Targeting focal ischemic and hemorrhagic stroke neuroprotection: Current prospects for local hypothermia

Selective brain cooling with a novel catheter reduces infarct growth after recanalization in a canine large vessel occlusion model

BACKGROUND

Therapeutic hypothermia has shown potential in cardiac intervention for years; however, its adoption into the neurovascular space has been limited. Studies have pointed to slow cooling and limited depth of hypothermia yielding negative outcomes. Here we present an insulated catheter that allows for consistent infusion of chilled saline directly to the brain. Direct delivery of cold saline allows a faster depth of hypothermia, which could have a benefit to the growth of ischemic lesions.

METHODS

Ten canines were randomized to either receive selective brain cooling or no additional therapy. Eight animals were successfully enrolled (n = 4 per group). Each animal underwent a temporary middle cerebral artery occlusion (MCAO) for a total of 45 min. Five minutes prior to flow restoration, chilled saline was injected through the ipsilateral internal carotid artery using an insulated catheter to ensure delivery temperature. The treatment continued for 20 min, after which the animal was transferred to an MRI scanner for imaging.

RESULTS

Of the 8 animals that were successfully enrolled in the study, 3 were able to survive to the 30-day endpoint with no differences between the cooled and control animals. There was no difference in the initial mean infarct size between the groups; however, animals that did not receive cooling had infarcts continuing to progress more rapidly after the MCAO was removed (13.8% vs 161.3%, p = 0.016, cooled vs control).

CONCLUSIONS

Selective hypothermia was able to reduce the post-MCAO infarct progression in a canine model of temporary MCAO.

A Systematic Review and Meta-Analysis of Therapeutic Hypothermia and Pharmacological Cotherapies in Animal Models of Ischemic Stroke

Therapeutic hypothermia (TH) lessens ischemic brain injury. Cytoprotective agents can augment protection, although it is unclear which combinations are most effective. The objective of this study is to identify which cytoprotective drug works best with delayed TH. Following PRISMA guidelines, a systematic review (PubMed, Web of Science, MEDLINE, Scopus) identified controlled experiments that used an in vivo focal ischemic stroke model and evaluated the efficacy of TH (delay of ≥1 hour) coupled with cytoprotective agents. This combination was our main intervention compared with single treatments with TH, drug, or no treatment. Endpoints were brain injury and neurological impairment. The CAMARADES checklist for study quality and the SYRCLE's risk of bias tool gauged study quality. Twenty-five studies were included. Most used young, healthy male rats, with only one using spontaneously hypertensive rats. Two studies used mice models, and six used adult animals. Study quality was moderate (median score = 6), and risk of bias was high. Pharmacological agents provided an additive effect on TH for all outcomes measured. Magnesium coupled with TH had the greatest impact compared with other agent-TH combinations on all outcomes. Longer TH durations improved both behavioral and histological outcomes and had greater cytoprotective efficacy than shorter durations. Anti-inflammatories were the most effective in reducing infarction (standardized mean difference [SMD]: -1.64, confidence interval [CI]: [-2.13, -1.15]), sulfonylureas reduced edema the most (SMD: -2.32, CI: [-3.09, -1.54]), and antiapoptotic agents improved behavioral outcomes the most (normalized mean difference: 52.38, CI: [45.29, 59.46]). Statistically significant heterogeneity was observed (I2 = 82 - 98%, all p < 0.001), indicating that studies wildly differ in their effect size estimates. Our results support the superiority of adding cytoprotective therapies with TH (vs. individual or no therapy). Additional exploratory and confirmatory studies are required to identify and thoroughly assess combination therapies owing to limited work and inconsistent translational quality.

Hypothermia protects the integrity of corticospinal tracts and alleviates mitochondria injury after intracerebral hemorrhage in mice

Disruption of corticospinal tracts (CST) is a leading factor for motor impairments following intracerebral hemorrhage (ICH) in the striatum. Previous studies have shown that therapeutic hypothermia (HT) improves outcomes of ICH patients. However, whether HT has a direct protection effect on the CST integrity and the underlying mechanisms remain largely unknown. In this study, we employed a chemogenetics approach to selectively activate bilateral warm-sensitive neurons in the preoptic areas to induce a hypothermia-like state. We then assessed effects of HT treatment on the integrity of CST and motor functional recovery after ICH. Our results showed that HT treatment significantly alleviated axonal degeneration around the hematoma and the CST axons at remote midbrain region, ultimately promoted skilled motor function recovery. Anterograde and retrograde tracing revealed that HT treatment protected the integrity of the CST over an extended period. Mechanistically, HT treatment prevented mitochondrial swelling in degenerated axons around the hematoma, alleviated mitochondrial impairment by reducing mitochondrial ROS accumulation and improving mitochondrial membrane potential in primarily cultured cortical neurons with oxyhemoglobin treatment. Serving as a proof of principle, our study provided novel insights into the application of HT to improve functional recovery after ICH.

Trends and hotspots of the neuroprotection of hypothermia treatment: A bibliometric and visualized analysis of research from 1992 to 2023

AIM

Recent studies have extensively investigated hypothermia as a therapeutic approach for mitigating neural damage. Despite this, bibliometric analyses specifically focusing on this area remain scarce. Consequently, this study aims to comprehensively outline the historical framework of research and to pinpoint future research directions and trends.

METHODS

Articles spanning from 2003 to 2023, relevant to both "neuroprotection" and "hypothermia", were sourced from the Web of Science Core Collection. The CiteSpace software facilitated a comprehensive evaluation and analysis of these publications. This analysis included examining the annual productivity, collaboration among nations, institutions, and authors, as well as the network of co-cited references, authors and journals, and the co-occurrence of keywords, and their respective clusters and trends, all of which were visualized.

RESULTS

This study included 2103 articles on the neuroprotection effects of hypothermia, noting a consistent increase in publications since 1992. The United States, the University of California System, and Ji Xunming emerged as the most productive nation, institution, and author, respectively. Analysis of the top 10 co-cited publications revealed that seven articles focused on the effects of hypothermia in infants with hypoxic-ischemic encephalopathy, while three studies addressed cardiac arrest. Shankaran S and the journal Stroke were the most frequently co-cited author and journal, respectively. Keyword cluster analysis identified ischemic stroke as the primary focus of hypothermia therapy historically, with cardiac arrest and neonatal hypoxic-ischemic encephalopathy emerging as current research foci.

CONCLUSIONS

Recent studies on the neuroprotective effects of hypothermia in cardiac arrest and neonatal hypoxic-ischemic encephalopathy suggest that hypothermia may mitigate neural damage associated with these conditions. However, the application of hypothermia in the treatment of ischemic stroke remains confined to animal models and in vitro studies, with a notable absence of evidence from multicenter randomized controlled trials (RCTs). Further research is required to address this gap.

Blood biomarker changes following therapeutic hypothermia in ischemic stroke

INTRODUCTION

Therapeutic hypothermia is a promising candidate for stroke treatment although its efficacy has not yet been demonstrated in patients. Changes in blood molecules could act as surrogate markers to evaluate the efficacy and safety of therapeutic cooling.

METHODS

Blood samples from 54 patients included in the EuroHYP-1 study (27 treated with hypothermia, and 27 controls) were obtained at baseline, 24 ± 2 h, and 72 ± 4 h. The levels of a panel of 27 biomarkers, including matrix metalloproteinases and cardiac and inflammatory markers, were measured.

RESULTS

Metalloproteinase-3 (MMP-3), fatty-acid-binding protein (FABP), and interleukin-8 (IL-8) increased over time in relation to the hypothermia treatment. Statistically significant correlations between the minimum temperature achieved by each patient in the hypothermia group and the MMP-3 level measured at 72 h, FABP level measured at 24 h, and IL-8 levels measured at 24 and 72 h were found. No differential biomarker levels were observed in patients with poor or favorable outcomes according to modified Rankin Scale scores.

CONCLUSION

Although the exact roles of MMP3, FABP, and IL-8 in hypothermia-treated stroke patients are not known, further exploration is needed to confirm their roles in brain ischemia.

A systematic review and meta-analysis on the efficacy of glibenclamide in animal models of intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating stroke with many mechanisms of injury. Edema worsens outcome and can lead to mortality after ICH. Glibenclamide (GLC), a sulfonylurea 1- transient receptor potential melastatin 4 (Sur1-Trpm4) channel blocker, has been shown to attenuate edema in ischemic stroke models, raising the possibility of benefit in ICH. This meta-analysis synthesizes current pre-clinical (rodent) literature regarding the efficacy of post-ICH GLC administration (vs. vehicle controls) on behaviour (i.e., neurological deficit, motor, and memory outcomes), edema, hematoma volume, and injury volume. Six studies (5 in rats and 1 in mice) were included in our meta-analysis (PROSPERO registration = CRD42021283614). GLC significantly improved behaviour (standardized mean difference (SMD) = -0.63, [-1.16, -0.09], n = 70-74) and reduced edema (SMD = -0.91, [-1.64, -0.18], n = 70), but did not affect hematoma volume (SMD = 0.0788, [-0.5631, 0.7207], n = 18-20), or injury volume (SMD = 0.2892, [-0.4950, 1.0734], n = 24). However, these results should be interpreted cautiously. Findings were conflicted with 2 negative and 4 positive reports, and Egger regressions indicated missing negative edema data (p = 0.0001), and possible missing negative behavioural data (p = 0.0766). Experimental quality assessed via the SYRCLE and CAMARADES checklists was concerning, as most studies demonstrated high risks of bias. Studies were generally low-powered (e.g., average n = 14.4 for behaviour), and future studies should employ sample sizes of 41 to detect our observed effect size in behaviour and 33 to detect our observed effect in edema. Overall, missing negative studies, low study quality, high risk of bias, and incomplete attention to key recommendations (e.g., investigating female, aged, and co-morbid animals) suggest that further high-powered confirmatory studies are needed before conclusive statements about GLC's efficacy in ICH can be made, and before further clinical trials are performed.

Molecular, Pathological, Clinical, and Therapeutic Aspects of Perihematomal Edema in Different Stages of Intracerebral Hemorrhage

Acute intracerebral hemorrhage (ICH) is a devastating type of stroke worldwide. Neuronal destruction involved in the brain damage process caused by ICH includes a primary injury formed by the mass effect of the hematoma and a secondary injury induced by the degradation products of a blood clot. Additionally, factors in the coagulation cascade and complement activation process also contribute to secondary brain injury by promoting the disruption of the blood-brain barrier and neuronal cell degeneration by enhancing the inflammatory response, oxidative stress, etc. Although treatment options for direct damage are limited, various strategies have been proposed to treat secondary injury post-ICH. Perihematomal edema (PHE) is a potential surrogate marker for secondary injury and may contribute to poor outcomes after ICH. Therefore, it is essential to investigate the underlying pathological mechanism, evolution, and potential therapeutic strategies to treat PHE. Here, we review the pathophysiology and imaging characteristics of PHE at different stages after acute ICH. As illustrated in preclinical and clinical studies, we discussed the merits and limitations of varying PHE quantification protocols, including absolute PHE volume, relative PHE volume, and extension distance calculated with images and other techniques. Importantly, this review summarizes the factors that affect PHE by focusing on traditional variables, the cerebral venous drainage system, and the brain lymphatic drainage system. Finally, to facilitate translational research, we analyze why the relationship between PHE and the functional outcome of ICH is currently controversial. We also emphasize promising therapeutic approaches that modulate multiple targets to alleviate PHE and promote neurologic recovery after acute ICH.

Disturbed cerebral circulation and metabolism matters: A preface to the special issue "Stroke and Energy Metabolism": A preface to the special issue "Stroke and Energy Metabolism"

Stroke is a serious neurological disorder caused by blockage or rupture of cerebral blood vessels. Two main aims in acute stroke therapy include the restoration of cerebral blood flow in order to preserve energy supply to neurons and other brain cells, and minimizing neuronal loss. Maintenance of energy homeostasis in the brain drives neural network dynamics, which preserves normal brain function under physiological conditions. As such, cerebral energy homeostasis is a key target in stroke therapy. The various articles in this special issue highlight energy metabolism changes following stroke, including disturbed cerebral blood circulation, mitochondrial dysfunction, programmed neuronal cell death and cell-cell communication in brain metabolism. Collectively, this series of articles provides insight and presents new avenues for further research to improve the clinical management of stroke patients.