Foxl1-expressing mesenchymal cells constitute the intestinal stem cell niche.

BACKGROUND & AIMS: Intestinal epithelial stem cells that express Lgr5 and/or Bmi1 continuously replicate and generate differentiated cells throughout life. Previously, Paneth cells were suggested to constitute an epithelium-intrinsic niche that regulates the behavior of these stem cells. However, ablating Paneth cells has no effect on maintenance of functional stem cells. Here, we demonstrate definitively that a small subset of mesenchymal, subepithelial cells expressing the winged-helix transcription factor Foxl1 are a critical component of the intestinal stem cell niche.

METHODS

We genetically ablated Foxl1 mesenchymal cells in adult mice using two separate models by expressing either the human or simian diphtheria toxin receptor (DTR) under Foxl1 promoter control.

CONCLUSIONS

Killing Foxl1 cells by diphtheria toxin administration led to an abrupt cessation of proliferation of both epithelial stem- and transit-amplifying progenitor-cell populations that was associated with a loss of active Wnt signaling to the intestinal epithelium. Therefore, Foxl1-expressing mesenchymal cells constitute the fundamental niche for intestinal stem cells.