A multi-laboratory preclinical trial in rodents to assess treatment candidates for acute ischemic stroke

The role of oxidative stress in blood-brain barrier disruption during ischemic stroke: Antioxidants in clinical trials

Ischemic stroke is one of the leading causes of death and disability. Occlusion and reperfusion of cerebral blood vessels (i.e., ischemia/reperfusion (I/R) injury) generates reactive oxygen species (ROS) that contribute to brain cell death and dysfunction of the blood-brain barrier (BBB) via oxidative stress. BBB disruption influences the pathogenesis of ischemic stroke by contributing to cerebral edema, hemorrhagic transformation, and extravasation of circulating neurotoxic proteins. An improved understanding of mechanisms for ROS-associated alterations in BBB function during ischemia/reperfusion (I/R) injury can lead to improved treatment paradigms for ischemic stroke. Unfortunately, progress in developing ROS targeted therapeutics that are effective for stroke treatment has been slow. Here, we review how ROS are produced in response to I/R injury, their effects on BBB integrity (i.e., tight junction protein complexes, transporters), and the utilization of antioxidant treatments in ischemic stroke clinical trials. Overall, knowledge in this area provides a strong translational framework for discovery of novel drugs for stroke and/or improved strategies to mitigate I/R injury in stroke patients.

Hippocampal infarction and generalized seizures predict early mortality after endovascular middle cerebral artery occlusion in mice

Endovascular middle cerebral artery occlusion (MCAO) is a widely used experimental ischemic stroke model. However, the model carries high early mortality. Our aim was to investigate the factors that influence early mortality within 48 h of reperfusion after transient MCAO. Using C57BL/6 mice, we induced 1-hour endovascular filament MCAO. To introduce heterogeneity of infarct volumes, a subset of animals had additional tandem common carotid artery occlusion (MCAO+CCAO). Continuous video monitoring was used to gain insight into the cause of death. Mortality within 48 h was 25% in the pooled cohort. All animals with early mortality suffered from infarcts in the hippocampus, sometimes accompanied by infarcts in the thalamus and midbrain, which occurred exclusively in the MCAO+CCAO group. All animals with early mortality developed convulsive seizures captured on video monitoring. None of the animals that did not develop convulsive seizures died. Among the three regions, hippocampal infarction appeared necessary for convulsive seizures and early mortality. Our data highlight seizures as the primary cause of mortality within the first 48 h after endovascular filament MCAO, linked to hippocampal infarction. Since hippocampal blood supply is mainly from the posterior cerebral artery (PCA), avoiding concurrent PCA ischemia can decrease mortality in proximal MCAO models.

Stroke of Consistency: Streamlining Multicenter Protocols for Enhanced Reproducibility of Infarct Volumes in Preclinical Stroke Research

BACKGROUND

The discrepancy between experimental research and clinical trial outcomes is a persistent challenge in preclinical studies, particularly in stroke research. A possible factor contributing to this issue is the lack of standardization across experimental stroke models, leading to poor reproducibility in multicenter studies. This study addresses this gap by aiming to enhance reproducibility and the efficacy of multicenter studies through the harmonization of protocols and training of involved personnel.

METHODS

We established a set of standard operating procedures for various stroke models and the Neuroscore. These standard operating procedures were implemented across multiple research centers, followed by specialized, in-person training for all participants. We measured the variability in infarct volume both before and after the implementation of these standardized protocols and training sessions.

RESULTS

The standardization process led to a significant reduction in variability of infarct volume across different stroke models (40%-50% reduction), demonstrating the effectiveness of our harmonized protocols and training. Additionally, the implementation of the Neuroscore system across centers showed low variability and consistent results up to 28 days poststroke, underscoring its utility in chronic phase evaluations.

CONCLUSIONS

The harmonization of protocols and surgeon training significantly reduced variability in experimental outcomes across different centers. This improvement can increase the comparability of data between research groups and enhance the statistical power of multicenter studies. Our findings also establish the Neuroscore as a reliable tool for long-term assessment in stroke research, paving the way for more consistent and impactful multicenter preclinical studies.

Priming and Combined Strategies for the Application of Mesenchymal Stem Cells in Ischemic Stroke: A Promising Approach

Ischemic stroke (IS) is a leading cause of death and disability worldwide. Tissue plasminogen activator (tPA) administration and mechanical thrombectomy are the main treatments but have a narrow time window. Mesenchymal stem cells (MSCs), which are easily scalable in vitro and lack ethical concerns, possess the potential to differentiate into various types of cells and secrete a great number of growth factors for neuroprotection and regeneration. Moreover, MSCs have low immunogenicity and tumorigenic properties, showing safety and preliminary efficacy both in preclinical studies and clinical trials of IS. However, it is unlikely that MSC treatment alone will be sufficient to maximize recovery due to the low survival rate of transplanted cells and various mechanisms of ischemic brain damage in the different stages of IS. Preconditioning was used to facilitate the homing, survival, and secretion ability of the grafted MSCs in the ischemic region, while combination therapies are alternatives that can maximize the treatment effects, focusing on multiple therapeutic targets to promote stroke recovery. In this case, the combination therapy can yield a synergistic effect. In this review, we summarize the type of MSCs, preconditioning methods, and combined strategies as well as their therapeutic mechanism in the treatment of IS to accelerate the transformation from basic research to clinical application.

Biological and Procedural Predictors of Outcome in the Stroke Preclinical Assessment Network (SPAN) Trial

BACKGROUND

The SPAN trial (Stroke Preclinical Assessment Network) is the largest preclinical study testing acute stroke interventions in experimental focal cerebral ischemia using endovascular filament middle cerebral artery occlusion (MCAo). Besides testing interventions against controls, the prospective design captured numerous biological and procedural variables, highlighting the enormous heterogeneity introduced by the multicenter structure that might influence stroke outcomes. Here, we leveraged the unprecedented sample size achieved by the SPAN trial and the prospective design to identify the biological and procedural variables that affect experimental stroke outcomes in transient endovascular filament MCAo.

METHODS

The study cohort included all mice enrolled and randomized in the SPAN trial (N=1789). Mice were subjected to 60-minute MCAo and followed for a month. Thirteen biological and procedural independent variables and 4 functional (weight loss and 4-point neuroscore on days 1 and 2, corner test on days 7 and 28, and mortality) and 3 tissue (day 2, magnetic resonance imaging infarct volumes and swelling; day 30, magnetic resonance imaging tissue loss) outcome variables were prospectively captured. Multivariable regression with stepwise elimination was used to identify the predictors and their effect sizes.

RESULTS

Older age, active circadian stage at MCAo, and thinner and longer filament silicone tips predicted higher mortality. Older age, larger body weight, longer anesthesia duration, and longer filament tips predicted worse neuroscores, while high-fat diet and blood flow monitoring predicted milder neuroscores. Older age and a high-fat diet predicted worse corner test performance. While shorter filament tips predicted more ipsiversive turning, longer filament tips appeared to predict contraversive turning. Age, sex, and weight interacted when predicting the infarct volume. Older age was associated with smaller infarcts on day 2 magnetic resonance imaging, especially in animals with larger body weights; this association was most conspicuous in females. High-fat diet also predicted smaller infarcts. In contrast, the use of cerebral blood flow monitoring and more severe cerebral blood flow drop during MCAo, longer anesthesia, and longer filament tips all predicted larger infarcts. Bivariate analyses among the dependent variables highlighted a disconnect between tissue and functional outcomes.

CONCLUSIONS

Our analyses identified variables affecting endovascular filament MCAo outcome, an experimental stroke model used worldwide. Multiple regression refuted some commonly reported predictors and revealed previously unrecognized associations. Given the multicenter prospective design that represents a sampling of real-world conditions, the degree of heterogeneity mimicking clinical trials, the large number of predictors adjusted for in the multivariable model, and the large sample size, we think this is the most definitive analysis of the predictors of preclinical stroke outcome to date. Future multicenter experimental stroke trials should standardize or at least ensure a balanced representation of the biological and procedural variables identified herein as potential confounders.

New Perspectives in Neuroprotection for Ischemic Stroke

The constant failure of new neuroprotective therapies for ischemic stroke has partially halted the search for new therapies in recent years, mainly because of the high investment risk required to develop a new treatment for a complex pathology, such as stroke, with a narrow intervention window and associated comorbidities. However, owing to recent progress in understanding the stroke pathophysiology, improvement in patient care in stroke units, development of new imaging techniques, search for new biomarkers for early diagnosis, and increasingly widespread use of mechanical recanalization therapies, new opportunities have opened for the study of neuroprotection. This review summarizes the main protective agents currently in use, some of which are already in the clinical evaluation phase. It also includes an analysis of how recanalization therapies, new imaging techniques, and biomarkers have improved their efficacy.

Chronic consequences of ischemic stroke: Profiling brain injury and inflammation in a mouse model with reperfusion

Stroke is a pervasive and debilitating global health concern, necessitating innovative therapeutic strategies, especially during recovery. While existing literature often focuses on acute interventions, our study addresses the uniqueness of brain tissue during wound healing, emphasizing the chronic phase following the commonly used middle cerebral artery (MCA) occlusion model. Using clinically relevant endpoints in male and female mice such as magnetic resonance imaging (MRI) and plasma neurofilament light (NFL) measurement, along with immunohistochemistry, we describe injury evolution. Our findings document significant alterations in edema, tissue remodeling, and gadolinium leakage through MRI. Plasma NFL concentration remained elevated at 30 days poststroke. Microglia responses are confined to the region adjacent to the injury, rather than continued widespread activation, and boron-dipyrromethene (BODIPY) staining demonstrated the persistent presence of foam cells within the infarct. Additional immunohistochemistry highlighted sustained B and T lymphocyte presence in the poststroke brain. These observations underscore potentially pivotal roles played by chronic inflammation brought on by the lipid-rich brain environment, and chronic blood-brain barrier dysfunction, in the development of secondary neurodegeneration. This study sheds light on the enduring consequences of ischemic stroke in the most used rodent stroke model and provides valuable insights for future research, clinical strategies, and therapeutic development.

Association between uric acid levels and the risk of futile reperfusion in stroke after thrombectomy: A propensity score matching study

INTRODUCTION

Currently, futile reperfusion (FR) is becoming a major challenge in the endovascular treatment of patients with acute ischemic stroke (AIS). The relationship between serum uric acid (SUA) and FR has not been investigated. This study aims to determine the relationship between SUA and FR using propensity score matching (PSM) analysis.

METHODS

A total of 441 patients with AIS undergoing mechanical thrombectomy (MT) between August 2017 and January 2023 were included and divided into two groups based on the median SUA (297.4 μmol/L). Two groups were balanced using PSM analysis at a 1:1 ratio. The standardized mean difference (SMD) were used to assess the efficacy of the matching. Finally, 158 patients with low SUA (≤ 297.4 μmol/L) were matched with 158 patients with high SUA (>297.4 μmol/L). Predictors of FR were analyzed by multivariate logistic regression analysis in the PSM cohort.

RESULTS

After PSM, patients with low SUA (≤ 297.4 μmol/L) had a significant higher incidence of FR (72.8 %, 115/158) than patients with high SUA (>297.4 μmol/L) (48.1 %, 76/158) (P<0.001). Multivariate logistic regression analysis in the PSM cohort showed that low SUA (≤ 297.4 μmol/L) was an independent risk factor for the efficacy of reperfusion (OR: 6.403, 95 % CI: 3.123-13.129, P<0.001), suggesting that patients with SUA ≤ 297.4 μmol/L have a 6.403 times higher risk of FR than patients with SUA>297.4 μmol/L.

CONCLUSION

The results of this study suggest that low SUA (≤ 297.4 μmol/L) at admission increases the risk of FR in AIS patients undergoing MT by PSM analysis.

Angiotensin II Type 2 Receptor Agonism Alleviates Progressive Post-stroke Cognitive Impairment in Aged Spontaneously Hypertensive Rats

Hypertension and aging are leading risk factors for stroke and vascular contributions to cognitive impairment and dementia (VCID). Most animal models fail to capture the complex interplay between these pathophysiological processes. In the current study, we examined the development of cognitive impairment in 18-month-old spontaneously hypertensive rats (SHR) before and following ischemic stroke. Sixty SHRs were housed for 18 months with cognitive assessments every 6 months and post-surgery. MRI scans were performed at baseline and throughout the study. On day 3 post-stroke, rats were randomized to receive either angiotensin II type 2 receptor (AT2R) agonist Compound 21 (C21) or plain water for 8 weeks. SHRs demonstrated a progressive cognitive decline and significant MRI abnormalities before stroke. Perioperative mortality within 72 h of stroke was low. Stroke resulted in significant acute brain swelling, chronic brain atrophy, and sustained sensorimotor and behavioral deficits. There was no evidence of anhedonia at week 8. C21 enhanced sensorimotor recovery and ischemic lesion resolution at week 8. SHRs represent a clinically relevant animal model to study aging and stroke-associated VCID. This study underscores the importance of translational disease modeling and provides evidence that modulation of the AT2R signaling via C21 may be a useful therapeutic option to improve sensorimotor and cognitive outcomes even in aged animals.

Toward Quantitative Multisite Preclinical Imaging Studies in Acute Myocardial Infarction: Evaluation of the Immune-Fibrosis Axis

The immune-fibrosis axis plays a critical role in cardiac remodeling after acute myocardial infarction. Imaging approaches to monitor temporal inflammation and fibroblast activation in mice have seen wide application in recent years. However, the repeatability of quantitative measurements remains challenging, particularly across multiple imaging centers. We aimed to determine reproducibility of quantitative inflammation and fibroblast activation images acquired at 2 facilities after myocardial infarction in mice. Methods: Mice underwent coronary artery ligation and sequential imaging with 68Ga-DOTA-ECL1i to assess chemokine receptor type 2 expression at 3 d after myocardial infarction and 68Ga-FAPI-46 to assess fibroblast activation protein expression at 7 d after myocardial infarction. Images were acquired at 1 center using either a local or a consensus protocol developed with the second center; the protocols differed in the duration of isoflurane anesthesia and the injected tracer dose. A second group of animals were scanned at the second site using the consensus protocol. Image analyses performed by each site and just by 1 site were also compared. Results: The uptake of 68Ga-DOTA-ECL1i in the infarct territory tended to be higher when the consensus protocol was used (P = 0.03). No difference was observed between protocol acquisitions for 68Ga-FAPI-46. Compared with the local protocol, the consensus protocol decreased variability between individual animals. When a matched consensus protocol was used, the 68Ga-DOTA-ECL1i infarct territory percentage injected dose per gram of tissue was higher on images acquired at site B than on those acquired at site A (P = 0.006). When normalized to body weight as SUV, this difference was mitigated. Both the percentage injected dose per gram of tissue and the SUV were comparable between sites for 68Ga-FAPI-46. Image analyses at the sites differed significantly, but this difference was mitigated when all images were analyzed at site A. Conclusion: The application of a standardized acquisition protocol may lower variability within datasets and facilitate comparison of molecular radiotracer distribution between preclinical imaging centers. Like clinical studies, multicenter preclinical studies should use centralized core-based image analysis to maximize reproducibility across sites.

Immunothrombosis in neurovascular disease

A State of the Art lecture titled "Immunothrombosis in Neurovascular Diseases" was presented at the International Society on Thrombosis and Haemostasis Congress in 2023. Despite significant clinical advancements in stroke therapy, stroke remains a prominent contributor to both mortality and disability worldwide. Brain injury resulting from an ischemic stroke is a dynamic process that unfolds over time. Initially, an infarct core forms due to the abrupt and substantial blockage of blood flow. In the subsequent hours to days, the surrounding tissue undergoes gradual deterioration, primarily driven by sustained hypoperfusion, programmed cell death, and inflammation. While anti-inflammatory strategies have proven highly effective in experimental models of stroke, their successful translation to clinical use has proven challenging. To overcome this translational hurdle, a better understanding of the distinct immune response driving ischemic stroke brain injury is needed. In this review article, we give an overview of current knowledge regarding the immune response in ischemic stroke and the contribution of immunothrombosis to this process. We discuss therapeutic approaches to overcome detrimental immunothrombosis in ischemic stroke and how these can be extrapolated to other neurovascular diseases, such as Alzheimer's disease and multiple sclerosis. Finally, we summarize relevant new data on this topic presented during the 2023 International Society on Thrombosis and Haemostasis Congress.

Uric Acid: A Translational Journey in Cerebroprotection That Spanned Preclinical and Human Data

Uric acid (UA) is a strong endogenous antioxidant that neutralizes the toxicity of peroxynitrite and other reactive species on the neurovascular unit generated during and after acute brain ischemia. The realization that a rapid reduction of UA levels during an acute ischemic stroke was associated with a worse stroke outcome paved the way to investigate the value of exogenous UA supplementation to counteract the progression of redox-mediated ischemic brain damage. The long translational journey for UA supplementation recently reached a critical milestone when the results of the multicenter NIH stroke preclinical assessment network (SPAN) were reported. In a novel preclinical paradigm, 6 treatment candidates including UA supplementation were selected and tested in 6 independent laboratories following predefined criteria and strict methodological rigor. UA supplementation was the only intervention in SPAN that exceeded the prespecified efficacy boundary with male and female animals, young mice, young rats, aging mice, obese mice, and spontaneously hypertensive rats. This unprecedented achievement will allow UA to undergo clinical testing in a pivotal clinical trial through a NIH StrokeNet thrombectomy endovascular platform created to assess new treatment strategies in patients treated with mechanical thrombectomy. UA is a particularly appealing adjuvant intervention for mechanical thrombectomy because it targets the microcirculatory hypoperfusion and oxidative stress that limits the efficacy of this therapy. This descriptive review aims to summarize the translational development of UA supplementation, highlighting those aspects that likely contributed to its success. It includes having a well-defined target and mechanism of action, and an approach that simultaneously integrated rigorous preclinical assessment, with epidemiologic and preliminary human intervention studies. Validation of the clinical value of UA supplementation in a pivotal trial would confirm the translational value of the SPAN paradigm in preclinical research.