Dysbiosis in the Mouse Esophagus Caused by CaSR Deletion

Background We have previously reported a mouse model, where we knocked out the calcium sensing receptor (CaSR) in the esophageal stratified squamous epithelium ( Eso CaSR ‐/‐ ) using Cre recombination. The esophageal tissues showed morphological changes including elongation of the rete pegs, abnormal keratinization and stratification, and a remarkable bacterial build‐up on the luminal epithelial surface. In addition, the barrier properties of the epithelium were altered as indicated by a decrease in cell‐cell junction proteins and increased permeability. Objective We aimed to quantify and characterize the mucosal‐associated bacterial microbiome caused by deletion of CaSR in the esophagus. Methods To explore the bacterial buildup in Eso CaSR ‐/‐ esophageal tissue, we analyzed the mucosal‐associated bacterial microbiome and compared it to the one in control Eso CaSR +/+ mice. Total bacterial load was estimated by quantitative polymerase chain reaction (qPCR) of 16S ribosomal DNA (rDNA) using SYBER green. We sequenced 16S rRNA targeting the hypervariable V3‐V4 region and performed gene profiling and metagenomic analysis. Results Quantification of 16S DNA by qPCR indicated ~1.5‐fold increase in bacterial load in Eso CaSR ‐/‐ as compared to control. Sequencing data indicated significant changes in the microbiome composition of Eso CaSR ‐/‐ . Phylum P‐Cyanobacteria was increased in Eso CaSR ‐/‐ , family F_Burkholderiacea and order o_Betaproteobacteria were decreased. The microbe species s_Rodentibacter, s_Lactobacillus_hilgardii were enriched in CaSR KO mice while s_Curvibacter_unclassified, s__Streptococcus_equinus, s_Lactobacillus_crispatus and s_Millionella_massiliensis were decreased. Linear discriminant analysis (LDA) detected 3 bacterial species ; g‐Rodentibacter, s_Rodentibacter_unclassified, and s_Lactobacillus_hilgardi showed statistically significant and biologically consistent differences between control and Eso CaSR ‐/‐ tissues. Metagenomic analysis indicated a significant decrease in metabolic pathways and bacterial enzymes. Conclusions This is the first report on dysbiosis caused by CaSR deletion in the esophagus. Our data demonstrate a direct in‐vivo interaction between esophageal epithelia and bacteria and could shed light on cellular factors modulating the microbiome.