In vivo silencing of alpha-synuclein using naked siRNA

Abstract

Background: Overexpression of α-synuclein (SNCA) in families with multiplication mutations causes parkinsonism and subsequent dementia, characterized by diffuse Lewy Body disease postmortem. Genetic variability in SNCA contributes to risk of idiopathic Parkinson's disease (PD), possibly as a result of overexpression. SNCA downregulation is therefore a valid therapeutic target for PD.

Tissue-specific gene silencing monitored in circulating RNA

“…At the end of the 7-d infusion period, brains and CSF were collected for analysis. Consistent with previous studies demonstrating gene silencing in neuronal cells by intraparenchymal CNS siRNA infusion (Lewis et al 2008;Querbes et al 2009), a 33 ± 13% reduction in striatal Snca mRNA was measured in animals receiving the Snca siRNA compared with naïve animals. To analyze CSF RNA, pooled samples were subjected to high-speed centrifugation, and total RNA was isolated from the pellets.…”

Nerve Injection of Viral Vectors Efficiently Transfers Transgenes into Motor Neurons and Delivers RNAi Therapy Against ALS

“…While progress will be made in this front, an alternative strategy is to deliver RNAi therapy by directly infusing synthetic siRNA into the CNS. Several groups have tested this strategy using different neurodegenerative disease models, including models for Huntington disease, Parkinson disease, and ALS (15,31,54). These experiments have shown that the infused siRNA can knockdown the expression of the target disease genes such as mutant huntingtin, a-synuclein, and SOD1, and in some cases, display modest therapeutic efficacy.…”

shRNA targeting α-synuclein prevents neurodegeneration in a Parkinson’s disease model

“…There are four previous reports of RNAi-mediated knockdown of endogenous α-synuclein in the adult CNS in vivo (63)(64)(65)(66). Naked siRNA infused into the mouse hippocampus gave rise to a significant 60%-80% reduction in Snca mRNA and a qualitative decrease in α-synuclein protein levels, but no overt cell loss or microgliosis (65). Naked siRNA infused into the primate midbrain caused a 50% reduction in SNCA mRNA, associated with a 40% reduction in α-synuclein.…”

“…However, acute knockdown of Snca in the adult brain could potentially cause unwanted effects by circumventing developmental compensatory mechanisms that occur in germline null mutants. There are four previous reports of RNAi-mediated knockdown of endogenous α-synuclein in the adult CNS in vivo (63)(64)(65)(66). Naked siRNA infused into the mouse hippocampus gave rise to a significant 60%-80% reduction in Snca mRNA and a qualitative decrease in α-synuclein protein levels, but no overt cell loss or microgliosis (65).…”