An Alternative Approach to Study Primary Events in Neurodegeneration Using Ex Vivo Rat Brain Slices
April 11th, 2018
We present a method which can provide further insights into the early events underlying neurodegeneration and based on the established ex-vivo brain technique, combining the advantages of in vivo and in vitro experiments. Moreover, it represents a unique opportunity for direct comparison of treated and untreated group in the same anatomical plane.
The overall goal of this procedure is to simultaneously investigate two specular hemislices obtained from the same anatomical plane and montior the effects following a treatment. This method can help answer crucial questions in the molecular neuroscience field such as the primary events effecting key molecules involved in neurodegenerative processes. The main advantage of this technique is that it can provide and medium carried out of molecular cascades underlying neurodegenerative events.
Though this method can provide insight into primary events occurring in neurodegeneration, it can also be applied to investigate animal models of different disorders or other organs and tissues properties. Begin with preparing two different artificial cerebrospinal fluids. One used for the brain slicing, and the other for the incubation step.
After preparing the slicing ACSF, mix the solution and keep it on ice. Similarly, prepare the recording ACSF, but keep it at room temperature. Oxygenate both solutions.
Next, prepare the instruments for the decapitation and brain removal at the dissection hood. Then, set up the vibratome parameters. Set the slice thickness as needed.
Such as three hundred microns. Set the frequency at seven and the speed at six. Then, insert the vibratome chamber and surround it with ice.
For the brain sectioning, opening the carbogen valve to oxygenate the slicing ACSF. Select the minimum flow rate of around two milliliters per minute. Now in two 15 milliliters tubes, prepare the tus conditions.
Load one tube with 10 millilieters of the recording ACSF as a control. Load the other with the 10 milliliter of recording ACSF enriched with the treatment. In this case, two micromolar of T30.
Vortex both tubes and keep them on ice until they are needed. Incise the skin over the skull with a surgical blade. Then using scissors, cut the skull along the midline from the posterior to the bone above the olfactory bulbs.
Then, laterally pull on the two sides of the skull using forceps to access the brain. Insert a spatula ventrally to the brain. Gently scoop it out and keep it hydrated in ice cold slicing ACSF for about five minutes.
After the rest in cold ACSF, transfer the brain to a filter paper. And after having removed the cerebellum, glue the brain vertically on the vibratome disc. Then transfer it to the sectioning chamber filled with ice cold slicing ACSF.
Now start the oxygen flow to the chamber solution. Then adjust the cutting interval and proceed with the brain sectioning. Collect the sections containing the region of interest using standard methods.
Now carefully divide each section with small scissors along the midline to obtain two specular hemislices. Use each pair of hemislices for the control and treated condition. After being divided, let the hemisections rest in the vibratome chamber for five to ten minutes.
After the rest, gently transfer the hemisections using a glass pipet into a bubbling pot containing recording ACSF at room temperature. Then let the hemisections recover for about 30 minutes before proceeding. During the break, load three glass vials with three milliliters of recording ACSF for the control group and three vials with three milliliters of ACSF enriched with T30 for the treated group.
After the 30 minute rest, within five minutes, transfer the sample to the baths. First load the consecutive hemislices to the control solution using a brush. Then, using a different brush, transfer the contralateral hemisections to the treatment solution.
Next, seal the vials with plastic stoppers containing 21 gauge needles for the delivery of carbogen to the sample. Deliver oxygen at a minimal flow rate, such as two milliliters per minute to prevent any movement of the brain tissue resulting in possible mechanical damage to the tissue. This completes the setup.
Now start a five hour incubation. After the incubation, stop the oxygen flow and uncap the vials. Then gently transfer the hemislices using the appropriate brush to 1.5 milliliter tubes containing 250 microliters of lysis buffer maintained on ice.
Next using separate pestles, homogenize each tissue. Complete the transfer and homogenization steps within 10 to 15 minutes for all six samples. Now centrifuge the homogenized samples at 1, 000 times gravity for five minutes at four degrees Celsius.
After the spin, transfer the supernatants into new tubes and store the samples at negative 80 degrees Celsius. Administration of a toxic peptide, T30, to the basil fore brain containing hemisections had three site specific effects on the tissue. It modulated the expression of alpha seven nicotinic receptor, the phosphorylation of Tau and the expression of amyloid beta.
The nicotinic receptor showed a significant increase in the rostral treated hemislice, while the intermediate slice did not reveal any change between the two conditions. In the posterior section, a significant reduction was present in the T30 exposed portion. Phosphorylated Tau levels were significantly increased in the anterior region.
On the other hand, the other two basil fore brain sections do not show any significant difference between the conditions. Amyloid beta was significantly enhanced after T30 exposure in the rostral and intermediate hemisections. However, in the codal slide, there was no measurable effect on amyloid beta expression.
Once mastered, this technique can be done within seven hours if properly performed.
View the full transcript and gain access to thousands of scientific videos
Overview
This study presents an ex-vivo brain technique to investigate early neurodegenerative events by using paired hemislices for comparative analysis. The method allows for direct monitoring of treated and untreated conditions within the same anatomical framework, offering insights into key molecular changes associated with neurodegeneration.
Key Study Components
Area of Science
- Neuroscience
- Neurodegeneration
- Cellular and Molecular Biology
Background
- Neurodegenerative processes impact critical signaling pathways in neuronal health.
- Investigating these processes at the molecular level is essential for understanding disease mechanisms.
- Comparative models in the same anatomical structure allow for more precise insights.
Purpose of Study
- To examine the effects of treatment on molecular events associated with neurodegeneration.
- To provide a method that can also be adapted for different animal models or tissue investigations.
- To analyze the primary molecular changes in response to various treatments.
Methods Used
- Ex-vivo brain slices were utilized, focusing on paired hemislices from the same brain for control and treated conditions.
- The study used a toxic peptide, T30, to assess its impact on specific molecular markers in the basal forebrain.
- Key steps included preparing artificial cerebrospinal fluids (ACSF), brain sectioning, incubation, and homogenization for subsequent analysis.
Main Results
- T30 treatment elicited significant changes in the expression of alpha seven nicotinic receptors, tau phosphorylation, and amyloid beta levels across various brain regions.
- Notable increases in phosphorylated tau and amyloid beta levels were observed, highlighting the method’s capacity to reveal critical neurodegenerative mechanisms.
- This approach supports the inference of specific molecular cascades as relevant targets for neurodegenerative research.
Conclusions
- This technique enables simultaneous investigation of neurodegenerative events with direct comparisons, facilitating a deeper understanding of disease mechanisms.
- Findings suggest pathways for further exploration of molecular targets in neurodegeneration and potentially other disorders.
- The insights gained may inform therapeutic strategies and advance the study of neurodegenerative diseases.
Frequently Asked Questions
Executive Industry Relevance
This ex-vivo brain slice method enables direct comparison of treated and untreated tissue from the same anatomical region, supporting mechanistic de-risking in early neurodegeneration target validation. By preserving cytoarchitecture and local functionality, it provides a physiologically relevant system for evaluating molecular responses to toxic peptides or drug candidates. The approach enhances predictive confidence in lead identification by revealing site-specific, dose-dependent, and time-dependent changes in AD-relevant biomarkers.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Interrogates therapeutic hypotheses by measuring differential expression of α7-nAChR, p-Tau, and Aβ across brain subregions.
- Operational Value: Enables paired hemislice controls to reduce biological variability and improve assay sensitivity.
- Strategic Value: Supports target de-risking through spatially resolved biomarker readouts in disease-relevant circuits.
Screening & Assay Development
- Scientific Value: Generates quantitative molecular readouts (receptor expression, phosphorylation, protein levels) for compound screening.
- Operational Value: Uses standardized ACSF perfusion and oxygenation to ensure reproducible slice viability.
- Strategic Value: Facilitates dose-response and time-course assays in a single animal, improving throughput and reducing resource use.
Translational & Preclinical Research
- Scientific Value: Models early AD-like molecular changes in the basal forebrain, a region selectively affected in neurodegeneration.
- Operational Value: Allows multi-region analysis from one brain, increasing data yield per animal.
- Strategic Value: Supports go/no-go decisions by linking target engagement to downstream pathophysiological markers.
Pipeline & Workflow Integration
The method fits within early discovery workflows, bridging target engagement assays to phenotypic screening by providing mechanistic readouts in a disease-relevant neural system.
- Discovery Biology: Supports hypothesis testing of neurodegenerative cascades via spatially resolved biomarker analysis.
- Screening: Enables standardized, reproducible compound testing with quantitative molecular outputs.
- Analytics: Delivers multiplexed readouts (receptor, phospho-protein, amyloid) for comparative condition analysis.
- Translational Research: Connects molecular changes in basal forebrain to AD pathology, supporting preclinical continuity.
- Enterprise Reuse: Reusable across treatment conditions, time points, and brain regions from a single preparation.
Operational & Enterprise Impact
- Scientific Value: Predictive confidence in target validation through mechanistic de-risking of neurodegenerative pathways.
- Operational Value: Standardized tissue preparation and incubation ensure reproducibility across experiments.
- Strategic Value: Reduces late-stage biological risk by identifying ineffective targets early.
- Portfolio Impact: Enables risk-adjusted prioritization of compounds based on target-specific biomarker modulation.
Implementation Considerations
- Expertise in neuroanatomy and vibratory sectioning is required to obtain viable hemislices.
- Instrumentation includes a vibratome, oxygenation system, and temperature-controlled incubation setup.
- Standardization of ACSF composition, slice thickness, and perfusion rates is critical for reproducibility.
- Adaptation to other brain regions or species may require optimization of slicing and recovery parameters.
- Tissue viability limits experimental windows, necessitating timely processing post-sectioning.
