Liquid biopsy biomarkers of renal interstitial fibrosis based on urinary exosome

Renal interstitial fibrosis (RIF) is difficult to diagnose. This paper explored liquid biopsy markers in urinary exosomes derived from RIF patients. Urine samples from 32 patients with various degrees of RIF and 20 non-RIF patients were collected. The size and morphology of urinary exosomes isolated by polyethylene glycol were observed with electron microscopy. Protein biomakers of exosomes were analyzed by Western blot. qRT-PCR was used to detect the levels of biomarkers (miR-29c, miR-21, E-cadherin, and vimentin) of epithelial mesenchymal transition in urinary exosomes. The diagnostic value was detected with ROC curves. Results displayed successfully isolated urinary exosomes. The examined miRNAs and mRNAs were checked from all urinary exosomes samples, except for two cases of RIF which lacked E-cadherin mRNA. RNA levels were different in patients with diverse degrees of RIF. Urinary miR-29c was decreased with the progress of fibrosis. Levels of E-cadherin mRNA were first decreased and then increased. The contents of miR-21 and vimentin mRNA were also depended on the degrees of RIF. ROC curve analysis showed that the area under the curve (AUC) of miR-29c was 0.8621, statistically significant compared with the non-RIF group (P < 0.05). The miR-29c level within the urinary exosomes is a promising marker for the diagnosis of RIF.