Molecular Imaging in Preclinical Models of IBD with Nuclear Imaging Techniques: State-of-the-Art and Perspectives

Inflammatory bowel disease (IBD), which includes ulcerative colitis and Crohn's disease, is characterized by chronic unregulated inflammation of the intestinal mucosa of the gastrointestinal tract. To date, this pathology has no cure. Colonoscopy and biopsies are the current gold standard diagnostic tools. However, being a chronic disease, IBD requires continuous follow-up to check for disease progress, treatment response, and remission. Unfortunately, these 2 diagnostic procedures are invasive and generally unable to show the cellular and molecular changes that take place in vivo. In this context, it is clear that there is a strong need for optimized noninvasive imaging techniques able to overcome the aforementioned limitations. This review aims to bring to light the scientific advancements that have been achieved so far in nuclear medicine in relation to tracking of immune cells involved in the preclinical models of IBD. In particular, this review will explore the advantages and limitations of the radiopharmaceuticals that aim to track whole cells like neutrophils, those that involve the radiolabeling of immune cell substrates or available human IBD medical therapies, and those that aim to track cell signaling molecules (e.g., cytokines and cell adhesion molecules). After a detailed critical summary of the state-of-the art, the challenges and perspectives of molecular imaging applied to IBD studies will be analyzed. Special attention will be paid to the translational potential of the described techniques and on the potential impact of these innovative approaches on the drug discovery pipelines and their contribution to the evolution of personalized medicine.