BACKGROUND: Early and specific detection of cancer is of great importance for successful treatment of the disease. New biomarkers, like microRNAs, could improve treatment efficiency and survival ratio. In human medicine, deregulation of microRNA profiles in circulation has shown great potential as a new type of biomarker for cancer diagnostics. There are, however, few studies of circulating microRNAs in dogs. Extracellular circulating microRNAs have shown a high level of stability in human blood and other body fluids. Nevertheless, there are still important issues to be solved before microRNA can be applied routinely as a clinical tool, one of them being their stability over time in media commonly used for blood sampling.

OBJECTIVE: Evaluation of the stability of microRNA levels in plasma and serum from healthy dogs after storage at room temperature for different time points before being processed.

METHODS: The levels of four microRNAs (cfa-let-7a, cfa-miR-16, cfa-miR-23a and cfa-miR-26a) known to be stably expressed from other canine studies, have been measured by real-time quantitative PCR.

RESULTS: MicroRNA levels were found sufficiently stable for gene profiling in serum- and plasma stored at room temperature for one-hour but not for samples stored at room temperature for 24-hours.

CONCLUSION: Storage at room temperature of serum and plasma samples intended for microRNA profiling should be kept for a minimum period of time before proceeding with RNA isolation. For the four microRNAs investigated in the present study, we did not find significant differences in microRNA levels between serum and plasma samples from the same time point.