Guardian crypt-base-goblet-cells protect the human colonic stem cell niche by triggering cholinergic calcium signal-dependent MUC2 secretion and luminal flushing

Mucus secreting goblet cells play a vital role in the maintenance of tissue homeostasis. Here we report the discovery of an enigmatic mechanism for the generation of calcium signals that couple cholinergic input to secretion of hydrated mucus in the human colonic stem cell niche. Mechanistic insights for this study were derived from native human colonic crypts and crypt-like organoids expressing MUC2-mNEON. Importantly, we demonstrate that the human colonic stem cell niche is also a cholinergic niche, and that activation of muscarinic receptors initiates calcium signals at the apical pole of intestinal stem cells and neighbouring crypt-base-goblet-cells. The calcium signal trigger zone is defined by a microdomain of juxtaposed calcium stores expressing TPC1 and InsP3R3 calcium channels. Co-activation of TPC1 and InsP3R3 is required for generation of cholinergic calcium signals and downstream secretion of hydrated mucus, which culminates in the flushing of the colonic stem cell niche.

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Immunostaining of Lgr5, an Intestinal Stem Cell Marker, in Normal and Premalignant Human Gastrointestinal Tissue

The Scientific World JOURNAL ◽

10.1100/tsw.2008.148 ◽

2008 ◽

Vol 8 ◽

pp. 1168-1176 ◽

Cited By ~ 76

Author(s):

Laren Becker ◽

Qin Huang ◽

Hiroshi Mashimo

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Stem Cell Niche ◽

Intestinal Stem Cells ◽

Stem Cell Marker ◽

Tumor Initiating Cells ◽

Colonic Adenomas ◽

Potential Marker ◽

Cell Niche ◽

Crypt Base

Lgr5 has recently been identified as a murine marker of intestinal stem cells. Its expression has not been well characterized in human gastrointestinal tissues, but has been reported in certain cancers. With the increasing appreciation for the role of cancer stem cells or tumor-initiating cells in certain tumors, we sought to explore the expression of Lgr5 in normal and premalignant human gastrointestinal tissues. Using standard immunostaining, we compared expression of Lgr5 in normal colon and small intestine vs. small intestinal and colonic adenomas and Barrett's esophagus. In the normal tissue, Lgr5 was expressed in the expected stem cell niche, at the base of crypts, as seen in mice. However, in premalignant lesions, Lgr5+cells were not restricted to the crypt base. Additionally, their overall numbers were increased. In colonic adenomas, Lgr5+cells were commonly found clustered at the luminal surface and rarely at the crypt base. Finally, we compared immunostaining of Lgr5 with that of CD133, a previously characterized marker for tumor-initiating cells in colon cancer, and found that they identified distinct subpopulations of cells that were in close proximity, but did not costain. Our findings suggest that (1) Lgr5 is a potential marker of intestinal stem cells in humans and (2) loss of restriction to the stem cell niche is an early event in the premalignant transformation of stem cells and may play a role in carcinogenesis.

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