INTRODUCTION: Menstruation is induced by progesterone withdrawal at the end of the menstrual cycle and involves endometrial tissue breakdown, regeneration and repair. Perturbations in the regulation of menstruation may result in menstrual disorders including abnormal uterine bleeding. We aimed to elucidate the changing molecular profile of human endometrium on days 2, 3 and 4 of menstruation and identify genes and pathways that play a role in the menstrual process.
METHODS: Endometrial samples were collected by Pipelle biopsy on days 2 (n=9), 3 (n=9) or 4 (n=6) of menstruation. RNA was extracted and analysed by genome wide expression Illumina Sentrix Human HT12 arrays. Data were analysed using ‘Remove unwanted variation-inverse (RUV-inv). Ingenuity pathway analysis and the Database for Annotation, Visualisation and Integrated Discovery v6.7 were used to identify canonical pathways and functional gene clusters enriched between days 2, 3 and 4 of menstruation. Individual genes were validated by quantitative PCR.
RESULTS: Significant canonical pathways and gene clusters enriched during menstrual bleeding included those associated with immune cell trafficking, inflammation, cell cycle regulation, extracellular remodelling and the complement and coagulation cascade. The largest number of differentially expressed genes (1176) was between days 2 and 4 of menstruation. We identified several novel genes in the context of menstruation including lipopolysaccharide binding protein (LBP), glutathione-S-transferase mu 1 and -2 (GSTM1/2), V-set domain containing T cell activation inhibitor 1 (VTCN1) and trefoil factor 3 (TFF3). Genes related to processes associated with inflammation were up-regulated on day 2 of menstruation (early-menstruation) whereas those associated with endometrial repair and regeneration were up-regulated on day 4 of menstruation (late-menstruation).
CONCLUSION: The changing molecular profile during menstruation identifies a number of genes not previously associated with menstruation. Our findings provide new insights into the menstrual process and may present novel targets for therapeutic intervention in cases of endometrial dysfunction.