title: Advancing maternal age predisposes to mitochondrial damage and loss during maturation of equine oocytes in vitro.
abstract: In many mammalian species, reproductive success decreases with maternal age. One proposed contributor to this age-related decrease in fertility is a reduction in the quantity or functionality of mitochondria in oocytes. This study examined whether maternal age or (in vitro maturation). IVM affect the quantity of mitochondria in equine oocytes. Oocytes were collected from the ovaries of slaughtered mares categorized as young (<12 years) or aged (≥12 years) and either denuded and prepared for analysis immediately (not-IVM) or matured in vitro for 30 hours before preparation (IVM). The mean oocyte mitochondrial DNA copy number was estimated by quantitative polymerase chain reaction and found to be significantly lower in oocytes from aged mares and that had been subjected to IVM than in any other group. Transmission electron microscopy demonstrated that mitochondria in aged mare oocytes subjected to IVM experienced significantly more swelling and loss of cristae than in other groups. We conclude that maternal aging is associated with a heightened susceptibility to mitochondrial damage and loss in equine oocytes, which manifests during IVM. This predisposition to mitochondrial degeneration probably contributes to reduced fertility in aged mares.
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 112, 3584 CM Utrecht, The Netherlands.
authors.forename: B P B
authors.initials: BP
authors.lastname: Rambags
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 112, 3584 CM Utrecht, The Netherlands.
authors.forename: D C J
authors.initials: DC
authors.lastname: van Boxtel
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 112, 3584 CM Utrecht, The Netherlands.
authors.forename: T
authors.initials: T
authors.lastname: Tharasanit
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 112, 3584 CM Utrecht, The Netherlands.
authors.forename: J A
authors.initials: JA
authors.lastname: Lenstra
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 112, 3584 CM Utrecht, The Netherlands.
authors.forename: B
authors.initials: B
authors.lastname: Colenbrander
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 112, 3584 CM Utrecht, The Netherlands. Electronic address: t.a.e.stout@uu.nl.
authors.forename: T A E
authors.initials: TA
authors.lastname: Stout
mesh_terms: D000375:Aging; D000818:Animals; D005260:Female; D006736:Horses / Q000502:physiology*; D059471:In Vitro Oocyte Maturation Techniques / Q000662:veterinary*; D063306:Mitophagy / Q000502:physiology*; D009865:Oocytes / Q000166:cytology / Q000502:physiology*
keywords: Horse; In vitro maturation; Maternal age; Mitochondrion; Oocyte