Cell-specific mitochondrial response in progressive supranuclear palsy

Abstract

Progressive supranuclear palsy (PSP) is a main form of idiopathic tauopathy characterized neuropathologically by subcortical neurofibrillary tangles in neurons, oligodendroglial coiled bodies, and tufted astrocytes, which follow sequential distribution in the human brain. Mitochondrial dysfunction is thought to be a contributor to many neurodegenerative diseases, but its role in PSP at the cellular level remains incompletely understood. To address this, we performed cell-specific morphometric analysis of mitochondrial markers in post-mortem tissues from motor cortex of PSP patients and non-diseased controls (n = 5 each) followed by single-nuclear transcriptomics (n = 3 each) to identify changes in genes that regulate mitochondrial function. We treated iCell astrocytes with PSP brain homogenates and isolated viable astrocytes from multiple regions of PSP-affected brains. We found that PSP is characterized by significant mitochondrial changes in neurons and astrocytes at the immunohistochemical level, particularly in complex I, with distinct transcriptomic responses across cell types. Glial cells exhibited upregulation of pathways associated with mitochondrial function. In contrast, excitatory and inhibitory neurons showed downregulation in these pathways, indicating impaired mitochondrial function. Astrocytes derived from different human brain regions express varied levels of GFAP and EAAT1 immunoreactivity. Astrocytic tau pathology in cell culture derived from postmortem PSP brains mirrors that seen in corresponding brain tissue histology. Tau pathology in human astrocyte cell culture is associated with clumps of mitochondria potentially associated with impairment in their neuron supportive function. Our results underscore selective complex I damage and cell-type specific patterns that differentiate PSP from other neurodegenerative diseases.