Body Fluid Specific Micro-RNA Markers: Characterising the Fluctuation of Expression in Vaginal Material when Analysed Over a Full Menstrual Cycle

Body fluid (BF) identification is a vital tool in progressing alleged sexual assault cases. The capability to do so is limited due to the absence of presumptive BF identification tests for vaginal material and aspermatozoic seminal fluid. Equally, where blood is present, distinguishing between venous and menstrual blood is also problematic. The characterisation of microRNA (miRNA) markers presents a potential solution to these problems. miRNA are abundant, stable, non-coding RNA’s, approximately 22 nucleotides in length which modulate gene expression post transcription. Their role in expression suggests the presence of BF specific miRNAs is likely, thus making them a robust tool for BF identification. Numerous miRNA were analysed and resulted in a set of markers capable of identifying a full BF panel. Research into expression level variation of miRNAs over the course of a menstrual cycle is lacking. Its dynamic nature results in many hormonal changes and the initiation of functions such as ovum release and detachment of the endometrial lining. It would therefore be expected that the regulation of these processes causes expression levels of miRNA to fluctuate and affect successful identification. The identified full BF panel of miRNA markers was then used to analyse daily vaginal material samples, which were provided by 5 females over the course of 31 days. Expression of each miRNA was measured using stem-loop reverse transcription, followed by qPCR. This study describes the changes in miRNA expression over a full menstrual cycle and therefore demonstrates their robustness as a successful BF identification tool.