The development of new therapies to slow down or halt Parkinson’s disease (PD) progression is a healthcare priority. A key pathological feature of PD is the presence of alpha-synuclein aggregates and transmission of this pathology between neurons plays a central role in disease progression.

 

Objective: We aimed to evaluate if alpha-synuclein downregulation by shRNA-minicicles (shRNA-MC) delivered by RVG-extracellular vesicles (RVG-EV) administrated after the appearance of the alpha-synuclein pathology halt the neurodegenerative process.

 

Methods: RVG-EVs were isolated from dendritic cells transfected to express the RVG-peptide and loaded with shRNA-MCs by electroporation. We used a progressive synucleinopathy model based on the intrastriatal injection of alpha-synuclein preformed fibrils (syn PFFs). RVG-EVs containing shRNA-MC were administred intravenously 35 and 80 days after syn PFF injection, a group of mice received only one injection 35 days after syn PFF injection.

 

Results: The treatment with 2 doses of shRNA-MC RVG-EV decreased significantly alpha-synuclein mRNA and protein levels in the brain. This decrease was reflected in a significant reduction in the number of phospho-alpha-synuclein aggregates, the normalization of the striatal TH staining and the lack of dopaminergic cell death. However, the treatment with only one dose was not sufficient to reduce mRNA or protein levels of alpha-synuclein 105 days after administration.

 

Conclusions: We demonstrated that the treatment with anti-alpha-synuclein shRNA-MC RVG-EV after the development of pathology is effective to downregulate alpha-synuclein in brain. Moreover, we confirmed that a multidose treatment is necessary to maintain downregulation for long-term treatments.