Quantitative evaluation of endometrium-expressed mRNAs for the purpose of discriminating between menstruation and traumatic vaginal injury in sexual assault cases.

In sexual assault cases, it is crucial to discriminate between peripheral blood and menstrual blood to provide evidence for vaginal intercourse with traumatic injury. In this study, the menstrual blood mRNA markers progestagen-associated endometrial protein (PAEP), matrix metallopeptidase 7 (MMP7), and left-right determination factor 2 (LEFTY2) were evaluated by quantitative RT-PCR (RT-qPCR) for the discrimination of menstrual blood from peripheral blood and vaginal fluid. As a result, all markers with cutoff delta cycle quantification (ΔCq) values were specifically determined in menstrual blood among forensically relevant body fluids. Even though the changes in the expression levels of each marker differed during the menstrual cycle, all markers were determined to be positive in most of the randomly collected menstrual blood samples that were analyzed. Additionally, the markers with proposed cutoff ΔCq values could discriminate between menstrual blood and peripheral blood-mixed vaginal fluid samples. The determination of positive markers was less affected by storage temperature under dry conditions than under wet conditions, while PAEP was detectable in samples stored below room temperature under wet conditions. The detectability of PAEP was considered to be the result of its higher expression level compared with MMP7 and LEFTY2. In conclusion, menstrual blood markers for the RT-qPCR procedure evaluated in this study were highly specific for menstrual blood. The proposed procedure could be useful for discriminating between menstruation and traumatic bleeding in the female genital tract. In particular, PAEP is expected to be applicable to forensic casework samples because of its high specificity and robustness.