Maturation and culture affect the metabolomic profile of oocytes and follicular cells in young and old mares.

Oocytes and follicular somatic cells within the ovarian follicle are altered during maturation and after exposure to culture . In the present study, we used a nontargeted metabolomics approach to assess changes in oocytes, cumulus cells, and granulosa cells from dominant, follicular-phase follicles in young and old mares. Samples were collected at three stages associated with oocyte maturation: (1) GV, germinal vesicle stage, prior to the induction of follicle/oocyte maturation ; (2) MI, metaphase I, maturing, collected 24 h after induction of maturation ; and (3) MIIC, metaphase II, mature with collection 24 h after induction of maturation plus 18 h of culture .

Equine maternal aging affects the metabolomic profile of oocytes and follicular cells during different maturation time points.

Oocyte quality and fertility decline with advanced maternal age. During maturation within the ovarian follicle, the oocyte relies on the associated somatic cells, specifically cumulus and granulosa cells, to acquire essential components for developmental capacity. A nontargeted metabolomics approach was used to investigate the effects of mare age on different cell types within the dominant, follicular-phase follicle at three time points during maturation.

Effect of Mare Age on Transcript Abundance of Connexins-37 and -43, Zona Pellucida Proteins, and Sperm Binding.

Zona pellucida (ZP) proteins are important for fertilization and sperm binding and are closely associated with cumulus cells. Communication between cumulus and oocytes is facilitated by intracellular membrane channels composed of connexins. The extent aging impacts potential differences in fertilization and reductions in fertility is not well understood.

Autogenous transfer of intracytoplasmic sperm injection-produced equine embryos into the uterus of the oocyte donor during the same oestrous cycle.

The clinical use of intracytoplasmic sperm injection (ICSI) in horses usually involves the transfer of embryos into recipient mares, resulting in substantial cost increases. This is essential when subfertile mares are oocyte donors; but some donors are fertile, with ICSI compensating for limited or poor-quality spermatozoa. Fertile oocyte donors could carry pregnancies, eliminating the need for a recipient.