Identification of urinary miRNA biomarkers for detecting cisplatin-induced proximal tubular injury in rats

Despite increased focus in recent years on urinary microRNA (miRNA) biomarkers in patients with diabetes and chronic kidney diseases, few studies have explored urinary miRNA markers in drug-induced nephrotoxicity. Here, we attempted to identify urinary miRNA markers suitable for use in detecting cisplatin-induced nephrotoxicity in rats. Cisplatin (6 mg/kg) was given as a single intraperitoneal injection to male Sprague–Dawley (SD) rats, and urine collected from Days 4 to 5 for 17 h under fed or fasted conditions. MiRNAs were identified using TaqMan® Rodent microRNA PCR cards, and rats were euthanized 5 days after administration. Levels of 25 miRNAs were significantly increased in the urine of cisplatin-treated rats under both fed and fasted conditions, while the levels of these miRNAs were decreased in either or both the cortex or outer medulla of the kidney. Analysis of time and dose dependency in the urine from rats treated with cisplatin (1, 3, and 6 mg/kg) on Days 1, 3, and 7, showed levels of 25 miRNAs were increased in urine and their appearance correlated with the severity of necrosis in the proximal tubules. Four miRNAs (let-7g-5p, miR-93-5p, miR-191a-5p and miR-192-5p) in urine were measured by absolute quantification, and a strong correlation was found between relative and absolute quantification methods. In summary, we identified 25 miRNAs in urine that were able to be used as non-invasive biomarkers for the detection of cisplatin-induced proximal tubular injury in rats. This study is the first step in demonstrating the potential utility of urinary miRNAs in assessing nephrotoxicity. Further study, such as collaborative programs currently underway in the HESI consortium, will clarify the usability of identified miRNA markers in measurement of other nephrotoxicants and injury-site specificity.