ORIGINAL ARTICLE Effects of T cell-induced Colonic Inflammation on Epithelial Barrier Function Peter Suenaert, MD, PhD,* Philippe Maerten, MD, PhD,* Gert Van Assche, MD, PhD,* Willy Van Driessche, PhD, † Karel Geboes, MD, PhD, ‡ Veerle Bulteel, MSc,* Jeannine Simaels, BSc, † Patrick Augustijns, PhD, § Jan L. Ceuppens, MD, PhD, k Paul Rutgeerts, MD, PhD,* and Cle´mentine Perrier, PhD* Background: Epithelial barrier disturbance is thought to con- tribute to the pathogenesis of inflammatory bowel diseases; how- ever, it remains unclear whether it is a primary defect participating to the onset of inflammation or only a consequence of sustained inflammation. Methods: A time course study of epithelial barrier functions and immune mediators was performed in the CD4 þ CD45RB hi T cell transfer model of colitis using Ussing chambers. Results: In nonreconstituted severe combined immunodeficiency (SCID) mice, no epithelial dysfunction was observed. However, after transfer of CD4 þ CD45RB hi T cells or total CD4 þ T cells, colon of SCID mice displayed a decreased epithelial resistance, even before overt microscopic inflammation had occurred. Sus- tained colitis of CD4 þ CD45RB hi T cell reconstituted mice was also associated with enhanced subepithelial resistance, enhanced paracellular permeability, and decreased net ion transport. All these reflect a disturbance of barrier function and may contribute to diarrhea. Epithelial resistance was positively correlated with interleukin 10 (IL-10) and transforming growth factor b (TGF-b) levels and net ion transport inversely correlated with tumor necro- sis factor alpha (TNF-a) levels, pointing to the protective effect of IL-10 and TGF-b and to a damaging effect of TNF-a. Indo- methacin, a nonselective COX inhibitor, decreased epithelial re- sistance independent of T cells and inflammation, but its effect was more pronounced in inflamed colon. Conclusions: Induction of colitis by transfer of CD4 þ CD45RB hi T cells in SCID mice leads to changes in the colonic epithelium before colitis develops. Decreased epithelium resistance might contribute to the development of colitis; however, it is not suffi- cient to lead to chronic inflammation. (Inflamm Bowel Dis 2010;16:1322–1331) Key Words: Crohn’s disease, experimental colitis, epithelial barrier function, cytokines, indomethacin C rohn’s disease (CD) is a segmental inflammatory dis- ease of the intestine characterized by a massive infil- tration of CD4 þ T cells and macrophages and by epithelial damage. The relationship between inflammation and epithe- lial dysfunction is not well understood. Diarrhea, which is frequently associated with intestinal inflammatory diseases including enteric infections, ulcerative colitis, CD, and celiac disease, reflects an imbalance between intestinal absorption and secretion of water and electrolytes. Inflammation-induced changes in epithelial cell function may induce a decrease in active colonic sodium absorption and/or increased chloride secretion. Moreover, inflammation can be associated with altered tight junction structure, resulting in an impaired epithelial barrier function with increased loss of electrolytes and water into the lumen. 1–3 The gut epithelial barrier is an essential component of the innate immune function preventing or limiting the entry of potentially noxious substances, such as microbes and antigens, into the body. A variety of defense mecha- nisms are located in close proximity to the epithelium, and it is well established that immune cells and inflammatory mediators affect epithelial cell function. 4 In vivo murine models of colitis offer a potential approach to characterize the intestinal epithelial function in inflamed mucosa in comparison to healthy circumstances. Received for publication November 18, 2009; Accepted November 30, 2009. From the *Division of Gastroenterology, University Hospital, Leuven, Belgium; † Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium, ‡ Department of Morphology and Molecular Pathology, University Hospital, Leuven, Belgium, § Department of Pharmacotechnology and Biopharmacy, Katholieke Universiteit Leuven, Belgium, k Department of Experimental Immunology, University Hospital, Leuven, Belgium. Supported by grants from the Foundation for Scientific Research Flanders (FWO-Vlaanderen, grant G.0507.06), by a Researcher Fellowship Funding of the Flemish Fund for Scientific Research (FWO-Vlaanderen, grant 1.5.054.02) (to P.S.), by a grant from the Research Council of the Catholic University of Leuven, and by a Schering-Plough IBD fellowship (to P.M., C.P.). The first 2 authors contributed equally to this work. Reprints: Cle ´mentine Perrier, PhD, Department of Gastroenterology, University hospital Gasthuisberg, Katholieke Universiteit Leuven, Herestraat 49, 3000 Leuven, Belgium (e-mail: Clementine.Perrier@med. kuleuven.be) Copyright V C 2010 Crohn’s & Colitis Foundation of America, Inc. DOI 10.1002/ibd.21211 Published online 12 February 2010 in Wiley InterScience (www. interscience.wiley.com). Inflamm Bowel Dis  Volume 16, Number 8, August 2010 1322