INTESTINAL EPITHELIAL CELL-SPECIFIC CFTR KNOCKOUT MICE EXHIBIT FECAL MICROBIAL DYSBIOSIS

Chronic intestinal inflammation is a poorly understood manifestation of Cystic Fibrosis (CF) disease. Fecal microbial dysbiosis has the potential of inducing intestinal inflammation and has been reported in people with CF as well as CF mouse models. CF mice consuming an osmotic polyethylene glycol (PEG) laxative in drinking water to prevent intestinal obstruction have low levels of intestinal inflammation and low intestinal bacterial loads. In contrast, CF mice consuming a nutritionally complete liquid diet to prevent intestinal impaction exhibit intestinal inflammation and high intestinal bacterial loads (R. C. De Lisle, et al., Am J Physiol 293, G577-G584, 2007) To investigate the development of dysbiosis in a CFTR-deficient intestine, we transitioned adult intestinal epithelial cell-specific knockout and wild-type (WT) mice from life-long consumption of PEG laxative to a nutritionally-complete liquid diet for a two week period before collection of fecal samples.

Fecal samples collected from B6.Cg-Tg(Vil1-cre)-Cftr^f10/f10 intestinal-specific Cftr knockout mice (iCftr KO) and their WT sex-matched littermates were DNA extracted and prepared for 16S rRNA sequencing and evaluation of the microbiome. Microbial community composition, richness and diversity indices, and relative abundance of bacterial species of interest were evaluated.

16S rRNA sequencing and metagenomic analysis revealed significant differences in microbial composition with intestinal-specific loss of CFTR as compared to WT, as well as a significant decrease in Shannon diversity and Chao-1 richness indices. A significant deficit of taxa was seen in the intestinal-specific CF mice, as compared to WT, which corresponded with a significant increase in bacterial species that potentially serve as provocateurs of intestinal inflammation including Helicobacter typhlonius, Clostridium perfringens, Ruminococcus gnavus, and Tyzerella spp.

As compared to WT, the transition from PEG laxative to a nutritionally-complete liquid diet resulted in overt differences in the fecal microbiota composition in iCftr KO mice which included enrichment of potential bacterial pathobionts capable of stimulating intestinal inflammation. These studies suggest that the CFTR-deficient intestinal epithelium provides an environment selective for potential bacterial pathobionts. The paradigm of the study may prove useful for investigating the development of dysbiosis and corresponding changes in intestinal mucosal immunity.