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Notum produced by Paneth cells attenuates regeneration of aged intestinal epithelium.

ABSTRACT: A decline in stem cell function impairs tissue regeneration during ageing, but the role of the stem-cell-supporting niche in ageing is not well understood. The small intestine is maintained by actively cycling intestinal stem cells that are regulated by the Paneth cell niche^1,2. Here we show that the regenerative potential of human and mouse intestinal epithelium diminishes with age owing to defects in both stem cells and their niche. The functional decline was caused by a decrease in stemness-maintaining Wnt signalling due to production of Notum, an extracellular Wnt inhibitor, in aged Paneth cells. Mechanistically, high activity of mammalian target of rapamycin complex 1 (mTORC1) in aged Paneth cells inhibits activity of peroxisome proliferator activated receptor α (PPAR-α)³, and lowered PPAR-α activity increased Notum expression. Genetic targeting of Notum or Wnt supplementation restored function of aged intestinal organoids. Moreover, pharmacological inhibition of Notum in mice enhanced the regenerative capacity of aged stem cells and promoted recovery from chemotherapy-induced damage. Our results reveal a role of the stem cell niche in ageing and demonstrate that targeting of Notum can promote regeneration of aged tissues.

SUBMITTER: Pentinmikko N

PROVIDER: S-EPMC8151802 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The recognition of autophagy related 16-like 1 (ATG16L1) as a genetic risk factor has exposed the critical role of autophagy in Crohn's disease. Homozygosity for the highly prevalent ATG16L1 risk allele, or murine hypomorphic (HM) activity, causes Paneth cell dysfunction. As Atg16l1(HM) mice do not develop spontaneous intestinal inflammation, the mechanism(s) by which ATG16L1 contributes to disease remains obscure. Deletion of the unfolded protein response (UPR) transcription factor X-box binding protein-1 (Xbp1) in intestinal epithelial cells, the human orthologue of which harbours rare inflammatory bowel disease risk variants, results in endoplasmic reticulum (ER) stress, Paneth cell impairment and spontaneous enteritis. Unresolved ER stress is a common feature of inflammatory bowel disease epithelium, and several genetic risk factors of Crohn's disease affect Paneth cells. Here we show that impairment in either UPR (Xbp1(?IEC)) or autophagy function (Atg16l1(?IEC) or Atg7(?IEC)) in intestinal epithelial cells results in each other's compensatory engagement, and severe spontaneous Crohn's-disease-like transmural ileitis if both mechanisms are compromised. Xbp1(?IEC) mice show autophagosome formation in hypomorphic Paneth cells, which is linked to ER stress via protein kinase RNA-like endoplasmic reticulum kinase (PERK), elongation initiation factor 2? (eIF2?) and activating transcription factor 4 (ATF4). Ileitis is dependent on commensal microbiota and derives from increased intestinal epithelial cell death, inositol requiring enzyme 1? (IRE1?)-regulated NF-?B activation and tumour-necrosis factor signalling, which are synergistically increased when autophagy is deficient. ATG16L1 restrains IRE1? activity, and augmentation of autophagy in intestinal epithelial cells ameliorates ER stress-induced intestinal inflammation and eases NF-?B overactivation and intestinal epithelial cell death. ER stress, autophagy induction and spontaneous ileitis emerge from Paneth-cell-specific deletion of Xbp1. Genetically and environmentally controlled UPR function within Paneth cells may therefore set the threshold for the development of intestinal inflammation upon hypomorphic ATG16L1 function and implicate ileal Crohn's disease as a specific disorder of Paneth cells.

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Notum produced by Paneth cells attenuates regeneration of aged intestinal epithelium.

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