Poster Session II - A295 DEPLETION OF COLONIC HNF4A ACCENTUATES <i>CITROBACTER RODENTIUM</i> INFECTION SEVERITY IN FEMALE MICE

Abstract Background The transcription factor hepatocyte nuclear factor 4 alpha (HNF4A), an epithelial specific transcriptional regulator, is significantly decreased in inflammatory bowel diseases. The Citrobacter rodentium infection model in mice recapitulates human intestinal diseases associated with enteropathogenic E. coli. It is currently unclear whether the absence of HNF4A in the gut mucosa impacts the severity of C. rodentium infection-related intestinal diseases. Aims Herein, we aimed to determine whether the loss of HNF4A in intestinal epithelial cells (IEC) renders the intestinal epithelium more susceptible to C. rodentium infection, thereby altering the gut microbiota composition and the function of goblet cells (GCs) and mucus layers, as preconditions leading to the onset of severe colitis. Methods Control and Hnf4aΔIEC-ind mice of both sexes were challenged with C. rodentium and then monitored daily for body weight and fecal C. rodentium counts until bacterial clearance was achieved. Gut microbiota composition of cecum and colon fecal samples will be defined by 16S rDNA sequencing. The integrity of the GC and mucus layers upon C. rodentium infection will be evaluated using immunohistochemistry, immunofluorescence, immunoblotting, and gene expression analyses. Results Hnf4a ΔIEC-ind female mice weighed significantly less than the controls from day 9 post-infection until the moment they cleared the bacteria. The course of the infection was erratic in the control group, whereas the female mutants exhibited a rapid and consistent infection, characterized by much higher levels of bacteria in their feces. Surprisingly, Hnf4aΔIEC-ind male mice did not differ significantly from the controls under these conditions. Preliminary observations suggested that the colonic base of crypts in GC was rapidly depleted in infected Hnf4aΔIEC-ind mice. Since mucin-degrading bacteria such as Akkermansia muciniphila were reported to be increased in Hnf4aΔIEC mice in the past, we expect to find signs of dysbiosis in Hnf4aΔIEC-ind mice associated with GC and mucus layer defects. Conclusions These results support the notion that HNF4A function in IEC is essential for preserving epithelial defenses through the control of gut microbiota composition and the prevention of GC and mucus layer dysfunction, particularly in female mice. As future directions, we will measure the impact of the microbiota on GC and other IEC types in the context of colon organoid-derived monolayers in Transwells. Funding Agencies CIHR