Artificial microRNAs targeting tau enable post-symptomatic functional recovery in aged tauopathy mice.

Tauopathies are a group of neurodegenerative disorders, including Alzheimer's disease, frontotemporal dementia, and progressive supranuclear palsy, characterized by the pathological accumulation of tau protein. While tau reduction has emerged as a promising disease-modifying strategy, most preclinical studies have focused on preventive approaches, and the therapeutic potential after clinical onset remains largely unexplored. This limitation is critical, as patients are typically diagnosed after symptoms emerge. Furthermore, global tau suppression may disrupt physiological tau functions and lead to adverse effects, underscoring the need for targeted interventions. In this sense, RNA interference (RNAi)-mediated therapies using viral vectors offer high specificity, regional and cell-specific expression, and sustained target knockdown. We have engineered artificial microRNAs (Tau-miRNAs) to selectively reduce tau in vulnerable brain regions, minimizing off-target effects. Here, we tested the efficacy of these Tau-miRNAs in a tauopathy mouse model at advanced disease stages, delivering them into the prefrontal cortex after cognitive and electrophysiological deficit onset. This post-symptomatic intervention led to long-term improvements in memory, restoration of neuronal firing properties, and reduced pathological tau at synapses. Our findings highlight the potential of spatially targeted RNA-based tau-lowering strategies for late-stage intervention in tauopathies, addressing a critical unmet need in the treatment of these devastating disorders.