title: Maternal age and in vitro culture affect mitochondrial number and function in equine oocytes and embryos.
abstract: Advanced maternal age and in vitro embryo production (IVP) predispose to pregnancy loss in horses. We investigated whether mare age and IVP were associated with alterations in mitochondrial (mt) DNA copy number or function that could compromise oocyte and embryo development. Effects of mare age (<12 vs ≥12 years) on mtDNA copy number, ATP content and expression of genes involved in mitochondrial replication (mitochondrial transcription factor (TFAM), mtDNA polymerase γ subunit B (mtPOLB) and mitochondrial single-stranded DNA-binding protein (SSB)), energy production (ATP synthase-coupling factor 6, mitochondrial-like (ATP-synth_F6)) and oxygen free radical scavenging (glutathione peroxidase 3 (GPX3)) were investigated in oocytes before and after in vitro maturation (IVM), and in early embryos. Expression of TFAM, mtPOLB and ATP-synth-F6 declined after IVM (P<0.05). However, maternal age did not affect oocyte ATP content or expression of genes involved in mitochondrial replication or function. Day 7 embryos from mares ≥12 years had fewer mtDNA copies (P=0.01) and lower mtDNA:total DNA ratios (P<0.01) than embryos from younger mares, indicating an effect not simply due to lower cell number. Day 8 IVP embryos had similar mtDNA copy numbers to Day 7 in vivo embryos, but higher mtPOLB (P=0.013) and a tendency to reduced GPX3 expression (P=0.09). The lower mtDNA number in embryos from older mares may compromise development, but could be an effect rather than cause of developmental retardation. The general down-regulation of genes involved in mitochondrial replication and function after IVM may compromise resulting embryos.
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 114, 3584 CM Utrecht, The Netherlands.
authors.forename: W Karin
authors.initials: WK
authors.lastname: Hendriks
authors.affiliation: Avantea, Laboratorio di Tecnologie della Riproduzione, Via Porcellasco 7f, 26100 Cremona, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Colleoni
authors.affiliation: Avantea, Laboratorio di Tecnologie della Riproduzione, Via Porcellasco 7f, 26100 Cremona, Italy.
authors.forename: Cesare
authors.initials: C
authors.lastname: Galli
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 114, 3584 CM Utrecht, The Netherlands.
authors.forename: Damien B B P
authors.initials: DB
authors.lastname: Paris
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 114, 3584 CM Utrecht, The Netherlands.
authors.forename: Ben
authors.initials: B
authors.lastname: Colenbrander
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 114, 3584 CM Utrecht, The Netherlands.
authors.forename: Bernard A J
authors.initials: BA
authors.lastname: Roelen
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 114, 3584 CM Utrecht, The Netherlands.
authors.forename: Tom A E
authors.initials: TA
authors.lastname: Stout
mesh_terms: D000818:Animals; D004272:DNA, Mitochondrial; D046149:Embryo Culture Techniques; D047108:Embryonic Development / Q000502:physiology*; D005260:Female; D006736:Horses; D059471:In Vitro Oocyte Maturation Techniques / Q000662:veterinary*; D008423:Maternal Age; D008928:Mitochondria / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism*; D011247:Pregnancy
chemical_list: D004272:DNA, Mitochondrial