A PEG-based method for the isolation of urinary exosomes and its application in renal fibrosis diagnostics using cargo miR-29c and miR-21 analysis.

PURPOSE: To assess a new and highly specific, but low-cost, easily performed and suitable for large-scale applications method for renal fibrosis (RF) diagnostics.

METHODS: Thirty-five RF and twenty non-RF patients were enrolled in the study. An appropriate polyethylene glycol (PEG) was used to isolate urinary exosomes. The efficiency of isolation process was evaluated by the morphology and size observation, as well as the detection of specific markers (CD63, CD9). The expression level of exosomal miR-29c, miR-21 and the endogenous control snRNA-U6 were detected by qRT-PCR. The diagnostic potency of urinary exosomal miR-29c and miR-21 was estimated by the ROC method. Spearman's rank-order correlations analysis was used to assess the correlation between the miRNAs and clinical parameters, including pathological index.

RESULTS: PEG-based method for isolation urinary exosome was effective and could be completed with a relatively low-speed centrifugal machine. Exosomal miR-29c and miR-21 were detected in all samples. The analysis of miRNAs in urinary exosomes revealed significant dys-regulation of miR-29c and miR-21 associated with RF. Exosomal miR-29c and miR-21 could predict degree of RF with AUC of 0.8333 and 0.7639 (P < 0.05). Correlation analysis showed that the level of miR-29c had a significant negative relationship with eGFR and the interstitial relative area.

CONCLUSIONS: The PEG-based method for isolation urinary exosome is an inexpensive and easily performed approach. The application for cargo miRNA analysis is feasible. Urinary exosomal miR-29c may present a promising diagnostic approach.