A62 BMP SIGNALING IN FOXL1+ CELLS IS A KEY TO THE INTESTINAL STEM CELL NICHE HOMEOSTASIS. (1st March 2018)

• Record Type: Journal Article
• Authors: Servant, R; Jones, C; Boudreau, F; Perreault, N
• Is Part Of: Journal of the Canadian Association of Gastroenterology. Volume 1(2018)Supplement 2
• Page Start: 98
• Page End: 99
• Publication Date: 2018-03-01
• Subjects: Gastroenterology -- Periodicals; 616.33005
• DOI: 10.1093/jcag/gwy009.062
• Languages: English
• ISSNs: 2515-2084

Abstract

Abstract: Background: New components of the intestinal stem cell niche are constantly being discovered. Recently, the subepithelial Foxl1 + cells were found to play a key role in maintaining and regulating intestinal crypt homeostasis. Foxl1 + cells produce crucial niche components such as WNT2b, WNT5a and RSPO3 as well as the Bone Morphogenic Proteins (BMP) inhibitors Gremlin 1 and 2. Previous work in our laboratory showed that epithelial BMP signaling is involved in terminal differentiation and maturation of cells from the secretory lineage. Our recent work showed that the loss of mesenchymal BMP signaling leads to the development of a pathological microenvironment inducing colonic and gastric polyposis in older mice, drawing attention to the impact of a pathogenic microenvironment in polyposis. Aims: By genetic means, we propose to address how BMP signaling in Foxl1 + cells modulates the intestinal stem cell niche. Methods: Using the Cre/loxP system, we generated mice with a deletion of BmpR1a in all gastrointestinal Foxl1 + subepithelial mesenchymal cells. Histological analysis and terminal differentiation assessment were performed with cellular staining and immunofluorescence (H&E, Alcian Blue and Lysozyme). Niche components were analysed by RT-qPCR from crypt epithelium or total ileal RNA extracts. Results: H&E staining on 9 months-old BmpR1a Δmes and control mice ileum demonstrated perturbed architecture in the BmpR1a Δmes such as fused and enlarged villi compared to control mice. Alcian Blue staining showed an increase of goblet cells in the mutant mice. Electron microscopy showed that Paneth cells from mutant mice have larger vesicles than controls. The RT-qPCR analysis showed a decrease in WNT signaling targets in the crypts epithelium cells. Indeed, LGR5 is decreased by 50% and mTERT by 34% in the mutant mice, whereas the stem cell marker BMI1 is not modulated. Maturity of Paneth cells is impaired in the mutant mice as shown by a 41% decrease in SOX9 expression. This lack in Paneth cell maturity is also reflected by a 60% decrease in WNT3 expression in BmpR1a Δmes mice, an important stem cell niche factor. Secretory cell determination transcription factor ATOH1 is decreased by 35% in the mutant mice. Analysis from total ileal extract revealed a decrease of WNT2b, a key niche factor from the mesenchymal cells. Conclusions: Altering Bmp signaling in Foxl1 + subepithelial mesenchymal cells modulates crucial niche factors and thus influences the stem cells homeostasis and their subsequent determination. Further analysis, with the use of organoids, will evaluate the survival of intestinal stem cells from the BmpR1a Δmes mice in absence of its surrounding mesenchyme. Funding Agencies: CIHR