Amyloid-β-regulated gene circuits for programmable Alzheimer's disease therapy.

Alzheimer's disease (AD) is a neurodegenerative disease characterized in part by the accumulation of the protein amyloid-β (Aβ). Monoclonal antibodies (mAbs) that target Aβ for clearance from the brain have received FDA approval; however, these therapies are accompanied by serious side effects, and their cognitive benefit for patients remains of tremendous debate. Here, we present a potential engineered cell therapy for AD in which we enlist cells of the central nervous system as programmable agents for sculpting the neurodegenerative niche toward one that mitigates glial reactivity and neuronal loss. We constructed a suite of Aβ-sensitive synthetic Notch (synNotch) receptors from clinically tested anti-Aβ mAbs and show that cells expressing these receptors can recognize synthetic Aβ(42) and Aβ(40) with differential sensitivity. We express these receptors in astrocytes, cells native to the brain that are known to become dysfunctional in AD. These synNotch astrocytes, which upregulate selected transgenes upon exposure to synthetic and human brain-derived amyloid, were engineered to express potential therapeutic transgenes in response to Aβ, including brain-derived neurotrophic factor and antagonists of the cytokines tumor necrosis factor and interleukin-1. SynNotch astrocytes that express such antagonists in response to Aβ partially attenuate a cytokine-induced reactive astrocyte phenotype and promote barrier properties in brain microvascular endothelial cells. Additionally, engineered Aβ-synNotch cells potently upregulate transgene expression in response to Aβ deposited in the 5xFAD mouse brain, demonstrating the capacity to recognize Aβ in situ. Overall, our work supports Aβ-synNotch receptors as promising tools to generate a cell-based therapy for AD with targeted functionalities to positively influence the AD niche.