A Deep Dive into Demyelination and Remyelination Using Spatial Transcriptomics in Multiple Sclerosis
Multiple sclerosis (MS) is a complex immune-mediated neurodegenerative disease impacting millions worldwide, characterized by demyelination, neurodegeneration, inflammation, and glial reactions within the central nervous system (CNS). While current therapies can manage acute inflammation, the progressive nature of MS often leads to increased disability, highlighting the urgent need to understand the underlying mechanisms at a cellular and molecular level. Animal models, like the cuprizone (CPZ) model, play a crucial role in this endeavor by mimicking demyelination and allowing for the testing of potential remyelination therapies.
The Cuprizone Model: A Window into MS Pathology
The CPZ model utilizes a copper chelator, cuprizone, to induce mitochondrial stress in mature oligodendrocytes (MOLs), leading to a predictable demyelination pattern, especially in the corpus callosum (CC). This model is valuable because it mirrors early-stage MS lesions where damage and repair occur simultaneously. Researchers traditionally use methods like histological staining and immunohistochemistry (IHC) to characterize the CNS phenotypes in the CPZ model. However, these approaches have limitations, as they can only examine a few selected markers, failing to capture the complete cellular and molecular response.
Spatial Transcriptomics: Revolutionizing Our Understanding of MS
To overcome these limitations, a recent study integrated single-cell and spatial transcriptomics (ST) to map the spatial cellular and molecular responses during de- and remyelination in the CPZ model. ST technology enables high-throughput investigations of spatially resolved transcripts, offering a superior tool for investigating the detailed cellular and molecular substrates underlying MS lesion evolution compared to traditional methods like manual dissection.
Key Findings
* Global Demyelination and Neuroinflammation: ST revealed that demyelination and neuroinflammation extend beyond the corpus callosum, displaying region-specific differences. This suggests that MS pathology is more widespread than previously thought.
* Oligodendroglia and Microglia as Major Players: The study identified oligodendroglia and microglia as the primary cell types exhibiting significant transcriptomic changes in the CPZ model. During remyelination, mature oligodendrocytes nearly reversed their phenotype to a control state, while microglia remained associated with the demyelination phenotype.
* Cell-Cell Interactions: Ligand-receptor pairing analyses predicted the enrichment of growth factor and phagocytic pathways during demyelination, aligning with changes observed in MS lesions. These interactions, particularly those involving microglia, may offer protective functions alongside pro-inflammatory ones under CPZ conditions.
* Astrocytes and MS Lesions: Astrocytes in the CPZ model showed the greatest preservation of disease-associated modules to MS lesions, suggesting the CPZ model has moderate translatability to chronically active MS lesions.
Dissecting the Results: A Closer Look
Spatial Mapping of Gene Expression
The researchers began by validating their ST data, confirming that the expression patterns of key genes (Mbp, Cd68, and Gfap) were consistent between Visium spatial maps and IHC staining. Using the SpaGCN package, they identified 17 spatial clusters closely resembling known anatomical regions, demonstrating the accuracy and reliability of their ST approach.
Identifying CPZ-Associated Cell Types
To resolve cell types at each ST spot, the team performed single-nucleus RNA-seq (snRNA-seq) on samples from the cortex, CC, and hippocampus. By integrating bulk and single-cell data using the Scissor package, they identified cell populations associated with experimental phenotypes without relying on subjective clustering methods. This analysis revealed that a high percentage of microglial cells contributed to the CPZ phenotype, while myelin-forming oligodendrocytes were negatively associated with it.
Uncovering Cell-Cell Communication Pathways
Using CellChat, the researchers uncovered novel enriched ligand-receptor (LR) pairs, focusing on significantly altered interactions in the CPZ condition. They identified enhanced phagocytosis, growth factor, and chemokine pathways in microglia, highlighting the complex interplay between these cells and their environment. SpaTalk was then used to infer spatially resolved cell–cell interactions from the deconvoluted Visium data, focusing on interactions among microglia, astrocytes, MOLs, and OPCs.
Assessing Translatability to Human MS
Finally, the study assessed the translatability of the CPZ model to human MS by integrating their data with a published MS RNA-seq dataset representing chronic active lesions. Using hdWGCNA, they defined disease-associated modules that were both correlated with the disease state and preserved between the two species. Astrocytes showed the highest preservation scores, while MOL, OPC, and microglia exhibited moderate to low preservation.
Implications and Future Directions
This study provides a comprehensive spatial-temporal characterization of the CPZ model, offering valuable insights into the biological processes underlying de- and remyelination in MS. By integrating ST with snRNA-seq and other bioanalytical tools, the researchers identified key cell types, pathways, and cell-cell interactions involved in MS pathology.
While the study has some limitations, such as the lack of single-cell resolution in the 10X Visium technology and the potential for direct CPZ effects on cells unrelated to demyelination, it represents a significant advancement in our understanding of MS. Future research should focus on:
* Functionally validating the identified ligand-receptor pairs to determine their therapeutic potential.
* Investigating the functional normalization of MOLs during remyelination.
* Profiling phagocytic proteins in MS CSF to correlate them with disease severity and progression.
* Comparing different MS lesion types to further refine the translatability of the CPZ model to MS pathology.
By continuing to explore the complexities of MS using advanced technologies like spatial transcriptomics, we can pave the way for the development of more effective therapies to combat this devastating disease.
Disclaimer: This blog post is based on the provided research article and is intended for informational purposes only. It is not intended to provide medical advice. Please consult with a healthcare professional for any health concerns.
References:
Tsai, H. H., Piya, S., Wang, J., Zhu, J., Hu, W., Gehrke, A. R., ... & Zhang, B. (2025). Spatial transcriptomics reveals heterogeneous cell‒cell interactions among brain regions in a cuprizone model consistent with multiple sclerosis lesions. bioRxiv, 2025-02.
