Q28 - Quantification of Structural Remodeling in the Normal and Inflamed Mouse Colon

Saturday, October 11, 2025

10:00 AM - 11:00 AM PDT

Location: Exhibit Hall F, G & H

Presenting Author(s)

PW

Piper Welsh

Student
The University of Texas at Dallas, United States

Co-Author(s)

CC

Chastity Chavez

PhD Student
The University of Texas at Dallas, United States

Primary Investigator(s)

Jacopo Ferruzzi

Assistant Professor
University of Texas at Dallas
Richardson, Texas, United States

Introduction: : Inflammatory bowel disease (IBD), specifically Ulcerative Colitis (UC) and Crohn’s Disease, can be described as excessive immune responses resulting in tissue damage and loss of function [1]. Prior studies have shown that such an inflammatory response causes a wound-healing effect aimed at restoring tissue structure by reorganizing the extracellular matrix (ECM), a process known as ECM remodeling [2]. ECM remodeling targets key structural constituents such as fibrillar collagen which, in turn, results in disparate changes in colorectal tissue structure, including heterogenous thickening and thinning of the colonic wall [3,4]. Yet, it remains unknown how IBD influences the local thickness and microstructure regionally along the length of the colon. In fact, the colon is a layered structure in which the thickness and composition of the inner (mucosa and submucosa) and outer (muscularis) layers is optimized to accomplish the main physiological functions of the large intestine. Tracking these structural changes in a regionally heterogeneous fashion is of particular importance, as they are likely associated with maladaptive changes in tissue function and development of clinical symptoms during IBD progression. Therefore, this work explores regional heterogeneities in colonic tissue structure and composition using healthy mice and a Dextran-Sodium Sulfate (DSS) mouse model of IBD. Overall, this work highlights the importance of acknowledging regional heterogeneities in response to IBD as a guide for the development of therapeutic applications [5].

Materials and

Methods: : For the healthy (baseline) mouse model, 12-week-old C57BL/6 male mice were euthanized, and the colon was harvested. Another cohort of mice in the DSS model were given concentrations of either 0%, 2.5%, or 5% DSS in their drinking water to induce acute colitis. After 5 days of DSS treatment, animals were euthanized and the colon was harvested. The colon was then sectioned into four regions of equal length: two proximal (P1 and P2) and two distal (D1 and D2). Each region underwent biaxial biomechanical mechanical testing after which we quantified the unloaded thickness of two load-bearing structures (the mucosa and the muscularis) to determine the influence of inflammation on structural damage. To do this, a ring was isolated from the region and imaged using a dissection microscope equipped with a calibrated camera. The resulting images were analyzed using a custom MATLAB code [6] where the perimeters of each of the layers were identified and the area was calculated. The rest of the tissue from the same colonic region was placed in 10% formalin before being embedded in paraffin wax. The samples were sectioned at 5 µm thicknesses and stained with Picrosirius Red (PSR) to quantify regional collagen content. The stained samples were imaged with both brightfield and polarized light imaging to identify the collagen content compared to the total sample area.

Results, Conclusions, and Discussions:: We examined regional load-bearing layer thicknesses and regional collagen content to investigate how the local structure and collagen remodeling are affected regionally by IBD. For the baseline model (0% DSS), the D1 region is significantly thinner than the other regions for both the mucosa (Figure 1, left) and the muscularis (Figure 1, right) layers. Following this, mucosal thinning occurs in proximal regions as DSS concentrations increase, while the distal regions are not impacted (Figure 1, left). The muscularis layer shows mild changes in colonic wall thickness as the DSS concentration increases (Figure 1, right). Furthermore, preliminary analysis of PSR sections captured by polarized light imaging suggests the presence of lower collagen content signal for the middle regions (P2 and D1) in the baseline model (data not shown) and a decrease in collagen content signal for the D2 region as the DSS concentration increases (Figure 2).

Despite some recent advances in the field, much remains to be done in terms of defining how tissue remodeling and biomechanical function are implicated in the progression of IBD. Here, we present how IBD affects regionally the thickness of the main load-bearing colonic layers and the associated changes in tissue microstructure. Ongoing work is aimed at studying how these structural changes associate with biomechanical changes, with the goal of understanding how the local structural properties relate to the overall tissue (dys)function in IBD.

By analyzing layer thickness and collagen content regionally in healthy and inflamed tissues, this work demonstrates that the normal mouse colon is structurally heterogenous and is differentially impacted by IBD, with the proximal colon undergoing mucosal thinning and the distal colon undergoing collagen remodeling.

Acknowledgements and/or References (Optional): : We thank Dr. Leonidas Bleris for providing animals used in preliminary experiments. We also thank Soto Kubo for his contribution in initiating the study and Dr. Christy Gliniak and Dr. Philipp Scherer from the UT Southwestern Touchstone Diabetes Center for assisting with the DSS murine model. This project was partially funded by The University of Texas at Dallas Office of Research and Innovation through the CoBRA program.

[1] Laiyemo A.O. et al., Best Prac Res Clin Gastroenterol, 28(4), 655–663, 2014.
[2] Shimshoni, E. et al., Gut, 64(3), 367–372, 2015.
[3] Stewart, D.C. et al., PLoS One, 13(7), e0200377, 2018.
[4] Shimshoni, E. et al., Matrix Biol, 96, 47–68, 2018.
[5] Villablanca, E.J. et al., Nat Rev Gastroenterol Hepatol, 19(8), 493–507, 2022.
[6] Ferruzzi, J. et al., Ann Biomed Eng, 41(7), 1311–1330, 2013.