Selective depletion of substance P-immunoreactive neurones in the transitional zone of the colon in piebald lethal mice

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.

Hirschsprung's disease: clinical and experimental observations

Hirschsprung's disease (HD) is a relatively common cause of intestinal obstruction in the newborn. It is characterized by an absence of ganglion cells in the distal bowel beginning at the internal sphincter and extending proximally for varying distances. The etiology of HD-associated enterocolitis remains a complex issue. This study has provided further support for a possible infectious etiology of enterocolitis complicating HD.

Natural history and pathophysiology of enterocolitis in the piebald lethal mouse model of Hirschsprung's disease

A breeding colony of piebald lethal mice was established in order to study the natural history of congenital megacolon in a mouse model of Hirschsprung's disease and to investigate mucosal defense mechanisms and secretory functions in enterocolitis complicating congenital megacolon. In experiment 1, 214 mice were studied, 53 of which had congenital megacolon. All piebald lethal mice with congenital megacolon (S1/S1) died at 3 to 11 weeks of age. Two distinct patterns of mortality were identified. A majority of mice (64%) became acutely ill at 3 to 4 weeks of age and died, whereas the remainder died between 9 and 11 weeks of age. The former group of mice exhibited clinical and histologic evidence of severe enterocolitis while the latter group had massive abdominal distension and classical megacolon. In experiment 2, piebald mice with congenital megacolon were killed at the time of acute illness. Significant histologic and immunohistochemical differences were seen in the ganglionic colon between piebald mice with early clinical onset of acute illness and piebald mice with the classical clinical picture of congenital megacolon. In the former group of mice the number of immunocytes in the lamina propria was significantly higher than in control mice (P less than .001), immunoglobulin-producing cells were equally distributed throughout the lamina propria and IgA-containing cells were by far the most abundant cell type identified in the colon. In the latter group of mice, immunocyte responses were significantly low and the distribution of immunocytes markedly different, with the immunoglobulin-producing cells being located only at the deep layer of lamina propria.(ABSTRACT TRUNCATED AT 250 WORDS)

Projections of enteric motor neurons in the mouse distal colon

This study examined the projections in vitro of excitatory and inhibitory colonic motor nerves in the unaffected siblings of mice with hereditary aganglionic colon--a strain of animals used as a model of Hirschsprung's disease. Microelectrode recordings from the circular muscle layer showed ongoing fluctuations in membrane potential (presumably junction potentials) that were sensitive to tetrodotoxin. Transmural electrical stimulation of the intrinsic nerves produced cholinergic excitatory and inhibitory junction potentials. The latter responses were more prolonged when recorded aboral to the stimulating electrodes. Apamin reduced, but did not block, these inhibitory potentials. Cholinergic excitatory junction potentials were abolished by d-tubocurarine when recording 2 mm from the stimulating electrodes; inhibitory junction potentials were recorded up to 10 mm in the presence of this drug. Thus, the intrinsic excitatory cholinergic motor neurons have relatively short projections to the circular smooth muscle compared with the projections of the inhibitory motor neurons.

An immunochemical study with neuron-specific-enolase and substance P of human enteric innervation--the normal developmental pattern and abnormal deviations in Hirschsprung's disease and pyloric stenosis

Human enteric innervation was studied immunochemically with neuron-specific-enolase (NSE), a specific neurone marker indicative of differentiation, and substance P, a potent member of the family of neuropeptides. By examining various levels of the gut in 28 normal human fetuses of gestational ages 9 to 21 weeks, we showed that enteric neurones as a whole, as well as peptidergic neurones in particular, followed a dual gradient of development proceeding from each end to the middle of the gut. This suggests the need for caution in accepting the hypothesis of the pathogenesis of Hirschsprung's disease based on the concept of a single craniocaudal gradient of enteric neuronal development. In studies of six infants with Hirschsprung's disease, NSE immunostaining was found to be potentially useful for diagnostic purposes. NSE activity suggested that the hypertrophied nerve bundles in aganglionic bowel were metabolically active and functionally mature. Substance P-immunoreactivity was decreased in both aganglionic and distal ganglionic bowel in Hirschsprung's disease, suggesting that substance P-nerves were more extensively affected developmentally than other enteric neurones. In 28 infants with pyloric stenosis (IHPS), the presence of intense NSE activity in the ganglia in the pylorus suggested that these neurones were neither immature nor severely degenerated. A decrease in substance P immunoreactivity in IHPS suggested possible involvement of peptidergic innervation in the pathogenesis of IHPS.