Abstract
Recombinant adeno-associated viral (rAAV) vectors are potentially powerful tools for gene therapy of CNS diseases, but their penetration into brain parenchyma is severely limited by the blood-brain barrier (BBB) and current delivery relies on invasive stereotactic injection. Here we evaluate the local, targeted delivery of rAAV vectors into the brains of mice by noninvasive, reversible, microbubble-facilitated focused ultrasound (FUS), resulting in BBB opening that can be monitored and controlled by magnetic resonance imaging (MRI). Using this method, we found that IV-administered AAV2-GFP (green fluorescence protein) with a low viral vector titer (1×109 vg/g) can successfully penetrate the BBB-opened brain regions to express GFP. We show that MRI monitoring of BBB-opening could serve as an indicator of the scale and distribution of AAV transduction. Transduction peaked at 3 weeks and neurons and astrocytes were affected. This novel, noninvasive delivery approach could significantly broaden the application of AAV-viral-vector-based genes for treatment of CNS diseases.
Highlights
Gene therapy is a potentially powerful means of treatment of various diseases with genomic causes
We verified the use of magnetic resonance imaging (MRI) to monitor focused ultrasound (FUS)-induced blood-brain barrier (BBB) opening
These local BBB-opening effects were confirmed as EB staining in experimental but not contralateral brain hemispheres (Fig. S1) and by increased EB dye extravasation at higher acoustic power (Fig. S2) (EB concentration increase of 97.7%, 508.2% and 726.5% were measured in 0.44, 0.53, and 0.7-MPa exposure, respectively)
Summary
Gene therapy is a potentially powerful means of treatment of various diseases with genomic causes. AAV serotype 2 (AAV2) vectors have been most intensively studied for the treatment of various diseases, and in clinical trials for Canavan’s [2], Batten’s [3], Parkinson’s [4], and Alzheimer’s diseases [5] Such central nervous system (CNS) disorders are important targets for gene therapy, but the delivery of therapeutic proteins and or genes to the brain presents a major challenge. Convection-enhanced delivery (CED) that infuses macromolecules or AAVs actively has been proposed to increase the distance of penetration after viral vector direct injection [8]. These procedures are invasive and subject to additional risks associated with surgery since Burr holes are required for insertion of the infusion tube [9,10]. With this viral vector dose (reaching 1012 vg), organs such as liver and heart would be significantly infected and it remains viral toxicity concerns
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