The presence of miRNAs in plasma and synovial fluid and their stability for storage. (Upper) Plasma and synovial fluid of RA were stored in --20°C until indicated days, thawed and analyzed for the concentrations of the indicated miRNAs. (Lower) The concentrations of indicated miRNAs in plasma and synovial fluid of RA after indicated freeze-thaw cycles from --20°C to 4°C. Significant differences compared to the concentration after the first freeze-thaw are indicated by * = P < 0.05, ** = P < 0.01. Results represent three independent experiments.