Visualizing Leukocyte Rolling and Adhesion in Angiotensin II-Infused Mice: Techniques and Pitfalls
January 4th, 2018
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This manuscript describes the use of transgenic reporter mice and different administration routes of fluorescent dyes in angiotensin II-induced hypertension using intravital video microscopy of blood vessels to evaluate the activation of immune cells and their ability to roll and adhere to the endothelium.
Overview
This study utilizes intravital video microscopy to visualize leukocyte interactions in corroded arteries of mice with Angiotensin II-induced hypertension. The methodology allows for real-time observation of immune cell behavior in vivo, providing insights into vascular dysfunction.
Key Study Components
Area of Science
- Neuroscience
- Vascular Biology
- Immunology
Background
- Angiotensin II is known to induce hypertension and vascular dysfunction.
- Leukocyte rolling and adhesion are critical processes in inflammation and vascular pathology.
- Intravital video microscopy (IVM) allows for the observation of these processes in real-time.
- Transgenic reporter mice provide a model for studying immune cell behavior.
Purpose of Study
- To visualize and quantify leukocyte rolling and adhesion in a model of hypertension.
- To investigate the interactions between leukocytes and the endothelium in vivo.
- To enhance understanding of the mechanisms underlying vascular dysfunction.
Methods Used
- Preparation of male mice with Angiotensin II treatment.
- Surgical isolation of the jugular vein and corroded arteries.
- Injection of fluorescent dyes for visualization of leukocyte behavior.
- Real-time imaging using high-speed fluorescence microscopy.
Main Results
- Leukocyte adhesion was observed in the corroded arteries of treated mice.
- Fluorescent imaging revealed interactions between leukocytes and endothelial cells.
- Quantification of rolling and adhering cells provided insights into inflammatory processes.
- Control experiments confirmed the specificity of the observed interactions.
Conclusions
- The study demonstrates the utility of IVM in examining leukocyte dynamics in hypertension.
- Findings contribute to understanding the role of immune cells in vascular diseases.
- This methodology can be applied to further investigate other vascular pathologies.
Frequently Asked Questions
What is the significance of using transgenic mice in this study?
Transgenic mice allow for specific labeling of immune cells, facilitating the visualization of their interactions with the endothelium.
How does intravital video microscopy enhance our understanding of vascular dysfunction?
IVM provides real-time imaging of leukocyte behavior in vivo, revealing dynamic processes that contribute to vascular pathology.
What role does Angiotensin II play in this research?
Angiotensin II is used to induce hypertension in the mouse model, allowing researchers to study its effects on leukocyte-endothelial interactions.
What are the main advantages of the IVM technique?
IVM allows for direct observation of cellular interactions in their natural environment, providing insights that are not possible with traditional methods.
How are leukocyte rolling and adhesion quantified in this study?
Quantification is achieved by counting the number of rolling and adhering cells within a defined area during video recordings.
What implications do the findings have for future research?
The findings may inform therapeutic strategies targeting immune cell interactions in vascular diseases.
Executive Industry Relevance
This method enables direct visualization of leukocyte-endothelial interactions in vivo, providing mechanistic insights into vascular inflammation relevant to hypertension therapeutics. By quantifying rolling and adhesion of immune cells, it supports target validation and de-risking of anti-inflammatory strategies in preclinical discovery. The approach highlights the importance of minimizing procedural artifacts to ensure data fidelity in translational research.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of leukocyte-endothelial interaction mechanisms in disease-relevant models.
- Operational Value: Provides quantitative readouts of cellular dynamics for hypothesis testing.
- Predictive Value: Supports assessment of target modulation on inflammatory cell recruitment.
Screening & Assay Development
- Scientific Value: Establishes standardized conditions for evaluating compound effects on leukocyte behavior.
- Operational Value: Facilitates reproducible imaging protocols across experimental groups.
- Assay Readiness: Enables real-time monitoring of pharmacological interventions in vivo.
Translational & Preclinical Research
- Scientific Value: Links immune cell activation to vascular pathology in a hypertensive model.
- Operational Value: Supports longitudinal assessment of treatment effects on endothelial interactions.
- Translational Continuity: Provides a platform for validating findings across disease models.
Pipeline & Workflow Integration
The technique fits within the discovery continuum from target validation through preclinical efficacy assessment, particularly for immunomodulatory candidates.
- Discovery Biology: Enables direct observation of leukocyte recruitment mechanisms in hypertension models.
- Screening: Supports evaluation of compound effects on immune cell-endothelial interactions.
- Analytics: Generates quantitative data on rolling and adhesion frequencies for comparative analysis.
- Translational Research: Connects immune cell behavior to vascular dysfunction outcomes.
- Enterprise Reuse: Establishes a reusable platform for studying leukocyte dynamics across cardiovascular indications.
Operational & Enterprise Impact
- Scientific Value: Reduces mechanistic ambiguity in leukocyte-mediated vascular pathology.
- Operational Value: Standardizes intravital imaging procedures for cross-study comparability.
- Strategic Value: Informs go/no-go decisions by clarifying target engagement in inflammatory pathways.
- Portfolio Impact: Enables risk-adjusted prioritization of immunomodulatory candidates based on functional validation.
Implementation Considerations
- Requires expertise in microsurgical techniques and intravital microscopy.
- Depends on specialized equipment including high-speed fluorescence microscopy and temperature control.
- Necessitates standardization of injection protocols to avoid confounding surgical artifacts.
- Involves adaptation considerations when translating across different mouse strains or disease models.
- Involves practical limitations related to vessel accessibility and imaging depth in certain vascular beds.
Biopharma FAQs
Why does jugular catheter implantation affect leukocyte rolling and adhesion measurements?
Jugular catheter implantation alone increases rolling and adhesion of LysM+ cells in sham-infused mice, indicating surgical artifact that must be controlled for in experimental design.
How does tail vein injection of acridine orange compare to jugular catheter delivery for leukocyte visualization?
Tail vein injection of acridine orange does not increase leukocyte adhesion or rolling in sham-infused mice, making it a less invasive alternative that avoids confounding surgical effects.
What quantitative measurements enable assessment of leukocyte-endothelial interactions in this model?
Rolling and adhering cells are quantified in a 200 micron by 250 micron rectangle view of the vessel, with adherence defined as cells not detaching within a 10-second video.
Why are replication requirements important for validating leukocyte interaction data across experimental groups?
Replication across multiple locations on the artery and conditional dye injection ensures that observed changes are due to biological effects rather than procedural variability or imaging artifacts.
What statistical analysis capabilities are required to distinguish true leukocyte activation from procedural artifacts?
Analysis must compare leukocyte rolling and adhesion across conditions including sham, AngII-infused, catheter-only, and dye-injection groups to isolate treatment-specific effects from surgical confounds.
