phasic and tonic contraction in a reversible manner. Nifedipine (1 microM), inhibitor of voltage-dependent L-type calcium current (VDCC(L)), almost abolished ACh-induced phasic contractions. These findings suggest that FSK, ISO and SNP, which are known cyclic nucleotide stimulators, inhibit smooth muscle contraction in human stomach partly via inhibition of VDCC(L).

Interstitial cells of Cajal and gastrointestinal inflammation and immunity

Interstitial cells of Cajal (ICC) in gastrointestinal tract are closely linked to gastrointestinal inflammation and dysmotility from various causes. During gastrointestinal inflammation, ICC show varying degrees of changes in their structure, number and functions. In addition, the immune mechanisms involved in the pathogenesis of gastrointestinal inflammation have also attracted wide attention. In this article, we will review the changes in ICC in gastrointestinal inflammation and immunity.

Enteric neuroglial apoptosis in inflammatory bowel diseases

BACKGROUND

Enteric nervous system abnormalities have been described in patients with inflammatory bowel diseases. However, the mechanisms responsible for these abnormalities remain to date largely unknown.

AIMS

We investigated the potential role of apoptotic phenomena in enteric neurons and enteroglial cells in patients with inflammatory bowel diseases.

PATIENTS AND METHODS

Full-thickness surgical specimens of 19 patients undergoing surgery for medically refractory disease (9 from the ileum of patients with Crohn's disease, 10 from the colon of patients with ulcerative colitis) were assessed for the presence of enteric neurons and enteroglial cells and for their apoptosis by two immunohistochemical methods, one also able to distinguish apoptosis from necrosis. The results were compared with those obtained in control specimens.

RESULTS

Concerning Crohn's disease, the ileal segments displayed a significant increase of apoptotic enteric neurons and enteroglial cells in both the submucous and the myenteric plexus compared to controls. In patients with ulcerative colitis, compared to controls, apoptotic phenomena were significantly reduced in enteric neurons, whereas they were increased in the enteroglial cell population (submucous and myenteric plexus).

CONCLUSIONS

In patients with inflammatory bowel disease apoptotic phenomena involve both enteric neurons and enteroglial cells, and may play a role in the abnormalities of the enteric nervous system. The importance of these findings in the pathophysiology of these conditions remains to be determined.

Mast cell adhesion induces cytoskeletal modifications and programmed cell death in oligodendrocytes

In this paper we show that rat peritoneal mast cells (RPMC) adhere to rat oligodendrocytes (ODC) in culture and switch on a bi-directional signal affecting both adhering cell and its target. Following heterotypic interaction, RPMC release granule content and ODC show morphological changes and enter the apoptotic programme. Altogether, these findings indicate that the interaction of MC with ODC could play a role in the mechanism of CNS damage induced by the inflammatory reaction.

Physiology, injury, and recovery of interstitial cells of Cajal: basic and clinical science

In the last 15 years, our understanding of the cellular basis of gastrointestinal function has been altered irreversibly by the discovery that normal gastrointestinal motility requires interstitial cells of Cajal (ICC). Research in this relatively short time period has modified our original concept that the core unit that controls motility is made up of nerves and smooth muscle, to one that now includes ICC. This concept has now expanded to beyond the gastrointestinal tract, suggesting that it may be a fundamental property of the regulation of smooth muscle function that requires rhythmic contraction. ICC are distributed throughout the gastrointestinal tract, have important functions in the control of gastrointestinal motility and are often abnormal in diseased states. Recently, significant steps forward have been made in our understanding of the physiology of ICC as well as mechanisms of injury and recovery. These advances will be the focus of this review.

Exploring the role of mast cells in eosinophilic esophagitis

The mast cell plays a critical role in allergic responses in the gastrointestinal tract and other sites. Emerging evidence indicates that mast cells also participate in the pathogenesis of eosinophilic esophagitis, although their precise role has not been defined. This article reviews the biology of mast cells and examines the potential involvement of the cell as an effector of the inflammatory response and tissue remodeling, and as a cell that has the potential to function as an immunomodulator and limit inflammation.

Loss of intramuscular and submuscular interstitial cells of Cajal and associated enteric nerves is related to decreased gastric emptying in streptozotocin-induced diabetes

Interstitial cells of Cajal (ICC) are associated with afferent innervation and peristalsis of the stomach suggestive of a key role in the pathophysiology of gastroparesis. We studied changes in the density and ultrastructure of ICC and enteric nerves in the streptozotocin-induced diabetes mellitus (STZ-DM) in Wistar rats using immunohistochemistry and electron microscopy. Gastric emptying was studied in vivo by single-photon emission computed tomography. In the STZ-DM antrum, a marked reduction was observed in the density of the intramuscular ICC (ICC-IM) and ICC located at the submucosal border of the circular muscle layer of the antrum (ICC-SM). The surviving ICC showed lamellar bodies and partial vacuolation of the cytoplasm content, loss of connections between ICC-IM and nerves; it appeared that injured ICC-IM developed into fibroblast-like ICC. ICC associated with Auerbach's plexus (ICC-AP) in the antrum and ICC in the fundus were not affected significantly except for a loss of connections with nerve structures. Marked reduction in nerve tissue (Protein Gene Product-9.5 positivity) was also restricted to the muscle layers including nitrergic nerves (neuronal nitric oxide synthase positivity). In vivo assessed gastric emptying was markedly reduced in STZ-DM rats. Our data demonstrate in the STZ-DM rat stomach a decreased density of ICC limited to the antrum and to ICC-IM and ICC-SM, and structural degeneration in ICC-IM and associated nerves with a special emphasis on loss of synaptic connections, accompanied by a decrease in gastric emptying. Hence, in this model of gastroparetic diabetes, regional injury to subsets of ICC and nerves are associated with gastric motor dysfunction.

Igf1r+/CD34+ immature ICC are putative adult progenitor cells, identified ultrastructurally as fibroblast-like ICC in Ws/Ws rat colon

The colon of Ws/Ws mutant rats shows impairment of pacemaker activity and altered inhibitory neurotransmission. The present study set out to find structural correlates to these findings to resolve mechanisms. In the colon of Ws/Ws rats, interstitial cells of Cajal associated with Auerbach's plexus (ICC-AP) were significantly decreased and ICC located at the submuscular plexus and intramuscular ICC were rarely observed based on immunohistochemistry and electron microscopy. Ultrastructural investigations revealed that there was no overall loss of all types of interstitial cells combined. Where loss of ICC was observed, a marked increase in fibroblast-like ICC (FL-ICC) was found at the level of AP. Immunoelectron microscopy proved FL-ICC to be c-Kit(-) but gap junction coupled to each other and to c-Kit(+) ICC; they were associated with enteric nerves and occupied space normally occupied by ICC in the wild-type rat colon, suggesting them to be immature ICC. In addition, a marked increase in immunoreactivity for insulin-like growth factor 1 receptor (Igf1r) occurred, co-localized with CD34 but not with c-Kit. A significantly higher number of Igf1r(+)/CD34(+) cells were found in Ws/Ws compared to wild-type rat colons. These CD34(+)/Igf1r(+) cells in the Ws/Ws colon occupied the same space as FL-ICC. Hence we propose that a subset of immature ICC (FL-ICC) consists of adult progenitor cells. Immunohistochemistry revealed a reduction of neurons positive for neuronal nitric oxide synthase. The functional capabilities of the immature ICC and the regenerative capabilities of the adult progenitor cells need further study. The morphological features described here show that the loss of pacemaker activity is not associated with failure to develop a network of interstitial cells around AP but a failure to develop this network into fully functional pacemaker cells. The reduction in nitrergic innervation associated with the Ws mutation may be the result of a reduction in nitrergic neurons.

Microelectrode array evaluation of gut pacemaker activity in wild-type and W/W(v) mice

Interstitial cells of Cajal in the myenteric plexus region (ICC-MyP) form a network and generate basal pacemaking electrical activity. This morphological feature leads us to believe that these cells may be essential for the coordinating actions of gastrointestinal (GI) motility. We aim to propose a new method for functional assessment of ICC electrical activity and its network. Field potentials in a approximately 1 mm(2) region were simultaneously measured using an 8x8 microelectrode array (MEA) with a polar distance of 150 microm. The extracellular solution contained nifedipine and tetrodotoxin (TTX) to suppress activities of smooth muscle cells and neurons, respectively. We compared spatial electrical activities between ileal muscle preparations from wild-type (WT) and W/W(v) mice. In spatio-temporal analyses, basal electrical activities were well synchronized with a propagation delay in WT, while those in W/W(v) were small in amplitude and irregular in occurrence. The power spectrum in WT had a prominent peak corresponding to the frequency of ICC-MyP pacemaker activity, while that of W/W(v) lacked it. Consequently, the ratio of the spectral power in 9.4-27.0 cpm was significantly larger in WT than in W/W(v). In conclusion, MEA measurements demonstrated that the network-forming ICC-MyP not only generates but also coordinates basal electrical activities. Disorders of GI motility based on morphological and functional impairments of ICC network with the range of several hundreds of micrometers, could be uncovered in future extensive studies.

Mast cells and gastrointestinal dysmotility in the cystic fibrosis mouse

BACKGROUND

Cystic fibrosis (CF) has many effects on the gastrointestinal tract and a common problem in this disease is poor nutrition. In the CF mouse there is an innate immune response with a large influx of mast cells into the muscularis externa of the small intestine and gastrointestinal dysmotility. The aim of this study was to evaluate the potential role of mast cells in gastrointestinal dysmotility using the CF mouse (Cftr(tm1UNC), Cftr knockout).

METHODOLOGY

Wild type (WT) and CF mice were treated for 3 weeks with mast cell stabilizing drugs (ketotifen, cromolyn, doxantrazole) or were treated acutely with a mast cell activator (compound 48/80). Gastrointestinal transit was measured using gavage of a fluorescent tracer.

RESULTS

In CF mice gastric emptying at 20 min post-gavage did not differ from WT, but was significantly less than in WT at 90 min post-gavage. Gastric emptying was significantly increased in WT mice by doxantrazole, but none of the mast cell stabilizers had any significant effect on gastric emptying in CF mice. Mast cell activation significantly enhanced gastric emptying in WT mice but not in CF mice. Small intestinal transit was significantly less in CF mice as compared to WT. Of the mast cell stabilizers, only doxantrazole significantly affected small intestinal transit in WT mice and none had any effect in CF mice. Mast cell activation resulted in a small but significant increase in small intestinal transit in CF mice but not WT mice.

CONCLUSIONS

The results indicate that mast cells are not involved in gastrointestinal dysmotility but their activation can stimulate small intestinal transit in cystic fibrosis.