A30 MICROBIOTA AND NOD2 REGULATE SMALL INTESTINAL RESTITUTION THROUGH FETAL-LIKE INTESTINAL STEM CELLS

TL;DR

This study shows that gut microbiota and Nod2 signaling help repair the small intestine by activating fetal-like stem cells after injury.

Contribution

The paper reveals a novel mechanism where microbiota and Nod2 regulate intestinal repair through fetal-like stem cells.

Findings

Microbiota increase fetal-like stem cell markers and proliferation after intestinal injury.

Nod2 signaling in fetal-like stem cells enhances interferon gene activity during repair.

Nod2 deficiency reduces cell proliferation in injured intestines.

Abstract

Inflammatory bowel disease is characterized by chronic inflammation of the gastrointestinal tract, resulting in recurrent injury to the intestinal epithelium. Restitution of the small intestinal epithelium is a coordinated response that involves the dedifferentiation of epithelial cell lineages, proliferation of Lgr5+ intestinal stem cells, and fetal-like stem cell reversion. While gut microbiota are critical mediators of intestinal inflammation, their impact on epithelial restitution remains unclear.

We aim to identify the how microbes regulate small intestinal epithelial restitution following damage. Our hypothesis is that gut microbiota accelerate restitution through pattern recognition receptor-driven signals following fetal-like stem cell reversion.

Irradiation (IR, 12Gγ) was used to induce a synchronized small intestinal epithelial restitution response in mice. Intestinal restitution kinetics were assessed transcriptionally (scRNA-Seq, qPCR) and histologically. Small intestinal organoids were used to assess epithelial restitution kinetics in vitro.

ScRNA-Seq of small intestinal epithelial cells following IR from germ-free mice (GF), and specific pathogen-free mice (SPF) mice revealed that microbiota induced greater expression of fetal-like stem cell reversion markers, Ly6a and Clu, and greater expression of the proliferation marker, Pcna. These results were supported histologically as irradiated SPF mice observed an increase in fetal-like stem cells marked by Ly6a and Clu and an increase BrdU+ proliferating cells. ScRNA-seq and in situ hybridization highlighted that fetal-like intestinal stem cells upregulate expression of Nod2, a bacterial pattern recognition receptor. Using intestinal organoids to assess the function of Nod2, we observed that muramyl dipeptide driven Nod2-signlaing potentiates an interferon gene signature following IFNγ and TNFα co-stimulation. Further supporting the role for Nod2 in intestinal restitution, intestinal epithelium specific Nod2KO mice decreased BrdU+ proliferating cells post-IR compared to littermate controls.

Microbiota promote small intestinal restitution following IR through Nod2-signaling in fetal-like intestinal stem cells.

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