Proteomics is advancing the understanding of stallion sperm biology

The mammalian ejaculate is very well suited to proteomics studies. As such, research concerning sperm proteomics is offering a huge amount of new information on the biology of spermatozoa. Among domestic animals, horses represent a species of special interest, in which reproductive technologies and a sizeable market of genetic material have grown exponentially in the last decade. Studies using proteomic approaches have been conducted in recent years, showing that proteomics is a potent tool to dig into the biology of the stallion spermatozoa. The aim of this review is to present an overview of the research conducted, and how these studies have improved our knowledge of stallion sperm biology. The main outcomes of the research conducted so far have been an improved knowledge of metabolism, and its importance in sperm functions, the impact of different technologies on the sperm proteome, and the identification of potential biomarkers. Moreover, proteomics of seminal plasma and phosphoproteomics are identified as areas of major interest.

Effects of activation and assisted reproduction techniques on the composition, structure, and properties of the sauger (Sander Canadensis) spermatozoa plasma membrane

The sperm plasma membrane is a multifunctional organelle essential to fertilization. However, assisted reproduction techniques often negatively affect this structure, resulting in reduced fertility. These reductions have been attributed to plasma membrane damage in a wide array of species, including fish. Considerable research has been conducted on the fish sperm membrane, but few have examined the effect of cryopreservation and other assisted reproduction techniques (ARTs) on not only membrane composition, but also specific characteristics (e.g., fluidity) and organization (e.g., lipid rafts). Herein, we determined the effects of three ARTs (testicular harvest, strip spawning, and cryopreservation) on the sperm plasma membrane, using Sauger (Sander canadensis) sperm as a model. To this end, a combination of fluorescent dyes (e.g., merocyanine 540, filipin III, cholera toxin subunit β), liquid chromatography - mass spectroscopy (LC-MS) analysis of membrane lipids, and membrane ultracentrifugation coupled with plate assays and immunofluorescence were used to describe and compare sperm fluidity, membrane composition, as well as lipid raft composition and distribution among sperm types. Stripped sperm became more fluid following motility activation (40% increase in highly fluid cells characterized by a 2 × increase in fluorescence) and contained lipid rafts restricted to the midpiece. Testicular harvest yielded sperm with characteristics similar to stripped sperm. By contrast, cryopreservation impacted every aspect of membrane physiology. Two cell populations, one highly fluid and the other rigid, resulted from the freeze-thaw process. Cryopreservation reduced lipid raft cholesterol content by 44% and flotilin-2 (a lipid raft marker) was partially displaced owing to a decrease in buoyancy. Unlike stripped and testicular sperm, LC-MS analysis revealed increases in oxidative damage markers, membrane destabilization, and apoptotic signaling in cryopreserved sperm. Ultrastructural analysis also revealed widespread physical damage to the membrane following freeze-thaw. Sperm motility, however, was unrelated to any measure of membrane physiology used in this study. Our results demonstrate that ARTs have the potential to substantially affect the sperm plasma membrane, but not always detrimentally. These results provide multiple potential biomarkers of sperm quality as well as insight into sources of sub-fertility resulting from use of ARTs.

Exposure to China dust exacerbates testicular toxicity induced by cyclophosphamide in mice

This study investigated the potential effects of China dust (CD) exposure on cyclophosphamide (CP)-induced testicular toxicity in mice, focusing on spermatogenesis and oxidative damage. CP treatment reduced testicular and epididymal weight and sperm motility and enhanced sperm abnormality. Histopathological examination presented various morphological alterations in the testis, including increased exfoliation of spermatogenic cells, degeneration of early spermatogenic cells, vacuolation of Sertoli cells, a decreased number of spermatogonia/spermatocytes/spermatids, along with a high number of apoptotic cells. In addition, the testis exhibited reduced glutathione (GSH) levels and glutathione reductase (GR) activity and enhanced malondialdehyde (MDA) concentration. Meanwhile, CD exposure exacerbated testicular histopathological alterations induced by CP. CD exposure also aggravated oxidative damage by increasing the lipid peroxidative product MDA and decreasing GSH levels and antioxidant enzyme activities in the testis. These results suggest that CD exposure exacerbates CP-induced testicular toxicity in mice, which might be attributed to the induction of lipid peroxidation and reduced antioxidant activity.

Rooster frozen-thawed semen quality following sublethal xanthine oxidase treatments

Reactive oxygen species are associated with cryodamage and may be a factor causing or exacerbating cellular cryodamage during freezing and thawing processes. Induction of sublethal oxidative stress as a new approach for preconditioning of sperm improves the cryo-resistance of sperm. The aim of this study was to investigate effects of sublethal concentrations of xanthine oxidase (XO), which induces oxidative stress before cryopreservation on values for semen quality variables of rooster sperm post-thawing. Semen samples were collected from 15 roosters and treated with different concentrations of XO [XO-0, XO-0.005, XO-0.05, XO-0.5, XO-5, and XO-50 U/ml]; then, the effects of treatments with XO as sublethal stressors, were examined. Results indicated the XO-0.5 and XO-5 treatments resulted in a greater percentage of sperm total motility, progressive motility, viability, and membrane functionality compared to other groups. There was no difference after treatments with XO-0, XO-0.005, and XO-0.05 on sperm total motility, membrane functionality, apoptosis, mitochondria activity, and viability. There was a greater percentage of mitochondria activity in sperm of the XO-0.05, XO-0.5, and XO-5 groups. Furthermore, there was the greatest concentration of malondialdehyde (MDA) in samples of the XO-50 group. Values for sperm abnormal morphology, acrosome integrity, and DNA fragmentation were not different among samples post-thawing. Sperm treated with XO-0.5 and XO-5 had a greater fertilization capacity than those of the control group. In conclusion, treatment of sperm with 0.5 and 5 U/ml XO as inducers of mild oxidative stress before cryopreservation, improved several function quality indices of sperm post-thawing.

Differences in the proteome of stallion spermatozoa explain stallion-to-stallion variability in sperm quality post-thaw†

The identification of stallions and or ejaculates that will provide commercially acceptable quality post-thaw before cryopreservation is of great interest, avoiding wasting time and resources freezing ejaculates that will not achieve sufficient quality to be marketed. Our hypothesis was that after bioinformatic analysis, the study of the stallion sperm proteome can provide discriminant variables able to predict the post-thaw quality of the ejaculate. At least three ejaculates from 10 different stallions were frozen following a split sample design. Half of the ejaculate was analyzed as a fresh aliquot and the other half was frozen and then analyzed as a frozen-thawed aliquot. Computer-assisted sperm analysis and flow cytometry were used to analyze sperm quality. Detailed proteomic analysis was performed on fresh and frozen and thawed aliquots, and bioinformatic analysis was used to identify discriminant variables in fresh samples able to predict the outcome of cryopreservation. Those with a fold change > 3, a P = 8.2e-04, and a q = 0.074 (equivalent to False discovery rate (FDR)) were selected, and the following proteins were identified in fresh samples as discriminant variables of good motility post-thaw: F6YTG8, K9K273, A0A3Q2I7V9, F7CE45, F6YU15, and F6SKR3. Other discriminant variables were also identified as predictors of good mitochondrial membrane potential and viability post-thaw. We concluded that proteomic approaches are a powerful tool to improve current sperm biotechnologies.

Pre-conditioning with Xanthine oxidase to improve post thawed quality of bull sperm

The purpose of this study was to examine the effects of sub-lethal concentration of Xanthine oxidase (XO) on the post-thawed bull sperm quality. Semen samples were collected from four Holstein bulls, twice a week and during three consecutive weeks (n = 24 total ejaculates). After collection in each replicate, semen samples were pooled and then frozen by semen extender containing different concentrations [0 (XO-0), 0.05 (XO-0.05), 0.5 (XO-0.5), 5 (XO-5), 50 (XO-50) and 500 (XO-500) μM] of XO. After thawing, motion parameters (SCA), plasma membrane functionality (HOST), apoptosis status (Phosphatidylserine translocation assay), mitochondrial activity (Rhodamine 123), and acrosome integrity (PSA), were evaluated. The results showed that total motility, VAP, VSL, VCL, STR, and LIN were lower in XO-50 and XO-500 compared to other groups (P < 0.05). Progressive motility were higher in XO-0.05 and XO-0.5 compared to XO-0, XO-50, and XO-500 (P < 0.05). Mitochondrial activity was highest in XO-0.05 and XO-0.5 groups. Sperm plasma membrane functionality was significantly greater in XO-0, XO-0.05, XO-0.5, and XO-5 than that of XO-50 and XO-500. Xanthine oxidase had not significant effects on acrosome integrity and dead spermatozoa. Higher percentage of live spermatozoa was recorded for XO-0, XO-0.05, XO-0.5, and XO-5; however, the lower amount of apoptotic spermatozoa was detected in the aforementioned groups (P < 0.05). In conclusion, it seems that XO at lower doses may have beneficial effects on post-thawed bull sperm quality.