Proteomic analyses identify differences between bovine epididymal and ejaculated spermatozoa that contribute to longevity

A longer period of epididymal sperm interaction with extender components during cryopreservation improves sperm quality, decreases the size of sperm distal cytoplasmic droplets, and changes the number of nanoparticles in the extender

While cryopreservation of cauda epididymal sperm (SpCau) allows the preservation of post-mortem bulls' gametes, the process triggers sperm damage. Although improving post-thaw sperm quality, using egg yolk extenders (EY) raises biosafety concerns which forces the use of EY-free extenders (EYFE). Since EYFE are less efficient in preserving post-thaw sperm quality, a strategy for ejaculated sperm (SpEj) frozen with EYFE is to add an Equilibrium Time (ET) step period to the cryopreservation process. However, the ET effect on the quality of SpCau cryopreserved in EYFE remains unknown. Distinct from SpEJ, SpCau physiologically displays cytoplasmic droplets (CDs) in the flagellum that may benefit cell exchange during ET. We hypothesized that using ET in SpCau cryopreserved with EYFE impacts sperm morphofunctional features, CD area, and in vitro fertility ability. Extender nanoparticles were also assessed. Following collection from the cauda epididymis of six Nellore bulls by retrograde flow, SpCau were cryopreserved in EYFE BoviFree® (Minitube, Germany) using three ET protocols: ET0 (no-ET); ET2.5 (2.5 h-ET); and ET5 (5 h-ET). SpCau from ET2.5 and ET5 showed a higher (P ≤ 0.05) percentage of motility and integrity of plasma and acrosome membranes and a smaller (P ≤ 0.05) distal CD area. There are no differences in sperm abnormalities, oxidative stress, capacitation-like events, and in vitro fertility ability. However, a better sperm recovery was found after Percoll® selection for ET2.5 and ET5. Interestingly, the number of nanoparticles in the extender decreased in post-thawed samples. In conclusion, an ET of 2.5 or 5 h is required for an efficient SpCau cryopreservation using an EYFE.

Proteomic analysis of boar sperm with differential ability of liquid preservation at 17 °C

Understanding the liquid preservation ability of boar sperm is pivotal for efficient management and breeding of livestock. Although sperm proteins play an important role in semen quality and freezability, how the levels of protein change in boar sperm with different liquid preservation abilities at 17 °C remains unclear. In this study, two groups of boar sperm with extreme difference in liquid preservation ability, namely the good preservation ability (GPA) and the poor preservation ability (PPA) groups, were selected by evaluating sperm motility parameters on the 7th day of liquid preservation at 17 °C. Quantitative proteomics based on tandem mass tag (TMT) labeling was used, sperm proteomic characteristics from two groups were analyzed, and potentially key proteins related to the fluid preservation ability of sperm were identified. A total of 187 differentially expressed proteins (DEPs) were identified among 2791 quantified proteins, including 85 upregulated, and 102 downregulated proteins. Further, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses of the DEPs revealed that they were enriched in GO terms associated with response to oxidative stress, enzyme activity related to oxidative stress or redox reactions, and several metabolic activities. The significant KEGG pathways included peroxisome, metabolic pathways, selenocompound metabolism, and collection duct acid secretion. In addition, analysis of protein-protein interactions further identified 8 proteins that could be used as biomarker candidates, including GPX5, GLRX, ENO4, QPCT, BBS7, OXSR1, DHRS4 and AP2S1, which may play an essential role in indicating the liquid preservation ability of boar sperm. These findings in this study provide new insights into the underlying molecular mechanisms of the liquid preservation ability of boar sperm. Moreover, the selected candidate proteins can serve as a reference for evaluating sperm quality or preservation ability in boars and their application in related biotechnologies.

Review: The role of male reproductive tract secretions in ruminant fertility

Male fertility largely depends on the ability to produce sperm that can transmit the paternal information onto the next generation. However, the factors that are critical for sperm function and the subsequent development of healthy offspring are still not completely understood in ruminants. Importantly, sperm function is not completely encoded by germ cell DNA, but rather, depends on sequential acquisition, loss, and modification of elements through interaction with secretions from the testes, epididymides, and accessory glands (collectively termed seminal plasma). In addition, these secretions can play a role in the inheritance of paternal environmental effects by progeny. This is likely achieved directly, by the regulation of sperm epigenetic effectors, and indirectly, by altering the female environment in which the individual develops. This review will provide an overview of the different organs that contribute to seminal plasma in ruminants, and summarise how their secretions shape sperm function and modulate the female reproductive tract. Finally, some consideration will be given to the potential of paternal factors to affect embryo development and offspring health in ruminants.

Proteomics dataset of epididymal fluid, seminal plasma, and proteins loosely attached to epididymal and ejaculated sperm from Angus bulls

Peptides and proteins were identified by liquid chromatography with tandem mass spectrometry analysis (LCMS-MS) on an Orbitrap Velos mass spectrometer to further understand biological mechanisms that regulate increased longevity in epididymis compared to ejaculated sperm. Semen from sexually mature bulls were collected and then bulls were slaughtered to collect epididymal samples from the cauda epididymis. All samples were centrifuged to separate spermatozoa from fluids. A high ionic solution was used to remove surface proteins from spermatozoa. Four unique samples were generated: (1) epididymal fluid, (2) seminal plasma (ejaculated fluid), and proteins stripped from (3) epididymal sperm, and (4) ejaculated sperm. Samples were analyzed by LCMS-MS, and data were interpreted with Protein Pilot 5. False discovery rate (FDR) was set at 1%. Unique proteins (n = 458) were identified in ejaculated samples, 178 proteins in seminal plasma and 298 proteins stripped from ejaculated sperm. In epididymal samples, 311 proteins were identified in the fluid, and 334 were identified among proteins stripped from epididymal sperm. This dataset can be useful for further understand of biological mechanisms that control sperm longevity. This dataset is related to the article ‘Proteomic analyses identify differences between bovine epididymal and ejaculated spermatozoa that contribute to longevity’ by (Zoca et al., 2022).