Reduced distribution of pacemaking cells in dilated colon

Clinicopathological study of intestinal smooth muscles, interstitial cells of Cajal, and enteric neurons in neonatal jejuno-ileal atresia with special reference to muscle morphometry

PURPOSE

To assess the thickness of the intestinal smooth muscle layer and analyze the distribution and density of interstitial cells of Cajal (ICC) and enteric neurons in the proximal and distal segments of neonatal jejuno-ileal atresia.

METHODS

This is an observational study done over a period of one year in which fifteen cases of jejuno-ileal atresia were included. All the cases underwent laparotomy and resection of the atretic segment with variable portions of the dilated proximal segment and distal segment. Histopathological analysis was done on the sections taken from proximal segments (at 3 cm, 5 cm & 8 cm) and the distal segment (at 2 cm) from the atretic portion. The mean thickness of the inner circular muscle layer (ICML) and outer longitudinal muscle layer (OLML) was assessed in the above segments using image morphometry. In addition, we also analyzed the distribution and density of the ICCs and enteric neurons in the different segments using immunohistochemistry for c-kit and S-100, respectively. Controls included normal jejuno-ileal segments resected from postmortem cases (n=7) and other nonrelated surgeries (n=3). The findings were then compared with each-other and with normal controls.

RESULTS

Mean thickness of ICML and OLML of the proximal segments at 8 cm was significantly lower than at 3 cm and 5 cm of ileal and jejunal atresias (p≪ 0.5). The mean thickness of ICML and OLML of distal segments at 2 cm was similar to the controls in all the atretic cases (p≫ 0.5). The mean ICML thickness at proximal 8 cm segment was similar to the distal segment of both ileal & jejunal atresias (p= 0.06 & 0.37 respectively). The mean thickness of the OLML of the proximal 8 cm segments was significantly more than that at the distal segment (p=0.008) in ileal atresias but was similar in cases of jejunal atresias (p=0.07). Both the proximal and distal segments of ileal as well as jejunal atresias showed reduction in distribution and density of ICCs, as compared to normal controls. The density of ICCs in proximal segments at 3 cm and 5 cm was similar in both ileal (p=0.33) and jejunal segments (p=0.41) but was significantly lower than the proximal 8 cm segments (p≪0.05).The distribution of ICCs in the proximal segment at 8 cm was similar to the distal segments (p≪0.05). S-100 staining showed dense expression of neurons and glial cells with presence of submucosal giant ganglia within the proximal dilated segments as compared to the distal segments and the controls, which were more marked at 3 cm and 5 cm levels than at 8 cm level.

CONCLUSION

Muscle morphometry using image analysis is a simple technique to assess the thickness of the intestinal smooth muscle layers. There is significant smooth muscle hypertrophy along with marked alteration in density and distribution of ICCs and ENS in the dilated proximal segments up to 5 cm, and relatively milder changes at 8 cm levels, as compared to the distal segments and the controls.

TYPE OF STUDY

Prognosis study.

LEVEL OF EVIDENCE

Level II.

Multiple endocrine neoplasia 2B: Differential increase in enteric nerve subgroups in muscle and mucosa

Multiple endocrine neoplasia 2B (MEN2B) is a rare syndrome caused by an activating mutation of the RET gene, leading to enteric gangliomatosis. This child presented with constipation at 1-mo old, was diagnosed with MEN2B by rectal biopsy at 4 mo, had thyroidectomy at 9 mo and a colectomy at 4 years. We studied the extent of neuronal and nerve fibre proliferation and which classes of enteric nerves are affected by examining the colon with multiple neuronal antibodies. Resected transverse colon was fixed, frozen, sectioned and processed for fluorescence immunohistochemistry labelling with antibodies against TUJ1, Hu, ChAT, NOS, VIP, SP and CGRP and cKit. Control transverse colon was from the normal margin of Hirschsprung (HSCR) colon (4-year-old) and a child with familial adenomatous polyposis (FAP, 12 year). Myenteric ganglia were increased in size to as wide as the circular muscle. There was a large increase in nerve cells and nerve fibres. ChAT-, NOS-, VIP- and SP-immunoreactive nerve fibres all increased in the myenteric ganglia. NOS-IR nerves preferentially increased in the muscle, while VIP and SP increased in submucosal ganglia and mucosal nerve fibres. The density of ICC was normal. RET overactivation in MEN2B lead to a large increase in intrinsic nerve fibres in the myenteric and submucosal ganglia, with a relative increase in NOS-IR nerve fibres in the circular muscle and VIP and SP in the submucosal ganglia and mucosa. The changes were associated with severe constipation resulting in colectomy at 4 years.

Significance of abnormalities in systems proximal and distal to the obstructed site of duodenal atresia

BACKGROUND

Duodenal atresia (DA) is a well-known neonatal intestinal disease. Even after surgery, the proximal segment can continue to be severely dilated with hypoperistalsis, resulting in intestinal dysmotility problems in later life. No data have been published regarding the morphologic differences between the proximal and distal regions of obstructed sites of the intramural components in DA.

METHODS

Operative duodenal samples (N = 12) from cases with DA (age 1-3 days) were used. Age-matched controls (N = 2) were used. All of the specimens were immunohistochemically stained with antibodies to S-100 protein, α-smooth muscle actin, and c-kit protein.

RESULTS

At the proximal segments of the obstructed site in DA, the number of neuronal cells decreased in size and number. The circular musculature was moderately to severely hypertrophic. Unusual ectopic smooth muscle bundles were also identified. The innermost layer of the circular musculature was thinner. Interstitial cells of Cajal are decreased, even around the myenteric plexus. All of the staining in the distal segments in DA was similar to the control tissues.

CONCLUSIONS

Proximal and distal segments in DA differ in the neural cells, musculature, and distributions of the interstitial cells of Cajal. Based on the present study, these morphologic changes may contribute to the onset of postoperative duodenal dysmotility.

Gender differences in reduced substance P (SP) in children with slow-transit constipation

PURPOSE

Adult slow-transit constipation (STC) occurs predominantly in females and is associated with low numbers of substance P (SP)-containing nerves in colonic circular muscle.

AIM

To determine if reduced SP nerves is female predominant in paediatric STC.

METHODS

Children with STC were identified from records of more than 600 nuclear transit studies (NTS) and intestinal biopsies done for intractable chronic constipation between November 1998 and March 2009. Colonic seromuscular biopsies collected from hepatic and splenic flexures, and sigmoid colon were processed for immunohistochemistry. Nerve fibre density in circular muscle containing SP was measured qualitatively by a pathologist.

RESULTS

Eighty-eight children with chronic constipation had both NTS and intestinal biopsies. Seventy-eight children (52 M; age 2-15.5 years; mean 7.7 years) had STC diagnosed by NTS. SP was reduced in 10/26 girls, but only 11/52 boys.

CONCLUSION

In this sample, STC was more common in boys than girls. However, in girls with STC, SP deficiency occurred in 40%, when compared with 20% of boys. During puberty, the percentage of girls with reduced SP decreased, whilst the percentage of boys increased. These results suggest that STC is heterogeneous and that there are some gender differences, the implication of which requires further investigation.

Chronic constipation: lessons from animal studies

Chronic constipation is a highly debilitating condition, affecting a significant proportion of the community. The burden to the health care system and impact on individual patients quality of life is immense. Unfortunately, the aetiology underlying chronic constipation is poorly understood and animal models are being used increasingly to investigate possible intrinsic neurogenic and myogenic mechanisms leading to relevant colonic sensori-motor dysfunction. Recently, major advances have been made in our understanding of the mechanisms that underlie propagating contractions along the large intestine, such as peristalsis and colonic migrating motor complexes in laboratory animals, particularly in guinea-pigs and mice. The first recordings of cyclical propagating contractions along the isolated whole human colon have now also been made. This review will highlight some of these advances and how impairments to these motility patterns may contribute to delayed colonic transit, known to exist in a proportion of patients with chronic constipation.

Alterations of Cajal cells in patients with small bowel atresia

PURPOSE

Interstitial cells of Cajal (ICC) are regarded as the pacemaker cells of the gastrointestinal tract. There are some well-designed studies investigating the structure and function of ICC subsequent to experimentally induced intestinal obstructions. However, it remains unclear whether reduction of number of ICC primarily leads to mechanical obstruction of the bowel such as seen in intestinal atresia. We aimed to investigate the number of ICC in proximal and distal parts of the atresias of patients with small bowel atresia.

PATIENTS AND METHODS

Twenty-one patients (13 male and 8 female; median age, 3 days; median gestation age, 38 weeks) with jejunal or ileal atresia underwent primary repair between 2001 and 2009. The demographic data were reviewed. The specimen of the distal and proximal parts of the atretic segments was investigated according to presence and number of ICC in the myenteric plexus using immunohistochemical methods. The jejunum segments of 14 newborns who died from causes other than bowel disease were examined as a control. Scoring and count systems were developed for the evaluation of ICC. A continuous layer of CD-117 immunoreactive Cajal cells around the myenteric plexus was scored as 3, whereas discontinuous and diminished Cajal cells were scored as 2. Few and sparse Cajal cells around the myenteric ganglia and in the muscle layer were scored as 1. If there was no Cajal cell at all, it was scored as zero. In addition, the number of ICC per field was counted. The scores and the numbers of ICC per field were compared in patients with small bowel atresia and control group.

RESULTS

All patients but one survived. One patient was lost because of congenital cardiac anomalies. The median score of control subjects was 3 (range, 1-3). Both the proximal and distal segments of the atretic bowel had a median score of 1 in patients with atresia. Twenty patients' score of proximal (95%) and 19 patients' score of distal bowel segment (90%) had an ICC score of 2 or less. Only 1 control subject (7%) had an ICC score of less than 2. Results were statistically significant in controls and patients. The mean number of ICC in the control group was 5.36 +/- 2.36; in distal segments of patients with atresia, it was 1.03 +/- 1.4; and in proximal segments, it was 0.82 +/- 1.56. The difference between the control group and the patients was statistically significant (P < .05).

CONCLUSION

We demonstrated a remarkable decrease of ICC in small bowel wall of patients with intestinal atresia; but we could not show whether the reduction of ICC is a primary event, which also participates in the pathogenesis of intestinal atresia, or whether the mechanical obstruction caused by any unknown etiology (eg, ischemia) leads to decrease in number of ICC.