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Aging-induced decline in mucus thickness in mice is associated with changes in microbiota composition and immunity and is sex dependent

ABSTRACT: A mucus layer covers and protects the intestinal epithelial cells from direct contact with microbes. This mucus layer not only prevents inflammation but also plays an essential role in microbiota colonization, indicating the complex interplay between mucus composition-microbiota and intestinal health. However, it is unknown whether the mucus layer is influenced by age or sex and whether this contributes to reported differences in intestinal diseases in males and females or with ageing. Therefore, in this study we investigated the effect of age on mucus thickness, intestinal microbiota composition and immune composition in relation to sex. The ageing induced shrinkage of the colonic mucus layer was associated with bacterial penetration and direct contact of bacteria with the epithelium in both sexes. Additionally, several genes involved in the biosynthesis of mucus were downregulated in old mice, especially in males, and this was accompanied by a decrease in abundances of various Lactobacillus species and unclassified Clostridiales type IV and XIV and increase in abundance of the potential pathobiont Bacteroides vulgatus. The changes in mucus and microbiota in old mice were associated with enhanced activation of the immune system as illustrated by a higher percentage of effector T cells in old mice. Our data contribute to a better understanding of the interplay between mucus-microbiota-and immune responses and ultimately may lead to more tailored design of strategies to modulate mucus production in targeted groups.

ORGANISM(S): Mus musculus

PROVIDER: GSE94515 | GEO | 2017/08/28

SECONDARY ACCESSION(S): PRJNA371227

REPOSITORIES: GEO

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Project description:Epithelial cells of the mammalian intestine are covered with a mucus layer that prevents direct contact with intestinal microbes but also constitutes a substrate for mucus-degrading bacteria. To study the effect of mucus degradation on the host response, germ-free mice were colonized with Akkermansia muciniphila. This anaerobic bacterium belonging to the Verrucomicrobia is specialized in the degradation of mucin, the glycoprotein present in mucus, and found in high numbers in the intestinal tract of human and other mammalian species. Efficient colonization of A. muciniphila was observed with highest numbers in the cecum, where most mucin is produced. In contrast, following colonization by Lactobacillus plantarum, a facultative anaerobe belonging to the Firmicutes that ferments carbohydrates, similar cell-numbers were found at all intestinal sites. Whereas A. muciniphila was located closely associated with the intestinal cells, L. plantarum was exclusively found in the lumen. The global transcriptional host response was determined in intestinal biopsies and revealed a consistent, site-specific, and unique modulation of about 750 genes in mice colonized by A. muciniphila and over 1500 genes after colonization by L. plantarum. Pathway reconstructions showed that colonization by A. muciniphila altered mucosal gene expression profiles toward increased expression of genes involved in immune responses and cell fate determination, while colonization by L. plantarum led to up-regulation of lipid metabolism. These indicate that the colonizers induce host responses that are specific per intestinal location. In conclusion, we propose that A. muciniphila modulates pathways involved in establishing homeostasis for basal metabolism and immune tolerance toward commensal microbiota. Keywords: Analysis of target gene regulation by using microarrays Adult germ-free female NMRI-KI mice (45 – 65 days) were used for bacterial mono-association. Two bacterial strains were used in this study, A. muciniphila MucT (ATTC BAA-835) and L. plantarum WCFS1 (NCIMB 8826). A. muciniphila was grown anaerobically in a basal mucin based medium and L. plantarum was grown anaerobically at 37°C in Man-Rogosa-Sharpe broth (MRS; Le Pont de Claix, France). After 7 days of colonization, mice were killed by cervical dislocation and terminal ileum, cecum and ascending colon specimens were sampled.

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Aging-induced decline in mucus thickness in mice is associated with changes in microbiota composition and immunity and is sex dependent

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