Genetically Engineered Small Extracellular Vesicles to Deliver Alpha-Synuclein siRNA Across the Blood-Brain-Barrier to Treat Parkinson’s Disease
Creators: name: Sosa Miranda, Carmen Daniela
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 2022
Subjects: Small extracellular vesicles
Parkinson’s Disease
Blood-Brain Barrier
neurogenerative disorders
small interfering RNA
transport vesicles
Alpha-Synuclein
gene silencing
genetic engineering

description: Small extracellular vesicles (small EVs) are endogenous membrane-enclosed nanocarriers released from essentially all cells. They have been shown to carry proteins, lipids, nucleic acids to transmit biological signals throughout the body, including to the brain. Some evidence has suggested that small EVs can cross the blood-brain barrier (BBB), moving from the peripheral circulation to the central nervous system (CNS). The BBB is a dynamic barrier that regulates molecular trafficking between the peripheral circulation and the CNS. As a result, small EVs have attracted attention for their potential as a novel delivery platform for nucleic acid-based therapeutics across the BBB. Silencing RNAs (siRNAs) are a potent drug class but using “naked” siRNA is not feasible due to their short half-life, vulnerability to degradation and low penetration in cells. Despite the excitement for the development of small EV-based therapeutics, their clinical development is hampered by the lack of reliable methods for packing therapeutics into them. Reshke et al. has shown that cells can be genetically engineered to produce customizable small EVs packaged with siRNA against any protein by integrating the siRNA sequence into the pre- miR-451 structure. Mounting evidence has established that in a misfolded state, α-synuclein becomes insoluble and phosphorylated to form intracellular inclusions in neurons (known as Lewy bodies) which leads to Parkinson’s disease (PD) pathogenesis. Given that increased α-synuclein expression causes familial and idiopathic PD, decreasing its synthesis by using siRNA is an attractive therapeutic strategy. Here, we genetically engineered cells to produce small EVs packaged with siRNA against α-synuclein integrated in the pre-miR451 backbone, tested their ability to cross an in vitro BBB, and deliver its cargo to silence endogenous α-synuclein in neuron- like cells. The therapeutic potential of α-synuclein siRNA delivery by these small EVs was demonstrated by the strong mRNA (60-70%) and protein knockdown (43%) of α-synuclein in neuron-like cells. We also demonstrated that approximately at 4% and 2%, respectively of small EVs-derived from human brain endothelial cells (hCMEC/D3) and human embryonic kidney (HEK293T) were transported cross the in vitro BBB model. Interestingly, we observed that small EVs-derived from HEK293T deliver their cargo to induced brain endothelial cells (iBECs) (~74% α-synuclein mRNA reduction) but their rate of transport across BBB was lower and did not reduce α-synuclein mRNA expression in neuron-like cells, seeded on the far side of the BBB. Small EVs- derived from hCMEC/D3 reduced α-synuclein mRNA (40%) in neuron-like cells across the BBB model. This finding suggests that small EVs derived from different cell sources can undergo different intracellular trafficking routes, providing various opportunities to influence the efficiency of delivery and fate of intracellular cargo. Using small EVs-derived from hCMEC/D3, two different routes of administration, a single bolus intravenous (IV) or intra-carotid (ICD) injection, showed small EVs largely accumulated in the liver, spleen, small intestines and kidneys; and only a small amount of small EVs were detected in the brain. These results indicate that human brain endothelial cells may serve as a promising cell source for CNS treatments based on small EVs.