Colonoscopy with mucosal biopsies in young rats: A model for experimental gastroenterology

First evidence of altered microbiota and intestinal damage and their link to absence epilepsy in a genetic animal model, the WAG/Rij rat

OBJECTIVE

A large number of studies have highlighted the important role of the gut microbiota in the pathophysiology of neurological disorders, suggesting that its manipulation might serve as a treatment strategy. We hypothesized that the gut microbiota participates in absence seizure development and maintenance in the WAG/Rij rat model and tested this hypothesis by evaluating potential gut microbiota and intestinal alterations in the model, as well as measuring the impact of microbiota manipulation using fecal microbiota transplantation (FMT).

METHODS

Initially, gut microbiota composition and intestinal histology of WAG/Rij rats (a well-recognized genetic model of absence epilepsy) were studied at 1, 4, and 8 months of age in comparison to nonepileptic Wistar rats. Subsequently, in a second set of experiments, at 6 months of age, untreated Wistar or WAG/Rij rats treated with ethosuximide (ETH) were used as gut microbiota donors for FMT in WAG/Rij rats, and electroencephalographic (EEG) recordings were obtained over 4 weeks. At the end of FMT, stool and gut samples were collected, absence seizures were measured on EEG recordings, and microbiota analysis and histopathological examinations were performed.

RESULTS

Gut microbiota analysis showed differences in beta diversity and specific phylotypes at all ages considered and significant variances in the Bacteroidetes/Firmicutes ratio between Wistar and WAG/Rij rats. FMT, from both Wistar and ETH-treated WAG/Rij donors to WAG/Rij rats, significantly decreased the number and duration of seizures. Histological results indicated that WAG/Rij rats were characterized by intestinal villi disruption and inflammatory infiltrates already at 1 month of age, before seizure occurrence; FMT partially restored intestinal morphology while also significantly modifying gut microbiota and concomitantly reducing absence seizures.

SIGNIFICANCE

Our results demonstrate for the first time that the gut microbiota is modified and contributes to seizure occurrence in a genetic animal model of absence epilepsy and that its manipulation may be a suitable therapeutic target for absence seizure management.

Mucosal microbial load in Crohn's disease: A potential predictor of response to faecal microbiota transplantation

BACKGROUND

The remission of Crohn's disease (CD) can be accomplished by faecal microbiota transplantation (FMT). However, this procedure has a low success rate, which could be attributed to mis-communication between recipient intestinal mucosa and donor microbiota.

METHODS

Here we used a human explant tissue model and an in vivo mouse model to examine changes in recipient intestinal mucosa upon contact with a faecal suspension (FS) obtained from a healthy donor. CD patients provided resected inflamed and non-inflamed mucosal tissues, whereas control colonic mucosa samples were collected from colorectal cancer patients. For the models, mucosal microbiome composition and tissue response were evaluated.

FINDINGS

We show that cytokine release and tissue damage were significantly greater in inflamed compared to non-inflamed CD tissues. Moreover, mucosal samples harbouring an initial low microbial load presented a shift in composition towards that of the FS, an increase in the relative count of Faecalibacterium prausnitzii, and a higher secretion of anti-inflammatory cytokine IL-10 compared to those with a high microbial load.

INTERPRETATION

Our results indicate that FMT during active inflammatory disease can compromise treatment outcome. We recommend the stratification of FMT recipients on the basis of tissue microbial load as a strategy to ensure successful colonization.

FUNDING

This study was supported by grants from the Instituto de Salud Carlos III/FEDER (PI17/00614), the European Commission: (INCOMED-267128) and PERIS (SLT002/16). K.M. is a postdoctoral fellow and S.V. a senior clinical investigator of the Fund for Scientific Research Flanders, Belgium (FWO-Vlaanderen).

A single faecal microbiota transplantation modulates the microbiome and improves clinical manifestations in a rat model of colitis

Background

Faecal microbiota transplantation (FMT) is a novel potential therapy for inflammatory bowel diseases, but it is poorly characterised.

Methods

We evaluated the performance of the mouse and rat as a pre-clinical model for human microbiota engraftment. We then characterised the effect of a single human stool transfer (HST) on a humanised model of DSS-induced colitis. Colonic and faecal microbial communities were analysed using the 16S rRNA approach and clinical manifestations were assessed in a longitudinal setting.

Findings

The microbial community of rats showed greater similarity to that of humans, while the microbiome of mice showed less similarity to that of humans. Moreover, rats captured more human microbial species than mice after a single HST. Using the rat model, we showed that HST compensated faecal dysbiosis by restoring alpha-diversity and by increasing the relative abundance of health-related microbial genera. To some extent, HST also modulated the microbial composition of colonic tissue. These faecal and colonic microbial communities alterations led to a relative restoration of colon length, and a significant decrease in both epithelium damage and disease severity. Remarkably, stopping inflammation by removing DSS before HST caused a faster and greater recovery of both microbiome and clinical manifestation features.

Interpretation

Our results indicate that the rat outperforms the mouse as a model for human microbiota engraftment and show that the efficacy of HST can be enhanced when inflammation stimulation is withdrawn. Finally, our findings support a new therapeutic strategy based on the use FMT combined with anti-inflammatory drugs.

Evaluation of the usefulness of colonoscopy with mucosal biopsies in the follow-up of TNBS-induced colitis in rats

Animal models are required for research regarding the pathogenesis and efficacy of anti-inflammatory agents in inflammatory bowel disease (IBD). Trinitrobenzene sulfonic acid (TNBS)-induced colitis closely mimics Crohn's disease. The present study was undertaken in order to determine the reliability of following the inflammatory course of TNBS-induced colitis using colonoscopy together with biopsy samples obtained during the examination. In this study we used 20 adult male Wistar rats, with a mean weight of 201.9 g. The rats were divided into two groups, control and TNBS, with ten rats in each group. Following the induction of TNBS colitis, the rats underwent colonoscopy with mucosal biopsies. At the end of the experiment, the rats were sacrificed and whole-wall colonic samples were obtained. The degree of inflammation was assessed endoscopically, macroscopically and microscopically. There was no significant change in the body weight of the control group but significant weight loss was observed in the TNBS group. Examination of the control group did not reveal any inflammation. Severe colitis was observed in the TNBS-induced colitis rats, as assessed endoscopically, macroscopically and microscopically. The endoscopic inflammation score obtained through colonoscopy examinations correlated with that obtained macroscopically, and those obtained microscopically from the whole-wall colon and biopsy samples collected during the colonoscopy. Moreover, the inflammation scores obtained from the whole-wall colon and biopsy samples collected during colonoscopy correlated markedly. In conclusion, colonoscopy is a reliable method for following up the course of inflammation in experimentally induced colitis. Although biopsy samples collected during colonoscopies may be used to assess the degree of inflammation, whole-wall samples are superior in this regard.