DSS Colitis and TNBS Colitis Models: An Overview

August 14, 2023 /

Inflammatory Bowel disease (IBD) is a multifaceted and polygenic disorder that is characterized by persistent inflammation in the GI tract. It encompasses two primary phenotypes (Ulcerative Colitis and Crohn’s disease). Attaining a comprehensive insight into the intricate mechanisms and the pathogenesis of IBD is of paramount importance for the development of efficacious therapeutic interventions. In this context, animal models have emerged as indispensable tools, playing a major role in both the advancement of and the understanding of IBD. The establishment of both robust and reliable animal models has made significant contributions to giving us a better insight into the complexities of IBD. These models enable the simulation of the intricate interplay between genetic predisposition, environmental factors, and dysregulated immune responses, which collectively contribute to the initiation and the development of the disease process. By providing a controlled experimental environment, animal models facilitate the systematic investigation of the fundamental pathogenic mechanism underlying IBD and serve as platforms for the evaluation of potential therapeutic modalities. Among the plethora of animal models available for studying IBD, two stand out: The Dextran Sodium Sulfate (DSS) colitis model, and the 2,4,6-trinitrobenzenesulfonic acid (TNBS) colitis model.

 

Overview of IBD

Inflammatory bowel disease stands as a perplexing and intricate medical condition posing a significant challenge to medical professionals and researchers alike1. This chronic inflammatory disorder involves a complex interplay of genetic, environmental, and immunological factors within the gastrointestinal tract leading to sustained inflammation and tissue damage1. The immune system’s dysregulated responses further contribute to the pathophysiology of IBD, perpetuating the disease’s chronicity. Patients afflicted with IBD endure a range of distressing symptoms including persistent abdominal pain, frequent diarrhea, unintended weight loss, and fatigue, significantly impairing their quality of life. Despite significant advancements in medical knowledge and therapeutic options, current treatments for IBD remain predominantly focused on symptom management and reducing inflammation rather than achieving a cure1. Immunosuppressants, corticosteroids, and biological therapies targeting specific cytokines are among the treatments commonly employed. However, these therapeutic approaches often carry adverse effects and may not provide sustained remission or long-term relief of patients1. To address the complexity of IBD and improve patient outcomes, researchers are dedicatedly delving into the disease’s underlying mechanisms2. The role of gut microbiota, immune cell pathways, and intricate inflammatory cascades is being extensively investigated to identify potential therapeutic targets2. Advancements in pharmacology and precision medicine offer promising avenues for more tailored and effective treatments aiming to restore the disrupted immune responses and achieve sustained remission for IBD patients.

 

DSS Colitis Model

The DSS Colitis model is a well-established and widely used experimental approach to better study and understand the acute phase of IBD in rodents. The induction protocol involves the administration of dextran sodium sulfate (DSS), a sulfated polysaccharide, in the drinking water of experimental animals. DSS exposure leads to colonic epithelial injury and disruption of the gut barrier function, triggering an inflammatory response3.

Researchers can modulate the severity of colitis in this model by adjusting the concentration and duration of DSS exposure. Shorter exposure durations generally induce milder inflammation, while longer exposures lead to more severe and sustained colitis. This allows for the study of various disease stages and the evaluation of therapeutic interventions at different time points during the inflammatory process. The DSS colitis model is commonly employed in mice and rats, with the C57BL/6 mouse strain being one of the most frequently used due to its well-characterized immune response. The model’s induction is relatively straightforward reproducible, making it an attractive choice for researchers investigating the early stages of IBD.

Clinically, researchers assess disease progression in DSS-treated animals by monitoring various parameters, such as body weight loss, stool consistency, and the presence of rectal bleeding. Additionally, histological examination of colonic tissue samples allows researchers to study the extent of mucosal damage, inflammatory cell infiltration, goblet cell depletion, and other key features characteristic of IBD pathology4.

 

TNBS Colitis Model

The TNBS colitis model is another widely used experimental approach employed to study the chronic phase of IBD. In this model trinitrobenzene sulfonic acid (TNBS) is typically dissolved in ethanol and instilled directly into the colon, leading to a T-cell-mediated immune response and inducing a delayed hypersensitivity reaction. This results in chronic inflammation and tissue injury in the colon5. Similar to the DSS model, the severity of colitis in the TNBS model can be controlled by adjusting the concentration and volume of TNBS instillation.

The model is commonly conducted in rats, such as the Wistar or Lewis strains, and mice, including the BALB/c and C57BL/6 strains. The strains have been extensively characterized in IBD research, providing valuable insights into the inflammatory responses seen in both acute and chronic phases of the disease. TNBS colitis model researchers assess disease severity by monitoring weight loss, disease activity index, and the occurrence of diarrhea. Additionally, histopathological analysis of colon sections allows for the examination of immune cell infiltration,  granuloma formation, and  transmural inflammation, which are key features observed in IBD patients particularly those with Crohn’s disease6.

 

Historic Overview of the DSS Colitis Model

The DSS Colitis model has a relatively recent history with its development and application dating back to the late 1980s and early 1990s. The model was initially introduced by Okayasu and colleagues in 1989 as another method to induce acute and chronic ulcerative colitis in mice3. The researchers recognized the need for a reproducible and reliable experimental model that could mimic the characteristics of human ulcerative colitis. To achieve this the utilized dextran sodium sulfate (DSS), a sulfated polysaccharide known for its pro-inflammatory effects on the colonic epithelium. Over the years the DSS colitis model has undergone refinement and optimization, becoming a widely used and well-established experimental tool in IBD research. Its versatility, reproducibility, and ability to simulate the acute phase of colitis make it valuable for studying the initial inflammatory events and assessing potential therapeutic interventions.

 

Histopathology Slide from UC Patient

 

Historic Overview of the TNBS Colitis Model

The TNBS Colitis model has a longer history, dating back to the 1960s, when researchers were exploring the immune mechanisms underlying hypersensitivity reactions. Trinitrobenzene sulfonic acid (TNBS) was initially used as a hapten to study delayed-type hypersensitivity in rodents5. In the late 1980s, researchers recognized the potential of TNBS as a colitis-inducing agent, leading to its application in the study of Inflammatory Bowel Disease. By administering TNBS into the colons of experimental animals, researchers could elicit a delayed-type hypersensitivity reaction, triggering chronic colitis and granulomatous inflammation. As the TNBS model was further investigated and characterized, researchers identified its relevance for studying fibrosis, a hallmark feature of IBD. The model offered insights into the fibrotic processes observed in Crohn’s disease, contributing to a more comprehensive understanding of IBD pathology.

 

DSS Colitis and TNBS Colitis V/S Other Models

The DSS colitis model and TNBS colitis model are valuable tools for studying Inflammatory Bowel Disease (IBD), but they are not the only experimental models used for this indication. Other models, such as the IL-10 knockout model and the adoptive T cell transfer model, have also been employed in IBD research. Each model offers unique advantages and focuses on different aspects of IBD pathology. As mentioned previously, the DSS colitis model and TNBS colitis model primarily represent chemically-induced models, involving the administration of DSS or TNBS to induce acute or chronic colitis, respectively. These models allow for the investigation of gut inflammation, immune cell infiltration, and tissue damage, making them well-suited for understanding the early and chronic stages of IBD. In contrast, the IL-10 knockout model mimics the genetic component of IBD, as IL-10 plays a pivotal role in maintaining intestinal homeostasis. The absence of IL-10 leads to spontaneous colitis in mice, resembling the chronic and relapsing nature of IBD in humans. This model is particularly useful for studying the role of immune dysregulation and the contribution of genetic factors to IBD development. The adoptive T cell transfer model focuses on immune cell-mediated inflammation. In this model, T cells isolated from mice with colitis are transferred into immunocompromised recipient mice, resulting in colitis development. Researchers can investigate the pathogenicity of specific T cell populations and study immune cell interactions and signaling pathways associated with IBD.

 

Best Practices for DSS Colitis Model

 

  • Standardization: Use standardized DSS concentration and administration protocols to ensure consistency in results across experiments. Consider factors such as animal strain, DSS concentration, duration of exposure, and water restriction carefully.
  • Animal Welfare: Monitor the health and welfare of experimental animals regularly. Assess and record parameters such as body weight, stool consistency, and the presence of rectal bleeding throughout the study period.
  • Water and Food Access: Ensure access to regular drinking water and a balanced diet for animals not receiving DSS treatment. Ad libitum access to water and food should be restored after DSS treatment to promote recovery.
  • Cage Conditions: Maintain optimal cage conditions, including appropriate temperature, humidity, and light cycles, to minimize stress and promote the well-being of experimental animals.
  • Randomization and Blinding: Randomize the assignment of animals to experimental groups and employ blinding during data collection and analysis to reduce bias and increase the reliability of results.
  • Sample Collection: Collect tissue samples consistently and systematically from the same regions of the colon to ensure accurate comparison and analysis between experimental groups.
  • Ethical Considerations: Adhere to ethical guidelines and obtain proper approval from the institutional animal ethics committee before conducting any experiments involving animals.

 

Best Practices for TNBS Colitis Model

  • TNBS Preparation: Prepare TNBS solutions freshly and with precision to ensure the stability and accuracy of the colitis induction process.
  • Ethanol Content: Use an appropriate amount of ethanol as a vehicle for dissolving TNBS to avoid potential non-specific effects of ethanol on the colonic tissue.
  • Dosage: Administer TNBS at the appropriate dosage to elicit a robust immune response and induce colitis consistently.
  • Animal Strain: Choose animal strains that are responsive to TNBS induction and have established literature support for colitis development.
  • Sterile Technique: Practice strict sterile techniques during TNBS administration and tissue sampling to minimize contamination and potential confounding factors.
  • Control Groups: Include suitable control groups, such as vehicle-treated or untreated animals, to provide a baseline comparison for TNBS-induced colitis.
  • Monitoring: Monitor animals closely for signs of colitis, such as body weight loss, stool consistency, and the presence of diarrhea or rectal bleeding, throughout the study.
  • Endpoint Consideration: Determine the appropriate endpoint for the study based on the research question, as TNBS colitis can manifest in various degrees of severity and duration.

 

FAQ

  1. What are the key differences between the DSS colitis model and the TNBS colitis model in studying IBD?

The DSS Colitis model is induced by administering DSS orally in the drinking water, causing human ulcerative colitis-like pathologies due to its damaging effect on the colonic epithelial barrier. The inflammation resulting from DSS administration is more evenly distributed throughout the colon, primarily affecting the mucosal layer. This model activates innate immune responses, leading to a neutrophil-dominated inflammation.

On the other hand, the TNBS-induced colitis model involves a single intrarectal instillation of the haptenizing molecule TNBS. This model is commonly utilized and shares significant properties with human Crohn’s disease. In TNBS colitis, the inflammation tends to be more localized and is often concentrated in specific segments of the colon. The inflammation affects multiple layers of the colon wall, including the mucosa, submucosa, and muscularis. Additionally, this model triggers both innate and adaptive immune responses, involving T cells, cytokines, and antibodies.

Researchers often choose between these two models based on their research objectives and the aspects of IBD they wish to study. DSS Colitis is suitable for simulating ulcerative colitis-like pathologies and studying the effects of inflammation in a more widespread manner. TNBS-induced colitis, on the other hand, is preferred when investigating localized and more chronic inflammatory responses akin to Crohn’s disease. Combining both models can provide a more comprehensive understanding of IBD and contribute to a better characterization of potential therapeutic interventions.

  1. Can the DSS colitis and TNBS colitis models be used to study specific subtypes of IBD, such as Crohn’s disease or ulcerative colitis?

While the DSS colitis model and TNBS colitis model primarily induce colitis, they have distinct pathological characteristics that resemble specific subtypes of IBD. The DSS colitis model is more commonly associated with ulcerative colitis due to its primarily colonic involvement and superficial inflammation. Conversely, the TNBS colitis model is frequently used to study aspects of Crohn’s disease, given its capacity to induce granulomatous inflammation and transmural colonic lesions. However, it is essential to recognize that these models represent simplifications of the complex spectrum of IBD, and results should be interpreted with consideration of the specific research question.

  1. How can researchers address inter-individual variability observed in the DSS colitis and TNBS colitis models?

Inter-individual variability is inherent in animal models, including the DSS colitis and TNBS colitis models. To minimize its impact, researchers should adopt rigorous experimental design with appropriate sample sizes, randomization, and blinding. Ensuring that animals within each experimental group are from the same source and age and standardizing housing conditions can also help mitigate variability. Moreover, the inclusion of relevant control groups allows researchers to distinguish treatment effects from natural variations in disease severity.

  1. What are the limitations of using the DSS colitis and TNBS colitis models in IBD research?

Both models have limitations that researchers should be aware of. The DSS colitis model does not fully replicate the chronic and transmural features seen in Crohn’s disease. The TNBS colitis model may induce severe inflammation, leading to animal morbidity and ethical concerns. Additionally, species differences should be considered when translating results to human patients. The models may not capture the complex interplay between genetic susceptibility, environmental factors, and the gut microbiota that contribute to IBD pathogenesis in humans.

  1. Can the DSS colitis and TNBS colitis models be used to study the efficacy of novel biologics and immunomodulatory agents?

Yes, both models are highly relevant for studying the effects of novel biologics and immunomodulatory agents in IBD research. These models allow researchers to investigate the impact of targeted therapies on immune cell populations, cytokine profiles, and gut barrier function during acute and chronic colitis. By evaluating the modulation of inflammatory responses and tissue damage, researchers can identify potential candidates for further preclinical and clinical development.

  1. Can the DSS colitis and TNBS colitis models be used to investigate the long-term effects of potential treatments in IBD?

Yes, both models can be adapted for long-term studies to assess the sustained effects of potential treatments in IBD. Researchers can administer therapeutic agents during the induction phase and continue treatment throughout the course of colitis development. By monitoring disease progression over an extended period, researchers can evaluate the durability and efficacy of the interventions in mitigating inflammation and promoting tissue repair.

  1. What are some key considerations for data analysis when using the DSS colitis and TNBS colitis models?

Proper data analysis is crucial when working with the DSS colitis and TNBS colitis models. Researchers should employ appropriate statistical tests to determine the significance of differences between experimental groups. Careful consideration should be given to selecting relevant endpoints, such as histopathological scoring, cytokine levels, and molecular markers, and to choosing the appropriate timepoints for data collection. Inflammation and recovery may follow different patterns over time, so capturing data at multiple timepoints can provide a more comprehensive view of the disease process. Additionally, incorporating adequate sample size calculations and assessing for outliers will enhance the robustness and reliability of the study results.

  1. Can the DSS colitis and TNBS colitis models be used to study the role of the gut-brain axis in IBD pathogenesis?

Yes, these models provide opportunities to explore the bidirectional communication between the gut and the brain, known as the gut-brain axis, in IBD research. Researchers can investigate the effects of stress, anxiety, and neural signaling on gut inflammation and immune responses in the DSS colitis and TNBS colitis models. By assessing neural pathways and neurotransmitter systems, researchers can gain insights into the neuroimmune interactions involved in IBD progression and the potential for neuroimmune-targeted therapies.

 

 

References

  1. Neurath MF. 2018. New targets for mucosal healing and therapy in inflammatory bowel diseases. Mucosal Immunology, 11(3), 5-17.
  2. Pastorelli L, et al. 2017. New Insights into IBD Pathogenesis: Intestinal Microbiota, IL-17, and Gut Macrophages. Inflammatory Bowel Diseases, 23(8), 1494-1503.
  3. Okayasu I, et al. 1990. A novel method in the induction of reliable experimental acute and chronic ulcerative colitis in mice. Gastroenterology, 98(3), 694-702.
  4. Chassaing B, et al. 2014. Dextran sulfate sodium (DSS)-induced colitis in mice. Current Protocols in Immunology, 104, 15.25.1-15.25.14.
  5. Morris GP, et al. 1989. Hapten-induced model of chronic inflammation and ulceration in the rat colon. Gastroenterology, 96(3), 795-803.
  6. Morrissey PJ, et al. 1993. Murine TNF receptors: differential intracellular fate for p55 and p75. Journal of Immunology, 151(1), 427-434.