rAAV‑mediated Hsp70 gene delivery alleviates FUS‑associated ALS‑like pathology

Impaired cellular proteostasis and pathological protein aggregation are key mechanisms underlying neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Current treatments are largely symptomatic, highlighting the need for alternative approaches. Heat shock proteins, particularly Hsp70, have emerged as promising neuroprotective agents in this context. Here, we evaluated the neuroprotective effect of AAV-mediated Hsp70 expression in a transgenic S-FUS(1-359) mouse model of FUS-associated proteinopathy with an ALS-like phenotype. Mice received retro-orbital injections of recombinant AAV vectors encoding HSPA1A-3xFLAG at two doses. Therapeutic efficacy was assessed based on survival, disease onset, symptomatic stage duration, body weight, functional tests, and Hsp70 expression. AAV-mediated Hsp70 expression prolonged survival, with the strongest effect observed in the high-dose group. Median survival increased to 170.5 days, representing a ~ 33% extension compared to non-treated controls (128 days). Mean lifespan was also increased to 172.2 ± 40.4 days versus 140.2 ± 30.1 days in controls (23% increase). The duration of the symptomatic stage was extended by 30% in the high-dose group (18.71 ± 5.36 days vs. 14.39 ± 5.36 days in controls). Additionally, high-dose rAAV-Hsp70 treatment delayed the progression of hindlimb impairment, specifically extending the periods of limited mobility and paralysis. Overall, these findings demonstrate that AAV-mediated Hsp70 expression exerts a disease‑modifying effect by slowing the symptomatic progression of FUS‑associated pathology in the transgenic mouse model of ALS.