Myenteric plexus neuropathy in infantile hypertrophic pyloric stenosis

The Oxidative Stress and Nervous Distress Connection in Gastrointestinal Disorders

Oxidative stress is increasingly recognized as a central player in a range of gastrointestinal (GI) disorders, as well as complications stemming from therapeutic interventions. This article presents an overview of the mechanisms of oxidative stress in GI conditions and highlights a link between oxidative insult and disruption to the enteric nervous system (ENS), which controls GI functions. The dysfunction of the ENS is characteristic of a spectrum of disorders, including neurointestinal diseases and conditions such as inflammatory bowel disease (IBD), diabetic gastroparesis, and chemotherapy-induced GI side effects. Neurons in the ENS, while essential for normal gut function, appear particularly vulnerable to oxidative damage. Mechanistically, oxidative stress in enteric neurons can result from intrinsic nitrosative injury, mitochondrial dysfunction, or inflammation-related pathways. Although antioxidant-based therapies have shown limited efficacy, recognizing the multifaceted role of oxidative stress in GI diseases offers a promising avenue for future interventions. This comprehensive review summarizes the literature to date implicating oxidative stress as a critical player in the pathophysiology of GI disorders, with a focus on its role in ENS injury and dysfunction, and highlights opportunities for the development of targeted therapeutics for these diseases.

A histological study of the hph-1 mouse mutant: an animal model of phenylketonuria and infantile hypertrophic pyloric stenosis

AIM

To quantify the chronological sequence of changes in the morphology and immunoreactivity for neurotransmitters in the pylorus of an animal model of infantile hypertrophic pyloric stenosis and phenylketonuria.

METHOD

Thirty specimens of pylorus from hph-1 mice and age/sex matched controls (age range: 10-180 days) were examined using conventional histology and immunohistochemistry for a variety of antigens: protein gene product 9.5, a pan neuronal marker; vasoactive intestinal polypeptide; nitric oxide synthase two antigens coalesced to the same inhibitory neurons in humans; substance P, a potent excitatory neurotransmitter; and calcitonin gene related peptide, a neurotransmitter implicated in the somatic afferent innervation of the stomach. The changes in the morphology of the muscle layers were quantified and statistically analysed for each age group (10, 20, 40, 90 and 180 days).

RESULTS

Between 10 and 90 days of age, all muscle layers of the hph-1 mice were hypertrophied, for example, 10 days, hph-1 longitudinal muscle mean diameter = 3.4, control = 1.8; hph-1 circular muscle width = 11.5, control = 4.7. The hph-1 mice were significantly smaller during this period (40 days, hph-1 weight = 10 g, control = 25 g). There was no change in the pattern of expression of the antigens examined within the hph-1 mice compared with the controls.

CONCLUSION

Hph-1 mice develop a transient smooth muscle hypertrophy of the pylorus attended by gastric distension and failure to gain weight. These changes resolve as the pyloric muscle hypertrophy resolves.

Interstitial cells of Cajal in human gut and gastrointestinal disease

This paper reviews the distribution of interstitial cells of Cajal (ICC) in the human gastrointestinal (GI) tract, based on ultrastructural and immunohistochemical evidence. The distribution and morphology of ICC at each level of the normal GI tracts is addressed from the perspective of their functional significance. Alterations of ICC reported in achalasia of cardia, infantile hypertrophic pyloric stenosis, chronic intestinal pseudoobstruction, Hirschsprung's disease, inflammatory bowel diseases, slow transit constipation, and some other disorders of GI motility as well as in gastrointestinal stromal tumors are reviewed, with emphasis on the place of ICC in the pathophysiology of disease.

Interstitial cells of Cajal in human gut and gastrointestinal disease

This paper reviews the distribution of interstitial cells of Cajal (ICC) in the human gastrointestinal (GI) tract, based on ultrastructural and immunohistochemical evidence. The distribution and morphology of ICC at each level of the normal GI tracts is addressed from the perspective of their functional significance. Alterations of ICC reported in achalasia of cardia, infantile hypertrophic pyloric stenosis, chronic intestinal pseudoobstruction, Hirschsprung's disease, inflammatory bowel diseases, slow transit constipation, and some other disorders of GI motility as well as in gastrointestinal stromal tumors are reviewed, with emphasis on the place of ICC in the pathophysiology of disease.

A quantitative study of the morphological and histochemical changes within the nerves and muscle in infantile hypertrophic pyloric stenosis

PURPOSE

The aim of this study was to quantify changes in dimensions of nerves and muscle and the proportionate expression of neural antigens in infantile hypertrophic pyloric stenosis (IHPS).

METHODS

Twenty specimens of pylorus from children with IHPS and age/sex-matched controls were examined using conventional histology and immunohistochemistry for a range of nerve and muscle antigens. The changes in the proportion of nerves expressing each antigen were quantified and statistically analyzed.

RESULTS

The longitudinal muscle was found to be hypertrophic and protein gene product 9.5-stained nerves appeared longer and thicker in the myenteric plexus and shorter in the longitudinal muscle layer in IHPS. The proportion of nerves that expressed neural nitric oxide synthase (nNOS) was found to be diminished in all the IHPS tissues examined. In the circular muscle and myenteric plexus, the proportion of nerves that expressed vasoactive intestinal polypeptide (VIP) and nNOS was almost identically diminished. The expression of calcitonin gene-related polypeptide and substance P was proportionately reduced in the myenteric plexus.

CONCLUSIONS

The results of this study represent the first quantitative analysis of nerves and muscle in IHPS. The muscle hypertrophy is not restricted to circular muscle layer. The changes in nerve morphology cannot be attributed to a dilutional effect of the muscle hypertrophy. The selective changes in nerve and ganglion morphology varies between tissue layers and neural antigen expressed. The findings of reduced proportions of nerves expressing, in particular, nNOS may shed some light on the etiology of this condition.

The pathology of infantile hypertrophic pyloric stenosis after healing

INTRODUCTION

Infantile hypertrophic pyloric stenosis (IHPS) is a common surgical affection of unknown etiology. The muscular hypertrophy is known to resolve within a few months after pyloromyotomy (PM). The pathology of IHPS has been studied extensively at the time of PM, but the fate of the pylorus after healing remains unknown.

MATERIALS AND METHODS

We had the rare opportunity to study two pyloric biopsy specimens obtained 4 months and 2 years (respectively) after an uncomplicated PM for IHPS. They were compared with the initial specimen in one case, with 26 other specimens of IHPS, and with five normal controls. Immunohistochemistry using the avidin-biotin complex (ABC) system was performed for S-100 and nerve growth factor receptor, as markers for the enteric nervous system, and for the tyrosine kinase receptor c-kit, as a marker for the interstitial cells of Cajal (pacemaker cells). NADPH-diaphorase histochemistry was performed as a marker for the neuronal enzyme nitric oxide synthase, which produces the inhibitory neurotransmitter nitric oxide.

RESULTS

In both cases of IHPS, after healing, the circular musculature was not hypertrophic. For all markers studied, the distribution appeared similar to that in the normal pylorus. In contrast, all specimens obtained at the time of PM displayed a severe reduction of the different markers in the hypertrophic musculature.

DISCUSSION

The pathological features observed in the circular layer in IHPS appear to resolve within a few months after PM. This suggests that the involvement of the enteric nervous system in IHPS might be milder than generally assumed. The etiology remains obscure, but our occasional observations may provide new insight into the pathophysiology of IHPS, and are in agreement with the excellent longterm clinical outcome for IHPS.

The ontogeny of the peptide innervation of the human pylorus, with special reference to understanding the aetiology and pathogenesis of infantile hypertrophic pyloric stenosis

Pyloric stenosis (PS) is a common condition in infancy, which is associated with smooth muscle hypertrophy that results in pyloric outlet obstruction. The author examines the ontogeny of the peptide innervation of the pylorus in fetal tissues and an experimental model in mice and evaluates the histochemical and morphological changes in the pylorus. The data suggest that PS is an intrauterine lesion that occurs by 12 weeks' gestation. This is associated with diminished nitric oxide in human tissues and reduced enzyme activity (resulting from a deficiency in an enzyme cofactor) in mice. Increased vasoactive intestinal polypeptide expression in pyloric myenteric ganglia may be an intrinsic mechanism for resolving this condition.

Lack of intestinal pacemaker (C-KIT-positive) cells in infantile hypertrophic pyloric stenosis

The pathogenesis of infantile hypertrophic pyloric stenosis (IHPS) is not well understood. Recent studies have shown that the protonocogene c-kit is essential for the development or maintenance of autonomic gut motility, and also show that the c-kit gene protein product (C-KIT) positive cells in the mammalian gut are responsible for intestinal pacemaker activity. This study examines cells in the pyloric muscles of 23 patients (16 with IHPS, 7 controls) for the presence of the C-KIT (C-KIT+), using immunohistochemical techniques with antihuman C-KIT sera. In the controls, many C-KIT immunoreactive (IR+) cells were observed in the muscle layers. The myenteric plexuses were demarcated by a moderate number of C-KIT-IR+ cells. However, in the IHPS patients, C-KIT-IR were either absent or significantly reduced. No C-KIT-IR+ cells were found around the myenteric plexuses. These findings suggest that a lack of c-kit expression (as an indicator of intestinal pacemaker activity) in the hypertrophic pyloric smooth muscles may be an important factor in the pathogenesis of IHPS.

Hypertrophic pyloric stenosis: ultrastructural abnormalities of enteric nerves and the interstitial cells of Cajal

Dysfunction of pyloric inhibition has been implicated in the pathophysiology of hypertrophic pyloric stenosis. Normal inhibition likely is mediated by peptidergic enteric nerves and also may involve interstitial cells of Cajal (ICC). The authors used electron microscopy to qualitatively assess these structures in infants with pyloric stenosis and in normal controls. Pyloric muscle strips from five infants with hypertrophic pyloric stenosis, from three normal pediatric organ donors, and from three adults were examined. The following observations were made. (1) Muscle cells were primarily in a proliferative phase in pyloric stenosis and exhibited very few gap junctions between smooth muscle cells or ICC compared with the control specimens. (2) The circular muscle layer in pyloric stenosis was characterized by near absence of large granular vesicle-containing nerve fibers compared with the control specimens. (3) There were fewer nerve cell bodies in the myenteric plexus in pyloric stenosis, and the total number of ganglia was lower than that in control samples. (4) Interstitial cells of Cajal were almost completely absent in patients with hypertrophic pyloric stenosis, but there was a group of cells resembling ICC that was termed ICC-like cells. These cells may represent a failure or delay in the maturation process of the ICC. These findings show that there are significant structural abnormalities of the inhibitory nervous system in hypertrophic pyloric stenosis. The ontogenic origins and functional significance of these results require further investigation.

Abnormal distribution of nerve terminals in infantile hypertrophic pyloric stenosis

Smooth muscle biopsy specimens obtained from nine infants with infantile hypertrophic pyloric stenosis (IHPS) and from three controls were studied immunohistochemically with respect to the distribution of nerve terminals and neurofilaments. To label nerve terminals and neurofilaments, monoclonal antibodies (MAb) 171B5 and 2F11 were used, respectively. In all specimens of the control group, nerve terminals were numerous in both the myenteric plexus and the muscle layer. There were abundant neurofilaments in the myenteric plexus and a moderate number in the muscle layer. In all specimens of the IHPS group, the density of nerve terminals and neurofilaments was reduced in the muscle layer. In the myenteric plexus, there was no such reduction. The results indicate poor neuronal innervation of the muscle layer in the pylorus of infants with IHPS. This poor innervation may be related to the pathogenesis of pyloric stenosis and hypertrophy.

Nitric oxide synthase activity in infantile hypertrophic pyloric stenosis

BACKGROUND

Hypertrophic pyloric stenosis is a common infantile disorder characterized by enlarged pyloric musculature and gastric-outlet obstruction. Its physiopathologic mechanism is not known, but a defect in pyloric relaxation (pylorospasm) has been postulated. Nitric oxide is a mediator of relaxation in the mammalian digestive tract, raising the possibility that pylorospasm could be caused by a defect in nitric oxide production. Since neuronal nitric oxide synthase and NADPH diaphorase are identical, we used the NADPH diaphorase histochemical reaction to study the distribution of nitric oxide synthase in pyloric tissue from patients with infantile hypertrophic pyloric stenosis.

METHODS

We studied pyloric tissue from nine infants with infantile hypertrophic pyloric stenosis and seven control infants and children. Cryostat sections were processed for NADPH diaphorase histochemical analysis. A polyclonal tau antiserum was used to identify the enteric nervous system by immunohistochemical methods.

RESULTS

NADPH diaphorase activity was restricted to the enteric nervous system and blood vessels. In the pyloric tissues from the control patients, intense diaphorase activity was present in the nerve fibers of the circular musculature, in the neurons and nerve bundles of the myenteric plexus, and in some nerve fibers of the longitudinal musculature. In the pyloric tissues from patients with infantile hypertrophic pyloric stenosis, the enteric nerve fibers in the hypertrophied circular musculature were enlarged and distorted and did not contain diaphorase activity, whereas the activity in the myenteric plexus and the longitudinal musculature was preserved.

CONCLUSIONS

We suggest that a lack of nitric oxide synthase in pyloric tissue is responsible for pylorospasm in infantile hypertrophic pyloric stenosis.

Infantile hypertrophic pyloric stenosis: myopathic type

Smooth muscle cell biopsies obtained at pyloromyotomy from 37 children with infantile hypertrophic pyloric stenosis (IHPS) were studied by light and electron microscopy and compared with 6 autopsy control cases without any clinical evidence of this disorder. In cases with IHPS an apparently irregular increase in the number of smooth muscle cells by mitosis was accompanied by an increase of the endoplasmic reticulum, proliferation of mitochondria and regressive changes, such as shrinkage, swelling, necrosis and apoptosis of smooth muscle cells. Other alterations, seen in some but not all cases consisted of large numbers of unusual dense granules some of which were clearly associated with actin filaments and, therefore, regarded as derivatives of the normally occurring dense bodies. Furthermore, intermyofibrillar and subsarcolemmal glycogen accumulations, various nuclear abnormalities and pleomorphic membranous cytoplasmic or nuclear bodies occurred. While smooth muscle cell abnormalities predominated in some cases of IHPS, in others there were more severe axonal changes in the myenteric plexus. It is suggested, therefore, that a primarily myogenic type of IHPS can be distinguished from a predominantly neurogenic type.