Oestrogen receptor α and β mRNA expression in human endometrium throughout the menstrual cycle

We examined the localization of oestrogen receptor (ER) beta mRNA in the human endometrium throughout the menstrual Cycle using non-radioactive in-situ hybridization with Brigati-tailed oligonucleotides. The findings were compared with those of ER alpha in order to examine the possible biological significance of ER beta in the human endometrium. Both ER alpha and ER beta mRNA expression were detected in all major human uterine cell types, including glandular epithelial cells, stromal cells and smooth muscle cells of the uterine wall, at every menstrual cycle stage. However, ER alpha mRNA expression was more prominent than that of ER beta in all cell types throughout the menstrual cycle. In proliferative phase endometrium, ER alpha mRNA was expressed in both glandular epithelial and stromal cells, while ER beta mRNA was expressed predominantly in glandular epithelial cells. Although the same pattern was observed in the secretory phase, both the ER alpha and ER beta mRNA expression was relatively weaker. These results suggest that oestrogenic effects occur predominantly through ER alpha, but that ER beta may also play a role in the modulation of oestrogenic action, especially on glandular epithelial cells in the human endometrium throughout the menstrual cycle.