title: Detection of stably expressed piRNAs in human blood.
abstract: 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.
  
  
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Urology, The First Affiliated Hospital of Nanjing Medical University Nanjing 210029, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Urology, The First Affiliated Hospital of Nanjing Medical University Nanjing 210029, China.
authors.forename: Yidong
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: Department of Urology, The First Affiliated Hospital of Nanjing Medical University Nanjing 210029, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Lu
authors.affiliation: Clinical Research Centre, The First Affiliated Hospital of Nanjing Medical University Nanjing 210029, China.
authors.forename: Jifu
authors.initials: J
authors.lastname: Wei
authors.affiliation: Department of Urology, The First Affiliated Hospital of Nanjing Medical University Nanjing 210029, China.
authors.forename: Haiwei
authors.initials: H
authors.lastname: Yang
authors.affiliation: Department of Urology, The First Affiliated Hospital of Nanjing Medical University Nanjing 210029, China.
authors.forename: Min
authors.initials: M
authors.lastname: Gu
keywords: biomarker; blood; circulating; piRNA; plasma; serum