Background: Circulating microRNAs are potential markers for disease detection. A novel class of small non-coding RNAs called Piwi-interacting RNAs (piRNAs) has been recently reported to participate in the epigenetic regulation of cancers and other diseases. This study aims to discover blood-based piRNAs which can be used as markers for disease detection and monitoring.
Materials and methods: We selected five piRNAs for detection, namely, has-piR-651, has-piR-823, has-piR-36707, has-piR-36741 and has-piR-57125. Serum or plasma samples were used to isolate small RNAs, including the piRNAs. The extracted small RNAs were reverse-transcribed in the presence of a poly-A polymerase with an oligo-dT adaptor, and quantitative real-time PCR (qRT-PCR) was applied to measure the levels of piRNAs. Room-temperature incubation and repetitive freeze-thaw cycles were performed to measure the stability of the piRNAs.
Results: Unlike the four other piRNAs, has-piR-57125 was present in both the serum and plasma samples. Regardless of the serum or plasma samples, qRT-PCR analysis indicated that the Ct values showed no remarkable variation with prolonged incubation time (P > 0.05). We also detected the Ct values of the samples with repetitive freeze-thaw cycles and observed a similar trend (P > 0.05) among the samples with diverse freeze-thaw cycles.
Conclusion: This study is the first to report that piRNAs are stably expressed in human serum or plasma samples. Therefore, piRNAs can serve as valuable blood-based biomarkers for disease detection and monitoring.
Keywords: biomarker; blood; circulating; piRNA; plasma; serum.