Children with Hirschsprung's disease have an abnormal colonic mucus defensive barrier independent of the bowel innervation status

Children with Hirschsprung disease exhibited alterations in host-microbial co-metabolism after pull-through operation

PURPOSE

This study aims to compare the fecal metabolome in post pull-through HD with and without HAEC patients and healthy young children using nuclear magnetic resonance (NMR) spectroscopy.

METHODS

Fresh fecal samples were collected from children under 5 years of age in both post-pull-through HD patients and healthy Thai children. A total of 20 fecal samples were then analyzed using NMR spectroscopy.

RESULTS

Thirty-four metabolites identified among HD and healthy children younger than 5 years were compared. HD samples demonstrated a significant decrease in acetoin, phenylacetylglutamine, and N-acetylornithine (corrected p value = 0.01, 0.04, and 0.004, respectively). Succinate and xylose significantly decreased in HD with HAEC group compared to HD without HAEC group (corrected p value = 0.04 and 0.02, respectively). Moreover, glutamine and glutamate metabolism, and alanine, aspartate, and glutamate metabolism were the significant pathways involved, with pathway impact 0.42 and 0.50, respectively (corrected p value = 0.02 and 0.04, respectively).

CONCLUSION

Differences in class, quantity, and metabolism of protein and other metabolites in young children with HD after pull-through operation were identified. Most of the associated metabolic pathways were correlated with the amino acids metabolism, which is required to maintain intestinal integrity and function.

Hirschsprung's disease associated enterocolitis: A comprehensive review

Hirschsprung's disease (HSCR) is a congenital disorder characterized by failure of the neural crest cells to migrate and populate the distal bowel during gestation affecting different lengths of intestine leading to a distal functional obstruction. Surgical treatment is needed to correct HSCR once the diagnosis is confirmed by demonstrating the absence of ganglion cells or aganglionosis of the affected bowel segment. Hirschsprung's disease associated enterocolitis (HAEC) is an inflammatory complication associated with HSCR that can present either in the pre- or postoperative period and associated with increased morbidity and mortality. The pathogenesis of HAEC remains poorly understood, but intestinal dysmotility, dysbiosis and impaired mucosal defense and intestinal barrier function appear to play a significant role. There is no clear definition for HAEC, but the diagnosis is primarily clinical, and treatment is guided based on severity. Here, we aim to provide a comprehensive review of the clinical presentation, etiology, pathophysiology, and current therapeutic options for HAEC.

Hirschsprung-Associated Enterocolitis: Transformative Research from Bench to Bedside

Hirschsprung disease (HSCR) is a congenital disease that is characterized by the absence of intrinsic ganglion cells in the submucosal and myenteric plexuses of the distal colon and is the most common cause of congenital intestinal obstruction. Hirschsprung-associated enterocolitis (HAEC) is a life-threatening complication of HSCR, which can occur either before or after surgical resection of the aganglionic bowel. Even though HAEC is a leading cause of death in HSCR patients, its etiology and pathophysiology remain poorly understood. Various factors have been associated with HAEC, including the mucus barrier, microbiota, immune function, obstruction of the colon, and genetic variations. In this review, we examine our current mouse model of HAEC and how it informs our understanding of the disease. We also describe current emerging research that highlights the potential future of HAEC treatment.

Cholinergic Signaling Attenuates Pro-Inflammatory Interleukin-8 Response in Colonic Epithelial Cells

Infants affected by Hirschsprung disease (HSCR), a neurodevelopmental congenital disorder, lack ganglia of the intrinsic enteric nervous system (aganglionosis) in a variable length of the colon, and are prone to developing severe Hirschsprung-associated enterocolitis (HAEC). HSCR patients typically show abnormal dense innervation of extrinsic cholinergic nerve fibers throughout the aganglionic rectosigmoid. Cholinergic signaling has been reported to reduce inflammatory response. Consequently, a sparse extrinsic cholinergic innervation in the mucosa of the rectosigmoid correlates with increased inflammatory immune cell frequencies and higher incidence of HAEC in HSCR patients. However, whether cholinergic signals influence the pro-inflammatory immune response of intestinal epithelial cells (IEC) is unknown. Here, we analyzed colonic IEC isolated from 43 HSCR patients with either a low or high mucosal cholinergic innervation density (fiber-low versus fiber-high) as well as from control tissue. Compared to fiber-high samples, IEC purified from fiber-low rectosigmoid expressed significantly higher levels of IL-8 but not TNF-α, IL-10, TGF-β1, Muc-2 or tight junction proteins. IEC from fiber-low rectosigmoid showed higher IL-8 protein concentrations in cell lysates as well as prominent IL-8 immunoreactivity compared to IEC from fiber-high tissue. Using the human colonic IEC cell line SW480 we demonstrated that cholinergic signals suppress lipopolysaccharide-induced IL-8 secretion via the alpha 7 nicotinic acetylcholine receptor (a7nAChR). In conclusion, we showed for the first time that the presence of a dense mucosal cholinergic innervation is associated with decreased secretion of IEC-derived pro-inflammatory IL-8 in the rectosigmoid of HSCR patients likely dependent on a7nAChR activation. Owing to the association between IL-8 and enterocolitis-prone, fiber-low HSCR patients, targeted therapies against IL-8 might be a promising immunotherapy candidate for HAEC treatment.

Disparities in the gut metabolome of post-operative Hirschsprung's disease patients

Hirschsprung's disease (HD) is a congenital structural abnormality of the colon seen in approximately 1 to 5000 live births. Despite surgical correction shortly after presentation, up to 60% of patients will express long-term gastrointestinal complaints, including potentially life-threatening Hirschsprung-associated enterocolitis (HAEC). In this study fecal samples from postoperative HD patients (n = 38) and their healthy siblings (n = 21) were analysed using high-resolution liquid chromatography-mass spectrometry aiming to further unravel the nature of the chronic gastrointestinal disturbances. Furthermore, within the patient group, we compared the faecal metabolome between patients with and without a history of HAEC as well as those diagnosed with short or long aganglionic segment. Targeted analysis identified several individual metabolites characteristic for all HD patients as well as those with a history of HAEC and long segment HD. Moreover, multivariate models based on untargeted data established statistically significant (p < 0.05) differences in comprehensive faecal metabolome in the patients' cohort as a whole and in patients with a history of HAEC. Pathway analysis revealed the most impact on amino sugar, lysine, sialic acid, hyaluronan and heparan sulphate metabolism in HD, as well as impaired tyrosine metabolism in HAEC group. Those changes imply disruption of intestinal mucosal barrier due to glycosaminoglycan breakdown and dysbiosis as major metabolic changes in patients' group and should be further explored for potential diagnostic or treatment targets.

The Role of the Gastrointestinal Mucus System in Intestinal Homeostasis: Implications for Neurological Disorders

Mucus is integral to gut health and its properties may be affected in neurological disease. Mucus comprises a hydrated network of polymers including glycosylated mucin proteins. We propose that factors that influence the nervous system may also affect the volume, viscosity, porosity of mucus composition and subsequently, gastrointestinal (GI) microbial populations. The gut has its own intrinsic neuronal network, the enteric nervous system, which extends the length of the GI tract and innervates the mucosal epithelium. The ENS regulates gut function including mucus secretion and renewal. Both dysbiosis and gut dysfunction are commonly reported in several neurological disorders such as Parkinson's and Alzheimer's disease as well in patients with neurodevelopmental disorders including autism. Since some microbes use mucus as a prominent energy source, changes in mucus properties could alter, and even exacerbate, dysbiosis-related gut symptoms in neurological disorders. This review summarizes existing knowledge of the structure and function of the mucus of the GI tract and highlights areas to be addressed in future research to better understand how intestinal homeostasis is impacted in neurological disorders.

Pull-through procedure in children with Hirschsprung disease: A nationwide analysis on postoperative outcomes

PURPOSE

No nationwide studies on hospital readmissions exist for children who have undergone pull-through operations for Hirschsprung disease. The study aim is to identify determinants of postoperative discharge outcomes and hospital readmissions in children with Hirschsprung disease.

METHODS

The Nationwide Readmissions Database for 2010-2014 was queried for children (<18yo) with Hirschsprung disease and whom had undergone pull-through procedure, utilizing ICD-9 codes 751.3 and 48.40-69, respectively. Outcomes included complications and readmissions at 30-day and 1-year. Results were weighted for national estimates.

RESULTS

The cohort consisted of 3635 patients, 75% male and 79% < 1 year of age. Readmission rates at 30 days and 1-year were 20% and 36%, respectively. Overall, the most common diagnoses for readmission were gastrointestinal disorders (46%) and infections (39%). All age groups had a ≥ 10% readmission rate for gastrointestinal disorders. Infants were more likely to be admitted for enterocolitis and infections (16% and 15%), while children (1-6 years old) were most commonly readmitted for electrolyte disturbances (12%). Total hospitalization cost was over $162 million with $24 million from readmissions.

CONCLUSION

Pull-through procedure for Hirschsprung disease is associated with high readmissions and associated economic burden. Age specific interventions to prevent unnecessary readmissions could improve outcomes and curtail healthcare spending.

TYPE OF STUDY

Retrospective Comparative Analysis.

LEVEL OF EVIDENCE

Level III.

Novel Insights into the Pathogenesis of Hirschsprung's-associated Enterocolitis

Objective:

To systematically summary the updated results about the pathogenesis of Hirschsprung's-associated enterocolitis (HAEC). Besides, we discussed the research key and direction based on these results.

Data Sources:

Our data cited in this review were obtained mainly from PubMed from 1975 to 2015, with keywords “Hirschsprung enterocolitis”, “Hirschsprung's enterocolitis”, “Hirschsprung's-associated enterocolitis”, “Hirschsprung-associated enterocolitis”, “HAEC”, and “EC”.

Study Selection:

Articles regarding the pathogenesis of HAEC were selected, and the articles mainly regarding the diagnosis, surgical approach, treatment, and follow-up were excluded.

Results:

Several factors, mainly including mucus barrier, intestinal microbiota, and immune function, as well as some other factors such as genetic variations and surgical reasons, have been found to be related to the pathogenesis of HAEC. Changed quantity and barrier property of mucus, different composition of microbiota, and an abnormal immune state work together or separately trigger HAEC.

Conclusions:

The maintenance of intestinal homeostasis is due to a well cooperation of microbiota, mucus barrier, and immune system. If any part presents abnormal, intestinal homeostasis will be broken. Meanwhile, for patients with Hirschsprung's disease or HAEC, dysfunction of these parts has been found. Thus, the happening of HAEC may be mainly attributed to the disorders of intestinal microbiota, mucus barrier, and immune system.

Exploring the role and diversity of mucins in health and disease with special insight into non-communicable diseases

Mucins are major glycoprotein components of the mucus that coats the surfaces of cells lining the respiratory, digestive, gastrointestinal and urogenital tracts. They function to protect epithelial cells from infection, dehydration and physical or chemical injury, as well as to aid the passage of materials through a tract i.e., lubrication. They are also implicated in the pathogenesis of benign and malignant diseases of secretory epithelial cells. In Human there are two types of mucins, membrane-bound and secreted that are originated from mucous producing goblet cells localized in the epithelial cell layer or in mucous producing glands and encoded by MUC gene. Mucins belong to a heterogeneous family of high molecular weight proteins composed of a long peptidic chain with a large number of tandem repeats that form the so-called mucin domain. The molecular weight is generally high, ranging between 0.2 and 10 million Dalton and all mucins contain one or more domains which are highly glycosylated. The size and number of repeats vary between mucins and the genetic polymorphism represents number of repeats (VNTR polymorphisms), which means the size of individual mucins can differ substantially between individuals which can be used as markers. In human it is only MUC1 and MUC7 that have mucin domains with less than 40% serine and threonine which in turn could reduce number of PTS domains. Mucins can be considered as powerful two-edged sword, as its normal function protects from unwanted substances and organisms at an arm's length while, malfunction of mucus may be an important factor in human diseases. In this review we have unearthed the current status of different mucin proteins in understanding its role and function in various non-communicable diseases in human with special reference to its organ specific locations. The findings described in this review may be of direct relevance to the major research area in biomedicine with reference to mucin and mucin associated diseases.

Impaired Cellular Immunity in the Murine Neural Crest Conditional Deletion of Endothelin Receptor-B Model of Hirschsprung's Disease

Hirschsprung’s disease (HSCR) is characterized by aganglionosis from failure of neural crest cell (NCC) migration to the distal hindgut. Up to 40% of HSCR patients suffer Hirschsprung’s-associated enterocolitis (HAEC), with an incidence that is unchanged from the pre-operative to the post-operative state. Recent reports indicate that signaling pathways involved in NCC migration may also be involved in the development of secondary lymphoid organs. We hypothesize that gastrointestinal (GI) mucosal immune defects occur in HSCR that may contribute to enterocolitis. EdnrB was deleted from the neural crest (EdnrB^NCC-/-) resulting in mutants with defective NCC migration, distal colonic aganglionosis and the development of enterocolitis. The mucosal immune apparatus of these mice was interrogated at post-natal day (P) 21–24, prior to histological signs of enterocolitis. We found that EdnrB^NCC-/- display lymphopenia of their Peyer’s Patches, the major inductive site of GI mucosal immunity. EdnrB^NCC-/- Peyer’s Patches demonstrate decreased B-lymphocytes, specifically IgM⁺IgD^hi (Mature) B-lymphocytes, which are normally activated and produce IgA following antigen presentation. EdnrB^NCC-/- animals demonstrate decreased small intestinal secretory IgA, but unchanged nasal and bronchial airway secretory IgA, indicating a gut-specific defect in IgA production or secretion. In the spleen, which is the primary source of IgA-producing Mature B-lymphocytes, EdnrB^NCC-/- animals display decreased B-lymphocytes, but an increase in Mature B-lymphocytes. EdnrB^NCC-/- spleens are also small and show altered architecture, with decreased red pulp and a paucity of B-lymphocytes in the germinal centers and marginal zone. Taken together, these findings suggest impaired GI mucosal immunity in EdnrB^NCC-/- animals, with the spleen as a potential site of the defect. These findings build upon the growing body of literature that suggests that intestinal defects in HSCR are not restricted to the aganglionic colon but extend proximally, even into the ganglionated small intestine and immune cells.

Hirschsprung's associated enterocolitis

PURPOSE OF REVIEW

Hirschsprung's disease (HSCR) is characterized by an absence of ganglion cells in the distal hindgut, extending from the rectum to a variable distance proximally, and results from a failure of cranial-caudal neural crest cell migration. Hirschsprung's-associated enterocolitis (HAEC) is a condition with classic manifestations that include abdominal distention, fever and foul-smelling stools, and is a significant and life-threatening complication of HSCR. The purpose of this review was to critically evaluate recent findings regarding the pathophysiology of HAEC.

RECENT FINDINGS

Several recent studies have investigated the cause of HAEC in humans and mouse models. These studies suggest that alterations in the intestinal barrier, including goblet cell number and function, and Paneth cell function, impaired gastrointestinal mucosal immunity, including B-lymphocyte trafficking or function and secretory immunoglobulin A production, and dysbiosis of the intestinal microbiota may contribute to the development of HAEC.

SUMMARY

Recent studies add to the body of literature, suggesting that the intestinal defects observed in HSCR are not restricted to the aganglionic segment but extend to the mucosal immune system within and beyond the gastrointestinal tract. Future studies further dissecting the mechanisms of HAEC and validating these findings in humans will allow for the development of directed therapeutic interventions.

Mucus Barriers to Microparticles and Microbes are Altered in Hirschsprung's Disease

Mucus forms a protective hydrogel layer over the intestinal epithelium, presenting a selective and robust barrier to the uptake of particulates and microbe invasion. Disease can alter mucus production and composition, thus potentially modifying mucosal barrier properties. Hirschsprung's disease (HD) is a developmental abnormality of the nervous system often complicated by intestinal infection. An investigation of colonic mucus barrier properties in an HD animal model, endothelin receptor B mutant mice, revealed significantly reduced microsphere (passive) and microbe (active) transport rates (7-fold and 3.6-fold, respectively, in proximal colonic mucus) relative to wild-type. Transport differences were evident in both the ganglionic and aganglionic colon segments, in agreement with the risk of HD-associated enterocolitis after surgery to remove aganglionic colon segments. The development of therapies aimed at altering colonic mucus barrier properties could be explored towards preventing the onset of enterocolitis in HD.

Immunostaining to visualize murine enteric nervous system development

The enteric nervous system is formed by neural crest cells that proliferate, migrate and colonize the gut. Following colonization, neural crest cells must then differentiate into neurons with markers specific for their neurotransmitter phenotype. Cholinergic neurons, a major neurotransmitter phenotype in the enteric nervous system, are identified by staining for choline acetyltransferase (ChAT), the synthesizing enzyme for acetylcholine. Historical efforts to visualize cholinergic neurons have been hampered by antibodies with differing specificities to central nervous system versus peripheral nervous system ChAT. We and others have overcome this limitation by using an antibody against placental ChAT, which recognizes both central and peripheral ChAT, to successfully visualize embryonic enteric cholinergic neurons. Additionally, we have compared this antibody to genetic reporters for ChAT and shown that the antibody is more reliable during embryogenesis. This protocol describes a technique for dissecting, fixing and immunostaining of the murine embryonic gastrointestinal tract to visualize enteric nervous system neurotransmitter expression.

Probiotics prevent Hirschsprung's disease-associated enterocolitis: a prospective multicenter randomized controlled trial

BACKGROUND

Enterocolitis (EC) is the most common and serious postoperative complication of Hirschsprung's disease (HD). Probiotics potentially play a protective role in maintaining intestinal mucosal integrity. Based on the beneficial effects of probiotics, we hypothesized that oral probiotics could decrease the incidence and severity of Hirschsprung's disease-associated enterocolitis (HAEC).

METHODS

We conducted a prospective, multicenter, randomized, and controlled trial to assess whether oral probiotics could decrease the incidence and severity of HAEC. HD patients were randomly assigned into the control group and probiotic-treated group. All children in probiotic-treated group were fed with probiotics per day for 4 weeks. In next 3 months, the incidence and severity of HAEC were analyzed. The peripheral blood T lymphocyte subsets and cytokines, including TNF-α, IFN-γ, IL-6, and IL-10, were analyzed by flow cytometry and enzyme immunoassay (EIA).

RESULTS

Compared with the control group, the incidence of HAEC in the probiotic-treated group was significantly diminished. The severity of EC was also remarkably decreased. Furthermore, probiotics balanced T lymphocyte subsets. Moreover, pro-inflammatory cytokines TNF-α, IFN-γ, and IL-6 were significantly decreased and anti-inflammatory cytokine IL-10 was notably increased in probiotic-treated group.

CONCLUSIONS

Probiotics not only significantly diminished the incidence but also decreased the severity of HAEC. Moreover, our study revealed that probiotics decreased pro-inflammatory cytokine and increased anti-inflammatory cytokine and furthermore balanced T lymphocytes (registered with ClinicalTrials.gov, NCT number: NCT01934959).

Intestinal dysbiosis and bacterial enteroinvasion in a murine model of Hirschsprung's disease

BACKGROUND/PURPOSE

Hirschsprung's disease (HSCR), characterized by the absence of ganglia in the distal colon, results in functional obstruction. Despite surgical resection of the aganglionic segment, around 40% of patients suffer recurrent life threatening Hirschsprung's-associated enterocolitis (HAEC). The aim of this study was to investigate whether gut microbiota and intestinal immunity changes contribute to the HAEC risk in an HSCR model.

METHODS

Mice with neural crest conditional deletion of Endothelin receptor B (EdnrB) and their littermate controls were used (EdnrB-null and EdnrB-het). Bacterial DNA was prepared from cecal contents of P16-18 and P21-24 animals and pyrosequencing employed for microbiome analysis. Ileal tissue was isolated and secretory phospholipase A2 (sPLA2) expression and activity determined. Enteroinvasion of Escherichia coli into ileal explants was measured using an ex vivo organ culture system.

RESULTS

EdnrB-het and EdnrB-nulls displayed similar flora, sPLA2 expression and activity at P16-18. However, by P21-24, EdnrB-hets demonstrated increased Lactobacillus and decreased Bacteroides and Clostridium, while EdnrB-nulls exhibited reciprocal changes. EdnrB-nulls also showed reduced sPLA2 expression and luminal activity at this stage. Functionally, EdnrB-nulls were more susceptible to enteroinvasion with E. coli ex vivo and released less sPLA2 than EdnrB-hets.

CONCLUSIONS

Initially, EdnrB-het and EdnrB-nulls contain similar cecal flora but then undergo reciprocal changes. EdnrB-nulls display dysbiosis, demonstrate impaired mucosal defense, decreased luminal sPLA2 and increased enteroinvasion of E. coli just prior to robust colonic inflammation and death. These findings suggest a role for the intestinal microbiome in the development of HAEC.

Altered goblet cell differentiation and surface mucus properties in Hirschsprung disease

Hirschsprung disease-associated enterocolitis (HAEC) leads to significant mortality and morbidity, but its pathogenesis remains unknown. Changes in the colonic epithelium related to goblet cells and the luminal mucus layer have been postulated to play a key role. Here we show that the colonic epithelium of both aganglionic and ganglionic segments are altered in patients and in mice with Hirschsprung disease (HSCR). Structurally, goblet cells were altered with increased goblet cell number and reduced intracellular mucins in the distal colon of biopsies from patients with HSCR. Endothelin receptor B (Ednrb) mutant mice showed increased goblet cell number and size and increased cell proliferation compared to wild-type mice in aganglionic segments, and reduced goblet cell size and number in ganglionic segments. Functionally, compared to littermates, Ednrb^−/− mice showed increased transepithelial resistance, reduced stool water content and similar chloride secretion in the distal colon. Transcript levels of goblet cell differentiation factors SPDEF and Math1 were increased in the distal colon of Ednrb^−/− mice. Both distal colon from Ednrb mice and biopsies from HSCR patients showed reduced Muc4 expression as compared to controls, but similar expression of Muc2. Particle tracking studies showed that mucus from Ednrb^−/− mice provided a more significant barrier to diffusion of 200 nm nanoparticles as compared to wild-type mice. These results suggest that aganglionosis is associated with increased goblet cell proliferation and differentiation and subsequent altered surface mucus properties, prior to the development of inflammation in the distal colon epithelium. Restoration of normal goblet cell function and mucus layer properties in the colonic epithelium may represent a therapeutic strategy for prevention of HAEC.

Probiotic prophylaxis after pullthrough for Hirschsprung disease to reduce incidence of enterocolitis: a prospective, randomized, double-blind, placebo-controlled, multicenter trial

OBJECTIVE

Hirschsprung-associated enterocolitis (HAEC) is one of the most troublesome problems encountered after a pullthrough. We hypothesized that prophylactic administration of probiotics after a pullthrough procedure would decrease the incidence of HAEC.

STUDY DESIGN

A prospective, double-blind, placebo-controlled, randomized trial was conducted at 2 children's hospitals. Infants undergoing pullthrough were randomized to probiotic or placebo for a period of 3 months post-pullthrough. Primary outcome was incidence of post-operative HAEC. Other outcomes included severity of HAEC by clinical grade, number of HAEC episodes and extent of aganglionosis. Pearson Chi Square analysis, as well as logistic regression, was used for statistical analysis.

RESULTS

Sixty-two patients were recruited (Sites: A=40; B=22). One was lost to follow up and one immediate post-op death was not included in final analysis. Probiotics were administered to 32 patients. Distribution of placebo/probiotics was equal between sites (P=0.858). Mean age at pullthrough was 6.5 ± 8.1(± SD) months. The incidence of HAEC was 28.3%. The incidence of HAEC was not statistically different between probiotic and placebo study groups.

CONCLUSIONS

Incidence of HAEC was not reduced with prophylactic probiotics. Future studies are needed to better determine the etiology and possible ways of preventing this complex condition.

The pathogenesis of Hirschsprung's disease-associated enterocolitis

Hirschsprung's disease-associated enterocolitis (HAEC) remains the most life-threatening complication in Hirschsprung disease (HD) patients. The pathogenesis of HAEC has not been determined and many hypotheses regarding the etiology of HAEC have been proposed. These include a possible causal relationship between the abnormal enteric nervous system development in HD and the development of enterocolitis. Based on the complex genetic causes of HD that have been discovered and the resultant heterogeneous group of patients that exists, the causes of HAEC are likely multiple. New insights regarding the relationship of the role of the enteric nervous system and its interaction between intestinal barrier function, innate host immunity, and commensal microflora have been discovered, which may shed light on this perplexing problem. This review presents current known risk factors of HAEC and the proposed theories and supporting evidence for the potential etiologies of HAEC.

Older age at diagnosis of Hirschsprung disease decreases risk of postoperative enterocolitis, but resection of additional ganglionated bowel does not

PURPOSE

This study was conducted to determine the effect of age at diagnosis and length of ganglionated bowel resected on postoperative Hirschsprung-associated enterocolitis (HAEC).

METHODS

Children who underwent endorectal pull-through (ERPT) between January 1993 and December 2004 were retrospectively reviewed. t Test, analysis of variance, Kaplan-Meier, and Cox's proportional hazards analyses were performed.

RESULTS

Fifty-two children with Hirschsprung disease (median age, 25 days; range, 2 days-16 years) were included. Nineteen (37%) had admissions for HAEC. Proportional hazards regression showed that HAEC admissions decreased by 30% with each doubling of age at diagnosis (P = .03) and increased 9-fold when postoperative stricture was present (P < .01), after controlling for type of ERPT, trisomy 21, transition zone level, and preoperative enterocolitis. Thirty-six children, with age at initial operation less than 6 months, were grouped based on length of ganglionated bowel excised (A [5 cm] and B [>5 cm]). No significant difference in the number of HAEC admissions during initial 2 years post-ERPT was seen between groups A (n = 18) and B (n = 18). The study had a power of 0.8 to detect a difference of 1 admission over 2 years.

CONCLUSIONS

Children diagnosed with Hirschsprung disease at younger ages are at a greater risk for postoperative enterocolitis. Excising a longer margin of ganglionated bowel (>5 cm) does not seem to be beneficial in decreasing HAEC admissions.

New insights into the pathogenesis of Hirschsprung's associated enterocolitis

The management of Hirschsprung's disease (HD) has made dramatic strides over the last 20 years. Research into the embryological development and migration of ganglion cell has enabled a greater understanding of the pathogenesis of the disease. Coupled with new techniques in surgery, such as laparoscopy-assisted pull-through and the transanal pull-through, this knowledge has led to improved outcomes for children with HD. However, although our appreciation of Hirschsprung's associated enterocolitis and its aetiology has increased, there are continued references in the literature to a multitude of theories of pathogenesis. The purpose of this review is to delineate the theories and demonstrate the evidence supporting or otherwise contradicting each other.

Enterocolitis complicating Hirschsprung's disease

Enterocolitis remains a relatively common complication of Hirschsprung's disease with significant morbidity and mortality. The etiology of Hirschsprung's enterocolitis (HEC) is multifactorial and remains poorly understood. Preventative measures and better treatment modalities will evolve out of a better understanding of the underlying pathophysiology. Prompt recognition of HEC allows early intervention and a potential reduction in disease severity and mortality. This review of HEC describes the epidemiology, clinical and pathological features and current best practice in management. Some of the areas of research into etiology and treatment are discussed.

MUC-2 mucin production in Hirschsprung's disease: possible association with enterocolitis development

BACKGROUND/PURPOSE

The etiology of Hirschsprung's-associated enterocolitis (HAEC) is unknown. Previous investigations have suggested that abnormal production of mucins may have an etiologic role. Recently, a series of mucin genes have been identified. MUC-2 is the predominant mucin expressed in humans. The authors have shown previously in vitro that use of MUC-2 can prevent bacterial translocation. Based on this, it was hypothesized that those patients with Hirschsprung's disease (HD) would have an abnormal production of MUC-2 compared with normal patients.

METHODS

Fresh stool specimens were collected from children with a diagnosis of HD (with or without HAEC) and from age-matched control patients. Protein was extracted, and MUC-2 was detected with Western blot analysis. MUC-2 protein expression was quantified by densitometry measurements. Results are expressed as mean density +/- SD. Statistical comparison was done with unpaired t tests, with P less than.05 being considered significant.

RESULTS

MUC-2 expression was detected in all control patients (mean density, 121 +/- 47). MUC-2 level was lowest in one child with a viral-induced diarrhea (density = 71). In those patients with HD, levels of MUC-2 protein expression were significantly lower (P <.05) than controls (12 +/- 15 for all HD patients). Levels of MUC-2 were lowest (nondetectable) in 2 HD patients who had clinical evidence of HAEC.

CONCLUSIONS

MUC-2 production is markedly depressed in patients with Hirschsprung's disease and is absent with enterocolitis. This decline in protein expression may result in a decrease in epithelial barrier function and be a predisposing factor in the development of HAEC.

Characterization of a 500-kb contig spanning the region between c-Ha-Ras and MUC2 on chromosome 11p15.5

The 11p15.5 region is associated with a broad range of diseases, including childhood acute myeloid leukemia; non-small cell lung carcinoma; arthrogryposis multiplex congenita, distal type 2B; and bladder cancer. Since targets for these diseases are unknown, we have constructed a physical map consisting of BAC and PAC clones spanning the region from the HRAS1 gene to the cluster of mucin genes on 11p15.5. The contig spans approximately 500 kb and includes 13 genes (9 novel), 9 STSs (5 novel), and 1 SNP and builds upon a published physical map spanning the region from the telomere to the HRAS gene. In addition, we expand the mucin gene cluster located on 11p15.5 to include a novel mucin-like gene (MUCDHL) located less than 250 kb telomeric to MUC6. The identification of potential disease genes within an organizational and evolutionary context provides valuable clues to function and as such will benefit our understanding of this region of the genome.

Hirschsprung disease and other enteric dysganglionoses

Hirschsprung disease has become a paradigm for multigene disorders because the same basic phenotype is associated with mutations in at least seven distinct genes. As such, the condition poses distinct challenges for clinicians, patients, diagnostic pathologists, and basic scientists, who must cope with the implications of this genetic complexity to comprehend the pathogenesis of the disorder and effectively manage patients. This review focuses on the anatomic pathology, genetics, and pathogenesis of Hirschsprung disease and related conditions. The nature and functions of "Hirschsprung disease genes" are examined in detail and emphasis is placed on the importance of animal models to this field. Where possible, potential uses and limitations of new data concerning molecular genetics and pathogenesis are discussed as they relate to contemporary medical practices.

Histochemical and genetic analysis of colonic mucin glycoproteins in Hirschsprung's disease

BACKGROUND/PURPOSE

Mucin glycoproteins (mucins) recently have been shown to be deficient in the colonic mucosa of patients with Hirschsprung's disease (HD). The authors performed a detailed histo- and immunohistochemical analysis of mucins in the colonic mucosa and studied the expression of mucin genes to characterize histologically mucin quality and gene expression in HD compared with controls.

METHODS

Paraffin-embedded 4-microm thick sections from patients with HD (n = 11 ganglionic, 10 aganglionic) and controls (n = 19) were taken. Slides were stained with mild periodic acid Schiff with and without saponification with KOH (reacts with O-actylated mucins), high iron diamine/alcian blue (differentiates sulphated v nonsulphated mucins), the monoclonal antimucin antibodies, PR3A5 (against di- and tri-O-acetylated sialic acids) and 91.9H (against sulphated mucins). O-acetylation and sulphation both confer an increased resistance of mucins to bacterial degradation and are thought to be important in the defensive function of the colonic mucus gel layer. In situ hybridization was used to study expression of the mucin genes MUC 1, 2, 3, 4, 5AC, 5B, 6, 7, and 8. [35S]-sulphate-labelled antisense oligonucleotide 48mer probes designed to the known tandem repeat domains of MUC genes were used. After hybridization and washing the slides were opposed to Hyperfilm MP for 7 days. The autoradiographs were scored by three independent observers for differences in expression and by image analysis. Those with positive findings were dipped in photographic emulsion, developed, and counterstained for photomicrographs.

RESULTS

There were different patterns of staining dependent on the region of the colon and especially the age of the patient with three reagents. No significant differences in the histological staining pattern was detected between HD patients and controls. The colonic mucins in HD were found to be primarily O-acetylated and sulphated. The MUC gene expression was similar in patients and controls. MUC2 and 4 were strongly expressed, MUC1, 3, and 5B had moderate to weak expression, and MUC 5AB, 6, 7, and 8 had baseline expression.

CONCLUSIONS

The mucin glycoproteins in children with HD, although quantitatively deficient, show no qualitative differences on histo- and immunohistochemical staining from normal controls. The expression of all the known mucin genes, the genetic control of mucin secretion, and the quality of mucins, is similar to normal controls.

Enterocolitis

Enterocolitis continues to be the major cause of morbidity and mortality in patients with Hirschsprung's disease. The exact etiology of Hirschsprung's-associated enterocolitis is not known. This review focuses on the clinical aspects, etiology, and therapy of Hirschsprung's-associated enterocolitis.

Turnover of radioactive mucin precursors in the colon of patients with Hirschsprung's disease correlates with the development of enterocolitis

BACKGROUND/PURPOSE

Mucin glycoproteins (mucins) in the colonic mucus gel layer interact with pathogens performing protective functions by a variety of mechanisms. It is recognised that patients with Hirschsprung's disease (HD) are prone to episodes of enterocolitis even after corrective surgery, the aetiology of which is poorly understood. The authors correlated the turnover of radioactive mucin precursors in organ culture of the proximal ganglionated colon at the time of pull-through with the development of postoperative enterocolitis.

METHODS

The colonic mucins in the retained proximal ganglionated colon of nine HD patients at the time of pull-through were studied. Organ culture of intact mucosa was performed with radioactive mucin precursors 35S-sulphate and 3H-glucosamine. Mucins in the secretions and epithelial cells were then purified by gel filtration. Turnover of the isotopes was determined by relating radioactivity to tissue DNA content. These patients were followed up prospectively for a mean duration of 30.8 months. The patients were assigned to one of two groups according to the criteria of requiring hospital admission for enterocolitis during this period. There were five patients in the group that remained well after corrective surgery and four in the group that developed entercolitis. The turnover values of both radioisotopes were analysed for differences in the two groups of patients.

RESULTS

Patients in the enterocolitis group had a median value for turnover of 331 dpm/microg DNA, and the group that was well had a median value of 2044 dpm/microg DNA. These differences were statistically significant (Mann-Whitney, P = .037).

CONCLUSIONS

A reduced turnover of mucins as shown by incorporation of radioactive precursors will give rise to a defective colonic mucus-defensive barrier. It can be inferred that the lower the turnover, the more prone a patient is to postoperative enterocolitis. It is therefore possible that organ culture with radioactive mucin precursors of the proximal ganglionated mucosa performed at the time of pull-through has a predictive value in the development of postoperative enterocolitis.