Critical differences between two classical surgical approaches for middle cerebral artery occlusion-induced stroke in mice

Assessing the effects of aging on the Koizumi's and Zea Longa's methods and their suitability as mouse models for evaluating neurodegeneration post-ischemic stroke: A comparative study

Koizumi's and Zea Longa's middle cerebral artery occlusion (MCAO) models (KMCAO and LMCAO) are commonly used methods in rodent ischemic stroke research. A key distinction between them lies in whether the blood flow through the common carotid artery (CCA) is maintained. Limited evidence exists regarding the systematic comparison of their pathophysiological characteristics, particularly considering the age of experimental mice. In this study, cerebral infarction outcomes were analyzed in mice aged 3, 6, 9, and 12 months. Mice aged 3-6 months exhibited minor cerebral infarction with KMCAO but substantial infarction with LMCAO, whereas differences diminished in 9-12-month-old mice. Comparable infarct severity in 3-month-old mice was achieved by inducing ischemia for 1.5 hours using KMCAO and for 1 hour using LMCAO, suggesting potential mechanistic similarities, subject to further research. LMCAO led to reperfusion injury due to preserved CCA perfusion, whereas KMCAO provided controlled ischemic insult via continuous CCA ligation. Both models confirmed that increased brain damage correlated with decreased neuronal nuclei expression and increased glial fibrillary acidic protein expression. These findings highlight the importance of selecting the MCAO model based on experimental objectives, age, and ischemia duration for the accurate modeling of ischemic and degenerative brain injury.

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.

Neuroprotective effects of methanolic extract from Chuanxiong Rhizoma in mice with middle cerebral artery occlusion-induced ischemic stroke: suppression of astrocyte- and microglia-related inflammatory response

BACKGROUND

In traditional Asian medicine, dried rhizomes of Ligusticum chuanxiong Hort. (Chuanxiong Rhizoma [CR]) have long been used to treat pain disorders that affect the head and face such as headaches. Furthermore, they have been used primarily for blood circulation improvement or as an analgesic and anti-inflammatory medicine. This study aimed to investigate the neuroprotective effects of a methanol extract of CR (CRex) on ischemic stroke in mice caused by middle cerebral artery occlusion (MCAO).

METHODS

C57BL/6 mice were given a 1.5-h transient MCAO (MCAO control and CRex groups); CRex was administered in the mice of the CRex group at 1,000-3,000 mg/kg either once (single dose) or twice (twice dose) before MCAO. The mechanism behind the neuroprotective effects of CRex was examined using the following techniques: brain infarction volume, edema, neurological deficit, novel object recognition test (NORT), forepaw grip strength, and immuno-fluorescence staining.

RESULTS

Pretreating the mice with CRex once at 1,000 or 3,000 mg/kg and twice at 1,000 mg/kg 1 h before MCAO, brought about a significantly decrease in the infarction volumes. Furthermore, pretreating mice with CRex once at 3,000 mg/kg 1 h before MCAO significantly suppressed the reduction of forepaw grip strength of MCAO-induced mice. In the MCAO-induced group, preadministration of CRex inhibited the reduction in the discrimination ratio brought on by MCAO in a similar manner. CRex exhibited these effects by suppressing the activation of astrocytes and microglia, which regulated the inflammatory response.

CONCLUSIONS

This study proposes a novel development for the treatment of ischemic stroke and provides evidence favoring the use of L. chuanxiong rhizomes against ischemic stroke.

Distinctions between the Koizumi and Zea Longa methods for middle cerebral artery occlusion (MCAO) model: a systematic review and meta-analysis of rodent data

Ischemic stroke in rodents is usually induced by intraluminal middle cerebral artery occlusion (MCAO) via the common carotid artery plugging filament invented by Koizumi et al. (MCAO-KM), or the external carotid artery plugging filament created by Zea Longa et al. (MCAO-LG). A systematic review of the distinctions between them is currently lacking. Here, we performed a meta-analysis in terms of model establishment, cerebral blood flow (CBF), and cerebral ischemia-reperfusion injury (CIRI) between them, Weighted Mean Differences and Standardized Mean Difference were used to analyze the combined effects, Cochrane's Q test and the I2 statistic were applied to determine heterogeneity, sensitivity analysis and subgroup analysis were performed to explore the source of heterogeneity. Literature mining suggests that MCAO-KM brings shorter operation time (p = 0.007), higher probability of plugging filament (p < 0.001) and molding establishment (p = 0.006), lower possibility of subarachnoid hemorrhage (p = 0.02), larger infarct volume (p = 0.003), severer brain edema (p = 0.002), and neurological deficits (p = 0.03). Nevertheless, MCAO-LG shows a more adequate CBF after ischemia-reperfusion (p < 0.001), a higher model survival rate (p = 0.02), and a greater infarct rate (p = 0.007). In conclusion, the MCAO-KM method is simple to operate with a high modeling success rate, and is suitable for the study of brain edema under long-term hypoperfusion, while the MCAO-LG method is highly challenging for novices, and is suitable for the study of CIRI caused by complete ischemia-reperfusion. These findings are expected to benefit the selection of intraluminal filament MCAO models before undertaking ischemic stroke preclinical effectiveness trials.

Preclinical models of middle cerebral artery occlusion: new imaging approaches to a classic technique

Stroke remains a major burden on patients, families, and healthcare professionals, despite major advances in prevention, acute treatment, and rehabilitation. Preclinical basic research can help to better define mechanisms contributing to stroke pathology, and identify therapeutic interventions that can decrease ischemic injury and improve outcomes. Animal models play an essential role in this process, and mouse models are particularly well-suited due to their genetic accessibility and relatively low cost. Here, we review the focal cerebral ischemia models with an emphasis on the middle cerebral artery occlusion technique, a "gold standard" in surgical ischemic stroke models. Also, we highlight several histologic, genetic, and in vivo imaging approaches, including mouse stroke MRI techniques, that have the potential to enhance the rigor of preclinical stroke evaluation. Together, these efforts will pave the way for clinical interventions that can mitigate the negative impact of this devastating disease.

Comparative Investigation of Expression of Glutamatergic and GABAergic Genes in the Rat Hippocampus after Focal Brain Ischemia and Central LPS Administration

Among the responses in the early stages of stroke, activation of neurodegenerative and proinflammatory processes in the hippocampus is of key importance for the development of negative post-ischemic functional consequences. However, it remains unclear, what genes are involved in these processes. The aim of this work was a comparative study of the expression of genes encoding glutamate and GABA transporters and receptors, as well as inflammation markers in the hippocampus one day after two types of middle cerebral artery occlusion (according to Koizumi et al. method, MCAO-MK, and Longa et al. method, MCAO-ML), and direct pro-inflammatory activation by central administration of bacterial lipopolysaccharide (LPS). Differences and similarities in the effects of these challenges on gene expression were observed. Expression of a larger number of genes associated with activation of apoptosis and neuroinflammation, glutamate reception, and markers of the GABAergic system changed after the MCAO-ML and LPS administration than after the MCAO-MK. Compared with the MCAO-ML, the MCAO-MK and LPS challenges caused changes in the expression of more genes involved in glutamate transport. The most pronounced difference between the responses to different challenges was the changes in expression of calmodulin and calmodulin-dependent kinases genes observed after MCAO, especially MCAO-ML, but not after LPS. The revealed specific features of the hippocampal gene responses to the two types of ischemia and a pro-inflammatory stimulus could contribute to further understanding of the molecular mechanisms underlying diversity of the post-stroke consequences both in the model studies and in the clinic.

A retrospect and outlook on the neuroprotective effects of anesthetics in the era of endovascular therapy

Studies on the neuroprotective effects of anesthetics were carried out more than half a century ago. Subsequently, many cell and animal experiments attempted to verify the findings. However, in clinical trials, the neuroprotective effects of anesthetics were not observed. These contradictory results suggest a mismatch between basic research and clinical trials. The Stroke Therapy Academic Industry Roundtable X (STAIR) proposed that the emergence of endovascular thrombectomy (EVT) would provide a proper platform to verify the neuroprotective effects of anesthetics because the haemodynamics of patients undergoing EVT is very close to the ischaemia–reperfusion model in basic research. With the widespread use of EVT, it is necessary for us to re-examine the neuroprotective effects of anesthetics to guide the use of anesthetics during EVT because the choice of anesthesia is still based on team experience without definite guidelines. In this paper, we describe the research status of anesthesia in EVT and summarize the neuroprotective mechanisms of some anesthetics. Then, we focus on the contradictory results between clinical trials and basic research and discuss the causes. Finally, we provide an outlook on the neuroprotective effects of anesthetics in the era of endovascular therapy.

Re-Exploring the Inflammation-Related Core Genes and Modules in Cerebral Ischemia

The genetic transcription profile of brain ischemic and reperfusion injury remains elusive. To address this, we used an integrative analysis approach including differentially expressed gene (DEG) analysis, weighted-gene co-expression network analysis (WGCNA), and pathway and biological process analysis to analyze data from the microarray studies of nine mice and five rats after middle cerebral artery occlusion (MCAO) and six primary cell transcriptional datasets in the Gene Expression Omnibus (GEO). (1) We identified 58 upregulated DEGs with more than 2-fold increase, and adj. p < 0.05 in mouse datasets. Among them, Atf3, Timp1, Cd14, Lgals3, Hmox1, Ccl2, Emp1, Ch25h, Hspb1, Adamts1, Cd44, Icam1, Anxa2, Rgs1, and Vim showed significant increases in both mouse and rat datasets. (2) Ischemic treatment and reperfusion time were the main confounding factors in gene profile changes, while sampling site and ischemic time were not. (3) WGCNA identified a reperfusion-time irrelevant and inflammation-related module and a reperfusion-time relevant and thrombo-inflammation related module. Astrocytes and microglia were the main contributors of the gene changes in these two modules. (4) Forty-four module core hub genes were identified. We validated the expression of unreported stroke-associated core hubs or human stroke-associated core hubs. Zfp36 mRNA was upregulated in permanent MCAO; Rhoj, Nfkbiz, Ms4a6d, Serpina3n, Adamts-1, Lgals3, and Spp1 mRNAs were upregulated in both transient MCAO and permanent MCAO; and NFKBIZ, ZFP3636, and MAFF proteins, unreported core hubs implicated in negative regulation of inflammation, were upregulated in permanent MCAO, but not in transient MCAO. Collectively, these results expand our knowledge of the genetic profile involved in brain ischemia and reperfusion, highlighting the crucial role of inflammatory disequilibrium in brain ischemia.

A Comparative Study of Two Models of Intraluminal Filament Middle Cerebral Artery Occlusion in Rats: Long-Lasting Accumulation of Corticosterone and Interleukins in the Hippocampus and Frontal Cortex in Koizumi Model

Recently, we have shown the differences in the early response of corticosterone and inflammatory cytokines in the hippocampus and frontal cortex (FC) of rats with middle cerebral artery occlusion (MCAO), according to the methods of Longa et al. (LM) and Koizumi et al. (KM) which were used as alternatives in preclinical studies to induce stroke in rodents. In the present study, corticosterone and proinflammatory cytokines were assessed 3 months after MCAO. The most relevant changes detected during the first days after MCAO became even more obvious after 3 months. In particular, the MCAO-KM (but not the MCAO-LM) group showed significant accumulation of corticosterone and IL1β in both the ipsilateral and contralateral hippocampus and FC. An accumulation of TNFα was detected in the ipsilateral hippocampus and FC in the MCAO-KM group. Thus, unlike the MCAO-LM, the MCAO-KM may predispose the hippocampus and FC of rats to long-lasting bilateral corticosterone-dependent distant neuroinflammatory damage. Unexpectedly, only the MCAO-LM rats demonstrated some memory deficit in a one-trial step-through passive avoidance test. The differences between the two MCAO models, particularly associated with the long-lasting increase in glucocorticoid and proinflammatory cytokine accumulation in the limbic structures in the MCAO-KM, should be considered in the planning of preclinical experiments, and the interpretation and translation of received results.

Redefining the Koizumi model of mouse cerebral ischemia: A comparative longitudinal study of cerebral and retinal ischemia in the Koizumi and Longa middle cerebral artery occlusion models

Cerebral and retinal ischemia share similar pathogenesis and epidemiology, each carrying both acute and prolonged risk of the other and often co-occurring. The most used preclinical stroke models, the Koizumi and Longa middle cerebral artery occlusion (MCAO) methods, have reported retinal damage with great variability, leaving the disruption of retinal blood supply via MCAO poorly investigated, even providing conflicting assumptions on the origin of the ophthalmic artery in rodents. The aim of our study was to use longitudinal in vivo magnetic resonance assessment of cerebral and retinal vascular perfusion after the ischemic injury to clarify whether and how the Koizumi and Longa methods induce retinal ischemia and how they differ in terms of cerebral and retinal lesion evolution. We provided anatomical evidence of the origin of the ophthalmic artery in mice from the pterygopalatine artery. Following the Koizumi surgery, retinal responses to ischemia overlapped with those in the brain, resulting in permanent damage. In contrast, the Longa method produced only extensive cerebral lesions, with greater tissue loss than in the Koizumi method. Additionally, our data suggests the Koizumi method should be redefined as a model of ischemia with chronic hypoperfusion rather than of ischemia and reperfusion.

Optimisation of a Mouse Model of Cerebral Ischemia-Reperfusion to Address Issues of Survival and Model Reproducibility and Consistency

Middle cerebral artery occlusion (MCAO) induced brain ischemia-reperfusion model in Mice is essential for understanding the pathology of stroke and investigating potential treatments, in which a variety of methods may be employed to block the middle cerebral artery (MCA), the most common being through the insertion of a monofilament; however, in vivo ischemia-reperfusion models are associated, particularly in mice, with high variability in lesion volume and high mortality. We aimed to optimise a mouse model of cerebral ischemia-reperfusion, addressing issues of mouse survival, model reproducibility, and consistency. The model was optimised in two ways: first, insert the monofilament directly through the internal carotid artery rather than through the external or common carotid artery, and second, by extending the length of the silicone coating on the monofilament, the length of the silicone coating enables embolization of the beginning of the middle cerebral artery, as well as the anterior cerebral artery and part of the posterior communicating artery. Results: We assessed various parameters, including blood flow changes in the middle cerebral artery, stability of the infarct area, correlation between infarct volume percentages and neurological deficit scores, mortality, weight changes, and wellbeing. We found that optimisation of the surgical procedure may improve mouse wellbeing and reduce mortality, through reduced weight loss and decrease the variability. In conclusion, we suggest that the optimisation of the model is superior for the study of both short and long-term outcomes of ischemic stroke. These results have considerable implications on stroke model selection for researchers.

Signaling pathways involved in ischemic stroke: molecular mechanisms and therapeutic interventions

Ischemic stroke is caused primarily by an interruption in cerebral blood flow, which induces severe neural injuries, and is one of the leading causes of death and disability worldwide. Thus, it is of great necessity to further detailly elucidate the mechanisms of ischemic stroke and find out new therapies against the disease. In recent years, efforts have been made to understand the pathophysiology of ischemic stroke, including cellular excitotoxicity, oxidative stress, cell death processes, and neuroinflammation. In the meantime, a plethora of signaling pathways, either detrimental or neuroprotective, are also highly involved in the forementioned pathophysiology. These pathways are closely intertwined and form a complex signaling network. Also, these signaling pathways reveal therapeutic potential, as targeting these signaling pathways could possibly serve as therapeutic approaches against ischemic stroke. In this review, we describe the signaling pathways involved in ischemic stroke and categorize them based on the pathophysiological processes they participate in. Therapeutic approaches targeting these signaling pathways, which are associated with the pathophysiology mentioned above, are also discussed. Meanwhile, clinical trials regarding ischemic stroke, which potentially target the pathophysiology and the signaling pathways involved, are summarized in details. Conclusively, this review elucidated potential molecular mechanisms and related signaling pathways underlying ischemic stroke, and summarize the therapeutic approaches targeted various pathophysiology, with particular reference to clinical trials and future prospects for treating ischemic stroke.

Bridging the Transient Intraluminal Stroke Preclinical Model to Clinical Practice: From Improved Surgical Procedures to a Workflow of Functional Tests

Acute ischemic stroke (AIS) remains a leading cause of mortality, despite significant advances in therapy (endovascular thrombectomy). Failure in developing novel effective therapies is associated with unsuccessful translation from preclinical studies to clinical practice, associated to inconsistent and highly variable infarct areas and lack of relevant post-stroke functional evaluation in preclinical research. To outreach these limitations, we optimized the intraluminal transient middle cerebral occlusion, a widely used mouse stroke model, in two key parameters, selection of appropriate occlusion filaments and time of occlusion, which show a significant variation in the literature. We demonstrate that commercially available filaments with short coating length (1–2 mm), together with 45-min occlusion, results in a consistent affected brain region, similar to what is observed in most patients with AIS. Importantly, a dedicated post-stroke care protocol, based on clinical practice applied to patients who had stroke, resulted in lower mortality and improved mice welfare. Finally, a battery of tests covering relevant fine motor skills, sensory functions, and learning/memory behaviors revealed a significant effect of tMCAO brain infarction, which is parallel to patient symptomatology as measured by relevant clinical scales (NIH Stroke Scale, NIHSS and modified Rankin Scale, mRS). Thus, in order to enhance translation to clinical practice, future preclinical stroke research must consider the methodology described in this study, which includes improved reproducible surgical procedure, postoperative care, and the battery of functional tests. This will be a major step s closing the gap from bench to bedside, rendering the development of novel effective therapeutic approaches.

Preserving mitochondrial function by inhibiting GRP75 ameliorates neuron injury under ischemic stroke

Ischemic stroke is a life-threatening disease, which is closely related to neuron damage during ischemia. Mitochondrial dysfunction is essentially involved in the pathophysiological process of ischemic stroke. Mitochondrial calcium overload contributes to the development of mitochondrial dysfunction. However, the underlying mechanisms of mitochondrial calcium overload are far from being fully revealed. In the present study, middle cerebral artery obstruction (MCAO) was performed in vivo and oxygen and glucose deprivation (OGD) in vitro. The results indicated that both MCAO and OGD induced significant mitochondrial dysfunction in vivo and in vitro. The mitochondria became fragmented under hypoxia conditions, accompanied with upregulation of the heat shock protein 75 kDa glucose-regulated protein (GRP75). Inhibition of GRP75 was able to effectively ameliorate mitochondrial calcium overload and preserve mitochondrial function, which may provide evidence for further translational studies of ischemic diseases.

Post-ischemia common carotid artery occlusion worsens memory loss, but not sensorimotor deficits, in long-term survived stroke mice

Ischemic stroke in rodents is usually induced by intraluminal occlusion of the middle cerebral artery (MCA) via the external carotid artery (ECA) or the common carotid artery (CCA). The latter route requires permanent CCA occlusion after ischemia, and here, we assess its effects on long-term outcomes. Transient occlusion of MCA and CCA was performed at normal body temperature. After 90minutes of ischemia, mice were randomized to permanent CCA occlusion or no occlusion (control group). Body weight, and motor and sensory functions, ie, pole test, adhesive tape removal, and elevated plus maze, were evaluated at 24hours, and at 7 and 28 days after stroke. Infarct volume, apoptosis, and activation of astrocytes and microglia were assessed at 4 weeks by an investigator blinded to groups. The Morris water maze test was performed at 3 weeks in the second experiment. One mouse died at 4 days, and the other mice survived with persistent neurologic deficits. CCA-occluded mice exhibited delayed turn on the pole at 24hours and decreased responses to the von Frey filament, and spent more time on the pole at 7 and 28 days than the control group. Infarction, hemispheric atrophy, glial activation, and apoptotic neuronal death were present in all mice, and no intra-group difference was found. However, CCA-occluded mice had a significantly poorer performance in the Morris water maze compared to the control group, which showed an adverse effect of post-ischemia CCA occlusion on cognition. Thus, the model selection should be well considered in preclinical efficacy studies on stroke-induced vascular dementia and stroke with Alzheimer's disease.

Ischemic Stroke, Glucocorticoids, and Remote Hippocampal Damage: A Translational Outlook and Implications for Modeling

Progress in treating ischemic stroke (IS) and its delayed consequences has been frustratingly slow due to the insufficient knowledge on the mechanism. One important factor, the hypothalamic-pituitary-adrenocortical (HPA) axis is mostly neglected despite the fact that both clinical data and the results from rodent models of IS show that glucocorticoids, the hormones of this stress axis, are involved in IS-induced brain dysfunction. Though increased cortisol in IS is regarded as a biomarker of higher mortality and worse recovery prognosis, the detailed mechanisms of HPA axis dysfunction involvement in delayed post-stroke cognitive and emotional disorders remain obscure. In this review, we analyze IS-induced HPA axis alterations and supposed association of corticoid-dependent distant hippocampal damage to post-stroke brain disorders. A translationally important growing point in bridging the gap between IS pathogenesis and clinic is to investigate the involvement of the HPA axis disturbances and related hippocampal dysfunction at different stages of SI. Valid models that reproduce the state of the HPA axis in clinical cases of IS are needed, and this should be considered when planning pre-clinical research. In clinical studies of IS, it is useful to reinforce diagnostic and prognostic potential of cortisol and other HPA axis hormones. Finally, it is important to reveal IS patients with permanently disturbed HPA axis. Patients-at-risk with high cortisol prone to delayed remote hippocampal damage should be monitored since hippocampal dysfunction may be the basis for development of post-stroke cognitive and emotional disturbances, as well as epilepsy.

A Comparative Study of Koizumi and Longa Methods of Intraluminal Filament Middle Cerebral Artery Occlusion in Rats: Early Corticosterone and Inflammatory Response in the Hippocampus and Frontal Cortex

Two classical surgical approaches for intraluminal filament middle cerebral artery occlusion (MCAO), the Longa et al. (LM) and Koizumi et al. methods (KM), are used as alternatives in preclinical studies to induce stroke in rodents. Comparisons of these MCAO models in mice showed critical differences between them along with similarities (Smith et al. 2015; Morris et al. 2016). In this study, a direct comparison of MCAO-KM and MCAO-LM in rats was performed. Three days after MCAO, infarct volume, mortality rate, neurological deficit, and weight loss were similar in these models. MCAO-LM rats showed an increase in ACTH levels, while MCAO-KM rats demonstrated elevated corticosterone and interleukin-1β in blood serum. Corticosterone accumulation was detected in the frontal cortex (FC) and the hippocampus of the MCAO-KM group. IL1β beta increased in the ipsilateral hippocampus in the MCAO-KM group and decreased in the contralateral FC of MCAO-LM rats. Differences revealed between MCAO-KM and MCAO-LM suggest that corticosterone and interleukin-1β release as well as hippocampal accumulation is more expressed in MCAO-KM rats, predisposing them to corticosterone-dependent distant neuroinflammatory hippocampal damage. The differences between two models, particularly, malfunction of the hypothalamic-pituitary-adrenal axis, should be considered in the interpretation, comparison, and translation of pre-clinical experimental results.

Dynamic oxygen-17 MRI with adaptive temporal resolution using golden-means-based 3D radial sampling

PURPOSE

The aim of this study was to develop a high-resolution 3D oxygen-17 (17 O) MRI method to delineate the kinetics of 17 O-enriched water (H217 O) across the entire mouse brain after a bolus injection via the tail vein.

METHODS

The dynamic 17 O signal was acquired with a golden-means-based 3D radial sampling scheme. To achieve adequate temporal resolution with preserved spatial resolution, a k-space-weighted view sharing strategy was used in image reconstruction with an adaptive window size tailored to the kinetics of the 17 O signal. Simulation studies were performed to determine the adequate image reconstruction parameters. The established method was applied to delineating the kinetics of intravenously injected H217 O in vivo in the post-stroke mouse brain.

RESULTS

The proposed dynamic 17 O-MRI method achieved an isotropic resolution of 1.21 mm (0.77 mm nominal) in mouse brain at 9.4T, with the temporal resolution increased gradually from 3 s at the initial phase of rapid signal increase to 15 s at the steady-state. The high spatial resolution enabled the delineation of the heterogeneous H217 O uptake and washout kinetics in stroke-affected mouse brain.

CONCLUSION

The current study demonstrated a 3D 17 O-MRI method for dynamic monitoring of 17 O signal changes with high spatial and temporal resolution. The method can be utilized to quantify physiological parameters such as cerebral blood flow and blood-brain barrier permeability by tracking injected H217 O. It can also be used to measure oxygen consumption rate in 17 O-oxygen inhalation studies.

Involvement of the Microglial Aryl Hydrocarbon Receptor in Neuroinflammation and Vasogenic Edema after Ischemic Stroke

Microglia are activated after ischemic stroke and induce neuroinflammation. The expression of the aryl hydrocarbon receptor (AhR) has recently been reported to elicit cytokine expression. We previously reported that microglial activation mediates ischemic edema progression. Thus, the purpose of this study was to examine the role of AhR in inflammation and edema after ischemia using a mouse middle cerebral artery occlusion (MCAO) model. MCAO upregulated AhR expression in microglia during ischemia. MCAO increased the expression of tumor necrosis factor α (TNFα) and then induced edema progression, and worsened the modified neurological severity scores, with these being suppressed by administration of an AhR antagonist, CH223191. In THP-1 macrophages, the NADPH oxidase (NOX) subunit p47phox was significantly increased by AhR ligands, especially under inflammatory conditions. Suppression of NOX activity by apocynin or elimination of superoxide by superoxide dismutase decreased TNFα expression, which was induced by the AhR ligand. AhR ligands also elicited p47phox expression in mouse primary microglia. Thus, p47phox may be important in oxidative stress and subsequent inflammation. In MCAO model mice, P47phox expression was upregulated in microglia by ischemia. Lipid peroxidation induced by MCAO was suppressed by CH223191. Taken together, these findings suggest that AhR in the microglia is involved in neuroinflammation and subsequent edema, after MCAO via p47phox expression upregulation and oxidative stress.

Improved reperfusion following alternative surgical approach for experimental stroke in mice

Background: Following ischemic stroke, recanalisation and restoration of blood flow to the affected area of the brain is critical and directly correlates with patient recovery.  In vivo models of ischemic stroke show high variability in outcomes, which may be due to variability in reperfusion.  We previously reported that a surgical refinement in the middle cerebral artery occlusion (MCAO) model of stroke, via repair of the common carotid artery (CCA), removes the reliance on the Circle of Willis for reperfusion and reduced infarct variability.  Here we further assess this refined surgical approach on reperfusion characteristics following transient MCAO in mice. Methods: Mice underwent 60 min of MCAO, followed by either CCA repair or ligation at reperfusion.  All mice underwent laser speckle contrast imaging at baseline, 24 h and 48 h post-MCAO. Results: CCA ligation reduced cerebral perfusion in the ipsilateral hemisphere compared to baseline (102.3 ± 4.57%) at 24 h (85.13 ± 16.09%; P < 0.01) and 48 h (75.04 ± 12.954%; P < 0.001) post-MCAO. Repair of the CCA returned perfusion to baseline (94.152 ± 2.44%) levels and perfusion was significantly improved compared to CCA ligation at both 24 h (102.83 ± 8.41%; P < 0.05) and 48 h (102.13 ± 9.34%; P < 0.001) post-MCAO. Conclusions: Our findings show CCA repair, an alternative surgical approach for MCAO, results in improved ischemic hemisphere perfusion during the acute phase.

Improved reperfusion following alternative surgical approach for experimental stroke in mice

Background: Following ischemic stroke, recanalisation and restoration of blood flow to the affected area of the brain is critical and directly correlates with patient recovery.  In vivo models of ischemic stroke show high variability in outcomes, which may be due to variability in reperfusion.  We previously reported that a surgical refinement in the middle cerebral artery occlusion (MCAO) model of stroke, via repair of the common carotid artery (CCA), removes the reliance on the Circle of Willis for reperfusion and reduced infarct variability.  Here we further assess this refined surgical approach on reperfusion characteristics following transient MCAO in mice. Methods: Mice underwent 60 min of MCAO, followed by either CCA repair or ligation at reperfusion.  All mice underwent laser speckle contrast imaging at baseline, 24 h and 48 h post-MCAO. Results: CCA ligation reduced cerebral perfusion in the ipsilateral hemisphere compared to baseline (102.3 ± 4.57%) at 24 h (85.13 ± 16.09%; P < 0.01) and 48 h (75.04 ± 12.954%; P < 0.001) post-MCAO. Repair of the CCA returned perfusion to baseline (94.152 ± 2.44%) levels and perfusion was significantly improved compared to CCA ligation at both 24 h (102.83 ± 8.41%; P < 0.05) and 48 h (102.13 ± 9.34%; P < 0.001) post-MCAO. Conclusions: Our findings show CCA repair, an alternative surgical approach for MCAO, results in improved ischemic hemisphere perfusion during the acute phase.

Improved reperfusion following alternative surgical approach for experimental stroke in mice

Background: Following ischemic stroke, recanalisation and restoration of blood flow to the affected area of the brain is critical and directly correlates with patient recovery.  In vivo models of ischemic stroke show high variability in outcomes, which may be due to variability in reperfusion.  We previously reported that a surgical refinement in the middle cerebral artery occlusion (MCAO) model of stroke, via repair of the common carotid artery (CCA), removes the reliance on the Circle of Willis for reperfusion and reduced infarct variability.  Here we further assess this refined surgical approach on reperfusion characteristics following transient MCAO in mice. Methods: Mice underwent 60 min of MCAO, followed by either CCA repair or ligation at reperfusion.  All mice underwent laser speckle contrast imaging at baseline, 24 h and 48 h post-MCAO. Results: CCA ligation reduced cerebral perfusion in the ipsilateral hemisphere compared to baseline (102.3 ± 4.57%) at 24 h (85.13 ± 16.09%; P < 0.01) and 48 h (75.04 ± 12.954%; P < 0.001) post-MCAO. Repair of the CCA returned perfusion to baseline (94.152 ± 2.44%) levels and perfusion was significantly improved compared to CCA ligation at both 24 h (102.83 ± 8.41%; P < 0.05) and 48 h (102.13 ± 9.34%; P < 0.001) post-MCAO. Conclusions: Our findings show CCA repair, an alternative surgical approach for MCAO, results in improved ischemic hemisphere perfusion during the acute phase.

Remarkable cell recovery from cerebral ischemia in rats using an adaptive escalator-based rehabilitation mechanism

Currently, many ischemic stroke patients worldwide suffer from physical and mental impairments, and thus have a low quality of life. However, although rehabilitation is acknowledged as an effective way to recover patients’ health, there does not exist yet an adaptive training platform for animal tests so far. For this sake, this paper aims to develop an adaptive escalator (AE) for rehabilitation of rats with cerebral ischemia. Rats were observed to climb upward spontaneously, and a motor-driven escalator, equipped with a position detection feature and an acceleration/deceleration mechanism, was constructed accordingly as an adaptive training platform. The rehabilitation performance was subsequently rated using an incline test, a rotarod test, the infarction volume, the lesion volume, the number of MAP2 positive cells and the level of cortisol. This paper is presented in 3 parts as follows. Part 1 refers to the escalator mechanism design, part 2 describes the adaptive ladder-climbing rehabilitation mechanism, and part 3 discusses the validation of an ischemic stroke model. As it turned out, a rehabilitated group using this training platform, designated as the AE group, significantly outperformed a control counterpart in terms of a rotarod test. After the sacrifice of the rats, the AE group gave an average infarction volume of (34.36 ± 3.8)%, while the control group gave (66.41 ± 3.1)%, validating the outperformance of the escalator-based rehabilitation platform in a sense. An obvious difference between the presented training platform and conventional counterparts is the platform mechanism, and for the first time in the literature rats can be well and voluntarily rehabilitated at full capacity using an adaptive escalator. Taking into account the physical diversity among rats, the training strength provided was made adaptive as a reliable way to eliminate workout or secondary injury. Accordingly, more convincing arguments can be made using this mental stress-free training platform.

Current advances in ischemic stroke research and therapies

With more than 795,000 cases occurring every year, stroke has become a major problem in the United States across all demographics. Stroke is the leading cause of long-term disability and is the fifth leading cause of death in the US. Ischemic stroke represents 87% of total strokes in the US, and is currently the main focus of stroke research. This literature review examines the risk factors associated with ischemic stroke, changes in cell morphology and signaling in the brain after stroke, and the advantages and disadvantages of in vivo and in vitro ischemic stroke models. Classification systems for stroke etiology are also discussed briefly, as well as current ischemic stroke therapies and new therapeutic strategies that focus on the potential of stem cells to promote stroke recovery.

Metallothionein I as a direct link between therapeutic hematopoietic stem/progenitor cells and cerebral protection in stroke

Stroke continues to be a leading cause of death and disability worldwide, yet effective treatments are lacking. Previous studies have indicated that stem-cell transplantation could be an effective treatment. However, little is known about the direct impact of transplanted cells on injured brain tissue. We wanted to help fill this knowledge gap and investigated effects of hematopoietic stem/progenitor cells (HSPCs) on the cerebral microcirculation after ischemia-reperfusion injury (I/RI). Treatment of HSPCs in I/RI for up to 2 wk after cerebral I/RI led to decreased mortality rate, decreased infarct volume, improved functional outcome, reduced microglial activation, and reduced cerebral leukocyte adhesion. Confocal microscopy and fluorescence-activated cell sorting analyses showed transplanted HSPCs emigrate preferentially into ischemic cortex brain parenchyma. We isolated migrated HSPCs from the brain; using RNA sequencing to investigate the transcriptome, we found metallothionein (MT, particularly MT-I) transcripts were dramatically up-regulated. Finally, to confirm the significance of MT, we exogenously administered MT-I after cerebral I/RI and found that it produced neuroprotection in a manner similar to HSPC treatment. These findings provide novel evidence that the mechanism through which HSPCs promote repair after stroke maybe via direct action of HSPC-derived MT-I and could therefore be exploited as a useful therapeutic strategy for stroke.-Smith, H. K., Omura, S., Vital, S. A., Becker, F., Senchenkova, E. Y., Kaur, G., Tsunoda, I., Peirce, S. M., Gavins, F. N. E. Metallothionein I as a direct link between therapeutic hematopoietic stem/progenitor cells and cerebral protection in 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'.

Surgical Approach for Middle Cerebral Artery Occlusion and Reperfusion Induced Stroke in Mice

Stroke is a leading cause of death worldwide and continues to be one of the major causes of long-term adult disabilities. About 87% of strokes are ischemic in origin and occur in the territory of the middle cerebral artery (MCA). Currently the only Food and Drug Administration (FDA) approved drug for the treatment of this devastating disease is tissue plasminogen activator (tPA). However, tPA has a small therapeutic window for administration (3 - 6 hr), and is only effective in 4% of the patients who actually receive it. Current research focuses on understanding the pathophysiology of stroke in order to find potential therapeutic targets. Thus, reliable models are crucial, and the MCA occlusion (MCAo) model (also termed the intraluminal filament or suture model) is deemed to be the most clinically relevant surgical model of ischemic stroke, and is fairly non-invasive and easily reproducible. Typically the MCAo model is used with rodents, especially with mice due to all the genetic variations available for this species. Here we describe (and present in the video) how to successfully perform the MCAo model (with reperfusion) in mice to generate reliable and reproducible data.

A Comparative Study of Variables Influencing Ischemic Injury in the Longa and Koizumi Methods of Intraluminal Filament Middle Cerebral Artery Occlusion in Mice

The intraluminal filament model of middle cerebral artery occlusion (MCAO) in mice and rats has been plagued by inconsistency, owing in part to the multitude of variables requiring control. In this study we investigated the impact of several major variables on survival rate, lesion volume, neurological scores, cerebral blood flow (CBF) and body weight including filament width, time after reperfusion, occlusion time and the choice of surgical method. Using the Koizumi method, we found ischemic injury can be detected as early as 30 min after reperfusion, to a degree that is not statistically different from 24 h post-perfusion, using 2,3,5-Triphenyltetrazolium chloride (TTC) staining. We also found a distinct increase in total lesion volume with increasing occlusion time, with 30–45 min a critical time for the development of large, reproducible lesions. Furthermore, although we found no significant difference in total lesion volume generated by the Koizumi and Longa methods of MCAO, nor were survival rates appreciably different between the two at 4 h after reperfusion, the Longa method produces significantly greater reperfusion. Finally, we found no statistical evidence to support the exclusion of data from animals experiencing a CBF reduction of <70% in the MCA territory following MCAO, using laser-Doppler flowmetry. Instead we suggest the main usefulness of laser-Doppler flowmetry is for guiding filament placement and the identification of subarachnoid haemorrhages and premature reperfusion. In summary, this study provides detailed evaluation of the Koizumi method of intraluminal filament MCAO in mice and a direct comparison to the Longa method.

A modification of intraluminal middle cerebral artery occlusion/reperfusion model for ischemic stroke with laser Doppler flowmetry guidance in mice

Stroke is one of the common causes of death and disability in the world. The intraluminal middle cerebral artery occlusion/reperfusion (MCAO/R) model is a "gold standard" in surgical ischemic stroke models. Here, we optimized the procedure of this model by ligating on external carotid artery (ECA) stump and two ligatures prepared on internal carotid artery, which could improve the success and survival rate in mice. The results show that ECA approach was superior to common carotid artery approach. Meanwhile, we found that the exposure of pterygopalatine artery was not an essential step for MCAO/R model in mice.