Lgr5 Controls Extracellular Matrix Production By Stem Cells In The Developing Intestine

The Lgr5 receptor is a marker of intestinal stem cells (ISCs) that regulates Wnt/b-catenin signaling. In this study, phenotype analysis of knockin/knockout Lgr5-eGFP-IRES-Cre and Lgr5-DTReGFP embryos revealed that Lgr5 deficiency during Wnt-mediated cytodifferentiation results in amplification of ISCs and early differentiation into Paneth cells, which can be counteracted by in utero treatment with the Wnt inhibitor LGK974. Conditional ablation of Lgr5 postnatally, but not in adults, altered stem cell fate towards the Paneth lineage. Together, these in vivo studies suggest that Lgr5 is part of a feedback loop to adjust the Wnt tone in ISCs. Moreover, transcriptome analyses revealed that fetal ISCs generate their own extracellular matrix components, a property lost in adult ISCs, which adopt a definitive epithelialized phenotype and an inflammatory response signature. Absence of Lgr5 in fetal ISCs resulted in reduced extracellular matrix production and accelerated ISC maturation, indicating that Lgr5 regulates the ISC niche. Finally, evidences are provided that Rspondin 2 negatively regulates the pool of ISCs in organoids via Lgr5, revealing a sophisticated regulatory process for Wnt signaling in ISC.