Serum and Exosomal miR-7-1-5p and miR-223-3p as Possible Biomarkers for Parkinson’s Disease

The etiology of Parkinson’s disease (PD) is poorly understood, and is strongly suspected to include both genetic and environmental factors. In this context, it is essential to investigate possible biomarkers for both prognostic and diagnostic purposes. Several studies reported dysregulated microRNA expression in neurodegenerative disorders, including PD. Using ddPCR, we investigated the concentrations of miR-7-1-5p, miR-499-3p, miR-223-3p and miR-223-5p—miRNAs involved in the α-synuclein pathway and in inflammation—in the serum and serum-isolated exosomes of 45 PD patients and 49 age- and sex-matched healthy controls (HC). While miR-499-3p and miR-223-5p showed no differences (1), serum concentration of miR-7-1-5p was significantly increased (p = 0.0007 vs. HC) and (2) miR-223-3p serum (p = 0.0006) and exosome (p = 0.0002) concentrations were significantly increased. ROC curve analysis showed that miR-223-3p and miR-7-1-5p serum concentration discriminates between PD and HC (p = 0.0001, in both cases). Notably, in PD patients, both miR-223-3p serum (p = 0.0008) and exosome (p = 0.006) concentrations correlated with levodopa equivalent daily dosage (LEDD). Finally, serum α-synuclein was increased in PD patients compared to HC (p = 0.025), and in patients correlated with serum miR-7-1-5p in (p = 0.05). Our results suggest that both miR-7-1-5p and miR-223-3p, distinguishing PD from HC, have the potential to be useful and non-invasive biomarkers in Parkinson’s disease.