Measuring Post-Stroke Cerebral Edema, Infarct Zone and Blood-Brain Barrier Breakdown in a Single Set of Rodent Brain Samples
October 23rd, 2020
This protocol describes a novel technique of measuring the three most important parameters of ischemic brain injury on the same set of rodent brain samples. Using only one brain sample is highly advantageous in terms of ethical and economic costs.
In the present protocol, we present a modified middle cerebral artery occlusion technique that measures ischemic brain injury to determinate an infarct zone, brain edema, and BBB permeability in the same set of rodent brains. In terms of ethical and economic costs, the main advantage of this technique is that only one brain sample is required for all three measurements. This assessment of the main parameters of ischemic brain injury will help to comprehensively investigate pathophysiology of ischemic stroke.
To begin, remove the rat brain, and cut 2 millimeter thick horizontal sections with a 0.009-inch stainless steel, uncoated, single edge razor blade. Place the sections in 0.005%TTC and incubate them for 30 minutes at 37 degrees Celsius, then place the brain tissue on the microscope slides and perform optical scanning of the six brain slices with a resolution of 1600 x 1600 DPI. Use a photo editor to add a blue filter to the images.
After opening the software, go to image, adjustments, and channel mixer. Select blue as the output channel and check monochrome, then click okay. Save the image in the JPEG file format.
Use the polygon selection tool in ImageJ version 1.37 to select each hemisphere of each of the six brain slices and save it as a separate image file. To calculate the infarct volume and brain edema, use a macro to convert the pixels in the image to white or black, based on a threshold. Then, close all files and use a second macro to compare the number of white and black pixels to determine the infarct volume and brain edema.
Copy the raw data to a spreadsheet. When calculating infarct volume, correct for tissue swelling by using the ratios of ipsilateral and contralateral cerebral hemispheres. Express the brain edema areas as a percentage of the standard areas of the unaffected contralateral hemisphere.
Determine blood brain barrier disruption 24 hours after occlusion. Divide the right and left hemispheres into six slices and put each slice into a microcentrifuge tube. Homogenize each slice of the brain tissue in trichloroacetic acid, using 4 milliliters of 50%trichloroacetic acid per gram of brain tissue.
Centrifuge the samples at 10, 000 times G for 20 minutes, then transfer the supernatant into a fresh tube and dilute it 1:3 with 96%ethanol. Perform luminescence spectrophotometry with a plate reader. An independent sample t-test indicated that 19 rats that underwent permanent middle cerebral artery occlusion, or MCAO, demonstrated a significant increase in brain infarct volume compared to the 16 sham operated rats.
The rats that underwent permanent MCAO also demonstrated a significant increase in the extent of brain edema and blood brain barrier breakdown after 24 hours, compared to the sham operated animals. When attempting this procedure, it is important to ensure that chemical concentration comply with the protocol. This protocol makes it possible to evaluate all three parameters of ischemic damage in one sample of the brain.
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Overview
This protocol details a modified middle cerebral artery occlusion technique to assess ischemic brain injury by evaluating infarct zones, brain edema, and blood-brain barrier (BBB) permeability in the same rodent brain samples. Utilizing a single brain sample enhances ethical and economic efficiency while allowing comprehensive examination of ischemic stroke pathophysiology.
Key Study Components
Area of Science
- Neuroscience
- Ischemic brain injury
- Rodent models
Background
- Ischemic stroke is a significant cause of morbidity and mortality.
- Evaluating multiple parameters of brain injury can enhance understanding of stroke mechanisms.
- Current methods often require multiple samples, creating ethical and resource constraints.
- This study introduces a streamlined approach to measure various damage indicators using one sample.
Purpose of Study
- To develop a technique for measuring infarct volume, edema, and BBB disruption in rodent brains.
- To improve resource efficiency and reduce reliance on multiple animal samples.
- To facilitate a more comprehensive understanding of ischemic brain injury and recovery.
Methods Used
- The method involves using rat brain samples after inducing ischemia via the middle cerebral artery occlusion.
- Brain sections are prepared and analyzed for various injury parameters including edema and BBB integrity.
- Key steps include image processing, pixel analysis for infarct volume calculations, and spectrophotometry for BBB disruption assessment.
- Data is quantified and compared between ischemic and control groups using statistical analysis.
Main Results
- The protocol allowed simultaneous measurement of infarct volume, edema, and BBB integrity in rat models.
- Significant increases in these parameters were observed in rats with induced ischemia compared to controls.
- Findings highlight the effectiveness of this technique in assessing ischemic damage while reducing animal use.
Conclusions
- This study demonstrates a novel method for the simultaneous assessment of key parameters of ischemic brain injury.
- The approach enhances understanding of stroke pathology and facilitates more ethical research practices.
- Implications extend to potential therapeutic developments and understanding of neuroprotective strategies.
Frequently Asked Questions
Executive Industry Relevance
Measuring multiple ischemic injury parameters in a single rodent brain sample reduces animal use and experimental variability, supporting ethical and cost-efficient preclinical stroke research. This integrated assessment enables more reliable target validation and mechanistic de-risking in neuroprotective drug discovery. The method enhances predictive confidence by correlating infarct volume, edema, and BBB permeability within the same biological system.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of therapeutic hypotheses by linking infarct zone, edema, and BBB breakdown in a unified pathophysiological readout.
- Operational Value: Reduces sample size requirements, improving throughput and consistency in target engagement studies.
Screening & Assay Development
- Scientific Value: Provides standardized, quantitative outputs for infarct volume and edema via pixel-based image analysis, supporting assay reproducibility.
- Operational Value: Uses accessible tools like ImageJ macros and spectrophotometry, facilitating technology transfer across discovery teams.
Translational & Preclinical Research
- Scientific Value: Aligns with disease-relevant systems by modeling key stroke pathophysiology endpoints in a single sample.
- Operational Value: Supports longitudinal assessment of biomarker continuity from discovery through preclinical validation.
Pipeline & Workflow Integration
The method fits within the discovery continuum from target validation to lead identification, offering multiparametric readouts that inform go/no-go decisions in stroke therapeutics.
- Discovery Biology: Supports pathway clarification by enabling concurrent measurement of structural and functional injury markers.
- Screening: Delivers assay-ready, quantitative data on infarct and edema through standardized image processing and normalization.
- Analytics: Generates comparable datasets via luminescence spectrophotometry for BBB integrity and corrected infarct volume calculations.
- Translational Research: Connects mechanistic findings to preclinical continuity by validating edema and BBB disruption as translatable injury biomarkers.
- Enterprise Reuse: Establishes a reusable platform for evaluating neuroprotective compounds across multiple injury dimensions.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence by reducing biological noise from inter-animal variability in multiparametric stroke assessment.
- Operational Value: Enhances standardization and scalability through defined sectioning, staining, and image analysis protocols.
- Strategic Value: Improves capital efficiency by minimizing animal consumption and enabling higher-information-content experiments.
- Portfolio Impact: Enables risk-adjusted prioritization of stroke therapeutics based on concordant infarct, edema, and BBB data.
Implementation Considerations
- Requires expertise in histology, image analysis (ImageJ), and spectrophotometry for accurate parameter quantification.
- Depends on precision instrumentation including microtomes, plate readers, and calibrated imaging systems.
- Necessitates cross-team standardization of staining thresholds, macro parameters, and data normalization procedures.
- Involves adaptation considerations when applying the protocol to different rodent strains or injury models.
- Practical limitations include dependency on consistent tissue sectioning and chemical reagent purity for reliable BBB measurements.
