Abstract
Sperm quality assessment is the first step for evaluating male fertility and includes the estimation of sperm concentration, motility, and morphology. Nevertheless, other parameters can be assessed providing additional information on the male reproductive potential. This study aimed to evaluate and correlate the oxidative status, mitochondrial functionality, and motility in spermatozoa of two marine invertebrate (Ciona robusta and Mytilus galloprovincialis) and one mammalian (Bos taurus) species. By combining fluorescent staining and spectrofluorometer, sperm oxidative status was evaluated through intracellular reactive oxygen species (ROS) and plasma membrane lipid peroxidation (LPO) analysis. Mitochondrial functionality was assessed through the mitochondrial membrane potential (MMP). In the three examined species, a negative correlation emerged between sperm motility vs ROS levels and LPO. Sperm motility positively correlated with MMP in bovine, whereas these parameters were not related in ascidian or even negatively related in mussel spermatozoa. MMP was negatively related to ROS and LPO levels in ascidians, only to LPO in bovine, and positively related in mussel spermatozoa. These results suggest that energy sources for sperm motility vary between species and that ROS causes a decline in sperm motility via oxidative damage of membrane lipids. Overall, this study validates the use of fluorescent probes in combination with spectrofluorometer as a simple and powerful methodology for supplementary evaluation of sperm quality shedding light on new potential quality markers and provided relevant information on sperm energetic metabolism.
Highlights
The spermatozoon is a highly specialized haploid cell generated in the male gonad through a differentiation process called spermatogenesis
Our results reveal that total motility and membrane potential (MMP) are not associated (C. robusta) or even negatively related (M. galloprovincialis) suggesting that, in these species, oxidative phosphorylation may not represent the major source of energy for sperm motility
This study validates a new approach to investigate different sperm quality parameters (MMP, reactive oxygen species (ROS), and lipid peroxidation (LPO)) by combining fluorescent staining and spectrofluorometric and correlate these parameters with each other to evaluate their possible use as new predictors of sperm quality
Summary
The spermatozoon is a highly specialized haploid cell generated in the male gonad through a differentiation process called spermatogenesis. The function of spermatozoon is to deliver the paternal genome into the female gamete during fertilization, the very special event in which the two gametes fuse their genomes originating a zygote, the first cell of a new diploid individual. To accomplish this task, spermatozoa are equipped with specific structures: a flagellum, which generates the movement, and a very compact nucleus that ensures protection of the paternal genome. Flagellar movement requires an adequate supply of energy in the form of ATP, which is used by the flagellar dynein-ATPase localized into the axoneme along the entire length of the flagellum [2].
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