Methods to Measure Neurodegeneration in Rodent Models

Table of Contents

Abstract

Presentation

01. Introduction 02. Regional Volumes Analysis Methods 03. Cortical Thickness Analysis Methods 04. TDP-43 Model 05. TDP-43 Model MR Images 06. TDP-43 Model MRI Analysis 07. Alpha-Synuclein Model 08. Synuclein Model MR Images 09. Synuclein Model MRI Analysis 10. Summary

Neurodegeneration is a central feature of many rodent models of CNS diseases. The ability to accurately and robustly measure neurodegeneration and its modulation by therapeutic intervention can be a powerful tool in preclinical studies of experimental disease-modifying therapies.

Example methods to measure neurodegeneration in rodent models

Quantitative measures on tissue sections
- Morphological measures
- Immunohistochemistry & immunofluorescence markers
Fluid-based biomarkers
- Neurofilament Light (NfL) in plasma & CSF
Non-invasive imaging
- MRI-derived volume and cortical thickness measures

Quantitative Measures on Tissue Sections

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Manual measurement of cortical thickness on a mouse brain tissue section.

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Counting or density measures based on immunohistochemistry (IHC) stained tissue sections using cell body, dendritic, axonal, and/or synaptic markers. Example of NeuN IHC staining in an alpha-synuclein preformed fibril (PFF) seeding/spreading model of Parkinson's disease demonstrating clear neuronal loss in the ipsilateral piriform cortex of mice injected with PFFs in the anterior olfactory nucleus (AON).

Fluid-based Biomarkers

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Quantitative analysis of neurofilament light (NfL) in the plasma of PBS and PFF inoculated mice measured by the Simoa assay. This example demonstrates highly elevated levels of NfL at 12 and 16 weeks post-inoculation in this model.

Non-invasive Imaging

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Automated measurement of regional brain volumes from anatomical MR images. This example shows segmentation (red) of the piriform cortex in a control mouse (left) compared to an synuclein PFF-injected mouse with significant atrophy of the cortex ipsilateral to the injection site (right).

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There are a variety of methods available to measure neurodegeneration in rodent models. All of these approaches have their pros and cons. The various measures can provide complementary information, and can be used together to provide a comprehensive characterization of neurodegeneration.

Morphometric measures on tissue sections suffer from several limitations, including shrinkage of tissue during fixation & processing, the two-dimensional (2D) nature of the sections, oblique angles of sectioning and differences in anatomy between sections, limited sampling, and manual measurements.

Quantitative immunohistochemistry and immunofluorescence can provide specific insights into the cellular processes contributing to neurodegenerative changes, such as cell loss, reduced dendritic arborization, axonal degeneration, and reduced synaptic density. However, the same limitations mentioned above also apply to these tissue-based measures.

Fluid-based biomarkers, such as neurofilament light levels, can provide highly sensitive measures of neurodegeneration. However, they do not have regional specificity (e.g. hippocampal atrophy). Unlike cross-sectional (terminal) tissue-based measures, fluid-based biomarkers can be measured at multiple in-life time points.

Imaging biomarkers have several advantages, including longitudinal in vivo measurement, three-dimensional (3D) morphometry, and regional localization. While highly sensitive to atrophy, MRI measures are non-specific as to the underlying pathological changes. However, such information can be gleaned via complementary immunohistochemistry or immunofluorescence studies.