Neuroimaging as a Selection Tool and Endpoint in Clinical and Pre-clinical Trials

Efficacy of Cerebrolysin Treatment as an Add-On Therapy to Mechanical Thrombectomy in Patients With Acute Ischemic Stroke Due to Large Vessel Occlusion: Study Protocol for a Prospective, Open Label, Single-Center Study With 12 Months of Follow-Up

This study is designed to determine the efficacy of Cerebrolysin treatment as an add-on therapy to mechanical thrombectomy (MT) in reducing global disability in subjects with acute ischemic stroke (AIS). We have planned a single center, prospective, open-label, single-arm study with a 12-month follow-up of 50 patients with moderate to severe AIS, with a small established infarct core and with good collateral circulation who achieve significant reperfusion following MT and who receive additional Cerebrolysin within 8 h of stroke onset compared to 50 historical controls treated with MT alone, matched for age, clinical severity, occlusion location, baseline perfusion lesion volume, onset to reperfusion time, and use of iv thrombolytic therapy. The primary outcome measure will be the overall proportion of subjects receiving Cerebrolysin compared to the control group experiencing a favorable functional outcome (by modified Rankin Scale 0-2) at 90 days, following stroke onset. The secondary objectives are to determine the efficacy of Cerebrolysin as compared to the control group in reducing the risk of symptomatic secondary hemorrhagic transformation, improving neurological outcomes (NIHSS 0-2 at day 7, day 30, and 90), reducing mortality rates (over the 90-day and 12 months study period), and improving: activities of daily living (by Barthel Index), health-related quality of life (EQ-5D-5L) assessed at day 30, 90, and at 12 months. The other measures of efficacy in the Cerebrolysin group will include: assessment of final stroke volume and penumbral salvage (measured by CT/CTP at 30 days) and its change compared to baseline volume, changes over time in language function (by the 15-item Boston Naming Test), hemispatial neglect (by line bisection test), global cognitive function (by The Montreal Cognitive Assessment), and depression (by Hamilton Depression Rating Scale) between day 30 and day 90 assessments). The patients will receive 30 ml of Cerebrolysin within 8 h of AIS stroke onset and continue treatment once daily until day 21 (first cycle) and they will receive a second cycle of treatment (30 ml/d for 21 days given in the Outpatient Department or Neurorehabilitation Clinic) from day 69 to 90.

Biomonitoring and Digital Data Technology as an Opportunity for Enhancing Animal Study Translation

The failure of animal studies to translate to effective clinical therapeutics has driven efforts to identify underlying cause and develop solutions that improve the reproducibility and translatability of preclinical research. Common issues revolve around study design, analysis, and reporting as well as standardization between preclinical and clinical endpoints. To address these needs, recent advancements in digital technology, including biomonitoring of digital biomarkers, development of software systems and database technologies, as well as application of artificial intelligence to preclinical datasets can be used to increase the translational relevance of preclinical animal research. In this review, we will describe how a number of innovative digital technologies are being applied to overcome recurring challenges in study design, execution, and data sharing as well as improving scientific outcome measures. Examples of how these technologies are applied to specific therapeutic areas are provided. Digital technologies can enhance the quality of preclinical research and encourage scientific collaboration, thus accelerating the development of novel therapeutics.

A Review of Translational Magnetic Resonance Imaging in Human and Rodent Experimental Models of Small Vessel Disease

Cerebral small vessel disease (SVD) is a major health burden, yet the pathophysiology remains poorly understood with no effective treatment. Since much of SVD develops silently and insidiously, non-invasive neuroimaging such as MRI is fundamental to detecting and understanding SVD in humans. Several relevant SVD rodent models are established for which MRI can monitor in vivo changes over time prior to histological examination. Here, we critically review the MRI methods pertaining to salient rodent models and evaluate synergies with human SVD MRI methods. We found few relevant publications, but argue there is considerable scope for greater use of MRI in rodent models, and opportunities for harmonisation of the rodent-human methods to increase the translational potential of models to understand SVD in humans. We summarise current MR techniques used in SVD research, provide recommendations and examples and highlight practicalities for use of MRI SVD imaging protocols in pre-selected, relevant rodent models.

Establishment and Evaluation of a Monkey Acute Cerebral Ischemia Model

OBJECTIVES

Cerebral ischemia seriously threatens human health and is characterized by high rates of incidence, disability and death. Developing an ideal animal model of cerebral ischemia that reflects the human clinical features is critical for pathological studies and clinical research. The goal of this study is to establish a local cerebral ischemia model in rhesus macaque, thereby providing an optimal animal model to study cerebral ischemia.

METHODS

Eight healthy rhesus monkeys were selected for this study. CT scans were performed before the operation to exclude cerebral vascular and intracranial lesions. Under guidance and monitoring with digital subtraction angiography (DSA), a microcatheter was inserted into the M1 segment of the middle cerebral artery (MCA) via the femoral artery. Then, autologous white thrombi were introduced to block blood flow. Immediately following embolization, multisequence MRI was used to monitor cerebrovascular and brain parenchymal conditions. Twenty-four hours after embolization, 2 monkeys were sacrificed and subjected to perfusion, fixation and pathological examination.

RESULTS

The cerebral ischemia model was established in 7 rhesus monkeys; one animal died during intubation. DSA and magnetic resonance angiography (MRA) indicated the presence of an arterial occlusion. MRI showed acute local cerebral ischemia. HE staining revealed infarct lesions formed in the brain tissues, and thrombi were present in the cerebral artery.

CONCLUSION

We established a rhesus macaque model of local cerebral ischemia by autologous thrombus placement. This model has important implications for basic and clinical research on cerebral ischemia. MRI and DSA can evaluate the models to ensure accuracy and effectiveness.

The Association Between Recanalization, Collateral Flow, and Reperfusion in Acute Stroke Patients: A Dynamic Susceptibility Contrast MRI Study

Background: Collateral circulation in ischemic stroke patients plays an important role in infarct evolution und assessing patients' eligibility for endovascular treatment. By means of dynamic susceptibility contrast MRI, we aimed to investigate the effects of reperfusion, recanalization, and collateral flow on clinical and imaging outcomes after stroke. Methods: Retrospective analysis of 184 patients enrolled into the prospective observational 1000Plus study (clinicaltrials.org NCT00715533). Inclusion criteria were vessel occlusion on baseline MR-angiography, imaging within 24 h after stroke onset and follow-up perfusion imaging. Baseline Higashida score using subtracted dynamic MR perfusion source images was used to quantify collateral flow. The influence of these variables, and their interaction with vessel recanalization, on clinical and imaging outcomes was assessed using robust linear regression. Results: Ninety-eight patients (53.3%) showed vessel recanalization. Higashida score (p = 0.002), and recanalization (p = 0.0004) were independently associated with reperfusion. However, we found no evidence that the association between Higashida score and reperfusion relied on recanalization status (p = 0.2). NIHSS on admission (p < 0.0001) and recanalization (p = 0.001) were independently associated with long-term outcome at 3 months, however, Higashida score (p = 0.228) was not. Conclusion: Higashida score and recanalization were independently associated with reperfusion, but the association between recanalization and reperfusion was similar regardless of collateral flow quality. Recanalization was associated with long-term outcome. DSC-based measures of collateral flow were not associated with long-term outcome, possibly due to the complex dynamic nature of collateral recruitment, timing of imaging and the employed post-processing.

Stroke: The past, present and future

Since the inception of the British Neuroscience Association, there have been major advances in our knowledge of the mechanistic basis for stroke-induced brain damage. Identification of the ischaemic cascade led to the development of hundreds of new drugs, many showing efficacy in preclinical (animal-based) studies. None of these drugs has yet translated to a successful stroke treatment, current therapy being limited to thrombolysis/thrombectomy. However, this translational failure has led to significant improvements in the quality of animal-based stroke research, with the refinement of rodent models, introduction of new technologies (e.g. transgenics, in vivo brain imaging) and improvements in study design (e.g. STAIR, ARRIVE and IMPROVE guidelines). This has run in parallel with advances in clinical diagnostic imaging for detection of ischaemic versus haemorrhagic stroke, differentiating penumbra from ischaemic core, and improved clinical trial design. These preclinical and clinical advances represent the foundation for successful translation from the bench to the bedside in the near future.

Cerebral venous collaterals: A new fort for fighting ischemic stroke?

Stroke therapy has entered a new era highlighted by the use of endovascular therapy in addition to intravenous thrombolysis. However, the efficacy of current therapeutic regimens might be reduced by their associated adverse events. For example, over-reperfusion and futile recanalization may lead to large infarct, brain swelling, hemorrhagic complication and neurological deterioration. The traditional pathophysiological understanding on ischemic stroke can hardly address these occurrences. Accumulating evidence suggests that a functional cerebral venous drainage, the major blood reservoir and drainage system in brain, may be as critical as arterial infusion for stroke evolution and clinical sequelae. Further exploration of the multi-faceted function of cerebral venous system may add new implications for stroke outcome prediction and future therapeutic decision-making. In this review, we emphasize the anatomical and functional characteristics of the cerebral venous system and illustrate its necessity in facilitating the arterial infusion and maintaining the cerebral perfusion in the pathological stroke content. We then summarize the recent critical clinical studies that underscore the associations between cerebral venous collateral and outcome of ischemic stroke with advanced imaging techniques. A novel three-level venous system classification is proposed to demonstrate the distinct characteristics of venous collaterals in the setting of ischemic stroke. Finally, we discuss the current directions for assessment of cerebral venous collaterals and provide future challenges and opportunities for therapeutic strategies in the light of these new concepts.

Current Status and Future Perspective of Stenting for Symptomatic Intracranial Atherosclerotic Disease: A Meta-Analysis

The aim of this study was to evaluate the safety and effectiveness of percutaneous transluminal angioplasty and stenting (PTAS) for intracranial atherosclerotic disease (ICAD) by conducting a meta-analysis. Two independent observers searched PubMed, EMBASE, and Cochrane Library for relevant studies up to 31 December 2016. A meta-analysis was conducted using Review Manager 5.3. Three studies involving 581 cases were included. The meta-analysis indicated that any stroke (RR = 3.13; 95% CI: 1.80-5.42), ischemic stroke (RR = 2.15; 95% CI: 1.19-3.89), and intracranial hemorrhage (RR = 14.71; 95% CI: 1.96-110.48) within 30 days in medical therapy alone were lower compared with PTAS plus medical therapy, but there were no significant differences in any stroke and ischemic stroke beyond 30 days between the two groups. There were also no significant differences in any death and myocardial infarction between the two groups. This meta-analysis demonstrated that, compared with medical therapy alone, PTAS for ICAD had a high risk of complication, but most complications in PTAS group occurred within 30 days after the operation, and beyond 30 days the PTAS was not inferior compared with medical therapy alone. Further studies are needed to reduce the periprocedural complications and reappraise the PTAS.

Management of Spontaneous Subarachnoid Hemorrhage Patients with Negative Initial Digital Subtraction Angiogram Findings: Conservative or Aggressive?

Background. The ideal management of SAH patients with negative initial DSA findings remains unresolved. Objective. (i) To present risk factors, clinical courses, and outcomes in different types of SAH patients with negative DSA findings; (ii) to explore the differences of basal vein between aSAH patients and NASAH patients; and (iii) to evaluate the value of repeated DSA for these patients. Methods. All SAH patients with negative initial DSA findings between 2013 and 2015 in our hospital were enrolled and were further categorized as perimesencephalic SAH (PMN-SAH) or nonperimesencephalic SAH (nPMN-SAH). Risk factors, clinical courses, outcomes, and the basal vein drainage patterns were compared. Results. A total of 137 patients were enrolled in the present study. The PMN-SAH group had better GOS and mRS values at 1-year follow-up. Moreover, the nPMN-SAH group had a higher rate of complications. The basal vein drainage pattern showed significant difference when comparing each of the NASAH subtypes with aSAH groups. There was a significant higher rate of a responsible aneurysm in nPMN-SAH group upon repeated DSA. Conclusions. SAH patients with negative initial DSA findings had benign clinical courses and outcomes. Repeated DSA studies are strongly advised for patients with the nPMN-SAH pattern.

Cytoprotective Drug-Tissue Plasminogen Activator Protease Interaction Assays: Screening of Two Novel Cytoprotective Chromones

Tissue plasminogen activator (tPA) is currently used in combination with endovascular procedures to enhance recanalization and cerebral reperfusion and is also currently administered as standard-of-care thrombolytic therapy to patients within 3-4.5 h of an ischemic stroke. Since tPA is not neuroprotective or cytoprotective, adjuvant therapy with a neuroprotective or an optimized cytoprotective compound is required to provide the best care to stroke victims to maximally promote clinical recovery. In this article, we describe the use of a sensitive standardized protease assay with CH3SO2-D-hexahydrotyrosine-Gly-Arg-p-nitroanilide•AcOH, a chromogenic protease substrate that is cleaved to 4-nitroaniline (p-nitroaniline) and measured spectrophotometrically at 405 nm (OD405 nm), and how the assay can be used as an effective screening assay to study drug-tPA interactions. While we focus on two compounds of interest in our drug development pipeline, the assay is broadly applicable to all small molecule neuroprotective or cytoprotective compounds currently being discovered and developed worldwide. In this present study, we found that the specific tPA inhibitor, plasminogen activator inhibitor-1 (PAI-1; 0.25 μM), significantly (p < 0.0001) inhibited 4-nitroaniline release, by 97.74% during the 10-min duration of the assay, which is indicative of tPA protease inhibition. In addition, two lead chromone cytoprotective candidates, 2-(3',4',5'-trihydroxyphenyl)chromen-4-one (3',4',5'-trihydroxyflavone) (CSMC-19) and 3-hydroxy-2-[3-hydroxy-4-(pyrrolidin-1-yl)phenyl]benzo[h]chromen-4-one (CSMC-140), also significantly (p < 0.05) reduced 4-nitroaniline accumulation, but to a lesser extent. The reduction was 68 and 45%, respectively, at 10 μM, and extrapolated IC50 values were 4.37 and >10 μM for CSMC-19 and CSMC-140, respectively. Using bonafide 4-nitroaniline, we then demonstrated that the reduction of 4-nitroaniline detection was not due to drug-4-nitroaniline quenching of signal detection at OD405 nm. In conclusion, the results suggest that high concentrations of both cytoprotectives reduced 4-nitroaniline production in vitro, but the inhibition only occurs with concentrations 104-1025-fold that of EC50 values in an efficacy assay. Thus, CSMC-19 and CSMC-140 should be further developed and evaluated in embolic stroke models in the absence or presence of a thrombolytic. If necessary, they could be administered once effective tPA thrombolysis has been confirmed to avoid the possibility that the chromone will reduce the efficacy of tPA in patients. Stroke investigator developing new cytoprotective small molecules should consider adding this sensitive assay to their development and screening repertoire to assess possible drug-tPA interactions in vitro as a de-risking step.

Neuroprotection provided by isoflurane pre-conditioning and post-conditioning

Isoflurane, a volatile and inhalational anesthetic, has been extensively used in perioperative period for several decades. A large amount of experimental studies have indicated that isoflurane exhibits neuroprotective properties when it is administrated before or after (pre-conditioning and post-conditioning) neurodegenerative diseases (e.g., hypoxic ischemia, stroke and trauma). Multiple mechanisms are involved in isoflurane induced neuroprotection, including activation of glycine and γ-aminobutyric acid receptors, antagonism of ionic channels and alteration of the function and activity of other cellular proteins. Although neuroprotection provided by isoflurane is observed in many animal studies, convincing evidence is lacking in human trials. Therefore, there is still a long way to go before translating its neuroprotective properties into clinical practice.

Data Standardization and Quality Management

Important questions regarding the conduct of scientific research and data transparency have been raised in various scientific forums over the last 10 years. It is becoming clear, that in spite of published RIGOR guidelines, that improvement in the transparency of scientific research is required to focus on the discovery and drug development process so that a treatment can be provided to stroke patients. We have the unique privilege of conducting research using animal models of a disease so that we can address the development of a new therapy, and we should do this with great care and vigilance. This document identifies valuable resources for researchers to become Good Laboratory Practices compliant and increase and improve data transparency and provides guidelines for accurate data management to continue to propel the translational stroke research field forward while recognizing that there is a shortage of research funds worldwide. While data audits are being considered worldwide by funding agencies and they are used extensively by industry, they are still quite controversial for basic researchers. Due to the special exploratory nature of basic and translational science research, the current challenging funding environment, and independent and individualized laboratory activities, it is debatable if current individualized non-standardized data management and monitoring represents the best approach. Thus, herein, we propose steps to prepare research study data in an acceptable form for archival purposes so that standards for translational research data can be comparable to those that are accepted and adhered to by the clinical community. If all translational research laboratories follow and institute the guidelines while conducting translational research, data from all sources may be more comparable and reliable.

Optimizing image registration and infarct definition in stroke research

OBJECTIVE

Accurate representation of final infarct volume is essential for assessing the efficacy of stroke interventions in imaging-based studies. This study defines the impact of image registration methods used at different timepoints following stroke, and the implications for infarct definition in stroke research.

METHODS

Patients presenting with acute ischemic stroke were imaged serially using magnetic resonance imaging. Infarct volume was defined manually using four metrics: 24-h b1000 imaging; 1-week and 1-month T2-weighted FLAIR; and automatically using predefined thresholds of ADC at 24 h. Infarct overlap statistics and volumes were compared across timepoints following both rigid body and nonlinear image registration to the presenting MRI. The effect of nonlinear registration on a hypothetical trial sample size was calculated.

RESULTS

Thirty-seven patients were included. Nonlinear registration improved infarct overlap statistics and consistency of total infarct volumes across timepoints, and reduced infarct volumes by 4.0 mL (13.1%) and 7.1 mL (18.2%) at 24 h and 1 week, respectively, compared to rigid body registration. Infarct volume at 24 h, defined using a predetermined ADC threshold, was less sensitive to infarction than b1000 imaging. 1-week T2-weighted FLAIR imaging was the most accurate representation of final infarct volume. Nonlinear registration reduced hypothetical trial sample size, independent of infarct volume, by an average of 13%.

INTERPRETATION

Nonlinear image registration may offer the opportunity of improving the accuracy of infarct definition in serial imaging studies compared to rigid body registration, helping to overcome the challenges of anatomical distortions at subacute timepoints, and reducing sample size for imaging-based clinical trials.