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Updated: Jun 26, 2025
Assessing Iron Deposition in the Brains of 5xFAD Mice by Perls'/DAB Staining
Published on: May 23, 2025
Cellular iron deposition patterns predict clinical subtypes of multiple system atrophy
Seojin Lee1, Ivan Martinez-Valbuena2, Anthony E Lang3
1Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Ontario M5T 0S8, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
Background:
Multiple system atrophy (MSA) is a primary oligodendroglial synucleinopathy, characterized by elevated iron burden in early-affected subcortical nuclei. Although neurotoxic effects of brain iron deposition and its relationship with α-synuclein pathology have been demonstrated, the exact role of iron dysregulation in MSA pathogenesis is unknown. Therefore, advancing the understanding of iron dysregulation at the cellular level is critical, especially in relation to α-synuclein cytopathology.
Methods:
Iron burden in subcortical and brainstem regions were histologically mapped in human post-mortem brains of 4 MSA-parkinsonian (MSA-P), 4 MSA-cerebellar (MSA-C), and 1 MSA case with both parkinsonian and cerebellar features. We then performed the first cell type-specific evaluation of pathological iron deposition in α-synuclein-affected and -unaffected cells of the globus pallidus, putamen, and the substantia nigra, regions of highest iron concentration, using a combination of iron staining with immunolabelling. Selective regional and cellular vulnerability patterns of iron deposition were compared between disease subtypes. In 7 MSA cases, expression of key iron- and closely related oxygen-homeostatic genes were examined.
Results:
MSA-P and MSA-C showed different patterns of regional iron burden across the pathology-related systems. We identified subcortical microglia to predominantly accumulate iron, which was more distinct in MSA-P. MSA-C showed relatively heterogenous iron accumulation, with greater or similar deposition in astroglia. Iron deposition was also found outside cellular bodies. Cellular iron burden associated with oligodendrocytic, and not neuronal, α-synuclein cytopathology. Gene expression analysis revealed dysregulation of oxygen homeostatic genes, rather than of cellular iron. Importantly, hierarchal cluster analysis revealed the pattern of cellular vulnerability to iron accumulation, distinctly to α-synuclein pathology load in the subtype-related systems, to distinguish MSA subtypes.
Conclusions:
Our comprehensive evaluation of iron deposition in MSA brains identified distinct regional, and for the first time, cellular distribution of iron deposition in MSA-P and MSA-C and revealed cellular vulnerability patterns to iron deposition as a novel neuropathological characteristic that predicts MSA clinical subtypes. Our findings suggest distinct iron-related pathomechanisms in MSA clinical subtypes that are therefore not a consequence of a uniform down-stream pathway to α-synuclein pathology, and inform current efforts in iron chelation therapies at the disease and cellular-specific levels.
Insights
Multiple system atrophy (MSA) involves iron buildup in specific brain cells, differing between MSA subtypes. This cellular iron vulnerability pattern helps distinguish MSA-P and MSA-C, informing targeted therapies.
Area of Science:
- Neuroscience
- Neuropathology
- Iron Metabolism
Background:
- Multiple system atrophy (MSA) is a neurodegenerative disease linked to iron accumulation in the brain.
- The precise role of iron dysregulation in MSA pathogenesis and its relation to alpha-synuclein pathology remain unclear.
- Understanding iron dysregulation at a cellular level is crucial for deciphering MSA.
Purpose of the Study:
- To map iron burden in subcortical and brainstem regions in human MSA brains.
- To conduct the first cell type-specific evaluation of pathological iron deposition in MSA.
- To compare iron deposition patterns between MSA subtypes (MSA-P and MSA-C).
Main Methods:
- Histological mapping of iron burden in post-mortem brains from MSA patients.
- Cell type-specific iron evaluation using iron staining and immunolabelling in key brain regions.
- Analysis of gene expression for iron- and oxygen-homeostatic genes in MSA cases.
Main Results:
- Distinct regional iron burden patterns were observed between MSA-P and MSA-C subtypes.
- Subcortical microglia predominantly accumulated iron, particularly in MSA-P; astroglia showed more heterogeneous accumulation in MSA-C.
- Cellular iron burden was associated with oligodendroglial, not neuronal, alpha-synuclein pathology; gene expression revealed oxygen homeostasis dysregulation.
Conclusions:
- Distinct regional and cellular iron distribution patterns were identified in MSA-P and MSA-C.
- Cellular vulnerability to iron deposition serves as a novel neuropathological characteristic predicting MSA clinical subtypes.
- Findings suggest distinct iron-related pathomechanisms in MSA subtypes, informing targeted iron chelation therapies.
