Effect of the Activation and Inhibition of the Plasminogen/Plasmin System During In Vitro Maturation of Bovine Oocytes: A Biological and Spectroscopic Approach

RIZO, G.; JIMENEZ, LUIS EMANUEL; GARCÍA, ELINA VANESA; GARCÍA, DANIELA CELESTE; BARRERA, AD; ALVAREZ, RMS; MARIELA ROLDÁN OLARTE

Ciudad Autonoma de Buenos Aires

Congreso; Reunion Conjunta de Biociencias; 2017

SAIB

The Plasminogen (Plg)/Plasmin (Plm) proteolytic system plays a crucial role during the initial steps of mammalian reproduction. Plg must interact with its activators to become Plm, involved in a broad spectrum of proteolytic processes. Due that Plg is in the zona pellucida (ZP) and plasma membrane of bovine oocytes, this study examines the effect of the exogenous activation or inhibition of Plg/Plm during the in vitro maturation (IVM) of cumulus oocytes complexes (COCs). Three groups were studied: i) control (COCs), ii) with 3.5 IU/mL streptokinase, an exogenous Plg activator (COCs/SK) iii) with 10 mM ε-aminocaproic acid, a specific inhibitor of Plm proteolytic activity (COCs/ε-ACA). After 22  h of IVM, oocytes were processed and evaluated. It was observed that in COCs/SK the percentages of metaphasic II (MII) oocytes were not modified, while in COCs/ε-ACA a decrease in the number of MII oocytes was evidenced. Cumulus expansion after IVM was employed to evaluate the effect of Plm activity. By microphotographs it was observed that ε-ACA inhibits the cumulus expansion respect to the control and SK. Modifications in the ZP were evaluated by measuring the time of digestion of ZP (dtZP) with pronase. No significant differences in the dtZP between COCs and COCs/SK were observed. However, in COCs/ε-ACA the resistance of ZP to enzymatic digestion was increased. Physicochemical properties of the ZP were also studied by Raman microspectroscopy. Spectral differences were related to specific structural changes in glycoproteins upon IVM with ε-ACA. The intensity decrease in the sialic acid band agrees with previous results regarding the in vitro fertilization: the biological effect of ε-ACA would be interpreted like a reduced interaction between the ZP oocyte and the sperm. Considering all these results, the inhibition of Plm activity by ɛ-ACA produces a negative effect in the in vitro matured oocytes. On the contrary, negligible effects were observed with SK.