Reprod Dom Anim 50, 529–537 (2015); doi: 10.1111/rda.12551 ISSN 0936–6768
Review Article The Impact of Reproductive Technologies on Stallion Mitochondrial Function FJ Pe~na1,2, M Plaza Davila1, BA Ball2, EL Squires2, P Martin Mu~ noz1, C Ortega Ferrusola1 and C Balao da Silva1 1 Laboratory of Equine Reproduction and Equine Spermatology, Veterinary Teaching Hospital, University of Extremadura, C aceres, Spain; 2Gluck Equine Research Center, University of Kentucky, Lexington, KY, USA
Contents The traditional assessment of stallion sperm comprises evaluation of sperm motility and membrane integrity and identification of abnormal morphology of the spermatozoa. More recently, the progressive introduction of flow cytometry is increasing the number of tests available. However, compared with other sperm structures and functions, the evaluation of mitochondria has received less attention in stallion andrology. Recent research indicates that sperm mitochondria are key structures in sperm function suffering major changes during biotechnological procedures such as cryopreservation. In this paper, mitochondrial structure and function will be reviewed in the stallion, when possible specific stallion studies will be discussed, and general findings on mammalian mitochondrial function will be argued when relevant. Especial emphasis will be put on their role as source of reactive oxygen species and in their role regulating sperm lifespan, a possible target to investigate with the aim to improve the quality of frozen– thawed stallion sperm. Later on, the impact of current sperm technologies, principally cryopreservation, on mitochondrial function will be discussed pointing out novel areas of research interest with high potential to improve current sperm technologies.
Introduction Due to the increased use of sperm technologies in equine species, the last decade has witnessed the development of intense research in sperm technologies in the stallion and thus its impact on sperm functionality. A central feature connecting both issues is the role of the mitochondrion. Among others, substantial increases of our current knowledge have occurred in areas such as oxidative stress (Aitken and Koppers 2011; da Silva et al. 2011; Gibb et al. 2014), apoptoticlike changes (Ortega-Ferrusola et al. 2008; Ortega Ferrusola et al. 2009b) and the pivotal effects of changes in osmolality during cryopreservation; interestingly, many of these studies have been performed using the stallion as a model. Technologies such as cryopreservation and sex sorting have experienced substantial advances in the last decade (Pe~ na et al. 2011; Samper et al. 2012). In this review, we will discuss recent advances in the understanding of mitochondrial function, and the potential mechanisms explaining how mitochondrial dysfunction may impact fertility based in recent human studies. Moreover, evidence indicating that mitochondrial functionality may be used to © 2015 Blackwell Verlag GmbH
identify the fertilizing subpopulation of spermatozoa, and the potential utility of separation of spermatozoa based on their mitochondrial status will be discussed.
Structure and Basic Mechanisms of Mitochondrial Function Mitochondria are membrane-enclosed organelles that generate most of the ATP supply (Stowe and Camara 2009; Mizrahi and Breitbart 2014; Vadnais et al. 2014), although in some species glycolysis may be an important supply of ATP for sperm (Ferramosca et al. 2008). Mitochondrial compartments include the outer mitochondrial membrane (OMM), the intermembrane space (IMS), the inner mitochondrial membrane (IMM), the cristae and matrix (Prince and Buttle 2004). In addition to ATP generation, mitochondria also have a role in cell signalling, Ca2+ buffering (Breitbart et al. 1996; Costello et al. 2009; Bravo et al. 2014), apoptosis (Koppers et al. 2010; Ortega Ferrusola et al. 2010; Mendoza et al. 2013) and cell death (Thompson et al. 2003). The OMM contains a large number of channels, formed by integral proteins termed ‘porins’, that allow molecules of
Review Article The Impact of Reproductive Technologies on Stallion Mitochondrial Function FJ Pe~na1,2, M Plaza Davila1, BA Ball2, EL Squires2, P Martin Mu~ noz1, C Ortega Ferrusola1 and C Balao da Silva1 1 Laboratory of Equine Reproduction and Equine Spermatology, Veterinary Teaching Hospital, University of Extremadura, C aceres, Spain; 2Gluck Equine Research Center, University of Kentucky, Lexington, KY, USA
Contents The traditional assessment of stallion sperm comprises evaluation of sperm motility and membrane integrity and identification of abnormal morphology of the spermatozoa. More recently, the progressive introduction of flow cytometry is increasing the number of tests available. However, compared with other sperm structures and functions, the evaluation of mitochondria has received less attention in stallion andrology. Recent research indicates that sperm mitochondria are key structures in sperm function suffering major changes during biotechnological procedures such as cryopreservation. In this paper, mitochondrial structure and function will be reviewed in the stallion, when possible specific stallion studies will be discussed, and general findings on mammalian mitochondrial function will be argued when relevant. Especial emphasis will be put on their role as source of reactive oxygen species and in their role regulating sperm lifespan, a possible target to investigate with the aim to improve the quality of frozen– thawed stallion sperm. Later on, the impact of current sperm technologies, principally cryopreservation, on mitochondrial function will be discussed pointing out novel areas of research interest with high potential to improve current sperm technologies.
Introduction Due to the increased use of sperm technologies in equine species, the last decade has witnessed the development of intense research in sperm technologies in the stallion and thus its impact on sperm functionality. A central feature connecting both issues is the role of the mitochondrion. Among others, substantial increases of our current knowledge have occurred in areas such as oxidative stress (Aitken and Koppers 2011; da Silva et al. 2011; Gibb et al. 2014), apoptoticlike changes (Ortega-Ferrusola et al. 2008; Ortega Ferrusola et al. 2009b) and the pivotal effects of changes in osmolality during cryopreservation; interestingly, many of these studies have been performed using the stallion as a model. Technologies such as cryopreservation and sex sorting have experienced substantial advances in the last decade (Pe~ na et al. 2011; Samper et al. 2012). In this review, we will discuss recent advances in the understanding of mitochondrial function, and the potential mechanisms explaining how mitochondrial dysfunction may impact fertility based in recent human studies. Moreover, evidence indicating that mitochondrial functionality may be used to © 2015 Blackwell Verlag GmbH
identify the fertilizing subpopulation of spermatozoa, and the potential utility of separation of spermatozoa based on their mitochondrial status will be discussed.
Structure and Basic Mechanisms of Mitochondrial Function Mitochondria are membrane-enclosed organelles that generate most of the ATP supply (Stowe and Camara 2009; Mizrahi and Breitbart 2014; Vadnais et al. 2014), although in some species glycolysis may be an important supply of ATP for sperm (Ferramosca et al. 2008). Mitochondrial compartments include the outer mitochondrial membrane (OMM), the intermembrane space (IMS), the inner mitochondrial membrane (IMM), the cristae and matrix (Prince and Buttle 2004). In addition to ATP generation, mitochondria also have a role in cell signalling, Ca2+ buffering (Breitbart et al. 1996; Costello et al. 2009; Bravo et al. 2014), apoptosis (Koppers et al. 2010; Ortega Ferrusola et al. 2010; Mendoza et al. 2013) and cell death (Thompson et al. 2003). The OMM contains a large number of channels, formed by integral proteins termed ‘porins’, that allow molecules of
