Expression Of Tissue-Type Plasminogen Activator-Plasminogen Activator Inhibitor-1System In Bovine Cumulus-Oocytes During In Vitro Maturation

In the present study, four experiments were conducted to investigate the potential effects of tPA, PAI-1and PLG on bovine cumulus cells and oocytes during in vitro maturation (IVM)(0h,8h,16h,24h). The expressions of tPA, PAI-1and PLG were detected by relative real-time RT-PCR experiments in bovine cumulus cells and oocytes both after0h,8h,16h,24h of IVM and under different FSH concentrations after16h of IVM separately. Meanwhile, the degree of bovine cumulus cell expansion and first polar body extrusion in oocyte were assessed respectively.1. TPA mRNA levels were higher in cumulus cells and oocytes at16h and24h than those at0h and8h of IVM significantly(P<0.05). PAI-1mRNA levels were higher in cumulus cells at8h than those at16h and24h of IVM significantly(P<0.05). The whole trend of PAI-1mRNA levels were similar to tPA in cumulus cells, while PAI-1mRNA levels were the highest at24h in oocytes, and higher at16h than those at0h and8h of IVM significantly(P<0.05).2. Among those groups that under different FSH concentrations (0,0.01,0.1and1IU/mL) after16h of IVM, tPA mRNA levels of cumulus cells was increased following the elevated FSH concentrations, as well as the cumulus expansion, the gap junctions of cumulus cells in1IU/mL FSH group was significantly looser and darker than others. PAI-1mRNA of cumulus cells in0.01IU/mL FSH group was significantly higher than others (P<0.05). PLG mRNA levels in0.01IU/mL FSH group were the lowest in cumulus cells, then in0.1IU/mL andl IU/mL FSH group increased dramatically (P<0.05). Expression of tPA showed a similar trend with the first polar body in oocytes that tPA mRNA levels of the0.01IU/mLFSH group and the first polar body extrusion significantly higher than the other groups (P<0.05).Meanwhile, PAI-1mRNA of oocytes0.01IU/mL FSH group significantly higher than others (P<0.05).3. Among those groups that addition of FRBI-10to the COCs after16h of IVM, the expression level of tPA mRNA in cumulus cells in only addition of FSH group significantly higher than others (P<0.05). TPA mRNA in the oocytes in only addition of FSH group was significantly higher than the blank group (P<0.05). In only addition of FSH group both the expression levels of PAI-1mRNA in cumulus cells and oocytes were significantly higher than all other groups. While in only addition of FSH group the expression levels of PLG mRNA both in cumulus cells and oocytes were lower than the blank group dramatically (P<0.05).Our conclusions are as followed, the expression of tPA and PAI-1in bovine cumulus was regulated positively by FSH, while the expression of PLG was inhibited by FSH. During in vitro maturation tPA-PAI-1system does not play a proactive role in cumulus expansion, and the sytem could participate in bovine follicle ovulation.However, it need to be further investigated that tPA-PAI-1system expression may be involved in first polar body excrusion of bovine oocytes. These results contribute to the further research on the specific roles of tPA-PAI-1system in bovine COCs during IVM.