The Microvasculature in Alzheimer’s Disease: Viable Microvessels for Studies of Brain Endothelial and Glycocalyx Health

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ABSTRACT/SUMMARY Brain microvasculature is altered in Alzheimer’s Disease (AD), but there are few methods to examine cellular processes in living tissue. Viable brain microvessels (MV) can be isolated from whole brain tissue of subjects undergoing rapid autopsy (<12 hours post mortem) in the UW Neuropathology (NP) Core. The donor subjects in the UW NP Core have a clinical diagnosis of dementia or no dementia, and all brain specimens undergo extensive neuropathologic assessment. This proposal utilizes innovative methods to rapidly obtain and maintain viable brain MV for a minimum of 5 days in supportive liquid media under standard tissue culture conditions, which affords a unique opportunity to study the microvasculature in brains with and without AD. Many aspects of MV structure and composition contribute to interactions that are relevant to AD. For this R03, the focus is on the luminal surface and the 2 components that are the initial interface between the brain and the systemic circulation: 1) the brain microvascular endothelial cell (BEC), and 2) the glycocalyx, a dynamic gel-like layer of extracellular matrix (ECM) that lines the luminal surface of BEC. The following 2 hypotheses will be tested. First, MV from those with dementia have similar BEC-specific viability and overall metabolic activity, but increased prevalence of senescent BEC relative to MV from those without dementia. Second, MV from those with dementia have greater glycocalyx shedding, which reflects increased degradative enzymes, relative to MV from those without dementia. Samples and outcome measures will be initially examined based on the clinical diagnosis of dementia or no dementia, and then re-classified according to subsequent detailed neuropathologic criteria. Aim 1 will define how BEC from dementia and no dementia MV specimens differ with respect to outcome measures of BEC-specific viability, overall metabolic activity, and BEC senescence. Aim 2 will determine how the glycocalyx from dementia and no dementia MV differ in de novo synthesis of ECM and markers of ECM degradation. Studies of glycocalyx will focus on heparan sulfate proteoglycans (HSPGs) and hyaluronan (HA). Knowledge gained will provide the foundation for perturbation/intervention experiments that are feasible, and have therapeutic implications for the mitigation of deleterious MV changes with dementia.