REPRINT: Good Laboratory Practice: Preventing Introduction of Bias at the Bench

As a research community, we have failed to demonstrate that drugs that show substantial efficacy in animal models of cerebral ischemia can also improve outcome in human stroke. Accumulating evidence suggests that this may be due, at least in part, to problems in the design, conduct and reporting of animal experiments, which create a systematic bias resulting in the overstatement of neuroprotective efficacy. Here, we set out a series of measures to reduce bias in the design, conduct and reporting of animal experiments modeling human stroke.

Reprint: Good laboratory practice: preventing introduction of bias at the bench

As a research community, we have failed to show that drugs, which show substantial efficacy in animal models of cerebral ischemia, can also improve outcome in human stroke. Accumulating evidence suggests this may be due, at least in part, to problems in the design, conduct, and reporting of animal experiments which create a systematic bias resulting in the overstatement of neuroprotective efficacy. Here, we set out a series of measures to reduce bias in the design, conduct and reporting of animal experiments modeling human stroke.

Effect of hyperthermia and anoxia on glucocorticoid and mineralocorticoid receptor expression in neonatal rat hippocampus

Brief periods of neonatal asphyxia are frequently observed. Within the CNS, the hippocampus is known to be particularly vulnerable to the damaging effects of hypoxia/ischaemia. The hippocampus contains the highest concentration of both mineralocorticoid (MR) and glucocorticoid (GR) receptors and the balance between MR/GR activation influences cell birth and death. MR occupation appears to promote prosurvival actions, while GR overactivation favours neurodegeneration. It has been widely recognized that core body temperature is a critical determinant of the severity of hypoxic-ischemic brain injury; indeed, hyperthermia exacerbates the degree of damage. Therefore, the aim of the present investigation was to study the effect of elevated body temperature in newborn rats under control conditions or during neonatal exposure to a critical anoxia, on changes of MR and GR mRNA expression in the rat hippocampus. 2-day-old rats were exposed to anoxia in 100% nitrogen atmosphere. Rectal temperature was kept at 33 degrees C (typical for the rat neonates), or elevated to a level typical for febrile (39 degrees C) adults. Control rats were exposed to atmospheric air under the respective thermal conditions. The changes in MR and GR mRNA expression in hippocampus were examined 24h after exposure. Our data show that hyperthermia with or without added anoxia, causes induction of MR mRNA expression in neonatal rat hippocampus without any effect on GR mRNA expression. We suggest this elevation of MR plays an important role in modulating the survival of neurons in the injured hippocampus.

Aortic arch atheroma

Severe atheroma of the aortic arch has now been established as an important risk factor and mechanism for stroke and peripheral embolism. The odds ratio for stroke or peripheral embolism in patients with severe arch atheroma is greater than four, and for mobile atheroma it is greater than 12. The prevalence of severe arch atheroma among patients presenting with acute ischaemic stroke, at over 20%, is in the same order as that of atrial fibrillation and carotid atherosclerosis. In patients with ischaemic stroke for which no cause has been identified, it is reasonable to determine as to whether they have severe arch atheroma by performing a transoesophageal echocardiogram. Recurrent stroke is common in patients with aortic arch atheroma that are thicker than 4 mm or with mobile components, particularly in the elderly, cigarette smokers, and those with hypertension or diabetes. Patients found to have severe atheroma are at high risk of recurrent events (14.2% per year) and may, therefore, need an aggressive secondary prevention strategy. Currently, there is uncertainty as to what this should be, but either combination antiplatelet therapy (aspirin plus clopidogrel) or anticoagulation with warfarin (target INR 2.0-3.0) are commonly used. Which of these is most effective will be evident after the completion of the aortic arch related cerebral hazard trial.

Good laboratory practice: preventing introduction of bias at the bench

BACKGROUND AND PURPOSE

As a research community, we have failed to demonstrate that drugs which show substantial efficacy in animal models of cerebral ischemia can also improve outcome in human stroke. Summary of Review- Accumulating evidence suggests this may be due, at least in part, to problems in the design, conduct and reporting of animal experiments which create a systematic bias resulting in the overstatement of neuroprotective efficacy.

CONCLUSIONS

Here, we set out a series of measures to reduce bias in the design, conduct and reporting of animal experiments modeling human stroke.

Evidence for the efficacy of NXY-059 in experimental focal cerebral ischaemia is confounded by study quality

BACKGROUND AND PURPOSE

The neutral results of the SAINT II trial have again highlighted difficulties translating neuroprotective efficacy from bench to bedside. Animal studies are susceptible to study quality biases, which may lead to overstatement of efficacy. We report the impact of study quality on published estimates of the efficacy of NXY-059 in animal models of stroke.

METHODS

We conducted a systematic review and stratified meta-analysis of published studies describing the efficacy of NXY-059 in experimental focal cerebral ischemia.

RESULTS

Overall, NXY-059 improved infarct volume by 43.3% (95% CI, 34.7 to 52.8). Only 2 of 9 publications reported randomization, concealment of treatment allocation, and blinded outcome assessment. Studies not reporting these quality items gave substantially higher estimates of efficacy than did higher-quality studies.

CONCLUSIONS

The reported efficacy of NXY-059 in animal models of stroke is confounded by low study quality. The failure of SAINT II highlights the need for substantial improvements in the design, conduct, and reporting of animal studies; journals can play an important role in this by adopting standards for animal studies similar to those agreed over 10 years ago for clinical trials.

Hypothermia in animal models of acute ischaemic stroke: a systematic review and meta-analysis

Induced hypothermia is proposed as a treatment for acute ischaemic stroke, but there have been too few clinical trials involving too few patients to draw any conclusions about the therapeutic benefit of cooling. Animal studies of induced hypothermia in focal cerebral ischaemia have tested cooling throughout a wide range of target temperatures, durations and intervals between stroke onset and the initiation of hypothermia. These studies, therefore, provide an opportunity to evaluate the effectiveness of different treatment strategies in animal models to inform the design of future clinical trials. We performed a systematic review and meta-analysis of the evidence for efficacy of hypothermia in animal models of ischaemic stroke, and identified 101 publications reporting the effect of hypothermia on infarct size or functional outcome, including data from a total of 3353 animals. Overall, hypothermia reduced infarct size by 44% [95% confidence interval (CI), 40-47%]. Efficacy was highest with cooling to lower temperatures (< or =31 degrees C), where treatment was started before or at the onset of ischaemia and in temporary rather than permanent ischaemia models. However, a substantial reduction in infarct volume was also observed with cooling to 35 degrees C (30%; 95% CI, 21-39%), with initiation of treatment between 90 and 180 min (37%; 95% CI, 28-46%) and in permanent ischaemia models (37%; 95% CI, 30-43%). The effects of hypothermia on functional outcome were broadly similar. We conclude that in animal models of focal cerebral ischaemia, hypothermia improves outcome by about one-third under conditions that may be achievable for large numbers of patients with ischaemic stroke. Large randomized clinical trials testing the effect of hypothermia in patients with acute ischaemic stroke are warranted.

Forebrain mineralocorticoid receptor overexpression enhances memory, reduces anxiety and attenuates neuronal loss in cerebral ischaemia

The nuclear mineralocorticoid receptor (MR), a high-affinity receptor for glucocorticoids, is highly expressed in the hippocampus where it underpins cognitive, behavioural and neuroendocrine regulation. Increased neuronal MR expression occurs early in the response to cellular injury in vivo and in vitro and is associated with enhanced neuronal survival. To determine whether increased neuronal MR might be causal in protecting against ischaemic damage in vivo we generated a forebrain-specific MR-overexpressing transgenic mouse (MR-Tg) under the control of the CamKII alpha promoter, and subjected mice to transient cerebral global ischaemia induced by bilateral common carotid artery occlusion for 20 min. We also separately assessed the effects of MR overexpression on hypothalamic-pituitary-adrenal (HPA) axis activity and cognitive and affective functions in noninjured animals. Our results showed that MR-Tg mice had significantly reduced neuronal death following transient cerebral global ischaemia compared to wild-type littermates. This effect was not associated with alterations in basal or poststress HPA axis function or in arterial blood pressure. MR-Tg mice also demonstrated improved spatial memory retention, reduced anxiety and altered behavioural response to novelty. The induction of neuronal MR appears to offer a protective response which has potential therapeutic implications in cerebral ischaemia and cognitive and affective disorders.

Hemicraniectomy after middle cerebral artery infarction with life-threatening Edema trial (HAMLET). Protocol for a randomised controlled trial of decompressive surgery in space-occupying hemispheric infarction

Background

Patients with a hemispheric infarct and massive space-occupying brain oedema have a poor prognosis. Despite maximal conservative treatment, the case fatality rate may be as high as 80%, and most survivors are left severely disabled. Non-randomised studies suggest that decompressive surgery reduces mortality substantially and improves functional outcome of survivors. This study is designed to compare the efficacy of decompressive surgery to improve functional outcome with that of conservative treatment in patients with space-occupying supratentorial infarction

Methods

The study design is that of a multi-centre, randomised clinical trial, which will include 112 patients aged between 18 and 60 years with a large hemispheric infarct with space-occupying oedema that leads to a decrease in consciousness. Patients will be randomised to receive either decompressive surgery in combination with medical treatment or best medical treatment alone. Randomisation will be stratified for the intended mode of conservative treatment (intensive care or stroke unit care). The primary outcome measure will be functional outcome, as determined by the score on the modified Rankin Scale, at one year.

1,026 experimental treatments in acute stroke

OBJECTIVE

Preclinical evaluation of neuroprotectants fostered high expectations of clinical efficacy. When not matched, the question arises whether experiments are poor indicators of clinical outcome or whether the best drugs were not taken forward to clinical trial. Therefore, we endeavored to contrast experimental efficacy and scope of testing of drugs used clinically and those tested only experimentally.

METHODS

We identified neuroprotectants and reports of experimental efficacy via a systematic search. Controlled in vivo and in vitro experiments using functional or histological end points were selected for analysis. Relationships between outcome, drug mechanism, scope of testing, and clinical trial status were assessed statistically.

RESULTS

There was no evidence that drugs used clinically (114 drugs) were more effective experimentally than those tested only in animal models (912 drugs), for example, improvement in focal models averaged 31.3 +/- 16.7% versus 24.4 +/- 32.9%, p > 0.05, respectively. Scope of testing using Stroke Therapy Academic Industry Roundtable (STAIR) criteria was highly variable, and no relationship was found between mechanism and efficacy.

INTERPRETATION

The results question whether the most efficacious drugs are being selected for stroke clinical trials. This may partially explain the slow progress in developing treatments. Greater rigor in the conduct, reporting, and analysis of animal data will improve the transition of scientific advances from bench to bedside.

Greater Incidence of Both Fatal and Nonfatal Strokes in Disadvantaged Areas

BACKGROUND AND PURPOSE

Greater stroke mortality has been reported among lower socioeconomic groups. We aimed to determine whether fatal, nonfatal, and overall stroke incidence varied by socioeconomic status.

METHODS

All suspected strokes occurring in 22 postcodes (population of 306,631) of Melbourne, Australia, during a 24-month period between 1997 and 1999 were found and assessed. Multiple overlapping sources were used to ascertain cases with standard clinical definitions for stroke. Socioeconomic disadvantage was assigned in 4 bands from least to greatest using an area-based measure developed by the Australian Bureau of Statistics.

RESULTS

Overall stroke incidence (number per 100,000 population per year), adjusted to the European population 45 to 84 years of age, increased with increasing socioeconomic disadvantage: 200 (95% CI, 173 to 228); 251 (95% CI, 220 to 282); 309 (95% CI, 274 to 343); and 366 (95% CI, 329 to 403; chi2 for ranks; P<0.0001). Similar incidence patterns were observed for both fatal and nonfatal stroke. Nonfatal stroke contributed most to this incidence pattern: 146 (95% CI, 122 to 169); 181 (95% CI, 155 to 207); 223 (95% CI, 194 to 252); and 280 (95% CI, 247 to 313; chi2 for ranks; P<0.0001).

CONCLUSIONS

In this population-based study, both fatal and nonfatal stroke incidence increased with increasing socioeconomic disadvantage. The greater contributor to this incidence pattern was nonfatal stroke incidence. This may have implications for service provision to those least able to afford it. Area-based identification of those most disadvantaged may provide a simple and effective way of targeting regions for stroke prevention strategies.

Results of a Multicentre, Randomised Controlled Trial of Intra-Arterial Urokinase in the Treatment of Acute Posterior Circulation Ischaemic Stroke

BACKGROUND

Patients with ischaemic stroke due to occlusion of the basilar or vertebral arteries may develop a rapid deterioration in neurological status leading to coma and often to death. While intra-arterial thrombolysis may be used in this context, no randomised controlled data exist to support its safety or efficacy.

METHODS

Randomised controlled trial of intra-arterial urokinase within 24 h of symptom onset in patients with stroke and angiographic evidence of posterior circulation vascular occlusion.

RESULTS

Sixteen patients were randomised, and there was some imbalance between groups, with more severe strokes occurring in the treatment arm. A good outcome was observed in 4 of 8 patients who received intra-arterial urokinase compared with 1 of 8 patients in the control group.

CONCLUSIONS

These results support the need for a large-scale study to establish the efficacy of intra-arterial thrombolysis for acute basilar artery occlusion.

Systematic review and metaanalysis of the efficacy of FK506 in experimental stroke

FK506 is a candidate drug for acute stroke. For such drugs, any decision to proceed to clinical trial should be based on a full and unbiased assessment of the animal data, and consideration should be given to the limitations of those data. Such an assessment should include not only the efficacy of a drug but also the in vivo characteristics and limits to that efficacy. Here we use systematic review and meta-analysis to assess the evidence for a protective effect of FK506 in animal models of stroke. In all, 29 studies were identified describing procedures involving 1759 animals. The point estimate for the effect of FK506 was a 31.3% (95% confidence interval 27.2% to 35.4%) improvement in outcome. Efficacy was higher with ketamine anaesthesia and temporary ischaemia and was lower in rats, in animals with comorbidities, and where outcome was measured as infarct size alone. Reported study quality was modest by clinical trial standards, and efficacy was lower in high-quality studies. These findings show a substantial efficacy for FK506 in experimental stroke, but raise concerns that our estimate of effect size might be too high because of factors such as study quality and possible publication bias.

Systematic review and meta-analysis of the efficacy of melatonin in experimental stroke

Melatonin is a candidate neuroprotective drug for ischaemic stroke. Any decision to proceed to clinical trial for such drugs should be based on an unbiased assessment of all available data. Such an assessment should include not only the efficacy of a drug but also the in vivo characteristics and limits--in terms of time window, dose, species and model of ischaemia used--to that efficacy. Here we use a systematic approach to establish the limits to and characteristics of the neuroprotective efficacy of melatonin in experimental stroke. We have used systematic review and meta-analysis to assess the evidence for a protective effect of melatonin in animal models of focal cerebral ischaemia. Fourteen studies were identified describing procedures involving 432 animals. The point estimate for the effect of melatonin was a 42.8% (95% CI 39.3-46.3%) improvement in outcome. Efficacy was greater when ketamine anaesthesia was used, and melatonin was equally effective in permanent or temporary ischaemia. Study quality was generally poor by clinical trial standards, and no evidence was found regarding the efficacy of melatonin in focal cerebral ischaemia in aged, hypertensive or diabetic animals, in species other than rats, or at time windows beyond 2 hr. These findings demonstrate a marked efficacy of melatonin in animal models of focal cerebral ischaemia, identify priority areas for future animal research, and suggest melatonin as a candidate neuroprotective drug for human stroke.

Atheroma of the aortic arch: an important and poorly recognised factor in the aetiology of stroke

Atrial fibrillation and severe carotid-artery stenosis are well-characterised risk factors for stroke; each is present in about a fifth of patients. The identification of such risk factors in patients is important because their presence calls for specific secondary prevention strategies. One region of the circulation that has received limited attention as a source of thrombus is the aortic arch. However, aortic arch atheroma is a common post-mortem finding, and it seems reasonable to speculate that atheroma might give rise to thrombi with distal embolism to the arterial tree, including the cerebral circulation. Here we review the evidence for aortic-arch atheroma as an important independent risk factor for stroke, and show that studies of the risk of stroke indicate a four times greater odds of stroke in patients with severe arch atheroma.

Pooling of animal experimental data reveals influence of study design and publication bias

BACKGROUND AND PURPOSE

The extensive neuroprotective literature describing the efficacy of candidate drugs in focal ischemia has yet to lead to the development of effective stroke treatments. Ideally, the choice of drugs taken forward to clinical trial should be based on an unbiased assessment of all available data. Such an assessment might include not only the efficacy of a drug but also the in vivo characteristics and limits--in terms of time window, dose, species, and model of ischemia used--to that efficacy. To our knowledge, such assessments have not been made. Nicotinamide is a candidate neuroprotective drug with efficacy in experimental stroke, but the limits to and characteristics of that efficacy have not been fully described.

METHODS

Systematic review and modified meta-analysis of studies of experimental stroke describing the efficacy of nicotinamide. The search strategy ensured ascertainment of studies published in full and those published in abstract only. DerSimonian and Laird random effects meta-analysis was used to account for heterogeneity between studies.

RESULTS

Nicotinamide improved outcome by 0.287 (95% confidence interval 0.227 to 0.347); it was more effective in temporary ischemia models, after intravenous administration, in animals without comorbidities, and in studies published in full rather than in abstract. Studies scoring highly on a quality measure gave more precise estimates of the global effect.

CONCLUSIONS

Meta-analysis provides an effective technique for the aggregation of data from experimental stroke studies. We propose new standards for reporting such studies and a systematic approach to aggregating data from the neuroprotective literature.

Mineralocorticoid receptor expression and increased survival following neuronal injury

Glucocorticoids, acting via the mineralocorticoid receptor, are required for granule neuronal survival in the rat dentate gyrus. Whether this mineralocorticoid receptor-mediated neuroprotective effect has more general applicability is unknown. Here we report increased mineralocorticoid receptor expression in rat hippocampal and cortical neurons exposed in vitro to low levels of staurosporine and in rat hippocampal pyramidal neurons exposed in vivo to hypothermic transient global ischaemia. In both the cell culture system and the in vivo system increased mineralocorticoid receptor expression is associated with increased neuronal survival, and this increase is reversed by mineralocorticoid receptor antagonism. Modulation of mineralocorticoid receptor gene expression may therefore be an important target for reduction of brain injury in conditions caused by cerebral ischaemia including brain damage following cardiac arrest and stroke.

Reduced NMDA-induced apoptosis in neurons lacking ataxia telangiectasia mutated protein

Apoptosis is an important route to neuronal death in experimental models of stroke, the leading neurological cause of death and disability. Here we explore a role for ataxia telangiectasia mutated protein (ATM), an activator of p53, in a primary cortical culture model of stroke. NMDA-induced apoptosis was reduced in cultures derived from mice with targeted deletions in the ATM gene. In addition, NMDA-induced caspase-3 activity was abolished in cultures lacking two functioning copies of the ATM gene. These data provide evidence to suggest that, in primary cortical culture, NMDA-induced apoptosis is partially mediated through ATM. They provide further evidence to support the hypothesis that DNA damage is one route to apoptosis following neuronal injury.

Effect of deprivation and gender on the incidence and management of acute brain disorders

OBJECTIVE

To determine the impact of deprivation and gender on the incidence and emergency management of acute brain disorders.

DESIGN

Retrospective database review of mortality, hospital discharge, and ICU discharge data.

SETTING

Lothian Health Board area, 1995-1999.

PATIENTS AND PARTICIPANTS

All persons over the age of 15 dying or being discharged from hospital with a primary diagnosis of stroke, epilepsy, subarachnoid haemorrhage (SAH) or traumatic brain injury; patients registered in the Scottish Intensive Care Society Audit Database as having been discharged from the supraregional neurosciences intensive care unit with one of these as a primary diagnoses and a home postcode within the Lothian Health Board area.

MEASUREMENTS AND RESULTS

Standardised ratios were calculated for hospital admission, mortality, and ICU admission by deprivation category and gender. Data were available for 29,205 hospital admissions, 5,227 deaths, and 360 ICU admissions. For all diagnoses, deprivation was associated with higher rates of hospital admission and death. Deprivation was associated with lower rates of ICU admission for traumatic brain injury and stroke. There was a U-shaped relationship between deprivation and ICU admission with epilepsy. There were no gender differences in rates of ICU admission. Males had higher rates of hospital admission for all conditions and of death from epilepsy and SAH, and lower rates of death from stroke.

CONCLUSIONS

We have demonstrated deprivation- and gender- differences in the incidence and emergency management of four acute brain disorders. The identification of the source(s) of these differences is an important subject for further research.

Nitric-oxide-synthase-mediated cyclic guanosine monophosphate production in neonatal rat cerebellar prisms is resistant to calcineurin inhibition

Although the macrolide immunosuppressant tacrolimus (FK506) is neuroprotective in animal models of focal and global cerebral ischaemia, the mechanism of this action is not known. FK506 inhibits the protein phosphatase calcineurin, whose substrates can include nitric oxide synthase (NOS), and the neuroprotective effect of FK506 has been attributed to inhibition of NOS activity. We have examined nitric oxide-mediated cyclic guanosine monophosphate (cGMP) accumulation in neonatal rat cerebellar prisms. As expected, N-methyl-D-aspartate (NMDA) induced a rapid, concentration dependent accumulation of cGMP that was inhibited by the NMDA receptor antagonist dizocilpine (MK801) and the NOS inhibitor L-nitro-arginine methyl ester. Phosphoserine immunopositivity following NMDA exposure was increased in the presence of FK506, confirming inhibition of calcineurin. However, FK506 had no effect on NMDA-stimulated cGMP accumulation. These findings suggest that the neuroprotective effect of FK506 may be mediated by mechanisms other than increased NOS phosphorylation.

Serum withdrawal causes apoptosis in SHSY 5Y cells

A proportion of differentiated SH-SY5Y cells undergo cell death in response to withdrawal of serum. This death manifests the hallmark features of apoptosis including changes in nuclear morphology, processing and activation of caspase 3 and cleavage of the caspase 3 substrates acetyl-Asp-Glu-Val-Asp-aminomethylcoumarin and poly(ADP-ribose) polymerase. These findings represent the first demonstration of serum withdrawal induced apoptosis in SH-SY5Y cells. The reduction in viability induced by serum deprivation and assessed using an inhibitor of mitochondrial respiration can be partially inhibited by FK506, but FK506 does not prevent caspase 3 processing or cleavage of caspase 3 substrates. FK506 is also able to promote the viability of a small proportion of embryonic mouse sensory neurons following nerve growth factor-withdrawal induced apoptosis. FK506 did not promote viability in either cell type in the absence of serum- or nerve growth factor-withdrawal. These observations are consistent with a survival-promoting effect of FK506 in cultured neurons.