A TNBS-Induced Rodent Model to Study the Pathogenic Role of Mechanical Stress in Crohn's Disease
March 1st, 2022
The present protocol describes the development of a Crohn's-like colitis model in rodents. Transmural inflammation leads to stenosis at the TNBS instillation site, and mechanical enlargement is observed in the segment proximal to the stenosis. These changes allow studying mechanical stress in colitis.
So in our protocol, intra-colonic instillation of TNBS leads to transmural inflammation at the instillation site and the mechanical distention in the segment proximal to inflammation. So this mimics stenotic Crohn's disease. As the proximal segment is mechanically distended but does not show a visible inflammation, a comparative study of the proximal segment and the inflammation site helps to determine if mechanical stress plays a role in Crohn's colitis.
Previous studies focus on the inflammation site only. Our protocol working on different sites in the model highlights a critical role of mechanical stress in Crohn's disease, particularly in stenotic Crohn's disease. To begin, place the rats on the anesthesia table in a supine position.
To induce colitis, insert a medical-grade, open-end, polyurethane catheter through the anus for approximately seven to eight centimeters from the anal verge, and gently instill TNBS into the colon. Administer the sham control rats with 250 microliters of saline. To help the distribution of TNBS or saline and avoid spills, keep the rats in a supine position with their head facing downwards at approximately a 30-degree angle, with the anus closed for two minutes.
Open the rat abdomen using surgical-grade scissors and forceps. Carefully remove the entire colon above the anal canal, and transfer the colon immediately to ice-cold 1x HBSS buffer. Straighten the colon in the buffer, and measure the colon length using a ruler.
Take a nylon thread, and circle it around the colon to measure the external circumference of the colon segments in control and TNBS-treated rats. Take full-thickness tissues for histology. Cut open the colon along the mesenteric board, and clean the colon thoroughly with HBSS buffer.
Assess the colon for macroscopic inflammation score based on the predefined criteria with minimal modifications. Collect colonic tissue samples from TNBS-treated rats at sites P, I, and D.Site P is the portion two to three centimeters before the oral margin of the inflammation site. Site I is the inflammation site where TNBS is instilled, typically four to six centimeters from the end of the colon.
Finally, site D is the portion one to two centimeters distal to the aboral margin of the inflammation site. Intra-colonic instillation of TNBS in rats induced a localized transmural inflammation approximately two centimeters in length with thickened bowel wall and narrowed lumen in the site of instillation in the distal colon. The site of TNBS instillation was referred to as site I.As a result of transmural inflammation and stenosis, both inflammation and mechanical stress were present in site I.The stenosis in site I led to marked lumen distension in the segment proximal to the site of TNBS instillation, referred to as site P.The colon circumference was significantly increased in sites P and I compared to sham control colon.
While mechanically distended, site P did not show visible inflammation. On the contrary, the colonic segment distal to the TNBS instillation referred to as site D presented neither inflammation nor mechanical distension. The macroscopic score of inflammation in site I in the TNBS-treated rats was dramatically increased compared to sham controls in sites P and D of colitis rats.
The inflammation scores in sites P and D were not significantly increased compared to sham. So it is important to study not just site I but sites P and D in the model, as this helps to recognize the pathogenic significance of mechanical stress in Crohn's disease. To further determine if mechanical stress is a pathogenic factor in gut inflammation, one may also try to release mechanical distention by feeding the animals exclusively with liquid diet and see if this helps with inflammation and bowel function.
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Overview
This protocol outlines the development of a Crohn's-like colitis model in rodents, focusing on transmural inflammation and mechanical stress. It allows for the investigation of mechanical changes in colitis, particularly in stenotic conditions.
Key Study Components
Area of Science
- Neuroscience
- Gastroenterology
- Inflammatory Bowel Disease
Background
- Crohn's disease is characterized by transmural inflammation.
- Mechanical stress may play a significant role in disease progression.
- Previous studies have primarily focused on inflammation sites.
- This model allows for comparative studies of affected and unaffected segments.
Purpose of Study
- To develop a rodent model that mimics stenotic Crohn's disease.
- To investigate the role of mechanical stress in colitis.
- To compare mechanical changes in inflamed and non-inflamed segments.
Methods Used
- Intra-colonic instillation of TNBS to induce inflammation.
- Assessment of mechanical distention in proximal segments.
- Comparative analysis between inflamed and non-inflamed areas.
- Use of anesthesia for rodent preparation.
Main Results
- Transmural inflammation was successfully induced at the TNBS site.
- Mechanical distention was observed in the proximal segment.
- Findings suggest a critical role of mechanical stress in Crohn's disease.
- Model highlights the importance of studying different anatomical sites.
Conclusions
- The developed model is effective for studying Crohn's-like colitis.
- Mechanical stress may contribute to disease pathology.
- Future studies should explore the implications of these findings.
Frequently Asked Questions
Executive Industry Relevance
Understanding the independent role of mechanical stress in Crohn's disease pathogenesis is critical for de-risking early discovery and target validation in IBD drug development. The TNBS-induced rodent model enables precise dissection of mechanical versus inflammatory drivers, supporting predictive confidence in translational research and portfolio triage for anti-fibrotic and anti-stenotic strategies.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables interrogation of mechanical stress as an independent pathogenic factor in Crohn's disease.
- Supports functional target validation by distinguishing mechanical from inflammatory contributions to fibrosis and stenosis.
- Facilitates mechanistic de-risking for novel therapeutic hypotheses targeting tissue remodeling.
Screening & Assay Development
- Provides a validated in vivo system for quantitative assessment of gene expression, immune response, and fibrosis under defined mechanical conditions.
- Enables reproducible measurement of macroscopic inflammation and mechanical distention across anatomical sites.
- Supports assay standardization for downstream compound evaluation targeting mechanical stress pathways.
Translational & Preclinical Research
- Aligns preclinical models with disease-relevant features of Crohn's pathology, including transmural inflammation and luminal stenosis.
- Enables continuity from discovery through preclinical validation of anti-fibrotic and anti-stenotic interventions.
- Provides translational biomarker opportunities by correlating mechanical stress with gene expression and tissue remodeling.
Pipeline & Workflow Integration
This model bridges early discovery and preclinical validation by enabling hypothesis testing on mechanical stress in IBD, supporting lead identification and risk-adjusted advancement decisions.
- Discovery Biology: Dissects the pathogenic significance of mechanical stress versus inflammation in Crohn's disease.
- Screening: Delivers quantitative, site-specific readouts for inflammation, fibrosis, and mechanical distention.
- Analytics: Enables comparative analysis of gene expression and immune response across defined anatomical sites.
- Translational Research: Models clinically relevant features for preclinical evaluation of anti-fibrotic strategies.
- Enterprise Reuse: Establishes a reusable platform for mechanistic studies and compound screening in IBD research.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence in target validation and mechanistic de-risking for Crohn's disease.
- Operational Value: Standardizes in vivo assessment of mechanical and inflammatory drivers in IBD models.
- Strategic Value: Informs go/no-go decisions for anti-fibrotic and anti-stenotic drug candidates.
- Portfolio Impact: Supports risk-adjusted prioritization of discovery and preclinical assets targeting tissue remodeling.
Implementation Considerations
- Requires expertise in rodent surgical procedures and colitis modeling.
- Demands access to histological, molecular, and macroscopic analytical infrastructure.
- Necessitates cross-team standardization of inflammation scoring and tissue sampling protocols.
- Adaptation may be needed for other rodent strains or IBD-relevant models.
- Mechanical stress quantification is limited to defined anatomical sites and may not capture systemic effects.
