Identification of the impact of Focused Ultrasound Induced Blood-Brain Barrier Opening (FUS-BBBO) on brain-wide memory traces in Alzheimer's disease - PROJECT SUMMARY / ABSTRACT Alzheimer’s disease (AD) is a debilitating, neurodegenerative disease.52 There remains a dire need to develop novel treatments for cognitive loss in patients suffering from AD and AD Related Dementias (ADRD).59 Focused ultrasound (FUS) is a novel technique to deliver highly focused acoustic energy to a small brain region, noninvasively focally modulating brain function.3 Recent advances have demonstrated that FUS combined with microbubbles to reversibly open the blood-brain barrier (FUS-BBBO) holds promise as a novel therapeutic strategy to modulate brain circuits to improve health and cognitive function.44 However, there is a gap in knowledge in elucidating the molecular mechanisms of how FUS-BBBO can modulate neural ensembles, resulting in improved memory, which is especially relevant to AD and ADRD. Here, we present an innovative approach to elucidate the neuronal mechanisms of FUS-BBBO as a novel therapeutic for AD. Specifically, we will test the hypothesis that FUS-BBBO uniquely alters individual memory traces to improve contextual discrimination, a phenotype impaired in AD and ADRD. Our preliminary and recently published data are in support of our hypothesis; specifically, we show that FUS- BBBO is effective in mouse models of AD and AD patients.4,56 We will leverage the ArcCreERT2 mice,15 an indelible activity-dependent tagging line to selectively tag individual memory traces / engrams across the brain, in conjunction with numerous cutting-edge technologies to include: behavioral assays, FUS-BBBO and FUS- neuromodulation (FUS-nm), single nucleus RNA-sequencing (snRNA-seq), and brain-wide immunolabeling and network modeling. In Aim 1, we will identify how sham, FUS-BBBO, or FUS-nm, targeted to the hippocampus (HPC), influences the neural ensembles mediating contextual fear discrimination (CFD) in control (Ctrl) or APP/PS1 (Aim 1A) or PS19 (Aim 1B) x ArcCreERT2 x enhanced yellow fluorescent protein (eYFP) mice. In the CFD paradigm, mice are exposed to a shock in one context (context A), and their ability to discriminate between this aversive, shock-paired context and a similar but safe context (context B) will be tested over 10 days. Following the last behavioral exposure, brains will be processed using a recently developed brain-wide imaging pipeline that allows for whole-brain neural activity analyses of multiple ensembles with single-cell resolution.25,29,39 In Aim 2, Ctrl or APP/PS1 x ArcCreERT2 x Sun1-GFP mice will be administered a sham or FUS-BBBO procedure. Following the CFD assay, mice will be euthanized to capture the HPC neural ensembles impacted by FUS-BBBO. Nuclei will be profiled with snRNA-seq to identify how FUS-BBBO changes the molecular landscape of HPC engrams in the context of AD. In summary, these studies will establish a mechanistic framework for how FUS-BBBO improves cognitive loss and inform future therapeutic strategies targeting neural memory ensembles to treat cognitive disorders such as AD and ADRD.
