The enteric serotonergic system is altered in patients with diverticular disease.

OBJECTIVE: Disturbances of the enteric serotonergic system have been implicated in several intestinal motility disorders. Patients with diverticular disease (DD) have been reported to exhibit abnormal intestinal motility and innervation patterns. Gene expression profiles of the serotonergic system and distribution of the serotonin type 4 receptor (5HT-4R) were thus studied in patients with DD. DESIGN: Colonic specimens from patients with DD and controls were subjected to quantitative PCR for serotonin receptors 2B, 3A, 4, serotonin transporter and synthesising enzyme tryptophan hydroxylase. Localisation of 5HT-4R was determined by dual-label immunocytochemistry using smooth muscle actin (α-SMA) and pan-neuronal markers (PGP 9.5) and quantitative analysis was carried out. Site-specific gene expression analysis of 5HT-4R was assessed within myenteric ganglia and muscle layers. Correlation of 5HT-4R with muscarinic receptors 2 and 3 (M2R, M3R) messenger RNA expression was determined. RESULTS: 5HT-4R mRNA expression was downregulated in the tunica muscularis and upregulated in the mucosa of patients with DD, whereas the other components of the serotonergic system remained unchanged. 5HT-4R was detected in ganglia and muscle layers, but was decreased in the circular muscle layer and myenteric ganglia of patients with DD. 5HT-4R mRNA expression correlated with M2R/M3R mRNA expression in controls, but not in patients with DD. CONCLUSIONS: The serotonergic system is compromised in DD. Altered expression of 5HT-4R at mRNA and protein levels may contribute to intestinal motor disturbances reported in patients with DD. The findings support the hypothesis that DD is associated and possibly promoted by an enteric neuromuscular pathology.

Expression pattern and localization of alpha-synuclein in the human enteric nervous system.

BACKGROUND: Alpha-synuclein (α-syn) is abundantly expressed in the central nervous system and involved in the regulation of neurotransmission. Insoluble fibrils of phosphorylated α-synuclein (p-α-syn) have been implicated in several neurodegenerative diseases (e.g. Parkinson's disease, Alzheimer's disease). The aim of the study was to determine the gene expression pattern and localization of α-syn/p-α-syn in the human enteric nervous system (ENS). METHODS: Human colonic specimens (n=13, 15-83 years) were processed for α-syn and p-α-syn immunohistochemistry. Colocalization of α-syn was assessed by dual-labeling with pan-neuronal markers (PGP 9.5, HuC/D). For qPCR studies, tissue was obtained from full-thickness sections, tunica muscularis, submucosa, mucosa, and laser-microdissected (LMD) enteric ganglia. RESULTS: Highest α-syn levels were detectable within the tunica muscularis and submucosa. Ganglia isolated by LMD showed high expression of α-syn mRNA. All myenteric and submucosal ganglia and nerve fibers were immunoreactive for α-syn. Dual-labeling revealed colocalization of α-syn with both pan-neuronal markers. p-α-syn immunoreactivity was consistently observed in specimens from adults with increasing age. CONCLUSIONS: α-syn is abundantly expressed in all nerve plexus of the human ENS including both neuronal somata and processes. The presence of p-α-syn within the ENS is a regular finding in adults with increasing age and may not be regarded as pathological correlate. The data provide a basis to unravel the functions of α-syn and to evaluate altered α-syn in enteric neuropathies and α-synucleinopathies of the CNS with gastrointestinal manifestations.

Deep pelvic anatomy revisited for a description of crucial steps in extralevator abdominoperineal excision for rectal cancer.

BACKGROUND: Extralevator abdominoperineal excision results in superior oncologic outcome for advanced low rectal cancer. The exact definition of surgical resection planes is pivotal to achieving negative circumferential resection margins. OBJECTIVE: This study aims to describe the surrounding anatomical structures that are at risk for inadvertent damage during extralevator abdominoperineal excision. DESIGN AND SETTING: Joint surgical and macroanatomical dissection was performed in a university laboratory of clinical anatomy. METHODS: A stepwise dissection study was conducted according to the technique of extralevator abdominoperineal excision by abdominal and perineal approaches in 4 human cadaveric pelvises. Muscular, fascial, tendinous, and neural structures were carefully exposed and related to the corresponding surgical resection planes. RESULTS: In addition to the autonomic nerves to be identified and preserved during total mesorectal excision, further structures endangered during extralevator abdominoperineal excision can be clearly identified. Terminal pudendal nerve branches come close to the surgical resection plane at the outer surface of the puborectal sling. Likewise, the pelvic plexus and its neurovascular bundles embedded within the parietal pelvic fascia extend close to the apex of the prostate where the parietal pelvic fascia has to be divided. These neural structures converge in the region of the perineal body, an area that provides no "self-opening" planes for surgical dissection. Thus, the necessity to sharply detach the anorectal specimen anteriorly from the perineal body and the superficial transverse perineal muscle bears the risk of both inadvertent damage of the aforementioned anatomical structures and perforation of the specimen. LIMITATIONS: The study focused primarily on the macroscopic topography relevant to the surgical procedure, so that previously published histologic examinations were not performed. CONCLUSION: The present anatomical dissection study highlights those anatomical landmarks that require clear identification for the successful achievement of both negative circumferential resection margins and preservation of urogenital functions during extralevator abdominoperineal excision.

Morphological alterations of the enteric nervous system in young male patients with rectal prolapse.

OBJECTIVES: The pathogenesis of rectal prolapse (RP) defined by a circumferential, full-thickness invagination of the rectal wall into the anal canal is controversial. RP is normally encountered in elderly women and attributed to several etiological factors (e.g., advanced age, pudendal nerve injury, laxity of supporting ligaments). RP affecting young male patients is unlikely to be explained by these factors and may be due to a rectal motility disorder. Therefore, the enteric nervous system (ENS) as key regulator of intestinal motility was evaluated by a systematic morphometric analysis. PATIENTS AND METHODS: Full-thickness rectosigmoid specimens obtained from young male patients with symptomatic RP (n = 5) and male controls (n = 15) were processed for conventional histology and immunohistochemistry using anti-HuC/D as pan-neuronal marker. Enteric ganglia, nerve and glial cells were quantified separately in the myenteric (MP) and submucosal plexus (SMP). RESULTS: Compared to controls, patients with RP showed significantly (p < 0.05) increased mean ganglionic area both in MP and SMP, increased mean neuronal content of submucosal ganglia, and nearly threefold higher frequency of submucosal ganglia containing ≥7 neurons. CONCLUSION: The morphometric analysis reveals distinct quantitative alterations of the ENS in young male patients with RP mainly characterized by submucosal hyperganglionosis similar to histopathological features described in intestinal neuronal dysplasia. The data give evidence that RP in this unusual subgroup is associated with morphological changes of enteric ganglia which may contribute to the development of RP and complement established etiological concepts.

Distinct pattern of enteric phospho-alpha-synuclein aggregates and gene expression profiles in patients with Parkinson's disease.

Phosphorylated alpha-synuclein (p-α-syn) containing Lewy bodies (LBs) and Lewy neurites (LNs) are neuropathological hallmarks of Parkinson's disease (PD) in the central nervous system (CNS). Since they have been also demonstrated in the enteric nervous system (ENS) of PD patients, the aim of the study was to analyze enteric p-α-syn positive aggregates and intestinal gene expression. Submucosal rectal biopsies were obtained from patients with PD and controls and processed for dual-label-immunohistochemistry for p-α-syn and PGP 9.5. p-α-syn positive aggregates in nerve fibers and neuronal somata were subjected to a morphometric analysis. mRNA expression of α-syn and dopaminergic, serotonergic, VIP (vaso intestinal peptide) ergic, cholinergic, muscarinergic neurotransmitter systems were investigated using qPCR. Frequency of p-α-syn positive nerve fibers was comparable between PD and controls. Although neuronal p-α-syn positive aggregates were detectable in both groups, total number and area of p-α-syn positive aggregates were increased in PD patients as was the number of small and large sized aggregates. Increased expression of dopamine receptor D1, VIP and serotonin receptor 3A was observed in PD patients, while serotonin receptor 4 and muscarinic receptor 3 (M3R) were downregulated. M3R expression correlated negative with the number of small sized p-α-syn positive aggregates. The findings strengthen the hypothesis that the CNS pathology of increased p-α-syn in PD also applies to the ENS, if elaborated morphometry is applied and give further insights in altered intestinal gene expression in PD. Although the mere presence of p-α-syn positive aggregates in the ENS should not be regarded as a criterion for PD diagnosis, elaborated morphometric analysis of p-α-syn positive aggregates in gastrointestinal biopsies could serve as a suitable tool for in-vivo diagnosis of PD.

The GDNF System Is Altered in Diverticular Disease - Implications for Pathogenesis.

BACKGROUND & AIMS: Absence of glial cell line-derived neurotrophic factor (GDNF) leads to intestinal aganglionosis. We recently demonstrated that patients with diverticular disease (DD) exhibit hypoganglionosis suggesting neurotrophic factor deprivation. Thus, we screened mRNA expression pattern of the GDNF system in DD and examined the effects of GDNF on cultured enteric neurons. METHODS: Colonic specimens obtained from patients with DD (n = 21) and controls (n = 20) were assessed for mRNA expression levels of the GDNF system (GDNF, GDNF receptors GFRα1 and RET). To identify the tissue source of GDNF and its receptors, laser-microdissected (LMD) samples of human myenteric ganglia and intestinal muscle layers were analyzed separately by qPCR. Furthermore, the effects of GDNF treatment on cultured enteric neurons (receptor expression, neuronal differentiation and plasticity) were monitored. RESULTS: mRNA expression of GDNF and its receptors was significantly down-regulated in the muscularis propria of patients with DD. LMD samples revealed high expression of GDNF in circular and longitudinal muscle layers, whereas GDNF receptors were also expressed in myenteric ganglia. GDNF treatment of cultured enteric neurons increased mRNA expression of its receptors and promoted neuronal differentiation and plasticity revealed by synaptophysin mRNA and protein expression. CONCLUSIONS: Our results suggest that the GDNF system is compromised in DD. In vitro studies demonstrate that GDNF enhances expression of its receptors and promotes enteric neuronal differentiation and plasticity. Since patients with DD exhibit hypoganglionosis, we propose that the observed enteric neuronal loss in DD may be due to lacking neurotrophic support mediated by the GDNF system.