Andre Obenaus - US grants

The Imaging Core supports the following Specific Aims ofthe three scientific projects ofthe Center for Brain Hemorrhage Research: 1) provide neuroimaging for edema (T2-weighted, T2W1), blood (T2WI and suscepribility weighted imaging, SWI), diffusion tensor imaging for white matter abnormalities, cerebral perfusion using both dynamic susceptibility contrast (DSC) and arterial spin labeling (ASL) approaches including cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT) and time to peak (TTP) indices; 2) undertake analysis for the collected imaging data, including anatomical mapping of edema and blood, blood brain barrier (BBB) disruption, white matter changes, cerebral perfusion abnormalities; 3) provide a centralized location for Project Pi's and staff to access raw and analyzed datasets; 4) develop and implement computational routines as we have for other disease states (i.e. stroke, TBI) to automate and speed analysis throughput, and 5) provide statistical and computational support for imaging data comparisons to behavior, cell biology and vascular outcomes. Our comprehensive approach will provide novel data about common interrelationships between three brain models of hemorrhagic injury, Subarachnoid Hemorrhage (SAH), Intracerebral Hemorrhage (ICH), and Traumatic Brain Injury (TBI). Clinical neuroimaging is increasingly taking a significant role in assessment of SAH, ICH, and TBI. A unifying feature of these neurological disease states is the deposition of extravascular blood which is extremely toxic to the brain and leads to rupture ofthe blood brain barrier (BBB). This cascade of events results in development of edema, often with catastrophic outcomes. Numerous studies have demonstrated that rapid imaging ofthe extent and anatomical location of blood is critical for decision-making relative to potential therapeutic interventions. Thus, the Imaging Core has elected for these Projects to focus on early and late indices of brain injury and function: 1) edema, 2) extravascular blood, 3) cerebral perfusion, and 4) white matter function. The Imaging Core will 1) undertake non-invasive but functional measures of brain physiology using MR imaging, 2) use standard and novel computational analysis to maximize data extraction, and 3) use numerical analysis methods to identify common data from all cores (Behavioral, Imaging, Vascular) that emerge for SAH, ICH, and TBI.

Project Summary The increased risk of Alzheimer?s Disease (AD) in women compared to men has been widely reported, including increased prevalence and also severity of cognitive impairment in women with AD than men. Women also exhibit an accelerated rate of impairment. However, there is considerable debate as to the physiological basis for this increased susceptibility. One potential key candidate mechanism that may underlie this vulnerability is differences in synaptic structure and function. To examine this question, we have opted to utilize a preclinical mouse model that exhibits endophenotypes of AD as well as normal aging mice. In particular, the familial AD 5xFAD transgenic mouse model recapitulates many AD characteristics, including an early aggressive amyloid-ß (Aß) pathology in the cortex and hippocampus, regions known to be necessary for learning and memory. We will test our hypothesis that synaptic density represents a key source of vulnerability to AD pathology in females as compared to males. Three distinct Aims will test this hypothesis. First, Aim 1 will evaluate the temporal progression of behavioral decrements in 5xFAD (male/female) mice as well as wild type (WT) mice from 4 through 24 mo of age. In addition, memory processes and also long-term potentiation, a form of synaptic plasticity thought to underlie learning and memory, will be assessed at the same ages. Second, Aim 2 will use clinically relevant magnetic resonance diffusion tensor imaging (dMRI) to map brain learning and memory circuits, probing the hippocampus and related brain structures for connectivity. Third, Aim 3 will explore the use of positron emission tomography (PET) imaging with an 18F radioligand to probe the synaptic marker, synaptic vesicle glycoprotein 2A (S2VA) in our WT and 5xFAD cohort. Preliminary studies have demonstrated loss of S2VA labeling in human AD patients, but have not explored sex-specific alterations. In sum, this research proposal will define the accelerated sex-specific changes in synaptic connectivity, density and physiological function that underlie the increased vulnerability of females when AD pathology is present. Moreover, we will identify when this vulnerability emerges with the future goal of intervening to either prevent or slow the progression of AD pathology.

Summary Project The majority of traumatic brain injury (TBI) is mild in nature but is known to elicit long-term consequences, including emergence of dementia and accelerated age-related declines. The highest-at-risk group are children whose brains are still undergoing development. This proposal will investigate the short- and long-term, cellular and molecular changes in the brain following juvenile mTBI (jmTBI) with the goal to intelligently develop new therapeutic options. Caveolin-1 (Cav-1) is an abundant structural protein involved in caveolae formation and cell signaling which is expressed in cerebral endothelial cells and in astrocytes, key components of the neurovascular unit (NVU). Recent development of a compound to target the Caveolin Scaffolding Domain (CSD), a complex that compartmentalizes structural proteins (e.g. claudin-5) and signaling molecules (e.g. eNOS), has provided tools to explore the role of Cav-1 in acquired neurological disease. After stroke, we found increased Cav-1 expression and Cav-AP treatment was beneficial for post-injury recovery. However, consensus is lacking whether Cav-1 exhibits beneficial or deleterious actions in other acquired brain disorders, such as jmTBI. Our model of jmTBI exhibits accelerated loss of cognition associated with decreased vascular function over their lifespan. We therefore will test the hypothesis that dysfunction in neurovascular coupling after jmTBI can be prevented by modulation of Cav-1 signaling, blunting accelerated hippocampal and cortical aging. Aim 1 will demonstrate that Cav-1 is critical for maintaining NVU functionality. We examine the role of vascular Cav-1 in male & female jmTBI mice in normal (WT), vascular Cav-1 deficient mice (Cav-1-/-) and in Cav-AP treated mice. We believe that jmTBI mice treated with Cav-AP will exhibit vascular recovery, whereas the loss of Cav-1 will worsen NVU outcomes. In Aim 2 we will examine how Cav- 1 in reactive astrocyte processes influences progression of jmTBI. We will modulate Cav-1 expression directly in astrocytes by injecting AAV-GFAP-Cav-1-shRNA and AAV-GFAP-synCav-1 in control and injured mice and quantify vascular recovery and behavioral outcomes. Increased astrocytic Cav-1 will be associated with improved NVU properties and cognitive outcomes. In Aim 3 we will examine male & female mice over their lifespan and examining if increased Cav-1 blunts accelerated brain aging that we have observed after jmTBI. We will assess behavioral, neuroimaging and histological outcomes. jmTBI mice treated with Cav-AP will exhibit improved outcomes related to enhanced NVU function and integrity. In sum, the proposed research is a critical first step in examining the role of Cav-1 in jmTBI and if therapeutic intervention can lead to enhanced NVU stability and function and thereby moderate accelerated aging.

Project Summary / Abstract Blood vessels, from arteries to capillaries to venules and then to veins, contribute to fundamental physiological processes. However, the vascular responses for repair and restoration of microvascular networks after cortical brain injury are poorly understood, including how neuronal activity influences these processes. A major barrier to research is the poor accessibility of micro-vessels in the brain and associated technical difficulties. To overcome this barrier, we propose to use innovative imaging technologies that we have co-developed to investigate micro-vessel formation and re-growth in response to focal cortical injury. We have used light-weight head-mounted, miniaturized microscopes (?miniscopes?) to dynamically image the vasculature and associated cells with high spatial and temporal resolution. We will use cortical injury models by applying a controlled moderate impact to the mouse motor cortex. Combining in vivo longitudinal miniscope and 2-photon imaging, histological ?vessel painting? and perfusion-weighted magnetic resonance imaging (PWI MRI), we aim to achieve a deeper understanding of microvascular restoration following cortical injury. We will apply targeted optogenetic stimulation of excitatory neurons and specific inhibitory neurons to modulate microvascular repair in early and late phases of vessel re-growth. Our guiding hypothesis is that microvascular restoration and remodeling after cortical injury are regulated by vascularization sequences and cellular processes that are similarly observed in normal vasculogenesis during central nervous system development. In Aim 1, we will identify the time course and spatial pattern of vascular regrowth, and blood flow dynamics after focal cortical injury. Vascular networks and blood flow are visualized with fluorescent-labeled dextrans for in vivo imaging for quantitative measurements. In Aim 2, we will determine the role of endothelial cells in new blood vessel sprouting and the establishment of functional microvascular by imaging Tie2-Cre reporter mice during the first two weeks post- injury. We will also examine the influence of astrocytes and pericytes in vascular re-growth. In Aim 3, we will test the hypothesis that optogenetic stimulation of specific neuron types in a temporally controlled manner facilitates and enhances microvasculature restoration for post-injury repair. We will also examine if and how targeted modulation of neural activities modulate Wnt/ß-catenin and VEGF signaling mechanisms that are critical for micro-vessel re-growth. Behavioral testing will assess the outcomes of the optogenetic treatment. We have strong preliminary data that supports the premise for the proposed research for all aims. The proposed research will advance our understanding of the cellular and molecular mechanisms underlying cortical microvascular restoration and how neural stimulation enhances vascular network formation.