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Background The precise causes and drivers of inflammatory bowel disease (IBD) are still incompletely understood. In recent years, intensive research has shown that not only chronic activation of the immune compartment, but also the integrity of the epithelial barrier plays a central role in disease progression. Inhibitors of histone deacetylases (HDACs) are known for their anti-inflammatory effects and increasing evidence suggests them as promising therapeutics for chronic inflammatory conditions such as IBD. However, the roles of single HDACs in the intestinal epithelium, especially class II HDACs, are still scarcely investigated. In genome wide association studies, HDAC7 has been identified as a risk locus for the development of IBD. Here, we investigated the role of HDAC7 in the intestinal epithelium to evaluate its potential as a therapeutic target. Methods Intestinal epithelial organoids were derived from the ileum and colon of tamoxifen-inducible HDAC7 knockout mice. Hdac7 deletion of organoids was achieved in vitro by tamoxifen treatment over five consecutive days of culture. Morphological changes were monitored via microscopy and gene expression was analysed using qPCR. To examine barrier function, colon organoids were seeded as monolayers into filter inserts and transepithelial electrical resistance (TEER) was measured. Monolayer structure was verified using immunofluorescence. Results Hdac7 silencing in organoids of the small intestine caused a significant morphological shift to a spheroidal shape typical for an undifferentiated phenotype. Gene expression analysis revealed a dramatic downregulation of differentiation markers for all epithelial subtypes and an upregulation of stem cell markers. In colon organoids, undifferentiated HDAC7 knockout spheroids showed a significantly increased expression of goblet cell markers but displayed reduced enterocyte marker expression when subjected to differentiation medium. TEER build-up was consistently slower in colon organoid-derived monolayers after Hdac7 deletion but was higher after differentiation compared to wild type monolayers. Conclusion In the ileal epithelium, HDAC7 seems to play an important role in the differentiation process of all specialized epithelial subtypes while it appears to suppress mainly secretory lineages and promote differentiation into absorptive cells in the colon epithelium. These results suggest HDAC7 as an important regulator of intestinal differentiation and regeneration making it an interesting therapeutic target to treat inflammation-induced injuries in the gut.

Background Inflammatory bowel disease (IBD) represents a dysregulation of the mucosal immune system. The pathogenesis of Crohn’s disease (CD) and ulcerative colitis (UC) is linked to the loss of intestinal tolerance and barrier function. The healthy mucosal immune system has previously been shown to be inert against food antigens. Since the small intestine is the main contact surface for antigens and therefore the immunological response, the present study served to analyse food-antigen-specific T cells in the peripheral blood of IBD patients. Methods Peripheral blood mononuclear cells of CD, with an affected small intestine, and UC (colitis) patients, either active or in remission, were stimulated with the following food antigens: gluten, soybean, peanut and ovalbumin. Healthy controls and celiac disease patients were included as controls. Antigen-activated CD4+ T cells in the peripheral blood were analysed by a magnetic enrichment of CD154+ effector T cells and a cytometric antigen-reactive T-cell analysis (‘ARTE’ technology) followed by characterisation of the effector response. Results The effector T-cell response of antigen-specific T cells were compared between CD with small intestinal inflammation and UC where inflammation was restricted to the colon. Among all tested food antigens, the highest frequency of antigen-specific T cells (CD4+CD154+) was found for gluten. Celiac disease patients were included as control, since gluten has been identified as the disease-causing antigen. The highest frequency of gluten antigen-specific T cells was revealed in active CD when compared with UC, celiac disease on a gluten-free diet (GFD) and healthy controls. Ovalbumin-specific T cells were almost undetectable, whereas the reaction to soybean and peanut was slightly higher. But again, the strongest reaction was observed in CD with small intestinal involvement compared with UC. Remarkably, in celiac disease on a GFD only antigen-specific cells for gluten were detected. These gluten-specific T cells were characterised by up-regulation of the pro-inflammatory cytokines IFN-γ, IL-17A and TNF-α. IFN-g was exclusively elevated in CD patients with active disease. Gluten-specific T-cells expressing IL-17A were increased in all IBD patients. Furthermore, T cells of CD patients, independent of disease activity, revealed a high expression of the pro-inflammatory cytokine TNF-α. Conclusion The ‘ARTE’-technique allows to analyse and quantify food antigen specific T cells in the peripheral blood of IBD patients indicating a potential therapeutic insight. These data provide evidence that small intestinal inflammation in CD is key for the development of a systemic pro-inflammatory effector T-cell response driven by food antigens.