Quantitative Foot Muscle Magnetic Resonance Imaging Reliably Measures Disease Progression in Children and Adolescents with Charcot-Marie-Tooth Disease Type 1A

Quantitative muscle fat fraction (FF) responsiveness is lower in younger Charcot-Marie-Tooth disease type 1A (CMT1A) patients with lower baseline calf-level FF. We investigated the practicality, validity, and responsiveness of foot-level FF in this cohort involving 22 CMT1A patients and 14 controls. The mean baseline foot-level FF was 25.9 ± 20.3% in CMT1A patients, and the 365-day FF (n = 15) increased by 2.0 ± 2.4% (p < 0.001 vs controls). Intrinsic foot-level FF demonstrated large responsiveness (12-month standardized response mean (SRM) of 0.86) and correlated with the CMT examination score (ρ = 0.58, P = 0.01). Intrinsic foot-level FF has the potential to be used as a biomarker in future clinical trials involving younger CMT1A patients. ANN NEUROL 2024.

Lower limb muscle MRI fat fraction is a responsive outcome measure in CMT X1, 1B and 2A

OBJECTIVE

With potential therapies for many forms of Charcot-Marie-Tooth disease (CMT), responsive outcome measures are urgently needed for clinical trials. Quantitative lower limb MRI demonstrated progressive calf intramuscular fat accumulation in the commonest form, CMT1A with large responsiveness. In this study, we evaluated the responsiveness and validity in the three other common forms, due to variants in GJB1 (CMTX1), MPZ (CMT1B) and MFN2 (CMT2A).

METHODS

22 CMTX1, 21 CMT1B and 21 CMT2A patients and matched controls were assessed at a 1-year interval. Intramuscular fat fraction (FF) was evaluated using three-point Dixon MRI at thigh and calf level along with clinical measures including CMT examination score, clinical strength assessment, CMT-HI and plasma neurofilament light chain.

RESULTS

All patient groups had elevated muscle fat fraction at thigh and calf levels, with highest thigh FF and atrophy in CMT2A. There was moderate correlation between calf muscle FF and clinical measures (CMTESv2 rho = 0.405; p = 0.001, ankle MRC strength rho = -0.481; p < 0.001). Significant annualised progression in calf muscle FF was seen in all patient groups (CMTX1 2.0 ± 2.0%, p < 0.001, CMT1B 1.6 ± 2.1% p = 0.004 and CMT2A 1.6 ± 2.1% p = 0.002). Greatest increase was seen in patients with 10-70% FF at baseline (calf 2.7 ± 2.3%, p < 0.0001 and thigh 1.7 ± 2.1%, p = 0.01).

INTERPRETATION

Our results confirm that calf muscle FF is highly responsive over 12 months in three additional common forms of CMT which together with CMT1A account for 90% of genetically confirmed cases. Calf muscle MRI FF should be a valuable outcome measure in upcoming CMT clinical trials.

Lateral Septal Circuits Govern Schizophrenia-Like Effects of Ketamine on Social Behavior

Schizophrenia is marked by poor social functioning that can have a severe impact on quality of life and independence, but the underlying neural circuity is not well understood. Here we used a translational model of subanesthetic ketamine in mice to delineate neural pathways in the brain linked to social deficits in schizophrenia. Mice treated with chronic ketamine (30 mg/kg/day for 10 days) exhibit profound social and sensorimotor deficits as previously reported. Using three- dimensional c-Fos immunolabeling and volume imaging (iDISCO), we show that ketamine treatment resulted in hypoactivation of the lateral septum (LS) in response to social stimuli. Chemogenetic activation of the LS rescued social deficits after ketamine treatment, while chemogenetic inhibition of previously active populations in the LS (i.e. social engram neurons) recapitulated social deficits in ketamine-naïve mice. We then examined the translatome of LS social engram neurons and found that ketamine treatment dysregulated genes implicated in neuronal excitability and apoptosis, which may contribute to LS hypoactivation. We also identified 38 differentially expressed genes (DEGs) in common with human schizophrenia, including those involved in mitochondrial function, apoptosis, and neuroinflammatory pathways. Chemogenetic activation of LS social engram neurons induced downstream activity in the ventral part of the basolateral amygdala, subparafascicular nucleus of the thalamus, intercalated amygdalar nucleus, olfactory areas, and dentate gyrus, and it also reduces connectivity of the LS with the piriform cortex and caudate-putamen. In sum, schizophrenia-like social deficits may emerge via changes in the intrinsic excitability of a discrete subpopulation of LS neurons that serve as a central hub to coordinate social behavior via downstream projections to reward, fear extinction, motor and sensory processing regions of the brain.

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.

137 Outcome measures in CMT: case examples from the muscle MRI in CMT study

Background

Twelve month increase in muscle fat fraction(FF) at calf has been demonstrated in patients with CMT1A.(1,2) Our MDA funded study builds on our previous work by investigating this method in patients with the three next most common subtypes of CMT: due to mutations in GJ1B, MPZ, and MFN2.

Methods

Sixty participants and 30 controls have been recruited. In select examples, baseline and follow-up FF were calculated at mid-calf and mid-thigh.

Results

A 45-year-old male with a MPZ mutation had imaging age 35 (CMTES 17), with FF at calf 20.9%. At age 45, CMTES was 20 and calf FF 35.6%. In a 32-year-old male with GJB1, CMTES rose from 9 to 10 at 12 months, with all muscle mid-calf FF rising from 9.5% to 11.8%. In the left peroneus longus, FF increased from 26% to 55% correlating with reduced ankle plantarflexion power. In a MFN2 patient, baseline CMTES was 16 and at 12-months 17. FF increased at thigh level from 10.5% to 15%.

Discussion

We present three cases illustrating key points from the study and demonstrate an increase in FF at 12 months in one patient each with CMT1X and CMT2A, and over 10 years in a patient with CMT1B.

carolynnedoherty@doctors.org.uk|NIHR Bursary

The Stroke Preclinical Assessment Network: Rationale, Design, Feasibility, and Stage 1 Results

Cerebral ischemia and reperfusion initiate cellular events in brain that lead to neurological disability. Investigating these cellular events provides ample targets for developing new treatments. Despite considerable work, no such therapy has translated into successful stroke treatment. Among other issues-such as incomplete mechanistic knowledge and faulty clinical trial design-a key contributor to prior translational failures may be insufficient scientific rigor during preclinical assessment: nonblinded outcome assessment; missing randomization; inappropriate sample sizes; and preclinical assessments in young male animals that ignore relevant biological variables, such as age, sex, and relevant comorbid diseases. Promising results are rarely replicated in multiple laboratories. We sought to address some of these issues with rigorous assessment of candidate treatments across 6 independent research laboratories. The Stroke Preclinical Assessment Network (SPAN) implements state-of-the-art experimental design to test the hypothesis that rigorous preclinical assessment can successfully reduce or eliminate common sources of bias in choosing treatments for evaluation in clinical studies. SPAN is a randomized, placebo-controlled, blinded, multilaboratory trial using a multi-arm multi-stage protocol to select one or more putative stroke treatments with an implied high likelihood of success in human clinical stroke trials. The first stage of SPAN implemented procedural standardization and experimental rigor. All participating research laboratories performed middle cerebral artery occlusion surgery adhering to a common protocol and rapidly enrolled 913 mice in the first of 4 planned stages with excellent protocol adherence, remarkable data completion and low rates of subject loss. SPAN stage 1 successfully implemented treatment masking, randomization, prerandomization inclusion/exclusion criteria, and blinded assessment to exclude bias. Our data suggest that a large, multilaboratory, preclinical assessment effort to reduce known sources of bias is feasible and practical. Subsequent SPAN stages will evaluate candidate treatments for potential success in future stroke clinical trials using aged animals and animals with comorbid conditions.

PKM2 promotes neutrophil activation and cerebral thromboinflammation: therapeutic implications for ischemic stroke

There is a critical need for cerebro-protective interventions to improve the suboptimal outcomes of patients with ischemic stroke who have been treated with reperfusion strategies. We found that nuclear pyruvate kinase muscle 2 (PKM2), a modulator of systemic inflammation, was upregulated in neutrophils after the onset of ischemic stroke in both humans and mice. Therefore, we determined the role of PKM2 in stroke pathogenesis by using murine models with preexisting comorbidities. We generated novel myeloid cell-specific PKM2-/- mice on wild-type (PKM2fl/flLysMCre+) and hyperlipidemic background (PKM2fl/flLysMCre+Apoe-/-). Controls were littermate PKM2fl/flLysMCre- or PKM2fl/flLysMCre-Apoe-/- mice. Genetic deletion of PKM2 in myeloid cells limited inflammatory response in peripheral neutrophils and reduced neutrophil extracellular traps after cerebral ischemia and reperfusion, suggesting that PKM2 promotes neutrophil hyperactivation in the setting of stroke. In the filament and autologous clot and recombinant tissue plasminogen activator stroke models, irrespective of sex, deletion of PKM2 in myeloid cells in either wild-type or hyperlipidemic mice reduced infarcts and enhanced long-term sensorimotor recovery. Laser speckle imaging revealed improved regional cerebral blood flow in myeloid cell-specific PKM2-deficient mice that was concomitant with reduced post-ischemic cerebral thrombo-inflammation (intracerebral fibrinogen, platelet [CD41+] deposition, neutrophil infiltration, and inflammatory cytokines). Mechanistically, PKM2 regulates post-ischemic inflammation in peripheral neutrophils by promoting STAT3 phosphorylation. To enhance the translational significance, we inhibited PKM2 nuclear translocation using a small molecule and found significantly reduced neutrophil hyperactivation and improved short-term and long-term functional outcomes after stroke. Collectively, these findings identify PKM2 as a novel therapeutic target to improve brain salvage and recovery after reperfusion.

Abstract 107: PKM2 Promotes Neutrophil Activation And Cerebral Thrombo-inflammation: Therapeutic Implications For Ischemic Stroke

In recent years compelling evidence has emerged that implicates role of metabolic reprogramming in the modulation of thrombosis and inflammation. The dimeric form of the metabolic enzyme pyruvate kinase muscle 2 (PKM2) enters nucleus and exerts protein kinase activity. We found that nuclear PKM2 levels were upregulated in neutrophils after the onset of ischemic stroke both in humans and in mice. Therefore, we evaluated the role of PKM2 in promoting thrombo-inflammation and ischemic brain injury.We generated novel myeloid cell-specific PKM2 -/- mice on wild-type ( PKM2 fl/fl LysMCre + ) and hyperlipidemic background ( PKM2 fl/fl LysMCre + Apoe -/- ). We observed that genetic deletion of PKM2 in myeloid cells limited inflammatory response in peripheral neutrophils and reduced neutrophil extracellular traps following cerebral ischemia/reperfusion. In the filament and autologous clot/rtPA stroke models, irrespective of sex, deletion of PKM2 in myeloid cells either in wild-type or hyperlipidemic mice reduced infarcts and enhanced long-term sensorimotor recovery. Laser speckle imaging revealed improved regional cerebral blood flow in myeloid cell-specific PKM2-deficient mice that was concomitant with reduced post-ischemic cerebral thrombo-inflammation (intracerebral fibrin(ogen), platelet (CD41- positive) deposition, neutrophil infiltration, and inflammatory cytokines). Mechanistically, PKM2 regulates post-ischemic inflammation in peripheral neutrophils by promoting STAT3 phosphorylation. Utilizing small molecule inhibitor (ML265) that inhibits PKM2 dimerization, we evaluated ex vivo thrombosis using human whole blood in a microfluidic flow chamber system. We observed a fivefold reduction in the thrombus growth rate in ML265-treated group. Similarly, ML265 treatment in mice resulted into significantly reduced poststroke neutrophil hyperactivation and improved short-term and long-term functional outcomes following stroke. Collectively, these findings identify PKM2 as a novel therapeutic target to improve brain salvage and recovery following reperfusion.

Fully automated 3D segmentation of MR-imaged calf muscle compartments: Neighborhood relationship enhanced fully convolutional network

Automated segmentation of individual calf muscle compartments from 3D magnetic resonance (MR) images is essential for developing quantitative biomarkers for muscular disease progression and its prediction. Achieving clinically acceptable results is a challenging task due to large variations in muscle shape and MR appearance. In this paper, we present a novel fully convolutional network (FCN) that utilizes contextual information in a large neighborhood and embeds edge-aware constraints for individual calf muscle compartment segmentations. An encoder-decoder architecture is used to systematically enlarge convolution receptive field and preserve information at all resolutions. Edge positions derived from the FCN output muscle probability maps are explicitly regularized using kernel-based edge detection in an end-to-end optimization framework. Our method was evaluated on 40 T1-weighted MR images of 10 healthy and 30 diseased subjects by fourfold cross-validation. Mean DICE coefficients of 88.00-91.29% and mean absolute surface positioning errors of 1.04-1.66 mm were achieved for the five 3D muscle compartments.

Low-Frequency Vibrations Enhance Thrombolytic Therapy and Improve Stroke Outcomes

Background and Purpose- We aim to determine the potential impact on stroke thrombolysis of drip-and-ship helicopter flights and specifically of their low-frequency vibrations (LFVs). Methods- Mice with a middle cerebral artery autologous thromboembolic occlusion were randomized to receive rtPA (recombinant tissue-type plasminogen activator; or saline) 90 minutes later in 3 different settings: (1) a motion platform simulator that reproduced the LFV signature of the helicopter, (2) a standardized actual helicopter flight, and (3) a ground control. Results- Mice assigned to the LFV simulation while receiving tPA had smaller infarctions (31.6 versus 54.9 mm3; P=0.007) and increased favorable neurological outcomes (86% versus 28%; P=0.0001) when compared with ground controls. Surprisingly, mice receiving tPA in the helicopter did not exhibit smaller infarctions (47.8 versus 54.9 mm3; P=0.58) nor improved neurological outcomes (37% versus 28%; P=0.71). This could be due to a causative effect of the 20- to 30-Hz band, which was inadvertently attenuated during actual flights. Mice using saline showed no differences between the LFV simulator and controls with respect to infarct size (80.9 versus 95.3; P=0.81) or neurological outcomes (25% versus 11%; P=0.24), ruling out an effect of LFV alone. There were no differences in blood-brain barrier permeability between LFV simulator or helicopter, compared with controls (2.45-3.02 versus 4.82 mm3; P=0.14). Conclusions- Vibration in the low-frequency range (0.5-120 Hz) is synergistic with rtPA, significantly improving the effectiveness of thrombolysis without impairing blood-brain barrier permeability. Our findings reveal LFV as a novel, safe, and simple-to-deliver intervention that could improve the outcomes of patients. Visual Overview- An online visual overview is available for this article.

Abstract WMP79: Recapitulation on the Ground of Helicopter Flight Low Frequency Vibration Enhances Stroke Thrombolysis

Background: Understanding the potential effects on stroke outcome of the unique physical factors present in a helicopter ambulance flight is critical in the era of thrombectomy. However, this factor in patient care has not been adequately investigated.

Methods: This was a prospective randomized blinded end-point animal study. A murine model of middle cerebral artery autologous thromboembolic occlusion (eMCAO) with rtPA reperfusion was exposed to three different settings: 1) a standardized actual helicopter flight, 2) a motion platform simulator that delivered the exact LFV signature of the helicopter, and 3) a ground control. Outcome measures included infarct size and BBB permeability on MRI, and neurological scores.

Results: A total of 106 mice were analyzed. Within the rtPA group, LFV simulator mice displayed lower infarction volumes on MRI (31.6 vs. 54.9 mm 3 , p=0.007) and improved neurological scores (87 vs. 28%, p=0.0001) compared to ground control mice. By contrast, mice receiving saline did not show change in either infarction volume (80.9 vs. 95.3, p=0.8) or neurological scores (37 vs. 28%, p=0.7). No differences were seen in the actual helicopter flight group as compared with ground control. No treatment group showed any difference in permeability of the blood brain barrier, assessed by MRI.

Conclusion: We found a synergistic beneficial effect of combining helicopter-like LFV and rtPA, which could provide a novel, safe, and potentially more efficacious intervention for patients with stroke. These results also suggest that non-LFV helicopter physical factors, such, as hypobaric environment, accelerations and noise, may have a negating effect on the otherwise positive effect of helicopter vibration on stroke outcomes. If so, strategies to minimize these negating factors might be expected to improve patient outcome.

Fn-EDA (Fibronectin Containing Extra Domain A) in the Plasma, but Not Endothelial Cells, Exacerbates Stroke Outcome by Promoting Thrombo-Inflammation

Background and Purpose- Cellular Fn-EDA (fibronectin containing extra domain A) is expressed in activated endothelial cells and elevated in circulation in patients with cardiovascular diseases. Although global deficiency of Fn-EDA in mice improves stroke outcome, the specific contribution of plasma versus endothelium Fn-EDA in stroke outcome is currently unknown. We investigated the role of plasma versus endothelial Fn-EDA in stroke exacerbation in the comorbid condition of hyperlipidemia. Methods- We generated novel plasma Fn-EDA^-/- ( Fn-EDA ^fl/fl Alb ^Cre) and endothelial Fn-EDA^-/- ( Fn-EDA ^fl/fl Tie2 ^Cre) strains on hyperlipidemic apolipoprotein E-deficient ( ApoE^-/-) background. By following the Stroke Therapy Academic Industry Roundtable guidelines, we evaluated stroke outcome in male and female mice. Susceptibility to ischemia/reperfusion injury was evaluated in 2 different models of stroke: intraluminal monofilament and embolic model on days 1, 3, and 7. Quantitative assessment of stroke outcome was evaluated by measuring infarct volume (by magnetic resonance imaging), cerebral blood flow (by laser speckle imaging), neurological and sensory-motor outcome, and postischemic thrombo-inflammation (platelet thrombi, fibrin, neutrophil, phospho-NFκB [nuclear factor κB], TNFα [tumor necrosis factor α], and IL1β [interleukin 1β]). Results- Stroke outcome was comparable in ApoE^-/- Fn-EDA ^fl/fl Tie2 ^Cre and control ApoE^-/- Fn-EDA ^fl/fl mice suggesting endothelial Fn-EDA does not contribute to stroke. ApoE^-/- Fn-EDA ^fl/fl Alb ^Cre mice exhibited significantly smaller infarcts and improved neurological and sensory-motor outcome at days 1, 3, and 7 in monofilament and embolic models of stroke. Improved stroke outcome was concomitant with enhanced survival, and decreased postischemic thrombo-inflammatory response ( P<0.05 versus ApoE^-/- Fn-EDA ^fl/fl). No sex-based differences were observed. Laser speckle imaging revealed significantly improved regional cerebral blood flow at 1 hour in ApoE^-/- Fn-EDA ^fl/fl Alb ^Cre mice suggesting plasma Fn-EDA promotes postischemic secondary thrombosis. Coinfusion of anti-Fn-EDA antibody with r-tPA (recombinant tissue-type plasminogen activator) in ApoE^-/- mice, 1 hour after embolization, improved stroke outcome with enhanced survival, and improved neurological outcome ( P<0.05 versus r-tPA). Conclusions- Genetic evidence suggests that plasma Fn-EDA exacerbates stroke outcome by promoting postischemic thrombo-inflammation. Interventions targeting plasma Fn-EDA may reduce brain damage after reperfusion.

High-energy external defibrillation and transcutaneous pacing during MRI: feasibility and safety

BACKGROUND

Rapid application of external defibrillation, a crucial first-line therapy for ventricular fibrillation and cardiac arrest, is currently unavailable in the setting of magnetic resonance imaging (MRI), raising concerns about patient safety during MRI tests and MRI-guided procedures, particularly in patients with cardiovascular diseases. The objective of this study was to examine the feasibility and safety of defibrillation/pacing for the entire range of clinically useful shock energies inside the MRI bore and during scans, using defibrillation/pacing outside the magnet as a control.

METHODS

Experiments were conducted using a commercial defibrillator (LIFEPAK 20, Physio-Control, Redmond, Washington, USA) with a custom high-voltage, twisted-pair cable with two mounted resonant floating radiofrequency traps to reduce emission from the defibrillator and the MRI scanner. A total of 18 high-energy (200-360 J) defibrillation experiments were conducted in six swine on a 1.5 T MRI scanner outside the magnet bore, inside the bore, and during scanning, using adult and pediatric defibrillation pads. Defibrillation was followed by cardiac pacing (with capture) in a subset of two animals. Monitored signals included: high-fidelity temperature (0.01 °C, 10 samples/sec) under the pads and 12-lead electrocardiogram (ECG) using an MRI-compatible ECG system.

RESULTS

Defibrillation/pacing was successful in all experiments. Temperature was higher during defibrillation inside the bore and during scanning compared with outside the bore, but the differences were small (ΔT: 0.5 and 0.7 °C, p = 0.01 and 0.04, respectively). During scans, temperature after defibrillation tended to be higher for pediatric vs. adult pads (p = 0.08). MR-image quality (signal-to-noise ratio) decreased by ~ 10% when the defibrillator was turned on.

CONCLUSIONS

Our study demonstrates the feasibility and safety of in-bore defibrillation for the full range of defibrillation energies used in clinical practice, as well as of transcutaneous cardiac pacing inside the MRI bore. Methods for Improving MR-image quality in the presence of a working defibrillator require further study.

Magnetic Resonance Imaging of Contracting Ultrathin Cardiac Tissue

OBJECTIVE

Integrating cardiac-tissue patches into the beating heart and evaluating the long-term effects of such integration on cardiac contractility are two challenges in an emerging field of regenerative medicine. This pilot study presents tools for the imaging of contracting multicellular cardiac tissue constructs (MTCs) in vitro and demonstrates the feasibility of tracking the early development of strand geometry and contractions in ultrathin strands and layers of cardiac tissue using CINE MRI.

APPROACH

Cultured, ultrathin (~50-100-micron) MTCs of rat neonatal cardiomyocytes were plated in rectangular cell chambers (4.5 × 2.0 cm) with and without ultrathin, carbon EP electrodes embedded in the floor of the cell chamber. Two-dimensional, steady-state free precession (SSFP) CINE MRI, cell microscopy, and tissue photography were performed on Days 5-9 of cell development. Potential confounders and MRI artifacts were evaluated using non-contracting cardiac tissues and cell-free chambers filled with the cell-culture medium.

MAIN RESULTS

Synchronized contractions formed by Day 7; individual contracting tissue strands became identifiable by Day 9. The global patterns and details of the strand geometry and movement patterns in the SSFP images were in excellent agreement with microscopic and photographic images. No synchronized movement was identifiable by either microscopy or CINE MRI in the non-contracting MTCs or the cell-free medium. The EP recordings revealed well-defined depolarization and repolarization waveforms; the imaging artifacts generated by the carbon electrodes were small.

SIGNIFICANCE

This pilot study demonstrates the feasibility of imaging cardiac-strand patterns and contractile activity in ultrathin, two-dimensional cardiac tissue in commonly used clinical scanners.

Validation of MRC Centre MRI calf muscle fat fraction protocol as an outcome measure in CMT1A

OBJECTIVE

To translate the quantitative MRC Centre MRI protocol in Charcot-Marie-Tooth disease type 1A (CMT1A) to a second site; validate its responsiveness in an independent cohort; and test the benefit of participant stratification to increase outcome measure responsiveness.

METHODS

Three healthy volunteers were scanned for intersite standardization. For the longitudinal patient study, 11 patients with CMT1A were recruited with 10 patients rescanned at a 12-month interval. Three-point Dixon MRI of leg muscles was performed to generate fat fraction (FF) maps, transferred to a central site for quality control and analysis. Clinical data collected included CMT Neuropathy Score.

RESULTS

Test-retest reliability of FF within individual healthy calf muscles at the remote site was excellent: intraclass correlation coefficient 0.79, limits of agreement -0.67 to +0.85 %FF. In patients, mean calf muscle FF was 21.0% and correlated strongly with disease severity and age. Calf muscle FF significantly increased over 12 months (+1.8 ± 1.7 %FF, p = 0.009). Patients with baseline FF >10% showed a 12-month FF increase of 2.9% ± 1.3% (standardized response mean = 2.19).

CONCLUSIONS

We have validated calf muscle FF as an outcome measure in an independent cohort of patients with CMT1A. Responsiveness is significantly improved by enrolling a stratified patient cohort with baseline calf FF >10%.

Treatment with Uric Acid Reduces Infarct and Improves Neurologic Function in Female Mice After Transient Cerebral Ischemia

BACKGROUND

Exogenous administration of uric acid, a naturally occurring antioxidant that scavenges reactive oxygen species in vasculature, has shown protective efficacy in both rodent models of stroke and human stroke patients in Spain as an adjuvant treatment to mechanical thrombectomy. Before clinical trials can be initiated in the United States, however, confirmation of efficacy in alternative preclinical models is required in accordance with stroke therapy academic industry roundtable-RIGOR criteria. To date, preclinical efficacy has only been established in the acute setting in male rodents.

METHODS

To address this need, we subjected 7- to 9-week old ovariectomized female mice to filament-induced right middle cerebral artery ischemia and reperfusion, an established preclinical model of mechanical thrombectomy. Fidelity of the procedure was monitored by laser Doppler flowmetry. A separate lab randomly assigned animals to vehicle versus uric acid infusion, which was initiated immediately after 45 minutes of reperfusion. Poststroke analysis of infarction size and neurologic function were conducted by investigators blind to treatment group, with a 7-day primary endpoint and a 3-day intermediary analysis at 1and.

RESULTS

Infarct size and neurologic function at 7 days poststroke were significantly improved in uric acid-treated animals, relative to vehicle.

CONCLUSION

Efficacy of uric acid in preclinical models of stroke is now expanded to include female mice analyzed at a later time point than has been investigated previously. These results support stroke therapy academic industry roundtable-RIGOR driven determination of the suitability of acute administration of uric acid as an adjuvant to mechanical thrombectomy in clinical trials for patients with stroke.

Abstract WP260: Uric Acid Reduces Infarct and Improves Neurological Function in Female Mice One Week After Transient Cerebral Ischemia

Background & Purpose: Exogenous administration of uric acid, a naturally occurring antioxidant that scavenges reactive oxygen species in vasculature, has shown protective efficacy in both rodent models of stroke and in human stroke patients in Spain as an adjuvant treatment to mechanical thrombectomy. In accordance with STAIR-RIGOR criteria, confirmation of efficacy in alternative preclinical models is required before clinical trials can be initiated in the United States. To date, preclinical efficacy has only been established in the acute setting in male rodents.

Methods: Seven to nine week old ovariectomized female mice were subjected to filament-induced right middle cerebral artery ischemia and reperfusion, an established preclinical model of mechanical thrombectomy. Fidelity of the procedure was monitored by laser Doppler flowmetry in all animals. A separate lab randomly assigned animals to vehicle vs uric acid infusion, which was initiated immediately after 45 minutes of reperfusion. Post-stroke analysis of infarction size and neurological function were conducted by investigators blind to treatment group, with a 7 day primary endpoint and intermediary analysis at 1and 3 days.

Results: Infarct size and neurological function at 7 days post-stroke was significantly improved in uric acid-treated animals, relative to vehicle.

Conclusions: Efficacy of uric acid in preclinical models of stroke is now expanded to include female mice analyzed at a more chronic time point than has been investigated previously. These results supports STAIR-RIGOR driven determination of the suitability of acute administration of uric acid as an adjuvant to mechanical thrombectomy in clinical trials for patients with stroke.

Abstract 70: Targeting Myeloid Specific Neutrophil Integrin α9β1 Improves Stroke Outcome Following Transient Cerebral Ischemia in Comorbid Condition of Hyperlipidemia

Background and Hypothesis: Neutrophils infiltration following reperfusion is the hallmark of ischemic stroke. Integrin α9β1 is highly expressed on neutrophils, upregulated upon activation, stabilizes adhesion to activated endothelium in synergy with β2 integrin, and plays a role in transmigration. Fibronectin containing alternatively spliced extra domain A (Fn-EDA) is a ligand for integrin α9β1, and is known to be pro-thrombotic and pro-inflammatory. The role of α9β1 in ischemic stroke is not elucidated yet. Following STAIR guidelines, we tested the hypothesis that integrin α9β1/Fn-EDA axis contributes to the pathophysiology of ischemic stroke in comorbid condition of hyperlipidemia.

Methods: Susceptibility to brain ischemia/reperfusion injury was evaluated in male and female mice (N=14-16) by transient occlusion of middle cerebral artery (1 hr) followed by 1, 3, and 7 days of reperfusion. Quantitative assessment of stroke outcome was evaluated by measuring infarct volume (MRI), neurological outcome (0-4), and post ischemic thrombo-inflammation (fibrin, neutrophil and inflammatory cytokines) within ischemic region (by Western and immunohistochemistry). Using intravital microscopy, susceptibility to arterial thrombosis was evaluated in FeCl 3 and laser injury-induced thrombosis models.

Results: Irrespective of gender, myeloid specific α 9 β 1 -/- mice on wild-type and hyperlipidemic background ( α 9 fl/fl LysMCre and α 9 fl/fl LysMCreApoe -/- ) exhibited smaller infarcts and improved neurological outcomes at days 1, 3 and 7 concomitant with enhanced survival rate and decreased post ischemic thrombo-inflammation (P<0.05 vs. α 9 fl/fl or α 9 fl/fl Apoe -/- mice littermates). Intravital microscopy showed that myeloid specific α 9 β 1 -/- mice were less susceptible to arterial thrombosis compared to controls (P<0.05). Bone marrow transplantation experiments revealed that Fn-EDA contributes to α9β1 mediated stroke exacerbation. Infusion of a specific inhibitor of α9β1 into Apoe -/- mouse 15 minutes after reperfusion significantly improved stroke outcome.

Conclusions: Following STAIR guidelines, we provide genetic and pharmacologic evidence that targeting myeloid specific integrin α9β1 in hyperlipidemic mice improves stroke outcome.

Segmentation of wall and plaque in in vitro vascular MR images

Atherosclerosis leads to heart attack and stroke, which are major killers in the western world. These cardiovascular events frequently result from local rupture of vulnerable atherosclerotic plaque. Non-invasive assessment of plaque vulnerability would dramatically change the way in which atherosclerotic disease is diagnosed, monitored, and treated. In this paper, we report a computerized method for segmentation of arterial wall layers and plaque from high-resolution volumetric MR images. The method uses dynamic programming to detect optimal borders in each MRI frame. The accuracy of the results was tested in 62 T1-weighted MR images from six vessel specimens in comparison to borders manually determined by an expert observer. The mean signed border positioning errors for the lumen, internal elastic lamina, and external elastic lamina borders were -0.1 +/- 0.1, 0.0 +/- 0.1, and -0.1 +/- 0.1 mm, respectively. The presented wall layer segmentation approach is one of the first steps towards non-invasive assessment of plaque vulnerability in atherosclerotic subjects.