A Rapid Approach to High-Resolution Fluorescence Imaging in Semi-Thick Brain Slices
July 26th, 2011
Here we describe a rapid and simple method to image fluorescently labeled cells in semi-thick brain slices. By fixing, slicing, and optically clearing brain tissue we describe how standard epifluorescent or confocal imaging can be used to visualize individual cells and neuronal networks within intact nervous tissue.
The overall goal of this procedure is to more easily visualize fluorescent neurons within thick brain slices. This is accomplished by first embedding the brain in an aeros plug holder. The second step of the procedure is to section the brain into thick slices on the compressed tome.
The third step of the procedure is to optically clear the brain slices in a glycerol gradient. The final step of the procedure is to mount the cleared brain slices onto slides for fluorescent imaging. Ultimately, results can be obtained that show high resolution fluorescent protein reporter expression in neurons within thick brain slices, through epi fluorescent or confocal microscopy.
The main advantage of this technique over existing methods like thin section, serial fluorescent microscopy or multi photon imaging, is that it is much more rapid, less labor intensive and does not require expensive or sophisticated microscopy technique. To begin retrieve the mouse brain tissue that has undergone NC two fixation by cardiac perfusion and has been postfix for one to two hours at four degrees Celsius. Next, make a 2%high strength low gel point agro solution in PBS and heat in the microwave until dissolved.
Transfer the molten agros to a test tube and place an a 40 degree Celsius heat block to equilibrate the temperature while the agros equilibrates glue the fixed brain tissue onto the plunger of the specimen syringe. With Sano Aate glue submersed the mounted tissue in a saturated sucrose PBS solution to coat the brain surface and then draw down the plunger into the plunger housing. Pipette the warm aros into the plunger, completely covering the brain tissue while making sure not to introduce any air bubbles.
Finally, clamp the specimen syringe with a cold chilling block for about one minute. To set the aros, assemble the specimen syringe containing the embedded brain tissue into the compressed home. Align the edge of the blade closely with the outlet of the specimen syringe, and then fill the buffer tank with PBS.
Rotate the micrometer. Once slice thickness forward to extrude the embedded brain tissue out of the specimen syringe. To generate the first slice, press the start button on the control unit.
Repeat the process of advancing the embedded tissue and pressing the start button to generate the desired number of slices. Collect the slices with a transfer pipette and transfer them to a glass inhalation vial filled with PBS pipette off most of the PBS from the collected slices and replace with a 10%glycerol in PBS solution. Rock the vial gently at four degrees Celsius on a tabletop rotating shaker until the slices sink.
Continue the gradual clearing by repeating the decanting and refilling process with 25 50 and then 75%glycerol solutions. Pipette off the 75%glycerol solution and replace with 90%glycerol. Being careful not to introduce any bubbles and equilibrate at four degrees Celsius with gentle rocking.
Now that the slices have been maximally cleared, they will no longer sink, but will instead show neutral buoyancy. Cut double-sided adhesive into an open rectangle with a two to three millimeter border to fit the viewable area of a 25 by 75 millimeter microscope Slide using a pair of forceps. Arrange the brain slices within the border on the slide.
Gently lower the cover glass onto the adhesive tape. Being careful not to introduce air bubbles and apply pressure to create a seal aspirate any excess glycerol, and then seal the edges of the cover slip by applying clear nail polish. Once the seal has dried, the slide can be stored in a slide box at four degrees Celsius or imaged.
Immediately use using epi fluorescent microscopy. The expression pattern of a viral vector expressing enhanced GFP can be seen in a 200 micrometer thick coronal section of mouse brain tissue. Here, the highlighted area of the epi fluorescent image is shown at high resolution using confocal microscopy to reveal individual layer five cortical neurons.
After watching this video, you should have a good understanding of how to prepare fixed to thick brain slices for rapid and high resolution fluorescent imaging.
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Overview
This article presents a method for imaging fluorescently labeled neurons in semi-thick brain slices. The technique involves fixing, slicing, and optically clearing brain tissue to enable visualization of individual cells and neuronal networks using standard imaging methods.
Key Study Components
Area of Science
- Neuroscience
- Cell Biology
- Imaging Techniques
Background
- Fluorescent imaging is crucial for studying neuronal structures.
- Thick brain slices pose challenges for visualization.
- Optical clearing techniques enhance imaging quality.
- Standard microscopy methods can be applied to cleared tissues.
Purpose of Study
- To simplify the visualization of fluorescent neurons in thick brain slices.
- To demonstrate a method that allows for high-resolution imaging.
- To provide a protocol that can be easily replicated in research settings.
Methods Used
- Embedding brain tissue in an aeros plug holder.
- Sectioning the brain into thick slices using a compressed tome.
- Optically clearing slices in a glycerol gradient.
- Mounting cleared slices onto slides for imaging.
Main Results
- High-resolution images of fluorescent protein expression in neurons.
- Successful visualization of neuronal networks within thick slices.
- Compatibility with both epifluorescent and confocal microscopy.
- Demonstration of the effectiveness of the imaging technique.
Conclusions
- The method provides a rapid and effective way to visualize neurons.
- It enhances the ability to study neuronal networks in intact tissue.
- This approach can be beneficial for various neuroscience research applications.
Frequently Asked Questions
Executive Industry Relevance
High-resolution fluorescence imaging in semi-thick brain slices enables rapid, scalable interrogation of neuronal architecture and molecular labeling in intact tissue. This approach addresses the bottleneck of labor-intensive thin-sectioning and cost-prohibitive multiphoton imaging, supporting efficient target validation and mechanistic de-risking in neurobiology-focused discovery pipelines. The method's compatibility with standard microscopy platforms enhances translational continuity and portfolio flexibility for CNS drug discovery programs.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables direct visualization of genetically or virally labeled neuronal populations in situ.
- Supports functional target validation by mapping neuronal connectivity and molecular expression patterns.
- Facilitates rapid hypothesis testing regarding neuronal subtypes and circuit engagement.
- Reduces ambiguity in pathway assignment by preserving tissue context and three-dimensional relationships.
Screening & Assay Development
- Provides reproducible preparation of semi-thick brain slices for downstream imaging assays.
- Delivers quantitative, high-resolution readouts of fluorescent reporter expression in intact tissue.
- Streamlines assay standardization and scalability by minimizing manual sectioning steps.
- Enables reliable evaluation of compound effects on neuronal structure and labeling in preclinical models.
Translational & Preclinical Research
- Aligns imaging outputs with disease-relevant brain regions and neuronal subtypes.
- Maintains tissue integrity for translational biomarker studies and preclinical validation.
- Supports risk-adjusted advancement by providing robust, interpretable imaging data across models.
- Facilitates continuity from discovery through preclinical assessment of CNS-targeted interventions.
Pipeline & Workflow Integration
This method integrates into the discovery-to-preclinical continuum by enabling rapid, high-content imaging of neuronal populations in genetically modified or virally transduced rodent models.
- Discovery Biology: Accelerates hypothesis testing and pathway mapping in intact brain tissue.
- Screening: Delivers standardized, quantitative imaging outputs suitable for comparative analysis.
- Analytics: Supports statistical evaluation of reporter expression and neuronal distribution across experimental conditions.
- Translational Research: Bridges discovery findings to preclinical validation in disease-relevant systems.
- Enterprise Reuse: Offers a scalable, reproducible workflow adaptable to diverse CNS research programs.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence in neuronal target engagement and circuit mapping.
- Operational Value: Reduces labor, cost, and technical barriers associated with traditional imaging approaches.
- Strategic Value: Enables faster go/no-go decisions and efficient resource allocation in CNS portfolios.
- Portfolio Impact: Supports risk-adjusted prioritization of neurobiological targets and mechanisms.
Implementation Considerations
- Requires expertise in rodent brain dissection, tissue embedding, and fluorescence microscopy.
- Needs access to vibratome or Compresstome instrumentation and optical clearing reagents.
- Demands cross-team standardization of tissue preparation and imaging protocols.
- Adaptable to various fluorescent reporters and brain regions with appropriate labeling strategies.
- Limited by tissue opacity and autofluorescence in extremely thick or uncleared samples.
Biopharma FAQs
Chapters in this video
0:05
Title
1:01
Agarose Embedding of Fixed Mouse Brain Tissue
1:55
Sectioning the Embedded Brain Tissue Using the Compresstome
2:33
Optical Clearing of the Brain Tissue Sections
3:14
Mounting the Brain Tissue Sections for Imaging
3:53
Epifluorescent and Confocal Microscopy of Intact Thick Brain Slices
4:16
Conclusion
