Failure of Alzheimer's Mice Brain Resident Neural Precursor Cells in Supporting Microglia-Mediated Amyloid ß Clearance.

ABSTRACT

The failure of brain microglia to clear excess amyloid ß (Aß) is considered a leading cause of the progression of Alzheimer's disease pathology. Resident brain neural precursor cells (NPCs) possess immune-modulatory and neuro-protective properties, which are thought to maintain brain homeostasis. We have recently showed that resident mouse brain NPCs exhibit an acquired decline in their trophic properties in the Alzheimer's disease brain environment. Therefore, we hypothesized that functional NPCs may support microglial phagocytic activity, and that NPCs derived from the adult AD mouse brain may fail to support the clearance of Aß by microglia. We first identified in the AD brain, in vivo and ex vivo, a subpopulation of microglia that express high Aß phagocytic activity. Time-lapse microscopy showed that co-culturing newborn NPCs with microglia induced a significant increase in the fraction of microglia with high Aß phagocytic activity. Freshly isolated NPCs from adult wild type, but not AD, mouse brain, induced an increase in the fraction of microglia with high Aß phagocytic activity. Finally, we showed that NPCs also possess the ability to promote Aß degradation within the microglia with high Aß phagocytic activity. Thus, resident brain NPCs support microglial function to clear Aß, but NPCs derived from the AD environment fail to do so. We suggest that the failure of AD brain NPCs to support Aß clearance from the brain by microglia may accelerate disease pathology.