Long-term survival in permanent middle cerebral artery occlusion: a model of malignant stroke in rats

Non-invasive Deep-Brain Imaging with 3D Integrated Photoacoustic Tomography and Ultrasound Localization Microscopy (3D-PAULM)

Photoacoustic computed tomography (PACT) is a proven technology for imaging hemodynamics in deep brain of small animal models. PACT is inherently compatible with ultrasound (US) imaging, providing complementary contrast mechanisms. While PACT can quantify the brain's oxygen saturation of hemoglobin (sO2), US imaging can probe the blood flow based on the Doppler effect. Further, by tracking gas-filled microbubbles, ultrasound localization microscopy (ULM) can map the blood flow velocity with sub-diffraction spatial resolution. In this work, we present a 3D deep-brain imaging system that seamlessly integrates PACT and ULM into a single device, 3D-PAULM. Using a low ultrasound frequency of 4 MHz, 3D-PAULM is capable of imaging the whole-brain hemodynamic functions with intact scalp and skull in a totally non-invasive manner. Using 3D-PAULM, we studied the mouse brain functions with ischemic stroke. Multi-spectral PACT, US B-mode imaging, microbubble-enhanced power Doppler (PD), and ULM were performed on the same mouse brain with intrinsic image co-registration. From the multi-modality measurements, we future quantified blood perfusion, sO2, vessel density, and flow velocity of the mouse brain, showing stroke-induced ischemia, hypoxia, and reduced blood flow. We expect that 3D-PAULM can find broad applications in studying deep brain functions on small animal models.

Long-Term Functionality Prediction for First Time Ischemic Middle Cerebral Artery Stroke Patients Receiving Conventional Medical Treatment

BACKGROUND

Middle cerebral artery (MCA) ischemic stroke poses a major threat to human beings and prompts intravenous thrombolytic and/or thrombectomy management remains the gold standard treatment. However, not all MCA stroke patients fit in the inclusion and exclusion criteria that many patients only receive conventional medical therapy. We attempt to seek the baseline parameters that can effectively predict patients' long-term functionality, as well as hypothesizing that the carotid duplex derived resistance/pulsatility index might be capable of fulfilling this purpose.

METHODS

The 741 MCA ischemic stroke patients have been retrospectively recruited for the project. Under the initial screening, matching the inclusion and exclusion criteria, there are 471 participants to be enrolled in the study. The patients' basic information, along with outcome assessments, pre-admission Barthel index and NIHSS score, and pre- and post-treatment mRS are recorded. All statistical analyses were performed using R for Windows (version 3.6.3). The significance level was set at P < 0.05 for all analyses.

RESULTS

Of the 471 patients, 239 participants show a net mRS improvement, whereas the other 232 show deterioration. Hyperlipidaemia, chronic kidney disease, and dementia are related to long-term functionality improvement. The multivariate logistic regression analysis shows that right common carotid artery (CCA) resistance index (RI) and ischemic heart disease play a significant role in favourable outcome functionality. The ROC and Youden Index models are formulated, and it shows that Barthel Index and the NIHSS are most significant in the outcome measurement group (AUC: 0.675, 0.653; cut-off point: 57.5, 3.5, respectively). The right-side CCA RI is the solely important outcome predictor for the baseline carotid duplex study (AUC: 0.5; cut-off point: 0.785).

CONCLUSION

The favourable long-term functionality of MCA ischemic stroke patients receiving conventional medical treatment seems to correlate fairly with pre-admission NIHSS and Barthel index scores. Underlying hyperlipidaemia, chronic kidney disease, and dementia are conversely associated with favourable long-term capability. Moreover, the value of CCA RI appears to significantly alter the long-term outcomes in this group of patients.

Levetiracetam effect on behavioral and electrophysiological parameters in rat model of global brain ischemia

Post-stroke paroxysmal activity is a neurophysiological indicator of epileptogenesis and increase of seizure susceptibility, so treatments with neuroprotective activity and anti-paroxysmal activity can be more beneficial during post-ischemic period. The goal of this study was evaluation of levetiracetam (100 mg/kg, 7 days of administration) effect on behavior and brain bioelectric activity changes in the post-ischemic period. Global ischemia model was carried out with bilateral ligation of carotid arteries in rats. Neurological deficit and electrophysiological changes of brain structures (striatum, cortex, hypothalamus, hippocampus) were analyzed during 28 days. Paroxysmal activity was not observed on the 1st day after ischemia and had early (2nd day) and late (28th day) onsets. Spectral analysis showed that rats, that died by the 10th day, had delta wave increase and theta decrease on the 1st day and delta activity reduction on the 2-7th days. LEV did not affect survival rate, however, it contributed to neurological disorder regression towards lighter forms on the 1st day after ischemia. It suppressed paroxysmal activity with an early onset and affected delta and theta waves on the 1st day in all structures except hippocampus. On the 7th and 28th days LEV increased delta activity due to 1-3 Hz frequency. Thus, LEV eliminates early onset post-ischemic paroxysmal activity and contributes to normalization of delta waves activity on the 1st day after ischemia, that positively affects neurological status of animals in post-ischemic period. It allows one to make a conclusion about possible LEV application in the post-ischemic period.

Edaravone-Loaded Macrophage-Derived Exosomes Enhance Neuroprotection in the Rat Permanent Middle Cerebral Artery Occlusion Model of Stroke

Edaravone (Edv) can inhibit tissue damage, cause cerebral edema, and delay neuronal death caused by acute cerebral infarction. Exosomes are considered as cargo carriers for intercellular communication and serve as important regulators in many pathological processes. Here, we developed macrophage-derived exosomes (Exo) containing Edv (Exo + Edv) to improve the bioavailability of Edv and enhance the neuroprotective effects in a rat model of permanent middle cerebral artery occlusion (PMCAO). The results showed that Exo + Edv significantly improved the bioavailability of Edv and prolonged half-life (t_1/2). At the same time, Exo + Edv made Edv more easily reach the ischemic side of rats with PMCAO and was localized with neuronal cells and microglia, thus reducing the death of neuronal cells and promoting the polarization of microglia from M1 to M2. Taken together, Exo + Edv may become a potential clinical treatment option for PMCAO.

Considering risk factors for the effectiveness of translational therapies in brain stroke

Multiple studies on cerebral ischemia have been performed in animal models to propose different strategies of neuroprotection that mitigate either the early or late consequences of the disease. These therapies have been successful in reducing the volume of infarction, the proinflammatory cascade, and the amount of free radicals, as well as reversing markers of neurodegeneration, among other events. However, when those strategies are translated to clinical studies, their effectiveness is not reproduced. This review will focus on highlighting some of the main limitations of the animal models of stroke that lead to unsuccessful translational therapies and the common risk factors in humans that should be carefully considered in the experimental design of future studies to generate a more realistic spatiotemporal physiopathology and improve therapeutic efficacy in cerebral ischemia.

The Beneficial Effects of Raffinee in Permanent Occulted Stroke Mice

Ischemic stroke is a major cause of disability and mortality globally. Although thrombolytic therapy is routinely adopted in cases of ischemic stroke, various alternative natural neuroprotectants are also used as effective adjuvant therapies to recover neurofunction following ischemic stroke. Raffinee, a natural fermented product with strong antioxidant and neuroprotective activities, has antiatherogenic effects in animals and has exhibited neuroprotective effects in a clinical trial by recovering motor and sensory function following spinal cord lesion. This study reveals the advantageous effects of Raffinee on PC12 cells by decreasing hypoxia-induced apoptosis in mice with permanent middle cerebral artery occlusion (pMCAO) by increasing the levels of neurotrophic factors such as S100β, reducing serum inflammatory factors such as matrix metalloproteinases (MMP)-9/MMP-2 ratio, tumor necrosis factor-α, and interleukin (IL)-6 level, and increasing IL-10 levels. Significantly reduced brain infarct volume along with a favorable survival ratio was observed for pMCAO mice that received Raffinee, suggesting a neuroprotective potential of Raffinee in cases of acute ischemic stroke by suppressing apoptosis.

Delayed Recanalization Promotes Functional Recovery in Rats Following Permanent Middle Cerebral Artery Occlusion

Most large vessel stroke patients have permanent occlusion, for which there are no current treatment options. Recent case studies have indicated delayed recanalization, that is recanalization outside of the 6-h treatment window, may lead to improved outcome. We hypothesized that delayed recanalization will restore cerebral blood flow, leading to improved function in rats. Male SD rats were subjected to pMCAO or sham surgery. Delayed recanalization was performed on either day 3, 7, or 14 after pMCAO in a subset of animals. Cerebral blood flow was monitored during suture insertion, during recanalization, and then at sacrifice. Neurological function was evaluated for 1 week after delayed recanalization and at 4 weeks post-ictus. After sacrifice, cerebral morphology was measured. Compared to no treatment, delayed recanalization restored cerebral blood flow, leading to sensorimotor recovery, improved learning and memory, reduced infarct volume, and increased neural stem/progenitor cells within the infarction. The data indicate that earlier delayed recanalization leads to better functional and histological recovery. Yet, even restoring cerebral blood flow 14 days after pMCAO allows for rats to regain sensorimotor function. This exploratory study suggests that delayed recanalization may be a viable option for treatment of permanent large vessel stroke.

Animal models of ischaemic stroke and characterisation of the ischaemic penumbra

Over the past forty years, animal models of focal cerebral ischaemia have allowed us to identify the critical cerebral blood flow thresholds responsible for irreversible cell death, electrical failure, inhibition of protein synthesis, energy depletion and thereby the lifespan of the potentially salvageable penumbra. They have allowed us to understand the intricate biochemical and molecular mechanisms within the 'ischaemic cascade' that initiate cell death in the first minutes, hours and days following stroke. Models of permanent, transient middle cerebral artery occlusion and embolic stroke have been developed each with advantages and limitations when trying to model the complex heterogeneous nature of stroke in humans. Yet despite these advances in understanding the pathophysiological mechanisms of stroke-induced cell death with numerous targets identified and drugs tested, a lack of translation to the clinic has hampered pre-clinical stroke research. With recent positive clinical trials of endovascular thrombectomy in acute ischaemic stroke the stroke community has been reinvigorated, opening up the potential for future translation of adjunctive treatments that can be given alongside thrombectomy/thrombolysis. This review discusses the major animal models of focal cerebral ischaemia highlighting their advantages and limitations. Acute imaging is crucial in longitudinal pre-clinical stroke studies in order to identify the influence of acute therapies on tissue salvage over time. Therefore, the methods of identifying potentially salvageable ischaemic penumbra are discussed. This article is part of the Special Issue entitled 'Cerebral Ischemia'.

A multiparameter model predicting in-hospital mortality in malignant cerebral infarction

The early identification of patients with large hemisphere infarctions (LHIs) at risk of fatal brain edema may result in better outcomes. A quantitative model using parameters obtained at admission may be a predictor of in-hospital mortality from LHI.This prospective study enrolled all patients with LHI involving >50% of the middle cerebral artery (MCA) admitted to our neurological intensive care unit within 48 hours of symptom onset. Early clinical and radiographic parameters and the baseline CHADS2 score (congestive heart failure, hypertension, age ≥ 75 years, diabetes mellitus, stroke [double weight]) were analyzed regarding their ability to predict patient outcomes.Seventy-seven patients with LHIs were identified, 33 (42.9%) with complete MCA infarction (CMCA), and 44 (57.1%) with incomplete MCA infarction (IMCA). The predictors of CMCA score included: >1/3 early hypodensity in computed tomography findings, hyperdense MCA sign, brain edema, initial National Institutes of Health Stroke Scale (NIHSS) score ≥17, and stroke in progression during the 1st 5 days of admission. The cutoff CMCA score was 2, with a sensitivity of 81.8% and specificity of 70.5%. Mortality score 1, used for predicting in-hospital mortality from LHI, included CMCA and CHADS2 scores ≥4 (sensitivity 100.0%, specificity 57.4%), and mortality score 2 included CMCA and CHADS2 scores ≥4, and NIHSS score ≥26, during the 1st 5 days (sensitivity 100.0%, specificity 91.7%).Patients qualifying for a mortality score of 2 were at high-risk of in-hospital mortality from LHI. These findings may aid in identifying patients who may benefit from invasive therapeutic strategies, and in better describing the characteristics of those at risk of mortality.

Bone Marrow Stromal Cells Combined With Sodium Ferulate and n-Butylidenephthalide Promote the Effect of Therapeutic Angiogenesis via Advancing Astrocyte-Derived Trophic Factors After Ischemic Stroke

Being a potential candidate for stroke treatment, bone marrow-derived mesenchymal stem/stromal cells (BM-MSCs) have been demonstrated to be able to enhance angiogenesis and proliferation of reactive astrocytes, which subsequently leads to the amelioration of neurological injury. Increasing evidence further indicates that combining BM-MSCs with certain agents, such as simvastatin, may improve therapeutic effects. Sodium ferulate (SF) and n-butylidenephthalide (BP), two main components of Radix Angelica Sinensis, are proven to be important regulators of stem cells in cell migration, differentiation, and pluripotency maintenance. This study aimed to investigate whether combining BM-MSCs with SF and BP had better therapeutic effect in the treatment of stroke, and the underlying molecular basis for the therapeutic effects was also investigated. The results showed that combination treatment notably reduced neurological injury after stroke and increased the expression of astrocyte-derived vascular endothelial growth factor (VEGF), brain-derived neurotrophic factor (BDNF), and von Willebrand factor-positive vascular density in the ischemic boundary zone as evaluated by immunofluorescence staining. After treatment with BM-MSCs plus SF and BP, astrocytes showed increased expression of VEGF and BDNF by upregulating protein kinase B/mammalian target of rapamycin (AKT/mTOR) expression in an oxygen- and glucose-deprived (OGD) environment. Human umbilical vein endothelial cells (HUVECs) incubated with the conditioned medium (CM) derived from OGD astrocytes treated with BM-MSCs plus SF and BP showed significantly increased migration and tube formation compared with those incubated with the CM derived from OGD astrocytes treated with BM-MSCs alone. These results demonstrate that combination treatment enhances the expression of astrocyte-derived VEGF and BDNF, which contribute to angiogenesis after cerebral ischemia, and the underlying mechanism is associated with activation of the astrocytic AKT/mTOR signaling pathway. Our study provides a potential therapeutic approach for ischemic stroke.