Depletion of Intestinal Stem Cell Niche Factors Contributes to the Alteration of Epithelial Differentiation in SAMP1/YitFcsJ Mice With Crohn Disease-Like Ileitis

Background: SAMP1/YitFcsJ (SAMP1) mice spontaneously develop terminal ileitis resembling human Crohn disease. SAMP1 mice have exhibited alteration of epithelial cell lineage distribution and an overall proliferation of the crypt cell population; however, it has not been evaluated whether epithelial differentiation is impaired because of dysfunction of intestinal stem cells (ISCs) or their niche factors. Methods: Using the intestine of SAMP1 mice aged 10 to 14 weeks, morphometric alterations in the crypt-villus architecture, ISCs, crypt cells, and differentiated cells; organoid formation capacity of intestinal crypts; and niche signaling pathways were analyzed and compared with those of age-matched control AKR/J (AKR) mice. Results: The ileum of SAMP1 mice showed increased depth of intestinal crypts and decreased surface area of the villi compared with those in the ileum of AKR mice. The number of ISCs in the ileal crypts did not differ between SAMP1 and AKR mice; however, the number of Paneth cells decreased and the number of transient amplifying cells increased. The organoid formation rate of the ileal crypts of SAMP1 mice decreased significantly compared with that of AKR mice. The performance of RNA sequencing for intestinal crypts found that the expression of ISC niche factors, such as Wnt3, Dll1, and Dll4, was decreased significantly in the ileal crypts of SAMP1 mice compared with those of AKR mice. Among the ISC niche signals, the Notch signaling-related genes tended to be downregulated. In particular, immunocytochemistry revealed that the expression of Paneth cell-expressing Notch ligand Dll4 was significantly decreased in the intestinal tissue and organoids of SAMP1 mice compared with those of AKR mice. Conclusions: Depletion of niche factors for ISCs contributes to the alteration of epithelial differentiation in SAMP1 mice.