Involvement of endogenous nitric oxide and c-kit-expressing cells in chronic intestinal pseudo-obstruction

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.

Intestinal pseudo-obstruction caused byGiardia lambliainfection

A woman in her 40s presented with malaise, nausea, reduced appetite, abdominal distention, loose stools and weight loss. Symptoms had started 6 months earlier and worsened in the last 2 weeks. CT enterography showed hypotonic dilated small bowel loops in absence of any mechanical obstruction. Endoscopic examinations including capsule endoscopy did not reveal any obstructing lesion, but a delayed small bowel transit time of the capsule. Duodenal histology revealed Marsh 3a villous atrophy. Secondary causes of intestinal pseudo-obstruction and villous atrophy were investigated.Giardia lambliatrophozoites were found in the stools and in the duodenal biopsies. The patient’s symptoms quickly resolved after metronidazole treatment with complete normalisation of duodenal histology.

Paediatric intestinal pseudo-obstruction: a scoping review

Paediatric intestinal pseudo-obstruction (PIPO) encompasses a group of rare disorders in which patients present with the clinical features of bowel obstruction in the absence of mechanical occlusion. The management of PIPO presents a challenge as evidence remains limited on available medical and surgical therapy. Parenteral nutrition is often the mainstay of therapy. Long-term therapy may culminate in life-threatening complications including intestinal failure-related liver disease, central line thrombosis and sepsis. Intestinal transplantation remains the only definitive cure in PIPO but is a complex and resource-limited solution associated with its own morbidity and mortality. We conducted a scoping review to present a contemporary summary of the epidemiology, aetiology, pathophysiology, diagnosis, management and complications of PIPO.Conclusion: PIPO represents a rare disorder that is difficult to diagnose and challenging to treat, with significant morbitity and mortality. The only known cure is intestinal transplantation. What is Known: • Paediatric intestinal pseudo-obstruction is a rare, heterogeneous disorder that confers a high rate of morbidity and mortality • Complications of paediatric intestinal pseudo-obstruction include chronic pain, small intestine bacterial overgrowth and malrotation. Other complications can occur related to its management, such as line infections with parenteral nutrition or cardiac side effects of prokinetic medications What is New: • Progress in medical and surgical therapy in recent years has led to improved patient outcomes • Enteral autonomy has been reported in most patients at as early as 1 month post-transplantation.

Bowel dysfunction following pullthrough surgery is associated with an overabundance of nitrergic neurons in Hirschsprung disease

PURPOSE

Recent evidence suggests that patients with Hirschsprung disease (HD) have abnormal neurotransmitter expression in the ganglionated proximal colon. These alterations may cause persistent bowel dysfunction even after pullthrough surgery. We sought to quantify the proportion of nitrergic neurons in the ganglionic colon of HD patients and relate these findings to functional outcome.

METHODS

The proximal resection margin from 17 patients with colonic HD who underwent a pullthrough procedure and colorectal tissue from 4 age-matched controls were immunohistochemically examined to quantify the proportion of nitrergic neurons. The incidence of constipation, incontinence, and enterocolitis in HD patients was assessed retrospectively and correlated with the proportion of nitric oxide synthase (NOS) expressing neurons. Neuronal subtypes in the ganglionic colon of the Edrnb^-/- mouse model of HD were also studied.

RESULTS

Mice with HD had a significantly higher proportion of NOS+ neurons in ganglionic colon than normal littermates (32.0±5.6% vs. 19.8±1.2%, p<0.01). Patients with HD also had significantly more NOS+ neurons than controls (18.4±4.6% vs. 13.1±1.9%, p<0.01). Patients who experienced constipation or enterocolitis postoperatively tended toward a higher proportion of NOS+ neurons (21.4±3.9% vs. 17.1±4.1%, p=0.06). Furthermore, patients with a proportion of NOS+ neurons above the median of all HD patients (18.3%) were significantly more likely to have constipation than those below the median (75% vs. 14%, p<0.05).

CONCLUSION

An overabundance of nitrergic neurons in the proximal resection margin is associated with HD and may predict bowel dysfunction following pullthrough surgery.

Interdependency between mechanical parameters and afferent nerve discharge in hypertrophic intestine of rats

Partial intestinal obstruction causes smooth muscle hypertrophy, enteric neuronal plasticity, motility disorders, and biomechanical remodeling. In this study we characterized the stimulus-response function of afferent fibers innervating the partially obstructed jejunum. A key question is whether changes in afferent firing arise from remodeled mechanical tissue properties or from adaptive afferent processes. Partial obstruction was created by placing a polyethylene ring for 2 wk in jejunum of seven rats. Sham obstruction was made in six rats and seven rats served as normal controls. Firing from mesenteric afferent nerve bundles was recorded during mechanical ramp, relaxation, and creep tests. Stress-strain, spike rate increase ratio (SRIR), and firing rate in single units were assessed for evaluation of interdependency of the mechanical stimulations, histomorphometry data, and afferent nerve discharge. Partial intestinal obstruction resulted in hypertrophy and jejunal stiffening proximal to the obstruction site. Low SRIR at low strains during fast distension and at high stresses during slow distension was found in the obstructed rats. Single unit analysis showed increased proportion of mechanosensitive units but absent high-threshold (HT) units during slow stimulation, decreased number of HT units during fast stimulation, and shift from HT sensitivity towards low threshold sensitivity in the obstructed jejunum. Biomechanical remodeling and altered afferent response to mechanical stimulations were found in the obstructed jejunum. Afferents from obstructed jejunum preserved their function in encoding ongoing mechanical stimulation but showed changes in their responsiveness. The findings support that mechanical factors rather than adaption are important for afferent remodeling.

Epithelial inducible nitric oxide synthase causes bacterial translocation by impairment of enterocytic tight junctions via intracellular signals of Rho-associated kinase and protein kinase C zeta

OBJECTIVE

Gut barrier dysfunction and bacterial translocation occur in various disorders, including intestinal obstruction. Overexpression of inducible nitric oxide synthase is implicated in the pathogenesis of bacterial translocation, of which the molecular mechanism remains unclear. Epithelial permeability is regulated by tight junction reorganization and myosin light chain phosphorylation. Our aim was to investigate the roles of Rho-associated kinase and protein kinase C ζ in epithelial nitric oxide synthase-mediated barrier damage.

DESIGN

Animal study and cell cultures.

SETTING

Research laboratory.

SUBJECTS

BALB/c mice.

INTERVENTIONS

: Mouse distal small intestine was obstructed in vivo by a 10-cm loop ligation in which vehicle, L-Nil (a nitric oxide synthase inhibitor), or Y27632 (a Rho-associated kinase inhibitor) was luminally administered. After obstruction for 24 hrs, intestinal tissues were mounted on Ussing chambers for macromolecular flux. Liver and spleen tissues were assessed for bacterial counts. Caco-2 cells were exposed to 1 mM S-nitroso-N-acetylpenicillamine (a nitric oxide donor) for 24 hrs, and transepithelial resistance and permeability were evaluated.

MEASUREMENTS AND MAIN RESULTS

Mice with intestinal obstruction displayed epithelial barrier dysfunctions, such as permeability rise and bacterial translocation, associated with tight junction disruption and myosin light chain phosphorylation. Increased inducible nitric oxide synthase and phosphorylated protein kinase C ζ were observed in villus epithelium. Enteric instillation of L-Nil and Y27632 attenuated the functional and structural barrier damage caused by intestinal obstruction. L-Nil decreased intestinal obstruction-induced myosin light chain, myosin phosphatase target subunit 1, and protein kinase C ζ phosphorylation, suggesting that inducible nitric oxide synthase is upstream of Rho-associated kinase and protein kinase C ζ signaling. The intestinal phosphorylated myosin light chain level did not increase in inducible nitric oxide synthase(-/-) mice following intestinal obstruction. In vitro studies showed that S-nitroso-N-acetylpenicillamine-induced transepithelial resistance drop and permeability rise was independent of cell apoptosis. Y27632 inhibited S-nitroso-N-acetylpenicillamine-induced myosin light chain phosphorylation and permeability rise. S-nitroso-N-acetylpenicillamine also triggered phosphorylation and membrane translocation of protein kinase C ζ. Inhibitory protein kinase C ζ pseudosubstrate blocked S-nitroso-N-acetylpenicillamine-induced tight junction reorganization, but not myosin light chain phosphorylation.

CONCLUSIONS

Epithelial inducible nitric oxide synthase activates two distinct signals, protein kinase C ζ and Rho-associated kinase, to disrupt tight junctions leading to bacterial influx.

Chronic alcohol consumption affects gastrointestinal motility and reduces the proportion of neuronal NOS-immunoreactive myenteric neurons in the murine jejunum

Alcohol consumption interferes with gastrointestinal transit causing symptoms in alcoholic patients. Nitric oxide (NO), synthesized by neuronal nitric oxide synthase (nNOS) plays an important role in the control of gastrointestinal motility. Our aim was to investigate whether chronic alcohol intake in a murine model induces gastrointestinal motility disturbances and affects the nitrergic myenteric neurons in the stomach and jejunum. Gastric emptying, small intestinal transit and geometric centre were measured in vivo after intragastric gavage of Evans blue. Nitrergic relaxations to electrical field stimulation (EFS) and exogenous NO were recorded in jejunal muscle strips in vitro. The proportion of nNOS-immunopositive myenteric neurons was assessed using PGP9.5 and nNOS immunostaining. After chronic alcohol consumption, gastric emptying and small intestinal transit were delayed compared with control mice, and the nitrergic nerve-mediated relaxations to EFS in the jejunum were decreased, whereas relaxations to exogenous NO did not differ. The proportion of nNOS-immunoreactive neurons did not change in the stomach, whereas in the jejunum the percentage decreased from 33% to 27% (P < 0.001) after chronic alcohol intake. The total number of myenteric neurons remained unchanged. These results suggest that chronic alcohol consumption disturbs gastric and small intestinal motility in vivo and in vitro and is associated with a decrease in the proportion of nNOS-immunoreactive myenteric neurons in the murine jejunum.

Spatial pattern analysis of nitrergic neurons in the myenteric plexus of the duodenum of different mammalian species

Nitrergic myenteric neurons are especially susceptible to the development of neuropathy in functional gastrointestinal disorders. Investigations of the similarities and dissimilarities in the organization of nitrergic neurons in the various mammalian species are therefore important in an effort to determine the extent to which the results obtained in different animal models can be generalized. In the present work, the density and the spatial organization of the nitrergic neurons in the myenteric plexus of the duodenum were investigated in 7 mammalian species. After nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry, the Plexus Pattern Analysis software (PPAs) was applied to count the nuclei of nitrergic neurons, calculate the proportions of the areas covered by the plexus and perform randomization analysis. All 7 species exhibited a large population of nitrergic myenteric neurons, with densities in the range 12-56 cells/mm 2 . The distribution patterns of these neurons differed markedly in the different species, however, the rat was the only species in which the nitrergic neurons appeared to be randomly distributed. The PPAs in conjunction with NADPH-d histochemistry proved to be a simple and fast tool with which to reveal similarities and dissimilarities in the spatial arrangement of the nitrergic neurons in the different species.

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.

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.

Differential responses of VIPergic and nitrergic neurons in paediatric patients with Crohn's disease

Inflammatory bowel disease is a recurrent intestinal inflammatory disorder that in adults has been associated with changes in enteric nervous system neuropeptide expression. The aim of the present study was to determine whether similar changes were observed in paediatric Crohn's disease. The distribution of vasoactive intestinal peptide (VIP) and neuronal nitric oxide synthase (nNOS) was determined in colonic tissues from children with ileo-colonic (n=4) and colonic (n=3) Crohn's disease. The submucosal plexus of inflamed regions showed significant increase in density of VIP immunoreactive neurons (margin, 48% vs. inflamed tissue, 82% of HuC/D positive neurons). The density of submucosal plexus nNOS immunoreactive neurons was too low to be reliably quantified. Using the pan-neuronal marker HuC/D, no significant difference in numbers of HuC/D positive submucosal neurons was evident except where neurons were normalized to length of tissue (margins, 3.6+/-0.7 vs. inflamed tissue, 4.0+/-0.6 neurons/ganglia, p=0.33; margins, 2.7+/-0.4 vs. inflamed tissue, 5.7+/-1.2, neurons/mm, p=0.03). In the myenteric plexus, there was a significant increase in the percent of NOS neurons (38% vs. 82% of HuC/D positive neurons) while there was no significant difference in percent of VIP neurons (4% vs. 8%). No difference in number of HuC/D positive myenteric neurons among margin and inflamed tissues was observed (margin, 12.2+/-3.0 vs. inflamed tissue, 12.5+/-5.1 neurons/ganglia, p=0.50; margins 9.1+/-2.1 vs. inflamed tissue, 13.7+/-2.3 neurons/mm, p=0.11). These data demonstrate that inflammation is associated with a differential expression of VIP and nNOS neuronal subpopulations within the two major enteric plexi, likely due to phenotypic switch. Such changes might contribute to the pathogenesis of IBD and ongoing symptoms even in quiescent disease.

Chronic ethanol exposure impairs neuronal nitric oxide synthase in the rat intestine

BACKGROUND

Nitric oxide (NO), synthesized by neuronal (nNOS), endothelial (eNOS), and inducible (iNOS) nitric oxide synthases, plays an essential role in the physiological functions of the gastrointestinal (GI) tract. Chronic ethanol intake has been shown to interfere with several of these physiological functions, leading to the pathological alterations observed in alcoholic individuals. Our aim therefore was to investigate the effects of chronic ethanol consumption on NOS isoforms in different GI segments.

METHODS

Rats received either 20% aqueous ethanol solution or water for 8 weeks. Tissue samples of the duodenum, jejunum, ileum, and colon of the rats were used for measurement of the NOS activity, protein content, and nNOS immunohistochemistry. Anti-HuC/D immunohistochemistry was used to determine the total number of neurons.

RESULTS

Measurement of the physiological constitutive NOS (cNOS) activity revealed a 20 times higher activity in the colon than in the small intestine and after chronic ethanol treatment demonstrated a significant decrease in the jejunum, ileum, and colon, while in the duodenum it remained unchanged compared with the control group. The physiological iNOS activity was higher in the ileum and colon than in the duodenum and jejunum, and these levels were not significantly affected by ethanol. Neuronal nitric oxide synthase immunohistochemistry revealed a significant decrease in the numbers of immunostained cells in all investigated intestinal segments, while the total number of myenteric neurons remained constant. The nNOS protein content measured by Western blotting indicated a significant decrease in the colon after ethanol consumption, while in other intestinal segments change was not detectable.

CONCLUSIONS

This study has demonstrated for the first time that chronic ethanol consumption has a differential effect on NOS activity, NOS protein content, and the number of nitrergic neurons in different intestinal segments, suggesting that chronic ethanol administration affects the NO pathways in the enteric nervous system.

Effect of intravenous infusion of glyceryl trinitrate on gastric and small intestinal motor function in healthy humans

BACKGROUND

Glyceryl trinitrate is a donor of nitric oxide that relaxes smooth muscle cells of the gastrointestinal tract. Little is known about the effect of glyceryl trinitrate on gastric emptying and no data exist on the possible effect of glyceryl trinitrate on small intestinal transit.

AIM

To examine the effect of intravenous infusion of glyceryl trinitrate on gastric and small intestinal motor function after a meal in healthy humans.

METHODS

Nine healthy volunteers participated in a placebo-controlled, double-blind, crossover study. Each volunteer was examined during intravenous infusion of glyceryl trinitrate 1 microg/kg x min or saline. A gamma camera technique was used to measure gastric emptying and small intestinal transit after a 1600-kJ mixed liquid and solid meal. Furthermore, duodenal motility was assessed by manometry.

RESULTS

Glyceryl trinitrate did not change gastric mean emptying time, gastric half emptying time, gastric retention at 15 min or small intestinal mean transit time. Glyceryl trinitrate did not influence the frequency of duodenal contractions, the amplitude of duodenal contractions or the duodenal motility index.

CONCLUSIONS

Intravenous infusion of glyceryl trinitrate 1 microg/kg x min does not induce major changes in gastric or small intestinal motor function after a 1600-kJ meal in healthy volunteers.

Effects of Atractylodes macrocephalae on gastric emptying and nitrergic nerves in rats with hepatic cirrhosis

AIM: To observe the effects of atractylodes macrocephalae (AM) on gastric motility and nitrergic nerval system in rats with hepatic cirrhosis.

METHODS: Twenty-four Wister rats were randomly divided into control group, cirrhosis model group and AM treatment group. Dextran blue-2000 was used as an internal marker to assay the gastric emptying of the rats. The nitrergic nerves in the myenteric plexuses of gastric fundus, body and antrum were observed with NADPH-d histochemical staining.

RESULTS: Compared with those in control group, the gastric emptyings of rats were markedly delayed in model group (160.23±45.13 vs 100±17.78, P<0.01), and the distributions and densities of myenteric nitrergic nerves in the gastric body and antrum were significantly increased (7.35±0.95 vs 5.52±0.92, P<0.01; 6.26±0.79 vs 5.28±0.78, P<0.05). No significant changes were found in the fundus. After treatment with AM, the gastric motility of rats was markedly improved and the nitrergic nerves in antrum were significantly recovered. No significant differences were observed between the rats of AM and control group (96.12±16.25 vs 100±17.78, 5.39±0.84 vs 5.28±0.78, both P>0.05).

CONCLUSION: Atractylodes macrocephalae can improve the gastric motility and the mechanism may be related to its effect on the distributions of nitrigic nerves in the gastric body and antrum of rats with hepatic cirrhosis.

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.

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.

Diagnosis and treatment of chronic gastroparesis and chronic intestinal pseudo-obstruction

Chronic gastroparesis and CIP are debilitating disorders that are difficult to treat with currently available therapies. Failure of proper migration and differentiation of enteric neurons or ICC can result from specific genetic mutations and lead to phenotypes of CIP with or without concomitant gastroparesis. Intestinal dysfunction in diabetes may reflect a depletion of NO production (and perhaps other neurotransmitters or modulators), which is manifest as a syndrome of gastroparesis, diarrhea, or constipation in individual patients. As the key molecular changes underlying these disorders are defined, clinicians will begin to understand their precise etiology and rational medical therapy may become possible. In the future, testable hypotheses regarding the etiology of other functional bowel disorders (e.g., functional dyspepsia, irritable bowel syndrome, and so forth) may be developed.

Role of interstitial cells of Cajal in motility disorders of the bowel

OBJECTIVE

Idiopathic intestinal pseudo-obstruction is characterized by the failure of the intestinal tract to propel its contents appropriately. This leads to signs and symptoms of bowel obstruction and, in the absence of an associated systemic disorder or the administration of drugs known to result in bowel dysmotility, is termed chronic idiopathic intestinal pseudo-obstruction (CIIP). Histopathologically, patients with CIIP can be characterized as having either myopathic or neuropathic forms, but the large majority of patients do not show any specific histological changes. Interstitial cells of Cajal (ICC) have been shown to be the pacemaker cells of the bowel and have been implicated in the pathogenesis of CIIP. The aim of this study was to compare the number and distribution patterns of c-kit+ ICC in CIIP in patients with mechanical bowel obstruction, other bowel motility disorders, and normal controls.

METHODS

Six patients with CIIP, six age-matched normal controls, nine patients with mechanical bowel obstruction, and 18 patients with other motility disorders (non-CIIP), including 10 with secondary intestinal pseudo-obstruction, were studied. Toluidine blue, Masson's trichrome, and S-100 immunostaining were performed in all subjects. The ICC were identified by an indirect immunoperoxidase method using a polyclonal c-kit antibody.

RESULTS

All six patients with CIIP showed total absence of c-kit+ ICC. A subject with neonatal meconium ileus in the non-CIIP group showed patchy areas devoid of c-kit+ ICC amid normal areas. The c-kit+ ICC had a normal number and distribution pattern in all patients with mechanical obstruction and in the remaining 17 non-CIIP subjects.

CONCLUSIONS

It seems that CIIP is characterized by a total loss of c-kit+ ICC. ICC may play an important role in the etiopathogenesis of CIIP and transient neonatal meconium syndrome, and staining for c-kit receptor may be very useful in the evaluation of motility disorders of the bowel.

Interstitial Cells in the Musculature of the Gastrointestinal Tract: Cajal and Beyond

Expression of the receptor tyrosine kinase KIT on cells referred to as interstitial cells of Cajal (ICC) has been instrumental during the past decade in the tremendous interest in cells in the interstitium of the smooth muscle layers of the digestive tract. ICC generate the pacemaker component (electrical slow waves of depolarization) of the smooth musculature and are involved in neurotransmission. By integration of ICC functions, substantial progress has been made in our understanding of the neuromuscular control of gastrointestinal motility, opening novel therapeutic perspectives. In this article, the ultrastructure and light microscopic morphology, as well as the functions and the development of ICC and of neighboring fibroblast-like cells (FLC), are critically reviewed. Directions for future research are considered and a unifying concept of mesenchymal cells, either KIT positive (the "ICC") or KIT negative "non-Cajal" (including the FLC and possibly also other cell types) cell types in the interstitium of the smooth musculature of the gastrointestinal tract, is proposed. Furthermore, evidence is accumulating to suggest that, as postulated by Santiago Ramon y Cajal, the concept of interstitial cells is not likely to be restricted to the gastrointestinal musculature.