Recent Translational Research Models of Intracranial Atherosclerotic Disease.

Intracranial atherosclerotic disease (ICAD) is a leading cause of ischemic stroke worldwide. However, research on the pathophysiology of ICAD is scarce due to the relative inaccessibility of histology samples and the lack of comprehensive experimental models. As a result, much of the current understanding of ICAD relies on research on extracranial atherosclerosis. This approach is problematic as intracranial and extracranial arteries are anatomically, structurally, physiologically, and metabolically distinct, indicating that intracranial and extracranial atherosclerosis likely develop through different biologic pathways. The current standard of care for ICAD treatment relies predominantly on therapeutics developed to treat extracranial atherosclerosis and is insufficient given the alarmingly high risk of stroke. To provide a definitive treatment for the disease, a deeper understanding of the pathophysiology underlying ICAD is specifically required. True mechanistic understanding of disease pathogenesis is only possible using robust experimental models. In this review, we aim to identify the advantages and limitations of the existing in vivo and in vitro models of ICAD and basic atherosclerotic processes, which may be used to inform better models of ICAD in the future and drive new therapeutic strategies to reduce stroke risk.

Association of Incident Stroke Risk With an IL-18-Centered Inflammatory Network Biomarker Composite.

BACKGROUND: A coordinated network of circulating inflammatory molecules centered on the pleotropic pro-atherogenic cytokine interleukin-18 (IL-18) is linked to cerebral small vessel disease. We sought to validate the association of this inflammatory biomarker network with incident stroke risk, cognitive impairment, and imaging metrics in a sample of the Framingham Offspring Cohort. METHODS: Using available baseline measurements of serum levels of IL-18, GDF (growth and differentiation factor)-15, soluble form of receptor for advanced glycation end products, myeloperoxidase, and MCP-1 (monocyte chemoattractant protein-1) from Exam 7 of the Framingham Offspring Cohort (1998-2001), we constructed a population-normalized, equally weighted log-transformed mean Z-score value representing the average level of each serum analyte to create an inflammatory composite score (ICS5). Multivariable regression models were used to determine the association of ICS5 with incident stroke, brain magnetic resonance imaging features, and cognitive testing performance. RESULTS: We found a significant association between ICS5 score and increased risk for incident all-cause stroke (hazard ratio, 1.48 [95% CI, 1.05-2.08]; P=0.024) and ischemic stroke (hazard ratio, 1.51 [95% CI, 1.03-2.21]; P=0.033) in the Exam 7 cohort of 2201 subjects (mean age 62±9 years; 54% female) aged 45+ years with an all-cause incident stroke rate of 6.1% (135/2201) and ischemic stroke rate of 4.9% (108/2201). ICS5 and its component serum markers are all associated with the Framingham Stroke Risk Profile score (ß±SE, 0.19±0.02; P<0.0001). In addition, we found a significant inverse association of ICS5 with a global cognitive score, derived from a principal components analysis of the neuropsychological battery used in the Framingham cohort (-0.08±0.03; P=0.019). No association of ICS5 with magnetic resonance imaging metrics of cerebral small vessel disease was observed. CONCLUSIONS: Circulating serum levels of inflammatory biomarkers centered on IL-18 are associated with an increased risk of stroke and cognitive impairment in the Framingham Offspring Cohort. Linking specific inflammatory pathways to cerebral small vessel disease may enhance individualized quantitative risk assessment for future stroke and vascular cognitive impairment.

Post-Stroke Cognitive Impairment and Dementia.

Poststroke cognitive impairment and dementia (PSCID) is a major source of morbidity and mortality after stroke worldwide. PSCID occurs as a consequence of ischemic stroke, intracerebral hemorrhage, or subarachnoid hemorrhage. Cognitive impairment and dementia manifesting after a clinical stroke is categorized as vascular even in people with comorbid neurodegenerative pathology, which is common in elderly individuals and can contribute to the clinical expression of PSCID. Manifestations of cerebral small vessel disease, such as covert brain infarcts, white matter lesions, microbleeds, and cortical microinfarcts, are also common in patients with stroke and likewise contribute to cognitive outcomes. Although studies of PSCID historically varied in the approach to timing and methods of diagnosis, most of them demonstrate that older age, lower educational status, socioeconomic disparities, premorbid cognitive or functional decline, life-course exposure to vascular risk factors, and a history of prior stroke increase risk of PSCID. Stroke characteristics, in particular stroke severity, lesion volume, lesion location, multiplicity and recurrence, also influence PSCID risk. Understanding the complex interaction between an acute stroke event and preexisting brain pathology remains a priority and will be critical for developing strategies for personalized prediction, prevention, targeted interventions, and rehabilitation. Current challenges in the field relate to a lack of harmonization of definition and classification of PSCID, timing of diagnosis, approaches to neurocognitive assessment, and duration of follow-up after stroke. However, evolving knowledge on pathophysiology, neuroimaging, and biomarkers offers potential for clinical applications and may inform clinical trials. Preventing stroke and PSCID remains a cornerstone of any strategy to achieve optimal brain health. We summarize recent developments in the field and discuss future directions closing with a call for action to systematically include cognitive outcome assessment into any clinical studies of poststroke outcome.

miR-142-3p regulates cortical oligodendrocyte gene co-expression networks associated with tauopathy.

Oligodendrocytes exist in a heterogenous state and are implicated in multiple neuropsychiatric diseases including dementia. Cortical oligodendrocytes are a glial population uniquely positioned to play a key role in neurodegeneration by synchronizing circuit connectivity but molecular pathways specific to this role are lacking. We utilized oligodendrocyte-specific translating ribosome affinity purification and RNA-seq (TRAP-seq) to transcriptionally profile adult mature oligodendrocytes from different regions of the central nervous system. Weighted gene co-expression network analysis reveals distinct region-specific gene networks. Two of these mature myelinating oligodendrocyte gene networks uniquely define cortical oligodendrocytes and differentially regulate cortical myelination (M8) and synaptic signaling (M4). These two cortical oligodendrocyte gene networks are enriched for genes associated with dementia including MAPT and include multiple gene targets of the regulatory microRNA, miR-142-3p. Using a combination of TRAP-qPCR, miR-142-3p overexpression in vitro, and miR-142-null mice, we show that miR-142-3p negatively regulates cortical myelination. In rTg4510 tau-overexpressing mice, cortical myelination is compromised, and tau-mediated neurodegeneration is associated with gene co-expression networks that recapitulate both the M8 and M4 cortical oligodendrocyte gene networks identified from normal cortex. We further demonstrate overlapping gene networks in mature oligodendrocytes present in normal cortex, rTg4510 and miR-142-null mice, and existing datasets from human tauopathies to provide evidence for a critical role of miR-142-3p-regulated cortical myelination and oligodendrocyte-mediated synaptic signaling in neurodegeneration.

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.

Inflammation and the Link to Vascular Brain Health: Timing Is Brain.

Inflammation and its myriad pathways are now recognized to play both causal and consequential roles in vascular brain health. From acting as a trigger for vascular brain injury, as evidenced by the COVID-19 pandemic, to steadily increasing the risk for chronic cerebrovascular disease, distinct inflammatory cascades play differential roles in varying states of cerebrovascular injury. New evidence is regularly emerging that characterizes the role of specific inflammatory pathways in these varying states including those at risk for stroke and chronic cerebrovascular injury as well as during the acute, subacute, and repair phases of stroke. Here, we aim to highlight recent basic science and clinical evidence for many distinct inflammatory cascades active in these varying states of cerebrovascular injury. The role of cerebrovascular infections, spotlighted by the severe acute respiratory syndrome coronavirus 2 pandemic, and its association with increased stroke risk is also reviewed. Rather than converging on a shared mechanism, these emerging studies implicate varied and distinct inflammatory processes in vascular brain injury and repair. Recognition of the phasic nature of inflammatory cascades on varying states of cerebrovascular disease is likely essential to the development and implementation of an anti-inflammatory strategy in the prevention, treatment, and repair of vascular brain injury. Although advances in revascularization have taught us that time is brain, targeting inflammation for the treatment of cerebrovascular disease will undoubtedly show us that timing is brain.

Plasma amyloid beta, neurofilament light chain, and total tau in the Systolic Blood Pressure Intervention Trial (SPRINT).

INTRODUCTION: Lowering blood pressure (BP) reduces the risk for cognitive impairment and the progression of cerebral white matter lesions. It is unclear whether hypertension control also influences plasma biomarkers related to Alzheimer's disease and non-disease-specific neurodegeneration. METHODS: We examined the effect of intensive (< 120 mm Hg) versus standard (< 140 mm Hg) BP control on longitudinal changes in plasma amyloid beta (Aß)40 and Aß42 , total tau, and neurofilament light chain (NfL) in a subgroup of participants from the Systolic Blood Pressure Intervention Trial (N = 517). RESULTS: Over 3.8 years, there were no significant between-group differences for Aß40, Aß42, Aß42 /Aß40, or total tau. Intensive treatment was associated with larger increases in NfL compared to standard treatment. Adjusting for kidney function, but not BP, attenuated the association between intensive treatment and NfL. DISCUSSION: Intensive BP treatment was associated with changes in NfL, which were correlated with changes in kidney function associated with intensive treatment. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01206062.

Flow-Mediated Susceptibility and Molecular Response of Cerebral Endothelia to SARS-CoV-2 Infection.

BACKGROUND AND PURPOSE: Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection is associated with an increased rate of cerebrovascular events including ischemic stroke and intracerebral hemorrhage. The mechanisms underlying cerebral endothelial susceptibility and response to SARS-CoV-2 are unknown yet critical to understanding the association of SARS-CoV-2 infection with cerebrovascular events. METHODS: Endothelial cells were isolated from human brain and analyzed by RNA sequencing. Human umbilical vein and human brain microvascular cells were used in both monolayer culture and endothelialized within a 3-dimensional printed vascular model of the middle cerebral artery. Gene expression levels were measured by quantitative polymerase chain reaction and direct RNA hybridization. Recombinant SARS-CoV-2 S protein and S protein-containing liposomes were used to measure endothelial binding by immunocytochemistry. RESULTS: ACE2 (angiotensin-converting enzyme-2) mRNA levels were low in human brain and monolayer endothelial cell culture. Within the 3-dimensional printed vascular model, ACE2 gene expression and protein levels were progressively increased by vessel size and flow rates. SARS-CoV-2 S protein-containing liposomes were detected in human umbilical vein endothelial cells and human brain microvascular endothelial cells in 3-dimensional middle cerebral artery models but not in monolayer culture consistent with flow dependency of ACE2 expression. Binding of SARS-CoV-2 S protein triggered 83 unique genes in human brain endothelial cells including upregulation of complement component C3. CONCLUSIONS: Brain endothelial cells are susceptible to direct SARS-CoV-2 infection through flow-dependent expression of ACE2. Viral S protein binding triggers a unique gene expression profile in brain endothelia that may explain the association of SARS-CoV-2 infection with cerebrovascular events.

MarkVCID cerebral small vessel consortium: I. Enrollment, clinical, fluid protocols.

The concept of vascular contributions to cognitive impairment and dementia (VCID) derives from more than two decades of research indicating that (1) most older individuals with cognitive impairment have post mortem evidence of multiple contributing pathologies and (2) along with the preeminent role of Alzheimer's disease (AD) pathology, cerebrovascular disease accounts for a substantial proportion of this contribution. Contributing cerebrovascular processes include both overt strokes caused by etiologies such as large vessel occlusion, cardioembolism, and embolic infarcts of unknown source, and frequently asymptomatic brain injuries caused by diseases of the small cerebral vessels. Cerebral small vessel diseases such as arteriolosclerosis and cerebral amyloid angiopathy, when present at moderate or greater pathologic severity, are independently associated with worse cognitive performance and greater likelihood of dementia, particularly in combination with AD and other neurodegenerative pathologies. Based on this evidence, the US National Alzheimer's Project Act explicitly authorized accelerated research in vascular and mixed dementia along with frontotemporal and Lewy body dementia and AD itself. Biomarker development has been consistently identified as a key step toward translating scientific advances in VCID into effective prevention and treatment strategies. Validated biomarkers can serve a range of purposes in trials of candidate interventions, including (1) identifying individuals at increased VCID risk, (2) diagnosing the presence of cerebral small vessel disease or specific small vessel pathologies, (3) stratifying study participants according to their prognosis for VCID progression or treatment response, (4) demonstrating an intervention's target engagement or pharmacodynamic mechanism of action, and (5) monitoring disease progression during treatment. Effective biomarkers allow academic and industry investigators to advance promising interventions at early stages of development and discard interventions with low success likelihood. The MarkVCID consortium was formed in 2016 with the goal of developing and validating fluid- and imaging-based biomarkers for the cerebral small vessel diseases associated with VCID. MarkVCID consists of seven project sites and a central coordinating center, working with the National Institute of Neurologic Diseases and Stroke and National Institute on Aging under cooperative agreements. Through an internal selection process, MarkVCID has identified a panel of 11 candidate biomarker "kits" (consisting of the biomarker measure and the clinical and cognitive data used to validate it) and established a range of harmonized procedures and protocols for participant enrollment, clinical and cognitive evaluation, collection and handling of fluid samples, acquisition of neuroimaging studies, and biomarker validation. The overarching goal of these protocols is to generate rigorous validating data that could be used by investigators throughout the research community in selecting and applying biomarkers to multi-site VCID trials. Key features of MarkVCID participant enrollment, clinical/cognitive testing, and fluid biomarker procedures are summarized here, with full details in the following text, tables, and supplemental material, and a description of the MarkVCID imaging biomarker procedures in a companion paper, "MarkVCID Cerebral small vessel consortium: II. Neuroimaging protocols." The procedures described here address a range of challenges in MarkVCID's design, notably: (1) acquiring all data under informed consent and enrollment procedures that allow unlimited sharing and open-ended analyses without compromising participant privacy rights; (2) acquiring the data in a sufficiently wide range of study participants to allow assessment of candidate biomarkers across the various patient groups who might ultimately be targeted in VCID clinical trials; (3) defining a common dataset of clinical and cognitive elements that contains all the key outcome markers and covariates for VCID studies and is realistically obtainable during a practical study visit; (4) instituting best fluid-handling practices for minimizing avoidable sources of variability; and (5) establishing rigorous procedures for testing the reliability of candidate fluid-based biomarkers across replicates, assay runs, sites, and time intervals (collectively defined as the biomarker's instrumental validity). Participant Enrollment Project sites enroll diverse study cohorts using site-specific inclusion and exclusion criteria so as to provide generalizable validation data across a range of cognitive statuses, risk factor profiles, small vessel disease severities, and racial/ethnic characteristics representative of the diverse patient groups that might be enrolled in a future VCID trial. MarkVCID project sites include both prospectively enrolling centers and centers providing extant data and samples from preexisting community- and population-based studies. With approval of local institutional review boards, all sites incorporate MarkVCID consensus language into their study documents and informed consent agreements. The consensus language asks prospectively enrolled participants to consent to unrestricted access to their data and samples for research analysis within and outside MarkVCID. The data are transferred and stored as a de-identified dataset as defined by the Health Insurance Portability and Accountability Act Privacy Rule. Similar human subject protection and informed consent language serve as the basis for MarkVCID Research Agreements that act as contracts and data/biospecimen sharing agreements across the consortium. Clinical and Cognitive Data Clinical and cognitive data are collected across prospectively enrolling project sites using common MarkVCID instruments. The clinical data elements are modified from study protocols already in use such as the Alzheimer's Disease Center program Uniform Data Set Version 3 (UDS3), with additional focus on VCID-related items such as prior stroke and cardiovascular disease, vascular risk factors, focal neurologic findings, and blood testing for vascular risk markers and kidney function including hemoglobin A1c, cholesterol subtypes, triglycerides, and creatinine. Cognitive assessments and rating instruments include the Clinical Dementia Rating Scale, Geriatric Depression Scale, and most of the UDS3 neuropsychological battery. The cognitive testing requires ≈60 to 90 minutes. Study staff at the prospectively recruiting sites undergo formalized training in all measures and review of their first three UDS3 administrations by the coordinating center. Collection and Handling of Fluid Samples Fluid sample types collected for MarkVCID biomarker kits are serum, ethylenediaminetetraacetic acid-plasma, platelet-poor plasma, and cerebrospinal fluid (CSF) with additional collection of packed cells to allow future DNA extraction and analyses. MarkVCID fluid guidelines to minimize variability include fasting morning fluid collections, rapid processing, standardized handling and storage, and avoidance of CSF contact with polystyrene. Instrumental Validation for Fluid-Based Biomarkers Instrumental validation of MarkVCID fluid-based biomarkers is operationally defined as determination of intra-plate and inter-plate repeatability, inter-site reproducibility, and test-retest repeatability. MarkVCID study participants both with and without advanced small vessel disease are selected for these determinations to assess instrumental validity across the full biomarker assay range. Intra- and inter-plate repeatability is determined by repeat assays of single split fluid samples performed at individual sites. Inter-site reproducibility is determined by assays of split samples distributed to multiple sites. Test-retest repeatability is determined by assay of three samples acquired from the same individual, collected at least 5 days apart over a 30-day period and assayed on a single plate. The MarkVCID protocols are designed to allow direct translation of the biomarker validation results to multicenter trials. They also provide a template for outside groups to perform analyses using identical methods and therefore allow direct comparison of results across studies and centers. All MarkVCID protocols are available to the biomedical community and intended to be shared. In addition to the instrumental validation procedures described here, each of the MarkVCID kits will undergo biological validation to determine whether the candidate biomarker measures important aspects of VCID such as cognitive function. Analytic methods and results of these validation studies for the 11 MarkVCID biomarker kits will be published separately. The results of this rigorous validation process will ultimately determine each kit's potential usefulness for multicenter interventional trials aimed at preventing or treating small vessel disease related VCID.

White Matter Stroke Induces a Unique Oligo-Astrocyte Niche That Inhibits Recovery.

Subcortical white matter stroke is a common stroke subtype. White matter stroke stimulates adjacent oligodendrocyte progenitor cells (OPCs) to divide and migrate to the lesion, but stroke OPCs have only a limited differentiation into mature oligodendrocytes. To understand the molecular systems that are active in OPC responses in white matter stroke, OPCs were virally labeled and laser-captured in the region of partial damage adjacent to the infarct in male mice. RNAseq indicates two distinct OPC transcriptomes associated with the proliferative and limited-regeneration phases of OPCs after stroke. Molecular pathways related to nuclear receptor activation, ECM turnover, and lipid biosynthesis are activated during proliferative OPC phases after stroke; inflammatory and growth factor signaling is activated in the later stage of limited OPC differentiation. Within ECM proteins, Matrilin-2 is induced early after stroke and then rapidly downregulated. Prediction of upstream regulators of the OPC stroke transcriptome identifies several candidate molecules, including Inhibin A-a negative regulator of Matrilin-2. Inhibin A is induced in reactive astrocytes after stroke, including in humans. In functional assays, Matrilin-2 induces OPC differentiation, and Inhibin A inhibits OPC Matrilin-2 expression and inhibits OPC differentiation. In vivo, Matrilin-2 promotes motor recovery after white matter stroke, and promotes OPC differentiation and ultrastructural evidence of remyelination. These studies show that white matter stroke induces an initial proliferative and reparative response in OPCs, but this is blocked by a local cellular niche where reactive astrocytes secrete Inhibin A, downregulating Matrilin-2 and blocking myelin repair and recovery.SIGNIFICANCE STATEMENT Stroke in the cerebral white matter of the brain is common. The biology of damage and recovery in this stroke subtype are not well defined. These studies use cell-specific RNA sequencing and gain-of-function studies to show that white matter stroke induces a glial signaling niche, present in both humans and mice, between reactive astrocytes and oligodendrocyte progenitor cells. Astrocyte secretion of Inhibin A and downregulation of oligodendrocyte precursor production of Matrilin-2 limit OPC differentiation, tissue repair, and recovery in this disease.

Nogo receptor blockade overcomes remyelination failure after white matter stroke and stimulates functional recovery in aged mice.

White matter stroke is a distinct stroke subtype, accounting for up to 25% of stroke and constituting the second leading cause of dementia. The biology of possible tissue repair after white matter stroke has not been determined. In a mouse stroke model, white matter ischemia causes focal damage and adjacent areas of axonal myelin disruption and gliosis. In these areas of only partial damage, local white matter progenitors respond to injury, as oligodendrocyte progenitors (OPCs) proliferate. However, OPCs fail to mature into oligodendrocytes (OLs) even in regions of demyelination with intact axons and instead divert into an astrocytic fate. Local axonal sprouting occurs, producing an increase in unmyelinated fibers in the corpus callosum. The OPC maturation block after white matter stroke is in part mediated via Nogo receptor 1 (NgR1) signaling. In both aged and young adult mice, stroke induces NgR1 ligands and down-regulates NgR1 inhibitors during the peak OPC maturation block. Nogo ligands are also induced adjacent to human white matter stroke in humans. A Nogo signaling blockade with an NgR1 antagonist administered after stroke reduces the OPC astrocytic transformation and improves poststroke oligodendrogenesis in mice. Notably, increased white matter repair in aged mice is translated into significant poststroke motor recovery, even when NgR1 blockade is provided during the chronic time points of injury. These data provide a perspective on the role of NgR1 ligand function in OPC fate in the context of a specific and common type of stroke and show that it is amenable to systemic intervention to promote recovery.

Human Endothelial Cell Collection from the Middle Cerebral Artery in Acute Ischemic Stroke.

BACKGROUND: Endovascular treatment for large-vessel acute ischemic stroke (AIS) has rapidly emerged. However, the understanding of the complex biology involving endothelial cells (ECs) remains scarce. METHODS: Using stent retrievers during endovascular thrombectomy (ET) in patients with AIS, ECs were segregated, centrifuged in a dissociation buffer, and suspended in endothelial specific antibody solution. Subsequently, fluorescence-activated cell sorting (FACS) and microscopic analyses were performed. RESULTS: Three stent-retriever devices (2 Solitaire, 1 Trevo) were collected as separate deployments. Of 5.0% (±.48%) total events using FACS, 6.8% (±.68%) of cells were specific for ECs using fluorescent markers and were further visualized on fluorescence microscopy for consistence with the positive controls. CONCLUSIONS: We describe a novel, minimally invasive biopsy technique to collect and harvest ECs from stent retrievers during ET and validate the approach in the treatment of AIS. Further work for detailed characterization and viability assessment of ECs is needed to compare their biology with in vitro and animal models.

Principles of precision medicine in stroke.

The era of precision medicine has arrived and conveys tremendous potential, particularly for stroke neurology. The diagnosis of stroke, its underlying aetiology, theranostic strategies, recurrence risk and path to recovery are populated by a series of highly individualised questions. Moreover, the phenotypic complexity of a clinical diagnosis of stroke makes a simple genetic risk assessment only partially informative on an individual basis. The guiding principles of precision medicine in stroke underscore the need to identify, value, organise and analyse the multitude of variables obtained from each individual to generate a precise approach to optimise cerebrovascular health. Existing data may be leveraged with novel technologies, informatics and practical clinical paradigms to apply these principles in stroke and realise the promise of precision medicine. Importantly, precision medicine in stroke will only be realised once efforts to collect, value and synthesise the wealth of data collected in clinical trials and routine care starts. Stroke theranostics, the ultimate vision of synchronising tailored therapeutic strategies based on specific diagnostic data, demand cerebrovascular expertise on big data approaches to clinically relevant paradigms. This review considers such challenges and delineates the principles on a roadmap for rational application of precision medicine to stroke and cerebrovascular health.

Fluid-Attenuated Inversion Recovery Vascular Hyperintensity Topography, Novel Imaging Marker for Revascularization in Middle Cerebral Artery Occlusion.

BACKGROUND AND PURPOSE: In acute arterial occlusion, fluid-attenuated inversion recovery vascular hyperintensity (FVH) has been linked to slow flow in leptomeningeal collaterals and cerebral hypoperfusion, but the impact on clinical outcome is still controversial. In this study, we aimed to investigate the association between FVH topography or FVH-Alberta Stroke Program Early CT Score (ASPECTS) pattern and outcome in acute M1-middle cerebral artery occlusion patients with endovascular treatment. METHODS: We included acute M1-middle cerebral artery occlusion patients treated with endovascular therapy (ET). All patients had diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery before ET. Distal FVH-ASPECTS was evaluated according to distal middle cerebral artery-ASPECT area (M1-M6) and acute DWI lesion was also reviewed. The presence of FVH inside and outside DWI-positive lesions was separately analyzed. Clinical outcome after ET was analyzed with respect to different distal FVH-ASPECTS topography. RESULTS: Among 101 patients who met inclusion criteria for the study, mean age was 66.2±17.8 years and median National Institutes of Health Stroke Scale was 17.0 (interquartile range, 12.0-21.0). FVH-ASPECTS measured outside of the DWI lesion was significantly higher in patients with good outcome (modified Rankin Scale [mRS] score of 0-2; 8.0 versus 4.0, P<0.001). Logistic regression demonstrated that FVH-ASPECTS outside of the DWI lesion was independently associated with clinical outcome of these patients (odds ratio, 1.3; 95% confidence interval, 1.06-1.68; P=0.013). FVH-ASPECTS inside the DWI lesion was associated with hemorrhagic transformation (odds ratio, 1.3; 95% confidence interval, 1.04-1.51; P=0.019). CONCLUSIONS: Higher FVH-ASPECTS measured outside the DWI lesion is associated with good clinical outcomes in patients undergoing ET. FVH-ASPECTS measured inside the DWI lesion was predictive of hemorrhagic transformation. The FVH pattern, not number, can serve as an imaging selection marker for ET in acute middle cerebral artery occlusion.

Molecular disorganization of axons adjacent to human lacunar infarcts.

Cerebral microvascular disease predominantly affects brain white matter and deep grey matter, resulting in ischaemic damage that ranges from lacunar infarcts to white matter hyperintensities seen on magnetic resonance imaging. These lesions are common and result in both clinical stroke syndromes and accumulate over time, resulting in cognitive deficits and dementia. Magnetic resonance imaging studies suggest that these lesions progress over time, accumulate adjacent to prior lesions and have a penumbral region susceptible to further injury. The pathological correlates of this adjacent injury in surviving myelinated axons have not been previously defined. In this study, we sought to determine the molecular organization of axons in tissue adjacent to lacunar infarcts and in the regions surrounding microinfarcts, by determining critical elements in axonal function: the morphology and length of node of Ranvier segments and adjacent paranodal segments. We examined post-mortem brain tissue from six patients with lacunar infarcts and tissue from two patients with autosomal dominant retinal vasculopathy and cerebral leukoencephalopathy (previously known as hereditary endotheliopathy with retinopathy, nephropathy and stroke) who accumulate progressive white matter ischaemic lesions in the form of lacunar and microinfarcts. In axons adjacent to lacunar infarcts yet extending up to 150% of the infarct diameter away, both nodal and paranodal length increase by ∼20% and 80%, respectively, reflecting a loss of normal cell-cell adhesion and signalling between axons and oligodendrocytes. Using premorbid magnetic resonance images, brain regions from patients with retinal vasculopathy and cerebral leukoencephalopathy that harboured periventricular white matter hyperintensities were selected and the molecular organization of axons was determined within these regions. As in regions adjacent to lacunar infarcts, nodal and paranodal length in white matter of these patients is increased. Myelin basic protein and neurofilament immunolabelling demonstrates that axons in these adjacent regions have preserved axonal cytoskeleton organization and are generally myelinated. This indicates that the loss of normal axonal microdomain architecture results from disrupted axoglial signalling in white matter adjacent to lacunar and microinfarcts. The loss of the normal molecular organization of nodes and paranodes is associated with axonal degeneration and may lead to impaired conduction velocity across surviving axons after stroke. These findings demonstrate that the degree of white matter injury associated with cerebral microvascular disease extends well beyond what can be identified using imaging techniques and that an improved understanding of the neurobiology in these regions can drive new therapeutic strategies for this disease entity.

DWI Lesion Patterns Predict Outcome in Stroke Patients with Thrombolysis.

BACKGROUND: Lesion patterns may predict prognosis after acute ischemic stroke within the middle cerebral artery (MCA) territory; yet it remains unclear whether such imaging prognostic factors are related to patient outcome after intravenous thrombolysis. AIMS: The aim of this study is to investigate the clinical outcome after intravenous thrombolysis in acute MCA ischemic strokes with respect to diffusion-weighted imaging (DWI) lesion patterns. METHODS: Consecutive acute ischemic stroke cases of the MCA territory treated over a 7-year period were retrospectively analyzed. All acute MCA stroke patients underwent a MRI scan before intravenous thrombolytic therapy was included. DWI lesions were divided into 6 patterns (territorial, other cortical, small superficial, internal border zone, small deep, and other deep infarcts). Lesion volumes were measured by dedicated imaging processing software. Favorable outcome was defined as modified Rankin scale (mRS) of 0-2 at 90 days. RESULTS: Among the 172 patients included in our study, 75 (43.6%) were observed to have territorial infarct patterns or other deep infarct patterns. These patients also had higher baseline NIHSS score (p < 0.001), a higher proportion of large cerebral artery occlusions (p < 0.001) and larger infarct volume (p < 0.001). Favorable outcome (mRS 0-2) was achieved in 89 patients (51.7%). After multivariable analysis, groups with specific lesion patterns, including territorial infarct and other deep infarct pattern, were independently associated with favorable outcome (OR 0.40; 95% CI 0.16-0.99; p = 0.047). CONCLUSIONS: Specific lesion patterns predict differential outcome after intravenous thrombolysis therapy in acute MCA stroke patients.

The antiaging protein Klotho enhances oligodendrocyte maturation and myelination of the CNS.

We have previously shown that myelin abnormalities characterize the normal aging process of the brain and that an age-associated reduction in Klotho is conserved across species. Predominantly generated in brain and kidney, Klotho overexpression extends life span, whereas loss of Klotho accelerates the development of aging-like phenotypes. Although the function of Klotho in brain is unknown, loss of Klotho expression leads to cognitive deficits. We found significant effects of Klotho on oligodendrocyte functions, including induced maturation of rat primary oligodendrocytic progenitor cells (OPCs) in vitro and myelination. Phosphoprotein analysis indicated that Klotho's downstream effects involve Akt and ERK signal pathways. Klotho increased OPC maturation, and inhibition of Akt or ERK function blocked this effect on OPCs. In vivo studies of Klotho knock-out mice and control littermates revealed that knock-out mice have a significant reduction in major myelin protein and gene expression. By immunohistochemistry, the number of total and mature oligodendrocytes was significantly lower in Klotho knock-out mice. Strikingly, at the ultrastructural level, Klotho knock-out mice exhibited significantly impaired myelination of the optic nerve and corpus callosum. These mice also displayed severe abnormalities at the nodes of Ranvier. To decipher the mechanisms by which Klotho affects oligodendrocytes, we used luciferase pathway reporters to identify the transcription factors involved. Together, these studies provide novel evidence for Klotho as a key player in myelin biology, which may thus be a useful therapeutic target in efforts to protect brain myelin against age-dependent changes and promote repair in multiple sclerosis.

The back and forth of axonal injury and repair after stroke.

PURPOSE OF REVIEW: The axon plays a central role in both the injury and repair phases after stroke. This review highlights emerging principles in the study of axonal injury in stroke and the role of the axon in neural repair after stroke. RECENT FINDINGS: Ischemic stroke produces a rapid and significant loss of axons in the acute phase. This early loss of axons results from a primary ischemic injury that triggers a wave of calcium signaling, activating proteolytic mechanisms and downstream signaling cascades. A second progressive phase of axonal injury occurs during the subacute period and damages axons that survive the initial ischemic insult but go on to experience a delayed axonal degeneration driven in part by changes in axoglial contact and axonal energy metabolism. Recovery from stroke is dependent on axonal sprouting and reconnection that occurs during a third degenerative/regenerative phase. Despite this central role played by the axon, comparatively little is understood about the molecular pathways that contribute to early and subacute axonal degeneration after stroke. Recent advances in axonal neurobiology and signaling suggest new targets that hold promise as potential molecular therapeutics including axonal calcium signaling, axoglial energy metabolism and cell adhesion as well as retrograde axonal mitogen-activated protein kinase pathways. These novel pathways must be modeled appropriately as the type and severity of axonal injury vary by stroke subtype. SUMMARY: Stroke-induced injury to axons occurs in three distinct phases each with a unique molecular underpinning. A wealth of new data about the molecular organization and molecular signaling within axons is available but not yet robustly applied to the study of axonal injury after stroke. Identifying the spatiotemporal patterning of molecular pathways within the axon that contribute to injury and repair may offer new therapeutic strategies for the treatment of stroke.

Late-Onset COL4A1 Mutation with Recurrent Ischemic and Hemorrhagic Strokes.

INTRODUCTION: Mutations in type IV collagen gene COL4A1 are identified as a cause of autosomal dominant cerebrovascular disease. We report an unusual late-onset presentation. CASE REPORT: A 64-year-old male was found to have an ischemic stroke and diffuse white matter changes. Genetic testing revealed COL4A1 gene mutation of heterozygous Alu insertion at intron 16. Alu elements are known as "jumping genes," and Alu insertion is not previously reported in COL4A1 genetic syndromes. Our case has attributes consistent with a heritable leukoencephalopathy: (1) late-onset presentation, (2) intracerebral hemorrhages and microbleeds, (3) bilateral symmetrical leukoencephalopathy, (4) recurrence over a short period of time, (5) bilateral retinopathy, and (6) family history notable for brain aneurysm, kidney diseases, and early-onset stroke. CONCLUSIONS: Although the majority of COL4A1 genetic syndromes featuring cerebral small vessel disease are in children, this case highlights a late-onset patient with key features of COL4A1 syndromes associated with a heterozygous Alu intronic insertion.

Simultaneous isolation of intact brain cells and cell-specific extracellular vesicles from cryopreserved Alzheimer's disease cortex.

BACKGROUND: The neuronal and gliaI populations within the brain are tightly interwoven, making isolation and study of large populations of a single cell type from brain tissue a major technical challenge. Concurrently, cell-type specific extracellular vesicles (EVs) hold enormous diagnostic and therapeutic potential in neurodegenerative disorders including Alzheimer's disease (AD). NEW METHOD: Postmortem AD cortical samples were thawed and gently dissociated. Following filtration, myelin and red blood cell removal, cell pellets were immunolabeled with fluorescent antibodies and analyzed by flow cytometry. The cell pellet supernatant was applied to a triple sucrose cushion for brain EV isolation. RESULTS: Neuronal, astrocyte and microglial cell populations were identified. Cell integrity was demonstrated using calcein AM, which is retained by cells with esterase activity and an intact membrane. For some experiments cell pellets were fixed, permeabilized, and immunolabeled for cell-specific markers. Characterization of brain small EV fractions showed the expected size, depletion of EV negative markers, and enrichment in positive and cell-type specific markers. COMPARISON WITH EXISTING METHODS AND CONCLUSIONS: We optimized and integrated established protocols, aiming to maximize information obtained from each human autopsy brain sample. The uniqueness of our method lies in its capability to isolate cells and EVs from a single cryopreserved brain sample. Our results not only demonstrate the feasibility of isolating specific brain cell subpopulations for RNA-seq but also validate these subpopulations at the protein level. The accelerated study of EVs from human samples is crucial for a better understanding of their contribution to neuron/glial crosstalk and disease progression.