Alzheimer's Disease Therapy via the MR Image-Guided Deletion of Microglial SHIP-1 with Focused Ultrasound - Microglia play a key role in Alzheimer’s disease (AD) pathogenesis and represent promising targets in the development of new Alzheimer’s Disease treatments. INPP5D, a gene that encodes for the SH2-domain- containing inositol phosphatase SHIP-1 and is predominantly expressed by microglia in the brain, has been recently uncovered as a late-onset Alzheimer’s disease genetic risk factor. Furthermore, we have recently shown that SHIP-1 deletion in brain-resident macrophages leads to greatly enhanced mobilization of microglia to amyloid beta (A) plaques, augmented A phagocytosis, and improved neuronal health and cognitive function. These results have led us to formulate the hypothesis that SHIP-1 is both a negative regulator of protective microglial responses in A amyloidosis and a novel therapeutic target for ameliorating Alzheimer’s-related disease. However, because global inhibition of SHIP-1 may cause multi-organ inflammation, its inhibition must entail selective brain/microglial targeting. To achieve this selective targeting, in this proposal, we will develop and deploy MR image-guided focused ultrasound (FUS), in combination with microbubbles (MBs), to deliver SHIP-1 neutralizing therapies across the blood-brain barrier (BBB) to microglia to improve A phagocytosis and restore neuronal health. We propose two specific aims. In Aim 1, we will first develop a non-invasive, MR image-guided, FUS- mediated, gene delivery strategy that yields efficient microglial transfection. To this end, we will interrogate “acoustically activated” compositions of matter that involve (i) directly binding plasmid to cationic MBs, (ii) co- injecting highly-PEGylated non-viral gene-bearing nanoparticles with MBs, and (iii) coupling gene-bearing nanoparticles to MBs via thiol-maleimide interactions. FUS parameters to oscillate MBs, open the BBB, and deliver transgene will be adjusted for each system to determine its capacity to transfect microglia. The best performing system will be advanced to Aim 2, wherein we will inhibit the progression of Alzheimer’s-related disease in mice by blocking microglial SHIP-1 via the delivery CRISPR-Cas9 plasmids for SHIP-1 deletion to microglia in Alzheimer’s disease mice. We will test this therapeutic strategy in 5xFAD mice, as well as in models of AD that develop progressive A amyloidosis (APPSAA mice), tauopathy alone (PS19 mice), and combined A and tau pathology (APPSAA mice crossed with PS19 mice to generate APPSAA x PS19 mice). The potential for the treatment to reduce A deposition, phospho-tau, neurofibrillary tangle, neuroinflammation, and CNS pathology, and improve neural function, will be assessed. Morris water maze (MWM) and Y tests will be used to assess the ability of the treatment to hinder cognitive decline in each of the AD mouse models. Ultimately, to our knowledge, this will be the first ever attempt to implement FUS-directed gene delivery technology to selectively modulate microglial responses and limit Alzheimer’s-related disease progression.
