Stability of miRNA in human urine supports its biomarker potential

Aim: miRNAs are showing utility as biomarkers in urologic disease, however, a rigorous evaluation of their stability in urine is lacking. Here, we evaluate the stability of miRNAs in urine under clinically relevant storage procedures. Materials & methods: Eight healthy individuals provided clean catch urine samples that were stored at room temperature or at 4 degrees C for 5 days, or subjected to ten freeze-thaw cycles at -80 degrees C. For each condition, two miRNAs, miR-16 and miR-21, were quantitated by quantitative real-time PCR. Results: All conditions demonstrated a surprising degree of stability of miRNAs in the urine: by the end of ten freeze-thaw cycles, 23-37% of the initial amount remained; over the 5-day period of storage at room temperature, 35% of the initial amount remained; and at 4 degrees C, 42-56% of the initial amount remained. Both miRNAs also showed degradation at approximately the same rate. Conclusion: miRNAs are relatively stable in urine under a variety of storage conditions, which supports their utility as urinary biomarkers.