Expression of 20alpha-hydroxysteroid dehydrogenase mRNA in human endometrium and decidua.

Progesterone secreted from ovarian corpus luteum plays pivotal roles in endometrial differentiation, and local progesterone metabolism to regulate its concentration in endometrial tissues is essential for the successful implantation and maintenance of pregnancy. In this study, we evaluated the expression of mRNA for 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD), a key enzyme which converts progesterone to a biologically inactive metabolite, in human endometrial tissues and cultured endometrial stromal cells as well as decidua and chorionic tissues of early pregnancy. The level of 20alpha-HSD mRNA expression in secretory phase endometrium was significantly higher than that in proliferative phase endometrium and chorionic tissues. The expression level in decidual tissue was also significantly higher than that in chorionic tissue. In cultured endometrial stromal cells, 20alpha-HSD mRNA expression was slightly enhanced at a lower progesterone concentration of 0.01 micromol/l, and an increase in its expression was significantly suppressed at higher concentrations of 1 micromol/l or greater. No effect on the gene expression was seen in cultured endometrial stromal cells with various concentrations of 17beta-estradiol. These results suggest that progesterone itself contributes to the regulation of local progesterone concentration through 20alpha-HSD levels in endometrial stromal cells at peri-implantation periods.