Evaluating Therapeutic Interventions in the SHIP-deficient Mouse Model of Crohn Disease-like Ileitis and Fibrosis

Crohn disease (CD) is a chronic, relapsing inflammatory condition characterized by segmental, transmural inflammation that can affect any part of the gastrointestinal tract. A hallmark of CD is impaired intestinal barrier function, and intestinal fibrosis is a common complication. SHIP-deficient (SHIP-/-) mice spontaneously develop gut barrier dysfunction, ileal inflammation, and fibrotic pathology, recapitulating key features of CD-like ileitis. The SHIP-/- mice serve as a valuable model for testing anti-inflammatory and anti-fibrotic therapies in CD. Here, we describe methods to evaluate therapeutic interventions in this model, using dexamethasone as an example of an effective therapy. We provide a step-by-step protocol for characterizing disease and treatment response, including in vivo assessment of gut permeability measured by FITC-dextran, as well as gross pathological examination and detailed histological analyses. Histological assessments incorporate hematoxylin and eosin (H&E) staining for inflammation, Masson's trichrome staining for fibrosis, and Alcian blue/Periodic Acid-Schiff (PAS) staining for goblet cell hyperplasia and hypertrophy. Additionally, cytokines and inflammatory markers in ileal tissue are quantified to assess the inflammatory state. Together, these methods provide a comprehensive framework for evaluating treatment efficacy in the SHIP-/- mouse model of CD-like ileitis. This protocol is broadly applicable to investigators studying gut inflammation, mucosal healing, and intestinal fibrosis.