The Impact of Reproductive Technologies on Stallion Mitochondrial Function

Abstract

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.

Flow Cytometry Probes to Evaluate Stallion Spermatozoa

“…These enzymes are present in stallion spermatozoa, possibly as sperm specific isoforms [47]. Numerous studies indicate that ROS are important regulators of sperm function [48][49][50][51][52], and ROS become detrimental only if homeostasis is lost [1]. Moreover, recent evidence suggests that stallion sperm mitochondria produce significant amounts of NO [47].…”

“…The mitochondria of spermatozoa are increasingly studied in both basic and applied andrology [1,14,23]. Stallion spermatozoa are highly dependent on mitochondrial production of ATP, and mitochondrial malfunction leads rapidly to sperm senescence and death.…”

“…Consequently, a better understanding of sperm function in relation to clinical andrology and sperm biotechnologies [1,2] has arisen. Relevant advances in stallion sperm biology include, among others, the following: the understanding of osmotic shock [3][4][5] and its implications on cryopreservation, which promoted the development of new protocols based on more permeant cryoprotectants [6][7][8][9][10]; advances in understanding the role of reactive oxygen species (ROS) [11][12][13][14]; and the development of practical methods for stallion sperm separation and selection through colloidal centrifugation [15][16][17][18][19][20][21].…”

<b>Impacto da qualidade espermática sobre a fertilidade <i>in vivo</i> em bovinos:</b> contribuição de marcadores mitocondriais e subpopulações espermáticas

“…Além disso, as mitocôndrias estão ativamente implicadas em outros processos, tais como a diferenciação celular, a geração de ROS e metabolismo do ferro (PIOMBONI et al, 2010;AMARAL et al, 2013). A ideia de que a mitocôndria desempenha um papel importante na etiologia da infertilidade masculina é relatada por alguns autores (RAMALHO-SANTOS et al, 2009;RAMALHO-SANTOS, 2010;AITKEN et al, 2012a;PEÑA et al, 2015).…”

“…Em primeiro lugar, exclusivamente estas organelas estão confinadas na peça intermediária do espermatozoide, firmemente enrolada em torno do axonema e a parte principal da cauda espermática é desprovida de mitocôndrias e enriquecida com enzimas glicolíticas (PIOMBONI et al, 2012). As mitocôndrias são geralmente conhecidas como "usina de energia" da célula, pois desempenham um papel crucial na produção de ATP através do sofisticado mecanismo da fosforilação oxidativa ou OXPHOS (PIOMBONI et al, 2010).…”