ORIGINAL ARTICLE Progression and Variability of TNBS Colitis-associated Inflammation in Rats Assessed by Contrast-enhanced and T2-weighted MRI Andreas Pohlmann, PhD,* Lorna C. Tilling, MSc,* Alison Robinson, DipAVN, † Olga Woolmer, BSc, † Scott McCleary, BSc, ‡ Laurens Kruidenier, PhD, ‡ Linda C. Warnock, MSc, § Huw D. Lewis, PhD, ‡ Anthony R. Hobson, PhD, ‡ and Michael F. James, PhD* Background: A common feature of preclinical models of colitis is that the time-course, magnitude, and persistence of inflammation vary considerably within the experimental animal group. Accord- ingly, noninvasive, serial quantification of colonic inflammation could advantageously guide dosing regimens and assess drug effi- cacy, thus enhancing the value of colitis models in research. This investigation using magnetic resonance imaging (MRI) was there- fore undertaken to objectively determine inflammatory progression, variability, and response to therapy associated with trinitrobenzene sulfonic acid (TNBS)-induced colitis in Wistar rats. Methods: Rats underwent TNBS treatment on Day 0 and received sulfasalazine or vehicle (methylcellulose) orally, daily, from Day -1 (prophylactically) or Day 2 (therapeutically). T2-weighted and semidynamic T1-weighted contrast-enhanced MRI (CE-MRI) was repeated over 7–10 days to measure colon wall thickness and per- fusion-related aspects of inflammation. Rectal bleeding, stool con- sistency, and disease activity were scored throughout and colon pathology determined terminally. Results: Principal component analysis of the CE-MRI time-series highlighted colon wall and mesenteric inflammation, which in- creased by 6 – 8 naı ¨ve values. Peristaltic artifacts were distin- guished from perfusion changes using the normalized temporal standard deviation. MRI correlated strongly with terminal colon weight (mean correlation r = 0.8), well with body weight change (r =-0.7), but little with conventional clinical scores. Sulfasalazine reduced inflammation administered prophylactically and therapeuti- cally. Conclusions: Inflammation and therapeutic efficacy can be sensi- tively quantified noninvasively using MRI in TNBS-treated rats. This methodology provides unique and objective in vivo measures of inflammation that can guide dosing strategies, enhancing colitis research effectiveness and the assessment of potential IBD thera- peutics. (Inflamm Bowel Dis 2009;15:534 –545) Key words: colitis, inflammation, rats, imaging, MRI U lcerative colitis and Crohn’s disease (together referred to as inflammatory bowel disease [IBD]) are serious, life- long, remitting-relapsing inflammatory conditions that affect the colon. IBD has a widespread geographic incidence. Esti- mates suggest up to 109,000 new cases of IBD in Europe and 46,000 in the USA and Canada develop per year: as many as 1.4 million persons in the USA and 2.2 million persons in Europe suffer from these diseases. 1 The causes of IBD appear to be manifold, including both environmental and genetic determinants, and a much greater understanding now exists of the inflammatory regulatory mechanisms that may mediate this disease. 2 This new knowledge is stimulating research into the discovery of novel therapeutics for IBD. Animal models of colitis 3,4 have been used to study drug activity; they include transgenic and mutant strains of mice with specific deficits, and inducible models in which dextran-sulfate sodium (DSS) or immunological haptens such as trinitrobenzene sulfonic acid (TNBS) are administered. In the TNBS model, a mucosal barrier breaker (ethanol) is administered rectally with the hapten—an acute injury phase results that develops into a longer-lasting immunological reaction. 3,5 Chemically induced models of colitis have re- ceived much attention because they are strain-sensitive (sug- gesting the importance of uncharacterized phenotypic modi- fiers), simple to induce, and evoke widespread immunoinflammatory sequelae in the colon that can be con- siderably prolonged. 6 Morris et al 5 reported mucosal and Received for publication September 29, 2008; Accepted September 30, 2008. From the *Preclinical MRI Centre, Immuno-Inflammation Centre of Ex- cellence in Drug Discovery, GlaxoSmithKline R&D, Harlow, UK, † Labora- tory Animal Sciences, GlaxoSmithKline R&D, Harlow, UK, ‡Immuno- Inflammation Centre of Excellence in Drug Discovery, GlaxoSmithKline R&D, Stevenage, UK, §Discovery Statistics Europe, GlaxoSmithKline R&D, Stevenage, UK. Reprints: Anthony R. Hobson, Immuno-Inflammation Centre of Ex- cellence in Drug Discovery, GlaxoSmithKline Medicines Research Centre, Gunnels Wood Road, Stevenage, SG1 2NY, UK (e-mail: anthony.r.hobson@gsk.com). Copyright © 2008 Crohn’s & Colitis Foundation of America, Inc. DOI 10.1002/ibd.20800 Published online 4 December 2008 in Wiley InterScience (www. interscience.wiley.com). 534 Inflamm Bowel Dis ● Volume 15, Number 4, April 2009