Serum Exosomal miR-223 Serves as a Potential Diagnostic and Prognostic Biomarker for Dementia

The aims of this study were to examine the levels of serum and exosomal miR-137, miR-155 and miR-223, three neuroinflammation-related miRNAs, in dementia patients and to explore the value of these miRNAs for the diagnosis and prognostic evaluation of dementia. Thirty-two patients with dementia were enrolled, and sixteen volunteers without dementia served as controls. Serum exosomes were isolated by precipitation with ExoQuick and characterized by western blotting, nanoparticle-tracking analysis and immunofluorescence microscopy. The levels of both total serum miRNAs and serum exosomal miRNAs were determined by real-time quantitative PCR. Total serum miRNAs and serum exosomal miRNAs were both detected to be down-regulated. The median level of serum exosomal miR-223 was significantly decreased in dementia patients (p < 0.01). The level of miR-223 was significantly correlated with Mini-Mental State Examination (MMSE) scores, Clinical Dementia Rating (CDR) scores, magnetic resonance spectroscopy (MRS) spectral ratios and serum concentrations of IL-1β, IL-6, TNF-α, and CRP. The diagnostic utility of exosomal miR-233 was evaluated by the area under the receiver operating characteristic (ROC) curve, and the area under the curve (AUC) was 0.875. This study suggests that serum exosomal miR-223 is a promising biomarker for diagnosing dementia and evaluating the progression of disease.