Identification of Lgr5-independent spheroid-generating progenitors of the mouse fetal intestinal epithelium

Immortal spheroids were generated from fetal mouse intestine using the culture system developed to culture organoids from adult intestinal epithelium. Spheroids are made of a monostratified polarized epithelium displaying a poorly differentiated intestinal phenotype. The proportion of spheroids generated from intestinal explants progressively decreases from fetal to postnatal period, with a corresponding increase in production of organoids. Spheroid cells show indefinite self-renewing properties but exhibit a transcriptome strikingly different from that of adult intestinal stem cells reminiscent of incompletely caudalized progenitors. The receptor Lgr4, but not Lgr5, is essential for their growth. Trop2/Tacstd2 and Cnx43/Gja1, two markers highly enriched in spheroids, are expressed throughout the E14 intestinal epithelium. Comparison of in utero and neonatal lineage tracing using Cnx43-CreER and Lgr5-CreERT2 mice identified spheroid-generating cells as developmental progenitors involved in generation of the prenatal intestinal epithelium. Ex vivo, spheroid cells have the potential to differentiate into organoids, thus qualifying them as a new type of intestinal stem-like cells. Two-channel microarray experiments were performed from spheroid/organoid pairs isolated each from a given embryo. Following initial seeding of small intestine from a given embryo/mouse (at E16, E18 or P0), spheroids and organoids were selectively picked up for each animal and replated for 3 passages to reach sample homogeneity. Hybridization was performed on the 4 independent pairs with dye-swap.