Why do neuroprotective drugs work in animals but not humans?

A multi-laboratory preclinical trial in rodents to assess treatment candidates for acute ischemic stroke

Human diseases may be modeled in animals to allow preclinical assessment of putative new clinical interventions. Recent, highly publicized failures of large clinical trials called into question the rigor, design, and value of preclinical assessment. We established the Stroke Preclinical Assessment Network (SPAN) to design and implement a randomized, controlled, blinded, multi-laboratory trial for the rigorous assessment of candidate stroke treatments combined with intravascular thrombectomy. Efficacy and futility boundaries in a multi-arm multi-stage statistical design aimed to exclude from further study highly effective or futile interventions after each of four sequential stages. Six independent research laboratories performed a standard focal cerebral ischemic insult in five animal models that included equal numbers of males and females: young mice, young rats, aging mice, mice with diet-induced obesity, and spontaneously hypertensive rats. The laboratories adhered to a common protocol and efficiently enrolled 2615 animals with full data completion and comprehensive animal tracking. SPAN successfully implemented treatment masking, randomization, prerandomization inclusion and exclusion criteria, and blinded assessment of outcomes. The SPAN design and infrastructure provide an effective approach that could be used in similar preclinical, multi-laboratory studies in other disease areas and should help improve reproducibility in translational science.

Ischemic Stroke, Lessons from the Past towards Effective Preclinical Models

Ischemic stroke is a leading cause of death worldwide, mainly in western countries. So far, approved therapies rely on reperfusion of the affected brain area, by intravenous thrombolysis or mechanical thrombectomy. The last approach constitutes a breakthrough in the field, by extending the therapeutic window to 16-24 h after stroke onset and reducing stroke mortality. The combination of pharmacological brain-protective strategies with reperfusion is the future of stroke therapy, aiming to reduce brain cell death and decrease patients' disabilities. Recently, a brain-protective drug-nerinetide-reduced brain infarct and stroke mortality, and improved patients' functional outcomes in clinical trials. The success of new therapies relies on bringing preclinical studies and clinical practice close together, by including a functional outcome assessment similar to clinical reality. In this review, we focused on recent upgrades of in vitro and in vivo stroke models for more accurate and effective evaluation of therapeutic strategies: from spheroids to organoids, in vitro models that include all brain cell types and allow high throughput drug screening, to advancements in in vivo preclinical mouse stroke models to mimic the clinical reality in surgical procedures, postsurgical care, and functional assessment.

Inhalation of Atmospheric-Pressure Gas Plasma Attenuates Brain Infarction in Rats With Experimental Ischemic Stroke

Previous studies suggest the potential efficacy of neuroprotective effects of gaseous atmospheric-pressure plasma (APP) treatment on neuronal cells. However, it remains unclear if the neuroprotective properties of the gas plasmas benefit the ischemic stroke treatment, and how to use the plasmas in the in vivo ischemic stroke models. Rats were subjected to 90 min middle cerebral artery occlusion (MCAO) to establish the ischemic stroke model and then intermittently inhaled the plasma for 2 min at 60 min MCAO. The regional cerebral blood flow (CBF) was monitored. Animal behavior scoring, magnetic resonance imaging (MRI), 2,3,5-triphenyltetrazolium chloride (TTC) staining, and hematoxylin and eosin (HE) staining were performed to evaluate the therapeutic efficacy of the gas plasma inhalation on MCAO rats. Intermittent gas plasma inhalation by rats with experimental ischemic stroke could improve neurological function, increase regional CBF, and decrease brain infarction. Further MRI tests showed that the gas plasma inhalation could limit the ischemic lesion progression, which was beneficial to improve the outcomes of the MCAO rats. Post-stroke treatment with intermittent gas plasma inhalation could reduce the ischemic lesion progression and decrease cerebral infarction volume, which might provide a new promising strategy for ischemic stroke treatment.

Cerebroprotection for Acute Ischemic Stroke: Looking Ahead

We search for ischemic stroke treatment knowing we have failed-intensely and often-to translate mechanistic knowledge into treatments that alleviate our patients' functional impairments. Lessons can be derived from our shared failures that may point to new directions and new strategies. First, the principle criticisms of both preclinical and clinical assessments are summarized. Next, previous efforts to develop single-mechanism treatments are reviewed. Finally, new definitions, novel approaches, and different directions are presented. In previous development efforts, the basic science and preclinical assessment of candidate treatments often lacked rigor and sufficiency; the clinical trials may have lacked power, rigor, or rectitude; or most likely both preclinical and clinical investigations were flawed. Single-target agents directed against specific molecular mechanisms proved unsuccessful. The term neuroprotection should be replaced as it has become ambiguous: protection of the entire neurovascular unit may be called cerebral cytoprotection or cerebroprotection. Success in developing cerebroprotection-either as an adjunct to recanalization or as stand-alone treatment-will require new definitions that recognize the importance of differential vulnerability in the neurovascular unit. Recent focus on pleiotropic multi-target agents that act via multiple mechanisms of action to interrupt ischemia at multiple steps may be more fruitful. Examples of pleiotropic treatments include therapeutic hypothermia and 3K3A-APC (activated protein C). Alternatively, the single-target drug NA-1 triggers multiple downstream signaling events. Renewed commitment to scientific rigor is essential, and funding agencies and journals may enforce quality principles of rigor in preclinical science. Appropriate animal models should be selected that are suited to the purpose of the investigation. Before clinical trials, preclinical assessment could include subjects that are aged, of both sexes, and harbor comorbid conditions such as diabetes or hypertension. With these new definitions, novel approaches, and renewed attention to rigor, the prospect for successful cerebroprotective therapy should improve.

Activation of microglial G‑protein-coupled receptor 30 protects neurons against excitotoxicity through NF-κB/MAPK pathways

Neuroexcitotoxicity is a common feature in neuronal damage and neurodegenerative diseases. Our previous studies have confirmed that neuronal and astrocytic G‑protein-coupled receptor 30 (GPR30) play a key role in neuroprotection in vivo and in vitro. Microglia are considered as immune cells in the central nervous system. However, the role of microglial GPR30 in neuroprotection against neuroexcitotoxicity remained unclear. In this study, MTT, Western blot, immunocytochemical staining, phagocytosis assay and wound healing assay were employed to detect the effect of GPR30 in N9 microglial cells after exposure to glutamate. We found that the treatment of GPR30 specific agonist G1 inhibited glutamate-induced proliferation and activation in N9 microglial cells. G1 inhibited M1 polarization, facilitated M2 polarization, and decreased over-phagocytosis but had no effect on migration ability in microglia. The result of neurons and microglia co-culture showed that the activation of microglial GPR30 protected neurons from excitotoxicity through the NF-κB/MAPK signaling pathways. Our findings suggested a key role of microglial GPR30 in excitatory neuronal damage and neurodegenerative diseases.

Are researchers moving away from animal models as a result of poor clinical translation in the field of stroke? An analysis of opinion papers

Objectives

Despite decades of research using animals to develop pharmaceutical treatments for patients who have had a stroke, few therapeutic options exist. The vast majority of interventions successful in preclinical animal studies have turned out to have no efficacy in humans or to be harmful to humans. In view of this, we explore whether there is evidence of a move away from animal models in this field.

Methods

We used an innovative methodology, the analysis of opinion papers. Although we took a systematic approach to literature searching and data extraction, this is not a systematic review because the study involves the synthesis of opinions, not research evidence. Data were extracted from retrieved papers in chronological order and analysed qualitatively and descriptively.

Results

Eighty eligible papers, published between 1979 and 2018, were identified. Most authors were from academic departments of neurology, neuroscience or stroke research. Authors agreed that translational stroke research was in crisis. They held diverse views about the causes of this crisis, most of which did not fundamentally challenge the use of animal models. Some, however, attributed the translational crisis to animal–human species differences and one to a lack of human in vitro models. Most of the proposed solutions involved fine-tuning animal models, but authors disagreed about whether such modifications would improve translation. A minority suggested using human in vitro methods alongside animal models. One proposed focusing only on human in vitro methods.

Conclusion

Despite recognising that animal models have been unsuccessful in the field of stroke, most researchers exhibited a strong resistance to relinquishing them. Nevertheless, there is an emerging challenge to the use of animal models, in the form of human-focused in vitro approaches. For the sake of stroke patients there is an urgent need to revitalise translational stroke research and explore the evidence for these new approaches.

MicroRNA-122 Mimic Improves Stroke Outcomes and Indirectly Inhibits NOS2 After Middle Cerebral Artery Occlusion in Rats

Aim: Our previous study demonstrated miR-122 mimic decreased NOS2 expression in blood leucocytes and improved stroke outcomes when given immediately after middle cerebral artery occlusion (MCAO) in rats. Since NOS2 is associated with neuro-inflammation in stroke and decreasing NOS2 expression alone in leucocytes is insufficient to improve stroke outcomes, we hypothesized that miR-122 mimic may also decrease NOS2 expression in brain microvascular endothelial cells (BMVECs) even at extended time windows.

Methods: We administered PEG-liposome wrapped miR-122 mimic (2.4 mg/kg, i.v.) 0 or 6 h after MCAO, and assessed stroke volume and NOS2 expression in BMVECs 24 h following MCAO in rats. Luciferase reporter assays were used to determine if miR-122 binds to 3′ untranslated regions (3′UTR) of NOS2.

Results: The data showed that miR-122 mimic decreased infarct volumes and decreased MCAO-induced NOS2 over-expression in BMVECs. However, miR-122 did not bind to 3′UTR of NOS2 in the luciferase assays.

Conclusion: The data show the 6-h period of therapeutic efficacy of miR-122 mimic which could relate to indirect knockdown of NOS2 in both BMVECs and leucocytes.

Magnesium in man: implications for health and disease

Magnesium (Mg(2+)) is an essential ion to the human body, playing an instrumental role in supporting and sustaining health and life. As the second most abundant intracellular cation after potassium, it is involved in over 600 enzymatic reactions including energy metabolism and protein synthesis. Although Mg(2+) availability has been proven to be disturbed during several clinical situations, serum Mg(2+) values are not generally determined in patients. This review aims to provide an overview of the function of Mg(2+) in human health and disease. In short, Mg(2+) plays an important physiological role particularly in the brain, heart, and skeletal muscles. Moreover, Mg(2+) supplementation has been shown to be beneficial in treatment of, among others, preeclampsia, migraine, depression, coronary artery disease, and asthma. Over the last decade, several hereditary forms of hypomagnesemia have been deciphered, including mutations in transient receptor potential melastatin type 6 (TRPM6), claudin 16, and cyclin M2 (CNNM2). Recently, mutations in Mg(2+) transporter 1 (MagT1) were linked to T-cell deficiency underlining the important role of Mg(2+) in cell viability. Moreover, hypomagnesemia can be the consequence of the use of certain types of drugs, such as diuretics, epidermal growth factor receptor inhibitors, calcineurin inhibitors, and proton pump inhibitors. This review provides an extensive and comprehensive overview of Mg(2+) research over the last few decades, focusing on the regulation of Mg(2+) homeostasis in the intestine, kidney, and bone and disturbances which may result in hypomagnesemia.

Incomplete Assessment of Experimental Cytoprotectants in Rodent Ischemia Studies

Background:

Inadequate preclinical testing (e.g., rodent studies) has been partly blamed for the failure of many cytoprotectants to effectively treat stroke in humans. For example, some drugs went to clinical trial without rigorous functional and histological assessment over long survival times. In this study, we characterized recent experimental practices in rodent cytoprotection experiments to determine whether the limitations of early studies have been rectified.

Methods:

We identified 138 rodent cytoprotection studies published in several leading journals (Journal of Neuroscience, Stroke, Journal of Cerebral Blood Flow and Metabolism and Experimental Neurology) for 2000 - 2002 and compared these to those published in 1990. From each study we determined the ischemia model, age and sex of the animal, the histological and functional endpoints used, and the methodology used to assess intra- and postischemic temperature.

Results:

Ninety-eight percent of recent studies used young adult rodents and most used males. Most studies (60%) did not assess functional outcome and survival times were often ≤ 48 hr (66%) for focal ischemia and ≤ 7 days (80%) for global ischemia. Over 60% of the experiments relied solely upon rectal temperature during ischemia and only 32.6% of ischemia studies measured temperature after surgery. The 1990 data were similar.

Conclusion:

Many investigators ignore the need to assess long-term functional and histological outcome and do not accurately represent clinical conditions of ischemia (e.g., use of aged animals). In addition, intra- and postischemic temperature measurement and control is frequently neglected or inadequately performed. Further clinical failures are likely.

Fate of graft cells: what should be clarified for development of mesenchymal stem cell therapy for ischemic stroke?

Mesenchymal stem cells (MSCs) are believed to be promising for cell administration therapy after ischemic stroke. Because of their advantageous characteristics, such as ability of differentiation into neurovascular lineages, avoidance of immunological problems, and abundance of graft cells in mesodermal tissues, studies regarding MSC therapy have increased recently. However, several controversies are yet to be resolved before a worldwide consensus regarding a standard protocol is obtained. In particular, the neuroprotective effects, the rate of cell migration to the lesion, and differentiation direction differ depending on preclinical observations. Analyses of these differences and application of recent developments in stem cell biology or engineering in imaging modality may contribute to identification of criteria for optimal stem cell therapy in which reliable protocols, which control cell quality and include safe administration procedures, are defined for each recovery phase after cerebral ischemia. In this mini review, we examine controversies regarding the fate of grafts and the prospects for advanced therapy that could be obtained through recent developments in stem cell research as direct conversion to neural cells.

Magnesium: potential roles in neurovascular disease

OBJECTIVE

Magnesium therapy has been studied extensively in pre-clinical and clinical trials in multiple organ systems. Cerebrovascular diseases may benefit from its neuroprotective properties. This review summarizes current studies of magnesium in a wide range of neurovascular diseases.

METHODS

We searched relevant terms in the National Library of Medicine PubMed database and selected research including basic science, translational reports, meta-analyses, and clinical studies.

RESULTS

Studies examining magnesium administration in ischemic stroke have failed to show any benefit in clinical outcome. Data on magnesium for intracerebral hemorrhage (ICH) are limited. Preliminary investigations in subarachnoid hemorrhage (SAH) were promising, but definitive studies did not reveal differences in clinical outcome between magnesium and placebo-treated groups. Studies examining magnesium administration in global ischemia following cardiac arrest suggest a trend toward improved clinical outcome. The strongest evidence for clinically relevant neuroprotection following magnesium administration derives from studies of pre-term infants and patients undergoing cardiac bypass and carotid endarterectomy procedures. Magnesium was found to have an excellent safety profile across all investigations.

CONCLUSION

Magnesium is easy to administer and possesses a favorable safety profile. Its utility as a neuroprotectant in cardiac surgery, carotid endarterectomy, and pre-term infant hypoxia remain promising. Value as a therapeutic agent in ischemic stroke, ICH, and SAH is unclear and appears to be limited by late administration. Ongoing clinical trials assessing magnesium administration in the first hours following symptom onset may help clarify the role of magnesium therapy in these disease processes.

Correlation between subacute sensorimotor deficits and brain edema in two mouse models of intracerebral hemorrhage

Formation of brain edema after intracerebral hemorrhage (ICH) is highly associated with its poor outcome. However, the relationship between cerebral edema and behavioral deficits has not been thoroughly examined in the preclinical setting. Hence, this study aimed to evaluate the ability of common sensorimotor tests to predict the extent of brain edema in two mouse models of ICH. One hundred male CD-1 mice were subjected to sham surgery or ICH induction via intrastriatal injection of either autologous blood (30 μL) or bacterial collagenase (0.0375U or 0.075U). At 24 and 72 h after surgery, animals underwent a battery of behavioral tests, including the modified Garcia neuroscore (Neuroscore), corner turn test (CTT), forelimb placing test (FPT), wire hang task (WHT) and beam walking (BW). Brain edema was evaluated via the wet weight/dry weight method. Intrastriatal injection of autologous blood or bacterial collagenase resulted in a significant increase in brain water content and associated sensorimotor deficits (p<0.05). A significant correlation between brain edema and sensorimotor deficits was observed for all behavioral tests except for WHT and BW. Based on these findings, we recommend implementing the Neuroscore, CTT and/or FPT in preclinical studies of unilateral ICH in mice.

Differential effects of fresh frozen plasma and normal saline on secondary brain damage in a large animal model of polytrauma, hemorrhage and traumatic brain injury

BACKGROUND

We have previously shown that the extent of traumatic brain injury (TBI) in large animal models can be reduced with early infusion of fresh frozen plasma (FFP), but the precise mechanisms remain unclear. In this study, we investigated whether resuscitation with FFP or normal saline differed in their effects on cerebral metabolism and excitotoxic secondary brain injury in a model of polytrauma, TBI, and hemorrhagic shock.

METHODS

Yorkshire swine (n = 10) underwent Grade III liver injury, rib fracture, standardized TBI, and volume-controlled hemorrhage, (40% ± 5%) and were randomly resuscitated with either FFP or normal saline. Hemodynamic parameters and brain oxygenation were continuously monitored, while microdialysis was used to measure the brain concentrations of pyruvate, lactate, glutamate, and glycerol at baseline; 1 hour and 2 hours after shock; immediate postresuscitation (PR); as well as 2, 4, and 6 hours PR. Cells from the injured hemisphere were separated into mitochondrial and cytosolic fractions and analyzed for activity of the pyruvate dehydrogenase complex (PDH).

RESULTS

There were no baseline differences in cerebral perfusion pressure, brain oxygenation, as well as concentrations of pyruvate, lactate, glutamate, and glycerol between the groups. At 2 hours and 4 hours PR, the FFP group had significantly higher cerebral perfusion pressures (52 [5] mm Hg vs. 43 [2] mm Hg, p = 0.016; and 50 [7] mm Hg vs. 37 [1] mm Hg, p = 0.008, respectively). There was a sustained and significant (p < 0.05) drop in the glutamate and glycerol levels in the FFP group, implying a decrease in excitotoxicity and brain damage, respectively. Mitochondrial PDH activity was significantly higher (2,666.2 [638.2] adjusted volume INT × mm vs. 1,293.4 [88.8] adjusted volume INT × mm, p = 0.008), and cytosolic PDH activity was correspondingly lower (671.4 [209.2] adjusted volume INT × mm vs. 3070.7 [484.3] adjusted volume INT × mm, p < 0.001) in the FFP group, suggesting an attenuation of mitochondrial dysfunction and permeability.

CONCLUSION

In this model of TBI, polytrauma, and hemorrhage, FFP resuscitation confers neuroprotection by improving cerebral perfusion, diminishing glutamate-mediated excitotoxic secondary brain injury and reducing mitochondrial dysfunction.

A review of current imaging methods used in stroke research

Stroke is a serious healthcare problem with high mortality and long-term disability. However, to date, our ability to prevent and cure stroke remains limited. One important goal in stroke research is to identify the extent and location of lesion for treatment. In addition, accurately differentiating salvageable tissue from infarct and evaluating therapeutic efficacies are indispensible. These objectives could potentially be met with the assistance of modern neuroimaging techniques. This paper reviews current imaging methods commonly used in ischemic stroke research. These methods include positron emission tomography, computed tomography, T1 MRI, T2 MRI, diffusion and perfusion MRI, diffusion tensor imaging, blood-brain barrier permeability MRI, pH-weighted MRI, and functional MRI.

Brain ischemic injury in rodents: the protective effect of EPO

Animal models constitute an indispensable tool to investigate human pathology. Here we describe the procedure to induce permanent and transient cerebral ischemia in the mouse and the rat. The model of transient occlusion of the middle cerebral artery (MCA) is performed by the insertion of an occlusive filament until the origin of the MCA while the permanent occlusion described in the mice is performed by a distal electrocoagulation of the MCA. Those models allow evaluating the efficiency of therapeutic strategy of ischemia from tissular aspect to behavioral and cognitive impairment assessment. They were widely used in the literature to evaluate the efficiency of different drugs including the cytokines and especially erythropoietin (EPO) or its derivatives.

Steps to translate preconditioning from basic research to the clinic

Efforts to treat cardiovascular and cerebrovascular diseases often focus on the mitigation of ischemia-reperfusion (I/R) injury. Many treatments or "preconditioners" are known to provide substantial protection against the I/R injury when administered prior to the event. Brief periods of ischemia itself have been validated as a means to achieve neuroprotection in many experimental disease settings, in multiple organ systems, and in multiple species suggesting a common pathway leading to tolerance. In addition, pharmacological agents that act as potent preconditioners have been described. Experimental induction of neuroprotection using these various preconditioning paradigms has provided a unique window into the brain's endogenous protective mechanisms. Moreover, preconditioning agents themselves hold significant promise as clinical-stage therapies for prevention of I/R injury. The aim of this article is to explore several key steps involved in the preclinical validation of preconditioning agents prior to the conduct of clinical studies in humans. Drug development is difficult, expensive and relies on multi-factorial analysis of data from diverse disciplines. Importantly, there is no single path for the preclinical development of a novel therapeutic and no proven strategy to ensure success in clinical translation. Rather, the conduct of a diverse array of robust preclinical studies reduces the risk of clinical failure by varying degrees depending upon the relevance of preclinical models and drug pharmacology to humans. A strong sense of urgency and high tolerance of failure are often required to achieve success in the development of novel treatment paradigms for complex human conditions.

Peroxisome proliferator-activated receptors: "key" regulators of neuroinflammation after traumatic brain injury

Traumatic brain injury is characterized by neuroinflammatory pathological sequelae which contribute to brain edema and delayed neuronal cell death. Until present, no specific pharmacological compound has been found, which attenuates these pathophysiological events and improves the outcome after head injury. Recent experimental studies suggest that targeting peroxisome proliferator-activated receptors (PPARs) may represent a new anti-inflammatory therapeutic concept for traumatic brain injury. PPARs are “key” transcription factors which inhibit NFκB activity and downstream transcription products, such as proinflammatory and proapoptotic cytokines. The present review outlines our current understanding of PPAR-mediated neuroprotective mechanisms in the injured brain and discusses potential future anti-inflammatory strategies for head-injured patients, with an emphasis on the putative beneficial combination therapy of synthetic cannabinoids (e.g., dexanabinol) with PPARα agonists (e.g., fenofibrate).

A new model of cortical stroke in the rhesus macaque

Primate models are essential tools for translational research in stroke but are reportedly inconsistent in their ability to produce cortical infarcts of reproducible size. Here, we report a new stroke model using a transorbital, reversible, two-vessel occlusion approach in male rhesus macaques that produces consistent and reproducible cortical infarcts. The right middle cerebral artery (distal to the orbitofrontal branch) and both anterior cerebral arteries were occluded with vascular clips. Bilateral occlusion of the anterior cerebral artery was critical for reducing collateral flow to the ipsilateral cortex. Reversible ischemia was induced for 45, 60, or 90 mins (n=2/timepoint) and infarct volume and neurologic outcome were evaluated. The infarcts were located predominantly in the cortex and increased in size with extended duration of ischemia determined by T(2)-weighted magnetic resonance imaging . Infarct volume measured by 2,3,5-triphenyl tetrazolium chloride and cresyl violet staining corroborated magnetic resonance imaging results. Neurologic deficit scores worsened gradually with longer occlusion times. A subset of animals (n=5) underwent 60 mins of ischemia resulting in consistent infarct volumes primarily located to the cortex that correlated well with neurologic deficit scores. This approach offers promise for evaluating therapeutic interventions in stroke.

Bioethical considerations in translational research: primate stroke

Controversy and activism have long been linked to the subject of primate research. Even in the midst of raging ethical debates surrounding fertility treatments, genetically modified foods and stem-cell research, there has been no reduction in the campaigns of activists worldwide. Playing their trade of intimidation aimed at ending biomedical experimentation in all animals, they have succeeded in creating an environment where research institutions, often painted as guilty until proven innocent, have avoided addressing the issue for fear of becoming targets. One area of intense debate is the use of primates in stroke research. Despite the fact that stroke kills more people each year than AIDS and malaria, and less than 5% of patients are candidates for current therapies, there is significant opposition to primate stroke research. A balanced examination of the ethics of primate stroke research is thus of broad interest to all areas of biomedical research.

Magnetic resonance imaging in cerebral ischemia: focus on neonates

Magnetic resonance imaging (MRI) has dramatically changed our ability to diagnose and treat stroke as well as follow its evolution and response to treatment. Early stroke and ischemia can be visualized using diffusion-weighted imaging (DWI), which utilizes proton diffusion within tissues as a reporter for evolving neuropathology that reflects cytotoxic edema, particularly during the first several days after injury. Historically, T2-weighted imaging (T2WI) has been used for evaluation of vasogenic edema and also is a reliable indicator of injured tissue late after injury. While visual analysis of MR data can provide information about the evolution of injury, quantitative analyses allow definitive and objective evaluations of injury size and location and the effectiveness of novel therapeutic strategies. We review the clinical basis of imaging for stroke and ischemia diagnosis and the methods for post-processing of MR data that could provide novel insights into the evolution and pathophysiology of stroke in the newborn.

Nitrite does not provide additional protection to thrombolysis in a rat model of stroke with delayed reperfusion

An adjuvant therapy to prolong the therapeutic window for stroke patients is urgently needed. This randomized, blinded, placebo-controlled study investigated adjuvant intravenous sodium nitrite with recombinant tissue plasminogen activator (rtPA) in middle cerebral artery occlusion (MCAO) with 6 and 2 h of ischemia followed by reperfusion in Sprague-Dawley rats (n=59). Quantitative diffusion, T(1)-, T(2)-weighted, and semiquantitative perfusion imaging were performed before and after reperfusion and at 48 h after ischemia to determine the spatiotemporal evolution of stroke. After 48 h animals were killed and examined to evaluate infarct size and evidence of hemorrhagic transformation. Factor VIII immunostaining was performed to assess vessel morphology. Nitrite treatment (6 h group: 37.5 micromol for more than 90 mins; 2 h group: 26.25 and 1.75 micromol for more than 60 mins) did not reduce infarct volume 48 h after MCAO compared with saline-treated placebo groups after 6 or 2 h of MCAO. Stroke progression from baseline to 48 h, based on the apparent diffusion coefficient and relative cerebral blood flow deficits before and after reperfusion and T(2)-weighted hyperintensity at 48 h, did not differ between treated and control animals. These results suggest that nitrite is not a protective adjuvant therapy to delayed rtPA administration after ischemic stroke in rats.

Experimental models, neurovascular mechanisms and translational issues in stroke research

Numerous failures in clinical stroke trials have led to some pessimism in the field. This short review examines the following questions: Can experimental models of stroke be validated? How can combination stroke therapies be productively pursued? Can we achieve neuroprotection without reperfusion? And finally, can we move from a pure neurobiology view of stroke towards a more integrative approach targeting all cell types within the entire neurovascular unit? Emerging data from both experimental models and clinical findings suggest that neurovascular mechanisms may provide new opportunities for treating stroke. Ultimately, both bench-to-bedside and bedside-back-to-bench interactions may be required to overcome the translational hurdles for this challenging disease.

Hyperacute treatment initiation in neuroprotective agent stroke trials

BACKGROUND

Late treatment start may be an important cause for the repeated failure of neuroprotective agents in acute ischemic stroke trials. Animal models suggest the optimal therapeutic window for neuroprotective intervention is the first 1 to 3 hours after ischemia onset. No prior study has analyzed the frequency of treatment initiation within the first 1, 2, and 3 hours in human neuroprotective stroke clinical trials.

METHODS

A total of 30 phase 3 neuroprotective trials published in English between 1990 and 2001 were identified by systematic literature review. A 1-page, 4-field data questionnaire was mailed to the principal investigators of identified trials, asking them to specify the number of patients enrolled in their trial or trials within the following epochs: 0 to 60, 61 to 120, 121 to 180, and 181 to 360 minutes.

RESULTS

A total of 6 trials, enrolling 5345 patients, provided detailed data. In all, 4 trials, enrolling 4166 patients, used a maximum permitted time enrollment window of less than 6 hours, whereas two trials allowed enrollment beyond 6 hours. Across all trials, the number and proportion of patients enrolled in early time epochs were: 0 to 60 minutes, 10 (0.2%); 61 to 120 minutes, 66 (1.2%); 121 to 180 minutes, 340 (6.3%); and 181 to 360 minutes, 3723 (69.7%). Even in trials with less than 6-hour time windows, fewer than 2% of patients received study agent within 2 hours of onset.

CONCLUSIONS

Only a very small proportion of patients in recent neuroprotective acute stroke trials have been enrolled in hyperacute, under 3-hour time epochs, when treatment effect is likely to be most substantial. New treatment delivery and trial design strategies are suggested that could accelerate agent initiation in neuroprotective treatment trials.

Novel end point analytic techniques and interpreting shifts across the entire range of outcome scales in acute stroke trials

BACKGROUND AND PURPOSE

Stroke treatments are generally not curative, but rather alter patient outcome over the entire range of functional measures. Dichotomizing outcome scales reduces computational complexity, but discards substantial outcome information, artificially privileges only a single health state transition as clinically meaningful, and often reduces study power. Newer approaches to endpoint analysis have several advantageous properties. Summary of Review- The global statistic assesses treatment effects on multiple outcome measures simultaneously. However, translating the global statistic multidimensional vector effect at the population level into benefit or harm expected in the individual patient is problematic. Responder analysis adjusts outcome thresholds to patient stroke severity at study entry, identifying achievable goals for each patient. However, responder analysis still discards substantial outcome information. Shift analysis gauges change in outcome distributions over the full range of ascertained outcomes, incorporating benefit and harm at all health state transitions valued by patients and clinicians, and often increasing study power. Translation of findings of shift analyses into clinically accessible terms may be accomplished using the recently developed joint outcome table specification technique, which yields the following values for the number needed to treat for 1 patient to improve in a clinically important manner: nimodipine in subarachnoid hemorrhage, 6.8; coiling over clipping, 5.9; intra-arterial pro-urokinase in acute cerebral ischemia, 4.8; intravenous tissue plasminogen activator, 3.3.

CONCLUSIONS

Dichotomized, global statistic, responder, and shift analyses each offer distinctive benefits and drawbacks. Choice of primary end point analytic technique should be tailored to the study population, expected treatment response, and study purpose. Shift analysis generally provides the most comprehensive index of a treatment's clinical impact.

Life After Cerovive

The SAINT II Trial, a large randomized multicenter clinical trial of the putative neuroprotectant, NXY-059, failed to demonstrate a treatment benefit in acute ischemic stroke. The further development of this agent was suspended. The implications of this outcome are considered from several perspectives, including: (1) the marginally positive antecedent trial, SAINT I, and the critical commentary stimulated by it, which called attention to its interpretively challenging primary outcome measure—a shift in the full-scale modified Rankin scale score—and to other statistical shortcomings; (2) the cogency of the STAIR recommendations, to which the development of NXY-059 closely adhered; and (3) the inherent physiochemical shortcomings of NXY-059 as a neuroprotective agent—its polar, nonlipophilic nature, poor blood–brain barrier penetrability, nonphysiological oxidation potential, and low potency. Caution is urged, however, regarding the unwarranted adoption of a nihilistic view toward neuroprotection on the part of the stroke community in view of the abundant preclinical evidence demonstrating proof-of-principle of the feasibility of neuroprotection, as well as the multiplicity of biochemical and molecular neuroprotective targets. The author offers the personal example of a translational journey in which a promising neuroprotectant agent targeting multiple injury mechanisms, high-dose albumin therapy, has proceeded successfully from preclinical studies that established efficacy through a pilot clinical trial that demonstrated safety and offered strong suggestions of clinical efficacy, leading to a large multicenter clinical trial currently in progress.

Sex differences in brain damage and recovery of function: experimental and clinical findings

Until the last decade or so, there was very little systematic examination of sex differences in recovery from brain injury--most of the work was anecdotal or based on very small studies comparing males to females. This chapter reviews some of the physiological, morphological, and functional evidence for sex differences in response to brain injury across the spectrum of development. It also examines more recent data showing that fluctuations in hormonal status during the menstrual and estrous cycle can play a determining role in functional outcome in both normal and brain-injured females, and that these hormonal influences can be measured at both the cellular and behavioral levels.

Bench to bedside: the quest for quality in experimental stroke research

Over the past decades, great progress has been made in clinical as well as experimental stroke research. Disappointingly, however, hundreds of clinical trials testing neuroprotective agents have failed despite efficacy in experimental models. Recently, several systematic reviews have exposed a number of important deficits in the quality of preclinical stroke research. Many of the issues raised in these reviews are not specific to experimental stroke research, but apply to studies of animal models of disease in general. It is the aim of this article to review some quality-related sources of bias with a particular focus on experimental stroke research. Weaknesses discussed include, among others, low statistical power and hence reproducibility, defects in statistical analysis, lack of blinding and randomization, lack of quality-control mechanisms, deficiencies in reporting, and negative publication bias. Although quantitative evidence for quality problems at present is restricted to preclinical stroke research, to spur discussion and in the hope that they will be exposed to meta-analysis in the near future, I have also included some quality-related sources of bias, which have not been systematically studied. Importantly, these may be also relevant to mechanism-driven basic stroke research. I propose that by a number of rather simple measures reproducibility of experimental results, as well as the step from bench to bedside in stroke research may be made more successful. However, the ultimate proof for this has to await successful phase III stroke trials, which were built on basic research conforming to the criteria as put forward in this article.

[Role of gene therapy in trauma and orthopedic surgery]

Mit Hilfe molekularbiologischer und gentechnologischer Methoden kann durch den Transfer von spezifischen Genen das Erbgut einer Zelle verändert werden. Hierdurch werden die Zellfunktionen so moduliert, dass die Zelle, die durch das implantierte Gen verschlüsselte Funktionen erhält, Proteine synthetisiert, die sie normalerweise nicht oder nur in geringen Mengen produziert.

Wie erste tierexperimentelle Studien zeigen, kann die Gentherapie die Heilungs- und Regenerationsfähigkeit der Haut, von Sehnen, Knorpel und Knochen unterstützen und beschleunigen. In jüngster Zeit werden in Tierversuchen neue Vektoren mit einer geringeren Immunogenität und verbesserten Steuerbarkeit sowie einer erhöhten Transfersicherheit getestet. Es ist zu erwarten, dass die Gentherapie in den nächsten Jahrzehnten bei der Frakturheilung, der Sanierung von Knorpelschäden und für die Behandlung von Infektionen einen bedeutenden Stellenwert einnehmen wird.

Gauging recovery after hemorrhagic stroke in rats: implications for cytoprotection studies

Successful clinical translation of prospective cytoprotectants will likely occur only with treatments that improve functional recovery in preclinical (rodent) studies. Despite this assumption, many rely solely on histopathologic end points or the use of one or two simple behavioral tests. Presently, we used a battery of tests to gauge recovery after a unilateral intracerebral hemorrhagic stroke (ICH) targeting the striatum. In total, 60 rats (N=15 per group) were stereotaxically infused with 0 (SHAM), 0.06 (MILD lesion), 0.12 (MODERATE lesion), or 0.18 U (SEVERE lesion) of bacterial collagenase. This created a range of injury akin to moderate (from SEVERE to MODERATE or MODERATE to MILD lesion size approximately 30% reduction) and substantial cytoprotection (SEVERE to MILD lesion size--51% reduction). Post-ICH functional testing occurred over 30 days. Tests included the horizontal ladder and elevated beam tests, swimming, limb-use asymmetry (cylinder) test, a Neurologic Deficit Scale, an adhesive tape removal test of sensory neglect, and the staircase and single pellet tests of skilled reaching. Most tests detected significant impairments (versus SHAM), but only a few (e.g., staircase) frequently distinguished among ICH groups and none consistently differentiated among all ICH groups. However, by using a battery of tests we could behaviorally distinguish groups. Thus, preclinical testing would benefit from using a battery of behavioral tests as anything less may miss treatment effects. Such testing must be based on factors including the type of lesion, the postoperative delay and the time required to complete testing.

Minocycline for short-term neuroprotection

Minocycline is a widely used tetracycline antibiotic. For decades, it has been used to treat various gram-positive and gram-negative infections. Minocycline was recently shown to have neuroprotective properties in animal models of acute neurologic injury. As a neuroprotective agent, the drug appears more effective than other treatment options. In addition to its high penetration of the blood-brain barrier, minocycline is a safe compound commonly used to treat chronic infections. Its several mechanisms of action in neuroprotection -- antiinflammatory and antiapoptotic effects, and protease inhibition -- make it a desirable candidate as therapy for acute neurologic injury, such as ischemic stroke. Minocycline is ready for clinical trials of acute neurologic injury.

Xenon CT cerebral blood flow in acute stroke

Acute stroke therapy is evolving rapidly as research moves toward extending the time window for treatment so that more patients can benefit. As physiology-based imaging increasingly is used in patient selection, it is becoming evident that rigid time windows are not applicable to individual patients. Xenon CT has an important role in acute stroke therapeutic intervention as a quantitative, reproducible, rapid, and safe modality, which can provide valuable physiologic data that can optimize patient triage and aid in management.

Applying a phase II futility study design to therapeutic stroke trials

BACKGROUND AND PURPOSE

Most large, randomized phase III efficacy trials of therapeutic agents in ischemic stroke have failed to find treatment benefit. We determined whether some phase III studies could have been avoided if preceded by smaller single-arm phase II studies to evaluate the futility of proceeding to phase III.

METHODS

To provide examples of the application of phase II methodology, we obtained primary outcome data for the active treatment group of 6 phase III ischemic stroke therapy trials. For each study, we estimated the sample size number required for a multistage single-arm study using parameters specified in the original study. We evaluated outcome data for the first number of subjects in the phase III study treatment arm ordered by enrollment dates. We compared the proportion of favorable outcomes to prespecified stopping criteria derived from a single-arm phase II futility design. If the observed proportion of favorable outcomes was less than the stopping criterion, we declared the treatment not sufficiently effective to warrant further evaluation in phase III.

RESULTS

We identified 3 trials as futile in phase II; none of 3 showed treatment efficacy in phase III. In the 3 remaining phase II trials in which we did not show futility, one showed efficacy in phase III.

CONCLUSIONS

Single-arm phase II futility studies have been underused in stroke research, but provide a strategy for discarding treatments likely to be ineffective in phase III trials.

The mitochondrial uncoupler 2,4-dinitrophenol attenuates tissue damage and improves mitochondrial homeostasis following transient focal cerebral ischemia

Ischemic stroke is caused by acute neuronal degeneration provoked by interruption of cerebral blood flow. Although the mechanisms contributing to ischemic neuronal degeneration are myriad, mitochondrial dysfunction is now recognized as a pivotal event that can lead to either necrotic or apoptotic neuronal death. Lack of suitable 'upstream' targets to prevent loss of mitochondrial homeostasis has, so far, restricted the development of mechanistically based interventions to promote neuronal survival. Here, we show that the uncoupling agent 2,4 dinitrophenol (DNP) reduces infarct volume approximately 40% in a model of focal ischemia-reperfusion injury in the rat brain. The mechanism of protection involves an early decrease in mitochondrial reactive oxygen species formation and calcium uptake leading to improved mitochondrial function and a reduction in the release of cytochrome c into the cytoplasm. The observed effects of DNP were not associated with enhanced cerebral perfusion. These findings indicate that compounds with uncoupling properties may confer neuroprotection through a mechanism involving stabilization of mitochondrial function.

Possible involvement of group I mGluRs in neuroprotective effect of theanine

We investigated the molecular mechanism underlying the neuroprotective effect of theanine, a green tea component, using primary cultured rat cortical neurons, focusing on group I metabotropic glutamate receptors (mGluRs). Theanine and a group I mGluR agonist, DHPG, inhibited the delayed death of neurons caused by brief exposure to glutamate, and this effect of theanine was abolished by group I mGluR antagonists. Although the administration of glutamate alone decreased the neuronal expression of phospholipase C (PLC)-beta1 and -gamma1, which are linked to group I mGluRs, their expression was equal to the control levels on cotreatment with theanine. Treatment with theanine or DHPG alone for 5-7 days resulted in increased expression of PLC-beta1 and -gamma1, and the action of theanine was completely abolished by group I mGluR antagonists. These findings indicate that group I mGluRs might be involved in neuroprotective effect of theanine by increasing the expression levels of PLC-beta1 and -gamma1.

Drug targets in the voltage-gated calcium channel family: why some are and some are not

The L-type calcium channel antagonists have been, and continue to be, a very successful group of therapeutic agents targeted at cardiovascular disorders, notably angina and hypertension. The discovery that the voltage-gated calcium channels are a large and widely distributed family with important roles in both the peripheral and central nervous systems has initiated a major search for drugs active at other calcium channel types directed at disorders of the central nervous system, including pain, epilepsy, and stroke. These efforts have not been therapeutically successful thus far, and small molecule equivalents of the L-type blockers nifedipine, diltiazem, and verapamil directed at non-L-type channels have not been found. The underlying reasons for this are discussed together with suggestions for new directions, including fertility control, oxygen-sensitive channels, and calcium channel activators.

Critical Care Assessment and Management of Acute Ischemic Stroke

The resuscitation and treatment of patients with an acute stroke has evolved measurably during the past 2 decades. Acute ischemic stroke represents a true emergency where time is crucial and, therefore, evaluation and treatment often proceed simultaneously. Advanced imaging techniques can provide information about the state of brain perfusion, metabolism, and the cerebrovascular anatomy to help identify patients with viable brain tissue who may derive the greatest benefit from available therapies. Currently, several agents are available for rapid restoration of perfusion to ischemic brain. These include intravenous administration of recombinant tissue-type plasminogen activator (tPA), which is effective within a 3-hour period, and intraarterial thrombolytic therapy, which may be effective within 6 hours. In addition, newer agents such as ancrod and abciximab may be effective within the acute time period. Optimal care requires a multidisciplinary approach with attention to a wide variety of therapeutic issues while maintaining adequate brain perfusion to reverse or halt the ischemic process. Herein, the author examines the important therapeutic concerns in the critical care management of ischemic stroke, including the management of elevated intracranial pressure, elevated and low blood pressure, cardiac complications, and potential metabolic disturbances.

Management of Ischemic Stroke in the Next Decade: Stroke Centers of Excellence

Stroke has been increasingly recognized as an important and expensive medical and societal problem during the past 10 years. Currently, organized stroke care is delivered to the American population in only a few cities and hospitals that provide an efficient system for rapid transportation, diagnosis, treatment, and rehabilitation. The Brain Attack Coalition (BAC) has recently proposed the concepts of stroke centers of excellence (akin to trauma level I centers), primary stroke centers, and comprehensive stroke center. The U.S. government, with the Paul Coverdell National Acute Stroke Registry and the Stroke Treatment and Ongoing Prevention Act of 2003, further supports these concepts. Herein, a discussion of the influence that the BAC, the Paul Coverdell National Acute Stroke Registry, and the Stroke Treatment and Ongoing Prevention Acts of 2001 and 2003 will have on the future of stroke therapy in this country during the next 10 years is presented. Also discussed are the elements that are crucial to organized stroke care and the formation of stroke centers of excellence. These include triage and diagnosis in the field, transportation, triage and imaging in the emergency department, prompt transfer to a dedicated stroke unit with focused care, rehabilitation, manpower, prevention and research, reimbursement issues, and politics. The importance of multidisciplinary collaboration on the professional and societal levels and, finally, government- and private sector-sponsored research are also presented.

Recovery of Pelvic Limb Function in Dogs following Acute Intervertebral Disc Herniations

Chondrodystrophoid breeds of dog are prone to explosive herniation of mineralized disc material into the thoracolumbar spinal canal. The resulting acute spinal cord injury may represent an excellent spontaneous model of acute traumatic spinal cord injury. The aims of this study were to quantify the recovery of dogs following acute disc herniations, to evaluate external factors that influence recovery, and to identify a group of dogs suitable for use in clinical trials on neuroprotective drugs. The gait of 88 dogs with thoracolumbar disc herniations was scored at the time of injury and 2, 4, and 12 weeks after surgical decompression. Dogs were placed into four groups dependent on the severity of presenting signs; dogs in group 1 had the most severe injury severity. Group 1 dogs showed a variable but incomplete recovery by 12 weeks. Dogs in groups 2 and 3 recovered uniformly but more completely, while dogs in group 4 made a rapid and excellent recovery and were deemed unsuitable for clinical trials. Combining dogs in groups 1, 2 and 3 produced a population of dogs with incomplete recovery by 12 weeks. Power analysis revealed that 87 such dogs would be needed per treatment group to detect a 20% change in function with a power of 95%. The number needed reduced drastically to 19 by eliminating dogs in group 1, but this produced less room for functional improvement. External factors did not appear to influence outcome. We conclude that dogs with spontaneous disc herniations provide a useful model of acute spinal cord injury for clinical trials.