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Efficient, spatially selective delivery of adeno-associated virus (AAV) therapeutics to deep brain structures remains a major challenge to gene therapy for Alzheimer's disease (AD), owing to limited transport across the blood-brain barrier (BBB) and poor penetration to target neurons. Here, we establish an integrated, noninvasive imaging and therapy platform that combines microbubble-enhanced focused ultrasound (MB-FUS) with positron emission tomography/computed tomography (PET/CT) to transiently modulate the BBB, enhance region-specific AAV delivery following systemic dosing, and longitudinally track transduction in vivo. Optimized MB-FUS achieved targeted hippocampal delivery of systemically administered AAV9 in healthy mice, resulting in a 10-fold enhancement of neuronal transduction as compared to non-FUS controls. Importantly, longitudinal PET reporter gene imaging in the 5xFAD AD model demonstrated robust brain AAV transduction that remained stable for at least seven months. Finally, to assess therapeutic impact, we used brain-derived neurotrophic factor (BDNF) as a test cargo. MB-FUS-facilitated delivery elevated BDNF expression in targeted regions and produced short-term improvements in synaptic signaling in 5xFAD mice. Collectively, these results highlight MB-FUS as a next-generation delivery platform to overcome barriers to AAV therapeutic delivery in Alzheimer's disease and position longitudinal PET assessment as a critical, translatable tool for monitoring and optimizing gene therapy. Show less

This pilot study investigated the protective effect of transfecting brain-derived neurotrophic factor (BDNF) and B-cell lymphoma 2 (bcl-2) genes in retinal ganglion cells (RGCs) using in vivo electroporation in an adult rat optic nerve transection model. Sprague-Dawley rats were randomly divided into five groups: BDNF(+)/bcl-2(+), BDNF(+), bcl-2(+), empty plasmid (EP), and no surgery (NS). The plasmids were intravitreally injected and electroporated into the left eye. Seven days later, optic nerve transection was performed in all groups except the NS group. Protein expression was examined using Western blotting, RGC survival was quantified using 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine perchlorate (DiI) retrograde labeling, and apoptosis was assessed using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) at multiple time points (7, 14, and 28 d after transfection). A significantly higher number of DiI (+) RGCs and lower number of apoptotic cells were observed in the BDNF(+)/bcl-2(+), BDNF(+), and bcl-2(+) groups compared to those in the EP group at all time points. The number of DiI (+) RGCs in the three treatment groups was significantly lower than that in the NS group. However, there were no significant differences among the three treatment groups. The protective effects of gene transfection tended to be strongest in the BDNF(+)/bcl-2(+) group, followed by the BDNF(+) group and then the bcl-2(+) group. Thus, all gene transfection treatments had a protective effect against the loss of DiI(+) RGCs induced by optic nerve transection but did not result in full recovery. This study also confirmed the value of in vivo electroporation. The findings of this pilot study provide a working base for the development of gene therapy for blinding optic nerve disorders. Show less