Non-pharmacological strategies for the treatment of acute ischaemic stroke

A Synergistic and Efficient Thrombolytic Nanoplatform: A Mechanical Method of Blasting Combined with Thrombolytic Drugs

BACKGROUND AND OBJECTIVE

Thrombosis is a common disease that poses a great threat to life and health. Most thrombolytic effects of traditional treatments or nanomedicine are not efficient or safe enough. Therefore, we designed a nanoparticle (NP) with a combination of a phase transition material and thrombolytic drugs for efficient and safe thrombolysis.

METHODS

A thrombus fibrin-targeted and phase transition NP was designed and contained perfluorohexane (PFH) and the thrombolytic drug rtPA core, with CREKA polypeptides attached to the shell of the PLGA NPs. Characterization of the phase transition and ultrasound imaging of the NPs was carried out under low-intensity focused ultrasound (LIFU). LIFU-responsive drug release in vitro was also explored. Under the synergistic effect of PFH and rtPA, the efficient thrombolysis ability of the NPs was studied in vitro and in vivo. In vivo monitoring of thrombosis and biosafety were also verified.

RESULTS

The PPrC NPs had good ultrasound imaging ability under LIFU irradiation and were related to the phase transition characteristics of the NPs. CREKA polypeptides can effectively increase the aggregation of the NPs on thrombi. Under static and dynamic conditions in vitro, the "liquid to gas" transformation effect of PFH can perform the destruction function of the excavator at the thrombus site and promote the specific release of rtPA, and the subsequent rtPA drug thrombolysis can further fully dissolve the thrombus. In vivo experiments showed that the NPs can monitor the formation of thrombi and have good thrombolytic effects, with significantly reduced bleeding side effects. The biochemical indexes of the rats were within normal limits after treatment.

CONCLUSION

PPrC NPs loaded with PFH and rtPA combining a mechanical way of blasting with thrombolytic drugs may be a promising new and reliable approach for thrombus monitoring and treatment.

Potential mechanisms of acupuncture in enhancing cerebral perfusion of ischemic stroke

Ischemic stroke is the predominant cause of long-term disability and death worldwide. It is attributable to the sudden interruption of regional cerebral blood flow, resulting in brain cell death and neurological impairment. Acupuncture is a widely used adjuvant treatment for ischemic stroke in China and shows promising efficacy in clinical practice. This review mainly focused on the evidence to illustrate several possible mechanisms of acupuncture therapy on cerebral perfusion in ischemic stroke. Studies have shown that acupuncture is probably effective in the enhancement of cerebral perfusion after ischemic stroke. It promotes the improvement of hemodynamics, the release of vasoactive substances, the formation of new blood vessels, as well as the restitution of microcirculation. Multiple factors may contribute to the variability in acupuncture's therapeutic effects, including the acupoint selection, stimulation frequency and intensity, and retaining needle time. Acupuncture has the potential to become a non-pharmacological adjuvant approach to enhance cerebral perfusion in ischemic stroke. Future studies are required to gain our insight into acupuncture as well as accelerate its clinical translation.

Ageing as a risk factor for cerebral ischemia: Underlying mechanisms and therapy in animal models and in the clinic

Age is the only one non-modifiable risk of cerebral ischemia. Advances in stroke medicine and behavioral adaptation to stroke risk factors and comorbidities was successful in decreasing stroke incidence and increasing the number of stroke survivors in western societies. Comorbidities aggravates the outcome after cerebral ischemia. However, due to the increased in number of elderly, the incidence of stroke has increased again paralleled by an increase in the number of stroke survivors, many with severe disabilities, that has led to an increased economic and social burden in society. Animal models of stroke often ignore age and comorbidities frequently associated with senescence. This might explain why drugs working nicely in animal models fail to show efficacy in stroke survivors. Since stroke afflicts mostly the elderly comorbid patients, it is highly desirable to test the efficacy of stroke therapies in an appropriate animal stroke model. Therefore, in this review, we make parallels between animal models of stroke und clinical data and summarize the impact of ageing and age-related comorbidities on stroke outcome.

Protecting the ischaemic penumbra as an adjunct to thrombectomy for acute stroke

After ischaemic stroke, brain damage can be curtailed by rescuing the 'ischaemic penumbra' - that is, the severely hypoperfused, at-risk but not yet infarcted tissue. Current evidence-based treatments involve restoration of blood flow so as to salvage the penumbra before it evolves into irreversibly damaged tissue, termed the 'core'. Intravenous thrombolysis (IVT) can salvage the penumbra if given within 4.5 h after stroke onset; however, the early recanalization rate is only ~30%. Direct removal of the occluding clot by mechanical thrombectomy considerably improves outcomes over IVT alone, but despite early recanalization in > 80% of cases, ~50% of patients who receive this treatment do not enjoy functional independence, usually because the core is already too large at the time of recanalization. Novel therapies aiming to 'freeze' the penumbra - that is, prevent core growth until recanalization is complete - hold potential as adjuncts to mechanical thrombectomy. This Review focuses on nonpharmacological approaches that aim to restore the physiological balance between oxygen delivery to and oxygen demand of the penumbra. Particular emphasis is placed on normobaric oxygen therapy, hypothermia and sensory stimulation. Preclinical evidence and early pilot clinical trials are critically reviewed, and future directions, including clinical translation and trial design issues, are discussed.

Low-Intensity Focused Ultrasound-Responsive Phase-Transitional Nanoparticles for Thrombolysis without Vascular Damage: A Synergistic Nonpharmaceutical Strategy

Multimodal molecular imaging has shown promise as a complementary approach to thrombus detection. However, the simultaneous noninvasive detection and lysis of thrombi for cardiovascular diseases remain challenging. Herein, a perfluorohexane (PFH)-based biocompatible nanostructure was fabricated, namely, as-prepared Fe₃O₄-poly(lactic- co-glycolic acid)-PFH-CREKA nanoparticles (NPs), which combine phase transition (PT) thrombolysis capabilities with properties conducive to multimodal imaging. This well-developed PT agent responded effectively to low-intensity focused ultrasound (LIFU) by triggering the vaporization of liquid PFH to achieve thrombolysis. The presence of the CREKA peptide, which binds to the fibrin of the thrombus, allows targeted imaging and efficacious thrombolysis. Then, we found that, compared with thrombolysis using a non-phase-transition agent, PT thrombolysis can produce a robust decrease in the thrombus burden regardless of the acoustic power density of LIFU. In particular, the reduced energy for LIFU-responsive PT during the lysis process guarantees the superior safety of PT thrombolysis. After injecting the NPs intravenously, we demonstrated that this lysis process can be monitored with ultrasound and photoacoustic imaging in vivo to evaluate its efficacy. Therefore, this nonpharmaceutical strategy departs from routine methods and reveals the potential use of PT thrombolysis as an effective and noninvasive alternative to current thrombolytic therapy.

Integration of phospholipid-complex nanocarrier assembly with endogenous N-oleoylethanolamine for efficient stroke therapy

Background

Leading to more and more deaths and disabilities, stroke has become a serious threat to human health. What’s more, few effective drugs are available in clinic till now.

Results

In this research, we prepared a novel neuroprotective nanoformation (OEA–SPC NPs) via the combination of the nanoparticle drug delivery system with the endogenous N-oleoylethanolamine (OEA). By forming hydrogen bond between OEA and the carrier—soybean phosphatidylcholine (SPC), the form of OEA was turned into amorphus state when loading to the nanoparticles, which greatly improved its bioavailability. Then the following systematic experiments revealed the efficient neuroprotective effect of OEA–SPC NPs in vivo. Compared with the MCAO group, the cerebral infarct volume was reduced by 81.1%, and the edema degree by 78.4% via the oral administration of OEA–SPC NPs. And the neurological deficit scores illustrated that the MCAO rats treated with OEA–SPC NPs exhibited significantly less neurological dysfunction. The Morris water maze test indicated that the spatial learning and memory of cerebral ischemia model rats were almost recovered to the normal level. Besides, the OEA–SPC NPs could inhibit the inflammation of reperfusion to a very slight level.

Conclusions

These results suggest that the OEA–SPC NPs have a great chance to be a potential anti-stroke formation for clinic application and actually bring hope to thousands of stroke patients.

Electronic supplementary material

The online version of this article (10.1186/s12951-019-0442-x) contains supplementary material, which is available to authorized users.

Model-based assessment of the benefits and risks of recombinant tissue plasminogen activator treatment in acute ischaemic stroke

AIMS

Recombinant tissue plasminogen activator (rt-PA) is the only first-line agent approved by the US Food and Drug Administration to treat acute ischaemic stroke. However, it often causes the serious adverse event (AE) of haemorrhagic transformation. The present study developed a pharmacometric model for the rt-PA treatment effect and AE and, using the developed model, proposed a benefit-to-risk ratio assessment scheme as a supportive tool to optimize treatment outcome.

METHODS

The data from 336 acute ischaemic stroke patients were used. The treatment effect was assessed based on an improvement in National Institutes of Health Stroke Scale (NIHSS) scores, which were described using an item response theory (IRT)-based disease progression model. Treatment failure and AE probabilities, and their occurrence times, were described by incidence and time-to-event models. Using the developed model, benefit-to-risk ratios were simulated under various scenarios using the global benefit-to-risk trade-off ratio (GBR).

RESULTS

High initial NIHSS score and middle cerebral artery (MCA) stroke were risk factors for treatment failure, where the failure rate with MCA stroke was 2.87-fold higher than with non-MCA stroke. The haemorrhagic transformation time was associated with longitudinal changes in NIHSS scores. The benefit-to-risk ratio simulated was highest in minor stroke severity, with GBR >1 in all scenarios, and the ratio with non-MCA stroke was 2-3 fold higher than with MCA stroke.

CONCLUSIONS

The study demonstrated the feasibility of applying an IRT model to describing the time course of the rt-PA treatment effect and AE. Benefit-to-risk ratio analyses showed that the treatment was optimal in non-MCA stroke with minor stroke severity.

Cellular and Molecular Mechanisms Underlying Non-Pharmaceutical Ischemic Stroke Therapy in Aged Subjects

The incidence of ischemic stroke in humans increases exponentially above 70 years both in men and women. Comorbidities like diabetes, arterial hypertension or co-morbidity factors such as hypercholesterolemia, obesity and body fat distribution as well as fat-rich diet and physical inactivity are common in elderly persons and are associated with higher risk of stroke, increased mortality and disability. Obesity could represent a state of chronic inflammation that can be prevented to some extent by non-pharmaceutical interventions such as calorie restriction and hypothermia. Indeed, recent results suggest that H₂S-induced hypothermia in aged, overweight rats could have a higher probability of success in treating stroke as compared to other monotherapies, by reducing post-stroke brain inflammation. Likewise, it was recently reported that weight reduction prior to stroke, in aged, overweight rats induced by caloric restriction, led to an early re-gain of weight and a significant improvement in recovery of complex sensorimotor skills, cutaneous sensitivity, or spatial memory.

CONCLUSION

animal models of stroke done in young animals ignore age-associated comorbidities and may explain, at least in part, the unsuccessful bench-to-bedside translation of neuroprotective strategies for ischemic stroke in aged subjects.

Aging-related alterations in eNOS and nNOS responsiveness and smooth muscle reactivity of murine basilar arteries are modulated by apocynin and phosphorylation of myosin phosphatase targeting subunit-1

Aging causes major alterations of all components of the neurovascular unit and compromises brain blood supply. Here, we tested how aging affects vascular reactivity in basilar arteries from young (<10 weeks; y-BA), old (>22 months; o-BA) and old (>22 months) heterozygous MYPT1-T-696A/+ knock-in mice. In isometrically mounted o-BA, media thickness was increased by ∼10% while the passive length tension relations were not altered. Endothelial denudation or pan-NOS inhibition (100 µmol/L L-NAME) increased the basal tone by 11% in y-BA and 23% in o-BA, while inhibition of nNOS (1 µmol/L L-NPA) induced ∼10% increase in both ages. eNOS expression was ∼2-fold higher in o-BA. In o-BA, U46619-induced force was augmented (pEC50 ∼6.9 vs. pEC50 ∼6.5) while responsiveness to DEA-NONOate, electrical field stimulation or nicotine was decreased. Basal phosphorylation of MLC20-S19 and MYPT1-T-853 was higher in o-BA and was reversed by apocynin. Furthermore, permeabilized o-BA showed enhanced Ca2+-sensitivity. Old T-696A/+ BA displayed a reduced phosphorylation of MYPT1-T696 and MLC20, a lower basal tone in response to L-NAME and a reduced eNOS expression. The results indicate that the vascular hypercontractility found in o-BA is mediated by inhibition of MLCP and is partially compensated by an upregulation of endothelial NO release.

Expanding the concept of neuroprotection for acute ischemic stroke: The pivotal roles of reperfusion and the collateral circulation

This review surveys the efforts taken to achieve clinically efficacious protection of the ischemic brain and underscores the necessity of expanding our purview to include the essential role of cerebral perfusion and the collateral circulation. We consider the development of quantitative strategies to measure cerebral perfusion at the regional and local levels and the application of these methods to elucidate flow-related thresholds of ischemic viability and to characterize the ischemic penumbra. We stress that the modern concept of neuroprotection must consider perfusion, the necessary substrate upon which ischemic brain survival depends. We survey the major mechanistic approaches to neuroprotection and review clinical neuroprotection trials, focusing on those phase 3 multicenter clinical trials for acute ischemic stroke that have been completed or terminated. We review the evolution of thrombolytic therapies; consider the lessons learned from the initial, negative multicenter trials of endovascular therapy; and emphasize the highly successful positive trials that have finally established a clinical role for endovascular clot removal. As these studies point to the brain's collateral circulation as key to successful reperfusion, we next review the anatomy and pathophysiology of collateral perfusion as it relates to ischemic infarction, as well as the molecular and genetic influences on collateral development. We discuss the current MR and CT-based diagnostic methods for assessing the collateral circulation and the prognostic significance of collaterals in ischemic stroke, and we consider past and possible future therapeutic directions.

Electroacupuncture modulates stromal cell-derived factor-1α expression and mobilization of bone marrow endothelial progenitor cells in focal cerebral ischemia/reperfusion model rats

Stromal cell-derived factor-1α(SDF-1α) plays a crucial role in regulating the mobilization, migration and homing of endothelial progenitor cells(EPCs). Electroacupuncture(EA), a modern version of Traditional Chinese Medicine, can improve neurological recovery and angiogenesis in cerebral ischemic area. This study aimed to investigate the effects of electroacupuncture(EA) on the mobilization and migration of bone marrow EPCs and neurological functional recovery in rats model after focal cerebral ischemia/reperfusion and the potentially involved mechanisms. Sprague-Dawley rats received filament occlusion of the right middle cerebral artery for 2h followed by reperfusion for 12h, 1d, 2d, 3d, 7d respectively. Rats were randomly divided into sham group, model group and EA group. After 2h of the reperfusion, EA was given at the "Baihui" (GV 20)/Siguan ("Hegu" (LI 4)/"Taichong" (LR 3)) acupoints in the EA group. Modified neurological severity score (mNSS) was used to assess the neurological functional recovery. EPCs number and SDF-1α level in bone marrow(BM) and peripheral blood(PB) were detected by using fluorescence-activated cell sorting (FACS) analysis and quantitative real time polymerase chain reaction (qRT-PCR) respectively. An mNSS test showed that EA treatment significantly improved the neurological functional outcome. EPCs number in PB and BM were obviously increased in the EA group. After cerebral ischemia, the SDF-1α level was decreased in BM while it was increased in PB, which implied a gradient of SDF-1α among BM and PB after ischemia. It suggested that the forming of SDF-1α concentration gradient can induce the mobilization and homing of EPCs. Eletroacupuncture as a treatment can accelerate and increase the forming of SDF-1α concentration gradient to further induce the mobilization of EPCs and angiogenesis in ischemic brain and improve the neurological function recovery.

Impact of collaterals on the efficacy and safety of endovascular treatment in acute ischaemic stroke: a systematic review and meta-analysis

OBJECTIVE

We aimed to investigate the role of pretreatment collateral status in predicting the efficacy and safety of endovascular treatment (EVT) in acute ischaemic stroke due to cervical and/or cerebral arterial occlusions.

METHODS

Relevant full-text articles published since 1 January 2000, investigating correlations between collateral status and any efficacy or safety outcome in patients undergoing EVT in cohort or case-control studies, or randomised clinical trials, were retrieved by PubMed and manual search. Two authors extracted data from eligible studies and assessed study quality. Risk ratios (RR) were pooled for good versus poor collaterals for outcomes based on a random-effects model. Sensitivity and subgroup analyses were conducted.

RESULTS

In total, 35 (3542 participants) and 23 (2652 participants) studies were included in qualitative review and quantitative meta-analysis, respectively. Overall, good pretreatment collaterals increased the rate of favourable functional outcome at 3 months (RR=1.98, 95% CI 1.64 to 2.38; p<0.001), and reduced the risks of periprocedural symptomatic intracranial haemorrhage (RR=0.59, 95% CI 0.43 to 0.81; p=0.001) and 3-month mortality (RR=0.49, 95% CI 0.38 to 0.63; p<0.001), as compared with poor collaterals, in patients with acute ischaemic stroke under EVT. No individual study could alter the estimate of overall effect of collateral status, but there were moderate to significant heterogeneities between subgroups of studies with different modes of EVT, different arterial occlusions and different collateral grading methods.

CONCLUSIONS

Good pretreatment collateral status is associated with higher rates of favourable functional outcome, and lower rates of symptomatic intracranial haemorrhage and mortality, in patients with acute ischaemic stroke receiving endovascular therapies.

Mechanical thrombectomy for emergent large vessel occlusion: a critical appraisal of recent randomized controlled clinical trials

BACKGROUND AND PURPOSE

After numerous attempts to prove efficacy for endovascular treatment of ischemic stroke, a series of recent randomized controlled clinical trials (RCTs) established fast mechanical thrombectomy (MT) as a safe and effective novel treatment for emergent large vessel occlusion (ELVO) in the anterior cerebral circulation.

METHODS

We reviewed five recent RCTs that evaluated the safety and efficacy of MT in ELVO patients and captured available information on recanalization/reperfusion, symptomatic intracranial hemorrhage (sICH), clinical outcome, and mortality. MT was performed with stent retrievers, aspiration techniques, or a combination of these endovascular approaches. We applied meta-analytical methodology to evaluate the pooled effect of MT on recanalization/reperfusion, sICH, functional independence (modified Rankin scale score of 0-2) and 3-month mortality rates in comparison to best medical therapy (BMT).

RESULTS

MT was associated with increased likelihood of complete recanalization/reperfusion (RR: 2.22; 95%CI: 1.89-2.62; P < 0.00001) and 3-month functional independence (RR: 1.72; 95%CI: 1.48-1.99; P < 0.00001) without any heterogeneity across trials (I (2) = 0%). The absolute benefit increase in MT for complete recanalization/reperfusion and functional independence was 44 (NNT = 2) and 16 (NNT = 6), respectively. MT was not associated with increased risk of 3-month mortality (15% with MT vs. 19% with BMT) and sICH (4.6% with MT vs. 4.3% with BMT), while small heterogeneity was detected across the included trials (I (2) < 25%).

CONCLUSIONS

MT is a safe and highly effective treatment for patients with ELVO in the anterior circulation. For every six ELVO patients treated with MT three more will achieve complete recanalization at 24 h following symptom onset and one more will be functionally independent at 3 months in comparison to BMT.

Twenty-four hours hypothermia has temporary efficacy in reducing brain infarction and inflammation in aged rats

Stroke is a major cause of disability for which no neuroprotective measures are available. Age is the principal nonmodifiable risk factor for this disease. Previously, we reported that exposure to hydrogen sulfide for 48 hours after stroke lowers whole body temperature and confers neuroprotection in aged animals. Because the duration of hypothermia in most clinical trials is between 24 and 48 hours, we questioned whether 24 hours exposure to gaseous hypothermia confers the same neuroprotective efficacy as 48 hours exposure. We found that a shorter exposure to hypothermia transiently reduced both inflammation and infarct size. However, after 1 week, the infarct size became even larger than in controls and after 2 weeks there was no beneficial effect on regenerative processes such as neurogenesis. Behaviorally, hypothermia also had a limited beneficial effect. Finally, after hydrogen sulfide-induced hypothermia, the poststroke aged rats experienced a persistent sleep impairment during their active nocturnal period. Our data suggest that cellular events that are delayed by hypothermia in aged rats may, in the long term, rebound, and diminish the beneficial effects.

Therapeutic hypothermia applicable to cardiac surgery

OBJECTIVE

To review the beneficial and adverse effects of therapeutic hypothermia (TH) applicable to cardiac surgery with cardiopulmonary bypass (CPB) in the contexts of various temperature levels and techniques for achieving TH.

DATABASES USED

Multiple electronic literature searches were performed using PubMed and Google for articles published from June 2012 to December 2014. Relevant terms (e.g. 'hypothermia', 'cardiopulmonary bypass', 'cardiac surgery', 'neuroprotection') were used to search for original articles, letters and reviews without species limitation. Reviews were included despite potential publication bias. References from the studies identified were also searched to find other potentially relevant citations. Abstracts, case reports, conference presentations, editorials and expert opinions were excluded.

CONCLUSIONS

Therapeutic hypothermia is an essential measure of neuroprotection during cardiac surgery that may be achieved most effectively by intravascular cooling using hypothermic CPB. For most cardiac surgical procedures, mild to modest (32-36 °C) TH will be sufficient to assure neuroprotection and will avoid most of the adverse effects of hypothermia that occur at lower body core temperatures.

Every 15-Min Delay in Recanalization by Intra-Arterial Therapy in Acute Ischemic Stroke Increases Risk of Poor Outcome

Background

Intra-arterial therapy has improved recanalization rates compared with intravenous thrombolysis for acute ischemic stroke; however, superior clinical efficacy has not been convincingly demonstrated. Time to recanalization is postulated as a mechanism hindering the efficacy of intra-arterial therapy.

Aim

To investigate the effects of time to recanalization on clinical outcome postintra-arterial therapy for acute ischemic stroke.

Methods

Clinical data were collected prospectively for consecutive patients undergoing intra-arterial therapy for acute ischemic stroke at a single center between 2009 and 2013. Ninety-day functional outcome was assessed by the modified Rankin scale. Univariate analyses identified candidate clinical variables for inclusion in the multivariable model; multivariable logistic regression analyses identified variables independently associated with good outcome, defined as modified Rankin scale 0–2.

Results

One hundred and seven patients were included in the analysis. Median (interquartile range) age was 67 (54–77) years, 41 (38%) were female, and median (interquartile range) baseline National Institute of Health Stroke Severity score was 18 (13–22). Median time from symptom onset to recanalization was 330 min (interquartile range 277–397). Fifty-four (50%) patients achieved a favorable modified Rankin scale at 90 days. Age, successful recanalization, and time to recanalization were independently associated with good outcome at 90 days in multivariable logistic regression analysis. For every 15 min delay in recanalization, the odds of good outcome decreased by 10%.

Conclusions

Longer time to recanalization was associated with poorer functional outcome post intra-arterial therapy. We recommend that a systematic approach to minimize time delay to treatment is warranted in intra-arterial therapy for acute ischemic stroke.

5'-adenosine monophosphate-induced hypothermia attenuates brain ischemia/reperfusion injury in a rat model by inhibiting the inflammatory response

Hypothermia treatment is a promising therapeutic strategy for brain injury. We previously demonstrated that 5′-adenosine monophosphate (5′-AMP), a ribonucleic acid nucleotide, produces reversible deep hypothermia in rats when the ambient temperature is appropriately controlled. Thus, we hypothesized that 5′-AMP-induced hypothermia (AIH) may attenuate brain ischemia/reperfusion injury. Transient cerebral ischemia was induced by using the middle cerebral artery occlusion (MCAO) model in rats. Rats that underwent AIH treatment exhibited a significant reduction in neutrophil elastase infiltration into neuronal cells and matrix metalloproteinase 9 (MMP-9), interleukin-1 receptor (IL-1R), tumor necrosis factor receptor (TNFR), and Toll-like receptor (TLR) protein expression in the infarcted area compared to euthermic controls. AIH treatment also decreased the number of terminal deoxynucleotidyl transferase dUTP nick end labeling- (TUNEL-) positive neuronal cells. The overall infarct volume was significantly smaller in AIH-treated rats, and neurological function was improved. By contrast, rats with ischemic brain injury that were administered 5′-AMP without inducing hypothermia had ischemia/reperfusion injuries similar to those in euthermic controls. Thus, the neuroprotective effects of AIH were primarily related to hypothermia.

Acute neuroinflammation in a clinically relevant focal cortical ischemic stroke model in rat: longitudinal positron emission tomography and immunofluorescent tracking

Adequate estimation of neuroinflammatory processes following ischemic stroke is essential for better understanding of disease mechanisms, and for the development of treatment strategies. With the TSPO (18 kDa translocator protein) positron emission tomography (PET) radioligand [(11)C]PBR28, we monitored longitudinally the inflammatory response post-transient cerebral ischemia in rats, using a recently developed rat stroke model that produces isolated focal cortical infarcts with clinical relevance in size and pathophysiology. Six Sprague-Dawley rats were subjected to 90 min transient endovascular occlusion of the M2 segment of the middle cerebral artery (M2CAO). Animals were imaged with a nanoScan(®) PET/MRI system at 1, 4, 7 and 14 days after M2CAO with a bolus injection of [(11)C]PBR28. In the infarct region, we found a significantly increased uptake of [(11)C]PBR28 on day 4, 7 and 14 compared to day 1 as well as compared to the contralateral cortex. No significant increase was detected in the contralateral cortex during the 14 days of imaging. The activation in the infarct region gradually decreased between day 4 and day 14. In an additional group of animals (n = 26), immunofluorescence studies were performed with antibodies for activated microglia/monocytes (Cd11b), phagocytes (Cd68), astrocytes (glial fibrillary acidic protein) and TSPO. The TSPO immunofluorescence signal indicated reactive microgliosis post injury, corresponding to PET findings. The present clinically relevant animal model and TSPO PET ligand appear to be well suited for studies on neuroinflammation after ischemic stroke.

The effects of poststroke aerobic exercise on neuroplasticity: a systematic review of animal and clinical studies

Aerobic exercise may be a catalyst to promote neuroplasticity and recovery following stroke; however, the optimal methods to measure neuroplasticity and the effects of training parameters have not been fully elucidated. We conducted a systematic review and synthesis of clinical trials and studies in animal models to determine (1) the extent to which aerobic exercise influences poststroke markers of neuroplasticity, (2) the optimal parameters of exercise required to induce beneficial effects, and (3) consistent outcomes in animal models that could help inform the design of future trials. Synthesized findings show that forced exercise at moderate to high intensity increases brain-derived neurotrophic factor (BDNF), insulin-like growth factor-I (IGF-I), nerve growth factor (NGF), and synaptogenesis in multiple brain regions. Dendritic branching was most responsive to moderate rather than intense training. Disparity between clinical stroke and stroke models (timing of initiation of exercise, age, gender) and clinically viable methods to measure neuroplasticity are some of the areas that should be addressed in future research.

Comparative efficacy of different acute reperfusion therapies for acute ischemic stroke: a comprehensive benefit-risk analysis of clinical trials

BACKGROUND

Numerous acute reperfusion therapies (RPT) are currently investigated as potential new therapeutic targets in acute ischemic stroke (AIS). We conducted a comprehensive benefit-risk analysis of available clinical studies assessing different acute RPT, and investigated the utility of each intervention in comparison to standard intravenous thrombolysis (IVT) and in relation to the onset-to-treatment time (OTT).

METHODS

A comprehensive literature search was conducted to identify all available published, peer-reviewed clinical studies that evaluated the efficacy of different RPT in AIS. Benefit-to-risk ratio (BRR), adjusted for baseline stroke severity, was estimated as the percentage of patients achieving favorable functional outcome (BRR1, mRS score: 0-1) or functional independence (BRR2, mRS score: 0-2) at 3 months divided by the percentage of patients who died during the same period.

RESULTS

A total of 18 randomized (n = 13) and nonrandomized (n = 5) clinical studies fulfilled our inclusion criteria. IV therapy with tenecteplase (TNK) was found to have the highest BRRs (BRR1 = 5.76 and BRR2 = 6.82 for low-dose TNK; BRR1 = 5.80 and BRR2 = 6.87 for high-dose TNK), followed by sonothrombolysis (BRR1 = 2.75 and BRR2 = 3.38), while endovascular thrombectomy with MERCI retriever was found to have the lowest BRRs (BRR1 range, 0.31-0.65; BRR2 range, 0.52-1.18). A second degree negative polynomial correlation was detected between favorable functional outcome and OTT (R (2) value: 0.6419; P < 0.00001) indicating the time dependency of clinical efficacy of all reperfusion therapies.

CONCLUSION

Intravenous thrombolysis (IVT) with TNK and sonothrombolysis have the higher BRR among investigational reperfusion therapies. The combination of sonothrombolysis with IV administration of TNK appears a potentially promising therapeutic option deserving further investigation.

Predictors of outcome after mechanical thrombectomy for anterior circulation large vessel occlusion in patients aged ≥80 years

BACKGROUND

There is uncertainty about the role of endovascular recanalization procedures for the treatment of acute ischemic stroke in patients aged ≥80 years. Therefore, careful patient selection is mandatory. Our aim was to find valid predictors of clinical outcome after mechanical thrombectomy (mTE) based on the sparse information available in the emergency setting.

METHODS

We included consecutive patients aged ≥80 years treated by mTE for anterior circulation thromboembolic vessel occlusion in our department between January 2008 and January 2013. Successful recanalization was defined as a thrombolysis in cerebral infarction (TICI) score of 2b or 3. The rates of parenchymal hemorrhage types I (PHI) and II (PHII) according to the ECASS definition and the rate of focal and diffuse subarachnoid hemorrhage (SAH) were reported. A modified Ranking scale (mRS) score of 0-2 at 90 days was defined as a favorable outcome. We evaluated the influence of gender, smoking habits, atrial fibrillation, diabetes, hypertension, hyperlipidemia, coronary artery and peripheral artery disease, National Institutes of Health Stroke Scale (NIHSS) score, Totaled Health Risks in Vascular Events (THRIVE) score, Alberta Stroke Program Early CT Score (ASPECTS), and duration of symptoms on favorable outcome. Significant predictors were then included in a stepwise logistic regression analysis. Odds ratios (OR), 95% confidence intervals (CI), and receiver operating characteristics (ROC) curves were calculated. p < 0.05 was considered statistically significant.

RESULTS

In the defined period, we treated 109 patients aged ≥80 years with 116 occluded anterior circulation target vessels. Successful recanalization was achieved in 87.9% of the targets. The rates of PHI, PHII, and focal and diffuse SAH were 6.4, 5.5, 12.8, and 7.3%, with an overlap between PH and SAH. The combined rate of PHII and/or diffuse SAH was 9.2%. Despite good recanalization rates and reasonable rates of hemorrhage, only 19 patients (17.4%) were functionally independent at 90 days. An additional 12 patients (11.0%) suffered from moderate disability (mRS score 3), 26 (23.9%) were severely disabled (mRS score 4-5) and 52 (47.7%) were deceased. NIHSS, ASPECTS, and THRIVE scores significantly predicted a favorable outcome. Stepwise logistic regression identified NIHSS (OR 0.89; 95% CI 0.82-0.96; p = 0.009) and ASPECTS (OR 2.27; 95% CI 1.28-4.02; p = 0.005) as independent predictors. The ROC area was 0.81.

CONCLUSION

ASPECTS and NIHSS were independent predictors of a favorable outcome in patients aged ≥80 years after mTE for anterior circulation large vessel occlusion and may support decision making with regard to the treatment modality. Since the chances of gaining functional independence are limited, careful consideration of each individual case is mandatory. Further studies comparing endovascular and standard treatment in octogenarians are warranted.