Abnormal vasculature in intestinal neuronal dysplasia

Challenges in the diagnosis of intestinal neuronal dysplasia type B: A look beyond the number of ganglion cells

Intestinal neuronal dysplasia type B (IND-B) is a controversial condition among gastrointestinal neuromuscular disorders. Constipation is its most common clinical manifestation in patients. Despite intense scientific research, there are still knowledge gaps regarding the diagnostic criteria for IND-B in the histopathological analysis of rectal biopsies. The guidelines published in the past three decades have directed diagnostic criteria for quantifying the number of ganglion cells in the nervous plexus of the enteric nervous system. However, it is very complex to distinguish numerically what is pathological from what is normal, mainly because of the difficulty in determining a reliable control group composed of healthy children without intestinal symptoms. Thus, a series of immunohistochemical markers have been proposed to assist in the histopathological analysis of the enteric nervous system. Several of these markers facilitate the identification of other structures of the enteric nervous system, in addition to ganglion cells. These structures may be related to the etiopathogenesis of IND-B and represent new possibilities for the histopathological diagnosis of this disease, providing a view beyond the number of ganglion cells. This review critically discusses the aspects related to the disease definitions and diagnostic criteria of this organic cause of constipation.

Colonic Adventitial Fibromuscular Dysplasia: A Nonspecific Arteriopathy Associated With Hirschsprung Disease and Other Obstructive Disorders

Background Smooth muscle differentiation ("adventitial fibromuscular dysplasia," AFD) was purported as specific to arteries in the transition zone of Hirschsprung disease (HSCR) patients. We investigated AFD in an HSCR population and controls and consider the pathogenesis and significance of the vascular pathology. Design Vascular histology in sections from colonic HSCR resections (n = 55) was compared with age- and site-matched controls with (n = 19) and without (n = 28) non-HSCR obstructive conditions. Vascular pathology was mapped, and correlations were sought between the vascular findings and bowel distension, inflammation, neuromuscular anatomy, preoperative clinical variables, and postsurgical complications. Results One of 2 forms of AFD was identified in 42% (23/55) of the HSCR resections: the previously described "mature" form with adventitial bundles of differentiated smooth muscle cells (7/23, all submucosal) and a newly described "immature" AFD characterized by densely packed myofibroblasts in the arterial adventitia (16/23, 3 submucosal, 3 serosal, and 10 both). Adventitial inflammation and/or medial necrosis was present in the immature form (6/16). Mature submucosal AFD was present in 2/28 (7.1%) nonobstructive and 5/19 (26%) obstructive non-HSCR controls ( P = .10). Immature AFD was only found in less than 1-month-olds, and mature AFD only in older patients, including the 7 affected controls. AFD did not correlate with sex, syndromic status, length of the aganglionic segment, or postoperative complications. AFD was present in grossly dilated (17/23) and narrowed (10/23) regions and in the aganglionic (2/23), ganglionic (14/23), or both (7/23) segments. In several cases, AFD existed proximal to the histological transition zone. Conclusion AFD occurs in HSCR and other obstructive conditions but is significantly less common in the colons of patients with no history of dysmotility. The pathology likely progresses from a reversible accumulation of myofibroblasts in neonates to a stable population of mature smooth muscle cells. The distribution of vascular lesions does not correlate with neuropathological findings and suggests a nonspecific form of vascular injury, possibly related to bowel distension. AFD in HSCR resections has not been shown to be clinically significant and should not influence management.

Altered expression of ATP-sensitive K(+) channels in Hirschsprung's disease

PURPOSE

Hirschsprung's disease-associated enterocolitis (HAEC) is the most common cause of morbidity and mortality in Hirschsprung's disease (HSCR). Altered intestinal epithelial barrier function has been suggested to play a role in the causation of HAEC. In rodent experimental models of colitis, a decreased expression of K(ATP) channels (Subunits: Kir6.1/6.2 and SUR1/2) is reported. We designed this study to determine if K(ATP) channels exist within the human colon and to investigate the expression of different subunits in Hirschsprung's disease.

METHODS

We investigated Kir6.1, Kir6.2, SUR1, and SUR2 expression in ganglionic and aganglionic bowel of HD patients (n=5) and controls (n=5). Western blotting and confocal immunofluorescence were performed.

MAIN RESULTS

Western blot analysis revealed that Kir6.1, Kir6.2, SUR1, and SUR2 are strongly expressed in the normal human colon. Kir6.1, Kir6.2, SUR1, and SUR2 expression was significantly decreased in the aganglionic bowel compared to ganglionic bowel and controls. Kir6.1 and SUR1 expression were also significantly decreased in the ganglionic bowel of HSCR patients compared to controls.

CONCLUSION

We demonstrate for the first time the existence of K(ATP) channels in the human colon. The decreased K(ATP) channel expression in HSCR specimens suggests that an altered K(ATP) expression may interfere with intestinal epithelium barrier function and predispose to HAEC.

hESC Differentiation toward an Autonomic Neuronal Cell Fate Depends on Distinct Cues from the Co-Patterning Vasculature

To gain insight into the cellular and molecular cues that promote neurovascular co-patterning at the earliest stages of human embryogenesis, we developed a human embryonic stem cell model to mimic the developing epiblast. Contact of ectoderm-derived neural cells with mesoderm-derived vasculature is initiated via the neural crest (NC), not the neural tube (NT). Neurovascular co-patterning then ensues with specification of NC toward an autonomic fate requiring vascular endothelial cell (EC)-secreted nitric oxide (NO) and direct contact with vascular smooth muscle cells (VSMCs) via T-cadherin-mediated homotypic interactions. Once a neurovascular template has been established, NT-derived central neurons then align themselves with the vasculature. Our findings reveal that, in early human development, the autonomic nervous system forms in response to distinct molecular cues from VSMCs and ECs, providing a model for how other developing lineages might coordinate their co-patterning.

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Neural crest (NC) cells drive neurovascular co-patterning, as modeled by hESC

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Autonomic differentiation of NC cells depends on contact with perivascular cells

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This requires endothelial-derived NO and T-cadherin-mediated interaction with VSMCs

Classification and diagnostic criteria of variants of Hirschsprung's disease

"Variants of Hirschsprung's disease" are conditions that clinically resemble Hirschsprung's disease (HD), despite the presence of ganglion cells in rectal suction biopsies. The diagnosis and management of these patients can be challenging. Specific histological, immunohistochemical and electron microscopic investigations are required to characterize this heterogeneous group of functional bowel disorders. Variants of HD include intestinal neuronal dysplasia, intestinal ganglioneuromatosis, isolated hypoganglionosis, immature ganglia, absence of the argyrophil plexus, internal anal sphincter achalasia and congenital smooth muscle cell disorders such as megacystis microcolon intestinal hypoperistalsis syndrome. This review article systematically classifies variants of HD based on current diagnostic criteria with an additional focus on pathogenesis, epidemiology, clinical presentation, management and outcome.

Ganglia/nerve fibers ratio correlates with the need for surgery in patients diagnosed with Hirschsprung's disease allied disorder (HAD)

Treatment in Hirschsprung's disease allied disorder (HAD) is surgical. In HAD, surgery is always a question. We investigated the value of ganglia/nerve fibers ratio in prediction of the need for invasive procedures in HAD. Sections of full thickness bowel specimens of 14 patients were stained with antibodies marking ganglia (Anti-Neuron-Specific Enolase, Anti-NSE) and marking nerve fibers (S-100). Six out of seven patients indicated for surgery had low ganglia/nerve fibers ratio. Five out of seven patients, not showing the need for surgery, had high ganglia/nerve fibers ratio. We propose that a lower ganglia/nerve fiber ratio can be used as a predictor of increased need for surgery in HAD.

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

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

Histopathological and immunohistochemical study of the enteric innervations among various types of aganglionoses including isolated and syndromic Hirschsprung disease

We investigated enteric innervations in 15 isolated and five syndromic cases of Hirschsprung disease (HSCR) with immunohistochemistry for the S100 protein (S100), class III a-tubulin (TUJ1), peripherin, neuronal nitric oxide synthase (nNOS) and CD34. The number of neurites per smooth muscle unit of the circular muscle layer (CML) was counted in the longitudinal sections. TUJ1 was the best marker to detect whole neuritic networks of the enteric nervous system. There were differences in the innervation patterns between isolated rectosigmoid aganglionosis (RS) and long segment aganglionosis (LS) including total colonic aganglionosis and extensive aganglionosis. In the aganglionic bowel (AGB) of LS, no nerve fibers innervated smooth muscle units in the CML in the area from the small bowel to the terminal descending colon. In the rectosigmoid region of every type of isolated HSCR, we observed transmural nerve fibers forming meshworks in the CML with TUJ1 and S100 antibodies. In RS, the neurites running parallel with smooth muscle cells gradually decreased in number in the distal portion. However, in the rectosigmoid AGB in LS, those neurites were absent and most neurites perpendicularly crossed the CML. Hypertrophic nerve trunks (HNT) in the submucous and myenteric plexuses were observed more frequently in the rectosigmoid region than in the rostral portion. Based on these data, it is suggested that the neuritic meshworks in the CML of the rectosigmoid AGB might derive from not only the sacral plexus, via HNT, but also intrinsic neurons in the oligoganglionic bowel. All of the syndromic HSCR were RS. In the AGB of RS with Down syndrome, the distribution of neurite meshworks in the CML is markedly reduced. In the AGB of RS with mental retardation suspected of having Mowat-Wilson syndrome, the density of intramuscular innervation was comparatively higher. In the rostral portion to the AGB of syndromic HSCR, myenteric ganglia were clearly small in size, and more numerous per smooth muscle unit with scarce internodal strands. These dysplastic features fall under neither hyperganglionosis nor hypoganglionosis classifications. We considered that syndromic HSCR might occur on the basis of a dysplastic enteric nervous system caused by genetic alteration.

Acetylcholinesterase in Hirschsprung's disease

The association between the congenital absence of colonic ganglion cells and an increased acetylcholinesterase (AChE) expression in the affected tissue is of diagnostic importance in Hirschsprung's disease (HSCR). Investigation of AChE's function in development may also help unravel some of the complex pathophysiology in HSCR. Normal nerves do not stain for AChE, but increased AChE expression is associated with the hypertrophied extrinsic nerve fibres of the aganglionic segment in HSCR. Although a high degree of histochemical diagnostic accuracy exists, results are not always uniform, and false positives and false negatives are reported. False negative results are primarily related to age, and an absence of AChE reaction does not exclude HSCR in neonates within the first 3 weeks after birth. AChE staining results may lack uniformity, resulting in a number of technical modifications that have been made to improve standardization of AChE staining. At least two distinct histological patterns are described, types A and B. The interpretation of increased AChE staining patterns in ganglionated bowel at the time of surgical pull-through remains a problem in patients with HSCR. The development of rapid staining techniques has helped to identify normal ganglionated bowel with greater certainty. The presence of fine AChE neurofibrils in the ganglionated segment has contributed to the debate surrounding intestinal neuronal dysplasia. Quantitative assay of cholinesterase activity confirms the pattern of histochemical staining. AChE is particularly increased in relation to butrylcholinesterase, with one molecular form, the G4 tetrameric form, predominating. It is likely that the raised levels of AChE in aganglionic tissue are the transcriptional consequence of the abnormalities in signalling molecules that characterize HSCR. Evidence suggests that this AChE is functioning in a nonenzymatic capacity to promote cell adhesion and differentiation and that the hypertrophied nerves and neurofibrils may be the result of this increased AChE expression.

Variant Hirschsprung's disease

Conditions that clinically resemble HD despite the presence of ganglion cells on suction rectal biopsy results, can be diagnosed by providing an adequate biopsy and employing a variety of histological techniques. Intestinal neuronal dysplasia is a distinct clinical entity that can be clearly proven histologically. Patients with IND not only have abnormalities of submucosal and myenteric plexuses but also defective innervation of the muscle. Internal sphincter achalasia, which is histologically characterized by nitrergic nerve depletion, can be diagnosed on anorectal manometry and successfully treated by internal sphincter myectomy. The outcome of smooth muscle disorders is generally fatal. The need for surgical intervention should be weighed carefully and individualized because most explorations have not been helpful and are probably not necessary.

Intestinal neuronal dysplasia

Intestinal neuronal dysplasia (IND) is a clinical condition that resembles Hirschsprung's disease. In the past many years investigators have raised doubts about the existence of IND as a distinct histopathologic entity. One strong piece of evidence that IND is a real entity stems from animal models. Recently, two different HOX11L1 knockout mouse models and a heterozygous endothelin B receptor-deficient rat demonstrated abnormalities of the submucous plexus similar to that observed in human IND. This review describes in detail the diagnostic criteria of IND, staining techniques, correlation between histological findings and clinical symptoms, and management of IND.