Assessment of Mitochondrial DNA Copy Number in Progressive Supranuclear Palsy Patients: Evidence From a Pilot Study

Background: Progressive supranuclear palsy (PSP) is a rare neurodegenerative tauopathy characterized by early postural instability and vertical gaze palsy. Mitochondrial dysfunctions have been increasingly implicated in the pathogenesis of neurodegenerative disorders, including PSP. We investigated mitochondrial DNA copy number (mtDNA-CN) alterations in the peripheral blood of PSP patients, assessing its potential as a biomarker for disease onset and progression. Methods: We measured mtDNA-CN in a cohort of clinically diagnosed PSP patients and age-matched healthy controls using quantitative real-time PCR. We evaluated differences across clinical phenotypes and age groups. Results: PSP patients exhibited a significant reduction in ND3-CN compared to healthy controls (p < 0.0001). This depletion remained consistent across age groups, suggesting that mitochondrial impairment in PSP is independent of physiological aging. Although not statistically significant, ND3-CN levels were lower in PSP-parkinsonism (PSP-P) patients compared to those with Richardson's syndrome (PSP-RS). Interestingly, in PSP-RS patients, ND3-CN levels tended to increase with age, potentially reflecting an age-related compensatory mitochondrial response to chronic neuroinflammation. Conclusions: Our findings support the involvement of mitochondrial dysfunction in PSP pathogenesis, suggesting that peripheral mtDNA-CN may serve as a non-invasive biomarker for disease monitoring. Further studies in larger cohorts are warranted to validate its prognostic potential in different PSP phenotypes.