EN
The fertilization potential of mammalian oocytes may be regulated at the molecular level by the expression of species-specific sperm-egg interaction molecules, whose activities and/or cellular distribution determine the recognition and fusion of gemetes. Although there exist studies on the expression of integrins (ITGs) and zona pellucida glycoproteins (ZPs) in developmentally fully competent oocytes, the mRNA levels encoding these proteins in immature and developmentally incompetent porcine oocytes have to be elucidated. Therefore, our aim was to determine the expression of ITGB2, ZP3, and ZP3α mRNAs in porcine oocytes before in vitro maturation (IVM), in oocytes stained with BCB test but colorless, and in BCB positive oocytes after IVM. Porcine cumulus-oocyte complexes (COCs) were collected from 32 crossbred Landrace gilts, and then separated into three groups: (i) oocytes analyzed immediately after collection (n = 50), (ii) oocytes stained with brilliant cresyl blue (BCB+) and remained colorless (BCB–) (n = 50). After collection and/or staining and cultivation, all oocytes were denuded and analyzed regarding ITGB2, ZP3, and ZP3α by QT-PCR. We found a higher expression of ITGB2, ZP3, and ZP3α in oocytes immediately after collection and in BCB+ oocytes compared to BCB– oocytes (P < 0.001, respectively). No differences in the ITGB2 and ZP3 mRNA levels were observed between oocytes after collection and BCB+ oocytes. In addition, BCB– oocytes revealed lower transcript expression of all the genes under study. It is presumed that the similar mRNA levels of ITGB2 and ZP3 in oocytes after collection and in BCB+/ IVM oocytes may be related to (i) a toxic effect of BCB staining and/or to (ii) the degradation of accumulated maternal templates in porcine oocytes. Additionally, lower ITGB2, ZP3, and ZP3α transcript levels point to the down-regulation of the mRNA synthesis of stored maternal transcripts in developmentally incompetent porcine oocytes.