Neprilysin expression increases microglial Aβ phagocytosis. The numbers of IBA-1 immunoreactive microglia were quantified adjacent to control and sNEP-NSC grafts. (A-B) As expected, NSC transplantation increases the recruitment of IBA-1+ microglia towards the injection site. In addition, sNEP expression appears to further increase graft-associated microglial numbers (P <0.05). (C-D) Interestingly, neprilysin expression also significantly increases the co-localization between IBA-1+ (red) and Aβ (green), suggesting that sNEP expression may indirectly enhance microglial Aβ phagocytosis (P <0.05). N = 6/group, error bars represent standard error of the mean (SEM). Scale Bars = 300 μm in A top panels, 25 μm in A bottom panels, and 12 μm in C. Aβ, beta- amyloid; NSCs, neural stem cells; sNEP, secreted neprilysin.