Hirschsprung disease and other enteric dysganglionoses

Rectal suction biopsy versus incisional rectal biopsy in the diagnosis of Hirschsprung disease

BACKGROUND

Hirschsprung disease is one of the most common congenital anomalies that affect colorectal function. Rectal biopsy demonstrating the absence of ganglion cells in the affected bowel is the gold standard for diagnosis. Suction and incisional rectal biopsies are appropriate methods for obtaining diagnostic tissue. The goal of this study is to determine if any differences in adequacy exist between suction and incisional rectal biopsies at our institution.

METHODS

We conducted a retrospective review of suction and incisional rectal biopsies for inadequacy per procedure at a tertiary pediatric hospital. Each procedure for rectal biopsy was also evaluated by a number of biopsies per procedure. We used a two-sample test of proportions to compare the inadequacy of suction vs. incisional biopsies.

RESULTS

133 rectal suction biopsy procedures (227 biopsies) and 125 incisional biopsy procedures (140 biopsies) were analyzed. In patients 6 months of age and older, the percentage of inadequate procedures was substantially higher in the suction biopsy group (24.1% vs 0.9%, p < 0.01).

CONCLUSIONS

A substantially higher proportion of inadequacy was found in the suction rectal biopsy group compared to the incisional cohort among the older patient cohort, suggesting incisional biopsies should be strongly considered as the primary rectal biopsy method in patients older than 6 months.

The science of Hirschsprung disease: What we know and where we are headed

The enteric nervous system (ENS) is a rich network of neurons and glial cells that comprise the gastrointestinal tract's intrinsic nervous system and are responsible for controlling numerous complex functions, including digestion, transit, secretion, barrier function, and maintenance of a healthy microbiome. Development of a functional ENS relies on the coordinated interaction between enteric neural crest-derived cells and their environment as the neural crest-derived cells migrate rostrocaudally along the embryonic gut mesenchyme. Congenital or acquired disruption of ENS development leads to various neurointestinal diseases. Hirschsprung disease is a congenital neurocristopathy, a disease of the neural crest. It is characterized by a variable length of distal colonic aganglionosis due to a failure in enteric neural crest-derived cell proliferation, migration, differentiation, and/or survival. In this review, we will review the science of Hirschsprung disease, targeting an audience of pediatric surgeons. We will discuss the basic biology of normal ENS development, as well as what goes awry in ENS development in Hirschsprung disease. We will review animal models that have been integral to studying this disease, as well as current hot topics and future research, including genetic risk profiling, stem cell therapy, non-invasive diagnostic techniques, single-cell sequencing techniques, and genotype-phenotype correlation.

Rare case of adult intestinal hypoganglionosis and review of the literature

Intestinal hypoganglionosis is a rare condition in adults. We report a case of intestinal hypoganglionosis in the mid-distal transverse colon to splenic flexure in a 65-year-old female patient presenting with altered bowel habit and abdominal distension, and reviewed the current literature on this topic. Our patient had a medical history of neurofibromatosis type 1. A preoperative computed tomography (CT) scan demonstrated a grossly dilated transverse colon without obstruction. A laparotomy for subtotal colectomy was performed, with histopathology demonstrating intestinal hypoganglionosis.

PHOX2B Immunostaining: A Simple and Helpful Tool for the Recognition of Ganglionic Cells and Diagnosis of Hirschsprung Disease

Hirschsprung disease (HD) is a congenital disorder of the enteric nervous system that occurs in ∼1 in 5000 live births. It is characterized by the absence of ganglionic cells (GCs) in the distal intestine. The diagnosis relies on the thorough analysis of a rectal suction biopsy (RSB), which must show a complete absence of GCs after careful examination of at least 100 serial sections. Such a negative characteristic explains the difficulty of this diagnosis. Moreover, GCs may be immature in very young or preterm born children, making them hard to recognize. Therefore, ancillary techniques have been developed as diagnostic help, such as acetylcholinesterase histochemistry and calretinin immunostaining. These techniques reveal only indirect clues, focusing mainly on the changes in nerve fibers, but not on GCs themselves. As PHOX2B has been shown to be a very specific transcription factor in GCs and in progenitor enteric nerve cells, we have assessed (i) PHOX2B immunostaining in immature enteric ganglia and (ii) the use of PHOX2B immunostaining for the recognition of GCs on RSBs for suspicion of HD. We have observed PHOX2B expression in all GCs, both mature and immature, and its complete absence in Hirschsprung cases. We suggest that the use of PHOX2B immunostaining is of great help (i) in the recognition of GCs on RSBs regardless of their differentiation and therefore (ii) in the diagnosis of HD.

Submucosal Supernumerary Smooth Muscle Coat: A Common Histologic Finding in Mowat-Wilson Syndrome With or Without Hirschsprung Disease

BACKGROUND

Mowat-Wilson syndrome (MWS) is a multiorgan system disorder caused by ZEB2 (zinc finger E-box-binding homeobox 2) mutations or deletions. One common manifestation is constipation, and approximately half of the patients have Hirschsprung disease (HSCR). In addition to classic histologic features of HSCR, an unusual supernumerary intestinal muscle coat was recently reported in a patient of MWS with HSCR. A similar smooth muscle alteration, segmental additional circular muscle coat, had been described in the specimens from patients with intestinal pseudo-obstruction without MWS or HSCR.

METHOD

Rectal biopsies and rectosigmoidectomy specimens from MWS patients were identified by retrospective reviews of surgical pathology records. Routinely prepared glass slides were examined to determine whether any smooth muscle structural alteration was present. Clinical information was obtained by chart review.

RESULTS

Six MWS patients were identified. A supernumerary smooth muscle coat in the submucosa was present in 3 of them, including 2 of the 4 patients with HSCR.

CONCLUSION

The structural anomaly, termed submucosal supernumerary smooth muscle coat, is not a syndrome-specific pathological feature. However, it appears to be more common than expected in MWS and is consistent with contemporary models for the roles of ZEB2 and related cell signaling pathways in the patterning of intestinal musculature during embryonic development.

Ganglion Cells Are Frequently Present in Pediatric Mucosal Colorectal Biopsies: H&E Sections and Calretinin Immunohistochemistry in the Evaluation of Children With Chronic Constipation

Hirschsprung disease (HD) rarely presents as chronic constipation after the newborn period. At our institution, calretinin immunohistochemistry (CAL) is frequently requested by clinicians on rectal mucosal biopsies (RMBs) taken during colonoscopy in older children in whom suspicion for HD is low. We hypothesized that review of these biopsies would frequently reveal ganglion cells (GCs). We reviewed features of mucosal biopsies (November 2013 to September 2015) from children ≥1 year of age on which clinicians had requested CAL on at least one specimen. A total of 93 biopsies with paired CAL from 83 patients were suitable for study (ages 1-18 years, M:F 1.2). Submitted clinical indication was constipation in 62 patients (75%). GCs were found within or subjacent to muscularis mucosa in 63 biopsies (68%), 12 (19%) of which were designated from a specific anatomic site, eg, 2 or 3 cm. In 25 of 63 (40%) cases, GCs were identified on one of the first 3 sections (median 5th, range 1st-54th). Forty-six cases (73%) contained no or <0.5 mm of submucosa (SM, range 0-2 mm). All but one case (62/63, 98%) with identified GCs showed positive CAL staining; a single case showed equivocal staining. Among the 30 biopsies with no observed GCs, none (0%) had >1 mm of SM, and 21 (70%) had no SM. CAL was positive in 28 (93%) and equivocal/weak in 2 (7%); no additional work-up for HD was pursued. The data suggest that H&E sections of RMBs can exclude HD at a specified site in many cases and provide the basis for a future study examining the utility of CAL in RMBs without SM as a means for excluding HD.

Current practice patterns of rectal suction biopsy in the diagnostic work-up of Hirschsprung's disease: results from an international survey

PURPOSE

The diagnosis of Hirschsprung's disease (HD) was revolutionized by the introduction of rectal suction biopsy (RSB), allowing specimens to be taken without general anesthesia on the ward or as an out-patient procedure. However, insufficient tissue samples are not uncommon, and subsequently histopathologists often remain reluctant to confirm the presence or absence of enteric ganglion cells merely on the basis of submucosal RSBs. The aim of this study was to evaluate the current usage of RSB in the diagnostic work-up of HD based on an international survey.

METHODS

A 15-item questionnaire was distributed among participants and faculty members at the 21st International Meeting of the Pediatric Colorectal Society.

RESULTS

Eighty-seven pediatric surgeons from 30 countries completed the anonymous survey (response rate 70.2 %), grouped into 68 (78.2 %) staff surgeons and 19 (21.8 %) trainees, with a median work experience of 18 years (range 2-45 years). Of these, 74 (85.1 %) use RSB in the diagnostic work-up of patients with suspected HD, whereas 13 (14.9 %) prefer open full-thickness biopsy under general anesthesia. In total, 47 (63.5 %) respondents perform ≥20 RSBs (range 3-100 RSBs) per year. Five different RSB instruments were reported, the most common ones being rbi2 (65.0 %), Solo-RBT (15.0 %) and multipurpose suction biopsy kit (8.3 %). Only 22 (29.7 %) of the respondents use a defined negative suction pressure, with a median of 10 mL air (range 6-25 mL air). The most proximal reported biopsy site was located at a median of 2 cm (range 1-15 cm) above the pectinate line and a median of 2 (range 1-5) specimens are routinely taken, mainly from the posterior rectal wall. Insufficient tissue samples with need for repeat RSB were encountered in a median of 10 % (range 0-40 %). Most frequently used staining methods for rectal biopsies are hematoxylin/eosin (75.9 %), acetylcholinesterase (73.6 %), and calretinin (33.3 %). Overall, 36 (48.6 %) respondents had experienced RSB-related complications, including self-limiting rectal blood loss (n = 28), persistent rectal bleeding requiring blood transfusion (n = 9) and rectal perforation requiring surgical intervention (n = 7).

CONCLUSIONS

Although RSB is considered to be today's gold standard for the diagnosis of HD, many aspects of its current usage are lacking consensus. Therefore, a prospective multi-center study or larger global audit appears warranted to identify if the present survey reflects common surgical practice and to establish universal standards for RSB.

Prospective identification and culture of rat enteric neural stem cells (ENSCs)

Hirschprung's disease (HD), a very common congenital abnormality in children, occurs mainly due to the congenital developmental defect of the enteric nervous system. The absence of enteric ganglia from the distal gut due to deletion in gut colonization by neural crest progenitor cells may lead to HD. The capacity to identify and isolate the enteric neuronal precursor cells from developing and mature tissues would enable the development of cell replacement therapies for HD. However, a mature method to culture these cells is a challenge. The present study aimed to propose a method to culture enteric neural stem cells (ENSCs) from the DsRed transgenic fetal rat gut. The culture medium used contained 15 % chicken embryo extract, basic fibroblast growth factor, and epidermal growth factor. ENSCs were cultured from embryonic day 18 in DsRed transgenic rat. Under inverted microscope and fluorescence staining, ENSCs proliferated to form small cell clusters on the second day of culture. The neurospheres-like structure were suspended in the medium, and there were some filaments between the adherent cells from day 3 to day 6 of the culture. The neurospheres were formed by ENSCs on day 8 of the culture. Network-like connections were formed between the adherent cells and differentiated cells after adding 10 % FBS. The differentiated cells were positive for neurofilament and glial fibrillary acidic protein antibodies. The present study established a method to isolate and culture ENSCs from E18 DsRed transgenic rats in the terminal stage of embryonic development. This study would offer a way to obtain plenty of cells for the future research on the transplantation of HD.

Clinical aspects of neurointestinal disease: Pathophysiology, diagnosis, and treatment

The enteric nervous system (ENS) is involved in the regulation of virtually all gut functions. Conditions referred to as enteric neuropathies are the result of various mechanisms including abnormal development, degeneration or loss of enteric neurons that affect the structure and functional integrity of the ENS. In the past decade, clinical and molecular research has led to important conceptual advances in our knowledge of the pathogenetic mechanisms of these disorders. In this review we consider ENS disorders from a clinical perspective and highlight the advancing knowledge regarding their pathophysiology. We also review current therapies for these diseases and present potential novel reparative approaches for their treatment.

Knockout mouse models of Hirschsprung's disease

PURPOSE

Hirschsprung's disease (HSCR) is a developmental disorder of the enteric nervous system, which occurs due to the failure of neural crest cell migration. Rodent animal models of aganglionosis have contributed greatly to our understanding of the genetic basis of HSCR. Several natural or target mutations in specific genes have been reported to produce developmental defects in neural crest migration, differentiation or survival. The aim of this study was to review the currently available knockout models of HSCR to better understand the molecular basis of HSCR.

METHODS

A review of the literature using the keywords "Hirschsprung's disease", "aganglionosis", "megacolon" and "knockout mice model" was performed. Resulting publications were reviewed for relevant mouse models of human aganglionosis. Reference lists were screened for additional relevant studies.

RESULTS

16 gene knockout mouse models were identified as relevant rodent models of human HSCR. Due to the deletion of a specific gene, the phenotypes of these knockout models are diverse and range from small bowel dilatation and muscular hypertrophy to total intestinal aganglionosis.

CONCLUSIONS

Mouse models of aganglionosis have been instrumental in the discovery of the causative genes of HSCR. Although important advances have been made in understanding the genetic basis of HSCR, animal models of aganglionosis in future should further help to identify the unknown susceptibility genes in HSCR.

Overexpression of Bcl-2 promotes survival and differentiation of neuroepithelial stem cells after transplantation into rat aganglionic colon

Introduction

Neural stem cell transplantation is a promising tool for the restoration of the enteric nervous system in a variety of motility disorders. However, limited cell viability after transplantation has restricted its regenerative capacity. The aim of this study was to evaluate the effect of transplantation of neuroepithelial stem cell (NESC) overexpressing anti-apoptotic gene Bcl-2 on the survival, differentiation and function of grafted cells in rat aganglionic colon.

Methods

NESCs were isolated from neural tube of embryonic rat (embryonic day 11.5) and manipulated to overexpress the Bcl-2 gene. After transplantation into the benzalkonium chloride-induced rat aganglionic colon, grafted cells were visualized in colonic sections. Apoptosis and differentiation of the implanted cells were assessed 1, 4 and 8 weeks post transplantation, respectively. Eight weeks post transplantation, neuronal function of the colon was assessed by measuring the response of muscle strips to electrical field stimulation.

Results

Transplantation with Bcl-2-NESCs reduced apoptosis within the transplant at 1 week compared with the vector-NESC grafted group. Our findings also indicated that overexpression of Bcl-2 in the transplanted NESCs enhanced differentiation into PGP9.5-positive and neuronal nitric oxide synthase-positive neurons at 8-week assessment. Moreover, electrical field stimulation-induced relaxation of colonic strips was also significantly increased in the Bcl-2-NESC grafted group.

Conclusion

Transplantation of NESCs genetically modified to overexpress Bcl-2 may have value for enhancing survival and neurogenesis of grafted cells in the adult gut environment and for improving the efficacy of stem cell therapy following a broad range of gastrointestinal motility disorders.

Histochemical staining for intestinal dysganglionosis: over 30 years experience with more than 1,500 biopsies

PURPOSE

Intestinal dysganglionosis are a group of anomalies of the enteric nervous system that constitute infrequent but severe forms of constipation. Histochemical stainings are the gold standard diagnostic procedure for intestinal dysganglionosis. This study describes our experience with histochemistry in a large series of patients.

METHODS

Between 1977 and 2010, 1,589 biopsies from children with persistent chronic constipation were studied. The specimens were snap frozen, sectioned and stained with acetylcholinesterase (AChE), acetylcholinesterase counterstained with hematoxilin and succinic dehydrogenase (SDH) histochemical stainings.

RESULTS

Among the 1,589 biopsies, 946 (59.5%) were rectal biopsies, 242 (15.2%) were internal sphincter biopsies, 346 (21.8%) were intestinal mapping studies and 42 (2.7%) of them were colon specimens from surgical resections. From the rectal biopsy group, 544 (57.5%) patients were reported as normal. Hirschsprung disease was found in 163 (17.2%) patients with a median age at diagnosis of 8 months and a male to female ratio of 3:1. Intestinal neuronal dysplasia was found in 162 (17.2%) patients, hypoganglionosis in 3 (0.3%) of them and ganglioneuromatosis in 1 (0.1%). In 73 (7.7%) patients, the biopsy was not conclusive for different reasons. 34 out of the 42 resected colon specimens were Hirschsprung disease. Intestinal neuronal dysplasia was found in the proximal segment of the aganglionic bowel in 15 out of 34 (44%) patients. All the aganglionic resected colon specimens had a previous aganglionic rectal biopsy. There were no false positive results in this group.

CONCLUSIONS

Histochemical stainings continue to be the gold standard in the diagnosis of intestinal dysganglionosis. The combination of two histochemical staining techniques provides a high level of accuracy in the diagnosis of intestinal dysganglionosis.

Genetics of Hirschsprung disease and anorectal malformations

Hirschsprung disease (HD) and anorectal malformations (ARMs) result from alterations in hindgut development. It has long been recognized that both recur in families and thus result, at least in part, from genetic factors. Progress in the understanding of the genetic basis of HD has been made by the application of findings from genetic animal models of altered enteric nervous system development to human beings. Several genes have been shown to be important for human enteric nervous system development, and current work is progressing to identify genetic interactions that may explain the variable phenotype of HD. By contrast, understanding of the genetic factors underlying ARMs is much less developed. We and others have shown that genetic factors play an important role in the pathogenesis of ARMs, and many mouse genetic models suggest molecular pathways that may be altered in ARMs.

Human and mouse enteric nervous system neurosphere transplants regulate the function of aganglionic embryonic distal colon

BACKGROUND & AIMS

Recent advances have raised the possibility of treating enteric nervous system (ENS) disorders with transplanted progenitor cells (ENSPC). Although these cells have been shown to migrate and differentiate after transplantation, no functional effects have been demonstrated. We therefore aimed to investigate whether embryonic mouse and neonatal human ENSPC can regulate the contractility of aganglionic bowel.

METHODS

Embryonic mouse and neonatal human ENSPC were grown as neurospheres before transplantation into aganglionic embryonic mouse hindgut explants and culture for 8-12 days. Engraftment and neural differentiation were confirmed using immunofluorescence and transmission electron microscopy. The contraction frequency of transplanted bowel was measured and compared with that of embryonic day 11.5 embryonic ganglionic and aganglionic bowel cultured for the same period. Calcium movement was measured at spatially defined points in bowel wall smooth muscle. Neural modulation of bowel contractility was assessed using tetrodotoxin.

RESULTS

Both mouse and human ENSPC migrated and differentiated after neurosphere transplantation. Transmission electron microscopy demonstrated the existence of synapses. Transplantation restored the high contraction frequency of aganglionic bowel to the lower rate of ganglionic bowel. Calcium imaging demonstrated that neurosphere transplantation coordinates intracellular free calcium levels. Both these effects were reversed by the addition of tetrodotoxin, indicating the functional effect of neurosphere-derived neurons.

CONCLUSIONS

Neonatal human gut is a source of ENSPC that can be transplanted to restore the contractile properties of aganglionic bowel by a neurally mediated mechanism. This may aid development of a stem cell-based treatment for Hirschsprung's disease.

Histochemical staining of rectal suction biopsies as the first investigation in patients with chronic constipation

Rectal suction biopsy (RSB) is the gold standard diagnostic procedure for disorders of bowel motility. This study describes our experience with RSB stained with histochemistry as the first diagnostic approach in a large series of patients presenting with chronic constipation. Between 1993 and 2005, 766 children underwent RSB for persistent chronic constipation. The specimens were snap frozen, sectioned and stained with conventional hematoxylin and eosin (H&E) and with nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) and acetylcholinesterase (AChE) histochemical stainings. Adequate amount of submucosa was present in 655 (85.5%) out of 766 cases and formed the basis of this study. RSB in 540 (82%) patients were reported as normal. Hirschsprung's disease was found in 47 (7.2%) patients with characteristic features of absence of ganglion cells, increased AChE activity in the lamina propria and muscularis mucosae, thick nerve fibers in the submucosa, and a lack of NADPH-d-positive fibers in muscularis mucosae. RSB in 59 (9%) patients presented features of intestinal neuronal dysplasia such as submucosal hyperganglionosis, giant ganglia, ectopic ganglia and increased AChE activity in lamina propria. Hypoganglionosis was suspected in nine (1.3%) children because of sparse or absent ganglion cells and low AChE and NAPDH-d activity in muscularis mucosae. Three patients (0.4%) developed bleeding following RSB, requiring diathermy of the bleeding point. Thus, we conclude that RSB is a simple and safe method when used as the first diagnostic approach in patients with chronic constipation. The combination of two histochemical stainings techniques provides a high level of accuracy in the diagnosis of intestinal dysganglionosis.

Review article: molecular, pathological and therapeutic features of human enteric neuropathies

BACKGROUND

Considerable information has been gathered on the functional organization of enteric neuronal circuitries regulating gastrointestinal motility. However, little is known about the neuropathophysiological mechanisms underlying gastrointestinal motor disorders.

AIM

To analyse the most important pathological findings, clinical implications and therapeutic management of idiopathic enteric neuropathies.

METHODS

PubMed searches were used to retrieve the literature inherent to molecular determinants, pathophysiological bases and therapeutics of gastrointestinal dysmotility, such as achalasia, gastroparesis, chronic intestinal pseudo-obstruction, Hirschsprung's disease and slow transit constipation, to unravel advances on digestive disorders resulting from enteric neuropathies.

RESULTS

Current data on molecular and pathological features of enteric neuropathies indicate that degenerative and inflammatory abnormalities can compromise the morpho-functional integrity of the enteric nervous system. These alterations lead to a massive impairment in gut transit and result in severe abdominal symptoms with associated high morbidity, poor quality of life for patients and established mortality. Many pathophysiological aspects of these severe conditions remain obscure, and therefore treatment options are quite limited and often unsatisfactory.

CONCLUSIONS

This review of enteric nervous system abnormalities provides a framework to better understand the pathological processes underlying gut dysmotility, to translate this knowledge into clinical management and to foster the development of targeted therapeutic strategies.

Characterization of fetal and postnatal enteric neuronal cell lines with improvement in intestinal neural function

BACKGROUND & AIMS

The isolation and culture of primary enteric neurons is a difficult process and yields a small number of neurons. We developed fetal and postnatal enteric neuronal cell lines using H-2K(b)-tsA58 transgenic mice (immortomice) that have a temperature-sensitive mutation of the SV40 large tumor antigen gene under the control of an interferon gamma-inducible H-2K(b) promoter element.

METHODS

Enteric neuronal precursors were isolated from the intestines of E13-mouse fetuses and second day postnatal mice using magnetic immunoselection with a p75NTR antibody. The cells were maintained at the permissive temperature, 33 degrees C, and interferon-gamma for 24 or 48 hours, and then transferred to 39 degrees C in the presence of glial cell line-derived neurotrophic factor for 7 days for further differentiation. Neuronal markers were assessed by reverse-transcription polymerase chain reaction, Western blot, and immunocytochemistry. Neuronal function was assessed by transplanting these cells into the colons of Piebald or nNOS(-/-) mice.

RESULTS

Expression analysis of cells showed the presence of neuronal markers peripherin, PGP9.5, HuD, tau, synaptic marker synaptophysin, characteristic receptors of enteric neurons, Ret, and 5-hydroxytryptamine-receptor subtypes at 33 degrees C and 39 degrees C. Nestin, S-100beta, and alpha-smooth muscle actin were expressed minimally at 39 degrees C. Glial cell line-derived neurotrophic factor resulted in increased phosphorylation of Akt in these cells, similar to primary enteric neurons. Transplantation of cells into the piebald or nNOS(-/-) mice colon improved colonic motility.

CONCLUSIONS

We have developed novel enteric neuronal cell lines that have neuronal characteristics similar to primary enteric neurons. These cells can help us in understanding newer therapeutic options for Hirschsprung's disease.

Neuroepithelial stem cells differentiate into neuronal phenotypes and improve intestinal motility recovery after transplantation in the aganglionic colon of the rat

The purpose of this study was to elucidate the possibility and the biological significance of intracolonic grafting of neuroepithelial stem cells (NESCs) as a therapeutic strategy for neuronal replacement in disorders of the enteric nervous system (ENS) such as aganglionosis. The enteric plexus of rat colon were eliminated by serosal application of the cationic surfactant benzalkonium chloride. NESCs were harvested from the neural tube of embryonic rat, labelled with bromodeoxyuridine (BrdU), and transplanted into the denervated colon. After 2, 4 and 8 weeks, grafted cells were visualized in colon sections by fluorescent double-staining for BrdU and neuronal, astrocytic, neurochemical or stem cell markers. Eight weeks post-transplantation, the intestinal motility was assessed by measuring the changes of intraluminal pressure responding to inflating stimulation and the responses to electrical field stimulation (EFS). Our results indicate that when transplanted into the denervated gut, NESCs survived and could differentiate into neurons and glial cells in vivo. Furthermore, inflation stimulated contraction and EFS-induced response were observed in NESCs grafted group compared with no reaction in denervated group. Therefore, NESCs can survive and function in the denervated rat colon in vivo, which indicates that NESCs provide a promising cellular replacement candidate for ENS.

Detection and significance of serum protein marker of Hirschsprung disease

OBJECTIVE

The objective of this study was to identify a specific fingerprint chromatogram model of serum proteins for early screening and diagnosis of Hirschsprung disease.

METHODS

To detect the protein mass spectrograms of 78 serum specimens (42 specimens of Hirschsprung disease, 16 specimens of adhesive ileus including appendicitis and Meckel diverticulum after operation and inflammatory bowel disease, and 20 specimens of normal control subjects), we used surface-enhanced laser desorption/ionization time of flight mass spectrometry technology, combined with bioinformatics methods (support vector machine) to develop and compare protein mass spectrograms from serum samples.

RESULTS

We identified 3 protein markers, the mass-to-charge ratio of which is positioned at 3221.7, 5639.2, and 6884.2 from the fingerprint chromatogram model of serum protein for early screening and diagnosis of Hirschsprung disease. The markers had 100% sensitivity and specificity.

CONCLUSION

The fingerprint chromatogram model of serum protein using surface-enhanced laser desorption/ionization time of flight mass spectrometry technology combining support vector machine is a new method of early screening and diagnosis of Hirschsprung disease that is worthy of additional research and application.

Advantages of intraoperative semiquantitative evaluation of myenteric nervous plexuses in patients with Hirschsprung disease

BACKGROUND

The reappearance of an occlusive syndrome after surgical treatment of patients with Hirschsprung disease is often caused by incomplete resection of the affected segment. Intraoperative examination of frozen biopsies assists surgery, but interpretation of biopsies in the transitional zone is difficult.

METHODS

We performed retrospective semiquantitative evaluations of myenteric nervous plexuses at the proximal limits of resection specimens from 41 children who were treated for rectocolic Hirschsprung disease using intraoperative examination of transparietal biopsies. The results of the evaluations were correlated with the postoperative courses of the children.

RESULTS

After formalin fixation, the mean length of the aganglionic segments was 8.9 cm (range, 1-37.5 cm). At the proximal limit, the percentage of the circumference of the muscularis propria that was composed of plexuses with ganglion cells was more than 95% in 7 children, 90% to 95% in 21 children, 40% to 80% in 6 children, and 30% or less in 7 children (17%), 4 of whom subsequently developed occlusive syndromes.

CONCLUSIONS

Semiquantitative intraoperative examination of the entire circumference of resected segments facilitates precise evaluation of intrinsic innervation at the level of the anastomosis and may reduce the frequency of recurrence of occlusive symptoms after surgery.

Increased heritability of certain types of anorectal malformations

PURPOSE

Various lines of evidence point to genetic causes for the diverse spectrum of anorectal malformations (ARMs); we therefore studied patterns of heritability in a large case series.

METHODS

We searched our ARM database for all patients having family members with congenital anomalies. This group was analyzed to determine the type of ARM and the specific anomalies in affected family members.

RESULTS

Thirty-nine of 1606 patients (2.4%) had a family member with a congenital anomaly. The associated non-ARM anomalies included sacral masses and gynecologic, hematologic, esophageal, duodenal, renal, and spinal anomalies. Of these, 24 patients (1.4%) had 1 or more family members with an ARM. Among females with a positive family history, 73% of patients had either a vestibular or perineal fistula, compared with only 36% in patients without a family history (P = .0004). Among males, 35% had perineal fistulas compared with only 10% of those without affected family members (P = .0051).

CONCLUSIONS

A positive family history in 1.4% is supportive of a strong genetic component to ARM. The risk of having an affected family member is significantly increased in the presence of a vestibular or perineal fistula. These new data allow for more informed counseling of families with an ARM and support the need for further genetic studies.

Pseudo-obstruction intestinale chronique

Chronic intestinal pseudo-obstruction (CIPO) is a disease characterized by episodes resembling mechanical obstruction in the absence of organic, systemic, or metabolic disorders. Pseudo-obstruction is an uncommon condition and can result from primary (40%) or secondary (60%) causes. The most common symptoms are nausea, vomiting, abdominal distension, abdominal pain and constipation or diarrhea. These symptoms are usually present many years before CIPO diagnosis. They can lead to severe electrolyte disorders and malnutrition. Principles for management of patients with CIPO are: to establish a correct clinical diagnosis in excluding mechanical obstruction; to perform a symptomatic and physiologic assessment of the gastrointestinal tract involved; to look for extra-intestinal manifestations, especially for myopathy and neuropathy; to discuss in some cases a surgery for full-thickness intestinal biopsies, and/or a neuromuscular biopsy in case of mitochondrial cytopathy suspicion. The management is primarily focused on symptom control and nutritional support to prevent weight loss and malnutrition. Treatment of CIPO includes prokinetic agents which may help to reduce gastrointestinal symptoms Courses of antibiotics may be needed in patients with symptoms suggestive of bacterial overgrowth. When necessary, enteral nutrition is preferred. In carefully selected patients, feeding jejunostomy with or without decompression gastrostomy may be tried. Long term parenteral nutrition should be reserved for patients who can not tolerate enteral nutrition. Intestinal transplantation can be discussed in selected patients.

The Hlx homeobox transcription factor is required early in enteric nervous system development

Background

Development of the enteric nervous system (ENS) requires interactions between migrating neural crest cells and the nascent gastrointestinal tract that are dependent upon genes expressed by both cell compartments. Hlx, a homeobox transcription factor gene that is expressed in mouse intestinal and hepatic mesenchyme, is required for normal embryonic growth of intestine and liver, and the Hlx^-/- genotype is embryonic lethal. We hypothesized that Hlx is required for ENS development.

Results

Enteric neurons were identified in Hlx^+/+ and Hlx^-/- mouse embryos by immunostaining of embryo sections for the neural markers PGP9.5 and Phox2b, or by staining for β-galactosidase in whole-mount embryos containing the dopamine β-hydroxylase-nLacZ transgene. In Hlx^+/+ embryos, neural crest cells/enteric neurons have moved from the stomach into the intestine by E10.5. By contrast, neural crest cells/enteric neurons remain largely restricted to the lateral stomach mesenchyme of Hlx^-/- embryos, with only a few scattered neural crest cells/enteric neurons in the intestine between E10.5–16.5.

Conclusion

The Hlx homeobox transcription factor is required for early aspects of ENS development.

Clinicopathological features in 102 cases of Hirschsprung disease

BACKGROUND

Hirschsprung disease [HD] is a predominantly childhood disorder of intestinal motility with a multifactorial and polygenic etiology. The objective of this study was to document the clinical and pathological features of HD in Kuwait, which has an estimated consanguinity rate of 54%.

METHODS

We analyzed all rectal and colonic biopsies (n=268) for suspected HD identified from the records in the Pathology Department of Al-Sabah Hospital for the period between 1994 and 2004.

RESULTS

One hundred and two patients (87 males and 15 females) had histologically confirmed HD. Fifty-eight (57%) were neonates (<1 month of age), while 21% were more than 4 months old. The diagnosis was based on open biopsy in 11 cases and rectal biopsies in 91 cases. Nine patients with open biopsies presented as intestinal obstruction, necrotizing enterocolitis, or perforation. The extent of the disease was unknown in 13 patients. There were 67 males and 3 females with short segment HD. Nine had long segment, two ultra-short segment and eight total colonic aganglionosis (TCA). Five TCA cases involved the small intestine. A skip area was observed in two cases. Six patients had other anomalies. A positive family history for HD was established in three patients. Two of these were male siblings from a consanguineous marriage and had Waardenburg syndrome.

CONCLUSION

This study has highlighted an exceptionally strong male predominance of short segment and a relatively high frequency (5.6%) of small intestinal involvement in HD in Kuwait. These data call for a more detailed epidemiological study with special emphasis on genetics.

Pediatric Surgical Pathology: Pitfalls and Strategies for Error Prevention

Context.—Few data exist regarding quality measures for pediatric surgical pathology, types of errors, or how error-prone situations and diagnostic pitfalls can be minimized.

Objective.—This review reports on survey findings regarding methodology for quality assurance and error detection measurement and classification in pediatric surgical pathology. It presents information regarding, and quality aspects of, intraoperative consultations in pediatric surgical pathology. General strategies for identifying diagnostic pitfalls in pediatric surgical pathology are briefly discussed.

Data Sources.—A survey of children's hospitals based on a survey created by the Association of Directors of Anatomic and Surgical Pathology, literature review, and institutional quality assurance records provided information for this review.

Conclusions.—Approaches to quality assurance and error reduction in pediatric surgical pathology are similar to those used in general surgical pathology. The children's hospitals that were surveyed used a variety of standard quality assurance measures. Because of differences in data collection, classification, and reporting, it is not possible to provide a detailed analysis of the types of diagnostic error across institutions at this time. Intraoperative consultations are a potential source of error. Pediatric neoplasms and Hirschsprung disease account for the majority of intraoperative consultations in the pediatric setting. Further considerations include the unique aspects of pediatric medical and neoplastic disorders and special diagnostic criteria, classification, grading, and staging requirements.

lessen encodes a zebrafish trap100 required for enteric nervous system development

The zebrafish enteric nervous system (ENS), like those of all other vertebrate species, is principally derived from the vagal neural crest. The developmental controls that govern the specification and patterning of the ENS are not well understood. To identify genes required for the formation of the vertebrate ENS, we preformed a genetic screen in zebrafish. We isolated the lessen (lsn) mutation that has a significant reduction in the number of ENS neurons as well as defects in other cranial neural crest derived structures. We show that the lsn gene encodes a zebrafish orthologue of Trap100, one of the subunits of the TRAP/mediator transcriptional regulation complex. A point mutation in trap100 causes a premature stop codon that truncates the protein, causing a loss of function. Antisense-mediated knockdown of trap100 causes an identical phenotype to lsn. During development trap100 is expressed in a dynamic tissue-specific expression pattern consistent with its function in ENS and jaw cartilage development. Analysis of neural crest markers revealed that the initial specification and migration of the neural crest is unaffected in lsn mutants. Phosphohistone H3 immunocytochemistry revealed that there is a significant reduction in proliferation of ENS precursors in lsn mutants. Using cell transplantation studies, we demonstrate that lsn/trap100 acts cell autonomously in the pharyngeal mesendoderm and influences the development of neural crest derived cartilages secondarily. Furthermore, we show that endoderm is essential for ENS development. These studies demonstrate that lsn/trap100 is not required for initial steps of cranial neural crest development and migration, but is essential for later proliferation of ENS precursors in the intestine.

[Hirschsprung's disease: practical considerations]

Hirschsprung's disease (1/5000 live births) is defined by the congenital absence of neuronal cells in the nervous plexuses in the distal part of the digestive tract. The disease affects the rectum and sigmoid colon in 80% of cases, or is more extensive. Hirschsprung's disease is suspected in cases of low gastrointestinal obstruction in the neonatal period, or in cases of chronic severe constipation in childhood. It is diagnosed by pathological examination of rectal biopsies that include the submucosa. After standard staining, multiple sections are scrutinized for neuronal cells. Acetylcholinesterase staining is performed on a frozen fragment to demonstrate the hyperplasia of cholinergic fibers that is very suggestive of Hirschsprung's disease. This hyperplasia decreases from the rectum to the splenic flexure of the colon. Hyperplasia of extrinsic nerve fibers and rarefaction of neuromuscular junctions in Hirschsprung's disease may be demonstrated immunohistochemically. Differential diagnosis includes chronic intestinal pseudo-obstructions. The treatment for Hirschsprung's disease is, most often, anastomosis of the normally innervated gut to the anal canal. Peri- or pre-operative biopsies assist surgery, but their interpretation is difficult in the transitional zone. The examination of the surgical specimen allows measurement of the aganglionic segment and transitional zone. Different genes (RET, most often) may be involved in sporadic or familial Hirschsprung's disease. Hirschsprung's disease is associated with other digestive or extra-digestive abnormalities in 5 to 30% of patients. Associated abnormalities may delay the diagnosis and treatment of Hirschsprung's disease.

Development of the enteric nervous system, smooth muscle and interstitial cells of Cajal in the human gastrointestinal tract

The generation of functional neuromuscular activity within the pre-natal gastrointestinal tract requires the coordinated development of enteric neurons and glial cells, concentric layers of smooth muscle and interstitial cells of Cajal (ICC). We investigated the genesis of these different cell types in human embryonic and fetal gut material ranging from weeks 4-14. Neural crest cells (NCC), labelled with antibodies against the neurotrophin receptor p75NTR, entered the foregut at week 4, and migrated rostrocaudally to reach the terminal hindgut by week 7. Initially, these cells were loosely distributed throughout the gut mesenchyme but later coalesced to form ganglia along a rostrocaudal gradient of maturation; the myenteric plexus developed primarily in the foregut, then in the midgut, and finally in the hindgut. The submucosal plexus formed approximately 2-3 weeks after the myenteric plexus, arising from cells that migrated centripetally through the circular muscle layer from the myenteric region. Smooth muscle differentiation, as evidenced by the expression of alpha-smooth muscle actin, followed NCC colonization of the gut within a few weeks. Gut smooth muscle also matured in a rostrocaudal direction, with a large band of alpha-smooth muscle actin being present in the oesophagus at week 8 and in the hindgut by week 11. Circular muscle developed prior to longitudinal muscle in the intestine and colon. ICC emerged from the developing gut mesenchyme at week 9 to surround and closely appose the myenteric ganglia by week 11. By week 14, the intestine was invested with neural cells, longitudinal, circular and muscularis mucosae muscle layers, and an ICC network, giving the fetal gut a mature appearance.

Human enteric neuropathies: morphology and molecular pathology

The aim of this study is to review current understanding of the molecular and morphological pathology of the enteric neuropathies affecting motor function of the human gastrointestinal tract and to evaluate the described pathological entities in the literature to assess whether a new nosology may be proposed. The authors used PUBMED and MEDLINE searches to explore the literature pertinent to the molecular events and pathology of gastrointestinal motility disorders including achalasia, gastroparesis, intestinal pseudo-obstruction, colonic inertia and megacolon in order to characterize the disorders attributable to enteric gut neuropathies. This scholarly review has shown that the pathological features are not readily associated with clinical features, making it difficult for a patient to be classified into any specific category. Individual patients may manifest more than one of the morphological and molecular abnormalities that include: aganglionosis, neuronal intranuclear inclusions and apoptosis, neural degeneration, intestinal neuronal dysplasia, neuronal hyperplasia and ganglioneuromas, mitochondrial dysfunction (syndromic and non-syndromic), inflammatory neuropathies (caused by cellular or humoral immune mechanisms), neurotransmitter diseases and interstitial cell pathology. The pathology of enteric neuropathies requires further study before an effective nosology can be proposed. Carefully studied individual cases and small series provide the basic framework for standardizing the collection and histological evaluation of tissue obtained from such patients. Combined clinical and histopathological studies may facilitate the translation of basic science to the clinical management of patients with enteric neuropathies.

Roles for GFRα1 receptors in zebrafish enteric nervous system development

Components of the zebrafish GDNF receptor complex are expressed very early in the development of enteric nervous system precursors, and are already present as these cells begin to enter the gut and migrate caudally along its length. Both gfra1a and gfra1b as well as ret are expressed at this time, while gfra2 expression, the receptor component that binds the GDNF-related ligand neurturin, is not detected until the precursors have migrated along the gut. Gfra genes are also expressed in regions of the zebrafish brain and peripheral ganglia, expression domains conserved with other species. Enteric neurons are eliminated after injection with antisense morpholino oligonucleotides against ret or against both Gfra1 orthologs, but are not affected by antisense oligonucleotides against gfra2. Blocking GDNF signaling prevents migration of enteric neuron precursors, which remain positioned at the anterior end of the gut. Phenotypes induced by injection of antisense morpholinos against both Gfra orthologs can be rescued by introduction of mRNA for gfra1a or for gfra2, suggesting that GFRα1 and GFRα2 are functionally equivalent.

Neuronal dysplasia: A controversial pathological correlate of intestinal pseudo-obstruction

The infant or child with intestinal pseudo-obstruction poses many challenges for geneticists and other specialists. Although a well-defined anatomic diagnosis (e.g., Hirschsprung disease) can be established for a subset of patients, the pathological correlates for many patients are non-existent or controversial. Intestinal neuronal dysplasia (IND) is frequently considered in the differential diagnosis, despite the fact that existence and significance of the abnormal histopathological features that characterize IND are hotly debated. This review highlights some of the concerns regarding this diagnosis including problems with the diagnostic criteria, the manner in which these criteria are applied in contemporary pathology practices, and the likelihood that many of the pathological findings are secondary consequences of impaired motility with no other clear clinical significance. Possible genetic and developmental bases for IND are also discussed.

The enteric nervous system III: a target for pharmacological treatment

The past decade has seen major advances in the pharmacological understanding of the nervous system of the gastrointestinal tract, the enteric nervous system, and its importance for gut functions in several states of disease. Indeed, the enteric nervous system has become a promising target in the treatment of many gastrointestinal symptoms and disorders. Some of these new therapeutic concepts, such as botulinum toxin for achalasia and serotonergic drugs for functional bowel diseases, are already in clinical use. This paper is part 3 of three Minireviews in Pharmacology & Toxicology, and presents the neurogastrointestinal pharmacological therapeutic options in gastrointestinal pain, functional gastrointestinal disorders, inflammatory bowel diseases, cancer and related conditions with focus on future drug targets. The diagnosis of gastrointestinal neuropathy, the role of serotonin and related neuroendocrine transmitters, serotonergic drugs, and neurotrophic factors in neurogastrointestinal pharmacology will be addressed in this context.

Detection of ganglion cells in the colonic plexuses by immunostaining for neuron-specific marker NeuN: an aid for the diagnosis of Hirschsprung disease

The majority of ganglion cells in the colonic plexuses can be easily and specifically identified by immunostaining for neuronal marker NeuN. The distance between the neighboring solitary ganglion cells or groups of ganglion cells varied from 0.18 to 4.0 mm, average 1.0 mm, in ganglionic segments of colons of patients with Hirschsprung disease, and from 0.3 to 6.3 mm, average 1.43 mm, in colons of pediatric patients with chronic constipation of various etiologies. No ganglion cells were detected in aganglionic colonic segments of patients with Hirschsprung disease by this method.

Clinical and morphofunctional features of idiopathic myenteric ganglionitis underlying severe intestinal motor dysfunction: a study of three cases

Ganglionitis, i.e., the inflammatory neuropathy characterized by a marked lymphoplasmacellular infiltrate in the myenteric plexus, may underlie a variety of paraneoplastic, infectious, or neurological disorders, although occasional cases are idiopathic in origin. We report clinical, manometric, morphofunctional, and immunological features of three cases of idiopathic ganglionitis. All patients had megacolon and underwent surgery for repeated episodes of intestinal subocclusion. Esophageal, GI, and colonic manometry performed in one patient showed dysmotility of the whole gut. Histological examination of colonic and ileum specimens identified a prominent lymphoplasmacellular infiltrate within the myenteric plexus along with a marked decrease of a wide array of neuronal peptides/transmitters. In one patient, tissue analysis revealed progressive neuronal changes up to marked myenteric neuron damage. The inflammatory infiltrate in all patients comprised CD4+ and CD8+ T lymphocytes. Abundance of both subclasses of lymphocytes suggests that immune-mediated mechanisms were responsible for neuronal degeneration. In one patient, systemic steroid therapy brought a significant clinical improvement. The immunosuppressive approach deserves further investigation in patients with severe gut motor abnormalities attributable to idiopathic myenteric ganglionitis.

In ovo transplantation of enteric nervous system precursors from vagal to sacral neural crest results in extensive hindgut colonisation

The enteric nervous system (ENS) is derived from vagal and sacral neural crest cells (NCC). Within the embryonic avian gut, vagal NCC migrate in a rostrocaudal direction to form the majority of neurons and glia along the entire length of the gastrointestinal tract, whereas sacral NCC migrate in an opposing caudorostral direction, initially forming the nerve of Remak, and contribute a smaller number of ENS cells primarily to the distal hindgut. In this study, we have investigated the ability of vagal NCC, transplanted to the sacral region of the neuraxis, to colonise the chick hindgut and form the ENS in an experimentally generated hypoganglionic hindgut in ovo model. Results showed that when the vagal NC was transplanted into the sacral region of the neuraxis, vagal-derived ENS precursors immediately migrated away from the neural tube along characteristic pathways, with numerous cells colonising the gut mesenchyme by embryonic day (E) 4. By E7, the colorectum was extensively colonised by transplanted vagal NCC and the migration front had advanced caudorostrally to the level of the umbilicus. By E10, the stage at which sacral NCC begin to colonise the hindgut in large numbers, myenteric and submucosal plexuses in the hindgut almost entirely composed of transplanted vagal NCC, while the migration front had progressed into the pre-umbilical intestine, midway between the stomach and umbilicus. Immunohistochemical staining with the pan-neuronal marker, ANNA-1, revealed that the transplanted vagal NCC differentiated into enteric neurons, and whole-mount staining with NADPH-diaphorase showed that myenteric and submucosal ganglia formed interconnecting plexuses, similar to control animals. Furthermore, using an anti-RET antibody, widespread immunostaining was observed throughout the ENS, within a subpopulation of sacral NC-derived ENS precursors, and in the majority of transplanted vagal-to-sacral NCC. Our results demonstrate that: (1) a cell autonomous difference exists between the migration/signalling mechanisms used by sacral and vagal NCC, as transplanted vagal cells migrated along pathways normally followed by sacral cells, but did so in much larger numbers, earlier in development; (2) vagal NCC transplanted into the sacral neuraxis extensively colonised the hindgut, migrated in a caudorostral direction, differentiated into neuronal phenotypes, and formed enteric plexuses; (3) RET immunostaining occurred in vagal crest-derived ENS cells, the nerve of Remak and a subpopulation of sacral NCC within hindgut enteric ganglia.

Enteric nervous system: development and developmental disturbances--part 1

This review, which is presented in two parts, summarizes and synthesizes current views on the genetic, molecular, and cell biological underpinnings of the early embryonic phases of enteric nervous system (ENS) formation and its defects. In the first part, we describe the critical features of two principal abnormalities of ENS development: Hirschsprung's disease (HSCR) and intestinal neuronal dysplasia type B (INDB) in humans, and the similar abnormalities in animals. These represent the extremes of the diagnostic spectrum: HSCR has agreed and unequivocal diagnostic criteria, whereas the diagnosis and even existence of INDB as a clinical entity is highly controversial. The difficulties in diagnosis and treatment of both these conditions are discussed. We then review the genes now known which, when mutated or deleted, may cause defects of ENS development. Many of these genetic abnormalities in animal models give a phenotype similar or identical to HSCR, and were discovered by studies of humans and of mouse mutants with similar defects. The most important of these genes are those coding for molecules in the GDNF intercellular signaling system, and those coding for molecules in the ET-3 signaling system. However, a range of other genes for different signaling systems and for transcription factors also disturb ENS formation when they are deleted or mutated. In addition, a large proportion of HSCR cases have not been ascribed to the currently known genes, suggesting that additional genes for ENS development await discovery.

Development of the enteric nervous system

Development of the ENS requires the function of a diverse set of genes encoding transcription factors, signaling molecules, and their receptors. Mutations of these genes result in altered ENS function in animals and humans. In particular, such mutations have been shown to contribute to many cases of Hirschsprung's disease. Elucidation of the mechanisms of ENS development and function allow the development of new approaches to the diagnosis, therapy, and prevention of human disorders of gastrointestinal motility.

Hydrocephalus and intestinal aganglionosis: is L1CAM a modifier gene in Hirschsprung disease?

Congenital hydrocephalus associated with aqueductal stenosis and/or agenesis of the corpus callosum has been described in newborn males with mutations in L1CAM, a gene that encodes a neural cell adhesion molecule. These males usually have severe mental retardation and may have spastic paraplegia and adducted thumbs. In contrast, Hirschsprung disease, or absence of ganglion cells in the distal gut, has rarely been described in such individuals. We report a male infant who had severe hydrocephalus identified in the prenatal period with evidence of aqueductal stenosis and adducted thumbs at birth. He developed chronic constipation, and rectal biopsy confirmed the diagnosis of Hirschsprung disease. Molecular testing of the L1CAM gene revealed a G2254A mutation, resulting in a V752M amino acid substitution. A common polymorphism in RET, but no mutation, was identified. Our patient represents the third example of coincident hydrocephalus and Hirschsprung disease in an individual with an identified L1CAM mutation. We hypothesize that L1CAM-mediated cell adhesion may be important for the ability of ganglion cell precursors to populate the gut, and that L1CAM may modify the effects of a Hirschsprung disease-associated gene to cause intestinal aganglionosis.

Gdnf haploinsufficiency causes Hirschsprung-like intestinal obstruction and early-onset lethality in mice

Hirschsprung disease (HSCR) is a common congenital disorder that results in intestinal obstruction and lethality, as a result of defective innervation of the gastrointestinal (GI) tract. Despite its congenital origin, the molecular etiology of HSCR remains elusive for >70% of patients. Although mutations in the c-RET receptor gene are frequently detected in patients with HSCR, mutations in the gene encoding its ligand (glial cell line-derived neurotrophic factor [GDNF]), are rarely found. In an effort to establish a possible link between human HSCR and mutations affecting the Gdnf locus, we studied a large population of mice heterozygous for a Gdnf null mutation. This Gdnf(+/-) mutant cohort recapitulates complex features characteristic of HSCR, including dominant inheritance, incomplete penetrance, and variable severity of symptoms. The lack of one functioning Gdnf allele causes a spectrum of defects in gastrointestinal motility and predisposes the mutant mice to HSCR-like phenotypes. As many as one in five Gdnf(+/-) mutant mice die shortly after birth. Using a transgenic marking strategy, we identified hypoganglionosis of the gastrointestinal tract as a developmental defect that renders the mutant mice susceptible to clinical symptoms of HSCR. Our findings offer a plausible way to link an array of seemingly disparate features characteristic of a complex disease to a much more narrowly defined genetic cause. These findings may have general implications for the genetic analysis of cause and effect in complex human diseases.

Neuropathology of paediatric chronic intestinal pseudo-obstruction and related animal models

Chronic intestinal pseudo-obstruction (CIP) in paediatric patients is due to heterogeneous aetiologies that include primary disorders of the enteric nervous system. These conditions are poorly delineated by contemporary diagnostic approaches, in part because the complex nature of the enteric nervous system may shelter significant physiological defects behind subtle or quantitative anatomical changes. Until recently, relatively few experimental animal models existed for paediatric CIP. However, the availability of rodent models, particularly novel mutants created in the last few years by genetic manipulations, has brought unprecedented opportunities to investigate molecular, cellular, physiological, and histological details of enteric neuropathology. Information gleaned from studies of these animals is likely to change diagnostic and therapeutic approaches to paediatric CIP and related conditions.

Hypercellular/heterotopic ganglia in omphalomesenteric duct remnants

Omphalomesenteric duct remnants (ODR) including Meckel diverticula often present with symptoms of bowel obstruction. Their histologic features are varied and include heterotopic gastrointestinal mucosa and/or pancreatic tissue within the wall. Abnormalities of the submucosal plexus of Meissner, however, have not been documented in the literature. Thus, we have examined a number of ODR for evidence of ganglion abnormalities. Fifty-three cases of ODR were retrieved from our archives, along with 25 nonduodenal small bowel control specimens obtained from autopsies of patients without clinical or pathologic evidence of enteropathy. Histologic criteria for the diagnosis of abnormal hypercellular/heterotopic ganglia (HHG) in ODR were defined as a single submucosal ganglion/plexus containing > 10 neurons, or > 5 submucosal ganglions per high-power (x 40) field, or heterotopic ganglion cells within the muscularis mucosa or the lamina propria. HHG, histologically indistinguishable from intestinal neuronal dysplasia type B, were found in more than half of the ODR (ODR: 51.9%, n = 50 vs. control: 4%, n = 25, P = 3.6 x 10(-6), particularly those excised for obstructive complications (ODR with acute abdomen: 65.7%, n = 35, vs. ODR without acute abdomen: 33.3%, n = 15, P = 0.035). HHG were present in equal numbers of inflamed and noninflamed ODR (inflamed: 53.6%, n = 28, vs. noninflamed: 59.1%, n = 22, P = 0.70). A similar incidence was found in ODR with heterotopia and without (with heterotopia: 61.1%, n = 18, vs. without: 53.1%, n = 32, P = 0.59). ODR frequently contained HHG histomorphologically similar to those found in intestinal neuronal dysplasia, type B (IND-B). The overrepresentation of HHG in symptomatic ODR patients suggests an association with bowel obstruction. The data did not demonstrate a relationship with either inflammation or heterotopia.

Pediatric anorectal disorders

Anorectal disorders are common in children. It has been estimated that 10% of children are brought to medical attention because of a defecation disorder, and constipation is the chief complaint in 3% to 5% of all visits to pediatricians. Most of these children suffer from functional constipation. There are substantial differences in the approach to children and adults with anorectal disorders. This article discusses the commonest pediatric anorectal disorders, emphasizing the differences between children and adults in terms of clinical presentations, pathophysiology, diagnosis, and treatment.

Genetics of Hirschsprung disease

Hirschsprung disease (HSCR), or congenital intestinal aganglionosis, is a relatively common disorder of neural crest migration. It has a strong genetic basis, although simple Mendelian inheritance is rarely observed. Hirschsprung disease is associated with several other anomalies and syndromes, and animal models for these conditions exist. Mutations in the RET gene are responsible for approximately half of familial cases and a smaller fraction of sporadic cases. Mutations in genes that encode RET ligands (GDNF and NTN); components of another signaling pathway (EDNRB, EDN3, ECE-1); and the transcription factor, SOX10, have been identified in HSCR patients. A subset of these mutations is associated with anomalies of pigmentation and/or hearing loss. For almost every HSCR gene, incomplete penetrance of the HSCR phenotype has been observed, probably due to genetic modifier loci. Thus, HSCR has become a model of a complex polygenic disorder in which the interplay of different genes is currently being elucidated.