Human endometrial stromal interleukin-1 beta: autocrine secretion and inhibition by interleukin-1 receptor antagonist

Decidualization of human endometrial stromal cells is suppressed by endometrial IL-1 in an autocrine or paracrine manner, indicating that constant suppression of stromal decidualization by IL-1 requires a neutralizing mechanism for IL-1 action to accept embryo implantation. Since production of IL-1ra in human endometrium is reported to be 10- to 30-fold higher than that of IL-1 alpha/beta, we investigated whether endogenous IL-1 beta secreted from human endometrial stromal cells can be inhibited by IL-1ra by using an in vitro decidualization culture. Human stromal cells were cultured with 8-Br-cAMP to induce decidualization, and concentrations of IL-1 beta, IL-8, and prolactin in the culture supernatants were assayed before and after decidualization. There was no significant difference in mean IL-1 beta concentrations measured before and after decidualization. Addition of IL-1ra to endometrial stromal cell cultures strongly inhibited endogenous IL-8 secretion from the cells. Although IL-1 beta showed a biphasic effect on cell proliferation and a suppressive effect on decidualization of stromal cells, these effects were completely inhibited by IL-1ra. The results imply that a high in vivo concentration of IL-1ra in human endometrial tissues may regulate IL-1 effects on decidualization and cell proliferation of human endometrial stromal cells.