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P003 HDAC7 Controls Differentiation and Regeneration in the Intestinal Epithelium

Gerbeth, L.(1);Glauben, R.(1);Siegmund, B.(1);

(1)Charité - Universitätsmedizin Berlin, Medical Department of Gastroenterology- Infectiology and Rheumatology, Berlin, Germany

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.

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