Distinct microRNA signatures define sporadic PSP-RS and PD in patient-derived midbrain organoids

Progressive Supranuclear Palsy–Richardson Syndrome (PSP-RS) is a rare, rapidly progressive neurodegenerative tauopathy frequently misdiagnosed as Parkinson's Disease (PD) due to overlapping clinical features. The lack of reliable molecular biomarkers for early and differential diagnosis presents a major clinical challenge. To address this, we developed human midbrain organoids from induced pluripotent stem cells (iPSCs) derived from patients with sporadic PSP-RS, PD, and healthy controls (HCs), and profiled microRNA (miRNA) expression dynamics using small RNA sequencing. These 3D organoid models faithfully recapitulate key pathological hallmarks, including tau hyperphosphorylation in PSP-RS and Lewy body–like a-synuclein inclusions in PD. Our analysis revealed temporally dynamic, disease-specific miRNA signatures: miR-5683, miR-873-5p, miR-219b-5p, and miR-219a-2- 3p were selectively upregulated in PSP-RS, whereas PD organoids showed increased levels of miR-1-3p, miR-133b, miR-10b-5p, and miR-199a-5p. Additionally, miR-5683, miR-3085- 3p, miR-138-2-3p, and miR-124-3p emerged as key discriminators between PSP-RS and HCs. These findings highlight the utility of iPSC-derived midbrain organoids as a translationally relevant platform to uncover disease-specific regulatory networks and identify candidate miRNA biomarkers for atypical parkinsonian syndromes. Overall design: small RNAseq was carried out to characterize dynamic changes in miRNA expression at 60, 90, and 120 days. The samples are from iPSCs-derived midbrain organoids in three conditions: sporadic Progressive Supranuclear Palsy–Richardson Syndrome (PSP-RS), parkinson disease (PD), and healthy controls (HCs). Three replicates per condition for each time point (60,90,120d) are present (total of 27).