Preclinical models of intracerebral hemorrhage: a translational perspective

Hypothermia and temperature modulation for intracerebral hemorrhage (ICH): pathophysiology and translational applications

Background

Intracerebral hemorrhage (ICH) still poses a substantial challenge in clinical medicine because of the high morbidity and mortality rate that characterizes it. This review article expands into the complex pathophysiological processes underlying primary and secondary neuronal death following ICH. It explores the potential of therapeutic hypothermia as an intervention to mitigate these devastating effects.

Methods

A comprehensive literature review to gather relevant studies published between 2000 and 2023.

Discussion

Primary brain injury results from mechanical damage caused by the hematoma, leading to increased intracranial pressure and subsequent structural disruption. Secondary brain injury encompasses a cascade of events, including inflammation, oxidative stress, blood-brain barrier breakdown, cytotoxicity, and neuronal death. Initial surgical trials failed to demonstrate significant benefits, prompting a shift toward molecular mechanisms driving secondary brain injury as potential therapeutic targets. With promising preclinical outcomes, hypothermia has garnered attention, but clinical trials have yet to establish its definitive effectiveness. Localized hypothermia strategies are gaining interest due to their potential to minimize systemic complications and improve outcomes. Ongoing and forthcoming clinical trials seek to clarify the role of hypothermia in ICH management.

Conclusion

Therapeutic hypothermia offers a potential avenue for intervention by targeting the secondary injury mechanisms. The ongoing pursuit of optimized cooling protocols, localized cooling strategies, and rigorous clinical trials is crucial to unlocking the potential of hypothermia as a therapeutic tool for managing ICH and improving patient outcomes.

Establishment of a rat model of severe spontaneous intracerebral hemorrhage

Background

Severe intracerebral hemorrhage (ICH) is the most devastating subtype of stroke resulting in high mortality and disability. At present, the development of targeted treatments to minimize the high morbidity and mortality is limited partly due to the lack of a severe ICH animal model. In this study, we aimed to establish an accurate severe ICH model in rats and examine the pathological and physiological changes associated with ICH.

Methods

A rat model of severe ICH model was established by intrastriatal injection of autologous blood using different blood volumes (ICH 100 µL group, ICH 130 µL group, ICH 160 µL group, ICH 170 µL group, and ICH 180 µL group). The mortality was assessed during the 28-day post-ICH period. Short- and long-term neurological deficits were evaluated using the Longa method, foot fault, falling latency, and Morris water maze tests. Brain water content, hematoma volume, hemoglobin content, and magnetic resonance imaging were assessed to determine the extent of brain injury. Immunofluorescence staining was conducted to examine microglial activation and neuronal apoptosis. Hematoxylin and eosin (H&E) staining, lung water content, and western blotting were used to assess lung injury following ICH.

Results

The mortality of ICH rats increased significantly with an increase in autologous blood injection. The 28-day mortality in the 100 µL, 130 µL, 160 µL, 170 µL, and 180 µL ICH groups were 5%, 20%, 40%, 75%, and 100%, respectively. A significantly higher 28-day mortality was observed in the ICH 160 µL group compared to the ICH 100 µL group. The ICH 160 µL group exhibited significantly increased neurological deficits, brain edema, hematoma volume, and hemoglobin content compared to the sham group. Compared with the sham operation group, the activation of microglia and neuronal death in ICH 160 µL rats increased. The use of H&E staining and western blotting demonstrated that disruption of the intra-alveolar structure, alveolar edema, and infiltration of inflammatory cells and cytokines into the lung tissue were more severe in the ICH 160 µL group than the sham group.

Conclusions

A severe ICH model in rats was successfully established using an injection of autologous blood at a volume of 160 µL. This model may provide a valuable tool to examine the pathological mechanisms and potential therapeutic interventions of severe ICH.

Optimizing The Timing of Stereotactic Minimally Invasive Drainage for Hypertensive Intracerebral Hemorrhage

INTRODUCTION

Intracerebral hemorrhage is a high-risk pathological event that is associated with formidable morality rates. Here, our objective was to perform a retrospective study to determine the best timing for drainage using physiological data on patients who received drainage at different timings.

METHODS

In this retrospective study, we reviewed 198 patients with hypertensive cerebral hemorrhage who underwent stereotactic drainage at the conventional timing (surgery within 12 h of admission; control group) and 216 patients who underwent stereotactic drainage at a customized surgical timing (elective group). Follow-ups were performed at 3 and 6 months after surgery.

RESULTS

The clinical indicators, including prognosis, hematoma clearance, recurrent hemorrhage, intracerebral infection, pulmonary infection, deep venous thrombosis, gastrointestinal hemorrhage, National Institutes of Health Stroke Scale scores, and matrix metallopeptidase 2 and 9 levels, were compared between the control and elective groups. Our data indicated that the elective group had significantly better prognosis compared to the control group (p = 0.021), with a higher rate of hematoma clearance (p = 0.004) and a lower rate of recurrent hemorrhage (p = 0.018). The total occurrence rate of post-surgery complications was also lower for the elective group (p = 0.026). NIHSS scores and serum MMP2/9 levels of the elective group were lower than those of the control group.

CONCLUSIONS

Customized timing of stereotactic drainage may be superior to conventional fixed timing (within 12 h post-hemorrhage) in reducing post-surgery complications and promoting recovery, which supports the potential use of customized timing of stereotactic minimally invasive drainage as a new convention in clinics.

Animal models for the study of intracranial hematomas (Review)

Intracranial hematomas (ICH) are a frequent condition in neurosurgical and neurological practices, with several mechanisms of primary and secondary injury. Experimental research has been fundamental for the understanding of the pathophysiology implicated with ICH and the development of therapeutic interventions. To date, a variety of different animal approaches have been described that consider, for example, the ICH evolutive phase, molecular implications and hemodynamic changes. Therefore, choosing a test protocol should consider the scope of each particular study. The present review summarized investigational protocols in experimental research on the subject of ICH. With this subject, injection of autologous blood or bacterial collagenase, inflation of intracranial balloon and avulsion of cerebral vessels were the models identified. Rodents (mice) and swine were the most frequent species used. These different models allowed improvements on the understanding of intracranial hypertension establishment, neuroinflammation, immunology, brain hemodynamics and served to the development of therapeutic strategies.

Rodent Models of Post-Stroke Dementia

Post-stroke cognitive impairment is one of the most common complications in stroke survivors. Concomitant vascular risk factors, including aging, diabetes mellitus, hypertension, dyslipidemia, or underlying pathologic conditions, such as chronic cerebral hypoperfusion, white matter hyperintensities, or Alzheimer’s disease pathology, can predispose patients to develop post-stroke dementia (PSD). Given the various clinical conditions associated with PSD, a single animal model for PSD is not possible. Animal models of PSD that consider these diverse clinical situations have not been well-studied. In this literature review, diverse rodent models that simulate the various clinical conditions of PSD have been evaluated. Heterogeneous rodent models of PSD are classified into the following categories: surgical technique, special structure, and comorbid condition. The characteristics of individual models and their clinical significance are discussed in detail. Diverse rodent models mimicking the specific pathomechanisms of PSD could provide effective animal platforms for future studies investigating the characteristics and pathophysiology of PSD.

The transient intraluminal filament Middle Cerebral Artery Occlusion stroke model in rats. A step by step guide and technical considerations

OBJECTIVE

Stroke is a leading cause of disability and mortality worldwide. Related research, although already providing significant insights on the underlying pathophysiology and potential treatment strategies, is far from conclusive. In this respect, stroke models are proving of extreme significance for laboratories around the world. The scope of this article is to present in detail the most popular to date focal stroke model, the tifMCAO model in rats. This model mimics reliably stroke in humans and also approximates endovascular thrombectomy.

METHODS

The tifMCAO model was performed on Wistar rats with a weight of 300-400 gr. The surgical technique is described in a step-wise manner, while pictures and/or HD video accompany each step. Complete arteriotomy of the ECA stump is introduced during the procedure.

RESULTS

We performed the tifMCAO in 65 rats (male and female) involved in various experimental protocols. Although that initial mortality was 48%, practice reduced this number to10%. The mean procedural time was 53 min (range, 38 - 85 min). Stroke was confirmed in 87.5% of the cases.

CONCLUSIONS

The tifMCAO stroke model in rats is the most commonly utilized experimental model of focal ischemia because of its clinical relevance. We revisited the procedure and divided it, for instructional purposes, in 15 consecutive distinct steps.

Neuroprotective Pentapeptide, CN-105, Improves Outcomes in Translational Models of Intracerebral Hemorrhage

BACKGROUND

Intracerebral hemorrhage (ICH) is a devastating form of cerebrovascular disease for which there are no approved pharmacological interventions that improve outcomes. Apolipoprotein E (apoE) has emerged as a promising therapeutic target given its isoform-specific neuroprotective properties and ability to modify neuroinflammatory responses. We developed a 5-amino acid peptide, CN-105, that mimics the polar face of the apoE helical domain involved in receptor interactions, readily crosses the blood-brain barrier, and improves outcomes in well-established preclinical ICH models. In the current study, we investigated the therapeutic potential of CN-105 in translational ICH models that account for hypertensive comorbidity, sex, species, and age.

METHODS

In three separate experiments, we delivered three intravenous doses of CN-105 (up to 0.20 mg/kg) or vehicle to hypertensive male BPH/2 J mice, spontaneously hypertensive female rats, or 11-month-old male mice within 24-h of ICH. Neuropathological and neurobehavioral outcomes were determined over 3, 7, and 9 days, respectively.

RESULTS

In spontaneously hypertensive male mice, there was a significant dose-dependent effect of CN-105 on vestibulomotor function at 0.05 and 0.20 mg/kg doses (p < 0.05; 95% CI: 0.91-153.70 and p < 0.001; 95% CI: 49.54-205.62), while 0.20 mg/kg also improved neuroseverity scores (p < 0.05; 95% CI: 0.27-11.00) and reduced ipsilateral brain edema (p < 0.05; 95% CI: - 0.037 to - 0.001). In spontaneously hypertensive female rats, CN-105 (0.05 mg/kg) had a significant effect on vestibulomotor function (p < 0.01; η²  = 0.093) and neuroseverity scores (p < 0.05; η² = 0.083), and reduced contralateral edema expansion (p < 0.01; 95% CI: - 1.41 to - 0.39). In 11-month-old male mice, CN-105 had a significant effect on vestibulomotor function (p < 0.001; η² = 0.111) but not neuroseverity scores (p > 0.05; η² = 0.034).

CONCLUSIONS

Acute treatment with CN-105 improves outcomes in translational ICH models independent of sex, species, age, or hypertensive comorbidity.

Loss of MIC60 Aggravates Neuronal Death by Inducing Mitochondrial Dysfunction in a Rat Model of Intracerebral Hemorrhage

Mitochondrial damage has been reported to be a critical factor for secondary brain injury (SBI) induced by intracerebral hemorrhage (ICH). MIC60 is a key element of the mitochondrial contact site and cristae junction organizing system (MICOS), which takes a principal part in maintaining mitochondrial structure and function. The role of MIC60 and its underlying mechanisms in ICH-induced SBI are not clear, which will be investigated in this present study. To establish and emulate ICH model in vivo and in vitro, autologous blood was injected into the right basal ganglia of Sprague-Dawley (SD) rats; and primary-cultured cortical neurons were treated by oxygen hemoglobin (OxyHb). First, after ICH induction, mitochondria were damaged and exhibited mitochondrial crista-structure remodeling, and MIC60 protein levels were reduced. Furthermore, MIC60 overexpression reduced ICH-induced neuronal death both in vivo and in vitro. In addition, MIC60 upregulation reduced ICH-induced cerebral edema, neurobehavioral impairment, and cognitive dysfunction; by contrast, MIC60 knockdown had the opposite effect. Additionally, in primary-cultured neurons, MIC60 overexpression could reverse ICH-induced neuronal cell death and apoptosis, mitochondrial membrane potential collapse, and decrease of mitophagy, indicating that MIC60 overexpression can maintain the integrity of mitochondrial structures. Moreover, loss of MIC60 is after ICH-induced reduction in PINK1 levels and mislocalization of Parkin in primary-cultured neurons. Taken together, our findings suggest that MIC60 plays an important role in ICH-induced SBI and may represent a promising target for ICH therapy.

Rapid hematoma growth triggers spreading depolarizations in experimental intracortical hemorrhage

Recurrent waves of spreading depolarization (SD) occur in brain injury and are thought to affect outcomes. What triggers SD in intracerebral hemorrhage is poorly understood. We employed intrinsic optical signaling, laser speckle flowmetry, and electrocorticography to elucidate the mechanisms triggering SD in a collagenase model of intracortical hemorrhage in mice. Hematoma growth, SD occurrence, and cortical blood flow changes were tracked. During early hemorrhage (0-4 h), 17 out of 38 mice developed SDs, which always originated from the hematoma. No SD was detected at late time points (8-52 h). Neither hematoma size, nor peri-hematoma perfusion were associated with SD occurrence. Further, arguing against ischemia as a trigger factor, normobaric hyperoxia did not inhibit SD occurrence. Instead, SDs always occurred during periods of rapid hematoma growth, which was two-fold faster immediately preceding an SD compared with the peak growth rates in animals that did not develop any SDs. Induced hypertension accelerated hematoma growth and resulted in a four-fold increase in SD occurrence compared with normotensive animals. Altogether, our data suggest that spontaneous SDs in this intracortical hemorrhage model are triggered by the mechanical distortion of tissue by rapidly growing hematomas.

Local Experimental Intracerebral Hemorrhage in Rats

(1) Background: Hemorrhagic stroke is a lethal disease, accounting for 15% of all stroke cases. However, there are very few models of stroke with a hemorrhagic etiology. Research work is devoted to studying the development of cerebrovascular disorders in rats with an intracerebral hematoma model. The aim of this study was to conduct a comprehensive short-term study, including neurological tests, biochemical blood tests, and histomorphological studies of brain structures. (2) Methods: The model was reproduced surgically by traumatizing the brain in the capsula interna area and then injecting autologous blood. Neurological deficit was assessed according to the McGrow stroke-index scale, motor activity, orientation–exploratory behavior, emotionality, and motor functions. On Day 15, after the operation, hematological and biochemical blood tests as well as histological studies of the brain were performed. (3) Results: The overall lethality of the model was 43.7%. Acute intracerebral hematoma in rats causes marked disorders of motor activity and functional impairment, as well as inflammatory processes in the nervous tissue, which persist for at least 14 days. (4) Conclusions: This model reflects the situation observed in the clinic and reproduces the main diagnostic criteria for acute disorders of cerebral circulation.

Intracranial baroreflex is attenuated in an ovine model of renovascular hypertension

We have previously shown that elevations in intracranial pressure (ICP) within physiological ranges in normotensive animals increase arterial pressure; termed the intracranial baroreflex. Hypertension is associated with alterations in reflexes which maintain arterial pressure however, whether the intracranial baroreflex is altered is not known. Hence, in the present study, we tested the hypothesis that in hypertension, physiological increases in ICP would not be accompanied with an increase in arterial pressure. Renovascular hypertension was associated with no change in heart rate, renal blood flow or ICP levels compared to the normotensive group. ICV infusion of saline produced a ramped increase in ICP of 20 ± 1 mmHg. This was accompanied by an increase in arterial pressure (16 ± 2 mmHg) and a significant decrease in renal vascular conductance. ICV infusion of saline in the hypertensive group also increased ICP (19 ± 2 mmHg). However, the increase in arterial pressure was significantly attenuated in the hypertensive group (5 ± 2 mmHg). Ganglionic blockade abolished the increase in arterial pressure in both groups to increased ICP. Our data indicates that physiological increases in ICP lead to increases in arterial pressure in normotensive animals but this is severely attenuated in renovascular hypertension.

Can brain natriuretic peptide, S100b, and interleukin-6 prognosticate the neurological consequences in Egyptian patients presented with supratentorial intracerebral hemorrhage?

Background:

Biomarkers in supratentorial intracerebral hemorrhage (SICH) enhance the prognosis of the disease. This study aimed to assess the prognosticative grade of S100 calcium-binding protein B (S100B), interleukin-6 (IL-6), and the pro-brain natriuretic peptide (pro-BNP) in SICH outcome prediction.

Methods:

Blood samples of 50 SICH patients were analyzed for the biomarkers. The patients were classified into two groups with and without intraventricular hemorrhage (IVH). The following scales including Glasgow Coma Score (GCS), the Barthel index (BI), intracerebral hemorrhage (ICH) score, ICH volume, National Institutes of Health Stroke Scale (NIHSS), Modified Rankin Score (mRS), and length of stay were used to evaluate the severity.

Results:

The severity scores (NIHSS, GCS, BI, mRI) were significantly higher in SICH patients with IVH versus SICH patients without IVH (P = 0.002, 0.008, 0.001, and 0.03, respectively). Serum levels for a pro-BNP and S100b are significantly higher in SICH patients with IVH versus SICH patients without IVH (P = 0.02 and 0.027, respectively). Multivariate correlations between demographic (age), biomarkers panel (IL-6, S100b, and proBNP), and clinical and severity scores (ICH score, ICH volume, length of hospital stay [LOS], BI, mRS, GCS, and NIHSSS) in all studied patients showed a highly significant correlation between ICH score and pro-BNP (P = 0.04). There was a highly significant correlation between LOS and IL-6 (P = 0.003).

Conclusion:

Pro-BNP, IL-6, and S100b are greatly associated with the presence of IVH that, in turn, correlated well with poor clinical outcome measures.

Intraventricular Hemorrhage and White Matter Injury in Preclinical and Clinical Studies

Germinal matrix-intraventricular hemorrhage (IVH) occurs in nearly half of infants born at less than 26 weeks' gestation. Up to 50% of survivors with IVH develop cerebral palsy, cognitive deficits, behavioral disorders, posthemorrhagic ventricular dilatation, or a combination of these sequelae. After the initial bleeding and the primary brain injury, inflammation and secondary brain injury might lead to periventricular leukomalacia or diffuse white matter injury. Potential factors that are involved include microglia and astrocyte activation, degradation of blood components with release of "toxic" products, infiltration of the brain by systemic immune cells, death of neuronal and glial cells, and arrest of preoligodendrocyte maturation. In addition, impairment of the blood-brain barrier may play a major role in the pathophysiology. A wide range of animal models has been used to explore causes and mechanisms leading to IVH-induced brain injury. Preclinical studies have identified potential targets for enhancing brain repair. However, little has been elucidated about the effectiveness of potential interventions in clinical studies. A systematic review of available preclinical and clinical studies might help identify research gaps and which types of interventions may be prioritized. Future trials should report clinically robust and long-term outcomes after IVH.

Automated Assessment of Hematoma Volume of Rodents Subjected to Experimental Intracerebral Hemorrhagic Stroke by Bayes Segmentation Approach

Simulating a clinical condition of intracerebral hemorrhage (ICH) in animals is key to research on the development and testing of diagnostic or treatment strategies for this high-mortality disease. In order to study the mechanism, pathology, and treatment for hemorrhagic stroke, various animal models have been developed. Measurement of hematoma volume is an important assessment parameter to evaluate post-ICH outcomes. However, due to tissue preservation conditions and variables in digitization, quantification of hematoma volume is usually labor intensive and sometimes even subjective. The objective of this study is to develop an automated method that can accurately and efficiently obtain unbiased cerebral hematoma volume. We developed an application (MATLAB program) that can delineate the brain slice from the background and use the Hue information in the Hue/Saturation/Value (HSV) color space to segment the hematoma region. The segmentation threshold of Hue is calculated based on the Bayes classifier theorem so that the minimum error is mathematically ensured and automated processing is enabled. To validate the developed method, we compared the outcomes from the developed method with the hemoglobin content by the spectrophotometric assay method. The results were linearly correlated with statistical significance. The method was also validated by digital phantoms with an error less than 5% compared with the ground truth from the phantoms. Hematoma volumes yielded by the automated processing and those obtained by the operator's manual operation are highly correlated. This automated segmentation approach can be potentially used to quantify hemorrhagic outcomes in rodent stroke models in an unbiased and efficient way.

Loss of Endothelial Laminin α5 Exacerbates Hemorrhagic Brain Injury

Endothelial cells make laminin-411 and laminin-511. Although laminin-411 is well studied, the role of laminin-511 remains largely unknown due to the embryonic lethality of lama5-/- mutants. In this study, we generated endothelium-specific lama5 conditional knockout (α5-TKO) mice and investigated the biological functions of endothelial lama5 in blood-brain barrier (BBB) maintenance under homeostatic conditions and the pathogenesis of intracerebral hemorrhage (ICH). First, the BBB integrity of α5-TKO mice was measured under homeostatic conditions. Next, ICH was induced in α5-TKO mice and their littermate controls using the collagenase model. Various parameters, including injury volume, neuronal death, neurological score, brain edema, BBB integrity, inflammatory cell infiltration, and gliosis, were examined at various time points after injury. Under homeostatic conditions, comparable levels of IgG or exogenous tracers were detected in α5-TKO and control mice. Additionally, no differences in tight junction expression, pericyte coverage, and astrocyte polarity were found in these mice. After ICH, α5-TKO mice displayed enlarged injury volume, increased neuronal death, elevated BBB permeability, exacerbated infiltration of inflammatory cells (leukocytes, neutrophils, and mononuclear cells), aggravated gliosis, unchanged brain edema, and worse neurological function, compared to the controls. These findings suggest that endothelial lama5 is dispensable for BBB maintenance under homeostatic conditions but plays a beneficial role in ICH.

Human Placenta-Derived Mesenchymal Stem Cells Reduce Mortality and Hematoma Size in a Rat Intracerebral Hemorrhage Model in an Acute Phase

Intracerebral hemorrhage (ICH) is a critical disease, highly associated with mortality and morbidity. Several studies have demonstrated the beneficial effect of mesenchymal stem cells (MSCs) on ICH, mostly focused on their mid-to-long-term effect. Acute hematoma expansion is one of the most important prognostic factors of ICH. We hypothesized that MSCs would decrease mortality and hematoma size in acute ICH, based on the findings of a few recent researches reporting their effect on blood-brain barrier and endothelial integrity. Rat ICH models were made using bacterial collagenase. One hour after ICH induction, the rats were randomly divided into MSC-treated and control groups. Mortality, hematoma volume, ventricular enlargement, brain edema, and degenerating neuron count were compared at 24 hours after ICH induction. Expression of tight junction proteins (ZO-1, occludin) and coagulation factor VII mRNA was also compared. Mortality rate (50% versus 8.3%), hematoma size, ventricular size, hemispheric enlargement, and degenerating neuron count were significantly lower in the MSC-treated group (p = 0.034, 0.038, 0.001, 0.022, and <0.001, resp.), while the expression of ZO-1 and occludin was higher (p = 0.007 and 0.012). Administration of MSCs may prevent hematoma expansion in the hyperacute stage of ICH and decrease acute mortality by enhancing the endothelial integrity of cerebral vasculature.

The effects of nanomaterials on blood coagulation in hemostasis and thrombosis

The blood coagulation balance in the organism is achieved by the interaction of the blood platelets (PLTs) with the plasma coagulation system (PCS) and the vascular endothelial cells. In healthy organism, these systems prevent thrombosis and, in events of vascular damage, enable blood clotting to stop bleeding. The dysregulation of hemostasis may cause serious thrombotic and/or hemorrhagic pathologies. Numerous engineered nanomaterials are being investigated for biomedical purposes and are unavoidably exposed to the blood. Also, nanomaterials may access vascular system after occupational, environmental, or other types of exposure. Thus, it is essential to evaluate the effects of engineered nanomaterials on hemostasis. This review focuses on investigations of nanomaterial interactions with the blood components involved in blood coagulation: the PCS and PLTs. Particular emphases include the pathophysiology of effects of nanomaterials on the PCS, including the kallikrein-kinin system, and on PLTs. Methods for investigating these interactions are briefly described, and a review of the most important studies on the interactions of nanomaterials with plasma coagulation and platelets is provided. WIREs Nanomed Nanobiotechnol 2017, 9:e1448. doi: 10.1002/wnan.1448 For further resources related to this article, please visit the WIREs website.

Stages of the Inflammatory Response in Pathology and Tissue Repair after Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a major health concern, with high rates of mortality and morbidity and no highly effective clinical interventions. Basic research in animal models of ICH has provided insight into its complex pathology, in particular revealing the role of inflammation in driving neuronal death and neurologic deficits after hemorrhage. The response to ICH occurs in four distinct phases: (1) initial tissue damage and local activation of inflammatory factors, (2) inflammation-driven breakdown of the blood-brain barrier, (3) recruitment of circulating inflammatory cells and subsequent secondary immunopathology, and (4) engagement of tissue repair responses that promote tissue repair and restoration of neurologic function. The development of CNS inflammation occurs over many days after initial hemorrhage and thus may represent an ideal target for treatment of the disease, but further research is required to identify the mechanisms that promote engagement of inflammatory versus anti-inflammatory pathways. In this review, the authors examine how experimental models of ICH have uncovered critical mediators of pathology in each of the four stages of the inflammatory response, and focus on the role of the immune system in these processes.

Microglial Polarization and Inflammatory Mediators After Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a subtype of stroke with high mortality and morbidity. When a diseased artery within the brain bursts, expansion and absorption of the resulting hematoma trigger a series of reactions that cause primary and secondary brain injury. Microglia are extremely important for removing the hematoma and clearing debris, but they are also a source of ongoing inflammation. This article discusses the role of microglial activation/polarization and related inflammatory mediators, such as Toll-like receptor 4, matrix metalloproteinases, high-mobility group protein box-1, nuclear factor erythroid 2-related factor 2, heme oxygenase, and iron, in secondary injury after ICH and highlights the potential targets for ICH treatment.

Progesterone Improves Neurobehavioral Outcome in Models of Intracerebral Hemorrhage

In models of acute brain injury, progesterone improves recovery through several mechanisms including modulation of neuroinflammation. Secondary injury from neuroinflammation is a potential therapeutic target after intracerebral hemorrhage (ICH). For potential translation of progesterone as a clinical acute ICH therapeutic, the present study sought to define efficacy of exogenous progesterone administration in ICH-relevant experimental paradigms. Young and aged C57BL/6 male, female, and ovariectomized (OVX) mice underwent left intrastriatal collagenase (0.05-0.075 U) or autologous whole blood (35 μl) injection. Progesterone at varying doses (4-16 mg/kg) was administered at 2, 5, 24, 48, and 72 h after injury. Rotarod and Morris water maze latencies were measured on days 1-7 and days 28-31 after injury, respectively. Hematoma volume, brain water content (cerebral edema), complementary immunohistochemistry, multiplex cytokine arrays, and inflammatory proteins were assessed at prespecified time points after injury. Progesterone (4 mg/kg) administration improved rotarod and water maze latencies (p < 0.01), and decreased cerebral edema (p < 0.05), microglial proliferation, and neuronal loss (p < 0.01) in young and aged male, young OVX, and aged female mice. Brain concentration of proinflammatory cytokines and Toll-like receptor-associated proteins were also decreased after progesterone (4 mg/kg) treatment (p < 0.01). Progesterone-treated young female mice showed no detectable effects. Exogenous progesterone improved short- and long-term neurobehavioral recovery and modulated neuroinflammation in male and OVX mice after ICH. Future studies should validate these findings, and address timing and length of administration before translation to clinical trial.

Animal Stroke Model: Ischemia-Reperfusion and Intracerebral Hemorrhage

Stroke is a major health issue worldwide-one with serious financial and public health implications. As a result, ongoing clinical research on novel and improved stroke therapies is not only pertinent but also paramount. Due to the complexity of a stroke-like event and its many sequelae, devising usable methods and experimental models are necessary to study and better understand the pathophysiological processes that ensue. As it stands, animal models that simulate stroke-like events have proven to be the most logical and effective options in regards to experimental studies. A number of animal stroke models exist and have been demonstrated in previous studies on ischemic as well as hemorrhagic stroke. Considering the efficiency and reproducibility of animal models, here, we introduce an ischemic stroke model induced by middle cerebral artery occlusion (MCAO) and an intracerebral hemorrhagic stroke model induced by collagenase injection. The models outlined here have been proven to demonstrate the clinical relevance desired for use in continued research on stroke pathophysiology and the study of future therapeutic options.

Thrombin-induced microglial activation impairs hippocampal neurogenesis and spatial memory ability in mice

Background

To investigate the effects of microglia/macrophages activation induced by intrastriatal thrombin injection on dentate gyrus neurogenesis and spatial memory ability in mice.

Methods

The male C57BL/6 mice were divided into 4 groups of 10: sham, intracerebral hemorrhage (ICH), ICH + hirudin (thrombin inhibitor), and ICH + indometacin (Indo, an anti-inflammation drug). ICH model was created by intrastriatal thrombin (1U) injection. BrdU (50 mg/kg) was administrated on the same day after surgery for 6 consecutive days. Motor functions were evaluated with rotarod and beam walking tests. The spatial memory deficit was measured with Morris water maze (MWM). Cell quantification was performed for doublecortin (DCX, immature neuron), BrdU (S-phase proliferating cell population) and CD68 (activated microglia/macrophage) immune-reactive cells.

Results

Microglia/macrophages activation induced by intrastriatal thrombin injection reduced hippocampal neurogenesis and impaired spatial memory ability, but did not affect the motor function at 3 and 5 days post-injury. Both hirudin and indometacin reduced microglia/macrophages activation, enhanced hippocampal neurogenesis, and improved spatial memory ability in mice.

Conclusions

Microglia/macrophages activation induced by intrastriatal thrombin injection might be responsible for the spatial memory deficit. Targeting both thrombin and inflammation systems in acute phase of ICH might be important in alleviating the significant spatial memory deficits.

Stem cell-based therapies for intracerebral hemorrhage in animal model: a meta-analysis

Stem cell to be a new intervention for treating intracerebral hemorrhage (ICH) might benefit humans. Therefore, we collected animal studies to find the effect of this innovative treatment. In July 2014, we searched Medline (from 1950), Embase (from 1980), China Biology Medicine disk (from 1978) for studies on stem cells used for treating experimental ICH in animal models that reported neurobehavioral and structural outcome. We evaluated the quality of these studies and used a weighted mean difference random affects model for the meta-analysis. We have collected 30 studies from 650 publications identified through systematic review describing the effects of 5 different type of stem cells on 12 different neurobehavioral scales with 1101 rodents or monkeys. Although there is lack of uniformity of the evaluation methods, these researches showed consistent improvements both in neurobehavioral function and structural outcomes. Besides, the quality of these studies needs to be raised. In conclusion, stem cells hold extensive potential in treating ICH, which should be further evaluated with more evidence-based, high-quality animal studies.

Stem cell therapy in intracerebral hemorrhage rat model

Intracerebral hemorrhage (ICH) is a very complex pathology, with many different not fully elucidated etiologies and prognostics. It is the most severe subtype of stroke, with high mortality and morbidity rates. Unfortunately, despite the numerous promising preclinical assays including neuroprotective, anti-hypertensive, and anti-inflammatory drugs, to this moment only symptomatic treatments are available, motivating the search for new alternatives. In this context, stem cell therapy emerged as a promising tool. However, more than a decade has passed, and there is still much to be learned not only about stem cells, but also about ICH itself, and how these two pieces come together. To date, rats have been the most widely used animal model in this research field, and there is much more to be learned from and about them. In this review, we first summarize ICH epidemiology, risk factors, and pathophysiology. We then present different methods utilized to induce ICH in rats, and examine how accurately they represent the human disease. Next, we discuss the different types of stem cells used in previous ICH studies, also taking into account the tested transplantation sites. Finally, we summarize what has been achieved in assays with stem cells in rat models of ICH, and point out some relevant issues where attention must be given in future efforts.

Targeting heme oxygenase after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is the primary event in approximately 10% of strokes, and has higher rates of morbidity and mortality than ischemic stroke. Experimental evidence suggests that the toxicity of hemoglobin and its degradation products contributes to secondary injury that may be amenable to therapeutic intervention. Hemin, the oxidized form of heme, accumulates in intracranial hematomas to cytotoxic levels. The rate limiting step of its breakdown is catalyzed by the heme oxygenase (HO) enzymes, which consist of inducible HO-1 and constitutively-expressed HO-2. The effect of these enzymes on perihematomal injury and neurological outcome has been investigated in ICH models using both genetic and pharmacological approaches to alter their expression, with variable results reported. These findings are summarized and reconciled in this review; therapeutic strategies that may optimize HO expression and activity after ICH are described.

Neuroinflammation after intracerebral hemorrhage

Spontaneous intracerebral hemorrhage (ICH) is a particularly severe type of stroke for which no specific treatment has been established yet. Although preclinical models of ICH have substantial methodological limitations, important insight into the pathophysiology has been gained. Mounting evidence suggests an important contribution of inflammatory mechanisms to brain damage and potential repair. Neuroinflammation evoked by intracerebral blood involves the activation of resident microglia, the infiltration of systemic immune cells and the production of cytokines, chemokines, extracellular proteases and reactive oxygen species (ROS). Previous studies focused on innate immunity including microglia, monocytes and granulocytes. More recently, the role of adaptive immune cells has received increasing attention. Little is currently known about the interactions among different immune cell populations in the setting of ICH. Nevertheless, immunomodulatory strategies are already being explored in ICH. To improve the chances of translation from preclinical models to patients, a better characterization of the neuroinflammation in patients is desirable.

Seizure activity occurs in the collagenase but not the blood infusion model of striatal hemorrhagic stroke in rats

Seizures are a frequent complication of brain injury, including intracerebral hemorrhage (ICH), where seizures occur in about a third of patients. Rodents are used to study pathophysiology and neuroprotective therapies after ICH, but there have been no studies assessing the occurrence of seizures in these models. Thus, we compared seizure incidence and characteristics after infusing collagenase (0.14 U), which degrades blood vessels, and autologous blood (100 μL) into the striatum of rats. Saline was infused in others as a negative control, whereas iron, a by-product of degrading erythrocytes, served as a positive control. Ipsilateral and contralateral electroencephalographic (EEG) activity was continuously monitored with telemetry probes for a week after the stroke. There were no electrographic abnormalities during baseline recordings. As expected, saline did not elicit any epileptiform activity whereas iron caused seizure activity. Seizures occurred in 66 % of the collagenase group between 10 and 36 h, their duration ranged from 5 to 90 s, and these events were mostly observed bilaterally. No such activity occurred after blood infusion despite comparable lesion sizes of 32.5 and 40.9 mm³ in the collagenase and blood models, respectively (p = 0.222). Therefore, seizures are a common acute occurrence in the collagenase but not whole blood models of striatal ICH (p = 0.028, for incidence). These findings have potential implications for ICH studies such as for understanding model differences, helping select which model to use, and determining how seizures may affect or be affected by treatments applied after stroke.

Intrastriatal injection of autologous blood or clostridial collagenase as murine models of intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a common form of cerebrovascular disease and is associated with significant morbidity and mortality. Lack of effective treatment and failure of large clinical trials aimed at hemostasis and clot removal demonstrate the need for further mechanism-driven investigation of ICH. This research may be performed through the framework provided by preclinical models. Two murine models in popular use include intrastriatal (basal ganglia) injection of either autologous whole blood or clostridial collagenase. Since, each model represents distinctly different pathophysiological features related to ICH, use of a particular model may be selected based on what aspect of the disease is to be studied. For example, autologous blood injection most accurately represents the brain's response to the presence of intraparenchymal blood, and may most closely replicate lobar hemorrhage. Clostridial collagenase injection most accurately represents the small vessel rupture and hematoma evolution characteristic of deep hemorrhages. Thus, each model results in different hematoma formation, neuroinflammatory response, cerebral edema development, and neurobehavioral outcomes. Robustness of a purported therapeutic intervention can be best assessed using both models. In this protocol, induction of ICH using both models, immediate post-operative demonstration of injury, and early post-operative care techniques are demonstrated. Both models result in reproducible injuries, hematoma volumes, and neurobehavioral deficits. Because of the heterogeneity of human ICH, multiple preclinical models are needed to thoroughly explore pathophysiologic mechanisms and test potential therapeutic strategies.

Leukocyte invasion of the brain after experimental intracerebral hemorrhage in mice

BACKGROUND AND PURPOSE

Neuroinflammatory processes contribute to secondary neuronal damage after intracerebral hemorrhage. We aimed to characterize the time course of brain immigration of different leukocyte subsets after striatal injection of either autologous blood or collagenase in mice.

METHODS

Intracerebral hemorrhage was induced by injection of either autologous blood (20 μL) or collagenase (0.03 U) in C57Bl/6J mice. Hematoma volumetry was performed on cryosections. Blood volume was measured by hemoglobin spectrophotometry. Leukocytes were isolated from hemorrhagic hemisphere 1, 3, 5, and 14 days after intracerebral hemorrhage, stained for leukocyte markers, and measured by flow cytometry. Heterologous blood injection from CD45.1 mice was used to investigate the origin of brain-invading leukocytes.

RESULTS

Collagenase injection induced a larger hematoma volume but a similar blood content compared with blood injection. Cerebral leukocyte infiltration in the hemorrhagic hemisphere was similar in both models. The majority of leukocytes isolated from the brain originated from the circulation. CD4+ T lymphocytes were the predominant brain leukocyte population in both models. However, cerebral granulocyte counts were higher after collagenase compared with blood injection.

CONCLUSIONS

Brain infiltration of systemic immune cells is similar in both murine intracerebral hemorrhage models. The pathophysiological impact of invading leukocytes and, in particular, of T cells requires further investigation.

Suppression of CXCL2 upregulation underlies the therapeutic effect of the retinoid Am80 on intracerebral hemorrhage in mice

We previously demonstrated that a synthetic retinoic acid receptor agonist, Am80, attenuated intracerebral hemorrhage (ICH)-induced neuropathological changes and neurological dysfunction. Because inflammatory events are among the prominent features of ICH pathology that are affected by Am80, this study investigated the potential involvement of proinflammatory cytokines/chemokines in the effect of Am80 on ICH. ICH induced by collagenase injection into mouse striatum caused prominent upregulation of mRNAs for interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-6, CXCL1, CXCL2, and CCL3. We found that dexamethasone (DEX) and Am80 differently modulated the increase in expression of these cytokines/chemokines; TNF-α expression was attenuated only by DEX, whereas CXCL2 expression was attenuated only by Am80. Expression of IL-1β and IL-6 was inhibited both by DEX and Am80. Neurological assessments revealed that Am80, but not DEX, significantly alleviated motor dysfunction of mice after ICH. From these results, we suspected that CXCL2 might be critically involved in determining the extent of motor dysfunction. Indeed, magnetic resonance imaging-based classification of ICH in individual mice revealed that invasion of hematoma into the internal capsule, which has been shown to cause severe neurological disabilities, was associated with higher levels of CXCL2 expression than ICH without internal capsule invasion. Moreover, a CXCR1/2 antagonist reparixin ameliorated neurological deficits after ICH. Overall, suppression of CXCL2 expression may contribute to the beneficial effect of Am80 as a therapeutic agent for ICH, and interruption of CXCL2 signaling may provide a promising target for ICH therapy.

Interaction between sex and apolipoprotein e genetic background in a murine model of intracerebral hemorrhage

Emerging evidence suggests sex and apolipoprotein E (APOE) genotype separately modify outcomes after intracerebral hemorrhage (ICH). We test the hypothesis that an interaction exists between sex and APOE polymorphism in modifying outcomes after ICH and is altered by administration of exogenous apoE-mimetic peptide. To define the effects of sex and APOE polymorphism in ICH, we created collagenase-induced ICH in male and female APOETR mice (targeted replacement mice homozygous for APOE3 or APOE4 alleles; n=12/group) and assessed performance on Rotarod (RR) and Morris water maze (MWM). To evaluate hematoma formation, we used hematoxylin and eosin staining at 24 h after injury (n=8/group). Using separate cohorts (n=12/group), apoE-mimetic peptide (COG1410 at 2 mg/kg) was administered after ICH, and mice were assessed by RR and MWM. Female mice outperformed male mice via RR and MWM by over 190% improvement through 7 days (RR) and 32 days (MWM) of testing after ICH (p<0.01). Female APOE3TR mice demonstrated improved function compared with all other groups (p<0.05) without any difference in hematoma volume at 24 h after injury in any group. Administration of a therapeutic apoE-mimetic peptide improved RR latencies through 7 days after ICH in male and female APOE4TR mice and MWM latencies over days 28-32 after ICH in male APOE4TR mice (p<0.05). Sex and APOE polymorphism influence functional outcomes in our murine model of ICH. Moreover, administration of exogenous apoE-mimetic peptide after injury differentially modifies the interaction between sex and APOE polymorphism.

Quantitative gait analysis of long-term locomotion deficits in classical unilateral striatal intracerebral hemorrhage rat model

Gait analysis is a systematic collection of quantitative information on bodily movements during locomotion. Gait analysis has been employed clinically in stroke patients for their rehabilitation planning. In animal studies, gait analysis has been employed for the assessment of their locomotive disturbances in ischemic stroke, spinal cord injury and Parkinson's disease. The aims of the work reported here were to identify the gait parameters, collected from the computer-generated CatWalk System, that change after unilateral intracerebral hemorrhage (ICH) in the acute stage and long term up to 56 days post-ICH. The results showed that with the collagenase-induced unilateral striatal lesion, the rats displayed a significant contralateral decrease in print and maximum contact area and paw intensity, a diagonal increase in the stance duration of the left front and right hind paws, a significant decrease in the stride length of all four limbs, and foot pattern instability as reflected by the base of support, support on styles, and cadence. These deficits, including those in print area, stance and pressure, were demonstrated throughout the long-term period following ICH. The correlations between the gait parameters, lesion volume and asymmetrical forelimb use were also reported in this paper. This work has provided a systematic description on gait parameters in the classical striatal ICH model, which might become an essential assessment tool in future studies of pathophysiology and the development of novel treatments for experimental unilateral intracerebral hemorrhage with gait deficits.

A rapid fluorescent method to quantify neuronal loss after experimental intracerebral hemorrhage

Neuronal loss in tissue surrounding an intracerebral hemorrhage (ICH) is usually quantified by labor-intensive histological methods that are subject to bias. Fluorescent protein expression has been successfully used as a marker of cell viability in vitro and in retinal studies in vivo, but not in any ICH model to date. The potential of this approach was investigated using transgenic mice that constitutively express the red fluorescent protein variant dTomato in central neurons under the control of the Thy1 promoter. Breeding and growth of these mice were similar to their wild-type counterparts; behavioral phenotyping by digital analysis of home cage video recordings detected no differences. Bright fluorescence was evident in fresh brain samples with minimal background fluorescence, and was reduced in tissue surrounding the hematoma. In order to assess fluorescence loss as an injury marker in a planned study, these mice were crossed with heme oxygenase (HO)-2 knockouts and wild-type controls; striatal hemorrhage was induced by stereotactic injection of collagenase. Fluorescence in hemorrhagic striata was reduced to 86.4±3.9%, 62.2±5.1%, and 58.3±3.0% of contra-lateral on days 1, 4 and 8, respectively, and correlated closely with reduction in striatal cell viability as quantified by MTT assay. HO-2 knockout and wild-type values did not differ significantly. Similar results were observed with stereological cell counts of striatal neurons identified by NeuN immunoreactivity. These results suggest that loss of constitutive dTomato fluorescence is an accurate and efficient marker of neuronal loss in tissue surrounding a striatal hematoma.

Thrombin and hemin as central factors in the mechanisms of intracerebral hemorrhage-induced secondary brain injury and as potential targets for intervention

Intracerebral hemorrhage (ICH) is a subtype of stoke that may cause significant morbidity and mortality. Brain injury due to ICH initially occurs within the first few hours as a result of mass effect due to hematoma formation. However, there is increasing interest in the mechanisms of secondary brain injury as many patients continue to deteriorate clinically despite no signs of rehemorrhage or hematoma expansion. This continued insult after primary hemorrhage is believed to be mediated by the cytotoxic, excitotoxic, oxidative, and inflammatory effects of intraparenchymal blood. The main factors responsible for this injury are thrombin and erythrocyte contents such as hemoglobin. Therapies including thrombin inhibitors, N-methyl-D-aspartate antagonists, chelators to bind free iron, and antiinflammatory drugs are currently under investigation for reducing this secondary brain injury. This review will discuss the molecular mechanisms of brain injury as a result of intraparenchymal blood, potential targets for therapeutic intervention, and treatment strategies currently in development.

Modeling intracerebral hemorrhage in mice: injection of autologous blood or bacterial collagenase

Spontaneous intracerebral hemorrhage (ICH) defines a potentially life-threatening neurological malady that accounts for 10-15% of all stroke-related hospitalizations and for which no effective treatments are available to date(1,2). Because of the heterogeneity of ICH in humans, various preclinical models are needed to thoroughly explore prospective therapeutic strategies(3). Experimental ICH is commonly induced in rodents by intraparenchymal injection of either autologous blood or bacterial collagenase(4). The appropriate model is selected based on the pathophysiology of hemorrhage induction and injury progression. The blood injection model mimics a rapidly progressing hemorrhage. Alternatively, bacterial collagenase enzymatically disrupts the basal lamina of brain capillaries, causing an active bleed that generally evolves over several hours(5). Resultant perihematomal edema and neurofunctional deficits can be quantified from both models. In this study, we described and evaluated a modified double injection model of autologous whole blood(6) as well as an ICH injection model of bacterial collagenase(7), both of which target the basal ganglia (corpus striatum) of male CD-1 mice. We assessed neurofunctional deficits and brain edema at 24 and 72 hr after ICH induction. Intrastriatal injection of autologous blood (30 μl) or bacterial collagenase (0.075U) caused reproducible neurofunctional deficits in mice and significantly increased brain edema at 24 and 72 hr after surgery (p<0.05). In conclusion, both models yield consistent hemorrhagic infarcts and represent basic methods for preclinical ICH research.

Etiology of stroke and choice of models

Animal models of stroke contribute to the development of better stroke prevention and treatment through studies investigating the pathophysiology of different stroke subtypes and by testing promising treatments before trials in humans. There are two broad types of animal models: those in which stroke is induced through artificial means, modeling the consequences of a vascular insult but not the vascular pathology itself; and those in which strokes occur spontaneously. Most animal models of stroke are in rodents due to cost, ethical considerations, availability of standardized neurobehavioral assessments, and ease of physiological monitoring. While there are similarities in cerebrovascular anatomy and pathophysiology between rodents and humans, there are also important differences, including brain size, length and structure of perforating arteries, and gray to white matter ratio, which is substantially lower in humans. The wide range of rodent models of stroke includes models of global and focal ischemia, and of intracerebral and sub-arachnoid hemorrhage. The most widely studied model of spontaneous stroke is the spontaneously hypertensive stroke-prone rat, in which the predominant lesions are small subcortical infarcts resulting from a vascular pathology similar to human cerebral small vessel disease. Important limitations of animal models of stroke - they generally model only certain aspects of the disease and do not reflect the heterogeneity in severity, pathology and comorbidities of human stroke - and key methodological issues (especially the need for adequate sample size, randomization, and blinding in treatment trials) must be carefully considered for the successful translation of pathophysiological concepts and therapeutics from bench to bedside.

Elevated blood pressure causes larger hematoma in a rat model of intracerebral hemorrhage

Hypertension has been recognized as an independent risk factor for intracerebral hemorrhage (ICH). The objective of this study was to assess the effect of chronically elevated blood pressure on amount of hematoma in a rat model of ICH. A total of 46 rats were divided into two groups-normotensive group (n = 18) and spontaneously hypertensive group (n = 28). To induce ICH, we delivered 2 μL of collagenase solution (0.1 U/1 μL normal saline) into the striatum. Each animal's brain was removed 24 h post-surgery for spectrophotometric hemoglobin assay. Equal or unequal variance t tests were performed to assess changes in variables between the hypertensive and normotensive groups. Tissue analysis revealed a statistically significant difference in optical density percent change at 540-nm wavelength for the hypertensive vs. the normotensive group (261.47 ± 103.68 and 133.33 ± 58.53, p < 0.0001, respectively). As compared to the normotensive rats, hypertensive rats exhibited a higher neurological deficit, loss of balance and coordination, and loss of motor function. Our results demonstrated that hypertensive rats had significantly higher amounts of hemorrhage in comparison to normotensive ones. These findings support the need for further adequately powered studies to investigate differences in amount of hematoma and corresponding functional impairments due to ICH among hypertensive vs. normotensive rats.

The apoE-mimetic peptide, COG1410, improves functional recovery in a murine model of intracerebral hemorrhage

BACKGROUND

Apolipoprotein E has previously been demonstrated to modulate acute brain injury responses, and administration of COG1410, an apoE-mimetic peptide derived from the receptor-binding region of apoE, improves outcome in preclinical models of acute neurological injury. In the current study, we sought to establish the optimal dose and timing of peptide administration associated with improved functional outcome in a murine model of intracerebral hemorrhage (ICH).

METHODS

Ten to twelve-week-old C57/BL6 male mice were injured by collagenase-induced ICH and randomly selected to receive either vehicle or one of four doses of COG1410 (0.5, 1, 2, or 4 mg/kg) via tail vein injection at 30 min after injury and then daily for 5 days. The injured mice were euthanized at various time points to assess inflammatory mediators, cerebral edema, and hematoma volume. Over the first 5 days following injury, vestibulomotor function was tested via Rotorod (RR) latency. After an optimal dose was demonstrated, a final cohort of animals was injured with ICH and randomly assigned to receive the first dose of COG1410 or vehicle at increasingly longer treatment initiation times after injury. The mice were then assessed for functional deficit via RR testing over the first 5 days following injury.

RESULTS

The mice receiving 2 mg/kg of COG1410 after injury demonstrated reduced functional deficit, decreased brain concentrations of inflammatory proteins, and less cerebral edema, although hematoma volume did not vary. The improved RR performance was maintained when peptide administration was delayed for up to 2 h after ICH.

CONCLUSIONS

COG1410 administered at a dose of 2 mg/kg within 2 h after injury improves functional recovery in a murine model of ICH.

Statins improve outcome in murine models of intracranial hemorrhage and traumatic brain injury: a translational approach

Traumatic brain injury (TBI) and intracerebral hemorrhage (ICH) are leading causes of neurological mortality and disability in the U.S. However, therapeutic options are limited and clinical management remains largely supportive. HMG-CoA reductase inhibitors (statins) have pleiotropic mechanisms of action in the setting of acute brain injury, and have been demonstrated to improve outcomes in preclinical models of ICH and TBI. To facilitate translation to clinical practice, we now characterize the optimal statin and dosing paradigm in murine models of ICH and TBI. In a preclinical model of TBI, mice received vehicle, simvastatin, and rosuvastatin at doses of 1 mg/kg and 5 mg/kg for 5 days after the impact. Immunohistochemistry, differential gene expression, and functional outcomes (rotarod and Morris water maze testing) were assessed to gauge treatment response. Following TBI, administration of rosuvastatin 1 mg/kg was associated with the greatest improvement in functional outcomes. Rosuvastatin treatment was associated with histological evidence of reduced neuronal degeneration at 24 h post-TBI, reduced microgliosis at day 7 post-TBI, and preserved neuronal density in the CA3 region at 35 days post-injury. Administration of rosuvastatin following TBI was also associated with downregulation of inflammatory gene expression in the brain. Following ICH, treatment with simvastatin 1 mg/kg was associated with the greatest improvement in functional outcomes, an effect that was independent of hemorrhage volume. Clinically relevant models of acute brain injury may be used to define variables such as optimal statin and dosing paradigms to facilitate the rational design of pilot clinical trials.

A critical appraisal of experimental intracerebral hemorrhage research

The likelihood of translating therapeutic interventions for stroke rests on the quality of preclinical science. Given the limited success of putative treatments for ischemic stroke and the reasons put forth to explain it, we sought to determine whether such problems hamper progress for intracerebral hemorrhage (ICH). Approximately 10% to 20% of strokes result from an ICH, which results in considerable disability and high mortality. Several animal models reproduce ICH and its underlying pathophysiology, and these models have been widely used to evaluate treatments. As yet, however, none has successfully translated. In this review, we focus on rodent models of ICH, highlighting differences among them (e.g., pathophysiology), issues with experimental design and analysis, and choice of end points. A Pub Med search for experimental ICH (years: 2007 to 31 July 2011) found 121 papers. Of these, 84% tested neuroprotectants, 11% tested stem cell therapies, and 5% tested rehabilitation therapies. We reviewed these to examine study quality (e.g., use of blinding procedures) and choice of end points (e.g., behavioral testing). Not surprisingly, the problems that have plagued the ischemia field are also prevalent in ICH literature. Based on these data, several recommendations are put forth to facilitate progress in identifying effective treatments for ICH.

Experimental intracerebral hemorrhage: avoiding pitfalls in translational research

Intracerebral hemorrhage (ICH) has the highest mortality of all stroke subtypes, yet treatments are mainly limited to supportive management, and surgery remains controversial. Despite significant advances in our understanding of ICH pathophysiology, we still lack preclinical models that accurately replicate the underlying mechanisms of injury. Current experimental ICH models (including autologous blood and collagenase injection) simulate different aspects of ICH-mediated injury but lack some features of the clinical condition. Newly developed models, notably hypertension- and oral anticoagulant therapy-associated ICH models, offer added benefits but further study is needed to fully validate them. Here, we describe and discuss current approaches to experimental ICH, with suggestions for changes in how this condition is studied in the laboratory. Although advances in imaging over the past few decades have allowed greater insight into clinical ICH, there remains an important role for experimental models in furthering our understanding of the basic pathophysiologic processes underlying ICH, provided limitations of animal models are borne in mind. Owing to differences in existing models and the failed translation of benefits in experimental ICH to clinical practice, putative neuroprotectants should be trialed in multiple models using both histological and functional outcomes until a more accurate model of ICH is developed.

Comparison of humoral neuroinflammation and adhesion molecule expression in two models of experimental intracerebral hemorrhage

Background

Inflammatory cascades contribute to secondary injury after intracerebral hemorrhage (ICH) via humoral factors and cell-mediated cytotoxicity. Several experimental models were previously developed to analyze post-hemorrhagic neuroinflammation. However, neuroinflammatory markers have not been compared face-to-face between these models so far, and therefore, pathophysiological conclusions drawn from only one individual model may not be valid.

Methods

We compared neuroinflammatory pathways in the two most common murine models: striatal injection of autologous blood or collagenase. Expression of pro- and anti-inflammatory cytokines (IL-1, TNF-α, IFN-γ, IL-6, TGF-β and IL-10) as well adhesion molecule expression (VCAM-1, ICAM-1) was analyzed by RT-PCR at several time points after ICH induction. Outcome and physiological parameters were compared between the models.

Results

Both models induced a profound and dynamic increase in the expression of pro-inflammatory cytokines and adhesion molecules. However, blood injection resulted in significantly more pronounced alteration of these markers than collagenase injection. This difference was associated with worse outcome after blood injection compared to the collagenase model despite equal ICH volumes.

Conclusions

This is the first study performing a face-to-face comparison of neuroinflammatory pathways in the two most widely used murine ICH models, revealing substantial differences between the models. This discrepancies need to be taken into account in designing future studies employing experimental ICH models, especially when analyzing neuroinflammatory pathways and therapies.