The role for infarct volume as a surrogate measure of functional outcome following ischemic stroke

Peripheral, but not central, IGF-1 treatment attenuates stroke-induced cognitive impairment in middle-aged female Sprague Dawley rats: The gut as a therapeutic target

Stroke results in immediate sensory or motor disability and increases the risk for long term cognitive-affective impairments. Thus, therapies are urgently needed to improve quality of life for stroke survivors, especially women who are at a greater risk for severe stroke after menopause. Most current research on stroke therapies target the central nervous system; however, stroke also impacts peripheral organ systems. Our studies using acyclic (estrogen-deficient) middle aged female Sprague Dawley rats show that this group not only displays worse outcomes after stroke as compared to adult females, but also has lower levels of the neuroprotective peptide Insulin-like Growth Factor (IGF1) in circulation. Intracerebroventricular (ICV) administration of IGF1 to this group decreases infarct volume and improves sensory motor performance in the acute phase. In this study, we show that, despite this neuroprotection, ICV-IGF1 did not reduce peripheral inflammation or improve post stroke cognitive impairment in the chronic phase. In view of the evidence that stroke induces rapid gut dysfunction, we tested whether systemic delivery of IGF1 (intraperitoneal, IP) would promote gut health and consequently improve long-term behavioral outcomes. Surprisingly, while IP-IGF1, delivered 4 h and 24 h after ischemic stroke, did not reduce infarct volume or acute sensory motor impairment, it significantly attenuated circulating levels of pro-inflammatory cytokines, and attenuated stroke-induced cognitive impairment. In addition, IP-IGF1 treatment reduced gut dysmorphology and gut dysbiosis. Our data support the conclusion that therapeutics targeting peripheral targets are critical for long-term stroke recovery, and that gut repair is a novel therapeutic target to improve brain health in aging females.

A toolkit for stroke infarct volume estimation in rodents

Stroke volume is a key determinant of infarct severity and an important metric for evaluating treatments. However, accurate estimation of stroke volume can be challenging, due to the often confined 2-dimensional nature of available data. Here, we introduce a comprehensive semi-automated toolkit to reliably estimate stroke volumes based on (1) whole brains ex-vivo magnetic resonance imaging (MRI) and (2) brain sections that underwent immunofluorescence staining. We located and quantified infarct areas from MRI three days (acute) and 28 days (chronic) after photothrombotic stroke induction in whole mouse brains. MRI results were compared with measures obtained from immunofluorescent histologic sections of the same brains. We found that infarct volume determined by post-mortem MRI was highly correlated with a deviation of only 6.6 % (acute) and 4.9 % (chronic) to the measurements as determined in the histological brain sections indicating that both methods are capable of accurately assessing brain tissue damage (Pearson r > 0.9, p < 0.001). The Dice similarity coefficient (DC) showed a high degree of coherence (DC > 0.8) between MRI-delineated regions of interest (ROIs) and ROIs obtained from histologic sections at four to six pre-defined landmarks, with histology-based delineation demonstrating higher inter-operator similarity compared to MR images. We further investigated stroke-related scarring and post-ischemic angiogenesis in cortical peri‑infarct regions and described a negative correlation between GFAP+fluorescence intensity and MRI-obtained lesion size.

Magnetic Resonance Imaging Infarct Volume Correlates with Carotid Intima-Media Thickness and Plaque Echotexture in Ischemic Stroke

Objective

To determine the correlation between cerebral infarct volume, carotid intima-media thickness (CIMT), and plaque echotexture in patients with ischemic stroke.

Materials and Methods

This was a cross-sectional study of 70 patients with ischemic stroke who were imaged using the head coil of a 1.5T Toshiba magnetic resonance machine. The volumes of infarcts were documented and calculated using the manual tracing of the infarct perimeter method. The common carotid CIMT was measured on ultrasound using a linear high-frequency 7.5 MHz transducer.

Results

Seventy subjects were evaluated. The mean magnetic resonance imaging cerebral infarct volume was 8.07% volume. Hyperechoic plaques were the most prevalent (36.7%) compared to the hypoechoic (33.3%) and isoechoic (30%) plaques. There was a moderate positive correlation between CIMT and infarct volume (r = 0.70; P = 0.001) in the entire study population. Similarly, positive correlations between CIMT and infarct volume were recorded in both the male (r = 0.73; P = 0.001) and female (r = 0.67; P = 0.001) subjects. Furthermore, subjects who presented in the acute phase (1-3 days) of ictus showed a moderate positive correlation (r = 0.621; P = 0.0001) between CIMT and infarct volume, while there was a strong positive correlation (r = 0.74; P = 0.0001) in subjects that presented in the subacute phase (4-7 days).

Conclusion

Common carotid artery CIMT correlated positively with cerebral infarct volume in patients with ischemic stroke. Furthermore, hyperechoic plaques were associated with significantly larger infarct volumes compared to hypoechoic and isoechoic plaques.

Identifying applications of virtual reality to benefit the stroke translational pipeline

As a leading cause of mortality and morbidity, stroke and its management have been studied extensively. Despite numerous pre-clinical studies identifying therapeutic targets, development of effective, specific pharmacotherapeutics remain limited. One significant limitation is a break in the translational pipeline - promising pre-clinical results have not always proven replicable in the clinic. Recent developments in virtual reality technology might help generate a better understanding of injury and recovery across the whole research pipeline in search of optimal stroke management. Here, we review the technologies that can be applied both clinically and pre-clinically to stroke research. We discuss how virtual reality technology is used to quantify clinical outcomes in other neurological conditions that have potential to be applied in stroke research. We also review current uses in stroke rehabilitation and suggest how immersive programmes would better facilitate the quantification of stroke injury severity and patient recovery comparable to pre-clinical study design. By generating continuous, standardised and quantifiable data from injury onset to rehabilitation, we propose that by paralleling pre-clinical outcomes, we can apply a better reverse-translational strategy and apply this understanding to animal studies. We hypothesise this combination of translational research strategies may improve the reliability of pre-clinical research outcomes and culminate in real-life translation of stroke management regimens and medications.

Sex differences in the diathetic effects of shift work schedules on circulating cytokine levels and pathological outcomes of ischemic stroke during middle age

Shift work is associated with increased risk for vascular disease, including stroke- and cardiovascular-related mortality. However, evidence from these studies is inadequate to distinguish the effect of altered circadian rhythms in isolation from other risk factors for stroke associated with shift work (e.g., smoking, poor diet, lower socioeconomic status). Thus, the present study examined the diathetic effects of exposure to shifted LD cycles during early adulthood on circadian rhythmicity, inflammatory signaling and ischemic stroke pathology during middle age, when stroke risk is high and outcomes are more severe. Entrainment of circadian activity was stable in all animals maintained on a fixed light:dark 12:12 cycle but was severely disrupted during exposure to shifted LD cycles (12hr advance/5d). Following treatment, circadian entrainment in the shifted LD group was distinguished by increased daytime activity and decreased rhythm amplitude that persisted into middle-age. Circadian rhythm desynchronization in shifted LD males and females was accompanied by significant elevations in circulating levels of the inflammatory cytokine IL-17A and gut-derived inflammatory mediator lipopolysaccharide (LPS) during the post-treatment period. Middle-cerebral artery occlusion, 3 months after exposure to shifted LD cycles, resulted in greater post-stroke mortality in shifted LD females. In surviving subjects, sensorimotor performance, assessed 2- and 5-days post-stroke, was impaired in males of both treatment groups, whereas in females, recovery of function was observed in fixed but not shifted LD rats. Overall, these results indicate that early exposure to shifted LD cycles promotes an inflammatory phenotype that amplifies stroke impairments, specifically in females, later in life.

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Early exposure to shifted LD cycles alters circadian entrainment of the activity rhythm that persists into middle age.

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In conjunction with circadian dysregulation, shift work-like schedules promote the induction of key inflammatory mediators.

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In females, exposure to shift work-like schedules amplifies functional impairments caused by strokes arising later in life.

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Circadian dysregulation during shift work is a hysteretic risk factor in the overall severity of ischemic strokes.

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Shift work-related circadian dysregulation affects stroke outcomes independent of lifestyle vascular disease risk factors.

Functional status at 30 and 90 days after mild ischaemic stroke

BACKGROUND/OBJECTIVE

This study compares the global disability status of patients who had a mild ischaemic stroke at 30 and 90 days poststroke, as measured by the modified Rankin Scale (mRS), and identifies predictors of change in disability status between 30 and 90 days.

METHODS

The study population included 1339 patients who had a ischaemic stroke enrolled in the Mild and Rapidly Improving Stroke Study with National Institutes of Health (NIH) stroke score 0-5 and mRS measurements at 30 and 90 days. Outcomes were (1) Improvement defined as having mRS >1 at 30 days and mRS 0-1 at 90 days OR mRS >2 at 30 days and mRS 0-2 at 90 days and (2) Worsening defined as an increase of ≥2 points or a worsening from mRS of 1 at 30 days to 2 at 90 days. Demographic and clinical characteristics at hospital arrival were abstracted from medical records, and regression models were used to identify predictors of functional improvement and decline from 30 to 90 days post-stroke. Significant predictors were mutually adjusted in multivariable models that also included age and stroke severity.

RESULTS

Fifty-seven per cent of study participants had no change in mRS value from 30 to 90 days. Overall, there was moderate agreement in mRS between the two time points (weighted kappa=0.59 (95% CI 0.56 to 0.62)). However, worsening on the mRS was observed in 7.54% of the study population from 30 to 90 days, and 17.33% improved. Participants of older age (per year OR 1.02, 95% CI 1.00 to 1.03), greater stroke severity (per NIH Stroke Scale (NIHSS) point at admission OR 1.17, 95% CI 1.03 to 1.34), and those with no alteplase treatment (OR 1.72, 95% CI 1.11 to 2.69) were more likely to show functional decline after mutual adjustment.

DISCUSSION

A quarter of all mild ischaemic stroke participants exhibited functional changes between 30 and 90 days, suggesting that the 30-day outcome may insufficiently represent long-term recovery in mild stroke and longer follow-up may be clinically necessary.

TRIAL REGISTRATION NUMBER

NCT02072681.

Neuroprotective Effect of Eco-Sustainably Extracted Grape Polyphenols in Neonatal Hypoxia-Ischemia

Polyphenols are natural compounds with promising prophylactic and therapeutic applications. However, their methods of extraction, using organic solvents, may prove to be unsuitable for daily consumption or for certain medical indications. Here, we describe the neuroprotective effects of grape polyphenols extracted in an eco-sustainable manner in a rat model of neonatal hypoxia-ischemia (NHI). Polyphenols (resveratrol, pterostilben and viniferin) were obtained using a subcritical water extraction technology to avoid organic solvents and heavy metals associated with chemical synthesis processes. A resveratrol or a polyphenol cocktail were administered to pregnant females at a nutritional dose and different time windows, prior to induction of NHI in pups. Reduced brain edema and lesion volumes were observed in rat pups whose mothers were supplemented with polyphenols. Moreover, the preservation of motor and cognitive functions (including learning and memory) was evidenced in the same animals. Our results pave the way to the use of polyphenols to prevent brain lesions and their associated deficits that follow NHI, which is a major cause of neonatal death and disabilities.

Lentivirus- or AAV-mediated gene therapy interventions in ischemic stroke: A systematic review of preclinical in vivo studies

Due to the limited therapeutic options after ischemic stroke, gene therapy has emerged as a promising choice, especially with recent advances in viral vector delivery systems. Therefore, we aimed to provide the current state of the art of lentivirus (LV) and adeno-associated virus (AAV) mediated gene interventions in preclinical ischemic stroke models. A systematic analysis including qualitative and quantitative syntheses of studies published until December 2020 was performed. Most of the 87 selected publications used adult male rodents and the preferred stroke model was transient middle cerebral artery occlusion. LV and AAV vectors were equally used for transgene delivery, however loads of AAVs were higher than LVs. Serotypes having broad cell tropism, the use of constitutive promoters, and virus delivery before the stroke induction via stereotaxic injection in the cortex and striatum were preferred in the analyzed studies. The meta-analysis based on infarct volume as the primary outcome confirmed the efficacy of the preclinical interventions. The quality assessment exposed publication bias and setbacks in regard to risks of bias and study relevance. The translational potential could increase by using specific cell targeting, post-stroke interventions, non-invasive systematic delivery, and use of large animals.

Neuroprotection by cattle encephalon glycoside and ignotin beyond the time window of thrombolysis in ischemic stroke

Cattle encephalon glycoside and ignotin (CEGI) injection is known as a multi-target neuroprotective drug that contains numerous liposoluble molecules, such as polypeptides, monosialotetrahexosyl ganglioside (GM-1), free amino acids, hypoxanthine and carnosine. CEGI has been approved by the Chinese State Food and Drug Administration and widely used in the treatments of various diseases, such as stroke and Alzheimer's disease. However, the neuroprotective effects of CEGI beyond the time window of thrombolysis (within 4.5 hours) on acute ischemic stroke remain unclear. This study constructed a rat middle cerebral artery occlusion model by suture-occluded method to simulate ischemic stroke. The first daily dose was intraperitoneally injected at 8 hours post-surgery and the CEGI treatments continued for 14 days. Results of the modified five-point Bederson scale, beam balance test and rotameric test showed the neurological function of ischemic stroke rats treated with 4 mL/kg/d CEGI improved significantly, but the mortality within 14 days did not change significantly. Brain MRI and 2,3,5-triphenyltetrazolium chloride staining confirmed that the infarct size in the 4 mL/kg/d CEGI-treated rats was significantly reduced compared with ischemic insult only. The results of transmission electron microscopy and double immunofluorescence staining showed that the hippocampal neuronal necrosis in the ischemic penumbra decreased whereas the immunopositivity of new neuronal-specific protein doublecortin and the percentage of Ki67/doublecortin positive cells increased in CEGI-treated rats compared with untreated rats. Our results suggest that CEGI has an effective neuroprotective effect on ischemic stroke when administered after the time window of thrombolysis. The study was approved by the Animal Ethics Committee of The Third Military Medical University, China.

Secondary Degeneration of White Matter After Focal Sensorimotor Cortical Ischemic Stroke in Rats

Ischemic lesions could lead to secondary degeneration in remote regions of the brain. However, the spatial distribution of secondary degeneration along with its role in functional deficits is not well understood. In this study, we explored the spatial and connectivity properties of white matter (WM) secondary degeneration in a focal unilateral sensorimotor cortical ischemia rat model, using advanced microstructure imaging on a 14 T MRI system. Significant axonal degeneration was observed in the ipsilateral external capsule and even remote regions including the contralesional external capsule and corpus callosum. Further fiber tractography analysis revealed that only fibers having direct axonal connections with the primary lesion exhibited a significant degeneration. These results suggest that focal ischemic lesions may induce remote WM degeneration, but limited to fibers tied to the primary lesion. These “direct” fibers mainly represent perilesional, interhemispheric, and subcortical axonal connections. At last, we found that primary lesion volume might be the determining factor of motor function deficits.

Fingolimod administration improves neurological functions of mice with subarachnoid hemorrhage

PURPOSE

To investigate the brain protective effects of fingolimod on inflammatory response of SAH mice.

METHODS

We utilized an endovascular mouse perforation model of SAH. Mice were divided into three groups: sham group, SAH group and SAH + Fingolimod group. Mice received either saline or fingolimod (1 mg/kg) intraperitoneally 2 h after sham surgery or SAH. The modified neurological severity score (mNSS) and Morris water maze were respectively used to evaluate the influence of nerve function. Evens blue (EB) extravasation was used to detect the permeability of blood-brain barrier, and water content in brain tissue was also detected. Flow cytometry, ELISA kits and western blotting were used to detect inflammatory factors in brain tissue.

RESULTS

The results showed that compared with SAH group, after treatment, the delay time of locating the hidden platform was shorter. The mNSS results showed that fingolimod improved the behavior of SAH mice. In addition, fingolimod could reduce the water content in brain. Flow cytometry results showed that after 3 d of treatment, fingolimod significantly increased Treg cells and down-regulated NK cells. Western blotting results showed fingolimod inhibited the expression of inflammatory cytokines in brain tissue. ELISA kit results showed that fingolimod could down-regulate IL-6 and TNF-α and up-regulate IL-10 and TGF-β1 in serum.

CONCLUSIONS

Fingolimod could regulate the inflammatory response to alleviate SAH-induced brain damage and promote neurological recovery, which provides a new therapeutic strategy for SAH treatment.

Inhibition of VEGF Signaling Reduces Diabetes-Exacerbated Brain Swelling, but Not Infarct Size, in Large Cerebral Infarction in Mice

In light of repeated translational failures with preclinical neuroprotection-based strategies, this preclinical study reevaluates brain swelling as an important pathological event in diabetic stroke and investigates underlying mechanism of the comorbidity-enhanced brain edema formation. Type 2 (mild), type 1 (moderate), and mixed type 1/2 (severe) diabetic mice were subjected to transient focal ischemia. Infarct volume, brain swelling, and IgG extravasation were assessed at 3 days post-stroke. Expression of vascular endothelial growth factor (VEGF)-A, endothelial-specific molecule-1 (Esm1), and the VEGF receptor 2 (VEGFR2) was determined in the ischemic brain. Additionally, SU5416, a VEGFR2 inhibitor, was treated in the type 1/2 diabetic mice, and stroke outcomes were determined. All diabetic groups displayed bigger infarct volume and brain swelling compared to nondiabetic mice, and the increased swelling was disproportionately larger relative to infarct enlargement. Diabetic conditions significantly increased VEGF-A, Esm1, and VEGFR2 expressions in the ischemic brain compared to nondiabetic mice. Notably, in diabetic mice, VEGFR2 mRNA levels were positively correlated with brain swelling, but not with infarct volume. Treatment with SU5416 in diabetic mice significantly reduced brain swelling. The study shows that brain swelling is a predominant pathological event in diabetic stroke and that an underlying event for diabetes-enhanced brain swelling includes the activation of VEGF signaling. This study suggests consideration of stroke therapies aiming at primarily reducing brain swelling for subjects with diabetes.