Development of a Novel AAV-Mediated microRNA Gene Therapy for Spatial Suppression of BACE1 to Improve Cognitive Function in Alzheimer’s Disease Model Mice

The beta-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1) is a promising and rational target for Alzheimer’s disease (AD), but current clinical trials have been disappointing. Consequently, utilizing the intrinsic regulatory mechanisms of BACE1 during AD pathogenesis might provide valuable insights into the treatment of this devastating disease. In this study, we proposed a combination of AAV delivery and microRNA therapeutics targeting AD at its root by sustained and spatial inhibition of BACE1 with a single therapeutic injection. We demonstrate that upregulation of BACE1 is correlated with downregulation of miR-143-3p in the hippocampus of individuals with AD, and miR-143-3p can directly target BACE1 to inhibit Aβ generation. In the brains of 5×FAD model mice, BACE1 levels are found to be elevated with age in the cornu ammonis 1 (CA1) subfield of the hippocampus. AAV-mediated miR-143-3p restoration in the hippocampal CA1 subfield of AD mice can improve cognitive performance, attenuate BACE1 expression, reduce Aβ levels, induce microglia polarization toward the anti-inflammatory phenotype, modulate neural-related genes including Gal3, and promote synaptic functions. Collectively, the AAV-mediated microRNA gene therapy approach developed for spatial suppression of BACE1 can effectively enhance cognitive performance in AD model mice, offering an attractive therapeutic option for AD treatment with long-lasting efficacy.