APP and Alzheimer disease: To deeply investigate the morphological changes in the gut of AD mice, through XPCT, we analyzed the ileum villi and crypts of various mouse models: healthy wild-type (WT) mice aged matched (18 months) to APP/PS1dE9 and APP23 AD mice, senescence-accelerated mouse resistant-1 (SAMR1) mice, and littermate controls of senescence-accelerated mouse-8 (SAMP8) frail mice of 11 months of age (38, 39).