Translational Stroke Research Research Articles

Therapeutic Potential of Targeting the PERK Signaling Pathway in Ischemic Stroke.

Many pathologic states can lead to the accumulation of unfolded/misfolded proteins in cells. This causes endoplasmic reticulum (ER) stress and triggers the unfolded protein response (UPR), which encompasses three main adaptive branches. One of these UPR branches is mediated by protein kinase RNA-like ER kinase (PERK), an ER stress sensor. The primary consequence of PERK activation is the suppression of global protein synthesis, which reduces ER workload and facilitates the recovery of ER function. Ischemic stroke induces ER stress and activates the UPR. Studies have demonstrated the involvement of the PERK pathway in stroke pathophysiology; however, its role in stroke outcomes requires further clarification. Importantly, considering mounting evidence that supports the therapeutic potential of the PERK pathway in aging-related cognitive decline and neurodegenerative diseases, this pathway may represent a promising therapeutic target in stroke. Therefore, in this review, our aim is to discuss the current understanding of PERK in ischemic stroke, and to summarize pharmacologic tools for translational stroke research that targets PERK and its associated pathways.

Trends in stroke-related journals: Examination of publication patterns using topic modeling

ObjectivesThis study aims to demonstrate the capacity of natural language processing and topic modeling to manage and interpret the vast quantities of scholarly publications in the landscape of stroke research. These tools can expedite the literature review process, reveal hidden themes, and track rising research areas. Materials and methodsOur study involved reviewing and analyzing articles published in five prestigious stroke journals, namely Stroke, International Journal of Stroke, European Stroke Journal, Translational Stroke Research, and Journal of Stroke and Cerebrovascular Diseases. The team extracted document titles, abstracts, publication years, and citation counts from the Scopus database. BERTopic was chosen as the topic modeling technique. Using linear regression models, current stroke research trends were identified. Python 3.1 was used to analyze and visualize data. ResultsOut of the 35,779 documents collected, 26,732 were classified into 30 categories and used for analysis. "Animal Models," "Rehabilitation," and "Reperfusion Therapy" were identified as the three most prevalent topics. Linear regression models identified "Emboli," "Medullary and Cerebellar Infarcts," and "Glucose Metabolism" as trending topics, whereas "Cerebral Venous Thrombosis," "Statins," and "Intracerebral Hemorrhage" demonstrated a weaker trend. ConclusionsThe methodology can assist researchers, funders, and publishers by documenting the evolution and specialization of topics. The findings illustrate the significance of animal models, the expansion of rehabilitation research, and the centrality of reperfusion therapy. Limitations include a five-journal cap and a reliance on high-quality metadata.

Dynamics of cerebral blood volume during and after middle cerebral artery occlusion in rats – Comparison between ultrafast ultrasound and dynamic susceptibility contrast-enhanced MRI measurements

Tomographic perfusion imaging techniques are integral to translational stroke research paradigms that advance our understanding of the disease. Functional ultrasound (fUS) is an emerging technique that informs on cerebral blood volume (CBV) through ultrasensitive Doppler and flow velocity (CBFv) through ultrafast localization microscopy. It is not known how experimental results compare with a classical CBV-probing technique such as dynamic susceptibility contrast-enhanced perfusion MRI (DSC-MRI). To that end, we assessed hemodynamics based on uUS (n = 6) or DSC-MRI (n = 7) before, during and up to three hours after 90-minute filament-induced middle cerebral artery occlusion (MCAO) in rats. Recanalization was followed by a brief hyperperfusion response, after which CBV and CBFv temporarily normalized but progressively declined after one hour in the lesion territory. DSC-MRI data corroborated the incomplete restoration of CBV after recanalization, which may have been caused by the free-breathing anesthetic regimen. During occlusion, MCAO-induced hypoperfusion was more discrepant between either technique, likely attributable to artefactual signal mechanisms related to slow flow, and processing algorithms employed for either technique. In vivo uUS- and DSC-MRI-derived measures of CBV enable serial whole-brain assessment of post-stroke hemodynamics, but readouts from both techniques need to be interpreted cautiously in situations of very low blood flow.

Motor Rehabilitation Provides Modest Functional Benefits After Intracerebral Hemorrhage: a Systematic Review and Meta-Analysis of Translational Rehabilitation Studies.

Few certainties exist regarding the optimal type, timing, or dosage of rehabilitation after stroke. Despite differing injury mechanisms and recovery patterns following ischemic and hemorrhagic stroke, most translational stroke research is conducted after ischemia. As we enter the era of personalized medicine, exploring subtype-specific treatment efficacy is essential to optimizing recovery. Our objective was to characterize common rehabilitation interventions used after in vivo preclinical intracerebral hemorrhage (ICH) and assess the impact of post-ICH rehabilitation (vs. no-rehabilitation) on recovery of motor function. Following PRISMA guidelines, a systematic review (Academic Search Complete, CINAHL, EMBASE, Medline, PubMed Central) identified eligible articles published up to December 2022. Risk of bias (SYRCLE) and study quality (CAMARADES) were evaluated, and random-effects meta-analysis was used to assess treatment efficacy in recovery of forelimb and locomotor functions. Thirty articles met inclusion criteria, and 48 rehabilitation intervention groups were identified. Most used collagenase to model striatal ICH in young, male rodents. Aerobic exercise, enriched rehabilitation, and constraint-induced movement therapy represented ~ 70% of interventions. Study quality was low (median 4/10, range 2-8), and risk of bias was unclear. Rehabilitation provided modest benefits in skilled reaching, spontaneous impaired forelimb use, and locomotor function; however, effects varied substantially by endpoint, treatment type, and study quality. Rehabilitation statistically improves motor function after preclinical ICH, but whether these effects are functionally meaningful is unclear. Incomplete reporting and variable research quality hinder our capacity to analyze and interpret how treatment factors influence rehabilitation efficacy and recovery after ICH.

Animal models of focal ischemic stroke: brain size matters

Stroke remains the second leading cause of death worldwide and the third cause of disability-adjusted life-years. Most strokes are ischemic in nature, meaning they are caused by the disruption of cerebral blood flow resulting from obstructed blood vessels. Reperfusion therapies such as thrombolysis with tissue plasminogen activator and endovascular mechanical thrombectomy are very effective and are becoming game changers for eligible patients. Despite these advances, the achieved effects are insufficient from the perspective of the entire population of stroke patients. Therefore, there is an urgent need to expand eligibility for reperfusion therapies and implement adjuvant therapeutic measures. Animal stroke models are at the forefront of these efforts, helping to untangle complex pathophysiology and providing valuable preclinical data to guide further clinical trials. Various stroke models are available, including direct blocking of cerebral arteries or using other means to recapitulate stroke pathophysiology. International advisory boards recommend initial in vivo experiments be performed in smaller animals, such as rodents. However, second testing would be more desirable in larger animals such as cats, pigs, dogs, and non-human primates. Due to larger cerebral volume, gyrencephalization, and higher white/gray matter ratio, large animals are crucial in translational stroke research. Animal stroke models differ in the time and complexity of the stroke induction procedure, the reproducibility rate, the level of similarity to the human condition, and the possibilities for analysis, imaging, and follow-up studies. The choice of the most appropriate stroke model may translate to better bench-to-bedside translation of preclinical stroke research; ideally, this choice should be based solely on scientific merit.

Reverse Translation to Develop Post-stroke Therapeutic Interventions during Mechanical Thrombectomy: Lessons from the BACTRAC Trial.

The majority of strokes, approximately 87%, are ischemic in etiology with the remaining hemorrhagic in origin. Emergent large vessel occlusions (ELVOs) are a subtype of ischemic stroke accounting for approximately 30-40% of acute large vessel blockages. Treatment for ELVOs focuses on recanalization of the occluded vessel by time-sensitive administration of tissue plasminogen activator (tPA) or thrombus removal using mechanical thrombectomy. Although a great deal of time and resources have focused on translational stroke research, little progress has been made in the area of identifying additional new treatments for stroke. Translational limitations include difficulty simulating human comorbid conditions in animal models, as well as the temporal nature of stroke pathology. The Blood And Clot Thrombectomy Registry And Collaboration represents an ongoing tissue registry for thrombectomy patients and includes collection of intracranial arterial blood, systemic arterial blood, thrombi, as well as a series of clinical and radiographic data points for analysis. This chapter will explore the methodologies employed and results obtained from studying BACTRAC-derived human biological specimens and how they can inform translational experimental design in animal studies.

Blood-Brain Barrier Disruption in Preclinical Mouse Models of Stroke Can Be an Experimental Artifact Caused by Craniectomy.

The pathophysiological features of ischemia-related blood–brain barrier (BBB) disruption are widely studied using preclinical stroke models. However, in many of these models, craniectomy is required to confirm arterial occlusion via laser Doppler flowmetry or to enable direct ligation of the cerebral artery. In the present study, mice were used to construct a distal middle cerebral artery occlusion (dMCAO) model, a preclinical stroke model that requires craniectomy to enable direct ligation of the cerebral artery, or were subjected to craniectomy alone. dMCAO but not craniectomy caused neurodegeneration and cerebral infarction, but both procedures induced an appreciable increase in BBB permeability to Evans blue dye, fluorescein, and endogenous albumin but not to 10 kDa dextran-FITC, leading to cerebral edema. Using rats, we further showed that BBB disruption induced by craniectomy with no evidence of dural tearing was comparable to that induced by craniectomy involving tearing of the dura. In conclusion, our data demonstrated that craniectomy can be a major contributor to BBB disruption and cerebral edema in preclinical stroke models. The implications of this experimental artifact for translational stroke research and preclinical data interpretation are discussed.

The Top 100 Cited Articles Published in Translational Stroke Research.

The Top 100 Cited Articles Published in Translational Stroke Research.

Translational Stroke Research Review: Using the Mouse to Model Human Futile Recanalization and Reperfusion Injury in Ischemic Brain Tissue.

The approach to reperfusion therapies in stroke patients is rapidly evolving, but there is still no explanation why a substantial proportion of patients have a poor clinical prognosis despite successful flow restoration. This issue of futile recanalization is explained here by three clinical cases, which, despite complete recanalization, have very different outcomes. Preclinical research is particularly suited to characterize the highly dynamic changes in acute ischemic stroke and identify potential treatment targets useful for clinical translation. This review surveys the efforts taken so far to achieve mouse models capable of investigating the neurovascular underpinnings of futile recanalization. We highlight the translational potential of targeting tissue reperfusion in fully recanalized mouse models and of investigating the underlying pathophysiological mechanisms from subcellular to tissue scale. We suggest that stroke preclinical research should increasingly drive forward a continuous and circular dialogue with clinical research. When the preclinical and the clinical stroke research are consistent, translational success will follow.

Chronic T cell proliferation in brains after stroke could interfere with the efficacy of immunotherapies.

Neuroinflammation is an emerging focus of translational stroke research. Preclinical studies have demonstrated a critical role for brain-invading lymphocytes in post-stroke pathophysiology. Reducing cerebral lymphocyte invasion by anti-CD49d antibodies consistently improves outcome in the acute phase after experimental stroke models. However, clinical trials testing this approach failed to show efficacy in stroke patients for the chronic outcome 3 mo after stroke. Here, we identify a potential mechanistic reason for this phenomenon by detecting chronic T cell accumulation-evading the systemic therapy-in the post-ischemic brain. We observed a persistent accumulation of T cells in mice and human autopsy samples for more than 1 mo after stroke. Cerebral T cell accumulation in the post-ischemic brain was driven by increased local T cell proliferation rather than by T cell invasion. This observation urges re-evaluation of current immunotherapeutic approaches, which target circulating lymphocytes for promoting recovery after stroke.

STO: Stroke Ontology for Accelerating Translational Stroke Research.

IntroductionOntology-based annotation of evidence, using disease-specific ontologies, can accelerate analysis and interpretation of the knowledge domain of diseases. Although many domain-specific disease ontologies have been developed so far, in the area of cardiovascular diseases, there is a lack of ontological representation of the disease knowledge domain of stroke.MethodsThe stroke ontology (STO) was created on the basis of the ontology development life cycle and was built using Protégé ontology editor in the ontology web language format. The ontology was evaluated in terms of structural and functional features, expert evaluation, and competency questions.ResultsThe stroke ontology covers a broad range of major biomedical and risk factor concepts. The majority of concepts are enriched by synonyms, definitions, and references. The ontology attempts to incorporate different users’ views on the stroke domain such as neuroscientists, molecular biologists, and clinicians. Evaluation of the ontology based on natural language processing showed a high precision (0.94), recall (0.80), and F-score (0.78) values, indicating that STO has an acceptable coverage of the stroke knowledge domain. Performance evaluation using competency questions designed by a clinician showed that the ontology can be used to answer expert questions in light of published evidence.ConclusionsThe stroke ontology is the first, multiple-view ontology in the domain of brain stroke that can be used as a tool for representation, formalization, and standardization of the heterogeneous data related to the stroke domain. Since this is a draft version of the ontology, the contribution of the stroke scientific community can help to improve the usability of the current version.

National Institutes of Health StrokeNet During the Time of COVID-19 and Beyond.

National Institutes of Health StrokeNet During the Time of COVID-19 and Beyond.

Abstract TP20: Protocol to Isolate Lymphocytes for Flow Cytometry From BACTRAC Samples

Introduction: Since 2015, mechanical thrombectomy is the standard treatment for emergent large vessel occlusion stroke. Using standard techniques during mechanical thrombectomy, the Blood and Clot Thrombectomy Registry and Collaboration (BACTRAC) protocol (clinicaltrials.gov NCT03153683) isolates distal blood within the artery immediately downstream from the clot, peripheral blood proximal to the clot, and the thrombus. BACTRAC is the first protocol utilizing the thrombectomy technique to collect local whole blood samples during brain infarction. We aimed to augment the current collection protocol to reproducibly obtain and study local leukocyte populations during human stroke. Methods: We started with the established BACTRAC protocol previously published (PMID: 30064997). We modified the tissue collection protocol to isolate lymphocytes for flow cytometry and to bank the clot and plasma. We performed a flow cytometry panel that identifies CD3, 4, 8, 11b, 11c, 14, 19, 31, 45, 66b, 161, 183 markers to investigate populations of B-cells, T-cells, dendritic cells, NK cells, macrophages/monocytes, granulocytes, endothelial cells, and progenitors, respectively. Results: The protocol was first established in healthy controls (n=9) by drawing venous blood and simulating a vial of distal blood and a vial of proximal blood. In healthy subjects, we were able to isolate on average 2x10 6 leukocytes/ml with a viability of 97.85%. Banked lymphocytes are also viable upon reconstitution and for flow cytometry. This protocol successfully isolates leukocytes in proximal and distal blood samples in subjects undergoing mechanical thrombectomy, with identification and analysis by flow cytometry currently ongoing. Conclusions: This modification to the existing BACTRAC protocol provides the opportunity, for the first time, to study local leukocyte populations in the arteries undergoing ischemic stroke in the human condition. Efficient processing of these samples will provide insight into the neuroinflammatory microenvironment of the occlusion and accelerate translational stroke research towards new methods of diagnosis and treatment.

Are researchers moving away from animal models as a result of poor clinical translation in the field of stroke? An analysis of opinion papers

ObjectivesDespite decades of research using animals to develop pharmaceutical treatments for patients who had a stroke, few therapeutic options exist. The vast majority of interventions successful in preclinical animal studies...

Rodent Models of Developmental Ischemic Stroke for Translational Research: Strengths and Weaknesses.

Cerebral ischemia can occur at any stage in life, but clinical consequences greatly differ depending on the developmental stage of the affected brain structures. Timing of the lesion occurrence seems to be critical, as it strongly interferes with neuronal circuit development and determines the way spontaneous plasticity takes place. Translational stroke research requires the use of animal models as they represent a reliable tool to understand the pathogenic mechanisms underlying the generation, progression, and pathological consequences of a stroke. Moreover, in vivo experiments are instrumental to investigate new therapeutic strategies and the best temporal window of intervention. Differently from adults, very few models of the human developmental stroke have been characterized, and most of them have been established in rodents. The models currently used provide a better understanding of the molecular factors involved in the effects of ischemia; however, they still hold many limitations due to matching developmental stages across different species and the complexity of the human disorder that hardly can be described by segregated variables. In this review, we summarize the key factors contributing to neonatal brain vulnerability to ischemic strokes and we provide an overview of the advantages and limitations of the currently available models to recapitulate different aspects of the human developmental stroke.

Action Plan for Stroke in Europe 2018–2030

Two previous pan-European consensus meetings, the 1995 and 2006 Helsingborg meetings, were convened to review the scientific evidence and the state of current services to identify priorities for research and development and to set targets for the development of stroke care for the decade to follow. Adhering to the same format, the European Stroke Organisation (ESO) prepared a European Stroke Action Plan (ESAP) for the years 2018 to 2030, in cooperation with the Stroke Alliance for Europe (SAFE). The ESAP included seven domains: primary prevention, organisation of stroke services, management of acute stroke, secondary prevention, rehabilitation, evaluation of stroke outcome and quality assessment and life after stroke. Research priorities for translational stroke research were also identified. Documents were prepared by a working group and were open to public comments. The final document was prepared after a workshop in Munich on 21-23 March 2018. Four overarching targets for 2030 were identified: (1) to reduce the absolute number of strokes in Europe by 10%, (2) to treat 90% or more of all patients with stroke in Europe in a dedicated stroke unit as the first level of care, (3) to have national plans for stroke encompassing the entire chain of care, (4) to fully implement national strategies for multisector public health interventions. Overall, 30 targets and 72 research priorities were identified for the seven domains. The ESAP provides a basic road map and sets targets for the implementation of evidence-based preventive actions and stroke services to 2030.

Endocrine Regulator rFGF21 (Recombinant Human Fibroblast Growth Factor 21) Improves Neurological Outcomes Following Focal Ischemic Stroke of Type 2 Diabetes Mellitus Male Mice.

Background and Purpose- The complexity and heterogeneity of stroke, as well as the associated comorbidities, may render neuroprotective drugs less efficacious in clinical practice. Therefore, the development of targeted therapies to specific patient subsets has become a high priority in translational stroke research. Ischemic stroke with type 2 diabetes mellitus has a nearly double mortality rate and worse neurological outcomes. In the present study, we tested our hypothesis that rFGF21 (recombinant human fibroblast growth factor 21) administration is beneficial for improving neurological outcomes of ischemic stroke with type 2 diabetes mellitus. Methods- Type 2 diabetes mellitus db/db and nondiabetic genetic control db/+ mice were subjected into permanent focal ischemia of distal middle cerebral artery occlusion, we examined the effects of poststroke administration with rFGF21 in systemic metabolic disorders, inflammatory gatekeeper PPARγ (peroxisome proliferator-activated receptor γ) activity at 3 days, mRNA expression of inflammatory cytokines and microglia/macrophage activation at 7 days in the perilesion cortex, and last neurological function deficits, ischemic brain infarction, and white matter integrity up to 14 days after stroke of db/db mice. Results- After permanent focal ischemia, diabetic db/db mice presented confounding pathological features, including metabolic dysregulation, more severe brain damage, and neurological impairment, especially aggravated proinflammatory response and white matter integrity loss. However, daily rFGF21 treatment initiated at 6 hours after stroke for 14 days significantly normalized systemic metabolic disorders, rescued PPARγ activity decline, inhibited proinflammatory cytokine mRNA expression, and M1-like microglia/macrophage activation in the brain. Importantly, rFGF21 also significantly reduced white matter integrity loss, ischemic brain infarction, and neurological function deficits up to 14 days after stroke. The potential mechanisms of rFGF21 may in part consist of potent systematic metabolic regulation and PPARγ-activation promotion-associated antiproinflammatory roles in the brain. Conclusions- Taken together, these results suggest rFGF21 might be a novel and potent candidate of the disease-modifying strategy for treating ischemic stroke with type 2 diabetes mellitus.

Action Plan for Stroke in Europe 2018-2030.

Two previous pan-European consensus meetings, the 1995 and 2006 Helsingborg meetings, were convened to review the scientific evidence and the state of current services to identify priorities for research and development and to set targets for the development of stroke care for the decade to follow. Adhering to the same format, the European Stroke Organisation (ESO) prepared a European Stroke Action Plan (ESAP) for the years 2018 to 2030, in cooperation with the Stroke Alliance for Europe (SAFE). The ESAP included seven domains: primary prevention, organisation of stroke services, management of acute stroke, secondary prevention, rehabilitation, evaluation of stroke outcome and quality assessment and life after stroke. Research priorities for translational stroke research were also identified. Documents were prepared by a working group and were open to public comments. The final document was prepared after a workshop in Munich on 21–23 March 2018. Four overarching targets for 2030 were identified: (1) to reduce the absolute number of strokes in Europe by 10%, (2) to treat 90% or more of all patients with stroke in Europe in a dedicated stroke unit as the first level of care, (3) to have national plans for stroke encompassing the entire chain of care, (4) to fully implement national strategies for multisector public health interventions. Overall, 30 targets and 72 research priorities were identified for the seven domains. The ESAP provides a basic road map and sets targets for the implementation of evidence-based preventive actions and stroke services to 2030.

Fourth European stroke science workshop.

Lake Eibsee, Garmisch-Partenkirchen, 16 to 18 November, 2017: The European Stroke Organisation convened >120 stroke experts from 21 countries to discuss latest results and hot topics in clinical, translational and basic stroke research. Since its inception in 2011, the European Stroke Science Workshop has become a cornerstone of European Stroke Organisation's academic activities and a major highlight for researchers in the field. Participants include stroke researchers at all career stages and with different backgrounds, who convene for plenary lectures and discussions. The workshop was organised in seven scientific sessions focusing on the following topics: (1) acute stroke treatment and endovascular therapy; (2) small vessel disease; (3) opportunities for stroke research in the omics era; (4) vascular cognitive impairment; (5) intracerebral and subarachnoid haemorrhage; (6) alternative treatment concepts and (7) neural circuits, recovery and rehabilitation. All sessions started with a keynote lecture providing an overview on current developments, followed by focused talks on a timely topic with the most recent findings, including unpublished data. In the following, we summarise the key contents of the meeting. The program is provided in the online only Data Supplement. The workshop started with a key note lecture on how to improve the efficiency of clinical trial endpoints in stroke, which was delivered by Craig Anderson (Sydney, Australia) and set the scene for the following discussions.

Translational Stroke Research: Vision and Opportunities.

See related article, p 2341 Stroke risk and poststroke disability have steadily decreased in the United States over the past 2 decades because of improved prevention and access to reperfusion therapies for acute ischemic stroke, such as tPA (tissue-type plasminogen activator; alteplase) and endovascular thrombectomy. Despite the efficacy and safety of thrombolysis and thrombectomy, not all patients who receive the treatment improve to full, independent recovery, and most patients are ineligible for treatment. Additionally, there are no efficacious treatments to improve long-term outcomes for patients after the acute phase of ischemic stroke or to reduce brain injury induced by acute intracerebral hemorrhage. Therefore, development of new therapies for both acute and chronic stroke is sorely needed. Stroke occurs because of a variety of vascular pathologies and injury mechanisms, some of which are difficult to model in animals. With the exception of reperfusion therapy, preclinical research end points do not generally reflect clinical outcomes. Pharmacodynamics, pharmacokinetics, and target engagement in the human brain need to be further developed and optimized for stroke interventions so that drug level in brain tissue, time to initiation, and duration of treatment can be accurately measured in clinical trials. Many variables, such as heterogeneity of vascular pathologies, patient demographics, and a host of comorbid conditions, as well as the lack of validated biomarkers to stratify patient populations, limit the ability of typical stroke clinical trials to detect a treatment effect. To address these gaps, the National Institute of Neurological Disorders and Stroke organized and sponsored the workshop Translational Stroke Research: Vision and Opportunities, which was held in Bethesda, Maryland, on November 1 to 2, 2016. The workshop gathered over 180 registered participants from academia, industry, the Food and Drug Administration, and other public and private funding agencies. …