Basic Science and Pathogenesis.

Background: Alzheimer's disease (AD) is a complex neurodegenerative disorder characterized by hallmark pathologies that affect many brain regions, including the cellular microenvironment with the hippocampus, ultimately leading to profound deficits in cognition. Surprising recent work has shown that factors in the systemic environment regulate the hippocampal cellular niche; age-associated blood-borne factors exacerbate brain aging phenotypes, whereas youth-associated blood-borne factors, including tissue inhibitor of metalloproteinases 2 (TIMP2), reverse or ameliorate features of brain aging. As aging serves as the major risk factor for AD, and recent work shows that systemic factors can regulate AD pathology, we sought to characterize mechanisms by which the systemic environment regulates CNS phenotypes relevant to AD pathology through changes in neuroinflammation.