Longitudinal PET/CT evaluation of TNBS-induced inflammatory bowel disease rat model

Inflammatory bowel disease (IBD) is a group of chronic disorders of the gastrointestinal tract, which two main types are Crohn's disease and ulcerative colitis. It has multifactorial etiologies, being essential the use of animal models and disease activity measures to develop new therapies. With this aim, the use of animal models in combination with non-invasive molecular imaging can play an important role in the development of new treatments. In this study, IBD was induced in rats using 2,4,6-trinitrobenzenesulfonic acid (TNBS) and longitudinal [¹⁸F]FDG PET/CT scans were conducted to assess disease progression post-TNBS administration. Afterwards, [¹⁸F]FDG PET/CT scans were carried out after treatment with methylprednisolone to validate the model. In non-treated rats, SUV_max (Standardized Uptake Value) rapidly increased after IBD induction, being particularly significant (p < 0.01) on days 7-13 after induction. There were no significant differences between non-treated and treated IBD rats from days 0-3. Nevertheless, treated IBD rats showed a significant decrease in SUV_max between days 7-13 (p < 0.01). Histological examination showed descending and transverse colon as the most affected regions. There was a moderate (R² = 0.61) and strong (R² = 0.82) correlation of SUV_max with Nancy grade (parameter for histological assessment of disease activity) and weight changes, respectively. In this study, we have performed the first longitudinal [¹⁸F]FDG PET/CT assessment of TNBS-induced IBD in rats, demonstrating the potential role of preclinical molecular imaging for the evaluation of new therapies in combination with IBD rat models.