TNF Receptor 1 regulates colonic mesenchymal cell diversity and the epithelial stem cell niche
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BACKGROUND & AIMS
Anti-tumor necrosis factor (anti-TNF) is a mainstay of inflammatory bowel disease (IBD) therapy but fails in many patients. Although TNF has pro-inflammatory effects, depletion of TNF receptor 1 (TNFR1) paradoxically exacerbates chronic colitis. Because colitis induces remodeling of mesenchymal cell populations, which provide a niche for epithelial stem cells involved in mucosal healing, we hypothesized that TNFR1 promotes colonic mesenchymal cell diversity and stem cell niche function.
METHODS
Mesenchymal TNFR1 function was studied using TNFR1 -/- , platelet derived growth factor receptor alpha (PDGFRα)-Cre;TNFR1 fl/fl mice, and mixed-genotype mesenchymal-epithelial co-cultures. Mesenchymal cell diversity and gene function were assessed using single-cell RNA-Seq of primary colonic myofibroblasts (CMFs) and via anti-integrin A6 (ITGA6) antibody treatment and exogenous R-spondin 3 (RSPO3) supplementation.
RESULTS
TNFR1 -/- mesenchyme exhibits reduced cell diversity, with specific depletion of specialized TNF- and interferon-signaling pericryptal cell-type. Deletion of TNFR1 in the pericryptal mesenchyme diminished the (PDGFRα)+ CMF population and reduced RSPO3 expression, but increased ITGA6 expression relative to controls (TNFR1 +/- ). Moreover, inhibition of ITGA6 reversed the proliferative and migratory phenotype of TNFR1 -/- CMFs and restored expression of PDGFRα and RSPO3. Co-cultures of colonoids with TNFR1 -/- CMFs resulted in downregulation of stem cell marker expression; this was rescued by supplementation with RSPO3. Supporting the role for mesenchymal TNFR1 in regulating colonic epithelial stem cells, mice deficient for TNFR1 in PDGFRα+ cells showed a 40% loss of Lgr5+ stem cells, consistent with the global TNFR1-deficient mouse.
CONCLUSION
TNFR1-mediated signaling regulates specification and function of colonic mesenchyme, performing an integral role in the maintenance of the crypt stem cell population.
