Localization of plasminogen activator inhibitor type 1 and 2 in preimplantation mouse development in vitro

Plasminogen activator inhibitor type 1 (PAI-1) and type 2 (PAI-2) are the major endogenous inhibitors of fibrinolysis, or thrombolysis, as it is effective in blocking the conversion of plasminogen to plasmin. In mammalian embryos, both PAI-I and PAI-2 proteins are expressed in the trophoblasts during and after implantation, suggesting their critical roles in implantation and placentation during pregnancy. However, it remains unclear how both proteins localize in the early stage embryos before implantation. In this study, 2 cell stage embryos were flushed from the oviducts and cultured to specified stages in medium at 37 degrees C in a 5% CO2 incubator. Embryos were fixed and double immunostained with anti-PAI-1 and anti-PAI-2 antibody. We determined the critical expression and localization patterns of PAI-1 and PAI-2 proteins in murine preimplantation embryos at 2 cell, 8 cell, morula and blastocyst stages by using confocal laser scanning microscope. We found that PAI-1 and PAI-2 constantly express in the embryos during preimplantation development, and these proteins localize in both the cytoplasm and the nucleus of each blastomere regardless of their developmental stage. Our results suggest that PAI-I and PAI-2 proteins may play roles in early embryonic development before implantation.