Analysis of Cerebral Vasospasm in a Murine Model of Subarachnoid Hemorrhage with High Frequency Transcranial Duplex Ultrasound
June 3rd, 2021
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The aim of this manuscript is to present a sonography-based method that allows in vivo imaging of blood flow in cerebral arteries in mice. We demonstrate its application to determine changes in blood flow velocities associated with vasospasm in murine models of subarachnoid hemorrhage (SAH).
Overview
This article demonstrates a protocol for noninvasive, in vivo monitoring of cerebral vasospasm in mice following subarachnoid hemorrhage (SAH) using high-frequency color-coded duplex sonography. The method enables longitudinal assessment of blood flow velocities in intracranial and extracranial internal carotid arteries, providing a functional approach to detect vasospasm in murine SAH models.
Key Study Components
Area of Science
- Neuroscience
- Cerebrovascular research
- Imaging techniques
Background
- Cerebral vasospasm is a major complication after subarachnoid hemorrhage, leading to delayed cerebral ischemia.
- Reliable in vivo monitoring methods for cerebral vasospasm in murine models have been lacking.
- High-frequency ultrasound offers a noninvasive imaging modality for vascular assessment.
- Transcranial duplex sonography is established in clinical settings but less common in small animal research.
Purpose of Study
- To establish and demonstrate a protocol for in vivo monitoring of cerebral vasospasm in mice after SAH.
- To assess changes in blood flow velocities in intracranial and extracranial internal carotid arteries.
- To provide a noninvasive, functional imaging method suitable for longitudinal studies in murine models.
Methods Used
- Induction of subarachnoid hemorrhage or sham surgery in female C57BL/6N mice.
- Application of high-frequency color-coded duplex sonography under isoflurane anesthesia.
- Measurement of blood flow velocities in intracranial and extracranial internal carotid arteries using B-mode, CW-Doppler, and pulse wave Doppler imaging.
- Post-processing of ultrasound data to quantify peak systolic velocity, end diastolic velocity, and velocity time integral.
Main Results
- Before surgery, intra- and extracranial blood flow velocities were similar between SAH and sham groups.
- On days three and seven post-SAH, intracranial blood flow velocities increased markedly in SAH mice, indicating cerebral vasospasm.
- Extracranial blood flow velocities remained largely unchanged after SAH.
- The ratio of intra- to extracranial blood flow velocities increased significantly in SAH animals by day seven.
Conclusions
- High-frequency transcranial duplex sonography enables noninvasive, functional monitoring of cerebral vasospasm in mice.
- The method allows for longitudinal studies and parallels clinical findings in human SAH patients.
- This protocol provides a valuable tool for cerebrovascular research in murine models.
Frequently Asked Questions
What is the main advantage of using high-frequency duplex sonography in this protocol?
It provides a noninvasive, functional, and longitudinal method to monitor cerebral vasospasm in vivo in murine models.
How is cerebral vasospasm detected using this method?
Cerebral vasospasm is indicated by a significant increase in intracranial blood flow velocities, while extracranial velocities remain unchanged.
What animal model was used in this study?
Female C57BL/6N mice aged 11 to 12 weeks were used for SAH induction or sham surgery.
Which arteries are monitored for blood flow velocities?
Both intracranial and extracranial internal carotid arteries are monitored using duplex sonography.
What imaging modes are utilized in the ultrasound protocol?
B-mode, continuous wave (CW) Doppler, and pulse wave (PW) Doppler imaging modes are used to acquire anatomical and flow data.
How does this method compare to clinical monitoring in humans?
The protocol mirrors clinical approaches, as increased intracranial blood flow velocities after SAH are also used to indicate vasospasm in human patients.
Can this protocol be used for longitudinal studies?
Yes, the noninvasive nature of the method allows repeated measurements over time in the same animal.
Executive Industry Relevance
Noninvasive, high-frequency transcranial duplex ultrasound enables functional monitoring of cerebral vasospasm in murine subarachnoid hemorrhage (SAH) models, addressing a critical gap in preclinical cerebrovascular research. This capability supports predictive confidence in translational stroke studies and informs early-stage target validation for vascular interventions. The method's longitudinal design enhances portfolio decision-making by enabling repeated, quantitative assessment of vascular responses in vivo.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables functional interrogation of cerebrovascular response to SAH in disease-relevant murine models.
- Supports biological de-risking by quantifying intracranial blood flow changes indicative of vasospasm.
- Facilitates predictive confidence in target validation for vascular and neuroprotective therapeutics.
Screening & Assay Development
- Provides a validated, reproducible imaging workflow for in vivo vascular assessment in mice.
- Generates quantitative outputs (peak systolic velocity, end diastolic velocity, velocity time integral) for robust assay development.
- Enables screening of candidate interventions for impact on cerebral vasospasm with high temporal resolution.
Translational & Preclinical Research
- Aligns preclinical vascular readouts with clinical endpoints used in human SAH monitoring.
- Supports longitudinal studies to track disease progression and therapeutic response over time.
- Improves risk-adjusted advancement decisions by providing mechanistic insight into cerebrovascular dynamics.
Pipeline & Workflow Integration
This imaging protocol integrates into the discovery-to-preclinical continuum, bridging early mechanistic studies and translational validation in cerebrovascular research.
- Discovery Biology: Quantifies vascular response to SAH, supporting hypothesis testing and mechanistic de-risking.
- Screening: Delivers reproducible, quantitative imaging outputs for candidate evaluation.
- Analytics: Provides statistical measurements of blood flow velocities for condition comparison and trend analysis.
- Translational Research: Mirrors clinical monitoring strategies, enhancing preclinical-to-clinical continuity.
- Enterprise Reuse: Establishes a reusable, noninvasive imaging platform for diverse cerebrovascular studies in murine models.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence and reduces mechanistic ambiguity in cerebrovascular target validation.
- Operational Value: Standardizes in vivo vascular assessment with scalable, reproducible imaging protocols.
- Strategic Value: Informs go/no-go decisions and optimizes resource allocation by enabling early detection of vascular phenotypes.
- Portfolio Impact: Supports risk-adjusted prioritization of vascular and neuroprotective therapeutic candidates.
Implementation Considerations
- Requires expertise in high-frequency ultrasound imaging and murine anesthesia management.
- Demands access to advanced imaging instrumentation and post-processing software for quantitative analysis.
- Necessitates cross-team standardization of imaging parameters and data interpretation.
- Adaptable to other murine cerebrovascular models with protocol optimization.
- Limited to preclinical research; direct clinical translation requires further validation.
Biopharma FAQs
Why does null hypothesis testing matter for duplex ultrasound target validation?
Null hypothesis testing enables objective assessment of whether observed changes in intracranial blood flow velocities after SAH are statistically significant, supporting robust target validation in cerebrovascular research.
How does independent variable isolation fit the duplex sonography workflow?
By comparing SAH-induced and sham-operated mice, the protocol isolates the effect of SAH on cerebral blood flow, ensuring that measured changes are attributable to the experimental variable.
What do quantitative dependent variable measurements enable in this protocol?
Quantitative measurements of peak systolic velocity, end diastolic velocity, and velocity time integral provide objective, reproducible endpoints for evaluating vascular responses and therapeutic impact.
Why are replication requirements critical for cross-functional collaboration in vascular imaging?
Replication across multiple animals and time points ensures data reliability, enabling cross-team confidence in findings and facilitating integration into broader R&D workflows.
What statistical analysis capabilities are required before implementing this imaging protocol?
Teams must be able to perform comparative statistical analyses of blood flow velocities and ratios, supporting data-driven decisions and hypothesis testing in preclinical studies.
Chapters in this video
0:00
Introduction
1:54
Blood Flow Velocities of the Intracranial Internal Carotid Arteries
4:25
Blood Flow Velocities of the Extracranial Internal Carotid Arteries
6:37
Processing of the Ultrasonography Data
8:27
Processing of the Ultrasonography Data
8:44
Representative Results
9:54
Conclusion
