506. MENSTRUAL CYCLE VARIATIONS IN PLASMA microRNA EXPRESSION PROFILES

Abstract

microRNAs are short, single-stranded RNAs that regulate gene expression at the post-transcriptional level. Plasma and serum microRNAs correlate closely with microRNA profiles of diseased tissue and have been explored as blood-based biomarkers for human diseases, including steroid-driven malignancies. However, reproductive steroid signalling regulates the expression of specific microRNAs and this could impact the utility of microRNA biomarkers in reproductive aged women. We hypothesised that microRNA expression profiles are altered by steroid hormone fluctuations associated with the menstrual cycle. To test this hypothesis, plasma microRNA expression was measured in healthy women at 3 stages of a 28 day menstrual cycle; ie menstrual (day 3-5), follicular (day 9–13) and implantation window/secretory phase (day 18–22). Total RNA was extracted from plasma, multiplex reverse transcription was performed, and the cDNA pre-amplified prior to expression analysis of 667 microRNAs on Taqman low density PCR arrays (n=6 women). Preliminary data shows that up to 200 microRNAs may be detected with this methodology, and that at least 14 of these are differentially expressed (fold change ≥±1.5) at follicular and secretory phase, as compared to menstrual phase. We plan to confirm these findings with standard Taqman microRNA assays (n=10 women). Our findings suggest that plasma miRNA expression profiles change over the menstrual cycle, and that this could confound microRNA-based diagnostic tests. We hope to demonstrate the most appropriate cycle phase for blood-based miRNA profiling, facilitating the development of plasma microRNA-based diagnostic tests and providing valuable information to researchers studying circulating microRNA profiles in reproductive aged women.