Difference in mRNA expression and occurrence of plasminogen activator inhibitors in intrauterine decidua of normal and ectopic human pregnancies

The objective of this study was to elucidate the mechanisms involved in the formation of a functional decidua. The concentrations of plasminogen activators and plasminogen activator inhibitors in intrauterine decidua from normal and ectopic pregnancies were compared. Intrauterine decidua was obtained by curettage from 17 women with ectopic pregnancies and from five women with normal pregnancies. The gestational age was similar in the two groups. The antigen concentrations of plasminogen activators and plasminogen activator inhibitors in decidua homogenate were determined by ELISA and fibrinolytic activity was measured on fibrin plates. Localization was determined by immunohistochemical staining and mRNA was identified by in situ hybridization. Fibrinolytic activity was absent in decidua from normal pregnancies but present in the intrauterine decidua from ectopic pregnancies. High antigen concentrations of the inhibitors of fibrinolysis, PAI-1 and PAI-2, were found in normal decidua in contrast to low concentrations in decidua from ectopic pregnancies. Staining for PAI-1 as well as PAI-2 was positive in decidual cells. In situ hybridization resulted in high intensity signals for PAI-1 as well as for PAI-2 mRNA in decidua from normal pregnancies in contrast to very low intensity signals in decidua from ectopic pregnancies. The absence of proteolytic activity and high expression of PAI-1 and PAI-2 in normal decidua might facilitate attachment of the fertilized ovum and might also prevent detachment of the decidua.