PARENT SESSION

(6) PLASMINOGEN PROCESSING BY PERI-IMPLANTATION MOUSE EMBRYOS.

Baiza-Gutman, Luis¹, Martínez-Hernández, María¹, Aguilar-García, Cristina¹, Armant, D², ¹ Universidad Nacional Autónoma de México, México, México² Wayne State University, Detroit, MI

ABSTRACT- Trophoblast invasion and placenta formation during pregnancy in rodents entails endometrial tissue remodeling mediated by proteolytic enzymes. An important early step in the proteolytic cascade mediating extracellular matrix (ECM) degradation is the urokinase-type plasminogen activator-mediated transformation of plasminogen into plasmin, which can activate other proteases and degrade certain ECM proteins, including laminin and fibronectin. The aim of this study was to evaluate whether plasminogen can be processed to plasmin by peri-implantation trophoblast cells. E3.5 blastocysts were cultured under mineral oil in drops of Ham's F10 medium supplemented with 0.1% BSA. After two days, 0 or 10 g/ml plasminogen was added to the medium and culture was continued for two more days. Molecular forms of plasmin were identified by casein zymography of the conditioned medium and SDS-extracts of the culture plate surface. Several caseinolytic bands were produced from the exogenous plasminogen (plasminogen derivates) that had molecular weights ranging from 84 to 92 kDa and appeared to be plasmin. They were adsorbed to the culture surface by lysine binding sites (inhibited by -aminocaproic acid). Other plasminogen derivates with lower molecular weights were freely soluble in the medium. We conclude that implanting mouse blastocysts were able to process plasminogen to plasmin, and speculate that the latter is involved in tissue remodeling during embryo implantation and placenta formation. Supported by PAPIIT-DGAPA-UNAM to L.A.B-G. and NIH grant AA12057 to D.R.A.

KEY WORDS: trophoblast, embryo implantation, plasminogen, mouse embryo