Multimaterial decomposition in dual-energy CT for characterization of clots from acute ischemic stroke patients.

BACKGROUND: Nowadays, there is no method to quantitatively characterize the material composition of acute ischemic stroke thrombi prior to intervention, but dual-energy CT (DE-CT) offers imaging-based multimaterial decomposition. We retrospectively investigated the material composition of thrombi ex vivo using DE-CT with histological analysis as a reference. METHODS: Clots of 70 patients with acute ischemic stroke were extracted by mechanical thrombectomy and scanned ex vivo in formalin-filled tubes with DE-CT. Multimaterial decomposition in the three components, i.e., red blood cells (RBC), white blood cells (WBC), and fibrin/platelets (F/P), was performed and compared to histology (hematoxylin/eosin staining) as reference. Attenuation and effective Z values were assessed, and histological composition was compared to stroke etiology according to the Trial of ORG 10172 in Acute Stroke Treatment (TOAST) criteria. RESULTS: Histological and imaging analysis showed the following correlation coefficients for RBC (r = 0.527, p < 0.001), WBC (r = 0.305, p = 0.020), and F/P (r = 0.525, p < 0.001). RBC-rich thrombi presented higher clot attenuation in Hounsfield units than F/P-rich thrombi (51 HU versus 42 HU, p < 0.01). In histological analysis, cardioembolic clots showed less RBC (40% versus 56%, p = 0.053) and more F/P (53% versus 36%, p = 0.024), similar to cryptogenic clots containing less RBC (34% versus 56%, p = 0.006) and more F/P (58% versus 36%, p = 0.003) than non-cardioembolic strokes. No difference was assessed for the mean WBC portions in all TOAST groups. CONCLUSIONS: DE-CT has the potential to quantitatively characterize the material composition of ischemic stroke thrombi. RELEVANCE STATEMENT: Using DE-CT, the composition of ischemic stroke thrombi can be determined. Knowledge of histological composition prior to intervention offers the opportunity to define personalized treatment strategies for each patient to accomplish faster recanalization and better clinical outcomes. KEY POINTS: • Acute ischemic stroke clots present different recanalization success according to histological composition. • Currently, no method can determine clot composition prior to intervention. • DE-CT allows quantitative material decomposition of thrombi ex vivo in red blood cells, white blood cells, and fibrin/platelets. • Histological clot composition differs between stroke etiology. • Insights into the histological composition in situ offer personalized treatment strategies.

Effects of isorhamnetin on liver injury in heat stroke-affected rats under dry-heat environments via oxidative stress and inflammatory response.

Isorhamnetin is a natural flavonoid compound, rich in brass, alkaloids, and sterols with a high medicinal value. This study investigated the effects of isorhamnetin on liver injury and oxidative and inflammatory responses in heat-stroke-affected rats in a dry-heat environment. Fifty Sprague Dawley rats were randomly divided into five groups: normal temperature control (NC, saline), dry-heat control (DHC, saline), low-dose isorhamnetin-pretreated (L-AS, 25 mg/Kg), medium-dose isorhamnetin-pretreated (M-AS, 50 mg/Kg), and high-dose isorhamnetin-pretreated (H-AS, 100 mg/Kg) group. Saline was administered to the NC and DHC groups and corresponding concentrations of isorhamnetin were administered to the remaining three groups for 1 week. Blood and liver tissue were analyzed for oxidative stress and inflammation. The liver histopathological injury score, serum liver enzyme (alanine transaminase, aspartate transaminase, and lactate dehydrogenase), liver oxidative stress index (superoxide dismutase [SOD], catalase [CAT], and malondialdehyde), and inflammation index (tumor necrosis factor α [TNF-α], interleukin [IL]-1ß, IL-6, and lipopolysaccharides) were significantly higher in the DHC group than in the NC group (P < 0.05). These index values in the L-AS, M-AS, and H-AS groups were significantly lower than those in the DHC group (P < 0.05). The index values decreased significantly with an increase in the concentration of isorhamnetin (P < 0.05), while the index values of CAT and SOD showed the opposite tendency (P < 0.05). The expression of liver tissue nuclear factor kappa B (NF-κB), caspase-3, and heat shock protein (HSP-70) was higher in the DHC group than in the NC group (P < 0.05). Comparison between the isorhamnetin and DHC groups revealed that the expression of NF-кB and caspase-3 was decreased, while that of HSP-70 continued to increase (P < 0.05). The difference was significant for HSP-70 among all the isorhamnetin groups (P < 0.05); however, the NF-кB and caspase-3 values in the L-AS and H-AS groups did not differ. In summary, isorhamnetin has protective effects against liver injury in heat-stroke-affected rats. This protective effect may be related to its activities concerning antioxidative stress, anti-inflammatory response, inhibition of NF-кB and caspase-3 expression, and enhancement of HSP-70 expression.

Drug Delivery Angle for Various Atherosclerosis and Aneurysm Percentages of the Carotid Artery.

Stroke is the second cause of mortality among adult males and the first cause of death in adult females all around the world. It is also recognized as one of the most important causes of morbidity and dementia in adults. Stenosis or rupture of the only channels of the blood supply from the heart to the brain (carotid arteries) is among the main causes of stroke. In this regard, treatment of the lesions of carotid arteries, including atherosclerosis and aneurysm, could be a huge step in preventing stroke and improving brain performance. Targeted drug delivery by drug-carrying nanoparticles is the latest method for optimal delivery of drug to the damaged parts of the artery. In this study, a wide range of carotid artery lesions, including different percentages of atherosclerosis and aneurysm, were considered. After analyzing the dynamics of the fluid flow in different damaged regions and selecting the magnetic framework with proper ligand (Fe3O4@MOF) as the drug carrier, the size of the particles and their number per cycle were analyzed. Based on the results, the particle size of 100 nm and the use of 300 particles per injection at each cardiac cycle can result in maximum drug delivery to the target site. Then, the effect of the hospital bed angle on drug delivery was investigated. The results showed a unique optimal drug delivery angle for each extent of atherosclerosis or aneurysm. For example, in a 50% aneurysm, drug delivery at an angle of 30° is about 387% higher than that at an angle of 15°. Finally, simulation of real geometry indicated the effectiveness of simple geometry instead of real geometry for the simulation of carotid arteries, which can remarkably decrease the computational time and costs.

Consistent spatial lesion-symptom patterns: A comprehensive analysis using triangulation in lesion-symptom mapping in a cohort of stroke patients.

INTRODUCTION: The relationship between brain lesions and stroke outcomes is crucial for advancing patient prognosis and developing effective therapies. Stroke is a leading cause of disability worldwide, and it is important to understand the neurological basis of its varied symptomatology. Lesion-symptom mapping (LSM) methods provide a means to identify brain areas that are strongly associated with specific symptoms. However, inner variations in LSM methods can yield different results. To address this, our study aimed to characterize the lesion-symptom mapping variability using three different LSM methods. Specifically, we sought to determine a lesion symptom core across LSM approaches enhancing the robustness of the analysis and removing potential spatial bias. MATERIAL & METHODS: A cohort consisting of 35 patients with either right- or left-sided middle cerebral artery strokes were enrolled and evaluated using the NIHSS at 24 h post-stroke. Anatomical T1w MRI scans were also obtained 24 h post-stroke. Lesion masks were segmented manually and three distinctive LSM methods were implemented: ROI correlation-based, univariate, and multivariate approaches. RESULTS: The results of the LSM analyses showed substantial spatial differences in the extension of each of the three lesion maps. However, upon overlaying all three lesion-symptom maps, a consistent lesion core emerged, corresponding to the territory associated with elevated NIHSS scores. This finding not only enhances the spatial accuracy of the lesion map but also underscores its clinical relevance. CONCLUSION: This study underscores the significance of exploring complementary LSM approaches to investigate the association between brain lesions and stroke outcomes. By utilizing multiple methods, we can increase the robustness of our results, effectively addressing and neutralizing potential spatial bias introduced by each individual method. Such an approach holds promise for enhancing our understanding of stroke pathophysiology and optimizing patient care strategies.

LOX-1 and MMP-9 Inhibition Attenuates the Detrimental Effects of Delayed rt-PA Therapy and Improves Outcomes After Acute Ischemic Stroke.

BACKGROUND: Acute ischemic stroke triggers endothelial activation that disrupts vascular integrity and increases hemorrhagic transformation leading to worsened stroke outcomes. rt-PA (recombinant tissue-type plasminogen activator) is an effective treatment; however, its use is limited due to a restricted time window and hemorrhagic transformation risk, which in part may involve activation of MMPs (matrix metalloproteinases) mediated through LOX-1 (lectin-like oxLDL [oxidized low-density lipoprotein] receptor 1). This study's overall aim was to evaluate the therapeutic potential of novel MMP-9 (matrix metalloproteinase 9) ± LOX-1 inhibitors in combination with rt-PA to improve stroke outcomes. METHODS: A rat thromboembolic stroke model was utilized to investigate the impact of rt-PA delivered 4 hours poststroke onset as well as selective MMP-9 (JNJ0966) ±LOX-1 (BI-0115) inhibitors given before rt-PA administration. Infarct size, perfusion, and hemorrhagic transformation were evaluated by 9.4-T magnetic resonance imaging, vascular and parenchymal MMP-9 activity via zymography, and neurological function was assessed using sensorimotor function testing. Human brain microvascular endothelial cells were exposed to hypoxia plus glucose deprivation/reperfusion (hypoxia plus glucose deprivation 3 hours/R 24 hours) and treated with ±tPA and ±MMP-9 ±LOX-1 inhibitors. Barrier function was assessed via transendothelial electrical resistance, MMP-9 activity was determined with zymography, and LOX-1 and barrier gene expression/levels were measured using qRT-PCR (quantitative reverse transcription PCR) and Western blot. RESULTS: Stroke and subsequent rt-PA treatment increased edema, hemorrhage, MMP-9 activity, LOX-1 expression, and worsened neurological outcomes. LOX-1 inhibition improved neurological function, reduced edema, and improved endothelial barrier integrity. Elevated MMP-9 activity correlated with increased edema, infarct volume, and decreased neurological function. MMP-9 inhibition reduced MMP-9 activity and LOX-1 expression. In human brain microvascular endothelial cells, LOX-1/MMP-9 inhibition differentially attenuated MMP-9 levels, inflammation, and activation following hypoxia plus glucose deprivation/R. CONCLUSIONS: Our findings indicate that LOX-1 inhibition and ± MMP-9 inhibition attenuate negative aspects of ischemic stroke with rt-PA therapy, thus resulting in improved neurological function. While no synergistic effect was observed with simultaneous LOX-1 and MMP-9 inhibition, a distinct interaction is evident.

Pericyte Microvesicles as Plasma Biomarkers Reflecting Brain Microvascular Signaling in Patients With Acute Ischemic Stroke.

BACKGROUND: Blood-based biomarkers have the potential to reflect cerebrovascular signaling after microvascular injury; yet, the detection of cell-specific signaling has proven challenging. Microvesicles retain parental cell surface antigens allowing detection of cell-specific signaling encoded in their cargo. In ischemic stroke, the progression of pathology involves changes in microvascular signaling whereby brain pericytes, perivascular cells wrapping the microcapillaries, are one of the early responders to the ischemic insult. Intercepting the pericyte signaling response peripherally by isolating pericyte-derived microvesicles may provide not only diagnostic information on microvascular injury but also enable monitoring of important pathophysiological mechanisms. METHODS: Plasma samples were collected from patients with acute ischemic stroke (n=39) at 3 time points after stroke onset: 0 to 6 hours, 12 to 24 hours, and 2 to 6 days, and compared with controls (n=39). Pericyte-derived microvesicles were isolated based on cluster of differentiation 140b expression and quantified by flow cytometry. The protein content was evaluated using a proximity extension assay, and vascular signaling pathways were examined using molecular signature hallmarks and gene ontology. RESULTS: In this case-control study, patients with acute ischemic stroke showed significantly increased numbers of pericyte-derived microvesicles (median, stroke versus controls) at 12 to 24 hours (1554 versus 660 microvesicles/µL; P=0.0041) and 2 to 6 days after stroke (1346 versus 660 microvesicles/µL; P=0.0237). Their proteome revealed anti-inflammatory properties mediated via downregulation of Kirsten rat sarcoma virus and IL (interleukin)-6/JAK/STAT3 signaling at 0 to 6 hours, but proangiogenic as well as proinflammatory signals at 12 to 24 hours. Between 2 and 6 days, proteins were mainly associated with vascular remodeling as indicated by activation of Hedgehog signaling in addition to proangiogenic signals. CONCLUSIONS: We demonstrate that the plasma of patients with acute ischemic stroke reflects (1) an early and time-dependent increase of pericyte-derived microvesicles and (2) changes in the protein cargo of microvesicles over time indicating cell signaling specifically related to inflammation and vascular remodeling.

Absence in CX3CR1 receptor signaling promotes post-ischemic stroke cognitive function recovery through suppressed microglial pyroptosis in mice.

BACKGROUND: Post-stroke cognitive impairment (PSCI) is a major source of morbidity and mortality after stroke, but the pathological mechanisms remain unclear. Previous studies have demonstrated that the CX3CR1 receptor plays a crucial role in maintaining an early protective microenvironment after stroke, but whether it persistently influences cognitive dysfunction in the chronic phase requires further investigation. METHODS: Mouse was used to establish a middle cerebral artery occlusion (MCAO)/reperfusion model to study PSCI. Cognitive function was assessed by the Morris water maze (MWM) and the novel object recognition test. Neurogenesis was assessed by immunofluorescence staining with Nestin+ /Ki67+ and DCX+ /BrdU+ double-positive cells. The cerebral damage was monitored by [18 F]-DPA-714 positron emission tomography, Nissel, and TTC staining. The pyroptosis was histologically, biochemically, and electron microscopically examined. RESULTS: Upon MCAO, at 28 to 35 days, CX3CR1 knockout (CX3CR1-/- ) mice had better cognitive behavioral performance both in MWM and novel object recognition test than their CX3CR1+/- counterparts. Upon MCAO, at 7 days, CX3CR1-/- mice increased the numbers of Nestin+ /Ki67+ and DCX+ /BrdU+ cells, and meanwhile it decreased the protein expression of GSDMD, NLRP3 inflammasome subunit, caspase-1, mature IL-1ß/IL-18, and p-P65 in the hippocampus as compared with CX3CR1+/- mice. In addition, CX3CR1-/- mice could reverse infarct volume in the hippocampus region post-stroke. CONCLUSION: Our study demonstrated that CX3CR1 gene deletion was beneficial to PSCI recovery. The mechanism might lie in inhibited pyroptosis and enhanced neurogenesis. CX3CR1 receptor may serve as a therapeutic target for improving the PSCI.

On the Impact of Residual Strains in the Stress Analysis of Patient-Specific Atherosclerotic Carotid Vessels: Predictions Based on the Homogenous Stress Hypothesis.

The identification of carotid atherosclerotic lesion at risk for plaque rupture, eventually resulting in cerebral embolism and stroke, is of paramount clinical importance. High stress in the fibrous plaque cap has been proposed as risk factor. However, among others, residual strains influence said stress predictions, but quantitative and qualitative implications of residual strains in this context are not well explored. We therefore propose a multiplicative kinematics-based Growth and Remodeling (G&R) framework to predict residual strains from homogenizing tissue stress and then investigate its implication on plaque stress. Carotid vessel morphology of four patients was reconstructed from clinical Computed Tomography-Angiography (CT-A) images and equipped with heterogeneous tissue constitutive properties assigned through a histology-based artificial intelligence image segmentation tool. As compared to a purely elastic analysis and depending on patient-specific morphology and tissue distributions, the incorporation of residual strains reduced the maximum wall stress by up to 30 % and resulted in a fundamentally different distribution of stress across the atherosclerotic wall. Regardless residual strains homogenized tissue stresses, the fibrous plaque cap may persistently be exposed to spots of high stress. In conclusion, the incorporation of residual strains in biomechanical studies of atherosclerotic carotids may be important for a reliable assessment of fibrous plaque cap stress.

Hippocampal capillary pericytes in post-stroke and vascular dementias and Alzheimer's disease and experimental chronic cerebral hypoperfusion.

Neurovascular unit mural cells called 'pericytes' maintain the blood-brain barrier and local cerebral blood flow. Pathological changes in the hippocampus predispose to cognitive impairment and dementia. The role of hippocampal pericytes in dementia is largely unknown. We investigated hippocampal pericytes in 90 post-mortem brains from post-stroke dementia (PSD), vascular dementia (VaD), Alzheimer's disease (AD), and AD-VaD (Mixed) subjects, and post-stroke non-demented survivors as well as similar age controls. We used collagen IV immunohistochemistry to determine pericyte densities and a mouse model of VaD to validate the effects of chronic cerebral hypoperfusion. Despite increased trends in hippocampal microvascular densities across all dementias, mean pericyte densities were reduced by ~25-40% in PSD, VaD and AD subjects compared to those in controls, which calculated to 14.1 ± 0.7 per mm capillary length, specifically in the cornu ammonis (CA) 1 region (P = 0.01). In mice with chronic bilateral carotid artery occlusion, hippocampal pericyte loss was ~60% relative to controls (P < 0.001). Pericyte densities were correlated with CA1 volumes (r = 0.54, P = 0.006) but not in any other sub-region. However, mice subjected to the full-time environmental enrichment (EE) paradigm showed remarkable attenuation of hippocampal CA1 pericyte loss in tandem with CA1 atrophy. Our results suggest loss of hippocampal microvascular pericytes across common dementias is explained by a vascular aetiology, whilst the EE paradigm offers significant protection.

Association of Rare NOTCH3 Variants With Prevalent and Incident Stroke and Dementia in the General Population.

BACKGROUND: It is uncertain whether rare NOTCH3 variants are associated with stroke and dementia in the general population and whether they lead to alterations in cognitive function. This study aims to determine the associations of rare NOTCH3 variants with prevalent and incident stroke and dementia, as well as cognitive function changes. METHODS AND RESULTS: In the prospective community-based Shunyi Study, a total of 1007 participants were included in the baseline analysis. For the follow-up analysis, 1007 participants were included in the stroke analysis, and 870 participants in the dementia analysis. All participants underwent baseline brain magnetic resonance imaging, carotid ultrasound, and whole exome sequencing. Rare NOTCH3 variants were defined as variants with minor allele frequency <1%. A total of 137 rare NOTCH3 carriers were enrolled in the baseline study. At baseline, rare NOTCH3 variant carriers had higher rates of stroke (8.8% versus 5.6%) and dementia (2.9% versus 0.8%) compared with noncarriers. After adjustment for associated risk factors, the epidermal growth factor-like repeats (EGFr)-involving rare NOTCH3 variants were associated with a higher risk of prevalent stroke (odds ratio [OR], 2.697 [95% CI, 1.266-5.745]; P=0.040) and dementia (OR, 8.498 [95% CI, 1.727-41.812]; P=0.032). After 5 years of follow-up, we did not find that the rare NOTCH3 variants increased the risk of incident stroke and dementia. There was no statistical difference in the change in longitudinal cognitive scale scores. CONCLUSIONS: Rare NOTCH3 EGFr-involving variants are genetic risk factors for stroke and dementia in the general Chinese population.

Profiling of microglia nodules in multiple sclerosis reveals propensity for lesion formation.

Microglia nodules (HLA-DR+ cell clusters) are associated with brain pathology. In this post-mortem study, we investigated whether they represent the first stage of multiple sclerosis (MS) lesion formation. We show that microglia nodules are associated with more severe MS pathology. Compared to microglia nodules in stroke, those in MS show enhanced expression of genes previously found upregulated in MS lesions. Furthermore, genes associated with lipid metabolism, presence of T and B cells, production of immunoglobulins and cytokines, activation of the complement cascade, and metabolic stress are upregulated in microglia nodules in MS. Compared to stroke, they more frequently phagocytose oxidized phospholipids and possess a more tubular mitochondrial network. Strikingly, in MS, some microglia nodules encapsulate partially demyelinated axons. Taken together, we propose that activation of microglia nodules in MS by cytokines and immunoglobulins, together with phagocytosis of oxidized phospholipids, may lead to a microglia phenotype prone to MS lesion formation.

The paradox of tPA in ischemic stroke: tPA knockdown following recanalization improves functional and histological outcomes.

Previous studies have demonstrated that endogenous tissue-type plasminogen activator (tPA) is upregulated in the brain after an acute ischemic stroke (AIS). While mixed results were observed in genetic models, the pharmacological inhibition of endogenous tPA showed beneficial effects. Treatment with exogenous recombinant tPA exacerbated brain damage in rodent models of stroke. Despite the detrimental effects of tPA in ischemic stroke, recombinant tPA is administered to AIS patients to recanalize the occluded blood vessels because the benefits of its administration outweigh the risks associated with tPA upregulation and increased activity. We hypothesized that tPA knockdown following recanalization would ameliorate sensorimotor deficits and reduce brain injury. Young male and female rats (2-3 months old) were subjected to transient focal cerebral ischemia by occlusion of the right middle cerebral artery. Shortly after reperfusion, rats from appropriate cohorts were administered a nanoparticle formulation containing tPA shRNA or control shRNA plasmids (1 mg/kg) intravenously via the tail vein. Infarct volume during acute and chronic phases, expression of matrix metalloproteinases (MMPs) 1, 3, and 9, enlargement of cerebral ventricle volume, and white matter damage were all reduced by shRNA-mediated gene silencing of tPA following reperfusion. Additionally, recovery of somatosensory and motor functions was improved. In conclusion, our results provide evidence that reducing endogenous tPA following recanalization improves functional outcomes and reduces post-stroke brain damage.

Mitochondrial stress: a key role of neuroinflammation in stroke.

Stroke is a clinical syndrome characterized by an acute, focal neurological deficit, primarily caused by the occlusion or rupture of cerebral blood vessels. In stroke, neuroinflammation emerges as a pivotal event contributing to neuronal cell death. The occurrence and progression of neuroinflammation entail intricate processes, prominently featuring mitochondrial dysfunction and adaptive responses. Mitochondria, a double membrane-bound organelle are recognized as the "energy workshop" of the body. Brain is particularly vulnerable to mitochondrial disturbances due to its high energy demands from mitochondria-related energy production. The interplay between mitochondria and neuroinflammation plays a significant role in the pathogenesis of stroke. The biological and pathological consequences resulting from mitochondrial stress have substantial implications for cerebral function. Mitochondrial stress serves as an adaptive mechanism aimed at mitigating the stress induced by the import of misfolded proteins, which occurs in response to stroke. This adaptive response involves a reduction in misfolded protein accumulation and overall protein synthesis. The influence of mitochondrial stress on the pathological state of stroke is underscored by its capacity to interact with neuroinflammation. The impact of mitochondrial stress on neuroinflammation varies according to its severity. Moderate mitochondrial stress can bolster cellular adaptive defenses, enabling cells to better withstand detrimental stressors. In contrast, sustained and excessive mitochondrial stress detrimentally affects cellular and tissue integrity. The relationship between neuroinflammation and mitochondrial stress depends on the degree of mitochondrial stress present. Understanding its role in stroke pathogenesis is instrumental in excavating the novel treatment of stroke. This review aims to provide the evaluation of the cross-talk between mitochondrial stress and neuroinflammation within the context of stroke. We aim to reveal how mitochondrial stress affects neuroinflammation environment in stroke.

The contribution of ß-amyloid, Tau and α-synuclein to blood-brain barrier damage in neurodegenerative disorders.

Central nervous system (CNS) accumulation of fibrillary deposits made of Amyloid ß (Aß), hyperphosphorylated Tau or α-synuclein (α-syn), present either alone or in the form of mixed pathology, characterizes the most common neurodegenerative diseases (NDDs) as well as the aging brain. Compelling evidence supports that acute neurological disorders, such as traumatic brain injury (TBI) and stroke, are also accompanied by increased deposition of toxic Aß, Tau and α-syn species. While the contribution of these pathological proteins to neurodegeneration has been experimentally ascertained, the cellular and molecular mechanisms driving Aß, Tau and α-syn-related brain damage remain to be fully clarified. In the last few years, studies have shown that Aß, Tau and α-syn may contribute to neurodegeneration also by inducing and/or promoting blood-brain barrier (BBB) disruption. These pathological proteins can affect BBB integrity either directly by affecting key BBB components such as pericytes and endothelial cells (ECs) or indirectly, by promoting brain macrophages activation and dysfunction. Here, we summarize and critically discuss key findings showing how Aß, Tau and α-syn can contribute to BBB damage in most common NDDs, TBI and stroke. We also highlight the need for a deeper characterization of the role of these pathological proteins in the activation and dysfunction of brain macrophages, pericytes and ECs to improve diagnosis and treatment of acute and chronic neurological disorders.

C-Reactive Protein, Interleukin-6, and Vascular Recurrence According to Stroke Subtype: An Individual Participant Data Meta-Analysis

BACKGROUND AND OBJECTIVES: Anti-inflammatory therapies reduce major adverse cardiovascular events (MACE) in coronary artery disease but remain unproven after stroke. Establishing the subtype-specific association between inflammatory markers and recurrence risk is essential for optimal selection of patients in randomized trials (RCTs) of anti-inflammatory therapies for secondary stroke prevention. METHODS: Using individual participant data (IPD) identified from a systematic review, we analyzed the association between high-sensitivity C-reactive protein, interleukin-6 (IL-6), and vascular recurrence after ischemic stroke or transient ischemic attack. The prespecified coprimary end points were (1) any recurrent MACE (first major coronary event, recurrent stroke, or vascular death) and (2) any recurrent stroke (ischemic, hemorrhagic, or unspecified) after sample measurement. Analyses were performed stratified by stroke mechanism, per quarter and per biomarker unit increase after loge transformation. We then did study-level meta-analysis with comparable published studies not providing IPD. Preferred Reporting Items for Systematic Review and Meta-Analyses IPD guidelines were followed. RESULTS: IPD was obtained from 10 studies (8,420 patients). After adjustment for vascular risk factors and statins/antithrombotic therapy, IL-6 was associated with recurrent MACE in stroke caused by large artery atherosclerosis (LAA) (risk ratio [RR] 2.30, 95% CI 1.21-4.36, p = 0.01), stroke of undetermined cause (UND) (RR 1.78, 1.19-2.66, p = 0.005), and small vessel occlusion (SVO) (RR 1.71, 0.99-2.96, p = 0.053) (quarter 4 [Q4] vs quarter 1 [Q1]). No association was observed for stroke due to cardioembolism or other determined cause. Similar results were seen for recurrent stroke and when analyzed per loge unit increase for MACE (LAA, RR 1.26 [1.06-1.50], p = 0.009; SVO, RR 1.22 [1.01-1.47], p = 0.04; UND, RR 1.18 [1.04-1.34], p = 0.01). High-sensitivity CRP was associated with recurrent MACE in UND stroke only (Q4 vs Q1 RR 1.45 [1.04-2.03], p = 0.03). Findings were consistent on study-level meta-analysis of the IPD results with 2 other comparable studies (20,136 patients). DISCUSSION: Our data provide new evidence for the selection of patients in future RCTs of anti-inflammatory therapy in stroke due to large artery atherosclerosis, small vessel occlusion, and undetermined etiology according to inflammatory marker profile.

Parabiosis Discriminates the Circulating, Endothelial, and Parenchymal Contributions of Endogenous Tissue-Type Plasminogen Activator to Stroke.

BACKGROUND: Intravenous injection of alteplase, a recombinant tPA (tissue-type plasminogen activator) as a thrombolytic agent has revolutionized ischemic stroke management. However, tPA is a more complex enzyme than expected, being for instance able to promote thrombolysis, but at the same time, also able to influence neuronal survival and to affect the integrity of the blood-brain barrier. Accordingly, the respective impact of endogenous tPA expressed/present in the brain parenchyma versus in the circulation during stroke remains debated. METHODS: To address this issue, we used mice with constitutive deletion of tPA (tPANull [tPA-deficient mice]) or conditional deletion of endothelial tPA (VECad [vascular endothelial-Cadherin-Cre-recombinase]-Cre∆tPA). We also developed parabioses between tPANull and wild-type mice (tPAWT), anticipating that a tPAWT donor would restore levels of tPA to normal ones, in the circulation but not in the brain parenchyma of a tPANull recipient. Stroke outcomes were investigated by magnetic resonance imaging in a thrombo-embolic or a thrombotic stroke model, induced by local thrombin injection or FeCl3 application on the endothelium, respectively. RESULTS: First, our data show that endothelial tPA, released into the circulation after stroke onset, plays an overall beneficial role following thrombo-embolic stroke. Accordingly, after 24 hours, tPANull/tPANull parabionts displayed less spontaneous recanalization and reperfusion and larger infarcts compared with tPAWT/tPAWT littermates. However, when associated to tPAWT littermates, tPANull mice had similar perfusion deficits, but less severe brain infarcts. In the thrombotic stroke model, homo- and hetero-typic parabionts did not differ in the extent of brain damages and did not differentially recanalize and reperfuse. CONCLUSIONS: Together, our data reveal that during thromboembolic stroke, endogenous circulating tPA from endothelial cells sustains a spontaneous recanalization and reperfusion of the tissue, thus, limiting the extension of ischemic lesions. In this context, the impact of endogenous parenchymal tPA is limited.

Prolonged myelin deficits contribute to neuron loss and functional impairments after ischaemic stroke.

Ischaemic stroke causes neuron loss and long-term functional deficits. Unfortunately, effective approaches to preserving neurons and promoting functional recovery remain unavailable. Oligodendrocytes, the myelinating cells in the CNS, are susceptible to oxygen and nutrition deprivation and undergo degeneration after ischaemic stroke. Technically, new oligodendrocytes and myelin can be generated by the differentiation of oligodendrocyte precursor cells (OPCs). However, myelin dynamics and their functional significance after ischaemic stroke remain poorly understood. Here, we report numerous denuded axons accompanied by decreased neuron density in sections from ischaemic stroke lesions in human brain, suggesting that neuron loss correlates with myelin deficits in these lesions. To investigate the longitudinal changes in myelin dynamics after stroke, we labelled and traced pre-existing and newly-formed myelin, respectively, using cell-specific genetic approaches. Our results indicated massive oligodendrocyte death and myelin loss 2 weeks after stroke in the transient middle cerebral artery occlusion (tMCAO) mouse model. In contrast, myelin regeneration remained insufficient 4 and 8 weeks post-stroke. Notably, neuronal loss and functional impairments worsened in aged brains, and new myelin generation was diminished. To analyse the causal relationship between remyelination and neuron survival, we manipulated myelinogenesis by conditional deletion of Olig2 (a positive regulator) or muscarinic receptor 1 (M1R, a negative regulator) in OPCs. Deleting Olig2 inhibited remyelination, reducing neuron survival and functional recovery after tMCAO. Conversely, enhancing remyelination by M1R conditional knockout or treatment with the pro-myelination drug clemastine after tMCAO preserved white matter integrity and neuronal survival, accelerating functional recovery. Together, our findings demonstrate that enhancing myelinogenesis is a promising strategy to preserve neurons and promote functional recovery after ischaemic stroke.

Progressive lesion necrosis is related to increasing aphasia severity in chronic stroke.

BACKGROUND: Volumetric investigations of cortical damage resulting from stroke indicate that lesion size and shape continue to change even in the chronic stage of recovery. However, the potential clinical relevance of continued lesion growth has yet to be examined. In the present study, we investigated the prevalence of lesion expansion and the relationship between expansion and changes in aphasia severity in a large sample of individuals in the chronic stage of aphasia recovery. METHODS: Retrospective structural MRI scans from 104 S survivors with at least 2 observations (k = 301 observations; mean time between scans = 31 months) were included. Lesion demarcation was performed using an automated lesion segmentation software and lesion volumes at each timepoint were subsequently calculated. A linear mixed effects model was conducted to investigate the effect of days between scan on lesion expansion. Finally, we investigated the association between lesion expansion and changes on the Western Aphasia Battery (WAB) in a group of participants assessed and scanned at 2 timepoints (N = 54) using a GLM. RESULTS: Most participants (81 %) showed evidence of lesion expansion. The mixed effects model revealed lesion volumes significantly increase, on average, by 0.02 cc each day (7.3 cc per year) following a scan (p < 0.0001). Change on language performance was significantly associated with change in lesion volume (p = 0.025) and age at stroke (p = 0.031). The results suggest that with every 10 cc increase in lesion size, language performance decreases by 0.9 points, and for every 10-year increase in age at stroke, language performance decreases by 1.9 points. CONCLUSIONS: The present study confirms and extends prior reports that lesion expansion occurs well into the chronic stage of stroke. For the first time, we present evidence that expansion is predictive of longitudinal changes in language performance in individuals with aphasia. Future research should focus on the potential mechanisms that may lead to necrosis in areas surrounding the chronic stroke lesion.