Intestinal MAdCAM-1 imaging as biomarker for prognostic in murine models of multiple sclerosis.

INTRODUCTION: Multiple sclerosis (MS) is an autoimmune disease of the central nervous system. Recent evidence suggests that lymphocyte trafficking in the intestines could play a key role in its etiology. Nevertheless, it is not clear how intestinal tissue is involved in the disease onset nor its evolution. In the present study, we aimed to evaluate intestinal inflammation dynamic throughout the disease course and its potential impact on disease progression. METHODS: We used tissue immunophenotyping (immunohistofluorescence and flow cytometry) and a recently described molecular magnetic resonance imaging (MRI) method targeting mucosal addressin cell adhesion molecule-1 (MAdCAM-1) to assess intestinal inflammation in vivo in two distinct animal models of MS (Experimental Autoimmune Encephalomyelitis - EAE) at several time points of disease progression. RESULTS: We report a positive correlation between disease severity and MAdCAM-1 MRI signal in two EAE models. Moreover, high MAdCAM-1 MRI signal during the asymptomatic phase is associated with a delayed disease onset in progressive EAE and to a lower risk of conversion to a secondary-progressive form in relapsing-remitting EAE. During disease evolution, in line with a bi-directional immune communication between the gut and the central nervous system, we observed a decrease in T-CD4+ and B lymphocytes in the ileum concomitantly with their increase in the spinal cord. CONCLUSION: Altogether, these data unveil a crosstalk between intestinal and central inflammation in EAE and support the use of molecular MRI of intestinal MAdCAM-1 as a new biomarker for prognostic in MS patients.

N-Acetylcysteine to Reduce Mortality for Patients Requiring Cardiac Catheterization or Cardiac Surgery: A Systematic Review and Meta-analysis.

ABSTRACT: Multimers of von Willebrand factor play a critical role in various processes inducing morbidity and mortality in cardiovascular-risk patients. With the ability to reduce von Willebrand factor multimers, N-acetylcysteine (NAC) could reduce mortality in patients undergoing coronary catheterization or cardiac surgery. However, its impact in perioperative period has never been studied so far in regard of its potential cardiovascular benefits. Then, 4 databases were searched for randomized controlled trials that compared in-hospital mortality between an experimental group, with NAC, and a control group without NAC, in patients undergoing coronary catheterization or cardiac surgery. The primary efficacy outcome was in-hospital mortality. Secondary outcomes were the occurrence of thrombotic events, major cardiovascular events, myocardial infarction, and contrast-induced nephropathy. The safety outcome was occurrence of hemorrhagic events. Nineteen studies totaling 3718 patients were included. Pooled analysis demonstrated a reduction of in-hospital mortality associated with NAC: odds ratio, 0.60; 95% confidence interval, 0.39-0.92; P = 0.02. The occurrence of secondary outcomes was not significantly reduced with NAC except for contrast-induced nephropathy. No difference was reported for hemorrhagic events. Subgroup analyses revealed a life-saving effect of NAC in a dose-dependent manner with reduction of in-hospital mortality for the NAC high-dose group, but not for the NAC standard-dose (<3500-mg) group. In conclusion, without being able to conclude on the nature of the mechanism involved, our review suggests a benefit of NAC in cardiovascular-risk patients in perioperative period in terms of mortality and supports prospective confirmatory studies.

Time from I.V. Thrombolysis to Thrombectomy and Outcome in Acute Ischemic Stroke.

OBJECTIVE: Whether the time from intravenous thrombolysis (IVT) to endovascular treatment (EVT) in patients with acute ischemic stroke has an effect on the functional outcome is unknown. METHODS: The Endovascular Treatment in Ischemic Stroke (ETIS) registry is an ongoing, prospective, multicenter, observational study that perform EVT in France. Data were analyzed from patients treated by IVT and EVT between October 2013 and December 2018 in 6 comprehensive stroke centers. In the primary analysis, we assessed the association of time from IVT administration to start of EVT with functional outcome (measured with the modified Rankin Scale [mRS]), by means of ordinal logistic regression. Secondary end points included angiographic and safety outcomes. RESULTS: We analyzed 1,986 patients with acute ischemic stroke due to anterior circulation large vessel occlusion who underwent IVT and EVT. An increased IVT to start of EVT time was associated with a worse functional outcome at 90 days (mRS = 0-2, adjusted odds ratio [OR] per 30 minutes increase in time = 0.91, 95% confidence interval [CI] = 0.86-0.96; mRS = 0-1, adjusted OR per 30 minutes increase in time = 0.89, 95% CI = 0.84-0.94), a lower chance of modified Thrombolysis in Cerebral Infarction (mTICI) grade 2b to 3 reperfusion (adjusted OR per 30 minutes increase in time = 0.93, 95% CI = 0.87-0.98), and an increased probability of symptomatic intracerebral hemorrhage (adjusted OR per 30 minutes increase in time = 1.09, 95% CI = 0.99-1.18). INTERPRETATION: These findings provide a basis for further studies to determine if the functional outcome of patients with stroke can be greatly improved by optimizing IVT to EVT times. ANN NEUROL 2021;89:511-519.

Susceptibility Vessel Sign in Relation With Time From Onset to Magnetic Resonance Imaging.

Background and Purpose: In acute ischemic stroke, the susceptibility vessel sign (SVS) on T2* MR-sequence witnesses the red blood cell content of the clot. Although clot composition strongly depends on its age in vitro, the relationship between SVS and time has not been studied. In this study, we evaluated whether the presence of SVS was related to the time from symptom onset. Methods: We retrospectively analyzed our institutional registry of patients with acute stroke between November 2007 and June 2018. We included patients with an ischemic stroke confirmed by diffusion-weighted imaging magnetic resonance imaging within 8 hours from symptom onset caused by M1 or M2 occlusion and with interpretable T2*-weighted images. We compared clinical and imaging variables among SVS+ and SVS− patients. Time from onset was split into tertiles. Independent markers of SVS+ were identified using multivariable logistic regression. The probability of being SVS+ given time from symptoms onset was modeled using Probit regression. Results: Among the 608 patients included, 433 (71.2%) were SVS+. The odds of being SVS+ increased with time from symptom onset (P trend=0.005). In the multivariable analysis, factors independently associated with a SVS+ were symptom onset to magnetic resonance imaging ([130­180 min] odds ratio [OR], 1.62 [95% CI, 1.03­2.53]; [>180 min] OR, 3.14 [95% CI, 1.92­5.12]), type of magnetic resonance imaging-scanner (OR, 2.83 [95% CI, 1.82­4.41]), cardioembolic cause (OR, 1.51 [95% CI, 1.02­2.24]), and baseline National Institutes of Health Stroke Scale (OR, 1.05 [95% CI, 1.01­1.08]). The probability of being SVS+ increased with time from symptom onset (P=0.004): around 60% at 1 hour, 70% at 3 hours, 80% at 6 hours, and 90% at 8 hours. Conclusions: In acute ischemic stroke, the presence of SVS depends on time from onset to imaging.

Thrombectomy Complications in Large Vessel Occlusions: Incidence, Predictors, and Clinical Impact in the ETIS Registry.

BACKGROUND AND PURPOSE: Procedural complications in thrombectomy for large vessel occlusions of the anterior circulation are not well described. We investigated the incidence, risk factors, and clinical implications of thrombectomy complications in daily clinical practice. METHODS: We used data from the ongoing prospective multicenter observational Endovascular Treatment in Ischemic Stroke Registry in France. The present study is a retrospective analysis of 4029 stroke patients with anterior large vessel occlusions treated with thrombectomy between January 2015 and May 2020 in 18 centers. We systematically collected procedural data, incidence of embolic complications, perforations and dissections, clinical outcome at 90 days, and hemorrhagic complications. RESULTS: Procedural complications occurred in 7.99% (95% CI, 7.17%-8.87%), and embolus to a new territory (ENT) was the most frequent (5.2%). Predictors of ENTs were terminal carotid/tandem occlusion (odds ratio [OR], 5 [95% CI, 2.03-12.31]; P<0.001) and an increased total number of passes (OR, 1.22 [95% CI, 1.05-1.41]; P=0.006). ENTs were associated to worse clinical outcomes (90-day modified Rankin Scale score, 0-2; adjusted OR, 0.4 [95% CI, 0.25-0.63]; P<0.001), increased mortality (adjusted OR, 1.74 [95% CI, 1.2-2.53]; P<0.001), and symptomatic intracerebral hemorrhage (adjusted OR, 1.87 [95% CI, 1.15-3.03]; P=0.011). Perforations occurred in 1.69% (95% CI, 1.31%-2.13%). Predictors of perforations were terminal carotid/tandem occlusions (39.7% versus 27.6%; P=0.028). 40.7% of patients died at 90 days, and the overall rate of poor outcome was 74.6% in case of perforation. Dissections occurred in 1.46% (95% CI, 1.11%-1.88%) and were more common in younger patients (median age, 64.2 versus 70.2 years; P=0.002). Dissections did not affect the clinical outcome at 90 days. Besides dissection, complications were independent of the thrombectomy technique. CONCLUSIONS: Thrombectomy complication rate is not negligible, and ENTs were the most frequent. ENTs and perforations were associated with disability and mortality, and terminal carotid/tandem occlusions were a risk factor. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03776877.

Prediction of disease activity in models of multiple sclerosis by molecular magnetic resonance imaging of P-selectin.

New strategies for detecting disease activity in multiple sclerosis are being investigated to ameliorate diagnosis and follow-up of patients. Today, although magnetic resonance imaging (MRI) is widely used to diagnose and monitor multiple sclerosis, no imaging tools exist to predict the evolution of disease and the efficacy of therapeutic strategies. Here, we show that molecular MRI targeting the endothelial adhesion molecule P-selectin unmasks the pathological events that take place in the spinal cord of mice subjected to chronic or relapsing experimental autoimmune encephalomyelitis. This approach provides a quantitative spatiotemporal follow-up of disease course in relation to clinical manifestations. Moreover, it predicts relapse in asymptomatic mice and remission in symptomatic animals. Future molecular MRI targeting P-selectin may be used to improve diagnosis, follow-up of treatment, and management of relapse/remission cycles in multiple sclerosis patients by providing information currently inaccessible through conventional MRI techniques.

Potent Thrombolytic Effect of N-Acetylcysteine on Arterial Thrombi.

BACKGROUND: Platelet cross-linking during arterial thrombosis involves von Willebrand Factor (VWF) multimers. Therefore, proteolysis of VWF appears promising to disaggregate platelet-rich thrombi and restore vessel patency in acute thrombotic disorders such as ischemic stroke, acute coronary syndrome, or acute limb ischemia. N-Acetylcysteine (NAC, a clinically approved mucolytic drug) can reduce intrachain disulfide bonds in large polymeric proteins. In the present study, we postulated that NAC might cleave the VWF multimers inside occlusive thrombi, thereby leading to their dissolution and arterial recanalization. METHODS: Experimental models of thrombotic stroke induced by either intra-arterial thrombin injection or ferric chloride application followed by measurement of cerebral blood flow using a combination of laser Doppler flowmetry and MRI were performed to uncover the effects of NAC on arterial thrombi. To investigate the effect of NAC on larger vessels, we also performed ferric chloride-induced carotid artery thrombosis. In vitro experiments were performed to study the molecular bases of NAC thrombolytic effect, including platelet aggregometry, platelet-rich thrombi lysis assays, thromboelastography (ROTEM), and high-shear VWF string formation using microfluidic devices. We also investigated the putative prohemorrhagic effect of NAC in a mouse model of intracranial hemorrhage induced by in situ collagenase type VII injection. RESULTS: We demonstrated that intravenous NAC administration promotes lysis of arterial thrombi that are resistant to conventional approaches such as recombinant tissue-type plasminogen activator, direct thrombin inhibitors, and antiplatelet treatments. Through in vitro and in vivo experiments, we provide evidence that the molecular target underlying the thrombolytic effects of NAC is principally the VWF that cross-link platelets in arterial thrombi. Coadministration of NAC and a nonpeptidic GpIIb/IIIa inhibitor further improved its thrombolytic efficacy, essentially by accelerating thrombus dissolution and preventing rethrombosis. Thus, in a new large-vessel thromboembolic stroke model in mice, this cotreatment significantly improved ischemic lesion size and neurological outcome. It is important to note that NAC did not worsen hemorrhagic stroke outcome, suggesting that it exerts thrombolytic effects without significantly impairing normal hemostasis. CONCLUSIONS: We provide evidence that NAC is an effective and safe alternative to currently available antithrombotic agents to restore vessel patency after arterial occlusion.

Ischemia-Reperfusion Injury After Endovascular Thrombectomy for Ischemic Stroke.

Background and Purpose- In experimental models of ischemic stroke, abrupt reperfusion is associated with secondary brain damages, responsible for up to 70% of the final lesion size. Whether this remains true in humans is unknown. Methods- Using data from the ASTER randomized trial (Aspiration vs Stent Retriever for Successful Revascularization), we investigated the effect of complete reperfusion (defined as a modified Thrombolysis In Cerebral Infarction 3) after endovascular thrombectomy on early lesion growth as assessed by diffusion-weighted imaging at baseline and 1 day after reperfusion. Results- Among 381 patients included in the trial, 35 achieved complete reperfusion, benefited from both baseline and day 1 diffusion-weighted imaging, lacked significant hemorrhagic transformation, and were, therefore, included in the present study. We found that the median growth of the ischemic lesion between baseline and day 1 was only 0.9 mL after complete reperfusion, representing <4% of the mean lesion size. The actual lesion growth occurring after reperfusion is probably even smaller because this lesion growth occurred, at least in part, between baseline imaging and complete reperfusion, as demonstrated by a statistically significant positive correlation between imaging-to-reperfusion time and lesion growth ( R2=0.116; P=0.048). Conclusions- There is no significant lesion growth after complete reperfusion in most patients. This important discrepancy between clinical and preclinical pathophysiologies should be considered during preclinical evaluation of neuroprotective strategies.

Hyperfibrinolysis increases blood-brain barrier permeability by a plasmin- and bradykinin-dependent mechanism.

Hyperfibrinolysis is a systemic condition occurring in various clinical disorders such as trauma, liver cirrhosis, and leukemia. Apart from increased bleeding tendency, the pathophysiological consequences of hyperfibrinolysis remain largely unknown. Our aim was to develop an experimental model of hyperfibrinolysis and to study its effects on the homeostasis of the blood-brain barrier (BBB). We induced a sustained hyperfibrinolytic state in mice by hydrodynamic transfection of a plasmid encoding for tissue-type plasminogen activator (tPA). As revealed by near-infrared fluorescence imaging, hyperfibrinolytic mice presented a significant increase in BBB permeability. Using a set of deletion variants of tPA and pharmacological approaches, we demonstrated that this effect was independent of N-methyl-D-aspartate receptor, low-density lipoprotein-related protein, protease-activated receptor-1, or matrix metalloproteinases. In contrast, we provide evidence that hyperfibrinolysis-induced BBB leakage is dependent on plasmin-mediated generation of bradykinin and subsequent activation of bradykinin B2 receptors. Accordingly, this effect was prevented by icatibant, a clinically available B2 receptor antagonist. In agreement with these preclinical data, bradykinin generation was also observed in humans in a context of acute pharmacological hyperfibrinolysis. Altogether, these results suggest that B2 receptor blockade may be a promising strategy to prevent the deleterious effects of hyperfibrinolysis on the homeostasis of the BBB.

Molecular magnetic resonance imaging discloses endothelial activation after transient ischaemic attack.

SEE SUN ET AL DOI101093/AWW306 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: About 20% of patients with ischaemic stroke have a preceding transient ischaemic attack, which is clinically defined as focal neurological symptoms of ischaemic origin resolving spontaneously. Failure to diagnose transient ischaemic attack is a wasted opportunity to prevent recurrent disabling stroke. Unfortunately, diagnosis can be difficult, due to numerous mimics, and to the absence of a specific test. New diagnostic tools are thus needed, in particular for radiologically silent cases, which correspond to the recommended tissue-based definition of transient ischaemic attack. As endothelial activation is a hallmark of cerebrovascular events, we postulated that this may also be true for transient ischaemic attack, and that it would be clinically relevant to develop non-invasive in vivo imaging to detect this endothelial activation. Using transcriptional and immunohistological analyses for adhesion molecules in a mouse model, we identified brain endothelial P-selectin as a potential biomarker for transient ischaemic attack. We thus developed ultra-sensitive molecular magnetic resonance imaging using antibody-based microparticles of iron oxide targeting P-selectin. This highly sensitive imaging strategy unmasked activated endothelial cells after experimental transient ischaemic attack and allowed discriminating transient ischaemic attack from epilepsy and migraine, two important transient ischaemic attack mimics. We provide preclinical evidence that combining conventional magnetic resonance imaging with molecular magnetic resonance imaging targeting P-selectin might aid in the diagnosis of transient ischaemic attack.

Subarachnoid Hemorrhage Severely Impairs Brain Parenchymal Cerebrospinal Fluid Circulation in Nonhuman Primate.

BACKGROUND AND PURPOSE: Subarachnoid hemorrhage (SAH) is a devastating form of stroke with neurological outcomes dependent on the occurrence of delayed cerebral ischemia. It has been shown in rodents that some of the mechanisms leading to delayed cerebral ischemia are related to a decreased circulation of the cerebrospinal fluid (CSF) within the brain parenchyma. Here, we evaluated the cerebral circulation of the CSF in a nonhuman primate in physiological condition and after SAH. METHODS: We first evaluated in physiological condition the circulation of the brain CSF in Macacafacicularis, using magnetic resonance imaging of the temporal DOTA-Gd distribution after its injection into the CSF. Then, animals were subjected to a minimally invasive SAH before an MRI evaluation of the impact of SAH on the brain parenchymal CSF circulation. RESULTS: We first demonstrate that the CSF actively penetrates the brain parenchyma. Two hours after injection, almost the entire brain is labeled by DOTA-Gd. We also show that our model of SAH in nonhuman primate displays the characteristics of SAH in humans and leads to a dramatic impairment of the brain parenchymal circulation of the CSF. CONCLUSIONS: The CSF actively penetrates within the brain parenchyma in the gyrencephalic brain, as described for the glymphatic system in rodent. This parenchymal CSF circulation is severely impaired by SAH.

Vascular Tissue-Type Plasminogen Activator Promotes Intracranial Aneurysm Formation.

BACKGROUND AND PURPOSE: Although the mechanisms that contribute to intracranial aneurysm (IA) formation and rupture are not totally elucidated, inflammation and matrix remodeling are incriminated. Because tPA (tissue-type plasminogen activator) controls both inflammatory and matrix remodeling processes, we hypothesized that tPA could be involved in the pathophysiology of IA. METHODS: Immunofluorescence analyses of tPA and its main substrate within the aneurysmal wall of murine and human samples were performed. We then compared the formation and rupture of IAs in wild-type, tPA-deficient and type 1 plasminogen activator inhibitor-deficient mice subjected to a model of elastase-induced IA. The specific contribution of vascular versus global tPA was investigated by performing hepatic hydrodynamic transfection of a cDNA encoding for tPA in tPA-deficient mice. The formation and rupture of IAs were monitored by magnetic resonance imaging tracking for 28 days. RESULTS: Immunofluorescence revealed increased expression of tPA within the aneurysmal wall. The number of aneurysms and their symptomatic ruptures were significantly lower in tPA-deficient than in wild-type mice. Conversely, they were higher in plasminogen activator inhibitor-deficient mice. The wild-type phenotype could be restored in tPA-deficient mice by selectively increasing circulating levels of tPA via hepatic hydrodynamic transfection of a cDNA encoding for tPA. CONCLUSIONS: Altogether, this preclinical study demonstrates that the tPA present in the blood stream is a key player of the formation of IAs. Thus, tPA should be considered as a possible new target for the prevention of IAs formation and rupture.

Efficacy of Alteplase in a Mouse Model of Acute Ischemic Stroke: A Retrospective Pooled Analysis.

BACKGROUND AND PURPOSE: The debate over the fact that experimental drugs proposed for the treatment of stroke fail in the translation to the clinical situation has attracted considerable attention in the literature. In this context, we present a retrospective pooled analysis of a large data set from preclinical studies, to examine the effects of early versus late administration of intravenous recombinant tissue-type plasminogen activator. METHODS: We collected data from 26 individual studies from 9 international centers (13 researchers; 716 animals) that compared recombinant tissue-type plasminogen activator with controls, in a unique mouse model of thromboembolic stroke induced by an in situ injection of thrombin into the middle cerebral artery. Studies were classified into early (<3 hours) versus late (≥3 hours) drug administration. Final infarct volumes, assessed by histology or magnetic resonance imaging, were compared in each study, and the absolute differences were pooled in a random-effect meta-analysis. The influence of time of administration was tested. RESULTS: When compared with saline controls, early recombinant tissue-type plasminogen activator administration was associated with a significant benefit (absolute difference, -6.63 mm(3); 95% confidence interval, -9.08 to -4.17; I(2)=76%), whereas late recombinant tissue-type plasminogen activator treatment showed a deleterious effect (+5.06 mm(3); 95% confidence interval, +2.78 to +7.34; I(2)=42%; Pint<0.00001). Results remained unchanged after subgroup analyses. CONCLUSIONS: Our results provide the basis needed for the design of future preclinical studies on recanalization therapies using this model of thromboembolic stroke in mice. The power analysis reveals that a multicenter trial would require 123 animals per group instead of 40 for a single-center trial.

GpIbα-VWF blockade restores vessel patency by dissolving platelet aggregates formed under very high shear rate in mice.

Interactions between platelet glycoprotein (Gp) IIb/IIIa and plasma proteins mediate platelet cross-linking in arterial thrombi. However, GpIIb/IIIa inhibitors fail to disperse platelet aggregates after myocardial infarction or ischemic stroke. These results suggest that stability of occlusive thrombi involves additional and as-yet-unidentified mechanisms. In the present study, we investigated the mechanisms driving platelet cross-linking during occlusive thrombus formation. Using computational fluid dynamic simulations and in vivo thrombosis models, we demonstrated that the inner structure of occlusive thrombi is heterogeneous and primarily determined by the rheological conditions that prevailed during thrombus growth. Unlike the first steps of thrombus formation, which are GpIIb/IIIa-dependent, our findings reveal that closure of the arterial lumen is mediated by GpIbα-von Willebrand Factor (VWF) interactions. Accordingly, disruption of platelet cross-linking using GpIbα-VWF inhibitors restored vessel patency and improved outcome in a mouse model of ischemic stroke, although the thrombi were resistant to fibrinolysis or traditional antithrombotic agents. Overall, our study demonstrates that disruption of GpIbα-VWF interactions restores vessel patency after occlusive thrombosis by specifically disaggregating the external layer of occlusive thrombi, which is constituted of platelet aggregates formed under very high shear rates.

Impact of alcohol consumption on the outcome of ischemic stroke and thrombolysis: role of the hepatic clearance of tissue-type plasminogen activator.

BACKGROUND AND PURPOSE: Tissue-type plasminogen activator (tPA) is the only acute treatment for ischemic stroke. Unfortunately, the benefit of tPA-driven thrombolysis is not systematic, and understanding the reasons for this is mandatory. The balance between beneficial and detrimental effects of tPA might explain the limited overall efficiency of thrombolysis. Here, we investigated whether this balance could be influenced by excessive alcohol intake. METHODS: We used a murine model of thromboembolic stroke, coupled to an array of biochemical assays, near-infrared or magnetic resonance imaging scans, 2-photon microscopy, hydrodynamic transfections, and immunohistological techniques. RESULTS: We found that 6 weeks of alcohol consumption (10% in drinking water) worsens ischemic lesions and cancels the beneficial effects of tPA-induced thrombolysis. We accumulate in vivo and in vitro evidence showing that this aggravation is correlated with a decrease in lipoprotein receptor-related protein 1-mediated hepatic clearance of tPA in alcohol-exposed mice. CONCLUSIONS: An efficient liver-driven clearance of tPA might influence the safety of thrombolysis after stroke.

Impaired glymphatic perfusion after strokes revealed by contrast-enhanced MRI: a new target for fibrinolysis?

BACKGROUND AND PURPOSE: The aim of the present study was to investigate the impact of different stroke subtypes on the glymphatic system using MRI. METHODS: We first improved and characterized an in vivo protocol to measure the perfusion of the glymphatic system using MRI after minimally invasive injection of a gadolinium chelate within the cisterna magna. Then, the integrity of the glymphatic system was evaluated in 4 stroke models in mice including subarachnoid hemorrhage (SAH), intracerebral hemorrhage, carotid ligature, and embolic ischemic stroke. RESULTS: We were able to reliably evaluate the glymphatic system function using MRI. Moreover, we provided evidence that the glymphatic system was severely impaired after SAH and in the acute phase of ischemic stroke, but was not altered after carotid ligature or in case of intracerebral hemorrhage. Notably, this alteration in glymphatic perfusion reduced brain clearance rate of low-molecular-weight compounds. Interestingly, glymphatic perfusion after SAH can be improved by intracerebroventricular injection of tissue-type plasminogen activator. Moreover, spontaneous arterial recanalization was associated with restoration of the glymphatic function after embolic ischemic stroke. CONCLUSIONS: SAH and acute ischemic stroke significantly impair the glymphatic system perfusion. In these contexts, injection of tissue-type plasminogen activator either intracerebroventricularly to clear perivascular spaces (for SAH) or intravenously to restore arterial patency (for ischemic stroke) may improve glymphatic function.

tPA promotes ADAMTS-4-induced CSPG degradation, thereby enhancing neuroplasticity following spinal cord injury.

Although tissue plasminogen activator (tPA) is known to promote neuronal remodeling in the CNS, no mechanism of how this plastic function takes place has been reported so far. We provide here in vitro and in vivo demonstrations that this serine protease neutralizes inhibitory chondroitin sulfate proteoglycans (CSPGs) by promoting their degradation via the direct activation of endogenous type 4 disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS-4). Accordingly, in a model of compression-induced spinal cord injury (SCI) in rats, we found that administration of either tPA or its downstream effector ADAMTS-4 restores the tPA-dependent activity lost after the SCI and thereby, reduces content of CSPGs in the spinal cord, a cascade of events leading to an improved axonal regeneration/sprouting and eventually long term functional recovery. This is the first study to reveal a tPA-ADAMTS-4 axis and its function in the CNS. It also raises the prospect of exploiting such cooperation as a therapeutic tool for enhancing recovery after acute CNS injuries.

MRI-based microthrombi detection in stroke with polydopamine iron oxide.

In acute ischemic stroke, even when successful recanalization is obtained, downstream microcirculation may still be obstructed by microvascular thrombosis, which is associated with compromised brain reperfusion and cognitive decline. Identifying these microthrombi through non-invasive methods remains challenging. We developed the PHySIOMIC (Polydopamine Hybridized Self-assembled Iron Oxide Mussel Inspired Clusters), a MRI-based contrast agent that unmasks these microthrombi. In a mouse model of thromboembolic ischemic stroke, our findings demonstrate that the PHySIOMIC generate a distinct hypointense signal on T2*-weighted MRI in the presence of microthrombi, that correlates with the lesion areas observed 24 hours post-stroke. Our microfluidic studies reveal the role of fibrinogen in the protein corona for the thrombosis targeting properties. Finally, we observe the biodegradation and biocompatibility of these particles. This work demonstrates that the PHySIOMIC particles offer an innovative and valuable tool for non-invasive in vivo diagnosis and monitoring of microthrombi, using MRI during ischemic stroke.