11.17.11 CEN Healthcare Chris Schaffer Presentation

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    12-Jul-2015

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  • Alzheimers disease is the leading cause of dementia in the elderlyAuguste D., first Alzheimers patient described by Alois Alzheimer

  • Alzheimers is caused by neuronal loss due to neurotoxic effects of aggregated A-beta peptideK. Blennow, et al., Lancet (2006)Alzheimers pathologymolecular mechanisms

  • K. Blennow, et al., Lancet (2006)Alzheimers pathologymolecular mechanismsAlzheimers is caused by neuronal loss due to neurotoxic effects of aggregated A-beta peptide

  • A-beta is produced by neurons andcleared through the vasculature

  • Blood flow deficits to the brain also observed in Alzheimers patients

  • Blood flow deficits to the brain also observed in Alzheimers patients 20-30% decreased brain blood flow compared to non Alzheimer controls

    This blood flow decrease could be cognitively important, but the origin remains unclearWe used advanced imaging techniques to study disruptions in microvascular blood flow in mice that are engineered to get Alzheimers disease

  • Two-photon excitation of fluorescent dyes leads to emission that originates only from the focal volumeZ. Huang, et al., belfield.cos.ucf.edu/one vs two-photon excitation.html

  • Image is formed by scanning laser focus through the sample and recording fluorescence intensity

  • Image is formed by scanning laser focus through the sample and recording fluorescence intensity

  • Image fluorescently-labeled features in brain of anesthetized rodent with glass-covered craniotomy

  • Imaging fluorescent blood plasma yields a 3-D cortical micro-angiography

  • In vivo imaging of vasculature and amyloid plaques in AD mouse modelsplaques labeled by methoxy-X04vasculature with intravenous dye injectionAged APPswe/PS1 mice with craniotomies

  • Dye labels blood plasma, but not blood cells, allowing identification of flowing vs. stalled vessels

  • Fraction of capillaries with stalled blood flow increased to ~2% in mouse models of ADTemporary stalls that shift between capillary segments, rather than permanent occlusions2843 capillaries in 6 AD mice2475 capillaries in 4 WT mice

  • Labeling to distinguish red blood cells, leukocytes, and thrombi as potential cause of stallsleukocytes: rhodamine-6G and Hoechst

    thrombi: rhodamine-6G

    red blood cells: unlabeled

  • In vivo imaging of capillary stalls with rhodamine-6G and Hoechst labelingred - Texas-Red dextrangreen - rhodamine 6Gblue - methoxy-X04 and Hoescht

  • Majority of capillary stalls in AD mouse models are caused by leukocyte plugs

  • How does a single stalled capillary affect blood flow?N. Nishimura, et al., Nature Methods 3, 99 (2006) Laser injury to vessel triggers clottingMap changes in flow after capillary clotbaseline flowpost-clot flow

  • A single stalled capillary causes reduced blood flow in multiple downstream vessel branchesN. Nishimura, et al., Nature Methods 3, 99 (2006) Post-clot blood flow speed(fraction of baseline)

  • Map of blood vessels and amyloidplaques from AD mouse

  • Location of stalled capillaries

  • Simulate blood flow changes in capillaries downstream from plugged vessels

  • Simulate blood flow changes in capillaries downstream from plugged vessels

  • Simulate blood flow changes in capillaries downstream from plugged vessels

  • Increases in number of stalled capillaries causes decreases in average cerebral blood flow2% of capillaries stalled predicts a 30% decrease in flow compared to controls

  • Leukocyte plugging of capillary segments could explain blood flow deficits observed in ADIn humans, blood flow reduced by 20-30% compared to non-AD age-matched controls [1]In mouse models of AD, flow reduced by ~30% compared to wild-type animals [2]1. Farkas E, Luiten PG. (2001) Cerebral microvascular pathology in aging and Alzheimer's disease. Prog Neurobiol 64:575-6112. Niwa K, Kazama K, Younkin SG, Carlson GA, Iadecola C. (2002) Alterations in cerebral blood flow and glucose utilization in mice overexpressing the amyloid precursor protein. Neurobiol Dis 9:61-68

  • Summary2% of capillaries are stalled in AD mouse modelsStalls are caused by leukocytes plugging capillary segmentsThis rate of capillary stalling could produce ~30% decrease in cerebral blood flow, consistent with observations in humans and mouse models Suggests that A aggregates cause vascular inflammation that leads to firm adhesion of leukocytes to the endotheliumProvides a novel potential target for treatment of blood flow deficits in AD, which could improve cognitive function

  • Cyclic relationship between vascular stalls and A aggregates as a driver of AD progression

  • CollaboratorsCornellDr. Nozomi NishimuraCalvin KersbergenGabriel OtteJoan ZhouJeff BeverlyElizabeth Slack

    Weill Cornell Medical CollegeProf. Costantino Iadecola

  • AcknowledgementsThanks to William Klunk for donation of methoxy-X04

  • To occlude a small blood vessel, we optically injure the vessel to initiate endogenous clotting cascadeN. Nishimura, et al., Nature Methods 3, 99 (2006)

  • Femtosecond laser irradiation to produce a clot in a targeted, sub-surface brain capillary