Clinical Safety and Efficacy of Umbilical Cord Mesenchymal Stromal Cells-derived Exosomes in Patients With Parkinson's Disease

The goal of this clinical trial is to learn if intranasal umbilical cord mesenchymal stromal cell-derived exosomes (UCMSC-Exo) are safe and can help treat early Parkinson's disease in adults aged 50-75. It will also learn about the safety and tolerability of UCMSC-Exo. This is a single-center, open-label, dose-escalation study using a 3+3 design; there is no placebo and no blinding. The main questions it aims to answer are: 1. What local and systemic adverse events and serious adverse events occur with intranasal UCMSC-Exo? 2. Does intranasal UCMSC-Exo improve motor and non-motor symptoms, biomarkers, and imaging measures in Parkinson's disease? 3. Researchers will compare low-, medium-, and high-dose UCMSC-Exo groups sequentially to assess safety and preliminary efficacy. Participants will: 1. Receive UCMSC-Exo by nasal spray twice weekly (Monday/Thursday) for 12 weeks (24 administrations) at their assigned dose. 2. Continue their usual dopaminergic medication during the study. 3. Visit the clinic for safety assessments at weeks 4, 12, 16, and 48, and for efficacy assessments at weeks 12, 16, 24, 36, and 48. 4. Undergo blood sampling, symptom questionnaires, and PET-MR imaging at scheduled time points. 5. Be followed for a total of 48 weeks, including the 12-week treatment period and 36 weeks after treatment.

Inclusion Criteria: 1. Confirmed sporadic idiopathic Parkinson's disease according to the UK Brain Bank clinical diagnostic criteria. 2. On dopaminergic therapy for ≥60 days. 3. Hyposmia, defined as SS-16 score \