PSEN1 and Alzheimer disease: Some studies have shown that BMSCs trigger immune/inflammation responses through the activation of microglia in APP/presenilin 1 (PS1) double-transgenic (Tg) mice.17, 19 Other studies suggest that stem cells can induce neurotrophic factors.10, 14, 15 Indeed, BDNF was essential for the behavioral effects of NSC in triple Tg mice (3xTg-AD).34