Specific-sized hyaluronan fragments promote expression of human ß-defensin 2 in intestinal epithelium.

Hyaluronan (HA) is a glycosaminoglycan polymer found in the extracellular matrix of virtually all mammalian tissues. Recent work has suggested a role for small, fragmented HA polymers in initiating innate defense responses in immune cells, endothelium, and epidermis through interaction with innate molecular pattern recognition receptors, such as TLR4. Despite these advances, little is known regarding the effect of fragmented HA at the intestinal epithelium, where numerous pattern recognition receptors act as sentinels of an innate defense response that maintains epithelial barrier integrity in the presence of abundant and diverse microbial challenges. Here we report that HA fragments promote expression of the innate antimicrobial peptide human ß-defensin 2 (HßD2) in intestinal epithelial cells. Treatment of HT-29 colonic epithelial cells with HA fragment preparations resulted in time- and dose-dependent up-regulated expression of HßD2 protein in a fragment size-specific manner, with 35-kDa HA fragment preparations emerging as the most potent inducers of intracellular HßD2. Furthermore, oral administration of specific-sized HA fragments promotes the expression of an HßD2 ortholog in the colonic epithelium of both wild-type and CD44-deficient mice but not in TLR4-deficient mice. Together, our observations suggest that a highly size-specific, TLR4-dependent, innate defense response to fragmented HA contributes to intestinal epithelium barrier defense through the induction of intracellular HßD2 protein.

Utility of fecal and serum anti-Saccharomyces cerevisiae antibodies in the diagnosis of Crohn's disease-like condition of the pouch.

BACKGROUND: Fecal antibodies against bacterial products may directly reflect the interaction between luminal bacteria and mucosal immunity, and assays for these antibodies may be clinically useful in the diagnosis and differential diagnosis of Crohn's disease-like (CDL) condition of the pouch. AIMS: This study aims to evaluate stool and serum anti-Saccharomyces cerevisiae antibodies (ASCA) in normal and diseased pouches, to assess the correlation between ASCA levels and endoscopic disease activity, and to ascertain the diagnostic utility of ASCA for CDL of the pouch. METHODS: One hundred eighty-nine patients with ileal pouches were prospectively enrolled and corresponding serum and pouch aspirate samples were collected. Fecal and serum ASCA levels were measured with enzyme-linked immunosorbent assay in a blinded fashion. Statistical analysis was then conducted using the signed rank test, Spearman correlation coefficients, and analysis of variance. RESULTS: Forty-three patients (22.8 %) had irritable pouch syndrome or normal pouches, 74 (39.2 %) had pouchitis/cuffitis, 52 (27.5 %) had CDL, 9 (4.8 %) had familial adenomatous polyposis, and 11 (5.8 %) had surgical complications of the pouch. Receiver operating characteristic curves to distinguish CDL from other categories of pouch dysfunction had an area under the curve (AUC) of 0.608 for fecal ASCA and an AUC of 0.517 for serum ASCA. Neither fecal nor serum ASCA correlated with endoscopic disease activity scores. There was a significant difference in the mean values of fecal ASCA between inflammatory and fistulizing CDL (0.27 vs. 0.03 ELISA units/ml, P < 0.05). CONCLUSIONS: Fecal ASCA appears to be better than serum ASCA in differentiating CDL from other pouch disorders, although this distinction may be of limited clinical utility.

Hyaluronan (HA) deposition precedes and promotes leukocyte recruitment in intestinal inflammation.

Increased hyaluronan (HA) deposition is a common feature of inflamed tissues, including inflammatory bowel disease (IBD)-involved intestines. However, whether HA accumulation promotes or is the result of intestinal inflammation is unknown. Using the mouse dextran sulfate sodium (DSS)-induced experimental model of colitis, we investigated changes in HA deposition in the colon over time in conjunction with evolving pathological changes of tissue architecture. Profound changes in colon HA deposition occurred within 3-7 days of oral DSS administration and, more important, they preceded the inflammatory infiltrate. Interestingly, HA deposition within blood vessels of the colon is observed as early as 3 days during the course of colitis induction, well before any significant inflammatory infiltrate. HA deposition is also observed in blood vessels of inflamed human colon of IBD patients. We determined that human intestinal endothelial cells generate HA in response to proinflammatory stimuli by demonstrating a TNF-alpha-induced increase in hyaluronan synthase-3 mRNA expression and the accumulation of HA cable-like structures that are adhesive for leukocytes. Additionally, IBD mucosal endothelial cells produce higher levels of cell surface HA in response to TNF-alpha than non-IBD control cells. Therefore, HA deposition is an early event in inflamed gut tissue, preceding and likely promoting leukocyte infiltration.