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Abstract
Brilliant cresyl blue (BCB) is a super vital stain that has been used to select competent oocytes in different species. The objectives of the first part of the present studies were to determine mRNA abundance for select TGFÝ superfamily components, SMAD2/3 and SMAD1/5 phosphorylation levels and transcript abundance for other oocyte (JY1) and cumulus cell (CTSB, CTSK, CTSS and CTSZ) markers of oocyte quality in bovine oocytes and or adjacent cumulus cells classified based on developmental potential using BCB staining. The ability of exogenous FST, JY1, or cathepsin inhibitor treatment to rescue development of embryos derived from poor quality oocytes selected based on BCB staining was also determined. Cumulus oocyte complexes (COCs) from abattoir derived ovaries were subjected to BCB staining and GV stage oocytes and cumulus cells harvested from control, BCB+ and BCB- (poor oocyte quality) groups for real time PCR or Western blot analysis. Remaining COCs underwent in vitro maturation, in vitro fertilization and embryo culture in presence or absence of above described treatments. Levels of FST, JY1, BMP15 and SMAD1, 2, 3 and 5 transcripts were higher in BCB+ oocytes whereas abundance of CTSB, CTSK, CTSS and CTSZ mRNAs was higher in cumulus cells surrounding poor quality BCB- oocytes. Western blot analysis revealed SMAD1/5 and SMAD2/3 phosphorylation were higher in BCB+ than BCB- oocytes. Embryo culture studies demonstrated that follistatin and cathepsin inhibitor treatment but not JY-1 treatment can rescue developmental competence of BCB- oocytes. Results provide further understanding of molecular indices of oocyte competence.