GSE185350
Lymphatic endothelial cells, together with Rspo3+Grem1+ fibroblasts, support intestinal stem cells through the production of R-spondin3 in homeostasis and injury [200909Yil]
Intestinal stem cells (ISCs) depend on niche factors for proper function. Here, we focus on RSPO3, an essential ISC niche factor, that engages the Lgr5 receptor on ISCs to potentiate WNT signaling, an interaction that is critical for maintaining intestinal stemness. Leveraging novel Rspo3-GFP and Grem1-tdTomato-CreERT2 genetically engineered mice together with single-cell mRNA profiling, we find that RSPO3 is expressed by lymphatic endothelial cells (LECs) and Rspo3+Grem1+ (RG) fibroblasts in the intestinal stroma where RG fibroblasts surround lymphatics and are in close proximity to Lgr5+ ISCs near the crypt base. Functionally, RG fibroblasts through the production of RSPO3 and GREM1 and LECs through the production of RSPO3 foster intestinal organoid propagation in vitro. Rspo3 loss in either or both of these niche cells in vivo compromises ISC numbers, villi length, and repair after irradiation-induced injury. Mechanistically, irradiation-induced damage expands LEC and RG fibroblast numbers and enhances the latters' generation of RSPO3 through IL-1 receptor activation. We propose that LECs represent a novel component of the ISC niche, which together with RG fibroblasts, provide essential RSPO3 to sustain ISCs in homeostasis and regeneration. Overall design: Three replicates each of small intestinal or colonic Epcam negative, CD45 negative stromal cells positive or negative for CD31 or Rspo3.