Binder of Sperm Proteins 1 and 5 have contrasting effects on the capacitation of ram spermatozoa

Combined addition of L-carnitine and L-proline improves cryopreservation of dairy goat semen

Cryopreservation of semen renders artificial insemination easier and cheaper compared to use of fresh semen. However, the cellular oxidative stress, toxicity of cryoprotectants, and osmotic imbalance may lead to a decline in semen quality and fertilization ability during the process of cryopreservation. L-carnitine and L-proline have been demonstrated to possess effective antioxidant properties in cryopreservation, with the latter also exhibiting excellent permeability and thus being utilized as a permeable cryoprotectant in the field. The aim of this study was to investigate the effects of LC and LP on cryopreservation of semen of dairy goats. After thawing, sperm motility, membrane integrity, and acrosome integrity rate of cryopreserved semen treated with LC (50 mM) were significantly higher compared to the untreated control samples. Based on this premise, we conducted experiments to assess the cryoprotective efficacy of different concentrations of LP. The findings demonstrated that the inclusion of 50 mM LP resulted in improved sperm motility compared to other concentrations. Furthermore, the levels of damaging reactive oxygen species and the malonyldialdehyde marker for oxidative stress were significantly lower in goat semen treated with these concentrations of LC and LP compared to semen exposed to other treatments. Semen treated with LC and LP also exhibited good fertilization ability during both in vitro fertilization and artificial insemination. Thus, LC (50 mM) and LP (50 mM) improve cryoprotection of dairy goat sperm which suggests that addition of these compounds will be highly beneficial to the development of dairy goat breeding.

Molecular insights to the sperm-cervix interaction and the consequences for cryopreserved sperm

Cryopreserved ram spermatozoa are limited in their capacity to traverse the ovine cervix and achieve fertilization. This altered interaction may be related to modified molecular communication between frozen-thawed ram spermatozoa, seminal plasma, and the female tract. As such, this review aims to identify the biological processes which underpin sperm maturation and transport throughout the female reproductive tract to elucidate factors which may alter this natural process in cryopreserved ram spermatozoa. We also assess critical barriers to ram spermatozoa specific to the ovine cervix and the role of seminal plasma in mitigating these barriers. Transcriptomics is explored as a new approach to understand the sperm-cervix interaction. Recent studies have demonstrated that both spermatozoa and seminal plasma contain a complex profile of coding and non-coding RNAs. These molecular species have clear links with functional fertility, and mounting evidence suggests they may be altered by cryopreservation. Emerging in vitro cell culture models are also investigated as a "next step" in studying this interaction, utilizing transcriptomics to identify subtle changes in female tract gene expression in response to spermatozoa. The application of such models is proposed as an exciting opportunity to investigate the unique challenges faced by cryopreserved spermatozoa traversing the ovine cervix prior to fertilization.

Reproductive biology research down under: highlights from the Australian and New Zealand Annual Meeting of the Society for Reproductive Biology, 2021

Against the backdrop of a global pandemic, the Society for Reproductive Biology (SRB) 2021 meeting reunited the Australian and New Zealand reproductive research community for the first time since 2019 and was the first virtual SRB meeting. Despite the recent global research disruptions, the conference revealed significant advancements in reproductive research, the importance of which span human health, agriculture, and conservation. A core theme was novel technologies, including the use of medical microrobots for therapeutic and sperm delivery, diagnostic hyperspectral imaging, and hydrogel condoms with potential beyond contraception. The importance of challenging the contraceptive status quo was further highlighted with innovations in gene therapies, non-hormonal female contraceptives, epigenetic semen analysis, and in applying evolutionary theory to suppress pest population reproduction. How best to support pregnancies, particularly in the context of global trends of increasing maternal age, was also discussed, with several promising therapies for improved outcomes in assisted reproductive technology, pre-eclampsia, and pre-term birth prevention. The unique insights gained via non-model species was another key focus and presented research emphasised the importance of studying diverse systems to understand fundamental aspects of reproductive biology and evolution. Finally, the meeting highlighted how to effectively translate reproductive research into policy and industry practice.

HDL mediates reverse cholesterol transport from ram spermatozoa and induces hyperactivated motility

Reverse cholesterol transport or cholesterol efflux is part of an extensive plasma membrane remodeling process in spermatozoa that is imperative for fertilization. For ram spermatozoa, sheep serum is well known to support in vitro fertilization (IVF), but knowledge of its explicit role is limited. Though, it is postulated to elicit cholesterol efflux owing to the presence of high-density lipoproteins (HDLs) that interact with transmembrane cholesterol transporters, such as adenosinetriphosphate (ATP)-binding cassette transporter A1 (ABCA1) and scavenger receptor class B, type I (SR-BI). In this study, we report that both sheep serum and HDLs were able to elicit cholesterol efflux alone by up to 20–40% (as measured by the boron dipyrromethene (BODIPY)-cholesterol assay). Furthermore, when the antagonists glibenclamide and valspodar were used to inhibit the function of ABCA1 and SR-BI or ABCA1 alone, respectively, cholesterol efflux was only marginally reduced (8–15%). Nevertheless, it is likely that in ram spermatozoa, a specific facilitated pathway of cholesterol efflux is involved in the interaction between cholesterol acceptors and transporters. Interestingly, exposure to HDLs also induced hyperactivated motility, another critical event required for successful fertilization. Taken together, this study details the first report of the dual action of HDLs on ram spermatozoa, providing both an insight into the intricacy of events leading up to fertilization in vivo as well as demonstrating the possible application of HDL supplementation in media for IVF.

Melatonin improves the motility and DNA integrity of frozen-thawed ram spermatozoa likely via suppression of mitochondrial superoxide production

The ability of the neurohormone melatonin to ameliorate cryopreservation-induced damage to spermatozoa has been demonstrated in several domestic species. However, it is unclear how these protective effects are conferred, with improvements in sperm quality ambiguously attributed to the general antioxidant activity of melatonin. To further investigate this phenomenon, ram spermatozoa were diluted in cryomedia with and without melatonin (0 [control], 0.1, 1, 10, and 100 μM) and assessed for motility, viability, DNA integrity, mitochondrial superoxide production, lipid peroxidation, and intracellular reactive oxygen species before freezing and after thawing (0, 3, and 6 h post-thaw). Before freezing, supplementation with melatonin at any concentration had no effect on any measure of sperm quality. However, post-thaw, spermatozoa frozen in the presence of any level of melatonin reduced mitochondrial superoxide production of spermatozoa (P < 0.001), decreased the level of sperm DNA fragmentation (P < 0.001), and increased the percentage of motile spermatozoa (P = 0.035). Melatonin supplementation did not influence the relative levels of lipid peroxidation in the sperm membrane, the levels of intracellular reactive oxygen species, or sperm membrane lipid disorder (P > 0.05). There was no difference in the percentage of viable spermatozoa between treatment groups pre- or post-freeze (P > 0.05). These results suggest that, in the ram, melatonin does not protect the quality of cryopreserved spermatozoa through a nondiscerning scavenging of reactive oxygen species as previously suggested. Rather, melatonin appears to specifically reduce mitochondrial superoxide production, altering sperm functionality, as opposed to merely increasing the percentage of live sperm.

Mapping the major proteome of reproductive fluids and sperm membranes of rams: From the cauda epididymis to ejaculation

The present study evaluated the major proteome of ram seminal plasma and the main secretions that contribute to its formation, such as the cauda epididymal and accessory sex gland fluids. The study also investigated sperm membrane protein profiles before and after ejaculation. First, semen was collected from six rams (using artificial vagina) to obtain seminal plasma and ejaculated sperm. Then, rams were vasectomized for collection of accessory sex gland fluid (using artificial vagina). Next, rams were slaughtered and cauda epididymal fluid (CEF), seminal vesicle fluid, bulbourethral gland fluid and cauda epididymal sperm were properly collected. Proteins from reproductive fluids and sperm membranes were analyzed by 2-D SDS-PAGE, tandem mass spectrometry and bioinformatics. There we 386 proteins and 256 isoforms identified in all samples. The most abundant seminal plasma proteins were BSP1, BSP5 and spermadhesins (bodhesin-2 and spermadhesin Z13-like). These proteins were present in similar patterns in maps of accessory sexgland fluid, with very low quantities in the CEF and absent in the bulbourethral gland secretion. Thus, practically all BSPs and spermadhesins come from seminal vesicles. Bulbourethral gland fluid brought bactericidal/permeability-increasing protein-containing Family A member 1 isoforms, superoxide dismutase [Cu-Zn] and betamicroseminoprotein to seminal plasma. CEF was the major provider of clusterin, epididymal-specific lipocalin-5-like isoform, epididymal secretory gluthathione peroxidase, epididymal secretory protein E1 and prostaglandin-H2 D-isomerase to seminal plasma. Albumin came from all reproductive fluids. BSPs and spermadhesins were present in 2-D maps of ejaculated sperm but absent in cauda epididymal sperm. These proteins come from the seminal vesicles and bind to sperm at the moment of ejaculation. Other proteins of ejaculated and epididymal sperm membranes were mostly associated to energy production, cell adhesion and proteolytic activity (ATP synthases, disintegrin, metalloproteinase domain-containing protein 32, carboxypeptidase Q and cytosol aminopeptidase). In conclusion, there is a well-orchestrated sequence of events to form the major seminal plasma proteome, with specific contributions from cauda epididymis, seminal vesicles and bulbourethral glands. The present data contribute to a better understanding of male reproductive biology and how sperm functions are affected by the noncellularmicro environment of semen.

Bovine sperm-oviduct interactions are characterized by specific sperm behaviour, ultrastructure and tubal reactions which are impacted by sex sorting

To date sperm-oviduct interactions have largely been investigated under in vitro conditions. Therefore we set out to characterize the behaviour of bovine spermatozoa within the sperm reservoir under near in vivo conditions and in real-time using a novel live cell imaging technology and a newly established fluorescent sperm binding assay. Sperm structure and tubal reactions after sperm binding were analysed using scanning and transmission electron microscopy and histochemistry. As a model to specify the impact of stress on sperm-oviduct interactions, frozen-thawed conventional and sex-sorted spermatozoa from the same bulls (n = 7) were co-incubated with oviducts obtained from cows immediately after slaughter. Our studies revealed that within the oviductal sperm reservoir agile (bound at a tangential angle of about 30°, actively beating undulating tail), lagging (bound at a lower angle, reduced tail movement), immotile (absence of tail movement) and hyperactivated (whip-like movement of tail) spermatozoa occur, the prevalence of which changes in a time-dependent pattern. After formation of the sperm reservoir, tubal ciliary beat frequency is significantly increased (p = 0.022) and the epithelial cells show increased activity of endoplasmic reticula. After sex sorting, spermatozoa occasionally display abnormal movement patterns characterized by a 360° rotating head and tail. Sperm binding in the oviduct is significantly reduced (p = 0.008) following sexing. Sex-sorted spermatozoa reveal deformations in the head, sharp bends in the tail and a significantly increased prevalence of damaged mitochondria (p < 0.001). Our results imply that the oviductal cells specifically react to the binding of spermatozoa, maintaining sperm survival within the tubal reservoir. The sex-sorting process, which is associated with mechanical, chemical and time stress, impacts sperm binding to the oviduct and mitochondrial integrity affecting sperm motility and function.

The biological mechanisms regulating sperm selection by the ovine cervix

In species where semen is deposited in the vagina, the cervix has the unique function of facilitating progress of spermatozoa towards the site of fertilisation while also preventing the ascending influx of pathogens from the vagina. For the majority of species, advances in assisted reproduction techniques facilitate the bypassing of the cervix and therefore its effect on the transit of processed spermatozoa has been largely overlooked. The exception is in sheep, as it is currently not possible to traverse the ovine cervix with an inseminating catheter due to its complex anatomy, and semen must be deposited at the external cervical os. This results in unacceptably low pregnancy rates when frozen-thawed or liquid stored (>24 h) semen is inseminated. The objective of this review is to discuss the biological mechanisms which regulate cervical sperm selection. We assess the effects of endogenous and exogenous hormones on cervical mucus composition and discuss how increased mucus production and flow during oestrus stimulates sperm rheotaxis along the crypts and folds of the cervix. Emerging results shedding light on the sperm-cervical mucus interaction as well as the dialogue between spermatozoa and the innate immune system are outlined. Finally, ewe breed differences in cervical function and the impact of semen processing on the success of fertilisation, as well as the most fruitful avenues of further investigation in this area are proposed.

Untargeted metabolomic profiling of accessory sex gland fluid from Morada Nova rams

The present study was conducted to characterize the metabolome of accessory gland fluid (AGF) of locally adapted Morada Nova rams, raised in the Brazilian Northeast. AGF was collected by an artificial vagina from five vasectomized rams. Metabolites were identified by gas chromatography-mass spectrometry (GC/MS) and high-performance liquid chromatography-mass spectrometry (LC/MS), with the support of Human Metabolome Database, PubChem, LIPID Metabolites, Pathways Strategy databases, and MetaboAnalyst platforms. There were 182 and 190 metabolites detected by GC/MS and LC/MS, respectively, with an overlap of one molecule. Lipids and lipid-like molecules were the most abundant class of metabolites in the ram AGF (127 compounds), followed by amino acids, peptides, and analogs(103 metabolites). Considering all GC/MS and LC/MS, fructose, glycerol, citric acid, d-mannitol, d-glucose, and l-(+)-lactic acid were the most abundant single metabolites present in the ram AGF. Meaningful pathways associated with AGF metabolites included glycine, serine and threonine metabolism; pantothenate and CoA biosynthesis; galactose metabolism; glutamate metabolism and phenylalanine metabolism, and so forth. In conclusion, the combined use of LC/MS and GC/MS was essential for getting a holistic view of the compounds embedded in the ram AGF. Chemical analysis of the accessory sex gland secretion is relevant for understanding sperm function and fertilization.

Sperm surface changes and their consequences for sperm transit through the female reproductive tract

Spermatozoa are faced with considerable challenges during their passage through the female reproductive tract. Following deposition, they must deal with several physical and biochemical barriers as well as an aggressive immune defence system before they reach the site of fertilisation. While many factors are at play, the surface characteristics of spermatozoa are central to communication with the female and successful transit. The surface proteome of spermatozoa has been extensively studied and shown to vary considerably between species that deposit semen in the vagina (ram and bull) and uterus (boar and stallion), likely due to major differences in accessory sex gland anatomy. Comparing the surface characteristics of spermatozoa from these domestic species and how individual components may equip spermatozoa to interact with different features of the female tract could help understand how spermatozoa navigate from vagina or uterus to oviduct ampulla. Furthermore, we can begin to explain why use of high quality preserved spermatozoa in artificial insemination programs may still result in reduced fertility due to altered interaction with the female. In this review, we describe the sperm surface characteristics of the ram, bull, boar and stallion and compare changes as a result of mixture with seminal plasma and/or in vitro processing. The role of these seminal components in facilitating sperm survival and transit within the female reproductive tract is summarised, drawing attention to potential implications for applied reproductive technologies.

Epididymal and ejaculated sperm differ on their response to the cryopreservation and capacitation processes in mouflon (Ovis musimon)

Spermatozoa must undergo the process of capacitation to fertilize the egg which involves a cell destabilizing process. Capacitation-like changes such as protein tyrosine phosphorylation (PTP) are associated with cryopreservation. The aim of this study was to compare the cryoresistance and capacitation response of epididymal and ejaculated sperm of European mouflon (Ovis musimon). Post-thaw sperm parameters were analysed from epididymal and ejaculated samples cryopreserved by slow-freezing or ultrarapid-freezing for comparison. Sperm capacitation status was assessed by the semiquantification of PTP levels, cell localization of PTP and kinematic clustering. Epididymal sperm had higher cryoresistance than ejaculated sperm in both freezing techniques, and slow-freezing rendered better results than ultrarapid-freezing in both sperm samples. Ejaculated sperm had higher PTP levels than epididymal sperm and, additionally, ejaculated sperm showed higher phosphorylation in capacitating (CA) than in non-capacitating (NCA) conditions while there was no effect of medium in epididymal sperm. There was a higher tail PTP in CA than in NCA conditions in both types of sperm. Kinematic analysis revealed that the cluster associated with hyperactivated movement increased in ejaculated sperm incubated in CA whereas no effect of medium was observed in epididymal sperm clusters. In conclusion, epididymal sperm showed better freezability and lower capacitation status compared to ejaculated sperm.

The fate of spermatozoa in the female reproductive tract: A comparative review

The journey that spermatozoa take following deposition in the female tract is a long and perilous one. The barriers they face within the female tract differ depending on whether they are deposited in the vagina or uterus, like spermatozoa of the ram or boar respectively. Comparative studies on the transit of spermatozoa through the ewe and sow tracts serves to highlight similarities, or differences, in the way their sperm-surface properties enable them to overcome these barriers, progress through the tract and fertilise the oocyte. The female environment contributes towards this successful transit by providing a vehicle for sperm transport, aiding the removal of dead spermatozoa and other pathogens and applying strict selection pressures to ensure only those cells with the highest quality reach the site of fertilisation. Understanding the criteria behind these natural barriers helps an understanding of the limitations to fertility associated with preserved spermatozoa, and how in vitro manipulation can alter this complex interaction between spermatozoa and the female environment. Similar mechanisms or surface coat interactions exist in both species, but each has evolved to be used for physiologically disparate functions. Here we briefly describe the sperm surface characteristics of both fresh and frozen-thawed boar and ram spermatozoa and compare how these properties equip them to survive the physical, biochemical and immune interactions within the female reproductive tract.

Novel methods to detect capacitation-related changes in spermatozoa

Prior to interaction with the oocyte, spermatozoa must undergo capacitation, which involves a series of physio-chemical transformations that occur in the female tract. As capacitation is a pre-requisite for successful fertilisation, it is a topic of great interest for sperm biologists, but the complexity of the numerous biochemical and biophysical processes involved make it difficult to measure. Capacitation is an extremely complex event that encompasses numerous integrated processes that can occur concurrently during this window of time. The identification of techniques to accurately assess and quantify capacitation is therefore crucial to gain a meaningful insight into this fascinating sperm maturation event. Whilst there are extensive reviews in the literature that focus on the functional changes to spermatozoa during capacitation, few have examined the methods required to measure these changes. The aim of this review is to highlight frequently used methods to quantify different stages of capacitation and identify promising novel techniques. Factors that are able to modulate various capacitation processes will also be discussed. The overall outcome is to provide researchers with a toolbox of methods that can be used to gain a deeper understanding of the intricacies of capacitation in spermatozoa.

Seminal plasma proteins as markers of sperm fertility

During ejaculation and deposition in the female genital tract, spermatozoa are exposed to seminal plasma, a mix of secretions primarily from the accessory sex glands. Proteins, which make up the largest contribution to seminal plasma by weight, have been the focus of much interest, in particular the identification of specific proteins both in the plasma and/or found bound to the sperm surface post ejaculation. Global proteomic studies of seminal plasma originating from a range of species over the last 15 years have revealed their hitherto unknown diversity and complexity. Seminal plasma is generally known to aid sperm survival and fertility in a range of species and studies have begun to reveal its link with sperm function and identification, as markers of fertility. This review summarises recent data on proteins found on the sperm surface that originate from seminal plasma and have subsequently been shown to correlate with fertility, with a focus on the pig.

Lycium barbarum and Laminaria japonica polysaccharides improve Cashmere goat sperm quality and fertility rate after cryopreservation

Cashmere goat is known for the highest cashmere yield and best fiber quality. Here, the effects of Lycium barbarum polysaccharide (LBP) and Laminaria japonica polysaccharide (LJP) on goat sperm quality were investigated. Results showed that the sperm motility, mitochondrial activity, and membrane and acrosome integrity were significantly higher with 4.0 mg/mL LBP and 1.0 mg/mL LJP supplementations than in the control (P < 0.05), respectively. Higher SOD, CAT, and GSH-Px levels were observed in 4.0 mg/mL LBP and 1.0 mg/mL LJP groups than control group (P < 0.05). Sperm characteristics with 2.0 + 1.0 mg/mL LBP + LJP supplementation significantly improved compared to that with other treatments (P < 0.05). Compared to the control treatment, the non-return rate (NRR) were higher in the LBP + LJP (2.0 + 1.0 mg/mL) group (P < 0.05). These results suggest that LBP and LJP enhance cryo-protective effects on goat spermatozoa, and that 2.0 + 1.0 mg/mL LBP + LJP addition to the extender during cryopreservation is beneficial to the Cashmere goat breeding industry.

Major seminal plasma proteome of rabbits and associations with sperm quality

The present study was conducted to describe the major seminal plasma proteome of rabbits and potential associations between seminal proteins and semen criteria. Semen samples were collected from 18 New Zealand adult rabbits, and seminal plasma proteins were analyzed by 2-D SDS-PAGE and tandem mass spectrometry. Sperm motility, vigor, concentration, morphology and membrane sperm viability were evaluated. Rabbits ejaculated 364 ± 70 million sperm/ml, with 81 ± 6.1% motile cells, 3.8 ± 0.2 vigor and 66.7 ± 2.5% sperm with normal morphology. Based on the viability and acrosome integrity assay, there were 65.8 ± 2.5% live sperm with intact acrosome and most spermatozoa had both intact acrosome and functional membrane. On average, 2-D gels of rabbit seminal plasma had 232 ± 69.5 spots, as determined by PDQuest software (Bio Rad, USA). Mass spectrometry allowed the identification of 137 different proteins. The most abundant proteins in rabbit seminal plasma were hemoglobin subunit zeta-like, annexins, lipocalin, FAM115 protein and albumin. The intensity of the spots associated with these five proteins represented 71.5% of the intensity of all spots detected in the master gel. Multiple regression models were estimated using sperm traits as dependent variables and seminal plasma proteins as independent ones. Also, sperm motility had positive association with beta-nerve growth factor and cysteine-rich secretory protein 1-like and a negative one with galectin-1. The percentage of rabbit sperm with intact membrane was related to seminal plasma protein FAM115 complex and tropomyosin. Then, the population of morphologically normal sperm in rabbit semen was positively linked to carcinoembryonic antigen-related cell adhesion molecule 6-like and down regulated by seminal plasma isocitrate dehydrogenase. Based on another regression model, the variation in the percentage of live sperm with intact acrosome was partially explained by the amount of leukocyte elastase inhibitor and the peptidyl-prolyl cis-trans isomerase A in the rabbit seminal fluid. The current study reports the identification of 137 proteins of rabbit seminal plasma. Major proteins of seminal secretion relate primarily to prevention of damages caused by lipid peroxide radicals and oxidative stress, membrane functionality, transport of lipids to the sperm membrane and temperature regulation. Moreover, finding seminal plasma proteins as indicators of semen parameters will improve assisted reproductive technologies.