Cytokine biomarkers from tissue homogenates were examined to characterize the inflammatory status of the mice (Figure 1E). These data generally confirmed the clinical parameters although there were some interesting temporal changes reflecting the character of the developing pathology. The time course of IL1�� protein mirrored the observed changes www.selleckchem.com/products/MDV3100.html in the clinical parameters peaking at day 8 and subsequently decreasing to the end of the experiment. Similar to IL1��, IL6 and KC/IL8 also peaked on days 5 and 8 respectively, and returned to baseline levels. IL12p40, IL17, TGF�� and IFN�� demonstrated parallel temporal profiles over the course of the experiment. All four cytokines did not differ from control levels during the initial inflammatory response but temporally peaked at day 22; for TGF��, IL12p40 and IFN�� levels were significantly higher than cytokine levels on day 8.

Overall, the results of the clinical, histological and inflammatory biomarkers examined support the conclusion that DSS-induced epithelial damage results in development of a maturing immune response from an initial acute phase into a chronic inflammation of the colon characterized by distinct proinflammatory cytokine profiles. Figure 1 Temporal physical, histological and biomarker analysis of DSS damage. Temporal regulation of bacterial/host interaction following DSS damage A previous report demonstrated that DSS administration is associated with penetration of the colonic tissue by the commensal flora of the intestine [22]. Therefore, we tested the hypothesis that bacterial penetration of the tissue regulates the progression to chronic inflammation (Figure 2).

A cocktail of fluorescent-labeled bacterial FISH probes recognizing >95% of type strain bacteria was used to gauge bacterial infiltration into the tissue following DSS damage (Figure 2A, Figure S1). In the absence of DSS damage, the commensal bacteria remained in the lumen of the gut separated from the host by the mucous layer (Figure 2A). Following DSS, a clear progression of commensal infection into the host tissue could be observed. Consistent with the previous report, at day 8 following DSS damage, commensal bacteria were reliably observed in association with the epithelial layer. Tissue-associated bacteria were detected in deeper tissue layers over the time course of the experiment. By day 21, commensal bacteria could be detected in the lamina Batimastat propria of the mucosa and by day 28 in the submucosal and muscle layers. From day 35 to day 42, complete histological restitution of the epithelial layer was observed. However, there remained clear evidence of persistent commensal bacteria infiltration of deeper tissue layers especially the muscle and viscera.