title: Characterization of RNA in saliva.
abstract: BACKGROUND
  We have previously shown that human mRNAs are present in saliva and can be used as biomarkers of oral cancer. In this study, we analyzed the integrity, sources, and stability of salivary RNA.
  
  
  METHODS
  We measured the integrity of salivary RNA with reverse transcription followed by PCR (RT-PCR) or RT-quantitative PCR (RT-qPCR). To study RNA entry sites into the oral cavity, we used RT-PCR analysis of salivary RNA from the 3 major salivary glands, gingival crevice fluid, and desquamated oral epithelial cells. We measured stability of the salivary beta-actin mRNA by RT-qPCR of salivary RNA incubated at room temperature for different periods of time. We measured RNA association with other macromolecules by filtering saliva through pores of different sizes before performing RT-qPCR. To assess RNA-macromolecule interaction, we incubated saliva with Triton X-100 for different periods of time before performing RT-qPCR.
  
  
  RESULTS
  In most cases, we detected partial- to full-length salivary mRNAs and smaller amounts of middle and 3' gene amplicons compared with the 5'. RNA was present in all oral fluids examined. Endogenous salivary beta-actin mRNA degraded more slowly than exogenous beta-actin mRNA, with half-lives of 12.2 and 0.4 min, respectively (P <0.001). Salivary RNA could not pass through 0.22 or 0.45 mum pores. Incubation of saliva with Triton X-100 accelerated degradation of salivary RNA.
  
  
  CONCLUSIONS
  Saliva harbors both full-length and partially degraded forms of mRNA. RNA enters the oral cavity from different sources, and association with macromolecules may protect salivary RNA from degradation.
authors.affiliation: Dental Research Institute, UCLA School of Dentistry, Johnson Comprehensive Cancer Center, Division of Head and Neck Surgery/Otolaryngology, Henry Samueli School of Engineering, UCLA, Los Angeles, CA 90095, USA.
authors.forename: Noh Jin
authors.initials: NJ
authors.lastname: Park
authors.forename: Yang
authors.initials: Y
authors.lastname: Li
authors.forename: Tianwei
authors.initials: T
authors.lastname: Yu
authors.forename: Brigitta M N
authors.initials: BM
authors.lastname: Brinkman
authors.forename: David T
authors.initials: DT
authors.lastname: Wong
mesh_terms: D000328:Adult; D004847:Epithelial Cells / Q000737:chemistry; D005881:Gingiva / Q000737:chemistry; D006801:Humans; D009055:Mouth / Q000737:chemistry; D009061:Mouth Mucosa / Q000737:chemistry / Q000166:cytology; D012313:RNA / Q000737:chemistry*; D020871:RNA Stability; D012333:RNA, Messenger / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012463:Saliva / Q000737:chemistry*
chemical_list: D012333:RNA, Messenger; D012313:RNA