BACE1 and Alzheimer disease: We then defined the therapeutic function of clinical‐grade hUC‐MSCs on SAMP8 mice at histological and protein levels, including regulation of representative AD‐related key proteins p‐Tau (Thr181), BACE1, pGSK3β (Tyr216), APP, PS1, pGSK3β (Ser9), and pAKT (Ser473) (Figures 2 and 8K; Figure S2, Supporting Information); Aβ plaques, NFTs and neuroinflammation in the hippocampus (Figures S8 and S9, Supporting Information); and the regeneration of endogenous neural stem cells (Figure 2).