Age-associated changes in bovine oocytes and granulosa cell complexes collected from early antral follicles.

Abstract

To assess the age-associated changes in oocytes and granulosa cells derived from early antral follicles (EAFs). Gene expression analysis of granulosa cells of the EAFs using a genome analyzer (Illumina) and in vitro culture of oocyte-granulosa cell complexes (OGCs) of EAFs (400-700μm in diameter) collected from ovaries of aged (>120months) and young (<50months) cows. Gene expression profiles in granulosa cells of EAFs of aged cows, which included changes in genes that encode chaperone proteins and antioxidants. In vivo development of EAFs, as determined by oocyte diameter of EAFs and AFs (3-6mm in diameter), appeared to be impaired in aged cows and the OGCs of aged cows contained low GSH compared to younger counterparts. When the OGCs were cultured in a medium containing low estradiol (E2, 0.1μg/mL), the ratio of antrum formation was higher for OGCs from aged animals than that from young animals, while higher abnormal fertilization rate and lower total cell number of the blastocysts were observed in the OGCs of aged cows compared with those of young cows. On the contrary, when the OGCs were cultured in a medium containing 10μg/mL E2, the ratio of antrum formation and fertilization outcome was comparable between the two age groups, whereas the total cell number of the blastocysts was still low in the aged group. Aging affects the gene expression profiles of the granulosa cells, and impairs in vitro developmental ability of OGCs collected from EAFs.