Paneth cells constitute the niche for Lgr5 stem cells in intestinal crypts

Abstract

Homeostasis of self-renewing small intestinal crypts results from neutral competition between Lgr5 stem cells, small cycling cells located at crypt bottoms1, 2. Lgr5 stem cells are interspersed between terminally differentiated Paneth cells, that are known to produce bactericidal products such as lysozyme and cryptdins/defensins3. Single Lgr5-expressing stem cells can be cultured to form long-lived, self-organizing crypt-villus organoids in the absence of non-epithelial niche cells4. Here, we note a close physical association of Lgr5 stem cells with Paneth cells in vivo and in vitro. CD24+ Paneth cells express EGF, TGFα, Wnt3 and the Notch-ligand Dll4, all essential signals for stem cell maintenance in culture. Co-culturing of sorted stem cells with Paneth cells dramatically improves organoid formation. This Paneth cell requirement can be substituted by a pulse of exogenous Wnt. Genetic removal of Paneth cells in vivo results in the concomitant loss of Lgr5 stem cells. In colon crypts, CD24+ cells residing between Lgr5 stem cells may represent the Paneth cell equivalents. We conclude that Lgr5 stem cells compete for essential niche signals provided by a specialized daughter cell, the Paneth cell.

Starvation Compromises Paneth Cells

“…6 indispensable in crypt survival, providing essential niche signals to stem cells. 25 Second, they are crucial in smallintestinal immunity by sensing and responding to enteric bacteria, protecting stem cells and limiting penetration of the intestinal wall by both commensal and pathogenic bacteria. 3 To this end, Paneth cells produce and secrete cytoplasmic granules containing a battery of antimicrobial proteins.…”

The non-muscle-myosin-II heavy chain Myh9 mediates colitis-induced epithelium injury by restricting Lgr5+ stem cells

“…Under physiological conditions, Lgr5 þ stem cells actively proliferate and differentiate into all types of cells in the intestinal and colonic epithelium. Several signalling pathways, including Wnt, bone morphogenetic protein (BMP) and Notch, have been demonstrated to regulate the fate of Lgr5 þ stem cells 5 . However, the molecular mechanism of how self-renewal and differentiation are balanced in Lgr5 þ stem cells remains unclear.…”

Modeling colorectal cancer as a 3-dimensional disease in a dish: the case for drug screening using organoids, zebrafish, and fruit flies

“…By in vivo lineage tracing, using the promoters of Lgr5 and Bmi1 to drive the expression of stable reporters, the Lgr5 and Bmi1 cell populations were shown to give rise to all the differentiated cell types in the intestine: the absorptive enterocytes and the three secretory lineages: goblet cells which secrete mucous, enteroendocrine cells which secrete hormones; and paneth cells which secrete innate immunity proteins such as defensins, as well as ligands for the Wnt, Notch, and EGFR pathways [26,27] (Fig. 1).…”

“…Because the niche exists within a milieu of many cell types and signals, both local and systemic, it is virtually impossible to fully recapitulate it in vitro. For example the ingredients list for growing organoid cultures lacks instructive ligands that are present in the in vivo niche, but are hard to supplement exogenously, such as tumor necrosis growth factor-alpha and the Notch ligand Delta-like4, DLL4 [27] (Fig. 2).…”