The CSF-1 receptor fashions the intestinal stem cell niche

Abstract

Gastrointestinal (GI) homeostasis requires the action of multiple pathways. There is some controversy regarding whether small intestine (SI) Paneth cells (PCs) play a central role in orchestrating crypt architecture and their relationship with Lgr5+ve stem cells. Nevertheless, we previously showed that germline CSF-1 receptor (Csf1r) knock out (KO) or Csf1 mutation is associated with an absence of mature PC, reduced crypt proliferation and lowered stem cell gene, Lgr5 expression. Here we show the additional loss of CD24, Bmi1 and Olfm4 expression in the KO crypts and a high resolution 3D localization of CSF-1R mainly to PC. The induction of GI-specific Csf1r deletion in young adult mice also led to PC loss over a period of weeks, in accord with the anticipated long life span of PC, changed distribution of proliferating cells and this was with a commensurate loss of Lgr5 and other stem cell marker gene expression. By culturing SI organoids, we further show that the Csf1r−/− defect in PC production is intrinsic to epithelial cells as well as definitively affecting stem cell activity. These results show that CSF-1R directly supports PC maturation and that in turn PCs fashion the intestinal stem cell niche.

Regulation of Embryonic and Postnatal Development by the CSF-1 Receptor

“…Csf1 promoter-driven transgenic expression of the cell surface isoform of CSF-1 in Csf1 op/op mice rescues the macro phage and PC deficiencies, as well as stem cell activity suggesting that CSF-1 regulates intestinal development, in a juxtacrine or paracrine manner (Huynh et al, 2009). In addition, intestine-specific deletion of Csf1r reproduced the Csf1r −/− phenotype, formally proving that CSF-1R cell autonomously supports PC development (Akcora et al, 2013). These studies also showed that the CSF-1R is essential for de novo generation of PC, but not for their survival and demonstrated the critical role of CSF-1R regulation of PC in the maintenance of intestinal stem cells.…”

“…They have additional roles as regulators of detoxification, digestion, and in the regulation of stem cells as components of the stem cell niche (Clevers & Bevins, 2013; Porter, Bevins, Ghosh, & Ganz, 2002; Wehkamp & Stange, 2006). In both Csf1 op/op and Csf1r −/− mice, there is abnormal organization of the small intestine, with marked reductions of epithelial cells, including PC and intestinal stem cells, and of interstitial macrophages of the villi (Akcora et al, 2013; Cecchini et al, 1994; Huynh et al, 2009). PCs express the CSF-1R and reside in close proximity to CSF-1-expressing epithelial cells within the crypt (Huynh et al, 2009).…”

“…Several different cell types, including epithelial cells, endothelial cells, osteoblasts, and neurons, were shown to synthesize CSF-1 (Huynh et al, 2009; Nandi et al, 2012; Ryan et al, 2001). Biochemical studies revealed the existence of three distinct biologically active CSF-1 isoforms, a secreted glycoprotein (sgCSF-1) (Price, Choi, Rosenberg, & Stanley, 1992; Stanley & Heard, 1977), a secreted proteoglycan (spCSF-1) (Price et al, 1992; Suzu et al, 1992), and a membrane-spanning cell surface glycoprotein (csCSF-1) (Rettenmier et al, 1987; reviewed in Pixley & Stanley, 2004), each of which have overlapping, yet distinct effects when exclusively expressed in Csf1 op/op mice (Akcora et al, 2013; Dai, Zong, Sylvestre, & Stanley, 2004; Huynh et al, 2009; Nandi, Akhter, Seifert, Dai, & Stanley, 2006). …”

Establishment of Gastrointestinal Epithelial Organoids

“…Several studies demonstrated intestinal stem cell niche functions for Paneth or colonic goblet cells (Durand et al, 2012;Farin et al, 2012;Rothenberg et al, 2012;Sato et al, 2011). Similarly, enteroids deficient for Csf1r(-/-), which have a defect in Paneth cell production, showed defective enteroid formation (Akcora et al, 2013).…”

Establishment of Human Epithelial Enteroids and Colonoids from Whole Tissue and Biopsy

“…These epithelial organoid culture systems have been used to test the ability of isolated single cells to function as stem cells in vitro, thus testing the "stemness" of isolated cells 5,6,[10][11][12][13][14][15] . Other investigators have used both enteroids and colonoids to study the function of individual epithelial cells [16][17][18][19][20][21] . Thus, enteroid and colonoid cultures can be used to evaluate both stem and non-stem cell functions and give new insight into fundamental cellular interactions within the intestines.…”