Different regulation of oestrogen receptors alpha and beta in the human cervix at term pregnancy.

During pregnancy, a cervical connective tissue remodelling takes place, clinically recognized as softening, effacement and dilatation. The role of oestrogens and their receptors (ER) in this process is not clear. ERalpha is a ligand-activated transcription factor involved in many physiological processes. The identification of a second oestrogen receptor, ERbeta, has led to a re-evaluation of oestrogen signalling and physiology. The aim of this study was to monitor the expression of the two ERs in the cervix from women at term pregnancy (TP) and after parturition (PP) compared with that of non-pregnant (NP). A solution hybridization assay showed that the level of ERalpha mRNA was significantly decreased in the PP group, when compared with the NP and TP groups. In contrast the ERbeta mRNA level was increased in the TP group compared with the NP and PP groups. These results were supported by reverse transcription-polymerase chain reaction (RT-PCR). Similar results were observed for the protein with immunohistochemistry. Intense ERbeta immunostaining was observed in neutrophils and the endothelial cells of blood vessels. In conclusion, this study supports a concept according to which oestrogen might be involved in the final remodelling of the cervix via the modulating effects of the two ERs. Furthermore, oestrogen may mediate some effects on cervical ripening via ERbeta present in the invading neutrophils. Further studies are needed to elucidate this finding.