Feasibility of Using Focused Ultrasound-induced Blood-Brain Barrier Disruption to Enhance AAV2-GFP Expression in the Brain

Abstract

The use of recombinant adeno-associated viral (rAAV) vectors to facilitate gene therapy has a powerful potential in the CNS disease treatment, however, due to the blood-brain barrier (BBB) hampers the penetration of the viral vectors into the brain parenchyma, current approach only applied invasive local stereotactic injection of the therapeutic viral vectors. Microbubble-facilitated Focused ultrasound (FUS) has been shown to be able to locally and reversibly open the BBB and brings opportunity to deliver therapeutic-agents to the target brain for CNS disease treatment, and with used of magnetic resonance imaging (MRI), the BBB opening regions can be monitored and controlled. The purpose of this study is to evaluate the usefulness of delivering rAAV vectors into the brain facilitated by MRI-monitored FUS-BBB opening for achieving noninvasive and targeted gene delivery into the brain. Our results demonstrated that the IV administered AAV2-shRNA-GFP (109 vg/ml) can successfully penetrate the BBB-opened brain regions and produce equivalent GFP expression level to direct viral vector injection (also in 109 vg/ml), and its transduction peak occurred at 21 days. MRI-monitored BBB-opening, when transferred to the relative MR signal enhancement, can provide good prediction of the post-operational gene expression, suggesting the possibility of using MRImonitored BBB-opening can serve as an indicator of AAV-transducted scale and distribution. The use of AAV2-shRNA-GFP vectors was also found to majorly transduct glial cells in the CNS. The proposed approach may have potential for improving the usefulness and application spectrum on AAV-viral-vector-based gene delivery for CNS disease treatment. Abstract Materials and methods 1Department of Electrical Engineering, Chang Gung University, Kweishan, Taoyuan 333, Taiwan 2Animal Molecular Imaging Center, Chang Gung Memorial Hospital, Kweishan, Taoyuan 333, Taiwan 3Department of Medical Biotechnology and Laboratory Science, Chang Gung University, Kweishan, Taoyuan 333, Taiwan