The clinical significance of circulating microRNA-21 in patients with IgA nephropathy

Background: Urinary microRNA-21 (miR-21) has been reported to correlate with the histologic lesions of IgA nephropathy (IgAN). We investigated whether urinary or circulating miR-21 could serve as a biomarker for detecting the renal progression of IgAN. Methods: Forty patients with biopsy-proven IgAN were enrolled in this study. Serum and urinary sediment miRs were extracted, and the expression of miR-21 was quantified by real-time quantitative polymerase chain reaction. Renal progression was defined as end-stage renal disease, a sustained doubling of serum creatinine, or a 50% decrease in estimated glomerular filtration rate (eGFR) from baseline. Results: Six patients experienced renal progression during the follow-up period. The baseline eGFR was lower in the progression group (49±11 mL/min/1.73 m 2 vs. 90±23 mL/min/1.73 m 2 , p <0.05) than in the non-progression group. The level of circulating miR-21 on kidney biopsy was higher in the progression group than in the non-progression group (40.0±0.6 vs. 38.2±1.1 ΔCt value of miR-21, p <0.01), whereas there was no significant difference in urinary miR-21 (38.1±2.1 vs. 37.8±1.4 ΔCt value of miR-21, p =0.687) between the two groups. Receiver operating characteristic curve analysis demonstrated that circulating miR-21 had good discrimina-tive power for diagnosing renal progression of IgAN, with an area under the curve of 0.975. Conclusions: The level of circulating miR-21 was higher in the progression group than in the non-progression group at the time of kidney biopsy. Therefore, circulating miR-21 could be a surrogate marker of renal progression in patients with IgAN.