A lack of intestinal pacemaker (c-kit) in aganglionic bowel of patients with Hirschsprung's disease

Ca2+ dynamics in interstitial cells: foundational mechanisms for the motor patterns in the gastrointestinal tract

The gastrointestinal (GI) tract displays multiple motor patterns that move nutrients and wastes through the body. Smooth muscle cells (SMCs) provide the forces necessary for GI motility, but interstitial cells, electrically coupled to SMCs, tune SMC excitability, transduce inputs from enteric motor neurons, and generate pacemaker activity that underlies major motor patterns, such as peristalsis and segmentation. The interstitial cells regulating SMCs are interstitial cells of Cajal (ICC) and PDGF receptor (PDGFR)α+ cells. Together these cells form the SIP syncytium. ICC and PDGFRα+ cells express signature Ca2+-dependent conductances: ICC express Ca2+-activated Cl- channels, encoded by Ano1, that generate inward current, and PDGFRα+ cells express Ca2+-activated K+ channels, encoded by Kcnn3, that generate outward current. The open probabilities of interstitial cell conductances are controlled by Ca2+ release from the endoplasmic reticulum. The resulting Ca2+ transients occur spontaneously in a stochastic manner. Ca2+ transients in ICC induce spontaneous transient inward currents and spontaneous transient depolarizations (STDs). Neurotransmission increases or decreases Ca2+ transients, and the resulting depolarizing or hyperpolarizing responses conduct to other cells in the SIP syncytium. In pacemaker ICC, STDs activate voltage-dependent Ca2+ influx, which initiates a cluster of Ca2+ transients and sustains activation of ANO1 channels and depolarization during slow waves. Regulation of GI motility has traditionally been described as neurogenic and myogenic. Recent advances in understanding Ca2+ handling mechanisms in interstitial cells and how these mechanisms influence motor patterns of the GI tract suggest that the term "myogenic" should be replaced by the term "SIPgenic," as this review discusses.

Interstitial cells of Cajal: clinical relevance in pediatric gastrointestinal motility disorders

Interstitial cells of Cajal (ICCs) are pacemaker cells of gastrointestinal motility that generate and transmit electrical slow waves to smooth muscle cells in the gut wall, thus inducing phasic contractions and coordinated peristalsis. Traditionally, tyrosine-protein kinase Kit (c-kit), also known as CD117 or mast/stem cell growth factor receptor, has been used as the primary marker of ICCs in pathology specimens. More recently, the Ca2+-activated chloride channel, anoctamin-1, has been introduced as a more specific marker of ICCs. Over the years, various gastrointestinal motility disorders have been described in infants and young children in which symptoms of functional bowel obstruction arise from ICC-related neuromuscular dysfunction of the colon and rectum. The current article provides a comprehensive overview of the embryonic origin, distribution, and functions of ICCs, while also illustrating the absence or deficiency of ICCs in pediatric patients with Hirschsprung disease intestinal neuronal dysplasia, isolated hypoganglionosis, internal anal sphincter achalasia, and congenital smooth muscle cell disorders such as megacystis microcolon intestinal hypoperistalsis syndrome.

Intestinal proinflammatory macrophages induce a phenotypic switch in interstitial cells of Cajal

Interstitial cells of Cajal (ICCs) are pacemaker cells in the intestine, and their function can be compromised by loss of C-KIT expression. Macrophage activation has been identified in intestine affected by Hirschsprung disease-associated enterocolitis (HAEC). In this study, we examined proinflammatory macrophage activation and explored the mechanisms by which it downregulates C-KIT expression in ICCs in colon affected by HAEC. We found that macrophage activation and TNF-α production were dramatically increased in the proximal dilated colon of HAEC patients and 3-week-old Ednrb-/- mice. Moreover, ICCs lost their C-KIT+ phenotype in the dilated colon, resulting in damaged pacemaker function and intestinal dysmotility. However, macrophage depletion or TNF-α neutralization led to recovery of ICC phenotype and restored their pacemaker function. In isolated ICCs, TNF-α-mediated phosphorylation of p65 induced overexpression of microRNA-221 (miR-221), resulting in suppression of C-KIT expression and pacemaker currents. We also identified a TNF-α/NF-κB/miR-221 pathway that downregulated C-KIT expression in ICCs in the colon affected by HAEC. These findings suggest the important roles of proinflammatory macrophage activation in a phenotypic switch of ICCs, representing a promising therapeutic target for HAEC.

Current applications of mathematical models of the interstitial cells of Cajal in the gastrointestinal tract

The interstitial cells of Cajal (ICC) form interconnected networks throughout the gastrointestinal (GI) tract. ICC act as the pacemaker cells that initiate the rhythmic bioelectrical slow waves and intermediary between the GI musculature and nerves, both of which are critical to GI motility. Disruptions to the number of ICC and the integrity of ICC networks have been identified as a key pathophysiological mechanism in a number of clinically challenging GI disorders. The current analyses of ICC generally rely on either functional recordings taken directly from excised tissue or morphological analysis based on images of labeled ICC, where the structural-functional relationship is investigated in an associative manner rather than mechanistically. On the other hand, computational physiology has played a significant role in facilitating our understanding of a number of physiological systems in both health and disease, and investigations in the GI field are beginning to incorporate several mathematical models of the ICC. The main aim of this review is to present the major modeling advances in GI electrophysiology, in order to introduce a multi-scale framework for mathematically quantifying the functional consequences of ICC degradation at both cellular and tissue scales. The outcomes will inform future investigators utilizing modeling techniques in their studies. This article is categorized under: Metabolic Diseases > Computational Models.

Prototypical pacemaker neurons interact with the resident microbiota

Pacemaker neurons exert control over neuronal circuit function by their intrinsic ability to generate rhythmic bursts of action potential. Recent work has identified rhythmic gut contractions in human, mice, and hydra to be dependent on both neurons and the resident microbiota. However, little is known about the evolutionary origin of these neurons and their interaction with microbes. In this study, we identified and functionally characterized prototypical ANO/SCN/TRPM ion channel-expressing pacemaker cells in the basal metazoan Hydra by using a combination of single-cell transcriptomics, immunochemistry, and functional experiments. Unexpectedly, these prototypical pacemaker neurons express a rich set of immune-related genes mediating their interaction with the microbial environment. Furthermore, functional experiments gave a strong support to a model of the evolutionary emergence of pacemaker cells as neurons using components of innate immunity to interact with the microbial environment and ion channels to generate rhythmic contractions.

Pathological changes of interstitial cells of Cajal and ganglion cells in the segment of resected bowel in Hirschsprung's disease

OBJECTIVES

This study was conducted to investigate the pathological changes which occur in interstitial cells of Cajal (ICCs) and ganglion cells found in segments of resected bowel obtained from patients with Hirschsprung's disease (HD), as well as to explore the benefits of using a contrast enema (CE) with 24-h delayed X-ray films to predict the length of resected bowel.

METHODS

We performed a retrospective analysis of 58 children with HD who had undergone the pull-through procedure. After each operation, the ICCs and ganglion cells present in the proximal ends of the barium residue (Level A) and resected proximal bowel segment (Level B) were analyzed using immunohistochemical staining methods. Each patient was followed up for 1 year to record their stool frequency, defecation control ability, and post-surgical complications which may have occurred.

RESULTS

Immunohistochemical staining detected fewer ICCs in Level A than in Level B (p < 0.05). However, the density of ganglion cells in the two levels was not significantly different (p > 0.05). One patient had anastomotic stricture, and five patients suffered from enterocolitis.

CONCLUSIONS

The density of ICCs was significantly lower in the bowel segments that displayed barium retention. A CE may be a valuable tool for predicting the length of bowel resection in patients with HD.

Persistent mechanical stretch-induced calcium overload and MAPK signal activation contributed to SCF reduction in colonic smooth muscle in vivo and in vitro

Gastrointestinal (GI) distention is a common pathological characteristic in most GI motility disorders (GMDs), however, their detail mechanism remains unknown. In this study, we focused on Ca²⁺ overload of smooth muscle, which is an early intracellular reaction to stretch, and its downstream MAPK signaling and also reduction of SCF in vivo and in vitro. We successfully established colonic dilation mouse model by keeping incomplete colon obstruction for 8 days. The results showed that persistent colonic dilation clearly induced Ca²⁺ overload and activated all the three MAPK family members including JNK, ERK and p38 in smooth muscle tissues. Similar results were obtained from dilated colon of patients with Hirschsprung's disease and stretched primary mouse colonic smooth muscle cells (SMCs). Furthermore, we demonstrated that persistent stretch-induced Ca²⁺ overload was originated from extracellular Ca²⁺ influx and endoplasmic reticulum (ER) Ca²⁺ release identified by treating with different Ca²⁺ channel blockers, and was responsible for the persistent activation of MAPK signaling and SCF reduction in colonic SMCs. Our results suggested that Ca²⁺ overload caused by smooth muscle stretch led to persistent activation of MAPK signaling which might contribute to the decrease of SCF and development of the GMDs.

Electrophysiological Mechanisms of Gastrointestinal Arrhythmogenesis: Lessons from the Heart

Disruptions in the orderly activation and recovery of electrical excitation traveling through the heart and the gastrointestinal (GI) tract can lead to arrhythmogenesis. For example, cardiac arrhythmias predispose to thromboembolic events resulting in cerebrovascular accidents and myocardial infarction, and to sudden cardiac death. By contrast, arrhythmias in the GI tract are usually not life-threatening and much less well characterized. However, they have been implicated in the pathogenesis of a number of GI motility disorders, including gastroparesis, dyspepsia, irritable bowel syndrome, mesenteric ischaemia, Hirschsprung disease, slow transit constipation, all of which are associated with significant morbidity. Both cardiac and gastrointestinal arrhythmias can broadly be divided into non-reentrant and reentrant activity. The aim of this paper is to compare and contrast the mechanisms underlying arrhythmogenesis in both systems to provide insight into the pathogenesis of GI motility disorders and potential molecular targets for future therapy.

Mechanisms of Electrical Activation and Conduction in the Gastrointestinal System: Lessons from Cardiac Electrophysiology

The gastrointestinal (GI) tract is an electrically excitable organ system containing multiple cell types, which coordinate electrical activity propagating through this tract. Disruption in its normal electrophysiology is observed in a number of GI motility disorders. However, this is not well characterized and the field of GI electrophysiology is much less developed compared to the cardiac field. The aim of this article is to use the established knowledge of cardiac electrophysiology to shed light on the mechanisms of electrical activation and propagation along the GI tract, and how abnormalities in these processes lead to motility disorders and suggest better treatment options based on this improved understanding. In the first part of the article, the ionic contributions to the generation of GI slow wave and the cardiac action potential (AP) are reviewed. Propagation of these electrical signals can be described by the core conductor theory in both systems. However, specifically for the GI tract, the following unique properties are observed: changes in slow wave frequency along its length, periods of quiescence, synchronization in short distances and desynchronization over long distances. These are best described by a coupled oscillator theory. Other differences include the diminished role of gap junctions in mediating this conduction in the GI tract compared to the heart. The electrophysiology of conditions such as gastroesophageal reflux disease and gastroparesis, and functional problems such as irritable bowel syndrome are discussed in detail, with reference to ion channel abnormalities and potential therapeutic targets. A deeper understanding of the molecular basis and physiological mechanisms underlying GI motility disorders will enable the development of better diagnostic and therapeutic tools and the advancement of this field.

The zebrafish mutant lessen: an experimental model for congenital enteric neuropathies

BACKGROUND

Congenital enteric neuropathies of the distal intestine (CEN) are characterized by the partial or complete absence of enteric neurons. Over the last decade, zebrafish has emerged as a leading model organism in experimental research. Our aim was to demonstrate that the mutant zebrafish, lessen, expressing CEN characteristics, is an equally valuable animal model alongside mammalian models for CEN, by studying its enteric phenotype.

METHODS

The effect of the lessen mutation on the development of the enteric nervous system (ENS), interstitial cells of Cajal (ICC), and intestinal motility in each intestinal region of mutant and wild-type (wt) zebrafish embryos at 3-6 dpf, was analyzed by immunofluorescent detection of neurochemical markers and motility assays.

KEY RESULTS

Development of intestinal motility in the mutant was delayed and the majority of the observed contractions were disturbed. A significant disturbance in ENS development resulted in a distal intestine that was almost free of neuronal elements, in reduced neuronal density in the proximal and mid-intestine, and in a defect in the expression of neurochemical markers. Furthermore, markedly disturbed development of ICC gave rise to a less dense network of ICC.

CONCLUSIONS & INFERENCES

The observed alterations in intestinal motility, intrinsic innervation and ICC network of the mutant in comparison with the wt zebrafish, are similar to those seen in the oligo- and aganglionic regions of the intestine of CEN patients. It is concluded that the zebrafish mutant lessen is an appropriate animal model to investigate CEN.

Interstitial cells: regulators of smooth muscle function

Smooth muscles are complex tissues containing a variety of cells in addition to muscle cells. Interstitial cells of mesenchymal origin interact with and form electrical connectivity with smooth muscle cells in many organs, and these cells provide important regulatory functions. For example, in the gastrointestinal tract, interstitial cells of Cajal (ICC) and PDGFRα(+) cells have been described, in detail, and represent distinct classes of cells with unique ultrastructure, molecular phenotypes, and functions. Smooth muscle cells are electrically coupled to ICC and PDGFRα(+) cells, forming an integrated unit called the SIP syncytium. SIP cells express a variety of receptors and ion channels, and conductance changes in any type of SIP cell affect the excitability and responses of the syncytium. SIP cells are known to provide pacemaker activity, propagation pathways for slow waves, transduction of inputs from motor neurons, and mechanosensitivity. Loss of interstitial cells has been associated with motor disorders of the gut. Interstitial cells are also found in a variety of other smooth muscles; however, in most cases, the physiological and pathophysiological roles for these cells have not been clearly defined. This review describes structural, functional, and molecular features of interstitial cells and discusses their contributions in determining the behaviors of smooth muscle tissues.

Effects of lipopolysaccharide-induced inflammation on the interstitial cells of Cajal

Interstitial cells of Cajal (ICC) have recently been found to display phenotypic changes. The present study is designed to determine whether phenotypic changes occur in ICC associated with an inflammatory microenvironment and whether the ICC phenotype could be recovered after the discontinuation of inflammatory stimuli. Immunohistochemistry studies revealed that the functional ICC marker, c-kit, was markedly reduced in patients with Hirschsprung's disease (n = 34) compared with controls (n = 12), whereas another marker of ICC, CD34, was not altered significantly. Compared with the vehicle group (n = 6), intraperitoneal injection of lipopolysaccharide (LPS; 1.5 mg/kg) in mice (n = 6) significantly induced plasma tumor necrosis factor-alpha (TNF-α) levels as determined by enzyme-linked immunosorbent assay. Western blot and real-time polymerase chain reaction assessment further showed that LPS injection markedly suppressed intestinal c-kit protein and mRNA expression, which could be blocked by Toll-like receptor 4 (TLR4) deficiency (n = 6) rather than TLR2 deficiency (n = 6) and had no effects on CD34. Compared with the vehicle group (n = 6), intraperitoneal TNF-α (30 μg/kg) administration (n = 6) also significantly reduced intestinal c-kit protein and mRNA levels but not CD34 levels. However, the reduction of c-kit induced by TNF-α injection was not suppressed by TLR4 deficiency (n = 6). Intestinal c-kit protein and mRNA levels were markedly restored after the discontinuation of TNF-α administration for 7 days. Moreover, immunofluorescence analysis of primary ICC further confirmed that exposure to TNF-α for 24 h suppressed c-kit expression, which could be restored after discontinuation of TNF-α exposure. CD34 expression was not altered upon exposure to TNF-α. Thus, phenotypic changes in ICC occur in an inflammatory microenvironment in the gut and LPS, TLR4 and TNFα are crucial to this process.

Interstitial cells of Cajal in the normal human gut and in Hirschsprung disease

Hirschsprung disease (HD) is the most prevalent congenital gastrointestinal motility disorder. The pathogenesis of HD is defined as a functional intestinal obstruction resulting from a defect in the intrinsic innervation of the distal bowel. In addition to the enteric nervous system, the interstitial cells of Cajal (ICC) play an important role in the generation of coordinated gastrointestinal peristalsis. The major function of the ICCs is the generation of slow waves that allow these cells to act as specialised pacemaker cells within various tissues. ICCs have additional functions in the gastrointestinal tract as regulators of mechanical activity and neurotransmission. Due to the central role of ICCs in gastrointestinal peristalsis, it has been suggested that defects or impairments of the ICCs may contribute to motility dysfunction in several gastrointestinal motility disorders. This review describes the distribution and functions of ICCs in the normal gut and in Hirschsprung disease.

Immunohistochemical and electron microscopic examination of Cajal cells in ureteropelvic junction obstruction

OBJECTIVE

We examine the ultrastructural configurations of Cajal cells by electron microscopy, as well as the quantitative changes occurring in Cajal cells by light microscopy.

METHODS

In total, 35 patients with ureteropelvic junction (UPJ) obstruction and 7 patients without obstruction were compared immunohistochemically with c-kit (CD117) to quantify the number of cells. On electron microscopic examination, 7 patients with UPJ obstruction and 3 patients without obstruction were compared to evaluate the changes which occurred in the ultrastructural configuration of the Cajal cells.

RESULTS

On light microscopic examination, it was determined that the Cajal cells, which demonstrate c-kit (CD117) immunoreactive character, were located near the circular muscle layer and parallel to the muscle cells. The number of Cajal cells in the control group was significantly increased compared to the number of cells in patients with UPJ obstruction (p < 0.001). On electron microscopic examination, the number of interstitial cells was also higher in the control group. A decrease in the number of the caveolae in these cells was seen in the group with UPJ obstruction compared to the control group.

CONCLUSION

In UPJ obstruction, a decrease in the number of Cajal cells, as well as the changes in the morphologic structure of the Cajal cells, indicates that these cells have a role in the pacemaker system and are associated with ureteral peristalsis.

The importance of interstitial cells of cajal in the gastrointestinal tract

Gastrointestinal (GI) motility function and its regulation is a complex process involving collaboration and communication of multiple cell types such as enteric neurons, interstitial cells of Cajal (ICC), and smooth muscle cells. Recent advances in GI research made a better understanding of ICC function and their role in the GI tract, and studies based on different types of techniques have shown that ICC, as an integral part of the GI neuromuscular apparatus, transduce inputs from enteric motor neurons, generate intrinsic electrical rhythmicity in phasic smooth muscles, and have a mechanical sensation ability. Absence or improper function of these cells has been linked to some GI tract disorders. This paper provides a general overview of ICC; their discovery, subtypes, function, locations in the GI tract, and some disorders associated with their loss or disease, and highlights some controversial issues with regard to the importance of ICC in the GI tract.

The significantly reduced number of interstitial cells of Cajal in chagasic megacolon (CM) patients might contribute to the pathophysiology of CM

In addition to neurons, interstitial cells of Cajal (ICC) play an important role in coordinating intestinal motility with a pacemaker function. This study aimed to quantitatively analyze ICC, neurons, and muscular area, the latter to correct for quantitation errors resulting from dilation in case of a megacolon and from the dispersion of ICC that can be attributed to muscular hypertrophy. We analyzed 30 colon samples: ten chagasic megacolon (CM), ten chagasic colons without megacolon (CXM), and ten nonchagasic control patients (NC). We measured the area of muscularis propria and counted the number of neurons of the myenteric plexus in a histological section of an intestinal ring and the number of ICC at the level of the myenteric plexus and circular muscle layer, the latter in a section immunohistochemically stained for CD117. Muscular hypertrophy occurred only in the CM group. Compared to the NC group, we found in the CM group a statistically significant reduction of 80 % in the number of neurons, 60 % in the number of ICC in the myenteric plexus, and 38 % in the area of circular muscle. In the CXM group, these numbers were highly variable, and their reduction, less pronounced. We conclude that the number of ICC is significantly reduced in CM patients, and that this might contribute to the pathophysiology of CM. However, the development of CM requires severe denervation, whereas CXM generally exhibits less than 50 % denervation, favoring the hypothesis that the reduction in ICC number is, in part, a consequence of denervation.

Differentiation of interstitial cells of Cajal in the human distal colon

At the end of the embryonic period of human development, interstitial cells of Cajal (ICC) are present in the esophagus, stomach, and proximal duodenum, around the inception of the myenteric plexus (MP) ganglia. In the small and large bowel, ICC appear later. The object of the present study was to determine the timing of appearance and pattern of distribution of ICC in the human embryonic and fetal distal colon. Human distal colon specimens were obtained from 8 embryos and 14 fetuses without gastrointestinal disorders. The specimens were 7-16 weeks of gestational age. The specimens were exposed to anti-c-kit antibodies to investigate ICC differentiation. Enteric plexuses were immunohistochemically examined using anti-neuron-specific enolase, and the differentiation of smooth muscle cells was studied with anti-desmin antibodies. In the distal colon, ICC emerged at weeks 10-11 of the fetal period in the form of two parallel belts of densely packed cells extending at the submucous plexus (SMP) and the MP level. These cells correspond to ICC of the SMP (ICC-SMP) and ICC of the MP (ICC-MP). The simultaneous appearance of ICC at the SMP and MP level in the distal colon can be explained by the fact that there are differences in the migration of neural crest cells in particular portions of the digestive tube. In conclusion, in humans, there was a difference in the patterns of development of ICC in the distal colon compared to the rest of the gut.

Spontaneous contractions augmented by cholinergic and adrenergic systems in the human ureter

Interstitial cells of Cajal (ICC) evoke pacemaker activities in many tissues. The purpose of this study was to investigate the relationship between interstitial cell and pacemaker activity in the human ureter through the recording of spontaneous contractions. Spontaneous contractions of eight circular and longitudinal smooth muscle strips of the human ureter to acetylcholine (ACh) and/or norepinephrine (NE) were observed. Human ureteral strips were divided into proximal and distal groups, and each group was subdivided into circular and longitudinal groups. The proximal group showed spontaneous activities of 3~4 times within 5 minutes in the longitudinal group. ACh (10(-4) M) augmented the frequency of the spontaneous contractions. The cumulative application of NE also augmented the frequency in a dose-dependent manner. The effects of NE application were inhibited by concomitant application of 10(-5) M glibenclamide. Receptor tyrosine kinase (c-kit) staining revealed abundant ICCs only in proximal tissues. Therefore, spontaneous contractions of the human ureter might be modulated by ICC in the proximal region, and the actions might be related with the activation of cholinergic and/or adrenergic system mediated by a glibenclamide-sensitive pathway.

Development of c-kit immunopositive interstitial cells of Cajal in the human stomach

Interstitial cells of Cajal (ICC) include several types of specialized cells within the musculature of the gastrointestinal tract (GIT). Some types of ICC act as pacemakers in the GIT musculature, whereas others are implicated in the modulation of enteric neurotransmission. Kit immunohistochemistry reliably identifies the location of these cells and provides information on changes in ICC distribution and density. Human stomach specimens were obtained from 7 embryos and 28 foetuses without gastrointestinal disorders. The specimens were 7-27 weeks of gestational age, and both sexes are represented in the sample. The specimens were exposed to anti-c-kit antibodies to investigate ICC differentiation. Enteric plexuses were immunohistochemically examined by using anti-neuron specific enolase and the differentiation of smooth muscle cells (SMC) was studied with anti-alpha smooth muscle actin and anti-desmin antibodies. By week 7, c-kit-immunopositive precursors formed a layer in the outer stomach wall around myenteric plexus elements. Between 9 and 11 weeks some of these precursors differentiated into ICC. ICC at the myenteric plexus level differentiated first, followed by those within the muscle layer: between SMC, at the circular and longitudinal layers, and within connective tissue septa enveloping muscle bundles. In the fourth month, all subtypes of c-kit-immunoreactivity ICC which are necessary for the generation of slow waves and their transfer to SMC have been developed. These results may help elucidate the origin of ICC and the aetiology and pathogenesis of stomach motility disorders in neonates and young children that are associated with absence or decreased number of these cells.

Pathology of Intestinal Motor Disorders in Children

Varied intestinal neuromuscular pathologies are responsible for Hirschsprung disease and other forms of chronic pseudo-obstruction that are encountered in pediatrics. Pathologically distinct subtypes discussed in this review include aganglionosis, hypoganglionosis, neuronal intranuclear inclusion disease, ganglionitis, degenerative neuropathy, diffuse ganglioneuromatosis, neuronal dysplasia, malformations of the muscularis propria, degenerative leiomyopathy, leiomyositis, and mitochondriopathies. Emphasis is given to the histopathologic features that distinguish these conditions and their differential diagnoses.

Interstitial cells of Cajal, the Maestro in health and disease

Interstitial cells of Cajal (ICC) are important players in the symphony of gut motility. They have a very significant physiological role orchestrating the normal peristaltic activity of the digestive system. They are the pacemaker cells in gastrointestinal (GI) muscles. Absence, reduction in number or altered integrity of the ICC network may have a dramatic effect on GI system motility. More understanding of ICC physiology will foster advances in physiology of gut motility which will help in a future breakthrough in the pharmacological interventions to restore normal motor function of GI tract. This mini review describes what is known about the physiologic function and role of ICCs in GI system motility and in a variety of GI system motility disorders.

Depopulation of interstitial cells of cajal in chagasic megacolon: towards tailored surgery?

BACKGROUND: The mechanism of constipation in patients with Chagasic megacolon remains partially explained. In these patients, it was recently demonstrated a reduction in the population of interstitial cells of Cajal. AIM: To evaluate density of Cajal cells in the surgically resected colon of Chagasic patients in comparison to control patients, and to verify possible association between preoperative and postoperative bowel function of Chagasic patients and colonic cell count. METHOD: Sixteen patients with Chagasic megacolon were operated on. Clinical pre- and post-operative evaluation using the Cleveland Clinic Constipation Score was undertaken. Resected colons were examined. Cajal cells were identified by immunohistochemistry using anti-CD117 antibody. The mean cell number was compared to resected colons from 16 patients with non-obstructive sigmoid cancer. Association between pre-and post-operative constipation scores and cell count for megacolon patients was evaluated using the Pearson coefficient correlation test (r). RESULTS: A reduced number of Cajal cells [cells per field: 2.84 (0-6.6) vs. 9.68 (4.3-13) - p<0.001] was observed in the resected colon of Chagasic patients when compared to colon cancer patients. No correlation between constipation score before (r=-0.205; p=0.45) or after surgery (r=0,291; p=0.28) and cell count for megacolon patients was observed. CONCLUSIONS: Patients with Chagasic megacolon display marked reduction of interstitial cells of Cajal when compared to non-Chagasic patients. An association of constipation severity and Cajal cells depopulation in Chagasic megacolon could not be demonstrated.

Interstitial cells of Cajal reduce in number in recto-sigmoid Hirschsprung's disease and total colonic aganglionosis

Interstitial cells of Cajal (ICCs) play a key role in regulating gastrointestinal tract motility. The pathophysiological basis of colonic aperistalsis in Hirschsprung's disease (HD) is still not fully understood. Many studies reported that decreased numbers or disrupted networks of ICCs were associated with HD. Little information is available on the distribution of different subtypes of ICCs in HD. The aim of this study was to determine the alterations in density of different subtypes of ICC in colonic specimens of patients with total colonic and recto-sigmoid HD. Full thickness colonic specimens were obtained from five children with total colonic aganglionosis (TCA), sixteen with recto-sigmoid HD and seven controls. ICCs were visualized in frozen sections by c-Kit (CD117) fluorescent staining. In the control colon, c-Kit positive ICCs formed a dense network surrounding the myenteric plexus (IC-MY), along the submucosal surface of the circular muscle layer (IC-SM) and in the circular and longitudinal muscle layer (IC-IM). In the aganglionic region of the colon of the patients affected by HD, the number of ICCs (especially IC-IM and IC-SM) was markedly reduced and IC-MY networks were disrupted. Nearly total lack of three subtypes of ICCs was observed in the TCA specimens. This study demonstrated the altered distribution of different subtypes of ICCs in the resected colon of patients with recto-sigmoid HD and TCA. These findings suggest that the reduction of each subtype of ICCs may play an important role in the etiology of HD.

An age-dependent proliferation is involved in the postnatal development of interstitial cells of Cajal in the small intestine of mice

This paper aimed at investigating the alterations in interstitial cells of Cajal (ICCs) in the murine small intestine from 0-day to 56-day post-partum (P0-P56) by immunohistochemistry. The Kit+ ICCs, which were situated around myenteric nerve plexus (ICC-MY) formed a loose cellular network at P0 which changed into an intact one before P32. The density of ICC-MY increased from P0 to P12, and then decreased until P32. In contrast, the estimated total amount increased more than 15-fold at P32 than that at P0. Some Kit+/BrdU+ cells were observed at 24 h after one BrdU injection to the different-aged mice, and the number decreased from P2 to P24 and vanished at P32. Actually a few Kit+/BrdU+ cells can be observed at 1 h after one BrdU injection at P10, and the amount doubled at 24 h along with paired Kit+/BrdU+ cells. A number of BrdU+ ICCs were also labeled with CD34, CD44 and insulin-like growth factor I receptor. About 65% ICCs were BrdU+ at P32 after daily BrdU injection from P0. Our results indicate that an age-dependent proliferation is involved in the postnatal development of ICC-MY which increase greatly in cell numbers and proliferative ICCs may originate from ICCs progenitor cells.

Phenotypic alteration of interstitial cells of Cajal in idiopathic sigmoid megacolon

BACKGROUND

Interstitial cells of Cajal (ICCs) are detected as a pacemaker of gastrointestinal movement and express c-kit and CD34. Recently, ICCs have implicated pathogenesis in several human diseases presenting gastrointestinal motor dysfunction. This study was performed to clarify the role of ICCs in idiopathic sigmoid megacolon using histological and immunohistochemical examinations.

METHODS

Four adult patients with idiopathic sigmoid megacolon and 11 controls were studied. Histology and immunocytochemistry using NSE, S100, c-kit, and CD34 were performed in conjunction with quantitative analysis using the public domain NIH image program.

RESULTS

Little histological change in neuromuscular structures in megacolon was observed. Immunohistochemistry demonstrated remarkable decrease of c-kit expressing ICCs without reduction of CD34 expression in the similar interstitial cell population. This observation was further supported by quantitative assessment using public domain NIH image program.

CONCLUSIONS

A specific downregulation of c-kit in ICCs may be a cause of idiopathic sigmoid megacolon in adults.

C-kit receptor in the human vas deferens: distinction of mast cells, interstitial cells and interepithelial cells

The molecular mechanisms underlying the regulation of vas deferens (VD) motility and semen emission are still poorly understood. Interstitial cells of Cajal (ICC), which harbour the c-kit receptor (CD117), provide the basis of coordinated gut motility. We investigated whether c-kit receptor-positive cells also exist in the normal human VD. Enzyme and fluorescence immunohistochemical techniques were applied on serial sections of human proximal, middle, and distal VD segments (n=49) employing 13 different monoclonal and polyclonal antibodies recognizing the c-kit receptor. The c-kit receptor was detected in either round- or spindle-shaped cells. On account of their antigenic profile, the round- and oval-shaped c-kit receptor-positive cells were identified as mast cells (MC) occurring in all layers of the VD except the epithelium. In contrast, two distinct populations of exclusively c-kit receptor-positive spindle-shaped cells were found within the lamina propria and, rarely, in the inner and outer smooth muscle layers, as well as within the epithelium. Different shaped c-kit receptor-positive MC and IC were present in all layers of the human VD. Our findings demonstrate the presence of different c-kit receptor-positive cells also in the human VD. Their rather ubiquitous distribution within the lamina propria and muscle layers suggests that IC and MC may modulate the neuromuscular transmission and the propagation of electrical signals in multiple systems involved in the draining of fluids. The importance of the c-kit receptor-positive interepithelial cells remains unclear.

C-Kit receptor (CD117) in the porcine urinary tract

C-Kit positive interstitial cells of Cajal (ICC) play an important role in the regulation of the smooth muscle motility, acting as internal pacemakers to provide the slow wave activity within various luminal organs. Recently c-Kit-(CD117)-positive interstitial cells (IC) have been shown in the genitourinary tract, but systematic studies on the distribution and density of IC within the urinary tract are still lacking. Therefore the aim of the present study was to analyze systematically the localization and distribution of the c-Kit receptor in the urinary tract of the pig using immunohistochemical and molecular methods. Tissue samples were harvested from the porcine urinary tract including renal calices and pelvis, ureteropelvic junction, proximal, middle and distal ureter, ureteral orifice, fundus, and corpus of the bladder and the internal urethral orifice. Small and large intestine specimen served as controls. Immunohistochemistry (APAAP, IF) was applied on serial frozen sections using four monoclonal and polyclonal antibodies recognizing CD117. Whole mounts of the porcine upper urinary tract were prepared and investigated using conventional and confocal fluorescence microscopy followed by three-dimensional reconstruction. UV-laser microdissection and RT-PCR were applied to confirm the immunohistochemical results. CD117-immunoreactivity labeled bipolar IC and round-shaped mast cells (MC) throughout the adventitia, tunica muscularis and submucosa within the whole porcine urinary tract. While MC were found continuously in all investigated segments, a gradient of bipolar IC was evident. The whole mount preparations gave a detailed cytomorphology of IC within the various layers of the porcine urinary tract. Whole mount preparations revealed closed apposition of bi- and tripolar c-Kit positive IC parallel to the smooth muscle bundles and to veins of the tunica muscularis and adventitia. In the urothelium single CD117-positive interepithelial cells were found. The highest density of CD117-positive cells was found at the ureteropelvic junction, however the differences in between the segments were minimal. Microdissection and RT-PCR confirmed the results uncovered by immunohistochemistry. The ubiquitous distribution of IC and their close relationship to smooth muscle provides strong evidence that IC could contribute to the intrinsic pacemaker activity within the porcine (upper and lower) urinary tract. The role of the interepithelial CD117-positive cells as mechanosensors or as a precursor cell in the regeneration of the urothelium, is conceivable.

Interstitial cells of Cajal in the normal gut and in intestinal motility disorders of childhood

Interstitial cells of Cajal (ICCs) are pacemaker cells which are densely distributed throughout the whole gastrointestinal tract. ICCs have important functions in neurotransmission, generation of slow waves and regulation of mechanical activities in the gastrointestinal tract, especially for the coordinated gastrointestinal peristalsis. Therefore, a loss of ICCs could result in gastrointestinal motor dysfunction. In recent years c-kit labeling has been widely used to study pathological changes of ICCs in gastrointestinal motility disorders. Paediatric gastrointestinal motility disorders such as hypertrophic pyloric stenosis, Hirschsprung's disease, total colonic aganglionosis, hypoganglionosis, intestinal neuronal dysplasia, internal anal sphincter achalasia, megacystis microcolon intestinal hypoperistalsis syndrome have been reported to be associated with loss or deficiency of ICCs networks. This review describes the distribution of ICCs in the normal gastrointestinal tract and its altered distribution in intestinal motility disorders of childhood.

Disorders of interstitial cells of Cajal

Interstitial cells of Cajal (ICCs) have, in the past 2 decades, been recognised as important elements in the regulation of gastrointestinal motility. Specifically, they have been shown to be critical for the generation and propagation of electrical slow waves that regulate the phasic contractile activity of gastrointestinal smooth muscle, and for mediating neurotransmission from enteric motor neurons to smooth muscle cells. These different functional roles are carried out by different phenotypic classes of ICC that have discrete distributions within the tunica muscularis. Identifying the functional roles of ICC within the gut has been facilitated by studying mutant mice deficient in ICC, either as a consequence of loss of the tyrosine kinase receptor, Kit, or its ligand, stem cell factor, both of which are necessary for normal ICC development. In humans, under certain pathophysiological conditions, loss or defects in ICC networks appear to play a role in the generation of certain motility disorders. Alterations in ICC distribution have been reported in conditions such as achalasia, chronic intestinal pseudoobstruction, Hirschsprung disease, inflammatory bowel diseases, and slow transit constipation. Molecular and genetic techniques are helping researchers to determine whether defects in ICC networks are the cause of motility disorders, or whether the disrupted ICC networks are a consequence of gut dysfunction.

Interstitial cells of Cajal in health and disease. Part I: normal ICC structure and function with associated motility disorders

Ramon y Cajal (1852-1934) is considered to be one of the founders of the field of neuroscience. In 1911, he described interstitial neurons in the gut, noting that they were primitive accessory components that perhaps modify smooth muscle contraction, themselves subject to regulation from principle neurons. The accuracy of his description of their appearance and activities has led to these cells now being called the interstitial cells of Cajal (ICC). Thuneberg and Faussone-Pellegrini were instrumental in bringing these cells to the attention of gastroenterologists and pathologists in the early 1980s. Subsequently, the development of antibodies to c-kit has allowed routine identification of the ICC in pathology specimens. c-Kit is a transmembrane protein kinase which has as ligand stem cell factor and is involved in cell development in a variety of cell lineages. In the gut musculature, ICC and mast cells are the only cells that have prominent c-kit expression. The ICC are now known to play an important role in gut motility and absent or disordered ICC networks have been identified in a variety of motility disorders.

Morphology of the interstitial cells of Cajal of the human ileum from foetal to neonatal life

The so-called interstitial cells of Cajal myenteric plexus (ICC-MP), interstitial cells of Cajal intramuscular (ICC-IM) and interstitial cells of Cajal deep muscular plexus (ICC-DMP) are the three types of ICC endowed within the intestinal muscle coat where they play different roles in gut motility. Studies on ICC ontogenesis showed ICC-MP in the human ileum by 7-9 weeks while information on ICC-IM and ICC-DMP in foetuses and newborns are not exhaustive. Functional recordings in the fasting state of prematurely born babies aged 28-37 weeks showed immature ileal motility. To gain more information on the time of appearance of the three ICC types in the human ileum and on the steps of the acquisition of mature features, we studied by c-kit immuno-histochemistry foetuses aged 17-27 weeks and newborns aged 36-41 weeks. In parallel, the maturative steps of enteric plexuses and muscle layers were immunohistochemically examined by using anti-neuron specific enolase (NSE), anti-S-100 and anti-alpha smooth muscle actin (alphaSMA) antibodies. The appearance and differentiation of all the ICC types were seen to occur in concomitance with those of the related nerve plexuses and muscle layers. ICC-MP appeared first, ICC-IM and ICC-DMP later and their differentiation was incomplete at birth. In conclusion, the ICC-MP, the intestinal pacemaker cells, in spite of absence of food intake, are already present during the foetal life and the ICC-IM appear by pre-term life, thus ensuring neurotransmission. The ICC-DMP and their related nerve plexus and smooth muscle cells, i.e. the intestinal stretch receptor, begin to differentiate at birth. These findings might help in predicting neonatal ileal motor behaviour and in interpreting the role of ICC abnormalities in the pathophysiology of intestinal motile disorders of neonates and young children.

Idiopathic megacolon

This leading article refers to the paper by Meier-Ruge WA, Muller-Lobeck H, Stoss F, Bruder E. The pathogenesis of idiopathic megacolon. Eur J Gastroenterol Hepatol 2006; 18:1209-1215. We apologise to all concerned for the dissociation between the two papers, which was due to an administrative error. The pathogenesis of idiopathic megacolon is still unclear. Besides abnormalities of the enteric nervous system, alterations in the function of intestinal smooth muscle cells and connective tissue elements might play an important role. A permanent extension of the bowel diameter without concrete hints to its aetiology is termed idiopathic megacolon. Evidence exists that idiopathic megacolon comprises a heterogeneous group of conditions characterized by alterations of the enteric nervous system, smooth muscle cells and/or connective tissue. Innovative molecular techniques are needed to get further insights into the pathogenesis of these intestinal motility disorders.

Loss of interstitial cells of Cajal network in severe idiopathic gastroparesis

AIM

To report a case of severe idiopathic gastroparesis in complete absence of Kit-positive gastric interstitial cells of Cajal (ICC).

METHODS

Gastric tissue from a patient with severe idiopathic gastroparesis unresponsive to medical treatment and requiring surgery was analyzed by conventional histology and immunohistochemistry.

RESULTS

Gastric pacemaker cells expressing Kit receptor had completely disappeared while the local level of stem cell factor, the essential ligand for its development and maintenance, was increased. No signs of cell death were observed in the pacemaker region.

CONCLUSION

These results are consistent with the hypothesis that a lack of Kit expression may lead to impaired functioning of ICC. Total gastrectomy proves to be curative.

Interstitial cells of Cajal could regenerate and restore their normal distribution after disrupted by intestinal transection and anastomosis in the adult guinea pigs

Surgical manipulations of the gastrointestinal (GI) tract usually lead to loss of interstitial cells of Cajal (ICCs). The present study prepared to investigate whether ICCs can regenerate and restore their normal distribution up to 5 months after semitransection and end-to-end anastomosis of small intestines of adult guinea pigs. The segments of anastomosis were studied by immunohistochemistry with anti-KIT, 5-bromo-2'-deoxyuridine (BrdU), stem cell factor (SCF), and neurofilament 200 antibodies and also by transmission electron microscopy (TEM). At early stage, intestinal surgery led to intestinal wall impairment and ICCs loss, and ICCs near the site of anastomosis gradually increased in numbers. About 150 days postoperation, the distribution of ICCs and the microstructure of intestinal wall appeared to be similar with those of the control. By double immunostaining with BrdU and KIT antibodies, a number of proliferated ICCs were seen near the site of transection/anastomosis. Furthermore, KIT ligand, SCF, was mainly observed in the smooth muscle cells (SMCs), which are located close to ICCs. TEM observation revealed a number of immature and mature ICCs in this region. Our results indicated that ICCs could regenerate and restore their normal distribution after intestinal surgery and SMCs might be involved in the regenerated events of ICCs in the adult guinea pig GI tract.

Interstitial cells of Cajal, enteric nerves, and glial cells in colonic diverticular disease

BACKGROUND

Colonic diverticular disease (diverticulosis) is a common disorder in Western countries. Although its pathogenesis is probably multifactorial, motor abnormalities of the large bowel are thought to play an important role. However, little is known about the basic mechanism that may underlie abnormal colon motility in diverticulosis.

AIMS

To investigate the interstitial cells of Cajal (the gut pacemaker cells), together with myenteric and submucosal ganglion and glial cells, in patients with diverticulosis.

PATIENTS

Full thickness colonic samples were obtained from 39 patients undergoing surgery for diverticulosis. Specimens from tumour free areas of the colon in 10 age matched subjects undergoing surgery for colorectal cancer served as controls.

METHODS

Interstitial cells of Cajal were assessed using anti-Kit antibodies; submucosal and myenteric plexus neurones and glial cells were assessed by means of anti-PGP 9.5 and anti-S-100 monoclonal antibodies, respectively.

RESULTS

Patients with diverticulosis had normal numbers of myenteric and submucosal plexus neurones compared with controls (p = 0.103 and p = 0.516, respectively). All subtypes of interstitial cells of Cajal were significantly (p = 0.0003) reduced compared with controls, as were glial cells (p = 0.0041).

CONCLUSIONS

Interstitial cells of Cajal and glial cells are decreased in colonic diverticular disease, whereas enteric neurones appear to be normally represented. This finding might explain some of the large bowel motor abnormalities reported to occur in this condition.

Decreased density of interstitial cells of Cajal and neuronal cells in patients with slow-transit constipation and acquired megacolon

BACKGROUND

The pathophysiology of constipation is not clearly identified as yet, and the interstital cells of Cajal (ICC), known to generate the slow wave activity and to be involved in intestinal neurotransmission and the enteric nervous system (ENS), are suspected to play an important role. The aims of the present study were to assess the distribution of ICC and neuronal cells of ENS in patients with slow-transit constipation and acquired megacolon.

METHODS

Sigmoid colon specimens were obtained from patients who underwent colectomy due to slow-transit constipation (n = 10), acquired megacolon (n = 9) and non-obstructive colon cancer (n = 10) as a control group. The ICC were visualized by c-Kit immunohistochemistry and neuronal cells of the ENS were demonstrated by protein gene product (PGP) 9.5. Density of cells stained by c-Kit and PGP 9.5 was calculated as percent area (area stained/area of X-Y plane) x 100, when images were collected at a magnification of x40 objective, with maximum area examined in the horizontal X-Y plane of 400 microm x 400 microm using an image analyzer.

RESULTS

The densities of ICC and PGP 9.5 reactive neuronal structures were significantly decreased in all layers of sigmoid colon specimens in patients with slow-transit constipation and acquired megacolon, compared with that of the control group. However, there was no statistically significant difference in either the density of ICC or that of neuronal structures between the patients with slow-transit constipation and acquired megacolon.

CONCLUSIONS

Slow-transit constipation and acquired megacolon were associated with alteration of ICC and neuronal cells of ENS in the sigmoid colon.

Cajal-like cells in the upper urinary tract: comparative study in various species

The interstitial cells of Cajal (ICC) play an important role in the control of gut motility. The recognition that the ICC cell membrane harbors the c-kit receptor (CD117) sparked rapid advancement in ICC research on the gut and certain pathologies using immunochemical and molecular methods. The question arises whether ICC exist in the upper urinary tract (UUT) and trigger motility. The present study analyzed the distribution of the c-kit receptor in the normal human UUT compared with various species. Immunohistochemistry (alkaline-phosphatase-anti-alkaline-phosphatase technique, immunofluorescence) was applied on serial sections using monoclonal and polyclonal antibodies recognizing the c-kit receptor. C-kit staining was compared with standard endothelial, epithelial, neurogenic, histiocytic, mast cell, and smooth muscle markers, as well as a negative control. Normal proximal, middle, and distal ureter segments were analyzed in rodents, carnivores, porcines, cow, and humans. In all species the c-kit receptor was detected in either round or spindle-shaped cells. Because of their antigenic profile, the round cells were identified as mast cells occurring in all layers of the ureteral wall except the urothelium and were more frequent in humans. In contrast, the population of spindle-shaped cells was marked only by anti-c-kit receptor antibodies, thus resembling ICC. These ICC-like cells were found among the inner and outer smooth muscle layers and in the lamina propria of all species. In humans, spindle-shaped cells were also found vertically oriented within the urothelium. Our morphological data present for the first time the distribution of ICC in the UUT of various species. The ubiquitous distribution in the entire pyeloureteral complex provides strong evidence that ICC generate electrical pacemaker activity within the UUT as an intrinsic system. Animal studies may help to understand the physiological importance of these ICC-like cells. The significance of these findings needs to be evaluated by functional studies and investigations of certain congenital pathologies with disturbance of the urinary outflow.

Basic fibroblast growth factor, neurofilament, and glial fibrillary acidic protein immunoreactivities in the myenteric plexus of the rat esophagus and colon

The enteric nervous system consists of a number of interconnected networks of neuronal cell bodies and fibers as well as satellite cells, the enteric glia. Basic fibroblast growth factor (bFGF) is a mitogen for a variety of mesodermal and neuroectodermal-derived cells and its presence has been described in many tissues. The present work employs immunohistochemistry to analyze neurons and glial cells in the esophageal and colic enteric plexus of the Wistar rat for neurofilament (NF) and glial fibrillary acidic proteins (GFAP) immunoreactivity as well as bFGF immunoreactivity in these cells. Rats were processed for immunohistochemistry; the distal esophagus and colon were opened and their myenteric plexuses were processed as whole-mount preparations. The membranes were immunostained for visualization of NF, GFAP, and bFGF. NF immunoreactivity was seen in neuronal cell bodies of esophageal and colic enteric ganglia. GFAP-immunoreactive enteric glial cells and processes were present in the esophageal and colic enteric plexuses surrounding neuronal cell bodies and axons. A dense net of GFAP-immunoreactive processes was seen in the ganglia and connecting strands of the myenteric plexus. bFGF immunoreactivity was observed in the cytoplasm of the majority of the neurons in the enteric ganglia of esophagus and colon. The two-color immunoperoxidase and immunofluorescence methods revealed bFGF immunoreactivity also in the nucleus of GFAP-positive enteric glial cells. The results suggest that immunohistochemical localization of NF and GFAP may be an important tool in the study of the plasticity in the enteric nervous system. The presence of bFGF in neurons and glia of the myenteric plexus of the esophagus and the colon indicates that this neurotrophic factor may exert autocrine and paracrine actions in the enteric nervous system.

Accelerated intestinal transit in inbred mice with an increased number of interstitial cells of Cajal

The interstitial cells of Cajal (ICC) play an important role in coordinating intestinal motility, and structural alterations in ICC are found in several human digestive diseases. Mouse models with defects in ICC allow a better understanding of their functions. We investigated the pattern of intestinal motility and the distribution of ICC in the PRM/Alf inbred mouse strain, characterized by a selective intestinal lengthening. In PRM/Alf mice, the digestive transit time, evaluated by using thermophilic Bacillus subtilis spores, was normal, indicating accelerated transit. The contractility and slow-wave frequency, recorded on isolated segments from the proximal small intestine, were significantly increased. The number of ICC was also significantly higher along the small intestine and the colon. The concomitant increase of the contractility, the slow-wave frequency, and the number of ICC is consistent with the proposal of a role of ICC number increase in the higher intestinal transit speed. The PRM/Alf model should be useful to further investigate the roles of ICC in the control of digestive motility.

Gastroschisis in the rat model is associated with a delayed maturation of intestinal pacemaker cells and smooth muscle cells

BACKGROUND

A pacemaker system is required for peristalsis generation. The interstitial cells of Cajal (ICC) are considered the intestinal pacemaker, and are identified by expression of the c-kit gene--encoded protein. Gastroschisis is characterized by a severe gastrointestinal dysmotility in newborns. In spite of this clinical picture, few studies have focused on smooth muscle cells (SMC) morphology and none on ICC. Therefore, their morphology has been studied in fetuses at term in the rat model of gastroschisis.

METHODS

At 18.5 day's gestation (E18.5), 10 rat fetuses were killed, 10 underwent surgical creation of gastroschisis, and 10 underwent manipulation only. The small intestine of the latter 2 groups was harvested at E21.5. Specimens were processed for H&E, c-kit and actin (alpha smooth muscle antibody [alpha-SMA]) immunohistochemistry, and transmission electron microscopy (TEM).

RESULTS

In the controls, SMC were c-kit+ and alpha-SMA+, with labeling intensity increasing by age. At E21.5, some cells around the Auerbach's plexus were more intensely c-kit+, and differentiating ICC were seen under TEM at this level. Gastroschisis fetuses had no c-kit+ cells referable to ICC. In the more damaged loops, SMC were very faintly c-kit+ and alpha-SMA+. Under TEM, there were few differentiated SMC and no presumptive ICC. In the less-damaged loops, SMC were faintly c-kit+ and alpha-SMA+ and had ultrastructural features intermediate between those of E18.5 and E21.5 controls; ICC were very immature.

CONCLUSIONS

ICC and SMC differentiation is delayed in gastroschisis with the most damaged loops showing the most incomplete picture. These findings might help in understanding the delayed onset of peristalsis and the variable time-course of the recover seen in babies affected by gastroschisis.

Cajal-like cells in the human upper urinary tract

PURPOSE

Interstitial cells of Cajal (ICCs) have an important role in the regulation of gut motility as they are responsible for the slow wave activity of smooth muscle. It is still unknown if ICCs also occur in the human upper urinary tract. Since these cells express and are marked by the c-kit receptor CD117, we investigated its occurrence and distribution along the human upper urinary tract.

MATERIALS AND METHODS

Tissues from 56 human ureters, spanning proximal, middle and distal ureter segments, were analyzed by indirect immunohistochemistry using the alkaline phosphatase-anti-alkaline phosphatase method and double labeling immunofluorescence on consecutive tissue sections. Several monoclonal and polyclonal antibodies to c-kit receptor were used in combination with various cell markers for histiocytic, mast cell, endothelial, epithelial, neuronal, smooth muscle and stem cell differentiation.

RESULTS

The c-kit receptor was found in 3 cell types of the ureter and in round or spindle-shaped cells. Due to their antigenic profile the first one was revealed as mast cells occurring in all layers of the ureteral wall except the urothelium. In contrast, the population of spindle-shaped cells was only marked by c-kit receptor, thus, resembling ICCs. These ICC-like cells were found among the inner and outer smooth muscle layers, and in the lamina propria. They showed a slight decrease from proximal to distal ureteral segments. However, unlike intestinal ICCs their cytomorphology differed and some cells, representing the third group of c-kit receptor positive cells, were found within the urothelium.

CONCLUSIONS

Our data demonstrate the presence of ICC-like cells and their ubiquitous distribution in the human ureter. The physiological importance and pathological significance of these findings must be evaluated by functional studies and investigations of certain pathological with urinary outflow disturbance conditions.

Changes of interstitial cell of Cajal content in a rat model of electrogastric dysrhythmias

AIM: To observe the change of the interstitial cells of Cajal (ICC) content in the stomach wall in rats with electrogastric dysrhythmias, and to discuss the pathological mechanism of the rat model.

METHODS: Irregular feeding was adopted to establish a rat model of electrogastric dysrhythmias. Immunohistochemical staining was used to detect the content of c-kit positive ICC.

RESULTS: The content of ICC in the model group was higher than that in the control group, and showed a significant difference from that in the control group (P <0.001).

CONCLUSION: The increase of the ICC content in the model group may lead to the increase of the abnormal pacing impulse points, which results in the electrogastric dysrhythmias in the stomach.

[Drug-induced anomalous contraction of gastrointestinal tract of mice with impaired c-kit function]

Drug-induced contraction of gastrointestinal tracts seems to depend upon the extent of their rhythmic contraction that is driven by the activity of gastrointestinal pacemaker cells. In BALB/c mice chronically administrated with a neutralizing anti-c-Kit monoclonal antibody (ACK2), rhythmic contraction of the gastrointestinal tract was impaired and contractile responses to drugs, including acetylcholine, prostaglandin F(2alpha), and bradykinin, were anomalously augmented. Histochemical analysis of the c-kit-positive cells in the gastrointestinal tract revealed the decreased number of c-kit-positive cells in the ACK2-treated animals, which lead to the impaired rhythmic contraction. Since the intestinal c-kit-positive cells in primary culture developed Ca(2+)-dependent rhythmic Cl(-) current, the rhythmic current is supposed to be an origin of gastrointestinal pacemakers. The extent of anomaly in drug-induced contraction correlated with the extent of impairment in rhythmic contraction. The drug-induced anomalous contraction in the preparation from ACK2-treated animals, which is accompanied by the impaired rhythmic contraction, was mimicked when the gastrointestinal segments from control animals were superfused with a low temperature organ bath solution at 25 degrees C. These results suggest that rhythmic discharge of excitation of smooth muscle cells, which is triggered by rhythmic excitatory input from c-kit cells, regulates the extent of drug-induced contraction.

Interstitial cells of Cajal are normally distributed in both ganglionated and aganglionic bowel in Hirschsprung's disease

Surgery for Hirschsprung's disease is often complicated by post-operative bowel motility disorders. The impact of intestinal neural histology on the surgical outcome has been previously studied, but no information is available concerning the influence of the distribution of interstitial cells of Cajal (ICC) on these complications. These cells are considered to be pacemakers in the gastrointestinal tract. The aim of this study was to assess the distribution of ICC in the proximal segment of resected bowel in Hirschsprung's disease and confront these results with the clinical outcome. Using immunohistochemistry for light microscopy, we compared the pattern of distribution of ICC in the proximal segment of resected bowel in Hirschsprung's disease with that in normal colon. We correlated these results with the corresponding neural intestinal histology determined by CD56 and the protein gene product 9.5 immunohistochemistry. The distribution of ICC in the proximal segment of resected bowel is identical to that of normal colon, regardless of normal or abnormal colon innervation. ICC distribution does not seem to contribute to post-operative bowel motility disorders in patients operated for Hirschsprung's disease