Hormonal and follicular factors affecting maturation of sheep oocytes in vitro and their subsequent developmental capacity.
Oocytes removed from, or retained within, non-atretic and atretic follicles of different sizes were cultured for 24 h in the presence of a variety of hormones in an attempt to identify the factors affecting oocyte maturation in vitro. Resumption of meiosis was assessed morphologically; the developmental capacity of oocytes after culture was determined by transfer to the oviducts of inseminated ewes. About 70% of oocytes cultured after removal from follicles of different sizes resumed meiosis in vitro, but they did not undergo normal development after transplantation. Oocytes cultured within the follicle in hormone-free medium remained at the germinal vesicle stage. In the presence of FSH and LH some oocytes reached the second meiotic metaphase: 19% in small (2-3 mm diam.) and 73% in larger (3-5 mm diam.) non-atretic follicles, and 54% in small and 45% in larger atretic follicles. Less than 5% of oocytes cultured in follicles developed into normal blastocysts after transplantation when either no hormone or only FSH and LH were added to the culture medium. The addition of oestradiol-17beta to medium containing FSH (2 mug/ml) and LH (1 mug/ml) resulted in the development to blastocysts of 26% of oocytes from small non-atretic follicles, 46% from large non-atretic follicles and 50% from atretic follicles. Blastocyst formation was greatly depressed and fragmentation rate signinificantly increased with concentrations of 10 mugFSH/ml and 2 mug LH/ml. Developmental capacity after culture was further demonstrated by the birth of lambs from 63% of blastocysts derived from oocytes matured in vitro; 52% of control blastocysts developed to lambs after transfer.
D000818:Animals; D002478:Cells, Cultured; D003470:Culture Media; D004624:Embryo Transfer; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D006062:Gonadotropins / Q000494:pharmacology; D008540:Meiosis / Q000187:drug effects; D009865:Oocytes / Q000502:physiology* / Q000637:transplantation; D006080:Ovarian Follicle / Q000502:physiology*; D010063:Ovum / Q000502:physiology*; D011247:Pregnancy; D012756:Sheep / Q000502:physiology*; D014184:Transplantation, Homologous
D003470:Culture Media; D006062:Gonadotropins; D004958:Estradiol