Lack of gestation-related changes of urocortin gene expression in human placenta

Objectives: Urocortin is a newly discovered peptide, a member of the corticotropin-releasing factor (CRF) family, and is expressed in human pituitary gland and placenta. Structural and functional similarities between urocortin and CRF have been demonstrated, including an equipotent stimulation of placental prostaglandin release and myometrial contractility. The aims of the present study were, first, to investigate whether urocortin mRNA expression differs from early to late pregnancy, and second, to localize urocortin mRNA in human placental trophoblast. Methods: Placental trophoblast was collected from women undergoing elective aspiration termination of pregnancy (12 weeks, n = 8), or elective Cesarean section for routine indications carried out at term in the absence of labor (40 weeks, n = 8). Urocortin mRNA levels were determined by Northern blotting and its cellular type localization was evaluated by in situ hybridization. Results: Northern analysis showed no significant difference in urocortin gene expression in trophoblast cells between the first and third trimesters of normal healthy pregnancy. Syncytiotrophoblast cells of both secondary and tertiary villi showed an intense hybridization signal for urocortin mRNA. The urocortin mRNA signal was less intense in cytotrophoblast cells as well as within the structure of the villi, and no signal was observed on blood vessels within trophoblast villi. Conclusion: The present data show that the expression of urocortin mRNA in human placenta is concentrated in the syncytial layer, which coincides with the known localization of the mature peptide. Furthermore, placental urocortin expression does not seem to change from the first trimester to term pregnancy.