A Novel Mouse Model To Study Primary Sclerosing Cholangitis Associated Inflammatory Bowel Disease

Background: - Primary sclerosing cholangitis (PSC) is a form of liver fibrosis affecting the biliary network often leading to cholangiocarcinoma. PSC is rarely diagnosed, but 70% of PSC patients develop inflammatory bowel disease (IBD), leading to a condition called PSC-associated IBD (PSC-IBD), with a high risk of developing colorectal cancer. Unfortunately, the cause and underlying mechanisms of PSC-IBD are not understood. One of the reasons for this lack of knowledge is the dearth of animal models to study PSC-IBD, which our study focuses on. FVB/NJ mice deficient in ATP-binding cassette subfamily b member 4 ( Abcb4 KO) develop PSC by 12 weeks of age. ABCB4 is a hepatocyte transporter of phosphatidylcholine (PC) into the bile, which constitutes 90% of all bile phospholipids and forms micelles that carry bile salts. Absence of ABCB4 depletes bile PC, allowing bile salts to erode the lining of the biliary tree, causing hepatitis, followed by PSC. Our lab has established anti-interleukin 10 receptor monoclonal antibody (anti-IL10R mAb) treatment to induce chronic colitis, which mimics Crohn’s disease in humans. We hypothesized that inducing colitis in Abcb4 KO mice by IL10R neutralization in the gut could serve as a novel model of PSC-IBD. Methods: - We injected wild type (WT) and Abcb4 KO male mice, 8 weeks old, with 1.0 mg of anti-IL10R mAb/mouse/week intraperitoneally for 4 weeks, followed by euthanasia at week 5. Respective controls were injected with 1.0 mg of isotype IgG. We harvested serum for biochemical analysis of inflammatory cytokines, along with gall bladder, liver, and colon to determine biochemical and histology markers of liver and colon pathology. Results - Abcb4 KO mice had diminished bile phospholipids compared to WT mice (WT- 162.7±43.4 mg/dL vs Abcb4 KO- 22.5±14.9 mg/dL; p <0.05). Abcb4 KO mice suffer from cholemia (WT- 2.1±0.1 μM vs Abcb4 KO- 21.4±2.3 μM; p <0.01), and transaminitis, as indicated by greater alanine transaminase (WT- 22.0±5.7 U/L vs Abcb4 KO- 57.0±5.5 U/L; p <0.001). After treatment with anti-IL10R mAb, Abcb4 KO mice had greater circulating inflammatory markers such as lipocalin 2 (treated WT- 130.5±34.6 ng/mL vs treated Abcb4 KO- 781.6±209.1 ng/mL; p <0.05). Moreover, Abcb4 KO mice suffered from liver fibrosis as seen after Masson’s trichrome staining of liver sections. However, treated Abcb4 KO and WT mice had comparable levels of serum immunoreactivity to flagellin (treated WT- 1.17±0.22 vs treated Abcb4 KO- 1.06±0.09; p >0.9) and lipopolysaccharide (treated WT- 0.13±0.06 vs treated Abcb4 KO- 0.08±0.03; p >0.7). Moreover, both groups had comparable relative expression of colonic inflammatory cytokines such as KC (treated WT- 36.1±14.9 vs treated Abcb4 KO- 46.1±6.0; p >0.8), IL-6 (treated WT- 24.5±12.9 vs treated Abcb4 KO- 25.7±4.9; p >0.9), IL-17 (treated WT- 25.4±15.6 vs treated Abcb4 KO- 30.9±7.0; p >0.9), and IL-1β (treated WT- 3.8±1.9 vs treated Abcb4 KO- 10.9±3.8; p >0.5), and colonic myeloperoxidase activity (treated WT- 1.0±0.3 U/g colon vs treated Abcb4 KO- 1.4±0.2 U/g colon; p >0.5). Furthermore, colonic histology and Alcian blue staining indicated comparable tissue damage and mucin depletion in treated Abcb4 KO and WT mice. Conclusion:- Abcb4 KO mice treated with anti-IL10R mAb developed robust systemic inflammation compared to similarly treated WT mice, but comparable colitis as indicated by serum and colonic expression of inflammatory markers and histology. We posit that the greater circulating lipocalin 2 is a systemic response to PSC and IBD together. Further studies are warranted to understand the disparity in systemic and colonic expression of inflammatory markers. This model can be used to further investigate the underlying mechanism leading to PSC-IBD. M. Vijay-Kumar is supported by National Institutes of Health grants RO1 CA219144 and RO1 DK134053. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.