1,25-Dihydroxy Vitamin D Enhances the Differentiation of Intestinal Stem Cells Ex Vivo and In Vivo

Abstract Inflammatory bowel disease (IBD) is a chronic inflammatory disorder in the intestines. Current therapies aim at suppressing inflammation to prevent further damage. However, healing already damaged intestinal epithelia is still an unmet medical need. In this regard, epithelial healing is achieved via intestinal stem cells (ISCs) that are located in the intestinal crypts. Considering the literature reports that the active vitamin D (1,25[OH]2D) is essential for the maintenance of Lgr5+ ISCs, the active proliferating ISCs, we recently proposed to deliver locally high 1,25(OH)2D concentrations to the proximity of intestinal crypts to promote intestinal stem cell functions. This local delivery was devised to avoid potential side effects associated with systemically high 1,25(OH)2D concentrations. Using 5-Bromo-20-deoxyuridine (BrdU) to label the actively proliferating ISCs, our previous data indicated that the locally delivered 1,25(OH)2D enhanced the migration and differentiation of Lgr5+ ISCs. However, although sparse in the crypts, other proliferating cells may be labeled with BrdU. This current study used a unique mouse strain to precisely trace Lgr5+ ISCs and consolidated our previous finding that the locally delivered 1,25(OH)2D augmented ISC differentiation. Besides, we generated pure Lgr5+ ISC lines that could be induced to differentiate on demand. Our data showed that, in vitro, 1,25(OH)2D enhanced the differentiation of Lgr5+ ISCs. Moreover, by knocking down the vitamin D receptor (VDR), we demonstrated that the 1,25(OH)2D functions in ISCs are mediated through VDR. Accordingly, our findings suggest that locally high 1,25(OH)2D concentrations are a promising strategy for intestinal epithelial healing. This study was partially supported by the National Institute of Health (NIH, USA) grant (1R21AI142170); the US Army Medical Research and Materiel Command grant (W81XWH-15-0240); and the GI Foundation of Loma Linda University Innovation grant (RIG-GI 681207-2967).