The Effects of Gonadotropin-Releasing Hormone (GnRH) I and GnRH II on the Urokinase-Type Plasminogen Activator/Plasminogen Activator Inhibitor System in Human Extravillous Cytotrophoblasts in Vitro

The regulated expression of the urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor (PAI-1) is believed to modulate the invasive capacity of human trophoblastic cells in vitro and in vivo. To date, the factors capable of regulating the expression of uPA and PAI-1 in these cells remain poorly characterized. In these studies, we have examined the ability of the classical mammalian GnRH I and the second form of GnRH (GnRH II) to regulate uPA and PAI-1 mRNA and protein expression levels in primary cultures of human extravillous cytotrophoblasts using quantitative competitive PCR and ELISA, respectively. Both GnRH I and II increased uPA and concomitantly decreased PAI-1 mRNA and protein expression levels in our extravillous cytotrophoblast cultures in a dose- and time-dependent manner. Cetrorelix, a peptide GnRH antagonist specific for the GnRH I receptor, was capable of inhibiting the regulatory effects of GnRH I, but not GnRH II on uPA and PAI-1 expression levels in primary cell cultures. Taken together, these observations suggest that GnRH I and GnRH II may facilitate trophoblast invasion by increasing the ratio of uPA/PAI-1 expression via interactions with two distinct GnRH receptors.