Polyethylenimine Nanoparticle-Mediated siRNA Delivery to Reduce α-Synuclein Expression in a Model of Parkinson’s Disease

Abstract

RNA interference (RNAi)-based strategies that mediate the specific knockdown of target genes by administration of small interfering RNAs (siRNAs) could be applied for treatment of presently incurable neurodegenerative diseases such as Parkinson’s disease. However, inefficient delivery of siRNA into neurons hampers in vivo application of RNAi. We have previously established the 4–12 kDa branched polyethylenimine (PEI) F25-LMW with superior transfection efficacy for delivery of siRNA in vivo. Here, we present that siRNA complexed with this PEI extensively distributes across the CNS down to the lumbar spinal cord after a single intracerebroventricular infusion. siRNA against α-synuclein (SNCA), a pre-synaptic protein that aggregates in Parkinson’s disease, was complexed with PEI F25-LMW and injected into the lateral ventricle of mice overexpressing human wild-type SNCA (Thy1-aSyn mice). Five days after the single injection of 0.75 μg PEI/siRNA, SNCA mRNA expression in the striatum was reduced by 65%, accompanied by reduction of SNCA protein by ∼50%. Mice did not show signs of toxicity or adverse effects. Moreover, ependymocytes and brain parenchyma were completely preserved and free of immune cell invasion, astrogliosis, or microglial activation. Our results support the efficacy and safety of PEI nanoparticle-mediated delivery of siRNA to the brain for therapeutic intervention.

The Promise and Challenges of Developing miRNA-Based Therapeutics for Parkinson’s Disease

“…Although a large number of positive charges and non-biodegradability of polymeric carriers can reduce their viability and use, several studies have shown efficacy in PD. Thus, an in vivo study in mice using PEI/siRNA complexes decreased the expression of α-synuclein mRNA and protein in the striatum by about 50% [201] without causing toxic signs. Likewise, several in vitro studies have demonstrated the efficiency of PEG/PEI complexes as vectors for delivering of anti-α-Syn siRNAs to PC12 cells [202].…”

Progress in the molecular pathogenesis and nucleic acid therapeutics for Parkinson's disease in the precision medicine era

“…201 In other preclinical studies, polyethylenimine-siRNA and RVGexosome-siRNA targeting α-synuclein transcripts also demonstrated a robust reduction of both overexpressed human SNCA mRNA and α-synuclein protein in the striatum of a PD mouse model and delayed the development of α-synuclein pathology. 202,203 However, a delicate SNCA level must be maintained as it is obvious that too little α-synuclein may also be harmful to the brain because of its essential biological functions at the synapse. Marked downregulation of SNCA expression by siRNA was associated with an increased risk of developing nigrostriatal degeneration.…”

Nucleic Acid–Based Therapeutics for Parkinson's Disease

“…For example, a therapeutic approach using ribozyme expressed by adeno-associated virus (AAV) has been attempted to degrade SNCA mRNA and allowed the survival of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra of rats challenged with the dopaminergic toxin 1-methyl-4-phenylpyridinium (MPP + ) [4]. In addition, other methods that use short hairpin RNA (shRNA) and short interfering RNA (siRNA) to suppress SNCA expression have been tested [5][6][7][8][9][10][11][12][13]. For example, partial silencing of αsynuclein expression in striatal neurons can be achieved using a lentiviral vector expressing SNCA-targeting shRNA [5].…”

“…In PARK4 patients, α-synuclein protein is produced in excess, leading to its accumulation/ aggregation and neurodegeneration midbrain and striatum [11]. More recently using α-synuclein transgenic mice, intracerebroventricular infusion of polyethylenimine (PEI)/siRNA complex against α-synuclein resulted in 65% suppression of SNCA mRNA expression accompanied by a 50% reduction of α-synuclein protein in the striatum [12].…”