Evaluation of Immunological Response to TLR2 and α-SMA in Crohn's Disease and Ulcerative Colitis

Inflammatory bowel diseases (IBDs) represent multifactorial chronic inflammatory conditions of the gastrointestinal tract. The main IBDs are Crohn's disease (CD) and ulcerative colitis (UC). CD may cause perforation, stricture or transmural inflammation, which can occur discontinuously in the entire gastrointestinal tract (GIT). UC leads to mucosal inflammation as well as mucosal atrophy in the rectum and the colon. Innate immunity is considered the first line of defense against microbial invasion; among Toll-like receptors, TLR2 is the most important for defense against mycobacterial infection. TLR2 has been reported to have a lot of functions in infectious diseases and in other pathologies, such as chronic and acute inflammatory diseases. Alfa-Smooth Muscle Actin (alpha-SMA) is an important biomarker in IBDs. All myofibroblasts express alpha-SMA, which has been found to be upregulated in CD and UC. Paraformaldehyde-fixed intestinal tissues, from patients with CD and patients with UC, were analyzed by immunostaining for TLR2 and alpha-SMA. Our results showed that, in the samples obtained from UC patients with inflamed mucosa, TLR2-positive epithelial cells concentrated on the mucosal surface and scattered immune cells in the connective tissue; furthermore, numerous alpha-SMA-positive cells (subepithelial myofibroblasts) were detected in the lamina propria and around glands, while some myofibroblasts co-localizing with alpha-SMA and TLR2 could be inflammatory macrophages. In CD patients, TLR2-positive enterocytes and alpha-SMA-positive myofibroblasts in the lamina propria of the villus have been observed. In control samples, a low positivity to alpha-SMA and TLR2 was observed in subepithelial myofibroblasts and scattered immune cells of the lamina propria. These data showed the recall of alpha-SMA-positive myofibroblasts during the inflammatory state; in addition, TLR2 expression has been observed to change in the intestinal epithelium in IBDs, demonstrating that alterations in the innate system response may contribute to the pathogenesis of these diseases.