Downstream Microvascular Thrombosis in Cortical Venules Is an Early Response to Proximal Cerebral Arterial Occlusion

The benefit of favorable venous outflow profile is mediated through reduced microvascular dysfunction in acute ischemic stroke

INTRODUCTIONS

Venous outflow (VO) is emerging as a marker of microvascular integrity in acute ischemic stroke. Using hemorrhagic transformation (HT) and infarct growth as mediators, we tested whether a favorable VO profile benefited functional outcome by reducing consequences of microvascular dysfunction.

PATIENTS AND METHODS

Patients receiving thrombectomy in three comprehensive stroke centers due to acute anterior circulation occlusion were included. VO was assessed semi-quantitatively by the opacification of ipsilateral vein of Labbé, Trolard and superficial middle cerebral vein. HT was graded on follow-up CT. Infarct growth volume (IGV) was the difference of final infarct volume and baseline core volume. The association of VO and functional independence (90-day modified Rankin Scale ⩽ 2) was examined by logistic regression. Mediation analysis was performed among VO, HT or IGV, and functional outcome in patients with or without recanalization, respectively.

RESULTS

In 242 patients analyzed, VO was strongly correlated with functional independence and VO ⩾ 4 was defined favorable. In 175 patients recanalized, favorable VO was associated with a reduced risk of HT (OR = 0.82, 95% CI 0.71-0.95, p = 0.008), which accounted for 13.1% of the association between VO and favorable outcome. In 67 patients without recanalization, favorable VO was associated with decreased IGV (β = -0.07, 95% CI -0.11 to -0.02, p = 0.007). The association of favorable VO and functional independence was no longer significant (aOR = 4.84, 95% CI 0.87-38.87, p = 0.089) after including IGV in the model, suggesting a complete mediation.

DISCUSSION AND CONCLUSION

In patients with acute anterior large vessel occlusion, the clinical benefit of VO may be mediated through reduced microvascular dysfunction.

Acute Ischemic Stroke in the Clinic and the Laboratory: Targets for Translational Research

Ischemic stroke research has enabled significant advancements in diagnosis, treatment, and management of this debilitating disease, yet challenges remain standing in the way of better patient prognoses. In this narrative review, a fictional case illustrates challenges and uncertainties that medical professionals still face - penumbra identification, lack of neuroprotective agents, side-effects of tissue plasminogen activator, dearth of molecular biomarkers, incomplete microvascular reperfusion or no-reflow, post-recanalization hyperperfusion, blood pressure management and procedural anesthetic effects. The current state of the field is broadly reviewed per topic, with the aim to introduce a broad audience (scientist and clinician alike) to recent successes in translational stroke research and pending scientific queries that are tractable for preclinical assessment. Opportunities for co-operation between clinical and experimental stroke experts are highlighted to increase the size and frequency of strides the field makes to improve our understanding of this disease and ways of treating it.

Hemorrhagic cerebral venous infarction after vein injury during intraoperative lesion resection: incidence, hemorrhagic stages, risk factors and prognosis

Objective

Cerebral venous infarction (CVI) after vein injury during intraoperative lesion resection is associated with intracranial hemorrhage. We conducted this study to identify the incidence, clinical and imaging features, and prognosis of hemorrhage CVI.

Methods

We performed a retrospective analysis of patients with confirmed CVI after vein injury who underwent craniotomy in our hospital. Postoperative clinical symptoms were observed, and imaging features were compared between patients with and without intracranial hemorrhages through CT examination. Variables were analyzed using univariate and multivariate regression analyses.

Results

Among 2,767 patients who underwent craniotomy, 93 cases of injured veins were identified intraoperatively. Hemorrhagic CVI was found in 38% (35/93). Multivariate analysis revealed that midline approach, meningioma, postoperative seizures, disorders of consciousness and interval in hours < 72 h were identified as predictors of hemorrhagic CVI. After 3 months of follow-up, the prognosis was poor in 15 cases (16%, 15/93), including death (two cases), vegetative survival (four cases), and severe disability (nine cases).

Conclusions

Hemorrhagic CVI, as a critical complication after venous injury, can have disastrous consequences. Do not injure known veins intraoperatively. In case of injury, requisite remedial measures should be adopted during and after surgery.

Intravenous Thrombolysis before Complete Angiographic Reperfusion: Beyond Angiographic Assessment to Target Microvascular Obstruction?

OBJECTIVE

Recent data have suggested that ineffective tissue reperfusion despite successful angiographic reperfusion was partly responsible for unfavorable outcomes after endovascular therapy (EVT) and might be modulated by intravenous thrombolysis (IVT) use before EVT. To specifically decipher the effect played by IVT before EVT, we compared the clinical and safety outcomes of patients who experienced a complete reperfusion at the end of EVT according to IVT use before EVT.

METHODS

The Endovascular Treatment in Ischemic Stroke (ETIS) registry is an ongoing, prospective, observational study at 21 centers that perform EVT in France. Patients were included if they had an anterior large vessel occlusion of the intracranial internal carotid artery or middle cerebral artery (M1/M2 segments) and complete reperfusion (expanded Thrombolysis in Cerebral Infarction score = 3) with EVT within 6 hours, between January 2015 and December 2021. The cohort was divided into two groups according to IVT use before EVT, and propensity score matching (PSM) was used to balance the two groups. Primary outcome was the shift in the degree of disability as measured by the modified Rankin Scale (mRS) at 90 days. Secondary outcomes included favorable outcome (mRS 0-2) at 90 days. Safety outcomes included symptomatic intracranial hemorrhage and 90-day mortality. Outcomes were estimated with multivariate logistic models adjusted for age, National Institutes of Health Stroke Scale, Alberta Stroke Program Early CT Score, and time from symptom onset to puncture.

RESULTS

Among 5,429 patients included in the ETIS registry, 1,093 were included in the study, including 651 patients with complete recanalization treated with IVT before EVT. After PSM, 488 patients treated with IVT before EVT were compared to 337 patients without IVT. In the matched cohort analysis, the IVT+EVT group had a favorable shift in the overall mRS score distribution (adjusted odds ratio [aOR] = 1.41, 95% confidence interval [CI] = 1.04-1.91, p = 0.023) and higher rates of favorable outcome (61.1% vs 48.7%, aOR = 1.49, 95% CI = 1.02-2.20, p = 0.041) at 90 days compared with the EVT alone group. Rates of symptomatic intracerebral hemorrhage were comparable between both groups (6.0% vs 4.3%, aOR = 1.16, 95% CI = 0.53-2.54, p = 0.709).

INTERPRETATION

In clinical practice, even after complete angiographic reperfusion by EVT, prior IVT use improves clinical outcomes of patients without increasing bleeding risk. ANN NEUROL 2024;95:762-773.

Pretreatment with a dual antiplatelet and anticoagulant (APAC) reduces ischemia-reperfusion injury in a mouse model of temporary middle cerebral artery occlusion-implications for neurovascular procedures

BACKGROUND

Several neurovascular procedures require temporary occlusion of cerebral arteries, leading to ischemia of unpredictable length, occasionally causing brain infarction. Experimental models of cerebral ischemia-reperfusion injury have established that platelet adhesion and coagulation play detrimental roles in reperfusion injury following transient cerebral ischemia. Therefore, in a model of cerebral ischemia-reperfusion injury (IRI), we investigated the therapeutic potential of a dual antiplatelet and anticoagulant (APAC) heparin proteoglycan mimetic which is able to bind to vascular injury sites.

METHODS

Brain ischemia was induced in mice by transient occlusion of the right middle cerebral artery for 60 min. APAC, unfractionated heparin (UFH) (both at heparin equivalent doses of 0.5 mg/kg), or vehicle was intravenously administered 10 min before or 60 min after the start of ischemia. At 24 h later, mice were scored for their neurological and motor behavior, and brain damage was quantified.

RESULTS

Both APAC and UFH administered before the onset of ischemia reduced brain injury. APAC and UFH pretreated mice had better neurological and motor functions (p < 0.05 and p < 0.01, respectively) and had significantly reduced cerebral infarct sizes (p < 0.01 and p < 0.001, respectively) at 24 h after transient occlusion compared with vehicle-treated mice. Importantly, no macroscopic bleeding complications were observed in either APAC- or UFH-treated animals. However, when APAC or UFH was administered 60 min after the start of ischemia, the therapeutic effect was lost, but without hemorrhaging either.

CONCLUSIONS

Pretreatment with APAC or UFH was safe and effective in reducing brain injury in a model of cerebral ischemia induced by transient middle cerebral artery occlusion. Further studies on the use of APAC to limit ischemic injury during temporary occlusion in neurovascular procedures are indicated.

Safety and efficacy of platelet glycoprotein VI inhibition in acute ischaemic stroke (ACTIMIS): a randomised, double-blind, placebo-controlled, phase 1b/2a trial

BACKGROUND

Antagonists of glycoprotein VI-triggered platelet activation used in combination with recanalisation therapies are a promising therapeutic approach in acute ischaemic stroke. Glenzocimab is an antibody fragment that inhibits the action of platelet glycoprotein VI. We aimed to determine and assess the safety and efficacy of the optimal dose of glenzocimab in patients with acute ischaemic stroke eligible to receive alteplase with or without mechanical thrombectomy.

METHODS

This randomised, double-blind, placebo-controlled study with dose-escalation (1b) and dose-confirmation (2a) phases (ACTIMIS) was done in 26 stroke centres in six European countries. Participants were adults (≥18 years) with disabling acute ischaemic stroke with a National Institutes of Health Stroke Scale score of 6 or higher before alteplase administration. Patients were randomly assigned treatment using a central electronic procedure. Total administered dose at the end of the intravenous administration was 125 mg, 250 mg, 500 mg, and 1000 mg of glenzocimab or placebo in phase 1b and 1000 mg of glenzocimab or placebo in phase 2a. Treatment was initiated 4·5 h or earlier from stroke symptom onset in patients treated with alteplase with or without mechanical thrombectomy. The sponsor, study investigator and study staff, patients, and central laboratories were all masked to study treatment until database lock. Primary endpoints across both phases were safety, mortality, and intracranial haemorrhage (symptomatic, total, and fatal), assessed in all patients who received at least a partial dose of study medication (safety set). The trial is registered on ClinicalTrials.gov, NCT03803007, and is complete.

FINDINGS

Between March 6, 2019, and June 27, 2021, 60 recruited patients were randomly assigned to 125 mg, 250 mg, 500 mg, or 1000 mg glenzocimab, or to placebo in phase 1b (n=12 per group) and were included in the safety analysis. Glenzocimab 1000 mg was well tolerated and selected as the phase 2a recommended dose; from Oct 2, 2020, to June 27, 2021, 106 patients were randomly assigned to glenzocimab 1000 mg (n=53) or placebo (n=53). One patient in the placebo group received glenzocimab in error and therefore 54 and 52, respectively, were included in the safety set. In phase 2a, the most frequent treatment-emergent adverse event was non-symptomatic haemorrhagic transformation, which occurred in 17 (31%) of 54 patients treated with glenzocimab and 26 (50%) of 52 patients treated with placebo. Symptomatic intracranial haemorrhage occurred in no patients treated with glenzocimab compared with five (10%) patients in the placebo group. All-cause deaths were lower with glenzocimab 1000 mg (four [7%] patients) than with placebo (11 [21%] patients).

INTERPRETATION

Glenzocimab 1000 mg in addition to alteplase, with or without mechanical thrombectomy, was well tolerated, and might reduce serious adverse events, intracranial haemorrhage, and mortality. These findings support the need for future research into the potential therapeutic inhibition of glycoprotein VI with glenzocimab plus alteplase in patients with acute ischaemic stroke.

FUNDING

Acticor Biotech.

Progressive microvascular failure in acute ischemic stroke: A systematic review, meta-analysis, and time-course analysis

This systematic review, meta-analysis, and novel time course analysis examines microvascular failure in the treatment of acute ischemic stroke (AIS) patients undergoing endovascular therapy (EVT) and/or thrombolytic administration for stroke management. A systematic review and meta-analysis following PRIMSA-2020 guidelines was conducted along with a novel curve-of-best fit analysis to elucidate the time-course of microvascular failure. Scopus and PubMed were searched using relevant keywords to identify studies that examine recanalization and reperfusion assessment of AIS patients following large vessel occlusion. Meta-analysis was conducted using a random-effects model. Curve-of-best-fit analysis of microvascular failure rate was performed with a negative exponential model. Twenty-seven studies with 1151 patients were included. Fourteen studies evaluated patients within a standard stroke onset-to-treatment time window (≤6 hours after last known normal) and thirteen studies had an extended time window (>6 hours). Our analysis yields a 22% event rate of microvascular failure following successful recanalization (95% CI: 16-30%). A negative exponential curve modeled a microvascular failure rate asymptote of 28.5% for standard time window studies, with no convergence of the model for extended time window studies. Progressive microvascular failure is a phenomenon that is increasingly identified in clinical studies of AIS patients undergoing revascularization treatment.

Neutrophil activation in patients treated with endovascular therapy is associated with unfavorable outcomes and mitigated by intravenous thrombolysis

BACKGROUND

Accumulating evidence indicates that neutrophil activation (NA) contributes to microvascular thromboinflammation in acute ischemic stroke (AIS) due to a large vessel occlusion. Preclinical data have suggested that intravenous thrombolysis (IVT) before endovascular therapy (EVT) could dampen microvascular thromboinflammation. In this study we investigated the association between NA dynamics and stroke outcome, and the impact of IVT on NA in patients with AIS treated with EVT.

METHODS

A single-center prospective study was carried out, including patients treated with EVT for whom three blood samples (before, within 1 hour, 24 hours post-EVT) were drawn to measure plasma myeloperoxidase (MPO) concentration as a marker of NA. Unfavorable outcome was defined as a modified Rankin score of 3-6 at 3 months.

RESULTS

Between 2016 and 2020, 179 patients were included. The plasma MPO concentration peaked significantly 1 hour post-EVT (median increase 21.0 ng/mL (IQR -2.1-150)) and returned to pre-EVT baseline values 24 hours after EVT (median change from baseline -0.8 ng/mL (IQR -7.6-6.7)). This peak was strongly associated with unfavorable outcomes at 3 months (aOR 0.53 (95% CI 0.34 to 0.84), P=0.007). IVT before EVT abolished this 1 hour post-EVT MPO peak. Changes in plasma MPO concentration (baseline to 1 hour post-EVT) were associated with unfavorable outcomes only in patients not treated with IVT before EVT (aOR 0.54 (95% CI 0.33 to 0.88, P=0.013). However, we found no significant heterogeneity in the associations between changes in plasma MPO concentration and outcomes.

CONCLUSIONS

A peak in plasma MPO concentration occurs early after EVT and is associated with unfavorable outcomes. IVT abolished the post-EVT MPO peak and may modulate the association between NA and outcomes.

Incidence, severity and impact on functional outcome of persistent hypoperfusion despite large-vessel recanalization, a potential marker of impaired microvascular reperfusion: Systematic review of the clinical literature

The reported incidence of persistent hypoperfusion despite complete recanalization as surrogate for impaired microvascular reperfusion (IMR) has varied widely among clinical studies, possibly due to differences in i) definition of complete recanalization, with only recent Thrombolysis in Cerebral Infarction (TICI) grading schemes allowing distinction between complete (TICI3) and partial recanalization with distal occlusions (TICI2c); ii) operational definition of IMR; and iii) consideration of potential alternative causes for hypoperfusion, notably carotid stenosis, re-occlusion and post-thrombectomy hemorrhage. We performed a systematic review to identify clinical studies that carried out brain perfusion imaging within 72 hrs post-thrombectomy for anterior circulation stroke and reported hypoperfusion rates separately for TICI3 and TICI2c grades. Authors were contacted if this data was missing. We identified eight eligible articles, altogether reporting 636 patients. The incidence of IMR after complete recanalization (i.e., TICI3) tended to decrease with the number of considered alternative causes of hypoperfusion: range 12.5-42.9%, 0-31.6% and 0-9.1% in articles that considered none, two or all three causes, respectively. No study reported the impact of IMR on functional outcome separately for TICI-3 patients. Based on this systematic review, IMR in true complete recanalization appears relatively rare, and reported incidence highly depends on definition used and consideration of confounding factors.

Risk Factors, Pathophysiologic Mechanisms, and Potential Treatment Strategies of Futile Recanalization after Endovascular Therapy in Acute Ischemic Stroke

Endovascular therapy is the first-line treatment for acute ischemic stroke. However, studies have shown that, even with the timely opening of occluded blood vessels, nearly half of all patients treated with endovascular therapy for acute ischemic stroke still have poor functional recovery, a phenomenon called "futile recanalization.". The pathophysiology of futile recanalization is complex and may include tissue no-reflow (microcirculation reperfusion failure despite recanalization of the occluded large artery), early arterial reocclusion (reocclusion of the recanalized artery 24-48 hours post endovascular therapy), poor collateral circulation, hemorrhagic transformation (cerebral bleeding following primary ischemic stroke), impaired cerebrovascular autoregulation, and large hypoperfusion volume. Therapeutic strategies targeting these mechanisms have been attempted in preclinical research; however, translation to the bedside remains to be explored. This review summarizes the risk factors, pathophysiological mechanisms, and targeted therapy strategies of futile recanalization, focusing on the mechanisms and targeted therapy strategies of no-reflow to deepen the understanding of this phenomenon and provide new translational research ideas and potential intervention targets for improving the efficacy of endovascular therapy for acute ischemic stroke.

Thrombectomy with or without Intravenous Thrombolytics in Basilar Artery Occlusion

OBJECTIVE

Two randomized trials demonstrated the benefit of endovascular therapy (EVT) in patients suffering from a stroke due to a basilar artery occlusion (BAO). However, intravenous thrombolytic (IVT) use before EVT was low in these trials, questioning the added value of this treatment in this setting. We sought to investigate the efficacy and safety of EVT alone compared to IVT + EVT in stroke patients with a BAO.

METHODS

We analyzed data from the Endovascular Treatment in Ischemic Stroke registry, a prospective, observational, multicenter study of acute ischemic stroke patients treated with EVT in 21 centers in France between 1 January 2015 and 31 December 2021. We included patients with BAO and/or intracranial vertebral artery occlusion and compared patients treated with EVT alone versus IVT + EVT after propensity score (PS) matching. Variables selected for the PS were pre-stroke mRS, dyslipidemia, diabetes, anticoagulation, admission mode, baseline NIHSS and ASPECTS, type of anesthesia, and time from symptom onset to puncture. Efficacy outcomes were good functional outcome (modified Rankin Scale [mRS] 0-3) and functional independence (mRS 0-2) at 90 days. Safety outcomes were symptomatic intracranial hemorrhages and all-cause mortality at 90 days.

RESULTS

Among 385 patients, 243 (134 EVT alone and 109 IVT + EVT) were included after PS matching. There was no difference between EVT alone and IVT + EVT regarding good functional outcome (adjusted odd ratio [aOR] labeling = 1.27, 95% confidence interval [CI], 0.68-2.37, p = 0.45) and functional independence (aOR = 1.50, 95% CI, 0.79-2.85, p = 0.21). Symptomatic intracranial hemorrhage and all-cause mortality were also similar between the two groups (aOR = 0.42, 95% CI, 0.10-1.79, p = 0.24 and aOR = 0.56, 95% CI, 0.29-1.10, p = 0.09, respectively).

INTERPRETATION

In this PS matching analysis, EVT alone seemed to lead to similar neurological recovery than IVT + EVT, with comparable safety profile. However, given our sample size and the observational nature of this study, further studies are needed to confirm these findings. ANN NEUROL 2023;94:596-604.

No-Reflow Post-Recanalization in Acute Ischemic Stroke: Mechanisms, Measurements, and Molecular Markers

Acute ischemic stroke remains the primary cause of disability worldwide. For patients with large vessel occlusions, intravenous thrombolysis followed by mechanical thrombectomy remains the standard of care. Revascularization of the large vessel is typically successful. However, despite reopening of the occluded vessel, many patients fail to return to independence. Functional failure, despite macrovascular recanalization, is often referred to as the no-reflow phenomenon. Even with an extensive characterization of reperfusion in animal models, numerous mechanisms may explain no-reflow. Further, uniform measurements of this microvascular dysfunction and prognostic markers associated with no-reflow are lacking. In this review, we highlight a number of mechanisms that may explain no-reflow, characterize current multimodal measurements, and assess its molecular markers.

Impaired intracranial venous outflow profiles are associated with poor outcome in stroke after reperfusion therapy: A hypoperfusion-matched intracranial venous scale

PURPOSE

Arterial blood flow provided prognostic information in acute ischemic stroke (AIS). However, part of the patients with favorable arterial blood flow still suffered from poor outcomes after reperfusion therapy. We aimed to verify the hypothesis that intracranial venous outflow profiles (both cortical and deep) within the hypoperfusion area were associated with clinical outcome in AIS patients who received reperfusion therapy.

METHOD

We performed a retrospective analysis of prospectively collected data from anterior circulation AIS patients. All patients underwent pretreatment CTP and received reperfusion therapy. We constructed a 5-point hypoperfusion-matched Intracranial Venous Scale (hypo-IVS) from the sum of the contrast enhancement degree (1, attenuated contrast enhancement; 0, complete contrast enhancement) of 4 typical veins (superficial middle cerebral vein, vein of Labbé, vein of Trolard, and internal cerebral vein) whose outflow territories had matched hypoperfusion. Logistic and ordinal regression were used to analyze the association between hypo-IVS and clinical outcome.

RESULTS

A total of 751 patients were included. Higher Hypo-IVS was significantly associated with poor outcome (3-month mRS of >2; OR = 1.194; 95 % CI: 1.014-1.407; p = 0.033). The adjusted ORs for poor outcome and high 24-hour NIHSS were 1.172 (95 %CI: 1.035-1.328; p = 0.012) and 1.176 (95 %CI: 1.030-1.330; p = 0.010) in ordinal regression, respectively. Hypo-IVS > 2 was an independent risk factor of poor outcome (75.2 % vs 40.8 %; OR = 1.932; 95 %CI: 1.158-3.224; p = 0.012).

CONCLUSIONS

Intracranial venous outflow profiles deliver prognostic information in AIS and the hypo-IVS is a helpful tool to predict clinical outcomes after reperfusion therapy.

A dataset of rodent cerebrovasculature from in vivo multiphoton fluorescence microscopy imaging

We present MiniVess, the first annotated dataset of rodent cerebrovasculature, acquired using two-photon fluorescence microscopy. MiniVess consists of 70 3D image volumes with segmented ground truths. Segmentations were created using traditional image processing operations, a U-Net, and manual proofreading. Code for image preprocessing steps and the U-Net are provided. Supervised machine learning methods have been widely used for automated image processing of biomedical images. While much emphasis has been placed on the development of new network architectures and loss functions, there has been an increased emphasis on the need for publicly available annotated, or segmented, datasets. Annotated datasets are necessary during model training and validation. In particular, datasets that are collected from different labs are necessary to test the generalizability of models. We hope this dataset will be helpful in testing the reliability of machine learning tools for analyzing biomedical images.

Platelet-Neutrophil Crosstalk in Thrombosis

Platelets are essential for the formation of a haemostatic plug to prevent bleeding, while neutrophils are the guardians of our immune defences against invading pathogens. The interplay between platelets and innate immunity, and subsequent triggering of the activation of coagulation is part of the host system to prevent systemic spread of pathogen in the blood stream. Aberrant immunothrombosis and excessive inflammation can however, contribute to the thrombotic burden observed in many cardiovascular diseases. In this review, we highlight how platelets and neutrophils interact with each other and how their crosstalk is central to both arterial and venous thrombosis and in COVID-19. While targeting platelets and coagulation enables efficient antithrombotic treatments, they are often accompanied with a bleeding risk. We also discuss how novel approaches to reduce platelet-mediated recruitment of neutrophils could represent promising therapies to treat thrombosis without affecting haemostasis.

Endothelial caveolin-1 regulates cerebral thrombo-inflammation in acute ischemia/reperfusion injury

BACKGROUND

Thrombo-inflammation is an important checkpoint that orchestrates infarct development in ischemic stroke. However, the underlying mechanism remains largely unknown. Here, we explored the role of endothelial Caveolin-1 (Cav-1) in cerebral thrombo-inflammation.

METHODS

The correlation between serum Cav-1 level and clinical outcome was analyzed in acute ischemic stroke patients with successful recanalization. Genetic manipulations by endothelial-specific adeno-associated virus (AAV) and siRNA were applied to investigate the effects of Cav-1 in thrombo-inflammation in a transient middle cerebral artery occlusion (tMCAO) model. Thrombo-inflammation was analyzed by microthrombosis formation, myeloid cell infiltration, and endothelial expression of adhesion molecules as well as inflammatory factors.

FINDINGS

Reduced circulating Cav-1, with the potential to predict microembolic signals, was more frequently detected in recanalized stroke patients without early neurological improvement. At 24 h after tMCAO, serum Cav-1 was consistently reduced in mice. Endothelial Cav-1 was decreased in the peri-infarct region. Cav-1^-/- endothelium, with prominent barrier disruption, displayed extensive microthrombosis, accompanied by increased myeloid cell inflammatory infiltration after tMCAO. Specific enhanced expression of endothelial Cav-1 by AAV-Tie1-Cav-1 remarkably reduced infarct volume, attenuated vascular hyper-permeability and alleviated thrombo-inflammation in both wild-type and Cav-1^-/- tMCAO mice. Transcriptome analysis after tMCAO further designated Rxrg as the most significantly changed molecule resulting from the knockdown of Cav-1. Supplementation of RXR-γ siRNA reversed AAV-Tie1-Cav-1-induced amelioration of thrombo-inflammation without affecting endothelial tight junction.

INTERPRETATION

Endothelial Cav-1/RXR-γ may regulate infarct volume and neurological impairment, possibly through selectively controlling thrombo-inflammation coupling, in cerebral ischemia/reperfusion.

FUNDING

This work was supported by National Natural Science Foundation of China.

High neutrophil counts before endovascular treatment for acute basilar artery occlusion predict worse outcomes

Background and purpose

Ischemic stroke is related to inflammation. We investigated leukocyte counts, neutrophil counts, and NLR (neutrophil-to-lymphocyte ratio) to explore their prognostic potential and determine if high neutrophil counts before endovascular treatment (EVT) in patients with acute basilar artery occlusion (BAO) are associated with worse outcomes at 90 days post-EVT.

Methods

Leukocyte and neutrophil counts and NLR were determined in eligible patients from the Acute Basilar Artery Occlusion Study (BASILAR). Patients were divided into four groups according to leukocyte and neutrophil counts and NLR quartiles. The primary outcome was a favorable outcome based on the modified Rankin Scale (mRS: 0–3). The secondary outcome was functional independence (mRS 0–2). The safety outcome was mortality, and an unfavorable outcome was mRS 4–6. Successful reperfusion was mTICI (modified Thrombolysis in Cerebral Infarction) of 2b or 3. All the data were collected within 90 days after EVT.

Results

We enrolled 586 patients in the study. The leukocyte and neutrophil counts and NLR were significantly associated with clinical outcomes in all patients though no effects were seen in some intervals. Of these three parameters, the neutrophil count had the most significant impact, negatively affecting the outcome. The findings were similar in patients who were successfully recanalized.

Conclusion

Higher neutrophil counts predicted worse clinical outcomes 90 days after EVT. This finding supports the deleterious role of inflammation in patients with acute BAO despite EVT or successful recanalization.

Intravenous tPA (Tissue-Type Plasminogen Activator) Correlates With Favorable Venous Outflow Profiles in Acute Ischemic Stroke

BACKGROUND

Intravenous tPA (tissue-type plasminogen activator) is often administered before endovascular thrombectomy (EVT). Recent studies have questioned whether tPA is necessary given the high rates of arterial recanalization achieved by EVT, but whether tPA impacts venous outflow (VO) is unknown. We investigated whether tPA improves VO profiles on baseline computed tomography (CT) angiography (CTA) images before EVT.

METHODS

Retrospective multicenter cohort study of patients with acute ischemic stroke due to large vessel occlusion undergoing EVT triage. Included patients underwent CT, CTA, and CT perfusion before EVT. VO profiles were determined by opacification of the vein of Labbé, sphenoparietal sinus, and superficial middle cerebral vein on CTA as 0, not visible; 1, moderate opacification; and 2, full. Pial arterial collaterals were graded on CTA, and tissue-level collaterals were assessed on CT perfusion using the hypoperfusion intensity ratio. Clinical and demographic data were determined from the electronic medical record. Using multivariable regression analysis, we determined the correlation between tPA administration and favorable VO profiles.

RESULTS

Seven hundred seventeen patients met inclusion criteria. Three hundred sixty-five patients received tPA (tPA+), while 352 patients were not treated with tPA (tPA-). Fewer tPA+ patients had atrial fibrillation (n=128 [35%] versus n=156 [44%]; P=0.012) and anticoagulants/antiplatelet treatment before acute ischemic stroke due to large vessel occlusion onset (n=130 [36%] versus n=178 [52%]; P<0.001) compared with tPA- patients. One hundred eighty-five patients (51%) in the tPA+ and 100 patients (28%) in the tPA- group exhibited favorable VO (P<0.001). Multivariable regression analysis showed that tPA administration was a strong independent predictor of favorable VO profiles (OR, 2.6 [95% CI, 1.7-4.0]; P<0.001) after control for favorable pial arterial CTA collaterals, favorable tissue-level collaterals on CT perfusion, age, presentation National Institutes of Health Stroke Scale, antiplatelet/anticoagulant treatment, history of atrial fibrillation and time from symptom onset to imaging.

CONCLUSIONS

In patients with acute ischemic stroke due to large vessel occlusion undergoing thrombectomy triage, tPA administration was strongly associated with the presence of favorable VO profiles.

Impact of COVID-19 on thrombus composition and response to thrombolysis: Insights from a monocentric cohort population of COVID-19 patients with acute ischemic stroke

BACKGROUND

Resistance to fibrinolysis, levels of procoagulant/antifibrinolytic neutrophil extracellular traps (NETs), and the severity of acute ischemic stroke (AIS) are increased by COVID-19. Whether NETs are components of AIS thrombi from COVID-19 patients and whether COVID-19 impacts the susceptibility of these thrombi to thrombolytic treatments remain unknown, however.

OBJECTIVES

We aimed to characterize AIS thrombi from COVID-19 patients by immunohistology and to compare their response to thrombolysis to that of AIS thrombi from non-COVID-19 patients.

PATIENTS/METHODS

For this monocentric cohort study, 14 thrombi from COVID-19 AIS patients and 16 thrombi from non-COVID-19 patients, all recovered by endovascular therapy, were analyzed by immunohistology or subjected to ex vivo thrombolysis by tissue-type plasminogen (tPA)/plasminogen.

RESULTS

COVID-19 AIS thrombi were rich in neutrophils and contained NETs, but not spike protein. Thrombolysis assays revealed a mean resistance profile to tPA/plasminogen of COVID-19 AIS thrombi similar to that of non-COVID-19 AIS thrombi. The addition of DNase 1 successfully improved thrombolysis by potentiating fibrinolysis irrespective of COVID-19 status. Levels of neutrophil, NETs, and platelet markers in lysis supernatants were comparable between AIS thrombi from non-COVID-19 and COVID-19 patients.

CONCLUSIONS

These results show that COVID-19 does not impact NETs content or worsen fibrinolysis resistance of AIS thrombi, a therapeutic hurdle that could be overcome by DNase 1 even in the context of SARS-CoV-2 infection.

Thromboinflammation in Brain Ischemia: Recent Updates and Future Perspectives

Despite decades of promising preclinical validation and clinical translation, ischemic stroke still remains as one of the leading causes of death and disability worldwide. Within its complex pathophysiological signatures, thrombosis and inflammation, that is, thromboinflammation, are highly interconnected processes leading to cerebral vessel occlusion, inflammatory responses, and severe neuronal damage following the ischemic event. Hence, we here review the most recent updates on thromboinflammatory-dependent mediators relevant after stroke focusing on recent discoveries on platelet modulation, a potential regulation of the innate and adaptive immune system in thromboinflammation, utterly providing a thorough up-to-date overview of all therapeutic approaches currently undergoing clinical trial.

Impact of Prior Antiplatelet Therapy on Outcomes After Endovascular Therapy for Acute Stroke: Endovascular Treatment in Ischemic Stroke Registry Results

BACKGROUND AND PURPOSE

The influence of prior antiplatelet therapy (APT) uses on the outcomes of patients with acute ischemic stroke treated with endovascular therapy is unclear. We compared procedural and clinical outcomes of endovascular therapy in patients on APT or not before stroke onset.

METHODS

We analyzed 2 groups from the ongoing prospective multicenter Endovascular Treatment in Ischemic Stroke registry in France: patients on prior APT (APT+) and patients without prior APT (APT-) treated by endovascular therapy, with and without intravenous thrombolysis. Multilevel mixed-effects logistic models including center as random effect were used to compare angiographic (rates of reperfusion at the end of procedure, procedural complications) and clinical (favorable and excellent outcome, 90-day all-cause mortality, and hemorrhagic complications) outcomes according to APT subgroups. Comparisons were adjusted for prespecified confounders (age, admission National Institutes of Health Stroke Scale score, Alberta Stroke Program Early CT Score, intravenous thrombolysis, and time from onset to puncture), as well as for meaningful baseline between-group differences.

RESULTS

A total of 2939 patients were analyzed, of whom 877 (29.8%) were on prior APT. Patients with prior APT were older, had more frequent vascular risk factors, cardioembolic stroke mechanism, and prestroke disability. Rates of complete reperfusion (37.9% in the APT- group versus 42.7 % in the APT+ group; aOR, 1.09 [95% CI, 0.88-1.34]; P=0.41) and periprocedural complication (16.9% versus 13.3%; aOR, 0.90 [95% CI, 0.7-1.2]; P=0.66) did not differ between the two groups. Symptomatic intracerebral hemorrhage (aOR, 0.93 [95% CI, 0.63-1.37]; P=0.73), 3 months favorable clinical outcome (modified Rankin Scale score of 0-2; aOR, 0.98 [95% CI, 0.77-1.25]; P=0.89), and mortality (aOR, 0.95 [95% CI, 0.72-1.26]; P=0.76) at 90 days did not differ between the groups.

CONCLUSIONS

Prior APT does not influence angiographic and functional outcomes following endovascular therapy and should not be taken into account for acute revascularization strategies.

Platelet Activation and Chemokine Release Are Related to Local Neutrophil-Dominant Inflammation During Hyperacute Human Stroke

Experimental evidence has emerged that local platelet activation contributes to inflammation and infarct formation in acute ischemic stroke (AIS) which awaits confirmation in human studies. We conducted a prospective observational study on 258 consecutive patients undergoing mechanical thrombectomy (MT) due to large-vessel-occlusion stroke of the anterior circulation (08/2018–05/2020). Intraprocedural microcatheter aspiration of 1 ml of local (occlusion condition) and systemic arterial blood samples (self-control) was performed according to a prespecified protocol. The samples were analyzed for differential leukocyte counts, platelet counts, and plasma levels of the platelet-derived neutrophil-activating chemokine C-X-C-motif ligand (CXCL) 4 (PF-4), the neutrophil attractant CXCL7 (NAP-2), and myeloperoxidase (MPO). The clinical-biological relevance of these variables was corroborated by specific associations with molecular-cellular, structural-radiological, hemodynamic, and clinical-functional parameters. Seventy consecutive patients fulfilling all predefined criteria entered analysis. Mean local CXCL4 (+ 39%: 571 vs 410 ng/ml, P = .0095) and CXCL7 (+ 9%: 693 vs 636 ng/ml, P = .013) concentrations were higher compared with self-controls. Local platelet counts were lower (− 10%: 347,582 vs 383,284/µl, P = .0052), whereas neutrophil counts were elevated (+ 10%: 6022 vs 5485/µl, P = 0.0027). Correlation analyses revealed associations between local platelet and neutrophil counts (r = 0.27, P = .034), and between CXCL7 and MPO (r = 0.24, P = .048). Local CXCL4 was associated with the angiographic degree of reperfusion following recanalization (r =  − 0.2523, P = .0479). Functional outcome at discharge correlated with local MPO concentrations (r = 0.3832, P = .0014) and platelet counts (r = 0.288, P = .0181). This study provides human evidence of cerebral platelet activation and platelet-neutrophil interactions during AIS and points to the relevance of per-ischemic thrombo-inflammatory mechanisms to impaired reperfusion and worse functional outcome following recanalization.

Inflammatory Biomarkers and Intracranial Hemorrhage after Endovascular Thrombectomy

BACKGROUND

Intracranial hemorrhage after endovascular thrombectomy is associated with poorer prognosis compared with those who do not develop the complication. Our study aims to determine predictors of post-EVT hemorrhage - more specifically, inflammatory biomarkers present in baseline serology.

METHODS

We performed a retrospective review of consecutive patients treated with EVT for acute large vessel ischemic stroke. The primary outcome of the study is the presence of ICH on the post-EVT scan. We used four definitions: the SITS-MOST criteria, the NINDS criteria, asymptomatic hemorrhage, and overall hemorrhage. We identified nonredundant predictors of outcome using backward elimination based on Akaike Information Criteria. We then assessed prediction accuracy using area under the receiver operating curve. Then we implemented variable importance ranking from logistic regression models using the drop in Naegelkerke R2 with the exclusion of each predictor.

RESULTS

Our study demonstrates a 6.3% SITS (16/252) and 10.0% NINDS (25/252) sICH rate, as well as a 19.4% asymptomatic (49/252) and 29.4% (74/252) overall hemorrhage rate. Serologic markers that demonstrated association with post-EVT hemorrhage were: low lymphocyte count (SITS), high neutrophil count (NINDS, overall hemorrhage), low platelet to lymphocyte ratio (NINDS), and low total WBC (NINDS, asymptomatic hemorrhage).

CONCLUSION

Higher neutrophil counts, low WBC counts, low lymphocyte counts, and low platelet to lymphoycyte ratio were baseline serology biomarkers that were associated with post-EVT hemorrhage. Our findings, particularly the association of diabetes mellitus and high neutrophil, support experimental data on the role of thromboinflammation in hemorrhagic transformation of large vessel occlusions.

Thrombolytic strategies for ischemic stroke in the thrombectomy era

Twenty-five years ago, intravenous thrombolysis has revolutionized the care of patients with acute ischemic stroke. Since 2015, randomized clinical trials have demonstrated that mechanical thrombectomy improves functional outcome in stroke patients over intravenous thrombolysis alone. More recently, three randomized clinical trials have suggested that mechanical thrombectomy alone is noninferior to a combined strategy with both intravenous thrombolysis and mechanical thrombectomy. In the present review, we will present the last clinical and preclinical studies on the use of thrombolysis in stroke patients in the modern thrombectomy era. At the cost of a potential increased risk of hemorrhagic transformation, thrombolysis may promote arterial recanalization before thrombectomy, improve the rate of successful recanalization after thrombectomy, and restore microcirculation patency downstream of the main thrombus. Besides, new thrombolytic strategies targeting tissue-type plasminogen activator resistant thrombi are being developed, which could strengthen the beneficial effects of thrombolysis without carrying additional pro-hemorrhagic effects. For instance, tenecteplase has shown improved rate of recanalization compared with tissue-type plasminogen activator (alteplase). Beyond fibrinolysis, DNA- and von Willebrand factor-targeted thrombolytic strategies have shown promising results in experimental models of ischemic stroke. New combined strategies, improved thrombolytics, and dedicated clinical trials in selected patients are eagerly awaited to further improve functional outcome in stroke.

Pseudoginsenoside-F11 ameliorates thromboembolic stroke injury in rats by reducing thromboinflammation

Pseudoginsenoside-F11 (PF11), an ocotillol-type ginsenoside, has been reported to exert neuroprotective effects on ischemic stroke induced by permanent and transient middle cerebral artery occlusion in experimental animals. The aim of the present study was to investigate the effect of PF11 on thromboembolic stroke in rats and its possible mechanisms on thromboinflammation. PF11 (4, 12, 36 mg/kg) was injected intravenously (i.v.) once a day for 3 consecutive days to male Wistar rats followed by embolic middle cerebral artery occlusion (eMCAO). The results showed that PF11 significantly reduced the cerebral infarction volume, brain edema and neurological deficits induced by eMCAO. Meanwhile, the thromboinflammation in the ischemic hemisphere was observed at 24 h after eMCAO, as indicated by the increased number of microvascular thrombus and inflammatory response. Moreover, eMCAO resulted in the up-regulation of platelet glycoprotein Ibα (GPIbα) and VI (GPVI), as well as the activation of contact-kinin pathway. Notably, PF11 significantly reversed all these changes. Furthermore, PF11 prevented the eMCAO-induced loss of tight junction proteins and up-regulation of matrix metalloproteinase-9 (MMP-9), thus leading to the alleviation of blood-brain barrier (BBB) damage. In conclusion, the present study revealed that thromboinflammation was induced in the ischemic hemisphere of rats after eMCAO and PF11 exerted marked protective effects against thromboembolic stroke by attenuating thromboinflammation and preventing BBB damage. This research further identifies the potential therapeutic role of PF11 for ischemic stroke.

Downregulation of CD151 restricts VCAM-1 mediated leukocyte infiltration to reduce neurobiological injuries after experimental stroke

Background

Translational failures in anti-adhesion molecule therapies after stroke reveal the necessity of developing new strategies that not only interrupt leukocyte recruitment but also consider the inhibition of endothelial cell inflammation, verification of therapeutic time window, and normal function maintenance of circulating leukocytes. Our study focused on the potential therapeutic value of CD151 downregulation in improving current anti-adhesion molecule therapies.

Methods

Lentivirus intracerebroventricular administration was conducted to inhibit the CD151 expression and observe its functional influence on neurological injuries and outcomes. Then, immunohistochemistry and myeloperoxidase activity assessment were performed to explore the effects of CD151 expression on neutrophil and monocyte recruitment after rat cerebral ischemia. Primary rat brain microvascular endothelial cells were subjected to oxygen glucose deprivation and reoxygenation to elucidate the underlying working mechanisms between CD151 and VCAM-1.

Results

The CD151 downregulation remarkably reduced neurological injuries and improved neurological outcomes, which were accompanied with reduced neutrophil and monocyte infiltration after the CD151 downregulation. The VCAM-1 expression was remarkably decreased among the adhesion molecules on the endothelial cell responsible for neutrophil and monocyte infiltration. The activation of p38 MAPK and NF-κB pathways was restricted after the CD151 downregulation. p38 MAPK and NF-κB inhibitors decreased the VCAM-1 expression, and p38 acted as an upstream regulator of NF-κB. However, CD151 downregulation did not directly influence the neutrophil and monocyte activation.

Conclusions

Overall, CD151 regulated the expression of adhesion molecules. It also played a critical role in suppressing VCAM-1-mediated neutrophil and monocyte infiltration via the p38/NF-κB pathway. This study possibly provided a new basis for improving current anti-adhesion molecule therapies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02171-6.

Reperfusion failure despite recanalization in stroke: New translational evidence

Current treatment for acute ischemic stroke aims at recanalizing the occluded blood vessel to reperfuse ischemic brain tissue. Clot removal can be achieved pharmacologically with a thrombolytic drug, such as recombinant tissue plasminogen activator, or with mechanical thrombectomy. However, reopening the occluded vessel does not guarantee full tissue reperfusion, which has been referred to as reperfusion failure. When it occurs, reperfusion failure significantly attenuates the beneficial effect of recanalization therapy and severely affects functional recovery of stroke patients. The mechanisms of reperfusion failure are somewhat complex and not fully understood. Briefly, after stroke, capillaries show stalls, constriction and luminal narrowing, being crowded with neutrophils, and fibrin–platelet deposits. Furthermore, after recanalization in stroke patients, a primary clot can break, dislodge, and occlude distal arterial branches further downstream. In this review, we highlight a rodent model that allows studying the pathophysiological mechanisms underlying reperfusion failure after stroke. We also describe the vascular and intravascular changes involved in reperfusion, which may provide relevant therapeutic targets for improving treatment of stroke patients.

Platelets and lymphocytes drive progressive penumbral tissue loss during middle cerebral artery occlusion in mice

Background

In acute ischemic stroke, cessation of blood flow causes immediate tissue necrosis within the center of the ischemic brain region accompanied by functional failure in the surrounding brain tissue designated the penumbra. The penumbra can be salvaged by timely thrombolysis/thrombectomy, the only available acute stroke treatment to date, but is progressively destroyed by the expansion of infarction. The underlying mechanisms of progressive infarction are not fully understood.

Methods

To address mechanisms, mice underwent filament occlusion of the middle cerebral artery (MCAO) for up to 4 h. Infarct development was compared between mice treated with antigen-binding fragments (Fab) against the platelet surface molecules GPIb (p0p/B Fab) or rat immunoglobulin G (IgG) Fab as control treatment. Moreover, Rag1^−/− mice lacking T-cells underwent the same procedures. Infarct volumes as well as the local inflammatory response were determined during vessel occlusion.

Results

We show that blocking of the platelet adhesion receptor, glycoprotein (GP) Ibα in mice, delays cerebral infarct progression already during occlusion and thus before recanalization/reperfusion. This therapeutic effect was accompanied by decreased T-cell infiltration, particularly at the infarct border zone, which during occlusion is supplied by collateral blood flow. Accordingly, mice lacking T-cells were likewise protected from infarct progression under occlusion.

Conclusions

Progressive brain infarction can be delayed by blocking detrimental lymphocyte/platelet responses already during occlusion paving the way for ultra-early treatment strategies in hyper-acute stroke before recanalization.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02095-1.

Endothelial S1P1 Signaling Counteracts Infarct Expansion in Ischemic Stroke

RATIONALE

Cerebrovascular function is critical for brain health, and endogenous vascular protective pathways may provide therapeutic targets for neurological disorders. S1P (Sphingosine 1-phosphate) signaling coordinates vascular functions in other organs, and S1P1 (S1P receptor-1) modulators including fingolimod show promise for the treatment of ischemic and hemorrhagic stroke. However, S1P1 also coordinates lymphocyte trafficking, and lymphocytes are currently viewed as the principal therapeutic target for S1P1 modulation in stroke.

OBJECTIVE

To address roles and mechanisms of engagement of endothelial cell S1P1 in the naive and ischemic brain and its potential as a target for cerebrovascular therapy.

METHODS AND RESULTS

Using spatial modulation of S1P provision and signaling, we demonstrate a critical vascular protective role for endothelial S1P1 in the mouse brain. With an S1P1 signaling reporter, we reveal that abluminal polarization shields S1P1 from circulating endogenous and synthetic ligands after maturation of the blood-neural barrier, restricting homeostatic signaling to a subset of arteriolar endothelial cells. S1P1 signaling sustains hallmark endothelial functions in the naive brain and expands during ischemia by engagement of cell-autonomous S1P provision. Disrupting this pathway by endothelial cell-selective deficiency in S1P production, export, or the S1P1 receptor substantially exacerbates brain injury in permanent and transient models of ischemic stroke. By contrast, profound lymphopenia induced by loss of lymphocyte S1P1 provides modest protection only in the context of reperfusion. In the ischemic brain, endothelial cell S1P1 supports blood-brain barrier function, microvascular patency, and the rerouting of blood to hypoperfused brain tissue through collateral anastomoses. Boosting these functions by supplemental pharmacological engagement of the endothelial receptor pool with a blood-brain barrier penetrating S1P1-selective agonist can further reduce cortical infarct expansion in a therapeutically relevant time frame and independent of reperfusion.

CONCLUSIONS

This study provides genetic evidence to support a pivotal role for the endothelium in maintaining perfusion and microvascular patency in the ischemic penumbra that is coordinated by S1P signaling and can be harnessed for neuroprotection with blood-brain barrier-penetrating S1P1 agonists.

Tissue no-reflow despite full recanalization following thrombectomy for anterior circulation stroke with proximal occlusion: A clinical study

Despite early thrombectomy, a sizeable fraction of acute stroke patients with large vessel occlusion have poor outcome. The no-reflow phenomenon, i.e. impaired microvascular reperfusion despite complete recanalization, may contribute to such "futile recanalizations". Although well reported in animal models, no-reflow is still poorly characterized in man. From a large prospective thrombectomy database, we included all patients with intracranial proximal occlusion, complete recanalization (modified thrombolysis in cerebral infarction score 2c-3), and availability of both baseline and 24 h follow-up MRI including arterial spin labeling perfusion mapping. No-reflow was operationally defined as i) hypoperfusion ≥40% relative to contralateral homologous region, assessed with both visual (two independent investigators) and automatic image analysis, and ii) infarction on follow-up MRI. Thirty-three patients were eligible (median age: 70 years, NIHSS: 18, and stroke onset-to-recanalization delay: 208 min). The operational criteria were met in one patient only, consistently with the visual and automatic analyses. This patient recanalized 160 min after stroke onset and had excellent functional outcome. In our cohort of patients with complete and stable recanalization following thrombectomy for intracranial proximal occlusion, severe ipsilateral hypoperfusion on follow-up imaging associated with newly developed infarction was a rare occurrence. Thus, no-reflow may be infrequent in human stroke and may not substantially contribute to futile recanalizations.

Pre-procedural predictive factors of symptomatic intracranial hemorrhage after thrombectomy in stroke

OBJECTIVE

Symptomatic intracerebral hemorrhage (sICH) is a common complication of acute ischemic stroke (AIS) associated with limited treatments and poor outcomes. We aimed to identify predictive factors of sICH in patients with AIS following mechanical thrombectomy (MT) in a real-world setting.

METHODS

Patients with large vessel occlusion of the anterior circulation treated with MT were consecutively included in a prospective monocentric cohort. Clinical, biological, and radiological parameters were collected to identify pre-procedural predictors for sICH.

RESULTS

637 patients were included in our study. Magnetic resonance imaging was performed on most patients (86.7%). sICH occurred in 55 patients (8.6%). 428 patients (67.2%) were treated with intravenous thrombolysis. After multivariate analysis, prior use of antiplatelet therapies (odd ratio (OR) 1.84, 95% confidence interval (CI) 1.01-3.32), high C-reactive protein (OR per standard deviation (SD) increase 1.28, 95% 1.01-1.63), elevated mean arterial blood pressure (OR per 10 mmHg increase 1.22, 95% CI 1.03-1.44), hyperglycemia (OR per one SD-log increase 1.38, 95% CI 1.02-1.87), and low ASPECTS (OR per 1-point decrease 1.42, 95% CI 1.12-1.80) were found to be independent predictive factors of sICH. The pre-procedural predictors did not change when the absence of successful recanalization was considered as a covariate. Patients with strokes of unknown onset time were not especially vulnerable for sICH.

CONCLUSION

sICH after MT was associated with several pre-procedural risk factors: prior use of antiplatelet therapies, high C-reactive protein and hyperglycemia at baseline, elevated mean arterial blood pressure, and low ASPECTS.

Selective inhibition of carboxypeptidase U may reduce microvascular thrombosis in rat experimental stroke

BACKGROUND

Carboxypeptidase U (CPU, CPB2, TAFIa) is a potent attenuator of fibrinolysis. The inhibition of CPU is thus an interesting strategy for improving thrombolysis.

OBJECTIVES

The time course of CPU generation and proCPU consumption were assessed in an experimental rat model of acute ischemic stroke (AIS). In addition, the effects of the selective CPU inhibitor AZD9684 on CPU kinetics, microvascular thrombosis (MT), and AIS outcome were evaluated.

METHODS

Rats were subjected to transient middle cerebral artery occlusion (tMCAO) and received recombinant tissue-type plasminogen activator (tPA), a specific CPU inhibitor (AZD9684), combination therapy of tPA and AZD9684, or saline for 1 hour using a randomized treatment regime. CPU and proCPU levels were determined at five time points and assessed in light of outcome parameters (a.o.: infarct volume and fibrin[ogen] deposition as a measure for MT).

RESULTS

Clear activation of the CPU system was observed after AIS induction, in both saline- and tPA-treated rats. Maximal CPU activities were observed at treatment cessation and were higher in tPA-treated animals compared to the saline group. Concomitant proCPU consumption was more pronounced in tPA-treated rats. AZD9684 suppressed the CPU activity and reduced fibrin(ogen) deposition, suggesting a reduction of MT. Nonetheless, a significant decrease in infarct volume was not observed.

CONCLUSIONS

A pronounced activation of the CPU system was observed during tMCAO in rats. Selective inhibition of CPU with AZD9684 was able to reduce fibrin(ogen) deposition and brain edema, suggesting a reduction of MT but without a significant effect on final infarct volume.

Identification of Predictors for Hemorrhagic Transformation in Patients with Acute Ischemic Stroke After Endovascular Therapy Using the Decision Tree Model

Purpose

This study aimed to identify independent predictors for the risk of hemorrhagic transformation (HT) in arterial ischemic stroke (AIS) patients.

Methods

Consecutive patients with AIS due to large artery occlusion in the anterior circulation treated with mechanical thrombectomy (MT) were enrolled in a tertiary stroke center. Demographic and medical history data, admission lab results, and Circle of Willis (CoW) variations were collected from all patients.

Results

Altogether, 90 patients were included in this study; among them, 34 (37.8%) had HT after MT. The final pruned decision tree (DT) model consisted of collateral score and platelet to lymphocyte ratios (PLR) as predictors. Confusion matrix analysis showed that 82.2% (74/90) were correctly classified by the model (sensitivity, 79.4%; specificity, 83.9%). The area under the ROC curve (AUC) was 81.7%. The DT model demonstrated that participants with collateral scores of 2–4 had a 75.0% probability of HT. For participants with collateral scores of 0–1, if PLR at admission was <302, participants had a 13.0% probability of HT; otherwise, participants had an 75.0% probability of HT. The final adjusted multivariate logistic regression analysis indicated that collateral score 0–1 (OR, 10.186; 95% CI, 3.029–34.248; p < 0.001), PLR (OR, 1.005; 95% CI, 1.001–1.010; p = 0.040), and NIHSS at admission (OR, 1.106; 95% CI, 1.014–1.205; p = 0.022) could be used to predict HT. The AUC for the model was 0.855, with 83.3% (75/90) were correctly classified (sensitivity, 79.4%; specificity, 87.3%). Less patients with HT achieved independent outcomes (mRS, 0–2) in 90 days (20.6% vs. 64.3%, p < 0.001). Rate of poor outcomes (mRS, 4–6) was significantly higher in patients with HT (73.5% vs. 19.6%; p < 0.001).

Conclusion

Both the DT model and multivariate logistic regression model confirmed that the lower collateral status and the higher PLR were significantly associated with an increased risk for HT in AIS patients after MT. PLR may be one of the cost-effective and practical predictors for HT. Further prospective multicenter studies are needed to validate our findings.

Targeting Myeloid-Specific Integrin α9β1 Improves Short- and Long-Term Stroke Outcomes in Murine Models With Preexisting Comorbidities by Limiting Thrombosis and Inflammation

RATIONALE

Currently, there is no effective intervention available that can reduce brain damage following reperfusion. Clinical studies suggest a positive correlation between the increased influx of neutrophils and severity of brain injury following reperfusion. Integrin α9β1 is highly expressed on activated neutrophils and contributes to stable adhesion, but its role in stroke outcome has not been demonstrated to date.

OBJECTIVE

We sought to determine the mechanistic role of myeloid-specific α9β1 in the progression of ischemic stroke in murine models with preexisting comorbidities.

METHODS AND RESULTS

We generated novel myeloid-specific α9-deficient (α9-/-) wild type (α9fl/flLysMCre+/-), hyperlipidemic (α9fl/flLysMCre+/-Apoe-/-), and aged (bone marrow chimeric) mice to evaluate stroke outcome. Susceptibility to ischemia/reperfusion injury was evaluated at 1, 7, and 28 days following reperfusion in 2 models of experimental stroke: filament and embolic. We found that peripheral neutrophils displayed elevated α9 expression following stroke. Irrespective of sex, genetic deletion of α9 in myeloid cells improved short- and long-term stroke outcomes in the wild type, hyperlipidemic, and aged mice. Improved stroke outcome and enhanced survival in myeloid-specific α9-/- mice was because of marked decrease in cerebral thromboinflammatory response as evidenced by reduced fibrin, platelet thrombi, neutrophil, NETosis, and decreased phospho-NF-κB (nuclear factor-κB), TNF (tumor necrosis factor)-α, and IL (interleukin)-1β levels. α9-/- mice were less susceptible to FeCl3 injury-induced carotid artery thrombosis that was concomitant with improved regional cerebral blood flow following stroke as revealed by laser speckle imaging. Mechanistically, fibronectin containing extra domain A, a ligand for integrin α9, partially contributed to α9-mediated stroke exacerbation. Infusion of a specific anti-integrin α9 inhibitor into hyperlipidemic mice following reperfusion significantly reduced infarct volume and improved short- and long-term functional outcomes up to 28 days.

CONCLUSIONS

We provide genetic and pharmacological evidence for the first time that targeting myeloid-specific integrin α9β1 improves short- and long-term functional outcomes in stroke models with preexisting comorbidities by limiting cerebral thrombosis and inflammation.

Local Leukocyte Invasion during Hyperacute Human Ischemic Stroke

OBJECTIVE

Bridging the gap between experimental stroke and patients by ischemic blood probing during the hyperacute stage of vascular occlusion is crucial to assess the role of inflammation in human stroke and for the development of adjunct treatments beyond recanalization.

METHODS

We prospectively observed 151 consecutive ischemic stroke patients with embolic large vessel occlusion of the anterior circulation who underwent mechanical thrombectomy. In all these patients, we attempted microcatheter aspiration of 3 different arterial blood samples: (1) within the core of the occluded vascular compartment and controlled by (2) carotid and (3) femoral samples obtained under physiological flow conditions. Subsequent laboratory analyses comprised leukocyte counting and differentiation, platelet counting, and the quantification of 13 proinflammatory human chemokines/cytokines.

RESULTS

Forty patients meeting all clinical, imaging, interventional, and laboratory inclusion criteria could be analyzed, showing that the total number of leukocytes significantly increased under the occlusion condition. This increase was predominantly driven by neutrophils. Significant increases were also apparent for lymphocytes and monocytes, accompanied by locally elevated plasma levels of the T-cell chemoattractant CXCL-11. Finally, we found evidence that short-term clinical outcome (National Institute of Health Stroke Scale at 72 hours) was negatively associated with neutrophil accumulation.

INTERPRETATION

We provide the first direct human evidence that neutrophils, lymphocytes, and monocytes, accompanied by specific chemokine upregulation, accumulate in the ischemic vasculature during hyperacute stroke and may affect outcome. These findings strongly support experimental evidence that immune cells contribute to acute ischemic brain damage and indicate that ischemic inflammation initiates already during vascular occlusion. Ann Neurol 2020;87:466-479.

In vivo photoacoustic imaging dynamically monitors the structural and functional changes of ischemic stroke at a very early stage

Ischemic stroke (IS) is one of the leading causes of death and accounts for 85% of stroke cases. Since the symptoms are not obvious, diagnosis of IS, particularly at an early stage, is a great challenge. Photoacoustic imaging combines high sensitivity of optical imaging and fine resolution of ultrasonography to non-invasively provide structural and functional information of IS.

Methods: We adopted three rapid photoacoustic imaging systems with varying characteristics, including a portable handheld photoacoustic system, high-sensitivity bowl-shaped array photoacoustic computed tomography (PACT), and high-resolution photoacoustic microscopy (PAM) to assess the stereoscopic and comprehensive pathophysiological status of IS at an early stage. Two representative models of IS, referring to photothrombosis and middle cerebral artery occlusion (MCAO) models, were established to verify the feasibility of photoacoustic imaging detection.

Results: Non-invasive, rapid PACT of the IS model in mouse provided structural information of the brain lesion, achieving early disease identification (5 min after the onset of disease). Moreover, it was able to dynamically reflect disease progression. Quantitative high-resolution PAM allowed observation of pathological changes in the microvascular system of mouse brain. In terms of functional imaging, significant differences in oxygen saturation (sO₂) levels between infarcted and normal areas could be observed by PACT, permitting effective functional parameters for the diagnosis of IS.

Conclusions: We used PACT to perform full-view structural imaging and functional imaging of sO₂ in IS at the macroscopic level, and then observed the microvascular changes in the infarcted area at the microscopic level by using PAM. This work may provide new tools for the early diagnosis of IS and its subsequent complications as well as assessment of disease progression.

von Willebrand Factor and Platelet Glycoprotein Ib: A Thromboinflammatory Axis in Stroke

von Willebrand factor (VWF) and platelets are key mediators of normal hemostasis. At sites of vascular injury, VWF recruits platelets via binding to the platelet receptor glycoprotein Ibα (GPIbα). Over the past decades, it has become clear that many hemostatic factors, including VWF and platelets, are also involved in inflammatory processes, forming intriguing links between hemostasis, thrombosis, and inflammation. The so-called “thrombo-inflammatory” nature of the VWF-platelet axis becomes increasingly recognized in different cardiovascular pathologies, making it a potential therapeutic target to interfere with both thrombosis and inflammation. In this review, we discuss the current evidence for the thrombo-inflammatory activity of VWF with a focus on the VWF-GPIbα axis and discuss its implications in the setting of ischemic stroke.

CD69 Plays a Beneficial Role in Ischemic Stroke by Dampening Endothelial Activation

RATIONALE

CD69 is an immunomodulatory molecule induced during lymphocyte activation. Following stroke, T-lymphocytes upregulate CD69 but its function is unknown.

OBJECTIVE

We investigated whether CD69 was involved in brain damage following an ischemic stroke.

METHODS AND RESULTS

We used adult male mice on the C57BL/6 or BALB/c backgrounds, including wild-type mice and CD69^-/- mice, and CD69^+/+ and CD69^-/- lymphocyte-deficient Rag2^-/- mice, and generated chimeric mice. We induced ischemia by transient or permanent middle cerebral artery occlusion. We measured infarct volume, assessed neurological function, and studied CD69 expression, as well as platelet function, fibrin(ogen) deposition, and VWF (von Willebrand factor) expression in brain vessels and VWF content and activity in plasma, and performed the tail-vein bleeding test and the carotid artery ferric chloride-induced thrombosis model. We also performed primary glial cell cultures and sorted brain CD45^-CD11b^-CD31⁺ endothelial cells for mRNA expression studies. We blocked VWF by intravenous administration of anti-VWF antibodies. CD69^-/- mice showed larger infarct volumes and worse neurological deficits than the wild-type mice after ischemia. This worsening effect was not attributable to lymphocytes or other hematopoietic cells. CD69 deficiency lowered the time to thrombosis in the carotid artery despite platelet function not being affected. Ischemia upregulated Cd69 mRNA expression in brain endothelial cells. CD69-deficiency increased fibrin(ogen) accumulation in the ischemic tissue, and plasma VWF content and activity, and VWF expression in brain vessels. Blocking VWF reduced infarct volume and reverted the detrimental effect of CD69^-/- deficiency.

CONCLUSIONS

CD69 deficiency promotes a prothrombotic phenotype characterized by increased VWF and worse brain damage after ischemic stroke. The results suggest that CD69 acts as a downregulator of endothelial activation.

Neutrophil count predicts poor outcome despite recanalization after endovascular therapy

Objective

To identify early prognostic factors of poor clinical outcome in patients treated by endovascular therapy (EVT) with successful recanalization.

Methods

We reviewed our monocentric prospectively collected EVT database of patients with anterior circulation acute ischemic stroke (AIS) from January 2016 to April 2018 who had achieved successful recanalization (Thrombolysis in Cerebral Infarction score ≥ 2b) at the end of the procedure. A poor outcome was defined as a 3-month modified Rankin Scale score of ≥3.

Results

A total of 324 patients were included, among whom 186 (57.4%) had a poor outcome. Multivariate logistic regression indicated that age (per 10-year increase, odds ratio [OR] 1.34, 95% confidence interval [CI] 1.12–1.60), baseline NIH Stroke Scale score (per 1-unit increase, OR 1.09, 95% CI 1.04–1.15), initial infarct volume (per a log+1 increase, OR 1.34, 95% CI 1.05–1.67), blood glucose level (per a log+1 increase, OR 2.60, 95% CI 1.01–6.66), and neutrophil count (per 1,000-unit increase, OR 1.08, 95% CI 1.01–1.17) were all associated with poor clinical outcome.

Conclusions

In addition to baseline severe AIS criteria, high neutrophil count and high blood glucose, known from experimental studies to be associated with downstream microvascular thromboinflammation, are independently associated with poor outcome. These findings support a deleterious role of thromboinflammation in patient recovery despite successful recanalization.

Spontaneous bleeding in thrombocytopenia: Is it really spontaneous?

Spontaneous bleeding is a clinical hallmark of thrombocytopenia and can take multiple forms including petechiae, epistaxis, gum bleeding, or, in worst cases, intracranial hemorrhage. Those bleeding events are called " spontaneous " because they occur in the absence of overt trauma. Spontaneous bleeding manifestations have long been considered to be a direct consequence of low platelet counts. Nevertheless, although low platelet counts may lead to ultrastructural endothelial alterations, those alterations and the associated state of vascular fragility are unlikely sufficient to cause spontaneous rupture of the microvessel wall. Indeed, in addition to endothelial injury, factors capable of damaging the basement membrane are required to allow escape of red blood cells in the extravascular space. Therefore, despite their misleading name, spontaneous bleeding events in thrombocytopenia are most likely provoked and involve subclinical biological processes in which platelets normally intervene to ensure hemostasis. In this review, we discuss past and more recent studies on the possible triggers of spontaneous bleeding events in thrombocytopenia, with a particular focus on the role of inflammatory reactions.