Protocol to measure apoptosis-associated speck-like protein containing a CARD specks in human cerebrospinal fluid via imaging flow cytometry

Apoptosis-associated speck-like protein containing a c-terminal caspase activation and recruitment domain (ASC) specks are elevated in the cerebrospinal fluid (CSF) of Alzheimer's disease and related dementias (AD/ADRDs) patients. Here, we present a flow cytometry protocol to quantify ASC specks. We describe steps for fluorescently labeling ASC specks using antibody technology, visualizing with imaging flow cytometry, and gating based on physical characteristics. CSF ASC specks levels positively correlate with phosphorylated tau (Thr181) and negatively correlate with amyloid β ratio (42/40), thus serving as a neuroinflammatory biomarker for diagnosing AD/ADRDs. For complete details on the use and execution of this protocol, please refer to Jiang et al.1.

A trichotomy method for defining homogeneous subgroups in a dementia population

INTRODUCTION

Diagnosis of dementia in the aging brain is confounded by the presence of multiple pathologies. Mixed dementia (MX), a combination of Alzheimer's disease (AD) proteins with vascular disease (VD), is frequently found at autopsy, and has been difficult to diagnose during life. This report develops a method for separating the MX group and defining preclinical AD (presence of AD factors with normal cognition) and preclinical VD subgroups (presence of white matter damage with normal cognition).

METHODS

Clustering was based on three diagnostic axes: (1) AD factor (ADF) derived from cerebrospinal fluid proteins (Aβ42 and pTau), (2) VD factor (VDF) calculated from mean free water and peak width of skeletonized mean diffusivity in the white matter, and (3) Cognition (Cog) based on memory and executive function. The trichotomy method was applied to an Alzheimer's Disease Neuroimaging Initiative cohort (N = 538).

RESULTS

Eight biologically defined subgroups were identified which included the MX group with both high ADF and VDF (9.3%) and a preclinical VD group (3.9%), and a preclinical AD group (13.6%). Cog is significantly associated with both ADF and VDF, and the partial-correlation remains significant even when the effect of the other variable is removed (r(Cog, ADF/VDF removed) = 0.46, p < 10-28 and r(Cog, VDF/ADF removed) = 0.24, p < 10-7 ).

DISCUSSION

The trichotomy method creates eight biologically characterized patient groups, which includes MX, preclinical AD, and preclinical VD subgroups. Further longitudinal studies are needed to determine the utility of the 3-way clustering method with multimodal biological biomarkers.

Placental growth factor as a sensitive biomarker for vascular cognitive impairment

INTRODUCTION

High-performing biomarkers measuring the vascular contributions to cognitive impairment and dementia are lacking.

METHODS

Using a multi-site observational cohort study design, we examined the diagnostic accuracy of plasma placental growth factor (PlGF) within the MarkVCID Consortium (n = 335; CDR 0-1). Subjects underwent clinical evaluation, cognitive testing, MRI, and blood sampling as defined by Consortium protocols.

RESULTS

In the prospective population of 335 subjects (72.2 ± 7.8 years of age, 49.3% female), plasma PlGF (pg/mL) shows an ordinal odds ratio (OR) of 1.16 (1.07-1.25; P = .0003) for increasing Fazekas score and ordinal OR of 1.22 (1.14-1.32; P < .0001) for functional cognitive impairment measured by the Clinical Dementia Rating scale. We achieved the primary study outcome of a site-independent association of plasma PlGF (pg/mL) with white matter injury and cognitive impairment in two of three study cohorts. Secondary outcomes using the full MarkVCID cohort demonstrated that plasma PlGF can significantly discriminate individuals with Fazekas ≥ 2 and CDR = 0.5 (area under the curve [AUC] = 0.74) and CDR = 1 (AUC = 0.89) from individuals with CDR = 0.

DISCUSSION

Plasma PlGF measured by standardized immunoassay functions as a stable, reliable, diagnostic biomarker for cognitive impairment associated with substantial white matter burden.

Blood-brain barrier disruption measured by albumin index correlates with inflammatory fluid biomarkers

Blood-brain barrier (BBB) permeability can be measured by the ratio of albumin in cerebrospinal fluid (CSF) and blood and by dynamic contrast-enhanced MRI (DCEMRI). Albumin is a large molecule measured in CSF and blood to form the albumin index (Qalb), which is a global measure of BBB permeability, while the smaller Gadolinium molecule measures regional transfer (Ktrans); few studies have directly compared them in the same patients. We used both methods as part of a study of mechanisms of white matter injury in patients with different forms of dementia. In addition, we also measured biomarkers for inflammation, including proteases, angiogenic growth factors, and cytokines, and correlated them with the BBB results. We found that there was no correlation between Qalb and Ktrans. The Qalb was associated with the matrix metalloproteinases (MMP-2, MMP-3, and MMP-10), the angiogenic factors (VEGF-C and PlGF), and the cytokines (IL-6, IL-8 and TNF-α). On the other hand, Ktrans was associated with the diffusion measures, mean free water and PSMD, which indicate white matter injury. Our results show that the Qalb and Ktrans measure different aspects of BBB permeability, with albumin being a measure of inflammatory BBB opening and Ktrans indicating white matter injury.

Multi-Site Cross-Site Inter-Rater and Test-Retest Reliability and Construct Validity of the MarkVCID White Matter Hyperintensity Growth and Regression Protocol

BACKGROUND

White matter hyperintensities (WMH) that occur in the setting of vascular cognitive impairment and dementia (VCID) may be dynamic increasing or decreasing volumes or stable over time. Quantifying such changes may prove useful as a biomarker for clinical trials designed to address vascular cognitive-impairment and dementia and Alzheimer's Disease.

OBJECTIVE

Conducting multi-site cross-site inter-rater and test-retest reliability of the MarkVCID white matter hyperintensity growth and regression protocol.

METHODS

The NINDS-supported MarkVCID Consortium evaluated a neuroimaging biomarker developed to track WMH change. Test-retest and cross-site inter-rater reliability of the protocol were assessed. Cognitive test scores were analyzed in relation to WMH changes to explore its construct validity.

RESULTS

ICC values for test-retest reliability of WMH growth and regression were 0.969 and 0.937 respectively, while for cross-site inter-rater ICC values for WMH growth and regression were 0.995 and 0.990 respectively. Word list long-delay free-recall was negatively associated with WMH growth (p < 0.028) but was not associated with WMH regression.

CONCLUSIONS

The present data demonstrate robust ICC validity of a WMH growth/regression protocol over a one-year period as measured by cross-site inter-rater and test-retest reliability. These data suggest that this approach may serve an important role in clinical trials of disease-modifying agents for VCID that may preferentially affect WMH growth, stability, or regression.

MRI free water as a biomarker for cognitive performance: Validation in the MarkVCID consortium

Introduction

To evaluate the clinical validity of free water (FW), a diffusion tensor imaging-based biomarker kit proposed by the MarkVCID consortium, by investigating the association between mean FW (mFW) and executive function.

Methods

Baseline mFW was related to a baseline composite measure of executive function (EFC), adjusting for relevant covariates, in three MarkVCID sub-cohorts, and replicated in five, large, independent legacy cohorts. In addition, we tested whether baseline mFW predicted accelerated EFC score decline (mean follow-up time: 1.29 years).

Results

Higher mFW was found to be associated with lower EFC scores in MarkVCID legacy and sub-cohorts (p-values < 0.05). In addition, higher baseline mFW was associated significantly with accelerated decline in EFC scores (p = 0.0026).

Discussion

mFW is a sensitive biomarker of cognitive decline, providing a strong clinical rational for its use as a marker of white matter (WM) injury in multi-site observational studies and clinical trials of vascular cognitive impairment and dementia (VCID).

Willis Lecture: Biomarkers for Inflammatory White Matter Injury in Binswanger Disease Provide Pathways to Precision Medicine

Binswanger disease is the small vessel form of vascular cognitive impairment and dementia. Deposition of Alzheimer disease proteins can begin in midlife and progress slowly, whereas aging of the vasculature also can begin in midlife, continuing to progress into old age, making mixed dementia the most common type of dementia. Biomarkers facilitate the early diagnosis of dementias. It is possible to diagnose mixed dementia before autopsy with biomarkers for vascular disease derived from diffusor tensor images on magnetic resonance imaging and Alzheimer disease proteins, Aβ (amyloid β), and phosphorylated tau, in cerebrospinal fluid or in brain with positron emission tomography. The presence of vascular disease accelerates cognitive decline. Both misfolded proteins and vascular disease promote inflammation, which can be detected in cerebrospinal fluid by the presence of MMPs (matrix metalloproteinases), angiogenic growth factors, and cytokines. MMPs disrupt the blood-brain barrier and break down myelin, producing Binswanger disease's 2 main pathological features. Advances in detecting biomarkers in plasma will provide early detection of dementia and aided by machine learning and artificial intelligence, will enhance diagnosis and form the basis for early treatments.

Apoptosis-associated speck-like protein containing a CARD-mediated release of matrix metalloproteinase 10 stimulates a change in microglia phenotype

Inflammation contributes to amyloid-β and tau pathology in Alzheimer's disease (AD). Microglia facilitate an altered immune response that includes microgliosis, upregulation of inflammasome proteins, and elevation of matrix-metalloproteinases (MMPs). Studies of cerebrospinal fluid (CSF) and blood in dementia patients show upregulation of two potential biomarkers of inflammation at the cellular level, MMP10 and apoptosis-associated speck-like protein containing a CARD (ASC). However, little is known about their relationship in the context of brain inflammation. Therefore, we stimulated microglia cultures with purified insoluble ASC speck aggregates and MMP10 to elucidate their role. We found that ASC specks altered microglia shape and stimulated the release of MMP3 and MMP10. Furthermore, MMP10 stimulated microglia released additional MMP10 along with the inflammatory cytokines, tumor-necrosis factor-α (TNFα), Interleukin 6 (IL-6), and CXCL1 CXC motif chemokine ligand 1 (CXCL1). A broad-spectrum MMP inhibitor, GM6001, prevented TNFα release. With these results, we conclude that MMP10 and ASC specks act on microglial cells to propagate inflammation.

Shared Inflammatory Pathology of Stroke and COVID-19

Though COVID-19 is primarily characterized by symptoms in the periphery, it can also affect the central nervous system (CNS). This has been established by the association between stroke and COVID-19. However, the molecular mechanisms that cause stroke related to a COVID-19 infection have not been fully explored. More specifically, stroke and COVID-19 exhibit an overlap of molecular mechanisms. These similarities provide a way to better understand COVID-19 related stroke. We propose here that peripheral macrophages upregulate inflammatory proteins such as matrix metalloproteinases (MMPs) in response to SARS-CoV-2 infection. These inflammatory molecules and the SARS-CoV-2 virus have multiple negative effects related to endothelial dysfunction that results in the disruption of the blood-brain barrier (BBB). Finally, we discuss how the endothelial blood-brain barrier injury alters central nervous system function by leading to astrocyte dysfunction and inflammasome activation. Our goal is to elucidate such inflammatory pathways, which could provide insight into therapies to combat the negative neurological effects of COVID-19.

Instrumental validation of free water, peak-width of skeletonized mean diffusivity, and white matter hyperintensities: MarkVCID neuroimaging kits

Introduction

To describe the protocol and findings of the instrumental validation of three imaging-based biomarker kits selected by the MarkVCID consortium: free water (FW) and peak width of skeletonized mean diffusivity (PSMD), both derived from diffusion tensor imaging (DTI), and white matter hyperintensity (WMH) volume derived from fluid attenuation inversion recovery and T1-weighted imaging.

Methods

The instrumental validation of imaging-based biomarker kits included inter-rater reliability among participating sites, test-retest repeatability, and inter-scanner reproducibility across three types of magnetic resonance imaging (MRI) scanners using intra-class correlation coefficients (ICC).

Results

The three biomarkers demonstrated excellent inter-rater reliability (ICC >0.94, P-values < .001), very high agreement between test and retest sessions (ICC >0.98, P-values < .001), and were extremely consistent across the three scanners (ICC >0.98, P-values < .001).

Discussion

The three biomarker kits demonstrated very high inter-rater reliability, test-retest repeatability, and inter-scanner reproducibility, offering robust biomarkers suitable for future multi-site observational studies and clinical trials in the context of vascular cognitive impairment and dementia (VCID).

What does aducanumab treatment of Alzheimer's disease mean for research on vascular cognitive disorders?

•Controversial registration of aducanumab for Alzheimer's Disease•Aducanumab is the subject of post-licensing observational studies aiming to follow the effects of the drug•Given the high prevalence of cerebrovascular pathology it is important that these studies do not ignore vascular cognitive disorders•The studies may give detailed phenotyping data that may lead to knowledge of targets for treatments of patients with vascular cognitive disorders.

Proteopathic tau primes and activates interleukin-1β via myeloid-cell-specific MyD88- and NLRP3-ASC-inflammasome pathway

Pathological hyperphosphorylation and aggregation of tau (pTau) and neuroinflammation, driven by interleukin-1β (IL-1β), are the major hallmarks of tauopathies. Here, we show that pTau primes and activates IL-1β. First, RNA-sequence analysis suggests paired-helical filaments (PHFs) from human tauopathy brain primes nuclear factor κB (NF-κB), chemokine, and IL-1β signaling clusters in human primary microglia. Treating microglia with pTau-containing neuronal media, exosomes, or PHFs causes IL-1β activation, which is NLRP3, ASC, and caspase-1 dependent. Suppression of pTau or ASC reduces tau pathology and inflammasome activation in rTg4510 and hTau mice, respectively. Although the deletion of MyD88 prevents both IL-1β expression and activation in the hTau mouse model of tauopathy, ASC deficiency in myeloid cells reduces pTau-induced IL-1β activation and improves cognitive function in hTau mice. Finally, pTau burden co-exists with elevated IL-1β and ASC in autopsy brains of human tauopathies. Together, our results suggest pTau activates IL-1β via MyD88- and NLRP3-ASC-dependent pathways in myeloid cells, including microglia.

Inflammatory Biomarkers Aid in Diagnosis of Dementia

Dual pathology of Alzheimer's disease (AD) and vascular cognitive impairment and dementia (VCID) commonly are found together at autopsy, but mixed dementia (MX) is difficult to diagnose during life. Biological criteria to diagnose AD have been defined, but are not available for vascular disease. We used the biological criteria for AD and white matter injury based on MRI to diagnose MX. Then we measured multiple biomarkers in CSF and blood with multiplex biomarker kits for proteases, angiogenic factors, and cytokines to explore pathophysiology in each group. Finally, we used machine learning with the Random forest algorithm to select the biomarkers of maximal importance; that analysis identified three proteases, matrix metalloproteinase-10 (MMP-10), MMP-3 and MMP-1; three angiogenic factors, VEGF-C, Tie-2 and PLGF, and three cytokines interleukin-2 (IL-2), IL-6, IL-13. To confirm the clinical importance of the variables, we showed that they correlated with results of neuropsychological testing.

A double-dichotomy clustering of dual pathology dementia patients

INTRODUCTION

Subcortical ischemic vascular disease (SIVD) and Alzheimer's disease (AD) related dementia can coexist in older subjects, leading to mixed dementia (MX). Identification of dementia sub-groups is important for designing proper treatment plans and clinical trials.

METHOD

An Alzheimer's disease severity (ADS) score and a vascular disease severity (VDS) score are calculated from CSF and MRI biomarkers, respectively. These scores, being sensitive to different Alzheimer's and vascular disease processes are combined orthogonally in a double-dichotomy plot. This formed an objective basis for clustering the subjects into four groups, consisting of AD, SIVD, MX and leukoaraiosis (LA). The relationship of these four groups is examined with respect to cognitive assessments and clinical diagnosis.

RESULTS

Cluster analysis had at least 83% agreement with the clinical diagnosis for groups based either on Alzheimer's or on vascular sensitive biomarkers, and a combined agreement of 68.8% for clustering the four groups. The VDS score was correlated to executive function (r = -0.28, p < 0.01) and the ADS score to memory function (r = -0.35, p < 0.002) after adjusting for age, sex, and education. In the subset of patients for which the cluster scores and clinical diagnoses agreed, the correlations were stronger (VDS score-executive function: r = -0.37, p < 0.006 and ADS score-memory function: r = -0.58, p < 0.0001).

CONCLUSIONS

The double-dichotomy clustering based on imaging and fluid biomarkers offers an unbiased method for identifying mixed dementia patients and selecting better defined sub-groups. Differential correlations with neuropsychological tests support the hypothesis that the categories of dementia represent different etiologies.

Genetic Deletion or Pharmacological Inhibition of Cyclooxygenase-2 Reduces Blood-Brain Barrier Damage in Experimental Ischemic Stroke

Cyclooxygenase (COX)-2 and matrix metalloproteinase (MMP)-9 are two crucial mediators contributing to blood-brain barrier (BBB) damage during cerebral ischemia. However, it is not known whether MMP-9 activation is involved in COX-2-mediated BBB disruption in ischemic stroke. In this study, we hypothesized that genetic deletion or pharmacological inhibition of COX-2 reduces BBB damage by reducing MMP-9 activity in a mouse model of ischemic stroke. Male COX-2 knockout (COX-2^-/-) and wild-type (WT) mice were subjected to 60 min of middle cerebral artery occlusion (MCAO) followed by 24 h of reperfusion. Genetic deletion of COX-2 or post-ischemic treatment with CAY10404, a highly selective COX-2 inhibitor, significantly reduced BBB damage and hemorrhagic transformation, as assessed by immunoglobulin G (IgG) extravasation and brain hemoglobin (Hb) levels, respectively. Immunoblotting analysis showed that tight junction proteins (TJPs) zonula occludens (ZO)-1 and occludin as well as junctional adhesion molecule-A (JAM-A) and the basal lamina protein collagen IV were dramatically reduced in the ischemic brain. Stroke-induced loss of these BBB structural proteins was significantly attenuated in COX-2^-/- mice. Similarly, stroke-induced loss of ZO-1 and occludin was significantly attenuated by CAY10404 treatment. Ischemia-induced increase in MMP-9 protein levels in the ipsilateral cerebral cortex was significantly reduced in COX-2^-/- mice. Stroke induced a dramatic increase in MMP-9 enzymatic activity in the ischemic cortex, which was markedly reduced by COX-2 gene deficiency or pharmacological inhibition with CAY10404. Levels of myeloperoxidase (MPO, an indicator of neutrophil infiltration into the brain parenchyma), neutrophil elastase (NE), and lipocalin-2 (LCN2, also known as neutrophil gelatinase-associated lipocalin), measured by western blot and specific ELISA kits, respectively, were markedly increased in the ischemic brain. Increased levels of markers for neutrophil infiltration were significantly reduced in COX-2^-/- mice compared with WT controls following stroke. Altogether, neurovascular protective effects of COX-2 blockade are associated with reduced BBB damage, MMP-9 expression/activity and neutrophil infiltration. Our study shows for the first time that MMP-9 is an important downstream effector contributing to COX-2-mediated neurovascular damage in ischemic stroke. Targeting the COX-2/MMP-9 pathway could represent a promising strategy to reduce neuroinflammatory events in order to preserve the BBB integrity and ameliorate ischemic stroke injury.

Discriminating VCID subgroups: A diffusion MRI multi-model fusion approach

BACKGROUND

Vascular cognitive impairment and dementia (VCID) and Alzheimer's disease are predominant diseases among the aging population resulting in decline of various cognitive domains. Diffusion weighted MRI (DW-MRI) has been shown to be a promising aid in the diagnosis of such diseases. However, there are various models of DW-MRI and the interpretation of diffusion metrics depends on the model used in fitting data. Most previous studies are entirely based on parameters calculated from a single diffusion model.

NEW METHOD

We employ a data fusion framework wherein diffusion metrics from different models such as diffusion tensor imaging, diffusion kurtosis imaging and constrained spherical deconvolution model are fused using well known blind source separation approach to investigate white matter microstructural changes in population comprising of controls and VCID subgroups. Multiple comparisons between subject groups and prediction analysis using features from individual models and proposed fusion model are carried out to evaluate performance of proposed method.

RESULTS

Diffusion features from individual models successfully distinguished between controls and disease groups, but failed to differentiate between disease groups, whereas fusion approach showed group differences between disease groups too. WM tracts showing significant differences are superior longitudinal fasciculus, anterior thalamic radiation, arcuate fasciculus, optic radiation and corticospinal tract.

COMPARISON WITH EXISTING METHOD

ROC analysis showed increased AUC for fusion (AUC = 0.913, averaged across groups and tracts) compared to that of uni-model features (AUC = 0.77) demonstrating increased sensitivity of proposed method.

CONCLUSION

Overall our results highlight the benefits of multi-model fusion approach, providing improved sensitivity in discriminating VCID subgroups.

Editorial: WHO Guidelines on Community-Level Interventions to Manage Declines in Intrinsic Capacity: The Road for Preventing Cognitive Declines in Older Age?

The Concept of decline in “Intrinsic Capacities” (IC) from W.H.O Current Aging program (1, 2) prompts us to reposition prevention of cognitive decline and memory disorders with advancing age. In the new conceptual framework, Healthy Ageing is not defined as life free of diseases (disease can occur at any age) but, rather, as «the process of developing and maintaining the functional ability that enables wellbeing in older age» (1). This is a significant departure from the key strategy of current health care systems that are mainly designed to identify and treat acute episodes of (and chronic) illnesses, rather than maintaining individuals’ Intrinsic Capacities IC across the life course (1). Hence, there is an urgent need to change the strategic emphasis of health care systems from focusing on acute conditions to promoting integrated care aimed at maintaining functional abilities and well-being as an effective approach to promote healthy ageing.

Biomarkers identify the Binswanger type of vascular cognitive impairment

Binswanger's disease is a form of subcortical ischemic vascular disease (SIVD-BD) with extensive white matter changes. To test the hypothesis that biomarkers could improve classification of SIVD-BD, we recruited 62 vascular cognitive impairment and dementia (VCID) patients. Multimodal biomarkers were collected at entry into the study based on clinical and neuropsychological testing, multimodal magnetic resonance imaging (MRI), and cerebrospinal fluid (CSF) analysis. The patients' diagnoses were confirmed by long-term follow-up, and they formed a "training set" to test classification methods, including (1) subcortical ischemic vascular disease score (SIVDS), (2) exploratory factor analysis (EFA), (3) logistic regression (LR), and (4) random forest (RF). A subsequently recruited cohort of 43 VCID patients with provisional diagnoses were used as a "test" set to calculate the probability of SIVD-BD based on biomarkers obtained at entry. We found that N-acetylaspartate (NAA) on proton magnetic resonance spectroscopy (¹H-MRS) was the best variable for classification, followed by matrix metalloproteinase-2 in CSF and blood-brain barrier permeability on MRI. Both LR and RF performed better in diagnosing SIVD-BD than either EFA or SIVDS. Two-year follow-up of provisional diagnosis patients confirmed the accuracy of statistically derived classifications. We propose that biomarker-based classification methods could diagnose SIVD-BD patients earlier, facilitating clinical trials.

A Multimodal Approach to Stratification of Patients with Dementia: Selection of Mixed Dementia Patients Prior to Autopsy

Alzheimer’s disease (AD) and vascular cognitive impairment and dementia (VCID) are major causes of dementia, and when combined lead to accelerated cognitive loss. We hypothesized that biomarkers of neurodegeneration and neuroinflammation could be used to stratify patients into diagnostic groups. Diagnosis of AD can be made biologically with detection of amyloid and tau proteins in the cerebrospinal fluid (CSF) and vascular disease can be identified with diffusion tensor imaging (DTI). We recruited patients with cognitive complaints and made an initial clinical diagnosis. After one year of follow-up we made a biological diagnosis based on the use of biomarkers obtained from DTI, CSF AD, and inflammatory proteins, and neuropsychological testing. Patients with AD had primarily findings of neurodegeneration (CSF showing increased tau and reduced amyloid), while patients with neuroinflammation had abnormal DTI mean diffusion (MD) in the white matter. Using the biological biomarkers resulted in many of the clinically diagnosed AD patients moving into mixed dementia (MX). Biomarkers of inflammation tended to be higher in the MX than in either the AD or VCID, suggesting dual pathology leads to increased inflammation, which could explain accelerated cognitive decline in that group.

In search of multimodal brain alterations in Alzheimer's and Binswanger's disease

Structural and functional brain abnormalities have been widely identified in dementia, but with variable replicability and significant overlap. Alzheimer's disease (AD) and Binswanger's disease (BD) share similar symptoms and common brain changes that can confound diagnosis. In this study, we aimed to investigate correlated structural and functional brain changes in AD and BD by combining resting-state functional magnetic resonance imaging (fMRI) and diffusion MRI. A group independent component analysis was first performed on the fMRI data to extract 49 intrinsic connectivity networks (ICNs). Then we conducted a multi-set canonical correlation analysis on three features, functional network connectivity (FNC) between ICNs, fractional anisotropy (FA) and mean diffusivity (MD). Two inter-correlated components show significant group differences. The first component demonstrates distinct brain changes between AD and BD. AD shows increased cerebellar FNC but decreased thalamic and hippocampal FNC. Such FNC alterations are linked to the decreased corpus callosum FA. AD also has increased MD in the frontal and temporal cortex, but BD shows opposite alterations. The second component demonstrates specific brain changes in BD. Increased FNC is mainly between default mode and sensory regions, while decreased FNC is mainly within the default mode domain and related to auditory regions. The FNC changes are associated with FA changes in posterior/middle cingulum cortex and visual cortex and increased MD in thalamus and hippocampus. Our findings provide evidence of linked functional and structural deficits in dementia and suggest that AD and BD have both common and distinct changes in white matter integrity and functional connectivity.

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This is the first study to explore multi-modalities changes in different dementia.

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A multimodal fusion method is applied to identify joint components.

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Brain abnormalities in different modalities are highly correlated.

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Alzheimer's and Binswanger's disease share similar brain changes.

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Alzheimer's and Binswanger's disease also have distinct brain changes.

Neuroinflammation: friend and foe for ischemic stroke

Stroke, the third leading cause of death and disability worldwide, is undergoing a change in perspective with the emergence of new ideas on neurodegeneration. The concept that stroke is a disorder solely of blood vessels has been expanded to include the effects of a detrimental interaction between glia, neurons, vascular cells, and matrix components, which is collectively referred to as the neurovascular unit. Following the acute stroke, the majority of which are ischemic, there is secondary neuroinflammation that both promotes further injury, resulting in cell death, but conversely plays a beneficial role, by promoting recovery. The proinflammatory signals from immune mediators rapidly activate resident cells and influence infiltration of a wide range of inflammatory cells (neutrophils, monocytes/macrophages, different subtypes of T cells, and other inflammatory cells) into the ischemic region exacerbating brain damage. In this review, we discuss how neuroinflammation has both beneficial as well as detrimental roles and recent therapeutic strategies to combat pathological responses. Here, we also focus on time-dependent entry of immune cells to the ischemic area and the impact of other pathological mediators, including oxidative stress, excitotoxicity, matrix metalloproteinases (MMPs), high-mobility group box 1 (HMGB1), arachidonic acid metabolites, mitogen-activated protein kinase (MAPK), and post-translational modifications that could potentially perpetuate ischemic brain damage after the acute injury. Understanding the time-dependent role of inflammatory factors could help in developing new diagnostic, prognostic, and therapeutic neuroprotective strategies for post-stroke inflammation.

Altered static and dynamic functional network connectivity in Alzheimer's disease and subcortical ischemic vascular disease: shared and specific brain connectivity abnormalities

Subcortical ischemic vascular disease (SIVD) is a major subtype of vascular dementia with features that overlap clinically with Alzheimer's disease (AD), confounding diagnosis. Neuroimaging is a more specific and biologically based approach for detecting brain changes and thus may help to distinguish these diseases. There is still a lack of knowledge regarding the shared and specific functional brain abnormalities, especially functional connectivity changes in relation to AD and SIVD. In this study, we investigated both static functional network connectivity (sFNC) and dynamic FNC (dFNC) between 54 intrinsic connectivity networks in 19 AD patients, 19 SIVD patients, and 38 age-matched healthy controls. The results show that both patient groups have increased sFNC between the visual and cerebellar (CB) domains but decreased sFNC between the cognitive-control and CB domains. SIVD has specifically decreased sFNC within the sensorimotor domain while AD has specifically altered sFNC between the default-mode and CB domains. In addition, SIVD has more occurrences and a longer dwell time in the weakly connected dFNC states, but with fewer occurrences and a shorter dwell time in the strongly connected dFNC states. AD has both similar and opposite changes in certain dynamic features. More importantly, the dynamic features are found to be associated with cognitive performance. Our findings highlight similar and distinct functional connectivity alterations in AD and SIVD from both static and dynamic perspectives and indicate dFNC to be a more important biomarker for dementia since its progressively altered patterns can better track cognitive impairment in AD and SIVD.

Hypoxia promotes tau hyperphosphorylation with associated neuropathology in vascular dysfunction

BACKGROUND

Hypertension-induced microvascular brain injury is a major vascular contributor to cognitive impairment and dementia. We hypothesized that chronic hypoxia promotes the hyperphosphorylation of tau and cell death in an accelerated spontaneously hypertensive stroke prone rat model of vascular cognitive impairment.

METHODS

Hypertensive male rats (n = 13) were fed a high salt, low protein Japanese permissive diet and were compared to Wistar Kyoto control rats (n = 5).

RESULTS

Using electron paramagnetic resonance oximetry to measure in vivo tissue oxygen levels and magnetic resonance imaging to assess structural brain damage, we found compromised gray (dorsolateral cortex: p = .018) and white matter (corpus callosum: p = .016; external capsule: p = .049) structural integrity, reduced cerebral blood flow (dorsolateral cortex: p = .005; hippocampus: p < .001; corpus callosum: p = .001; external capsule: p < .001) and a significant drop in cortical oxygen levels (p < .05). Consistently, we found reduced oxygen carrying neuronal neuroglobin (p = .008), suggestive of chronic cerebral hypoperfusion in high salt-fed rats. We also observed a corresponding increase in free radicals (NADPH oxidase: p = .013), p-Tau (pThr231) in dorsolateral cortex (p = .011) and hippocampus (p = .003), active interleukin-1β (p < .001) and neurodegeneration (dorsolateral cortex: p = .043, hippocampus: p = .044). Human patients with subcortical ischemic vascular disease, a type of vascular dementia (n = 38; mean age = 68; male/female ratio = 23/15) showed reduced hippocampal volumes and cortical shrinking (p < .05) consistent with the neuronal cell death observed in our hypertensive rat model as compared to healthy controls (n = 47; mean age = 63; male/female ratio = 18/29).

CONCLUSIONS

Our data support an association between hypertension-induced vascular dysfunction and the sporadic occurrence of phosphorylated tau and cell death in the rat model, correlating with patient brain atrophy, which is relevant to vascular disease.

Binswanger's disease: biomarkers in the inflammatory form of vascular cognitive impairment and dementia

Vascular cognitive impairment and dementia (VCID) is a major public health concern because of the increased incidence of vascular disease in the aging population and the impact of vascular disease on Alzheimer's disease. VCID is a heterogeneous group of diseases for which there are no proven treatments. Biomarkers can be used to select more homogeneous populations. Small vessel disease is the most prevalent form of VCID and is the optimal form for treatment trials because there is a progressive course with characteristic pathological changes. Subcortical ischemic vascular disease of the Binswanger type (SIVD-BD) has a characteristic set of features that can be used both to identify patients and to follow treatment. SIVD-BD patients have clinical, neuropsychological, cerebrospinal fluid (CSF) and imaging features that can be used as biomarkers. No one feature is diagnostic, but a multimodal approach defines the SIVD-BD spectrum disorder. The most important features are large white matter lesions with axonal damage, blood-brain barrier disruption as shown by magnetic resonance imaging and CSF, and neuropsychological evidence of executive dysfunction. We have used these features to create a Binswanger Disease Scale and a probability of SIVD-BD, using a machine-learning algorithm. The patients discussed in this review are derived from published studies. Biomarkers not only aid in early diagnosis before the disease process has progressed too far for treatment, but also can indicate response to treatment. Refining the use of biomarkers will allow dementia treatment to enter the era of precision medicine. This article is part of the Special Issue "Vascular Dementia".

Vascular tight junction disruption and angiogenesis in spontaneously hypertensive rat with neuroinflammatory white matter injury

Vascular cognitive impairment is a major cause of dementia caused by chronic hypoxia, producing progressive damage to white matter (WM) secondary to blood-brain barrier (BBB) opening and vascular dysfunction. Tight junction proteins (TJPs), which maintain BBB integrity, are lost in acute ischemia. Although angiogenesis is critical for neurovascular remodeling, less is known about its role in chronic hypoxia. To study the impact of TJP degradation and angiogenesis during pathological progression of WM damage, we used the spontaneously hypertensive/stroke prone rats with unilateral carotid artery occlusion and Japanese permissive diet to model WM damage. MRI and IgG immunostaining showed regions with BBB damage, which corresponded with decreased endothelial TJPs, claudin-5, occludin, and ZO-1. Affected WM had increased expression of angiogenic factors, Ki67, NG2, VEGF-A, and MMP-3 in vascular endothelial cells and pericytes. To facilitate the study of angiogenesis, we treated rats with minocycline to block BBB disruption, reduce WM lesion size, and extend survival. Minocycline-treated rats showed increased VEGF-A protein, TJP formation, and oligodendrocyte proliferation. We propose that chronic hypoxia disrupts TJPs, increasing vascular permeability, and initiating angiogenesis in WM. Minocycline facilitated WM repair by reducing BBB damage and enhancing expression of TJPs and angiogenesis, ultimately preserving oligodendrocytes.

MRI measurements of Blood-Brain Barrier function in dementia: A review of recent studies

Blood-brain barrier (BBB) separates the systemic circulation and the brain, regulating transport of most molecules to protect the brain microenvironment. Multiple structural and functional components preserve the integrity of the BBB. Several imaging modalities are available to study disruption of the BBB. However, the subtle changes in BBB leakage that occurs in vascular cognitive impairment and Alzheimer's disease have been less well studied. Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) is the most widely adopted non-invasive imaging technique for evaluating BBB breakdown. It is used as a significant marker for a wide variety of diseases with large permeability leaks, such as brain tumors and multiple sclerosis, to more subtle disruption in chronic vascular disease and dementia. DCE-MRI analysis of BBB includes both model-free parameters and quantitative parameters using pharmacokinetic modelling. We review MRI studies of BBB breakdown in dementia. The challenges in measuring subtle BBB changes and the state of the art techniques are initially examined. Subsequently, a systematic review comparing methodologies from recent in-vivo MRI studies is presented. Various factors related to subtle BBB permeability measurement such as DCE-MRI acquisition parameters, arterial input assessment, T₁ mapping and data analysis methods are reviewed with the focus on finding the optimal technique. Finally, the reported BBB permeability values in dementia are compared across different studies and across various brain regions. We conclude that reliable measurement of low-level BBB permeability across sites remains a difficult problem and a standardization of the methodology for both data acquisition and quantitative analysis is required. This article is part of the Special Issue entitled 'Cerebral Ischemia'.

Translational models for vascular cognitive impairment: a review including larger species

BACKGROUND

Disease models are useful for prospective studies of pathology, identification of molecular and cellular mechanisms, pre-clinical testing of interventions, and validation of clinical biomarkers. Here, we review animal models relevant to vascular cognitive impairment (VCI). A synopsis of each model was initially presented by expert practitioners. Synopses were refined by the authors, and subsequently by the scientific committee of a recent conference (International Conference on Vascular Dementia 2015). Only peer-reviewed sources were cited.

METHODS

We included models that mimic VCI-related brain lesions (white matter hypoperfusion injury, focal ischaemia, cerebral amyloid angiopathy) or reproduce VCI risk factors (old age, hypertension, hyperhomocysteinemia, high-salt/high-fat diet) or reproduce genetic causes of VCI (CADASIL-causing Notch3 mutations).

CONCLUSIONS

We concluded that (1) translational models may reflect a VCI-relevant pathological process, while not fully replicating a human disease spectrum; (2) rodent models of VCI are limited by paucity of white matter; and (3) further translational models, and improved cognitive testing instruments, are required.

Neuroimaging in vascular cognitive impairment: a state-of-the-art review

Imaging is critical in the diagnosis and treatment of dementia, particularly in vascular cognitive impairment, due to the visualization of ischemic and hemorrhagic injury of gray and white matter. Magnetic resonance imaging (MRI) and positron emission tomography (PET) provide structural and functional information. Clinical MRI is both generally available and versatile - T2-weighted images show infarcts, FLAIR shows white matter changes and lacunar infarcts, and susceptibility-weighted images reveal microbleeds. Diffusion MRI adds another dimension by showing graded damage to white matter, making it more sensitive to white matter injury than FLAIR. Regions of neuroinflammatory disruption of the blood-brain barrier with increased permeability can be quantified and visualized with dynamic contrast-enhanced MRI. PET shows metabolism of glucose and accumulation of amyloid and tau, which is useful in showing abnormal metabolism in Alzheimer's disease. Combining MRI and PET allows identification of patients with mixed dementia, with MRI showing white matter injury and PET demonstrating regional impairment of glucose metabolism and deposition of amyloid. Excellent anatomical detail can be observed with 7.0-Tesla MRI. Imaging is the optimal method to follow the effect of treatments since changes in MRI scans are seen prior to those in cognition. This review describes the role of various imaging modalities in the diagnosis and treatment of vascular cognitive impairment.

Transient increase of fractional anisotropy in reversible vasogenic edema

Brain vasogenic edema, involving disruption of the blood-brain barrier, is a common pathological condition in several neurological diseases, with a heterogeneous prognosis. It is sometimes reversible, as in posterior reversible encephalopathy syndrome, but often irreversible and our current clinical tools are insufficient to reveal its reversibility. Here, we show that increased fractional anisotropy in magnetic resonance imaging is associated with the reversibility of vasogenic edema. Spontaneously, hypertensive rats-stroke prone demonstrated posterior reversible encephalopathy syndrome-like acute encephalopathy in response to high-dose cyclosporine A treatment; the deteriorating neurological symptoms and worsening scores in behavioral tests, which were seen in acute phase, dissappered after recovery by cessation of cyclosporine A. In the acute phase of encephalopathy, the fractional anisotropy and apparent diffusion coefficient increased in areas with IgG leakage. This increase of fractional anisotropy occurred in the absence of demyelination: fluid leakage into the myelinated space increased the axial, but not the radial, diffusivity, resulting in the increased fractional anisotropy. This increased fractional anisotropy returned to pre-encephalopathy values in the recovery phase. Our results highlight the importance of the fractional anisotropy increase as a marker for the reversibility of brain edema, which can delineate the brain areas for which recovery is possible.

Rodent Models of Vascular Cognitive Impairment

Vascular cognitive impairment dementia (VCID), which is an increasingly important cause of dementia in the elderly, lacks effective treatments. Many different types of vascular disease are included under the diagnosis of VCID, including large vessel disease with multiple strokes and small vessel disease with lacunar infarcts and white matter disease. Animal models have been developed to study the multiple forms of VCID. Because of its progressive course, small vessel disease (SVD) is thought to be the optimal form of VCID for treatment. One theory is that the pathophysiology involves hypoxic hypoperfusion resulting in injury to the white matter and neuronal death. Bilateral occlusion of the common carotid arteries (BCAO) in a normotensive rat, which reduces cerebral blood flow, induces hypoxia with white matter damage; this model has been used to test drugs to block the injury. Another model is the spontaneously hypertensive/stroke prone rat (SHR/SP). Hypertension leads to small vessel disease resulting in progressive damage to the white matter, cortex, and hippocampus. Bilateral carotid artery stenosis (BCAS) with coils or ameroid constrictors produces a slower development of changes than BCAO, avoiding the acute ischemia. A few studies have been done with the two-clip, two-vessel occlusion renal model for induction of hypertension. There are benefits and drawbacks to each of these models with the model selected depending on the type of vascular damage that is to be studied. This review describes the most commonly used models, and the drugs that have been used to reduce the damage.

Impaired renal function is associated with brain atrophy and poststroke cognitive decline

OBJECTIVE

To evaluate the interrelationship among impaired renal function, brain pathology on imaging, and cognitive decline in a longitudinal poststroke cohort.

METHODS

The Tel Aviv Brain Acute Stroke Cohort study is a prospective cohort of mild-moderate ischemic stroke/TIA survivors without dementia who underwent a 3T MRI and were cognitively assessed at admission and for 24 months following stroke. Renal function was evaluated at admission by creatinine clearance (CCl) estimation. The volumes of ischemic lesions and preexisting white matter hyperintensities (WMH), brain atrophy, and microstructural changes of the normal-appearing white matter tissue were measured using previously validated methods.

RESULTS

Baseline data were available for 431 participants. Participants with a CCl <60 mL/min at baseline performed significantly worse in all cognitive tests over time (p = 0.001) than those with a CCl ≥60 mL/min and had larger WMH volume and cortical atrophy and smaller hippocampal volume (all p < 0.001). After 2 years, 15.5% of the participants were diagnosed with cognitive impairment. Multiple logistic regression analysis, controlling for traditional risk factors, suggested CCl <60 mL/min at baseline as a significant predictor for the development of cognitive impairment 2 years after the index stroke (odds ratio 2.01 [95% confidence interval 1.03-3.92], p = 0.041).

CONCLUSIONS

Impaired renal function is associated with increased WMH volume and cortical atrophy, known biomarkers of the aging brain, and is a predictor for cognitive decline 2 years after stroke/TIA. Decreased renal function may be associated with cerebral small vessel disease underlying poststroke cognitive decline, suggesting a new target for early intervention.

Analysis of pharmacokinetics of Gd-DTPA for dynamic contrast-enhanced magnetic resonance imaging

The pharmacokinetics (PK) of the contrast agent Gd-DTPA administered intravenously (i.v.) for contrast-enhanced MR imaging (DCE-MRI) is an important factor for quantitative data acquisition. We studied the effect of various initial bolus doses on the PK of Gd-DTPA and analyzed population PK of a lower dose for intra-subject variations in DCE-MRI. First, fifteen subjects (23-85years, M/F) were randomly divided into four groups for DCE-MRI with different Gd-DTPA dose: group-I, 0.1mmol/kg, n=4; group-II, 0.05mmol/kg, n=4; group-III, 0.025mmol/kg, n=4; and group-IV, 0.0125mmol/kg, n=3. Sequential fast T1 mapping sequence, after a bolus i.v. Gd-DTPA administered, and a linear T1-[Gd-DTPA] relationship were used to estimate the PK of Gd-DTPA. Secondly, MR-acquired PKs of Gd-DTPA from 58 subjects (28-80years, M/F) were collected retrospectively, from an ongoing study of the brain using DCE-MRI with Gd-DTPA at 0.025mmol/kg, to statistically analyze population PK of Gd-DTPA. We found that the PK of Gd-DTPA (i.v. 0.025mmol/kg) had a half-life of 37.3±6.6min, and was a better fit into a linear T1-[Gd-DTPA] relationship than higher doses (up to 0.1mmol/kg). The area under the curve (AUC) for 0.025mmol/kg was 3.37±0.46, which was a quarter of AUC of 0.1mmol/kg. In population analysis, a dose of 0.025mmol/kg of Gd-DTPA provided less than 5% subject-dependent variation in the PK of Gd-DTPA. Administration of 0.025mmol/kg Gd-DTPA enabled us to estimate [Gd-DTPA] from T1 by using a linear relationship that has a lower estimation error compared to a non-linear relationship. DCE-MRI with a quarter dose of Gd-DTPA is more sensitive to detect changes in [Gd-DTPA].

Matrix Metalloproteinase-Mediated Neuroinflammation in Vascular Cognitive Impairment of the Binswanger Type

Vascular cognitive impairment (VCI) is a heterogeneous group of diseases linked together by cerebrovascular disease. Treatment of VCI has been hindered by the lack of a coherent pathophysiological process that could provide molecular targets. Of the several forms of VCI, the small vessel disease form is both the most prevalent and generally has a progressive course. Binswanger's disease (BD) is the small vessel form of VCI that involves extensive injury to the deep white matter. Growing evidence suggests that there is disruption of the blood-brain barrier (BBB) secondary to an inflammatory state. Matrix metalloproteinases (MMPs) are increased in the brain and CSF of patients with BD, and have been shown to disrupt the BBB in animal studies, suggesting that they may be biomarkers and therapeutic targets. Multimodal biomarkers derived from clinical, neuropsychological, imaging, and biochemical data can be used to narrow the VCI population to the progressive inflammatory form that will be optimal for treatment trials. This review describes the role of the MMPs in pathophysiology and their use as biomarkers.

Abstract TMP110: Minocycline Reduces Hypoxia-mediated BBB Disruption by Protecting TJP Degradation and Promoting Angiogenesis in SHR/SP With Chronic White-matter Injury

Introduction: Our previous study indicated that blood-brain barrier (BBB) disruption occurred secondary to hypoxia-induced and MMP-mediated neuroinflammatory white matter (WM) damage in spontaneously hypertensive/stroke prone rats (SHR/SP). Tight junction proteins (TJPs) maintain the normal BBB functions. Here, we investigated the effects of hypoxia on TJP degradation and hypoxia-induced angiogenesis, and tested the effect of long-term minocycline treatment on the BBB integrity and repair.

Methods: Male SHR/SPs at 12W (weeks) old were subjected to unilateral carotid artery occlusion (UCAO) and fed a Japanese permissive diet (JPD) for 4W. For the treatment study, the SHR/SP/UCAO/JPD were given minocycline (50 mg/kg in DMSO, i.p.) and the vehicle rats received DMSO from 12W to 20W of life.

Results: Sham-operated SHR/SP with normal chow had abnormal TJPs in blood vessels (BVs) at 16W compared to Wistar; they showed a slight increase of BBB permeability and NG2-positive microglia in WM. In the UCAO/JDP group, by 4W, multimodal MRI (T2, ADC, FA, and ASL) showed that WM damage of varying degree reflected the extent of injury corresponding to variable BBB leakage by dynamic contrast-enhanced MRI and IgG staining. TJP levels (claudin-5, occludin, and ZO-1) in WM were significantly decreased. Angiogenesis in WM was detected with increased expression of Ki67 and NG2 in vascular endothelial cells and/or pericytes. UCAO/JPD typically causes the death of SHR-SP/JPD/UCAO rats after 4W. However, minocycline treatment extended survival to 9W after UCAO/JPD and significantly reduced lesion size and vascular damage. TJPs, VEGF-A, and GST-π (mature oligodendrocytes) were increased by minocycline at 8W compared to sham and vehicle. Minocycline also increased the expression of factors involved in angiogenesis and WM repair (Ki67, NG2, MMP-2, MMP-3) in vascular endothelial cells, pericytes, astrocytes, and oligodendrocytes compared to controls.

Conclusions: Our results support the hypothesis that damage to the BVs by chronic hypertension and UCAO/JPD produces TJP degradation and increases BBB permeability. Minocycline treatment significantly protects WM from damage by preventing BBB disruption and enhances TJP formation and angiogenesis.

Abstract 44: Enlarged Perivascular Spaces Correlate With CSF Biomarkers for Abnormal Blood-brain Barrier Permeability and Neuroinflammation in Patients With Vascular Cognitive Impairment

Background: Enlarged perivascular spaces (PVS) in the brain are common but their etiology and specificity are unclear. Multiple studies have shown a correlation between enlarged PVS and white matter hyperintensities (WMHs), but the relationship with vascular disease is uncertain. We used albumin CSF to blood ratio as a method to measure permeability of the blood-brain barrier (BBB) in patients with vascular cognitive impairment (VCI). It is possible that the enlarged PVS are associated with an increase in BBB permeability, which could interfere with perivascular fluid flow. Therefore, we hypothesized that enlarged PVS correlate with CSF markers of increased BBB permeability and neuroinflammation.

Methods: We prospectively recruited 107 VCI patients with white matter disease. At entry, they had brain MRIs with standardized ranking for enlarged PVS. Sixty-one had lumbar puncture to obtain CSF for analysis of albumin ratio, matrix metalloproteinases-2 (MMP-2) index, and amyloid-beta1-42 (Abeta42). The data was analyzed statistically with nonparametric correlation methods.

Results: Enlarged PVS had a positive correlation with CSF albumin ratio, which is a biomarker for increased BBB permeability ( p <0.01), and a negative correlation with the neuroinflammatory biomarker, MMP2 index ( p <0.02), and with Abeta42 ( p <0.02), which is cleared by the PVS.

Conclusion: Our results suggest an association between PVS, MMP-mediated increased BBB permeability, and clearance of Abeta42. The role of perivascular fluid movement and its relationship with CSF biomarkers will require further investigation.

Validation of biomarkers in subcortical ischaemic vascular disease of the Binswanger type: approach to targeted treatment trials

OBJECTIVES

Vascular cognitive impairment (VCI) is a heterogeneous group of cerebrovascular diseases secondary to large and small vessel disease. We hypothesised that biomarkers obtained early in the disease could identify a homogeneous subpopulation with small vessel disease.

METHODS

We obtained disease markers in 62 patients with VCI that included neurological findings, neuropsychological tests, multimodal MR and cerebrospinal fluid measurements of albumin ratio, matrix metalloproteinases (MMPs), amyloid-β1-42 and phosphorylated-τ181. Proton MR spectroscopic imaging showed ischaemic white matter and permeability of the blood-brain barrier (BBB) was measured with dynamic contrast-enhanced MRI. We constructed a 10-point Binswanger disease score (BDS) with subjective and objective disease markers. In addition, an objective set of biomarkers was used for an exploratory factor analysis (EFA) to select patients with BD. Patients were followed for an average of 2 years to obtain clinical consensus diagnoses.

RESULTS

An initial BDS of 6 or greater was significantly correlated with a final diagnosis of BD (p<0.05; area under the curve (AUC)=0.79). EFA reduced nine objective biomarkers to four factors. The most predictive of BD was the factor containing the inflammatory biomarkers of increased BBB permeability, elevated albumin index and reduced MMP-2 index (factor 2; AUC=0.78). Both measures independently predicted a diagnosis of BD, and combining them improved the diagnostic accuracy.

CONCLUSIONS

Biomarkers predicted the diagnosis of the BD type of subcortical ischaemic vascular disease. Using pathophysiological biomarkers to select homogeneous groups of patients needs to be tested in targeted treatment trials.

Long-Term Blood-Brain Barrier Permeability Changes in Binswanger Disease

BACKGROUND AND PURPOSE

The blood-brain barrier (BBB) is disrupted in small vessel disease patients with lacunes and white matter hyperintensities (WMHs). The relationship of WMHs and regional BBB permeability changes has not been studied. We hypothesized that BBB disruption occurs in normal appearing WM and regions near the WMHs. To test the hypothesis, we repeated BBB permeability measurements in patients with extensive WMHs related to Binswanger disease.

METHODS

We selected a subset of 22 Binswanger disease subjects from a well-characterized larger prospective vascular cognitive impairment cohort. We used 16 age-matched controls for comparison. The abnormal WM permeability (WMP) was measured twice for several years using dynamic contrast-enhanced magnetic resonance imaging. WMP maps were constructed from voxels above a predetermined threshold. Scans from first and second visits were coregistered. WM was divided into 3 regions: normal appearing WM, WMH ring, and WMH core. The ring was defined as 2 mm on each side of the WMH border. WMP was calculated in each of the 3 specific regions. We used paired t test, ANOVA, and Fisher exact test to compare individual changes.

RESULTS

WMP was significantly higher in subjects than in controls (P<0.001). There was no correlation between WMH load and WMP. High permeability regions had minimal overlap between first and second scans. Nine percent of WMP was within the WMHs, 49% within the normal appearing WM, and 52% within the WMH ring (P<0.001; ANOVA).

CONCLUSIONS

Increased BBB permeability in normal appearing WM and close to the WMH borders supports a relationship between BBB disruption and the development of WMHs.

Matrix metalloproteinases as therapeutic targets for stroke

Matrix metalloproteinases (MMPs) are important in injury and recovery in ischemic injury. They are proteolytic enzymes that degrade all components of the extracellular matrix (ECM). They are secreted in a latent form, protecting the cell from damage, but once activated induce injury prior to rapid inactivation by four tissue inhibitors to metalloproteinases (TIMPs). Normally the constitutive enzymes, MMP-2 and membrane type MMP (MMP-14), are activated in a spatially specific manner and act close to the site of activation, while the inducible enzymes, MMP-3 and MMP-9, become active through the action of free radicals and other enzymes during neuroinflammation. Because of the complex nature of the interactions with tissues during development, injury and repair, the MMPs have multiple roles, participating in the injury process in the early stages and contributing to recovery during the later stages. This dual role complicates the planning of treatment strategies. This article is part of a Special Issue entitled SI: Cell Interactions In Stroke.

Abstract W P385: Hypertension-Induced Hypoxia Leads to Neurodegeneration in a Novel Model of Accelerated Cerebrovascular Disease

Hypertension is a major risk factor contributing to cerebrovascular diseases such as stroke and vascular cognitive impairment (VCI). Elevated blood pressure leads to cerebral small vessel disease, resulting neuronal cell death and cognitive dysfunction. We developed a unique animal model of clinical VCI in the spontaneously hypertensive stroke prone (SHR-SP) rat, characterized by significant white matter disease, neuroinflammation and behavioral deficits induced by a Japanese Permissive Diet (JPD) and unilateral carotid artery occlusion (UCAO). We hypothesized that the SHR-SP rat has neuropathological changes in the cortex and hippocampus due to effects of hypertension on neurodegeneration. To test the hypothesis, we performed permanent right side UCAO (hypoxia) at 12 weeks (12W) of age in male SHR-SP rats (n=5). Following surgery, rats were placed on a JPD and received 1% NaCl in drinking water (hypertension). Control rats were fed a normal diet and underwent right carotid artery isolation (n=4). A preliminary time course of NeuN and Cresyl Violet staining, from hypoxia onset (12W) to sacrifice (16W), showed decreased neuronal survival and elevated neuroinflammatory response (astro- and micro-gliosis by GFAP and Iba1 staining, respectively) in the experimental group as compared to controls. Microbleeds and endothelial cell damage were observed by Hematoxylin and Eosin histology. Immunohistochemistry showed an up-regulation of hypoxia inducible factor-1α (HIF-1α), implicating a hypoxia-mediated mechanism in neurodegeneration. We observed disruption of the blood brain barrier beginning at 13W, with progressive changes by 16W. MRI-T2 imaging showed significantly larger infarct sizes on the left as compared to the right side hippocampus of experimental rats versus controls (1409656.67±262032 and 1174952.89±145886 (mean±SE), respectively; p<0.009). Our results indicate that chronic hypertension may effect neurodegenerative changes, not only in the white matter, but also in the cortex and hippocampus. Supported by NIH/NINDS RO1 NS045847-07A1.

Binswanger's disease: toward a diagnosis agreement and therapeutic approach

Binswanger's disease (BD) is a progressive form of cerebral small vessel disease affecting the white matter and other subcortical structures. Clinical and imaging characteristics, neuropsychological profile and cerebrospinal fluid analysis aid in making the diagnosis. BD shares features of other small vessel diseases and degenerative neurological conditions, which makes diagnosis difficult. However, with recent developments in MRI methods and serum/cerebrospinal fluid biomarkers, we have gained a greater understanding of the complex pathophysiology of the disease that will guide us to a more certain diagnosis. There is growing evidence that the white matter injury in BD is related to endothelial dysfunction with a secondary inflammatory response leading to breakdown of the neurovascular unit. This review summarizes current and future research directions, including pathophysiological mechanisms and potential therapeutic approaches.

Identification of isoxsuprine hydrochloride as a neuroprotectant in ischemic stroke through cell-based high-throughput screening

Stroke is a leading cause of death and disability and treatment options are limited. A promising approach to accelerate the development of new therapeutics is the use of high-throughput screening of chemical libraries. Using a cell-based high-throughput oxygen-glucose deprivation (OGD) model, we evaluated 1,200 small molecules for repurposed application in stroke therapy. Isoxsuprine hydrochloride was identified as a potent neuroprotective compound in primary neurons exposed to OGD. Isoxsuprine, a β₂-adrenergic agonist and NR2B subtype-selective N-methyl-D-aspartate (NMDA) receptor antagonist, demonstrated no loss of efficacy when administered up to an hour after reoxygenation in an in vitro stroke model. In an animal model of transient focal ischemia, isoxsuprine significantly reduced infarct volume compared to vehicle (137±18 mm³ versus 279±25 mm³, p<0.001). Isoxsuprine, a peripheral vasodilator, was FDA approved for the treatment of cerebrovascular insufficiency and peripheral vascular disease. Our demonstration of the significant and novel neuroprotective action of isoxsuprine hydrochloride in an in vivo stroke model and its history of human use suggest that isoxsuprine may be an ideal candidate for further investigation as a potential stroke therapeutic.

Abstract W MP42: Early Treatment With Minocycline Promotes Neurovascular Remodeling of Tight Junctions Facilitating Recovery After Stroke in Rat Brain

Minocycline (Mino) reduces reperfusion injury and inflammation after stroke in animals and humans, but the late effects on remodeling of the neurovascular unit are less well studied. Previously, we showed that tight junction proteins (TJPs) disappeared from microvessels after reperfusion injury, reappearing in newly formed vessels in peri-infarct regions (peri-I) at 3 weeks, and that MMPs are involved in BBB restoration during recovery. Prior studies of Mino investigated short-term neuroprotective effects with or without tPA. We hypothesized that early treatment with Mino would improve neurovascular remodeling during recovery. To test the hypothesis, we monitored the time course of neurovascular remodeling after spontaneous and Mino-induced stroke recovery. Adult spontaneously hypertensive rats had a 90 min transient MCAO with reperfusion. At the onset of reperfusion they received a single dose of Mino (3 mg/kg, i.v.) or vehicle. They were studied at multiple times up to 4 weeks with MRI, immunohistochemistry, and biochemistry. A single dose of Mino significantly reduced the infarct size and tissue loss in the ischemic hemispheres compared to vehicle-treated rats from 2 to 4 weeks as measured with anatomical T2 MRI and ADC. FA measured at 4 weeks showed improved white matter recovery. ASL showed that Mino improved cerebral blood flow in peri-I by 7 days after reperfusion. BBB permeability in peri-I was reduced with Mino at 4 weeks using dynamic contrast-enhanced MRI. By 4 weeks, Mino induced higher levels of TJPs (occludin, ZO-1, and claudin-5), and MMP-3. We found that active microglia/macrophages, surrounding and within the peri-I, expressed both pro-inflammatory factors (TNF-α and IL-1β) and anti-inflammatory factors (TGF-β and IL-10) at 4 weeks. Western blot analysis showed that treatment with Mino significantly reduced levels of TNF-α and IL-1β, and increased levels of TGF-β and IL-10. Our results suggest that the early treatment with Mino significantly promotes later neurovascular remodeling during stroke recovery by: 1) reducing brain tissue loss; 2) enhancing TJP formation in newly formed vessels; and 3) accelerating functional alteration of microglia activation from pro-inflammatory stage to anti-inflammatory stage.

Dynamic contrast-enhanced MRI evaluation of cerebral cavernous malformations

The aim of this study is to quantitatively evaluate the behavior of CNS cavernous malformations (CCMs) using a dynamic contrast-enhanced MRI (DCEMRI) technique sensitive for slow transfer rates of gadolinium. The prospective study was approved by the institutional review board and was HIPPA compliant. Written informed consent was obtained from 14 subjects with familial CCMs (4 men and 10 women, ages 22-76 years, mean 48.1 years). Following routine anatomic MRI of the brain, DCEMRI was performed for six slices, using T1 mapping with partial inversion recovery (TAPIR) to calculate T1 values, following administration of 0.025 mmol/kg gadolinium DTPA. The transfer rate (Ki) was calculated using the Patlak model, and Ki within CCMs was compared to normal-appearing white matter as well as to 17 normal control subjects previously studied. All subjects had typical MRI appearance of CCMs. Thirty-nine CCMs were studied using DCEMRI. Ki was low or normal in 12 lesions and elevated from 1.4 to 12 times higher than background in the remaining 27 lesions. Ki ranged from 2.1E-6 to 9.63E-4 min(-1), mean 3.55E-4. Normal-appearing white matter in the CCM patients had a mean Ki of 1.57E-4, not statistically different from mean WM Ki of 1.47E-4 in controls. TAPIR-based DCEMRI technique permits quantifiable assessment of CCMs in vivo and reveals considerable differences not seen with conventional MRI. Potential applications include correlation with biologic behavior such as lesion growth or hemorrage, and measurement of drug effects.