Distribution of NADPH-diaphorase-positive neurons in the enteric nervous system of the human colon

What neurons hide behind calretinin immunoreactivity in the human gut?

Calretinin (CALR) is often used as an immunohistochemical marker for the histopathological diagnosis of human intestinal neuropathies. However, little is known about its distribution pattern with respect to specific human enteric neuron types. Prior studies revealed CALR in both myenteric and submucosal neurons, most of which colabel with choline acetyl transferase (ChAT). Here, we specified the chemical code of CALR-positive neurons in small and large intestinal wholemounts in a series of 28 patients. Besides other markers, we evaluated the labeling pattern of CALR in combination with vasoactive intestinal peptide (VIP). In colonic submucosa, CALR and VIP were almost completely colocalized in about three-quarters of all submucosal neurons. In the small intestinal submucosa, both the colocalization rate of CALR and VIP as well as the proportion of these neurons were lower (about one-third). In the myenteric plexus of both small intestine and colon, CALR amounted to 11 and 10 %, respectively, whereas VIP to 5 and 4 % of the whole neuron population, respectively. Colocalization of both markers was found in only 2 and 3 % of myenteric neurons, respectively. In section specimens, nerve fibers coreactive for CALR and VIP were found in the mucosa but not in the muscle coat. Summarizing the present and earlier results, CALR was found in at least one submucosal and two myenteric neuron populations. Submucosal CALR+/VIP+/ChAT± neurons innervate mucosal structures. Furthermore, CALR immunoreactivity in the myenteric plexus was observed in morphological type II (supposed primary afferent) and spiny type I (supposed inter- or motor-) neurons.

Morphological and quantitative study of the myenteric plexus in the human tenia coli

The longitudinal muscle in the large intestine in humans and some other mammalian species is concentrated in regions known as "tenia coli." The myenteric plexus under the tenia is believed to be highly developed to control the adjacent large muscle mass, however, data on the innervation of this region are very scarce. We used whole mount preparations of human colon to characterize the organization of the myenteric plexus under the tenia coli (UT) and compared it with the plexus between the tenia (BT). Using histochemical staining for NADPH diaphorase, we found that the meshwork UT was 50% denser than BT, and that the ganglia UT were 30% wider. The density and size of the NADPH-d positive neurons UT were similar to those of BT. We conclude that the myenteric plexus UT is considerably more developed than BT, and suggest to understand the control of colonic motility, the myenteric plexus UT needs to be further investigated.

Decreased density of ganglia and neurons in the myenteric plexus of familial dysautonomia patients

BACKGROUND

Familial dysautonomia (FD) is a hereditary disease of the autonomic and sensory nervous system. A prominent manifestation of FD is gastrointestinal dyscoordination, which contributes to the morbidity and mortality in FD.

AIM

As the myenteric plexus is an essential factor in gastrointestinal motility control, we compared its morphology in appendices of FD patients and controls.

METHODS

Appendices from FD patients (N=19) were obtained during surgery of fundoplication and gastrostomy; normal appendices (N=17) were obtained from patients suspected to suffer from acute appendicitis, in whom, however, the appendix was found to be normal. Specimens were stained histochemically for NADPH diaphorase (NADPH-d) and in a blinded manner examined under a light microscope for seven morphologic parameters: ganglionic density, neuronal density, ganglionic area, number of stained neurons per ganglion, nerve bundle width, ratio between nervous tissue area and total area, and neuronal area.

RESULTS

Ganglionic density was 10.13 per mm(2) in controls versus 5.01 per mm(2) in FD (p<0.05). Neuronal density was 70.12 per mm(2) in controls, compared with 22.09 per mm(2) in FD (p<0.01). The other parameters were not different between the two groups.

CONCLUSION

Densities of myenteric ganglia and neurons of FD patients were significantly lower than in controls. This deficiency may contribute to the pathogenesis of FD gastroenteropathy.

Regional differences in the number and type of myenteric neurons in the descending colon of rats

The purpose of this study was to analyze the neuronal density of the myenteric plexus of the intermediate and antimesocolic regions of the descending colon of rats. Whole-mounts were stained with three different techniques of neuronal evidenciation. Through counts of the number of neurons in an area of 6.64 mm under light microscopy, we found 1,271 +/- 227.54 neurons with Giemsa in the intermediate region and 1,234 +/- 225.92 neurons in the antimesocolic region; with the NADH-diaphorase technique we found 530 +/- 92.97 neurons in the intermediate region and 539 +/- 146.72 neurons in the antimesocolic region; and through the NADPH-diaphorase histochemistry, we found 417 +/- 34.42 neurons in the intermediate region and 547 +/- 84.01 neurons in the antimesocolic region. We conclude that there is a variation in the density of NADPH-diaphorase positive neurons in the intestinal circumference; that the NADH-diaphorase positive neuronal subpopulation represented 42.7% of that stained with Giemsa; and that the NADPH-diaphorase positive neurons represented 37.8% of the whole myenteric population.

Outer submucous plexus: an intrinsic nerve network involved in both secretory and motility processes in the intestine of large mammals and humans

The architecture of the enteric nerve networks in the gastrointestinal tract appears to be more complex in large mammals, including humans, than in small laboratory animals. At least two distinct ganglionic nerve plexuses could be identified in the submucous layer in the digestive tract of large mammals. While functionally and morphologically similar neuron populations are found in the intestinal wall of both small and large mammals, significant differences in their topographical organization and neurochemical features may be present. This short review clearly illustrates that the close and exclusive association, which has been assumed so far between the efferent pathways of the submucous plexus and regulation of intestinal secretion/absorption on the one hand and between the myenteric plexus and regulation of intestinal motility on the other hand, cannot be interpreted that strictly. An attempt has been made to give a briefoverview of the current status of the identification of distinct functional enteric neuronal classes in the gastrointestinal tract of large mammals using the pig and human intestine as references, and to compare these data with the more extensive information gathered from the guinea-pig intestine.

Projections of nitric oxide synthase and vasoactive intestinal polypeptide-reactive submucosal neurons in the human colon

BACKGROUND

The submucosal plexus is important in the control of secretomotor and motor function of the intestine. Our aim was to describe the projections of submucosal neurons to the mucosa within the submucosal plexus and to the circular muscle of human colon and to determine whether submucosal neurons that projected to different layers were located at different levels of the submucosa.

METHODS

A retrogradely transported fluorescent dye was applied to the mucosa, submucosa or circular muscle layer of human colon which was then maintained in organotypic culture for 5 days. The submucosa was then dissected into two preparations, one containing the inner layer of the submucosal plexus and the other containing both the intermediate and outer layers. The dissected preparations were labelled with antibodies to nitric oxide synthase (NOS) or vasoactive intestinal peptide (VIP).

RESULTS

Submucosal neurons projected to the mucosa, submucosa and circular muscle layers for mean distances of 3.7, 3.0 and 4.3 mm, respectively. Ninety-seven per cent of submucosal neurons labelled from the circular muscle were located in the outer or the intermediate layers, while 51% of those projecting to the mucosa were in inner layer and 49% in the intermediate/outer layers of the submucosal plexus. Eleven per cent of submucosal neurons projecting to the circular muscle were immunoreactive for NOS and 12% were immunoreactive for VIP. Forty-five per cent of those projecting within the submucosa were immunoreactive for VIP and 38% of those projecting to the mucosa were immunoreactive for VIP.

CONCLUSIONS

Submucosal neurons in the human colon innervate the mucosa, circular muscle and submucosa and different functional classes of neurons are located in different layers of the submucosal plexus.

Organization of the enteric nervous system in the human colon demonstrated by wholemount immunohistochemistry with special reference to the submucous plexus

To demonstrate the normal topography and structure of the enteric nervous system (ENS) in the human colon, the colonic wall of patients (n = 10, mean age 66.3 years), who underwent abdominal surgery unrelated to intestinal motility disorders, was submitted to wholemount immunohistochemistry. The specimens were stretched out and separated into the tunica muscularis, the outer and inner portion of the tela submucosa and the tunica mucosa. Prior to the application of the neuronal marker Protein Gene Product (PGP) 9.5, the laminar preparations were pretreated with the maceration agent KOH. The plexus myentericus was composed of prominent ganglia and interconnecting nerve fiber strands (NFS) forming a polygonal network, which was denser in the descending than in the ascending colon. Nerve cells were observed within the ganglia as well as in primary, secondary and tertiary NFS. The latter ramified into the adjacent smooth muscle layers, which contained the aganglionated plexus muscularis longitudinalis and circularis. The submucous plexus comprised three nerve networks of different topography and architecture: the delicate plexus submucosus extremus consisted of parallel orientated NFS with isolated nerve cells and small ganglia and was located at the outermost border of the tela submucosa adjacent to the circular muscle layer. The plexus submucosus externus was closely associated with the plexus submucosus extremus and composed of larger ganglia and thicker NFS. The plexus submucosus internus was situated adjacent to the lamina muscularis mucosae and formed a network with denser meshes but smaller ganglia and NFS than the plexus submucosus externus. The NFS of the aganglionated plexus muscularis mucosae followed the course of the smooth muscle cells of the lamina muscularis mucosae. The honeycomb-like network of the plexus mucosus was located within the lamina propria mucosae and divided into a subglandular and a periglandular portion. Single and accumulated nerve cells were observed within the plexus mucosus as a regular feature. The findings confirm the complex structural organisation of the ENS encountered in larger mammals, in particular the subdivision of the submucous plexus into three different compartments. PGP 9.5-immunohistochemistry applied to wholemount preparations comprehensively visualized the architecture of the intramural nerve plexus in human colonic specimens. In addition to conventional cross-sections, this technique allows a subtle assessment and classification of structural alterations of the ENS in patients with colorectal motor disorders.

Morphometric aspects of the submucous plexus in whole-mount preparations of normal human distal colon

BACKGROUND/PURPOSE

The diagnosis of intestinal neuronal dysplasia (IND) has traditionally been based on the finding of hyperplasia of the submucous plexus and increased acetylcholinesterase activity in parasympathetic nerve fibers in the lamina propria. However, recently it has been suggested that proposed diagnostic criteria relating to nerve cell density may overlap with age-related changes and that the finding of giant ganglia (ganglia containing more than seven ganglion cells) is the most relevant diagnostic parameter of IND. Ganglion cell counting is usually performed on conventional histological sections, whereas the topology of whole ganglia has been poorly studied. The aim of this study was to define the number of ganglion cells per ganglion and the ganglion cell density (the number of ganglion cells per surface area) in submucous whole-mount preparations of normal human colon.

METHODS

Specimens from distal colon were obtained during postmortem examination from 14 patients who died of nongastrointestinal disease. The submucous layer was prepared as a whole mount and stained for NADPH diaphorase (a nitrergic neurotransmitter marker) and cuprolinic blue (a general neuronal marker). Ganglion cell density was estimated by counting at least 10 mm2. The number of ganglion cells per ganglion was counted in at least 20 ganglia per case.

RESULTS

Ganglion cell density (NADPH diaphorase) fell markedly during the first 5 to 6 years of life (r = -0.60, P < .05). Most ganglion cells formed ganglia of 3 to 64 cuprolinic blue staining cells. The mean number of ganglion cells per ganglion did not vary with age.

CONCLUSIONS

The density of NADPH diaphorase-positive ganglion cells in the submucous plexus of human distal colon decreases markedly with age. However, the number of ganglion cells per ganglion remains constant. These findings indicate that the age of the patient has crucial importance for the histolopathologic evaluation of enteric nervous system disorders.

Vasoactive intestinal polypeptide and nitric oxide synthase distribution in the enteric plexuses of the human colon: an histochemical study and quantitative analysis

Vasoactive intestinal polypeptide (VIP) and nitric oxide synthase (NOS) positive innervation patterns were immunohistochemically and statistically evaluated in the human colon. Specimens from the right colon (cecum, ascending and right transverse colon) and left colon (left transverse and descending colon) were obtained surgically, fixed either in paraformaldehyde or in Carnoy's or in Bouin's and paraffin embedded. Sections were stained with hematoxylin-eosin, toluidine blue, cresyl violet, neuron-specific enolase, anti-VIP, and anti-NOS. The same results were obtained regardless of the fixative used. Enolase-positive, VIP-positive, and NOS-positive cells were occasionally found within the circular muscle and interpreted as neurons. VIP-positive nerve fibers were evenly distributed within the circular muscle while NOS-positive ones were lacking in its inner portion. The left colon was richer in neurons than the right colon, at both plexuses. VIP- and NOS-positive neuron densities were higher at the left than at the right colon, whereas at all colonic levels VIP-positive neuron percentages at both plexuses and NOS-positive ones at the myenteric plexus were similar. At the submucous plexus the NOS-positive neuron percentage was lower than that of the VIP-positive one.

IN CONCLUSION

(a) the right colon contains a lower number of neurons and of VIP- and NOS-positive ones than the left colon, and (b) VIP- and NOS-positive fibers are differently distributed in the inner and outer portions of the circular muscle.

Localization of NADPH-diaphorase activity in the submucous plexus of the guinea-pig intestine: light and electron microscopic studies

The localization of reduced nicotinamide adenine dinucleotide phosphate diaphorase in the submucous plexus of duodenum, jejunum, ileum, proximal colon, distal colon and rectum in the guinea-pig was examined histochemically by light and electron microscopy. The majority of reactive submucous neurons displayed features common to either Dogiel type I or type II neurons; some were closely adherent to the outer walls of lymphatic vessels. The use of 2-(2'-benzothiazolyl)-5-styryl-3-(4'-phthalhydrazidyl) tetrazolium chloride (BSPT) at the ultrastructural level showed that nicotinamide adenine dinucleotide phosphate diaphorase is a membrane-associated protein widely distributed in the cells, including the rough endoplasmic reticulum, Golgi apparatus and synaptic vesicles in the axon terminals associated with submucous neurons. On the basis of their diaphorase reactivity or the lack of it, the submucous neuronal somata and their associated terminals were observed to form several different kinds of synaptic configurations. The present quantitative analysis showed that the frequency of reactive submucous neurons in the large intestine was significantly higher than in the small intestine. Based on the ultrastructural localization of the diaphorase reaction product in positive cells, it is speculated that nitric oxide might be synthesized within the neurons. The demonstration of different synaptic configurations in the submucous ganglia suggests that the functional interaction between submucous neurons is extremely complex. Finally, the higher frequency of diaphorase reactive submucous neurons in the large intestine than in the small intestine indicates that submucous neurons in these two gut regions may not play equivalent roles.