MicroRNA-21 and Risk of Severe Acute Kidney Injury and Poor Outcomes after Adult Cardiac Surgery

Background: Severe acute kidney injury (AKI) after cardiac surgery is associated with poor clinical outcomes. This study evaluated the potential use of miR-21 as a risk marker for postoperative AKI progression and other poor outcomes. Methodology/Principal Findings: The study included 120 adult patients undergoing cardiac surgery: 40 non-AKI controls, 39 patients with progressive AKI, and 41 with non-progressive AKI. Urine and plasma levels of miR-21 were assessed by quantitative real-time PCR (RT-qPCR). Associations between miR-21 levels and AKI progression were determined by estimating areas under receiver operating characteristic curves (AUC). We demonstrated that up-regulated urine and plasma levels of miR-21 in patients with AKI were both associated with AKI progression. The AUCs for urine and plasma levels of miR-21 associated with established AKI were 0.68 (95% CI: 0.59-0.78) and 0.80 (95% CI: 0.73-0.88), respectively. Multiple logistic regression analysis, adjusting for clinical variables, indicated that the prognostic predictive power of urine and plasma miR-21 levels for AKI progression were represented by AUCs of 0.81 (95% CI: 0.72-0.91) and 0.83 (95% CI: 0.74-0.92), respectively. Urinary and plasma miR-21 levels also predicted the need for postoperative renal replacement therapy (RRT), development of Acute Kidney Injury Network (AKIN) stage 3 AKI, 30-day in-hospital mortality and prolonged stay in hospital or ICU. Urine miR-21 was a better outcome predictor than plasma miR-21, being associated with higher (1.4- to 2.6-fold) unadjusted odds ratio for progression of AKI and other poor outcomes. Conclusions: Urinary and plasma miR-21 are associated with severe AKI and other poor postoperative outcomes of cardiac surgery, indicating their potential use as prognostic markers.