Bicarbonate-induced membrane processing in sperm capacitation

Lipid remodeling in acrosome exocytosis: unraveling key players in the human sperm

It has long been thought that exocytosis was driven exclusively by well-studied fusion proteins. Some decades ago, the role of lipids became evident and escalated interest in the field. Our laboratory chose a particular cell to face this issue: the human sperm. What makes this cell special? Sperm, as terminal cells, are characterized by their scarcity of organelles and the complete absence of transcriptional and translational activities. They are specialized for a singular membrane fusion occurrence: the exocytosis of the acrosome. This unique trait makes them invaluable for the study of exocytosis in isolation. We will discuss the lipids' role in human sperm acrosome exocytosis from various perspectives, with a primary emphasis on our contributions to the field. Sperm cells have a unique lipid composition, very rare and not observed in many cell types, comprising a high content of plasmalogens, long-chain, and very-long-chain polyunsaturated fatty acids that are particular constituents of some sphingolipids. This review endeavors to unravel the impact of membrane lipid composition on the proper functioning of the exocytic pathway in human sperm and how this lipid dynamic influences its fertilizing capability. Evidence from our and other laboratories allowed unveiling the role and importance of multiple lipids that drive exocytosis. This review highlights the role of cholesterol, diacylglycerol, and particular phospholipids like phosphatidic acid, phosphatidylinositol 4,5-bisphosphate, and sphingolipids in driving sperm acrosome exocytosis. Furthermore, we provide a comprehensive overview of the factors and enzymes that regulate lipid turnover during the exocytic course. A more thorough grasp of the role played by lipids transferred from sperm can provide insights into certain causes of male infertility. It may lead to enhancements in diagnosing infertility and techniques like assisted reproductive technology (ART).

Navigating the Intersection of Glycemic Control and Fertility: A Network Perspective

The rising incidence of metabolic diseases is linked to elevated blood glucose levels, contributing to conditions such as diabetes and promoting the accumulation of advanced glycation end products (AGEs). AGEs, formed by non-enzymatic reactions between sugars and proteins, build up in tissues and are implicated in various diseases. This article explores the relationship between glycemic control and AGE accumulation, focusing on fertility implications. A computational model using network theory was developed, featuring a molecular database and a network with 145 nodes and 262 links, categorized as a Barabasi-Albert scale-free network. Three main subsets of nodes emerged, centered on glycemic control, fertility, and immunity, with AGEs playing a critical role. The transient receptor potential vanilloid 1 (TRPV1), a receptor expressed in several tissues including sperm, was identified as a key hub, suggesting that the modulation of TRPV1 in sperm by AGEs may influence fertility. Additionally, a novel link between glycemic control and immunity was found, indicating that immune cells may play a role in endocytosing specific AGEs. This discovery underscores the complex interplay between glycemic control and immune function, with significant implications for metabolic, immune health, and fertility.

Metabolic Shift in Porcine Spermatozoa during Sperm Capacitation-Induced Zinc Flux

Mammalian spermatozoa rely on glycolysis and mitochondrial oxidative phosphorylation for energy leading up to fertilization. Sperm capacitation involves a series of well-regulated biochemical steps that are necessary to give spermatozoa the ability to fertilize the oocyte. Additionally, zinc ion (Zn2+) fluxes have recently been shown to occur during mammalian sperm capacitation. Semen from seven commercial boars was collected and analyzed using image-based flow cytometry before, after, and with the inclusion of 2 mM Zn2+ containing in vitro capacitation (IVC) media. Metabolites were extracted and analyzed via Gas Chromatography-Mass Spectrometry (GC-MS), identifying 175 metabolites, with 79 differentially abundant across treatments (p < 0.05). Non-capacitated samples showed high levels of respiration-associated metabolites including glucose, fructose, citric acid, and pyruvic acid. After 4 h IVC, these metabolites significantly decreased, while phosphate, lactic acid, and glucitol increased (p < 0.05). With zinc inclusion, we observed an increase in metabolites such as lactic acid, glucitol, glucose, fructose, myo-inositol, citric acid, and succinic acid, while saturated fatty acids including palmitic, dodecanoic, and myristic acid decreased compared to 4 h IVC, indicating regulatory shifts in metabolic pathways and fatty acid composition during capacitation. These findings underscore the importance of metabolic changes in improving artificial insemination and fertility treatments in livestock and humans.

A stallion spermatozoon's journey through the mare's genital tract: In vivo and in vitro aspects of sperm capacitation

Conventional in vitro fertilization is not efficacious when working with equine gametes. Although stallion spermatozoa bind to the zona pellucida in vitro, these gametes fail to initiate the acrosome reaction in the vicinity of the oocyte and cannot, therefore, penetrate into the perivitelline space. Failure of sperm penetration most likely relates to the absence of optimized in vitro fertilization media containing molecules essential to support stallion sperm capacitation. In vivo, the female reproductive tract, especially the oviductal lumen, provides an environmental milieu that appropriately regulates interactions between the gametes and promotes fertilization. Identifying these 'fertilization supporting factors' would be a great contribution for development of equine in vitro fertilization media. In this review, a description of the current understanding of the interactions stallion spermatozoa undergo during passage through the female genital tract, and related specific molecular changes that occur at the sperm plasma membrane is provided. Understanding these molecular changes may hold essential clues to achieving successful in vitro fertilization with equine gametes.

An optimized centrifugation protocol for ram sperm ensuring high sample yield, quality and fertility

The optimization and implementation of artificial insemination (AI) in sheep is necessary to increase the livestock productivity through enhanced control of reproductive function. Sperm centrifugation is a common procedure in the ejaculate handling in AI and other assisted reproductive technologies (ART), as part of new methods of sperm analysis, selection or preservation. However, our research group previously established that this simple procedure might cause a large sperm loss and induce deleterious effects on the sperm function of the ovine species when high centrifugation forces are employed. To our knowledge, there are no studies on combined effect of extender and different centrifugal forces on ram sperm yield and quality. Furthermore, evidence of in vivo fertility rate using sperm obtained with various centrifugation forces is also lacking in this species. Thus, the objective of this work was to define the ideal conditions for ram semen centrifugation that will achieve the best quantity and quality sample to ensure unaffected fertilization ability of centrifuged ram sperm. The Experiment 1 evaluated the effect of the centrifugation procedure of two extenders (INRA 96 and Tyrode's) and two cooling protocols (Rapid and Slow Refrigeration -35 °C to 15 °C-) on sperm recovery rate and quality (motility and kinetic parameters, viability, apoptosis and mitochondrial activity). INRA 96 combined with Slow Refrigeration and Tyrode's at room temperature registered the highest sperm recovery and quality values (P ≤ 0.05). In Experiment 2, the influence of three centrifugal forces (600, 1200 and 6000×g for 10 min) was assessed immediately after centrifugation on the technical performance and sperm functionality in diluted samples with INRA 96 and Tyrode's at the conditions set out in Experiment 1. The lowest pellet weight (P ≤ 0.05) without harmful effect on sperm physiological status (P > 0.05) was achieved at 1200×g, since 6000×g induced sperm motility damage (P ≤ 0.05) with both extenders. Finally, to ensure the total safety of the centrifugation protocol, Experiment 3 tested in a combined in vitro and in vivo test the effect of these three centrifugal forces on ram sperm quality after dilution (INRA 96) and liquid storage (6-8 h at 15 °C). The damage produced by 6000×g on sperm motility (P ≤ 0.05) was maintained over time, coinciding with a lower fertility (P ≤ 0.05). In conclusion, ram sperm can be centrifuged in INRA 96 extender up to 1200×g for 10 min at 15 °C as secure values with high recovery rates and without detrimental effects on sperm quality and fertility.

Capacitation promotes a shift in energy metabolism in murine sperm

In mammals, sperm acquire fertilization ability after a series of physiological and biochemical changes, collectively known as capacitation, that occur inside the female reproductive tract. In addition to other requirements, sperm bioenergetic metabolism has been identified as a fundamental component in the acquisition of capacitation. Mammalian sperm produce ATP through two main metabolic processes, oxidative phosphorylation (OXPHOS) and aerobic glycolysis that are localized to two different flagellar compartments, the midpiece, and the principal piece, respectively. In mouse sperm, the occurrence of many events associated with capacitation relies on the activity of these two energy-producing pathways, leading to the hypothesis that some of these events may impose changes in sperm energetic demands. In the present study, we used extracellular flux analysis to evaluate changes in glycolytic and respiratory parameters of murine sperm that occur as a consequence of capacitation. Furthermore, we examined whether these variations affect sperm ATP sustainability. Our results show that capacitation promotes a shift in the usage ratio of the two main metabolic pathways, from oxidative to glycolytic. However, this metabolic rewiring does not seem to affect the rate at which the sperm consume ATP. We conclude that the probable function of the metabolic switch is to increase the ATP supply in the distal flagellar regions, thus sustaining the energetic demands that arise from capacitation.

α/β-Hydrolase D16B Truncation Results in Premature Sperm Capacitation in Cattle

Recently it was shown that a specific form of male infertility in Holstein cattle was caused by a nonsense variant in the α/β-hydrolase domain-containing 16B (ABHD16B) gene resulting in a protein truncation at amino acid position 218 (p.218Q*) and loss of function. Lipidomics showed that the absence of ABHD16B influenced the content of phosphatidylcholine (PC), ceramide (Cer), diacylglycerol (DAG), and sphingomyelin (SM) in variant carrier sperm membranes. However, the exact cause of infertility in affected sires has remained unclear until now. To elucidate the cause of infertility, we analyzed (i) standard sperm parameters (i.e., total sperm number, morphological intact sperm, total sperm motility), (ii) in vitro fertilizability and effects on early embryonic development, and (iii) sperm survival rates (i.e., capacitation time). The affected spermatozoa showed no changes in the usual sperm parameters and were also capable of fertilization in vitro. Furthermore, the absence of ABHD16B did not affect early embryonic development. Based on these results, it was concluded that the affected spermatozoa appeared to be fertilizable per se. Consequently, the actual cause of the inability to fertilize could only be due to a time- and/or place-dependent process after artificial insemination and before fertilization. A process fundamental to the ability to fertilize after insemination is capacitation. Capacitation is a biochemical maturation process that spermatozoa undergo in the female genital tract and is inevitable for the successful fertilization of the oocyte. It is known that the presence and concentration of certain sperm membrane lipids are essential for the correct course of capacitation. However, precisely these lipids are absent in the membrane of spermatozoa affected by the ABHD16B truncation. Since all other causes of fertilization inability were excluded in the previous experiments, consequently, the only remaining hypothesis was that the loss of function of ABHD16B leads to a capacitation disruption. We were able to show that heterozygous and homozygous affected spermatozoa exhibit premature capacitation and therefore decay before fertilization. This effect of the loss of function of ABHD16B has not been described before and our studies now revealed why sires harboring the variant in the ABHD16B gene are infertile.

A Review on the Role of Bicarbonate and Proton Transporters during Sperm Capacitation in Mammals

Alkalinization of sperm cytosol is essential for plasma membrane hyperpolarization, hyperactivation of motility, and acrosomal exocytosis during sperm capacitation in mammals. The plasma membrane of sperm cells contains different ion channels implicated in the increase of internal pH (pH_i) by favoring either bicarbonate entrance or proton efflux. Bicarbonate transporters belong to the solute carrier families 4 (SLC4) and 26 (SLC26) and are currently grouped into Na⁺/HCO₃⁻ transporters and Cl⁻/HCO₃⁻ exchangers. Na⁺/HCO₃⁻ transporters are reported to be essential for the initial and fast entrance of HCO₃⁻ that triggers sperm capacitation, whereas Cl⁻/HCO₃⁻ exchangers are responsible for the sustained HCO₃⁻ entrance which orchestrates the sequence of changes associated with sperm capacitation. Proton efflux is required for the fast alkalinization of capacitated sperm cells and the activation of pH-dependent proteins; according to the species, this transport can be mediated by Na⁺/H⁺ exchangers (NHE) belonging to the SLC9 family and/or voltage-gated proton channels (HVCN1). Herein, we discuss the involvement of each of these channels in sperm capacitation and the acrosome reaction.

Bicarbonate-Triggered In Vitro Capacitation of Boar Spermatozoa Conveys an Increased Relative Abundance of the Canonical Transient Receptor Potential Cation (TRPC) Channels 3, 4, 6 and 7 and of CatSper-γ Subunit mRNA Transcripts

Simple Summary

The detection of sub-fertile boars has been a difficult task, and despite their prevalence being low, its impact is very significant because it implies economic drawbacks for artificial insemination (AI) centers and farms. Unfortunately, some crucial reproductive processes fall beyond the routine analysis performed in the porcine model, such as sperm capacitation, which is a necessary event for fertilization. A synergistic action of bicarbonate (HCO₃⁻) with calcium (Ca²⁺) is needed to achieve capacitation. The transport of Ca²⁺ is mediated by CatSper channels and Canonical Transient Potential Channels (TRPC). We quantified mRNA transcripts of different subunits of CatSper (β, γ and δ) and TRPC (1, 3, 4, 6 and 7) before and after in vitro capacitation by HCO₃⁻ ions. Our results showed that in vitro capacitation using HCO₃⁻ increases the relative abundance of mRNA transcripts of almost all subunits of Ca²⁺ channels, except CatSper-δ and TRPC1, which were significantly reduced. More studies are needed to elucidate the specific roles of the TRPC channels at a physiological and functional level.

Abstract

Sperm capacitation is a stepwise complex biochemical process towards fertilization. It includes a crucial early calcium (Ca²⁺) transport mediated by CatSper channels and Canonical Transient Potential Channels (TRPC). We studied the relative abundance of mRNA transcripts changes of the CatSper β, γ and δ subunits and TRPC-channels 1, 3, 4, 6 and 7 in pig spermatozoa, after triggering in vitro capacitation by bicarbonate ions at levels present in vivo at the fertilization site. For this purpose, we analyzedfive5 ejaculate pools (from three fertile adult boars) before (control-fresh samples) and after in vitro exposure to capacitation conditions (37 mM NaHCO₃, 2.25 mM CaCl₂, 2 mM caffeine, 0.5% bovine serum albumin and 310 mM lactose) at 38 °C, 5% CO₂ for 30 min. In vitro capacitation using bicarbonate elicits an increase in the relative abundance of mRNA transcripts of almost all studied Ca²⁺ channels, except CatSper-δ and TRPC1 (significantly reduced). These findings open new avenues of research to identify the specific role of each channel in boar sperm capacitation and elucidate the physiological meaning of the changes on sperm mRNA cargo.

Polyvinyl alcohol, but not bovine serum albumin, promotes the induction of full‐type hyperactivation in boar cyclic AMP analog‐treated spermatozoa

This study aimed to verify the effects of polyvinyl alcohol (PVA) and bovine serum albumin (BSA) on the induction of full-type hyperactivation in boar spermatozoa treated with a cyclic AMP analog (cBiMPS). Washed spermatozoa were treated with cBiMPS (100 μM) for 180 min. As shown in the assessment of sperm motility, PVA (0.05%-0.4%) significantly promoted the induction of full-type hyperactivation, whereas BSA (0.025%-0.4%) did not affect the induction. In comparative experiments, BSA (0.4%) effectively promoted the induction of full-type hyperactivation in bovine spermatozoa treated with cBiMPS, calyculin A (a protein phosphatase inhibitor), and digoxin (a Na⁺ /K⁺ -ATPase inhibitor), while PVA (0.1%) did not affect the induction. Western blotting showed that protein tyrosine phosphorylation states of >50 kDa sperm proteins were effectively enhanced by treatment with cBiMPS in the PVA/BSA-free medium and not affected by the addition of PVA (0.1%). The assessment of plasma membrane integrity indicated that BSA (0.4%) significantly decreased spermatozoa with intact plasma membranes. These results indicate that PVA (0.1%) promotes the induction of full-type hyperactivation and does not influence the protein tyrosine phosphorylation states in boar cBiMPS-treated spermatozoa. They also suggest that BSA should not be added to medium containing cBiMPS for boar spermatozoa.

Membrane Remodeling and Matrix Dispersal Intermediates During Mammalian Acrosomal Exocytosis

To become fertilization-competent, mammalian sperm must undergo a complex series of biochemical and morphological changes in the female reproductive tract. These changes, collectively called capacitation, culminate in the exocytosis of the acrosome, a large vesicle overlying the nucleus. Acrosomal exocytosis is not an all-or-nothing event but rather a regulated process in which vesicle cargo disperses gradually. However, the structural mechanisms underlying this controlled release remain undefined. In addition, unlike other exocytotic events, fusing membranes are shed as vesicles; the cell thus loses the entire anterior two-thirds of its plasma membrane and yet remains intact, while the remaining nonvesiculated plasma membrane becomes fusogenic. Precisely how cell integrity is maintained throughout this drastic vesiculation process is unclear, as is how it ultimately leads to the acquisition of fusion competence. Here, we use cryoelectron tomography to visualize these processes in unfixed, unstained, fully hydrated sperm. We show that paracrystalline structures within the acrosome disassemble during capacitation and acrosomal exocytosis, representing a plausible mechanism for gradual dispersal of the acrosomal matrix. We find that the architecture of the sperm head supports an atypical membrane fission-fusion pathway that maintains cell integrity. Finally, we detail how the acrosome reaction transforms both the micron-scale topography and the nanoscale protein landscape of the sperm surface, thus priming the sperm for fertilization.

Exogenous Albumin Is Crucial for Pig Sperm to Elicit In Vitro Capacitation Whereas Bicarbonate Only Modulates Its Efficiency

Simple Summary

In this work, we addressed if the presence of exogenous bicarbonate required for pig sperm capacitation, which is a necessary step to acquire fertilizing ability. While sperm incubated in media without BSA or BSA/bicarbonate did not achieve in vitro capacitation, those incubated with BSA reached that status under any bicarbonate concentration, even when bicarbonate was absent. Interestingly, there were differences related to the concentration of bicarbonate, since sperm incubated in media with BSA and with no bicarbonate or 5 mM bicarbonate showed lower overall efficiency in achieving in vitro capacitation than those incubated in the presence of BSA and higher concentration of bicarbonate. Additionally, at the end of the experiment, sperm incubated in the presence of BSA and 38 mM bicarbonate showed lower motility and plasma membrane integrity than those incubated in media with BSA and lower concentrations of bicarbonate. In conclusion, BSA is crucial in for pig sperm to elicit in vitro capacitation and trigger the subsequent progesterone-induced acrosome exocytosis. In contrast, although exogenous bicarbonate does not appear to be indispensable, it shortens the time needed to reach that capacitated status.

Abstract

This work sought to address whether the presence of exogenous bicarbonate is required for pig sperm to elicit in vitro capacitation and further progesterone-induced acrosome exocytosis. For this purpose, sperm were either incubated in a standard in vitro capacitation medium or a similar medium with different concentrations of bicarbonate (either 0 mM, 5 mM, 15 mM or 38 mM) and BSA (either 0 mg/mL or 5 mg/mL). The achievement of in vitro capacitation and progesterone-induced acrosomal exocytosis was tested through the analysis of sperm motility, plasma membrane integrity and lipid disorder, acrosome exocytosis, intracellular calcium levels, mitochondria membrane potential, O₂ consumption rate and the activities of both glycogen synthase kinase 3 alpha (GSK3α) and protein kinase A (PKA). While sperm incubated in media without BSA or BSA/bicarbonate, they did not achieve in vitro capacitation; those incubated in media with BSA achieved the capacitated status under any bicarbonate concentration, even when bicarbonate was absent. Moreover, there were differences related to the concentration of bicarbonate, since sperm incubated in media with BSA and with no bicarbonate or 5 mM bicarbonate showed lower overall efficiency in achieving in vitro capacitation than those incubated in the presence of BSA and 15 mM or 38 mM bicarbonate. Additionally, at the end of the experiment, sperm incubated in the presence of BSA and 38 mM bicarbonate showed significantly (p < 0.05) lower values of motility and plasma membrane integrity than those incubated in media with BSA and lower concentrations of bicarbonate. In conclusion, BSA is instrumental for pig sperm to elicit in vitro capacitation and trigger the subsequent progesterone-induced acrosome exocytosis. Furthermore, while exogenous bicarbonate does not seem to be essential to launch sperm capacitation, it does modulate its efficiency.

Sperm Lipid Markers of Male Fertility in Mammals

Sperm plasma membrane lipids are essential for the function and integrity of mammalian spermatozoa. Various lipid types are involved in each key step within the fertilization process in their own yet coordinated way. The balance between lipid metabolism is tightly regulated to ensure physiological cellular processes, especially referring to crucial steps such as sperm motility, capacitation, acrosome reaction or fusion. At the same time, it has been shown that male reproductive function depends on the homeostasis of sperm lipids. Here, we review the effects of phospholipid, neutral lipid and glycolipid homeostasis on sperm fertilization function and male fertility in mammals.

Paternal trans-fatty acid and vitamin E diet affects rat offspring's semen quality and PPARs expression

Trans-fatty acids (TFAs) consumption has created concerns regarding male/female reproductive system. However, the effects of TFA in paternal diet on offspring's reproduction have not been addressed. The purpose of this study is to investigate the effects of rat paternal TFAs and vitamin E consumption on offspring's sperm quality and expression pattern of peroxisome proliferator-activated receptors (PPARs) in testis tissues. Forty adult male rats were randomly divided into four groups: Control diet (C); Control diet plus TFA (CTH); diet supplemented with vitamin E (E) and a diet containing vitamin E and TFA (ETH). Mother rats had normal diet during gestation period. Three offspring from each group were chosen randomly and their testicular samples were collected, and sperm parameters were measured by CASA. Our results indicate that feeding fathers with TFA can negatively affect offspring's sperm concentration and motility, while consumption of vitamin E can improve these parameters (p < .05). The paternal diet containing TFA down-regulated the expression of PPARβ and PPARγ genes, whereas vitamin E-containing diet up-regulated the transcription of PPAR genes. In conclusion, TFA intake in paternal diet may have negative effects on reproductive system of the offspring while vitamin E may not diminish these effects.

Transcriptomic and metabolomic insights into the variety of sperm storage in oviduct of egg layers

In birds, the sperm storage tubules (SST) are dispersed in uterovaginal junction (UVJ) and highly correlated with differential capacity of sperm storage (SS) in and among species with unspecified mechanisms. Here, the SS duration of 252 egg layer breeders was evaluated in 5 rounds with 3 phenotypic traits to screen high- and low-SS individuals, respectively, followed with transcriptome of UVJ tissues and metabolome of serum (high-SS vs. low-SS) to decipher the candidate genes and biochemical markers correlated with differential SS capacity. Histological characterization suggested slightly higher density of SST in UVJ (high-SS vs. low-SS). Transcriptome analyses identified 596 differentially expressed genes (336 upregulated vs. 260 downregulated), which were mainly enriched in gene ontology terms of homeostasis, steroid and lipid metabolism and hormone activity, and 12 significant pathways (P < 0.05) represented by calcium, steroid, and lipid metabolism. Immunohistochemical staining of GNAQ, ST6GAL1, ADFP, and PCNA showed similar distribution in UVJ tissues between 2 groups. Several candidates (HSD11B2, DIO2, AQP3, GNAQ, NANS, ST6GAL1) combined with 4 (11β-prostaglandin F2α, prostaglandin B1, 7α-hydroxytestosterone, and N-acetylneuraminic acid) of 40 differential metabolites enriched in serum metabolome were considered as regulators and biomarkers of SS duration in egg layer breeders. The integrated transcriptome and metabolome analyses of chicken breeder hens will provide novel insights for exploration and improvement of differential SS capacity in birds.

Inhibition of Potassium Channels Affects the Ability of Pig Spermatozoa to Elicit Capacitation and Trigger the Acrosome Exocytosis Induced by Progesterone

During capacitation, sperm undergo a myriad of changes, including remodeling of plasma membrane, modification of sperm motility and kinematic parameters, membrane hyperpolarization, increase in intracellular calcium levels, and tyrosine phosphorylation of certain sperm proteins. While potassium channels have been reported to be crucial for capacitation of mouse and human sperm, their role in pigs has not been investigated. With this purpose, sperm samples from 15 boars were incubated in capacitation medium for 300 min with quinine, a general blocker of potassium channels (including voltage-gated potassium channels, calcium-activated potassium channels, and tandem pore domain potassium channels), and paxilline (PAX), a specific inhibitor of calcium-activated potassium channels. In all samples, acrosome exocytosis was induced after 240 min of incubation with progesterone. Plasma membrane and acrosome integrity, membrane lipid disorder, intracellular calcium levels, mitochondrial membrane potential, and total and progressive sperm motility were evaluated after 0, 120, and 240 min of incubation, and after 5, 30, and 60 min of progesterone addition. Although blocking potassium channels with quinine and PAX prevented sperm to elicit in vitro capacitation by impairing motility and mitochondrial function, as well as reducing intracellular calcium levels, the extent of that inhibition was larger with quinine than with PAX. Therefore, while our data support that calcium-activated potassium channels are essential for sperm capacitation in pigs, they also suggest that other potassium channels, such as the voltage-gated, tandem pore domain, and mitochondrial ATP-regulated ones, are involved in that process. Thus, further research is needed to elucidate the specific functions of these channels and the mechanisms underlying its regulation during sperm capacitation.

Adhesion to oviduct glycans regulates porcine sperm Ca2+ influx and viability

Before fertilization, sperm bind to epithelial cells of the oviduct isthmus to form a reservoir that regulates sperm viability and capacitation. The sperm reservoir maintains optimum fertility in species, like swine, in which semen deposition and ovulation may not be well synchronized. We demonstrated previously that porcine sperm bind to two oviductal glycan motifs, a biantennary 6-sialylated N-acetyllactosamine (bi-SiaLN) oligosaccharide and 3-O-sulfated Lewis X trisaccharide (suLe^X). Here, we assessed the ability of these glycans to regulate sperm Ca²⁺ influx, capacitation and affect sperm lifespan. After 24 h, the viability of sperm bound to immobilized bi-SiaLN and suLe^X was higher (46% and 41% respectively) compared to viability of free-swimming sperm (10–12%). Ca²⁺ is a central regulator of sperm function so we assessed whether oviduct glycans could affect the Ca²⁺ influx that occurs during capacitation. Using a fluorescent intracellular Ca²⁺ probe, we observed that both oviduct glycans suppressed the Ca²⁺ increase that occurs during capacitation. Thus, specific oviduct glycans can regulate intracellular Ca²⁺. Because the increase in intracellular Ca²⁺ was suppressed by oviduct glycans, we examined whether glycans affected capacitation, as determined by protein tyrosine phosphorylation and the ability to undergo a Ca²⁺ ionophore-induced acrosome reaction. We found no discernable suppression of capacitation in sperm bound to oviduct glycans. We also detected no effect of oviduct glycans on sperm motility during capacitation. In summary, Le^X and bi-SiaLN glycan motifs found on oviduct oligosaccharides suppress the Ca²⁺ influx that occurs during capacitation and extend sperm lifespan but do not affect sperm capacitation or motility.

Assessment of binder of sperm protein 1 (BSP1) and heparin effects on in vitro capacitation and fertilization of bovine ejaculated and epididymal sperm

The present study evaluated the effect of binder of sperm protein 1 (BSP1) and/or heparin on in vitro bovine capacitation and fertilization rates using epididymal and ejaculated bovine sperm. Frozen-thawed sperm were selected and used in the following treatments. Control group: Fert-TALP medium without heparin; heparin (HEP) group: Fert-TALP with heparin (10 UI/ml); BSP1 group: Fert-TALP medium with BSP1 (10 µg/ml for ejaculated sperm; 40 µg/ml for epididymal sperm); HEP + BSP1 group: Fert-TALP medium with heparin (5 UI/ml) and BSP1 (5 µg/ml for ejaculated sperm; 20 µg/ml for epididymal sperm) and determined in vitro capacitation rates in different interval times (0, 15, 30 and 60 min) using the chlortetracycline fluorescence (CTC) method. Also, we evaluated the development rates of oocytes fertilized with ejaculated or epididymal sperm into the same treatments. Capacitation was greater and faster when ejaculated sperm were treated for 60 min with heparin compared with other treatments. However, developmental rates were similar in all treatments. For epididymal sperm, the treatments with BSP1 presented higher capacitation and fertilization rates compared with heparin (P < 0.05). The effects of heparin + BSP1 on capacitation and developmental rates did not cause any increase in capacitation or blastocyst rates compared with other groups for ejaculated or epididymal sperm. In conclusion, this study confirmed that either BSP1 and heparin can be used as capacitator agents for bovine ejaculated sperm during IVF. However, BSP1 seems to be more efficient compared with heparin for epididymal sperm. Furthermore, BSP1 and heparin have no synergic effects on sperm capacitation.

Post-ejaculatory modifications to sperm (PEMS)

Mammalian sperm must spend a minimum period of time within a female reproductive tract to achieve the capacity to fertilize oocytes. This phenomenon, termed sperm 'capacitation', was discovered nearly seven decades ago and opened a window into the complexities of sperm-female interaction. Capacitation is most commonly used to refer to a specific combination of processes that are believed to be widespread in mammals and includes modifications to the sperm plasma membrane, elevation of intracellular cyclic AMP levels, induction of protein tyrosine phosphorylation, increased intracellular Ca2+ levels, hyperactivation of motility, and, eventually, the acrosome reaction. Capacitation is only one example of post-ejaculatory modifications to sperm (PEMS) that are widespread throughout the animal kingdom. Although PEMS are less well studied in non-mammalian taxa, they likely represent the rule rather than the exception in species with internal fertilization. These PEMS are diverse in form and collectively represent the outcome of selection fashioning complex maturational trajectories of sperm that include multiple, sequential phenotypes that are specialized for stage-specific functionality within the female. In many cases, PEMS are critical for sperm to migrate successfully through the female reproductive tract, survive a protracted period of storage, reach the site of fertilization and/or achieve the capacity to fertilize eggs. We predict that PEMS will exhibit widespread phenotypic plasticity mediated by sperm-female interactions. The successful execution of PEMS thus has important implications for variation in fitness and the operation of post-copulatory sexual selection. Furthermore, it may provide a widespread mechanism of reproductive isolation and the maintenance of species boundaries. Despite their possible ubiquity and importance, the investigation of PEMS has been largely descriptive, lacking any phylogenetic consideration with regard to divergence, and there have been no theoretical or empirical investigations of their evolutionary significance. Here, we (i) clarify PEMS-related nomenclature; (ii) address the evolutionary origin, maintenance and divergence in PEMS in the context of the protracted life history of sperm and the complex, selective environment of the female reproductive tract; (iii) describe taxonomically widespread types of PEMS: sperm activation, chemotaxis and the dissociation of sperm conjugates; (iv) review the occurence of PEMS throughout the animal kingdom; (v) consider alternative hypotheses for the adaptive value of PEMS; (vi) speculate on the evolutionary implications of PEMS for genomic architecture, sexual selection, and reproductive isolation; and (vii) suggest fruitful directions for future functional and evolutionary analyses of PEMS.

Evaluation of Enkephalin-Degrading Enzymes in Sperm from Heroin-Addicted Men

Background

The aim of this study was to investigate two enkephalin-degrading enzymes, aminopeptidase N (APN/ CD13) and endopeptidase (NEP/CD10), gene and protein expression levels in sperm samples of fertile and heroin- addicted men, and the correlation between their expressions and semen quality.

Materials and Methods

In this case-controlled study, semen was collected from 24 normozoospermic healthy (as a control group) and 24 heroin-addicted men donors (as case or addiction group). Sperm cells isolated by Cook Medical gradient (40-80%) and followed up by swim-up techniques were used for real-time quantitative polymer- ase chain reaction (qPCR) and flow cytometry techniques to assess APN/CD13 and NEP/CD10 genes and proteins subsequently. Semen parameters were analyzed by computer-assisted sperm analysis.

Results

The findings revealed that there were significant differences in sperm total motility (41.07 ± 3.63 vs. 63.03 ± 3.31 %, P=0.0001), progressive motility (35.21 ± 2.64 vs. 20.93 ± 3.22%, P=0.001) and viability (69.9 ± 4.69 vs. 86.81 ± 1.26 %, P=0.002) in the addicted group vs. control ones. APN and NEP gene expression levels in the addicted group decreased compared with the control ones (1.00 ± 0.67 vs. 0.36 ± 0.13, P= 0.008 and 1.07 ± 0.11 vs. 0.52 ± 0.12 0.002, respectively). Flow cytometry analysis showed that the average percent of APN/CD13 in heroin consumers significantly decreased compared with the healthy ones, while NEP/CD10 rate between two groups was similar. We also observed that duration of drug dependence is correlated with sperm viability (r=-0.627, P=0.016) and motility (r=-0.410, P=0.05), NEP (r=-0.434, P= 0.049), and APN (r=-0.641, P=0.002) gene expression levels.

Conclusion

We conclude that semen quality and enkephalin-degrading enzymes were altered in heroin-addicted men. other confirming the internal validity of our estimates.

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.

Flagellar hyperactivation of bull and boar spermatozoa

BACKGROUND

In mammals, flagellar hyperactivation is indispensable to sperm fertilization with oocytes in vivo, although there are species differences in regulatory mechanisms for this event. In this study, I reviewed researches regarding hyperactivation of bull and boar spermatozoa, in comparison with those of spermatozoa from other species.

METHODS

Recent publications regarding sperm hyperactivation were collected and summarized.

RESULTS MAIN FINDINGS

In bull and boar spermatozoa, there are two types of hyperactivation "full-type hyperactivation and nonfull-type hyperactivation" which are equivalent to anti-hock hyperactivation and pro-hock hyperactivation of mouse spermatozoa, respectively, on the basis of the flagellar parts exhibiting asymmetrical beating. Full-type hyperactivation is initiated in response to a rapid increase of cytoplasmic Ca2+ in the connecting/middle and principal pieces by the mobilization of this divalent ion from extracellular space and internal store through cation channels. Regulatory molecules for the increase of cytoplasmic Ca2+ in the connecting/middle pieces are probably different from those in the principal pieces.

CONCLUSION

I have proposed a hypothesis on the regulation of full-type hyperactivation by the distinct signaling cascades leading to the increase in cytoplasmic Ca2+ between the connecting/middle and principal pieces of bull and boar spermatozoa.

Cryopreservation and egg yolk medium alter the proteome of ram spermatozoa

Cryopreservation causes significant lethal and sub-lethal damage to spermatozoa. In order to improve freezing outcomes, a comprehensive understanding of sub-lethal damage is required. Cryopreservation induced changes to sperm proteins have been investigated in several species, but few have employed currently available state of the art, data independent acquisition mass spectrometry (MS) methods. We used the SWATH LC-MS method to quantitatively profile proteomic changes to ram spermatozoa following exposure to egg yolk and cryopreservation. Egg yolk contributed 15 proteins to spermatozoa, including vitellogenins, apolipoproteins and complement component C3. Cryopreservation significantly altered the abundance of 51 proteins. Overall, 27 proteins increased (e.g. SERPINB1, FER) and 24 proteins decreased (e.g. CCT subunits, CSNK1G2, TOM1L1) in frozen thawed ram spermatozoa, compared to fresh spermatozoa. Chaperones constituted 20% of the proteins lost from spermatozoa following cryopreservation. These alterations may interfere with both normal cellular functioning and the ability of frozen thawed spermatozoa to appropriately respond to stress. This is the first study to apply SWATH mass spectrometry techniques to characterise proteins contributed by egg yolk based freezing media and to profile cryopreservation induced proteomic changes to ram spermatozoa.

SIGNIFICANCE

This study profiles changes to the sperm proteome induced by exposure to egg yolk based media and the process of cryopreservation, and the biological consequences are discussed.

Neuronal signaling repertoire in the mammalian sperm functionality

The common embryonic origin has been a recurrent explanation to understand the presence of "neural receptors" in sperm. However, this designation has conditioned a bias marked by the classical neurotransmission model, dismissing the possibility that neurotransmitters can play specific roles in the sperm function by themselves. For instance, the launching of acrosome reaction, a fundamental sperm function, includes several steps that recall the process of presynaptic secretion. Unlike of postsynaptic neuron, whose activation is mediated by molecular interaction between neurotransmitter and postsynaptic receptors, the oocyte activation is not mediated by receptors, but by cytosolic translocation of sperm phospholipase (PLCζ). Thus, the sperm has a cellular design to access and activate the oocyte and restore the ploidy of the species by an "allogenic pronuclear fusion." At subcellular level, the events controlling sperm function, particularly the capacitation process, are activated by chemical signals that trigger ion fluxes, sterol oxidation, synthesis of cyclic adenosine monophosphate, protein kinase A activation, tyrosine phosphorylations and calcium signaling, which correspond to second messengers similar to those associated with exocytosis and growth cone guidance in neurons. Classically, the sperm function associated with neural signals has been analyzed as a unidimensional approach (single ligand-receptor effect). However, the in vivo sperm are exposed to multidimensional signaling context, for example, the GABAergic, monoaminergic, purinergic, cholinergic, and melatoninergic, to name a few. The aim of this review is to present an overview of sperm functionality associated with "neuronal signaling" and possible cellular and molecular mechanisms involved in their regulation.

Characterization of extracellular Ca2+ -dependent full-type hyperactivation in ejaculated boar spermatozoa preincubated with a cAMP analog

Ejaculated boar spermatozoa exhibit two types of hyperactivation: full and non-full. Full-type hyperactivation is characterized by the asymmetrical bending of the entire middle piece-principal piece and a twisting/figure-eight-like trajectory, and can be induced by simple incubation with CaCl₂ after preincubation with a cAMP analog (Sp-5,6-dichloro-1-β-D-ribofuranosyl-benzimidazole-3',5'-cyclic monophosphorothioate [cBiMPS]). Here, we compared the sperm flagellar motility after treatments with elevators of [Ca²⁺ ]_i (cBiMPS/CaCl₂ , thimerosal, procaine, and 4-aminopyridine) to characterize the regulatory mechanism of extracellular Ca²⁺ -dependent, full-type hyperactivation in ejaculated boar spermatozoa, and examined the possible involvement of Transient receptor potential cation channel subfamily C member 3 (TRPC3) in this event using the specific inhibitor Pyr3. Full-type hyperactivation was induced by a 60-min incubation with CaCl₂ following a 180-min preincubation with cBiMPS but without Ca²⁺ . Thimerosal-treated spermatozoa exhibited full-type hyperactivation in a manner independent of extracellular Ca²⁺ ; conversely, this was not observed in procaine- or 4-aminopyridine-treated spermatozoa. A 20-min treatment with Pyr3 between preincubation with cBiMPS and incubation with CaCl₂ , significantly suppressed the normal phenotype. These observations indicated that mechanisms underlying full-type hyperactivation in spermatozoa incubated with CaCl₂ after preincubation with cBiMPS are different from those in the thimerosal-treated spermatozoa. Furthermore, indirect immunofluorescence localized TRPC3 in the upper segment of the middle piece, which bends asymmetrically during full-type hyperactivation but not in non-full-type hyperactivation, suggesting that TRPC3 may be involved in the extracellular Ca²⁺ -dependent full-type hyperactivation in ejaculated boar spermatozoa.

Reproductive tract modifications of the boar sperm surface

The sperm cell has a unique, polarized, and segregated surface that is modified extensively by the changing environments in both the male and the female reproductive tracts. The sperm cannot refresh its surface, as protein translation and membrane recycling by intracellular vesicular transport have ceased upon its maturation. So, how is the sperm surface modified in the reproductive tracts and how do these processes affect fertilization? This review traces these modifications as boar sperm travels from their liberation from the Sertoli cell into the lumen of seminiferous tubules of the testis to the site of fertilization in the ampulla of the oviduct in the sow, via an artificial insemination route. The effect of sperm dilution for artificial insemination, as well as more extensive sperm processing for in vitro fertilization, cryopreservation, or sex sorting, are also discussed with respect to how these procedures affect sperm surface organization and fertilization capacity.

The CatSper channel modulates boar sperm motility during capacitation

The cation channel of sperm (CatSper) comprises four transmembrane subunits specifically expressed in human, equine, murine and ovine spermatozoa, apparently implicated in capacitation, hyperactivation and acrosome exocytosis. Western blotting and immunocytochemistry showed hereby that CatSper subunits are also present in boar spermatozoa, primarily over the sperm neck, tail and cytoplasmic droplets; albeit CatSper -1 presented in addition some distribution over the membrane of the acrosome and CatSper -2 and -4 over the membrane of the post-acrosome. The role of the Catsper channel in boar spermatozoa was investigated by extending the spermatozoa in media containing different calcium (Ca²⁺) availability and exposure to the capacitation-trigger bicarbonate, to progesterone or CatSper inhibitors (Mibefradil and NNC 55-0396), separately or sequentially, at physiological and toxicological doses. Extracellular Ca²⁺ availability, combined with bicarbonate exposure (capacitation-inducing conditions) decreased sperm motility, similarly to when spermatozoa incubated in capacitation-inducing conditions was exposed to Mibefradil and NNC 55-0396. Exposure of these spermatozoa to progesterone did not cause significant changes in sperm motility and nor did it revert its decrease induced by CatSper antagonists. In conclusion, the CatSper channel regulates sperm motility during porcine capacitation-related events in vitro.

Capacitation-Related Lipid Remodeling of Mammalian Spermatozoa Membrane Determines the Final Fate of Male Gametes: A Computational Biology Study

To become fully fertile, mammalian spermatozoa must undergo a complex process of biochemical maturation within the female genital tract, which determines a marked lipid remodeling (LR) of membranes. Here, we represent this process as a biological network, which is a graph constituted by nodes (the molecules involved in LR) and by edges (their interactions). As a result, we found that LR network has a scale-free and small world topology. This implies that it is robust against random damage and that it allows a fast and specific transmission of information. In addition, the hubs in the network allow identification of the control mechanisms involved in membrane-related signaling, which could concur in determining the fate of ejaculated spermatozoa. Interestingly, different pathways involved in LR (maintenance of functional incompetence, reaching of fertilizing ability, apoptosis) are overlapped and some molecules take part in different signalling cascades; thus their role in sperm biology needs to be interpreted in a more large context. In addition, it was possible to differentiate, either based on their topological and biological characteristics, the molecules acting as global or local controller in LR. These findings may contribute to the understanding of capacitation-related signaling and of sperm physiopathology.

The effects of diabetes on male fertility and epigenetic regulation during spermatogenesis

The effects of diabetes mellitus include long-term damages, dysfunctions, and failures of various organs. An important complication of diabetes is the disturbance in the male reproductive system. Glucose metabolism is an important event in spermatogenesis. Moreover, glucose metabolism is also important for maintaining basic cell activity, as well as specific functions, such as motility and fertilization ability in mature sperm. Diabetic disease and experimentally induced diabetes both demonstrated that either type 1 diabetes or type 2 diabetes could have detrimental effects on male fertility, especially on sperm quality, such as sperm motility, sperm DNA integrity, and ingredients of seminal plasma. Epigenetic modifications are essential during spermatogenesis. The epigenetic regulation represents chromatin modifications including DNA methylation, histone modifications, remodeling of nucleosomes and the higher-order chromatin reorganization and noncoding RNAs. If spermatogenesis is affected during the critical developmental window, embryonic gonadal development, and germline differentiation, environmentally-induced epigenetic modifications may become permanent in the germ line epigenome and have a potential impact on subsequent generations through epigenetic transgenerational inheritance. Diabetes may influence the epigenetic modification during sperm spermatogenesis and that these epigenetic dysregulation may be inherited through the male germ line and passed onto more than one generation, which in turn may increase the risk of diabetes in offspring.

Methods for Improving In Vitro and In Vivo Boar Sperm Fertility

Fertility of boar spermatozoa is changed after ejaculation in vivo and in vitro. During processing for in vitro fertilization (IVF), although spermatozoa are induced capacitation, resulting in a high penetration rate, persistent obstacle of polyspermic penetration is still observed with a high incidence. For artificial insemination (AI), we still need a large number of spermatozoa and lose a majority of those in the female reproductive tract. Fertility of cryopreserved boar spermatozoa is still injured through freezing and thawing process. In the present brief review, factors affecting fertility of boar sperm during IVF, AI and cryopreservation are discussed in the context of discovering methodologies to improve it.

Remodeling of the plasma membrane in preparation for sperm-egg recognition: roles of acrosomal proteins

The interaction of sperm with the egg's extracellular matrix, the zona pellucida (ZP) is the first step of the union between male and female gametes. The molecular mechanisms of this process have been studied for the past six decades with the results obtained being both interesting and confusing. In this article, we describe our recent work, which attempts to address two lines of questions from previous studies. First, because there are numerous ZP binding proteins reported by various researchers, how do these proteins act together in sperm–ZP interaction? Second, why do a number of acrosomal proteins have ZP affinity? Are they involved mainly in the initial sperm–ZP binding or rather in anchoring acrosome reacting/reacted spermatozoa to the ZP? Our studies reveal that a number of ZP binding proteins and chaperones, extracted from the anterior sperm head plasma membrane, coexist as high molecular weight (HMW) complexes, and that these complexes in capacitated spermatozoa have preferential ability to bind to the ZP. Zonadhesin (ZAN), known as an acrosomal protein with ZP affinity, is one of these proteins in the HMW complexes. Immunoprecipitation indicates that ZAN interacts with other acrosomal proteins, proacrosin/acrosin and sp32 (ACRBP), also present in the HMW complexes. Immunodetection of ZAN and proacrosin/acrosin on spermatozoa further indicates that both proteins traffic to the sperm head surface during capacitation where the sperm acrosomal matrix is still intact, and therefore they are likely involved in the initial sperm–ZP binding step.

New insights into the regulation of cholesterol efflux from the sperm membrane

Cholesterol is an essential component of the mammalian plasma membrane because it promotes membrane stability without comprising membrane fluidity. Given this important cellular role, cholesterol levels are tightly controlled at multiple levels. It has been clearly shown that cholesterol redistribution and depletion from the sperm membrane is a key part of the spermatozoon's preparation for fertilization. Some factors that regulate these events are described (e.g., bicarbonate, calcium) but the mechanisms underlying cholesterol export are poorly understood. How does a hydrophobic cholesterol molecule inserted in the sperm plasma membrane enter the energetically unfavorable aqueous surroundings? This review will provide an overview of knowledge in this area and highlight our gaps in understanding. The overall aim is to better understand cholesterol redistribution in the sperm plasma membrane, its relation to the possible activation of a cholesterol transporter and the role of cholesterol acceptors. Armed with such knowledge, sperm handling techniques can be adapted to better prepare spermatozoa for in vitro and in vivo fertilization.

Penicillamine prevents ram sperm agglutination in media that support capacitation

Ram spermatozoa are difficult to capacitate in vitro. Here we describe a further complication, the unreported phenomenon of head-to-head agglutination of ram spermatozoa following dilution in the capacitation medium Tyrodes plus albumin, lactate and pyruvate (TALP). Sperm agglutination is immediate, specific and persistent and is not associated with a loss of motility. Agglutination impedes in vitro sperm handling and analysis. So the objectives of this study were to investigate the cause of sperm agglutination and potential agents which may reduce agglutination. The percentage of non-agglutinated, motile spermatozoa increased when bicarbonate was omitted from complete TALP suggesting that bicarbonate ions stimulate the agglutination process. d-penicillamine (PEN), a nucleophilic thiol, was highly effective at reducing agglutination. The inclusion of 250 μM PEN in TALP reduced the incidence of motile, agglutinated spermatozoa from 76.7±2.7% to 2.8±1.4%. It was then assessed if PEN (1 mM) could be included in existing ram sperm capacitation protocols (TALP +1 mM dibutyryl cAMP, caffeine and theophylline) to produce spermatozoa that were simultaneously capacitated and non-agglutinated. This protocol resulted in a sperm population which displayed high levels of tyrosine phosphorylated proteins and lipid disordered membranes (merocyanine-540) while remaining motile, viable, acrosome-intact and non-agglutinated. In summary, PEN (1 mM) can be included in ram sperm capacitation protocols to reduce sperm agglutination and allow for the in vitro assessment of ram sperm capacitation.

Purification of binder of sperm protein 1 (BSP1) and its effects on bovine in vitro embryo development after fertilization with ejaculated and epididymal sperm

The present study evaluated functional aspects of binder of sperm 1 (BSP1) in the bovine species. In a first experiment, cumulus-oocyte complexes (n = 1274) were incubated with frozen-thawed ejaculated sperm (18 hours) in Fert-TALP medium containing: heparin, 10, 20, or 40 μg/mL BSP1. Heparin followed by gelatin affinity chromatography was used for purification of BSP1 from bovine seminal vesicle fluid. With ejaculated sperm, cleavage rates were similar when Fert-TALP medium was incubated with heparin (74.1 ± 2.7%), 10 μg/mL BSP1 (77.8 ± 3.1%), or 20 μg/mL BSP1 (74 ± 2.0%). Day-7 blastocyst rates were equivalent after incubations with heparin (40.8 ± 5.0%) and 10 μg/mL BSP1 (34.1 ± 4.4%), but reduced after 20 μg/mL BSP1 (22.4 ± 2.9%) and 40 μg/mL BSP1 (19.3 ± 4.1%; P < 0.05). In the second experiment, cumulus-oocyte complexes (n = 1213) were incubated with frozen-thawed cauda epididymal sperm (18 hours) in Fert-TALP medium containing: no heparin, heparin, 10, 20, or 40 μg/mL. Cleavage and blastocyst rates were similar after treatments with heparin (68.5 ± 1.3% and 24.7 ± 3.2%, respectively) or without heparin (65.5 ± 1.8% and 27.3 ± 1.6%, respectively). Cleavage was higher after treatment with any BSP1 concentrations (74.2 ± 2.7%-79.0 ± 1.1%) than without heparin (P < 0.05). Also, cleavage was better after Fert-TALP medium incubation with 40 μg/mL BSP1 (79.0 ± 1.1%) than with heparin (68.5 ± 1.3%; P < 0.05). Embryo development was higher (P < 0.05) after treatment with 20 μg/mL BSP1 (35.6 ± 2.5%) and 40 μg/mL (41.1 ± 2%) than after incubations with heparin (24.7 ± 3.2%) or without heparin (27.3 ± 1.6%). Interestingly, BSP1 did not cause reductions in blastocyst rates after fertilization with epididymal sperm, as observed with ejaculated sperm. On the basis of immunocytochemistry, there was BSP1 binding to frozen-thawed ejaculated but not to epididymal sperm. Also, anti-BSP1 reaction remained on ejaculated sperm (as expected) and appeared on epididymal sperm after incubation with purified BSP1. Acrosome reaction of ejaculated and epididymal sperm was induced after incubation with purified BSP1 as well, indicating an effect of BSP1 on capacitation. In conclusion, purified BSP1 from bull seminal vesicles was able to bind to and induce capacitation of ejaculated and epididymal sperm. Also, BSP1 added to fertilization media and allowed proper cleavage and embryo development, with the effects being modulated by previous exposure or not of spermatozoa to seminal plasma.

Artificial insemination in pigs today

Use of artificial insemination (AI) for breeding pigs has been instrumental for facilitating global improvements in fertility, genetics, labor, and herd health. The establishment of AI centers for management of boars and production of semen has allowed for selection of boars for fertility and sperm production using in vitro and in vivo measures. Today, boars can be managed for production of 20 to 40 traditional AI doses containing 2.5 to 3.0 billion motile sperm in 75 to 100 mL of extender or 40 to 60 doses with 1.5 to 2.0 billion sperm in similar or reduced volumes for use in cervical or intrauterine AI. Regardless of the sperm dose, in liquid form, extenders are designed to sustain sperm fertility for 3 to 7 days. On farm, AI is the predominant form for commercial sow breeding and relies on manual detection of estrus with sows receiving two cervical or two intrauterine inseminations of the traditional or low sperm doses on each day detected in standing estrus. New approaches for increasing rates of genetic improvement through use of AI are aimed at methods to continue to lower the number of sperm in an AI dose and reducing the number of inseminations through use of a single, fixed-time AI after ovulation induction. Both approaches allow greater selection pressure for economically important swine traits in the sires and help extend the genetic advantages through AI on to more production farms.

Comparison of the effect of different media on the clinical outcomes of the density-gradient centrifugation/swim-up and swim-up methods

Objective

Sperm must be properly prepared in in vitro fertilization (IVF)-embryo transfer (ET) programs in order to control the fertilization rate and ensure that embryos are of high quality and have appropriate developmental abilities. The objective of this study was to determine the most optimal sperm preparation method for IVF.

Methods

Patients less than 40 years of age who participated in a fresh IVF-ET cycle from November 2012 to March 2013 were included in this study. Poor responders with less than three mature oocytes were excluded. Ham's F-10 medium or sperm-washing medium (SWM) was used in combination with the density-gradient centrifugation/swim-up (DGC-SUP) or SUP methods for sperm preparation. A total of 429 fresh IVF-ET cycles were grouped according to the media and methods used for sperm preparation and retrospectively analyzed (DGC-SUP/Ham's F-10, n=82; DGC-SUP/SWM, n=43; SUP/Ham's F-10, n=181; SUP/SWM, n=123).

Results

There were no significant differences among these four groups with respect to the mean age of the female partners, duration of infertility, number of previous IVF cycles, and retrieved oocytes. We determined that both the DGC-SUP and SUP methods for sperm preparation from whole semen, using either Ham's F-10 or SWM media, result in comparable clinical outcomes, including fertilization and pregnancy rates.

Conclusion

We suggest that both media and both methods for sperm preparation can be used for selecting high-quality sperm for assistive reproductive technology programs.

Sperm glucose transport and metabolism in diabetic individuals

Individuals with diabetes mellitus (DM) present marked reduction in sperm quality and higher DNA damage in spermatozoa, evidencing that this metabolic disorder impairs male fertility. These effects are related to defective testicular metabolic pathways and signaling, resulting in altered sperm metabolism. Spermatozoa metabolize several substrates to ensure energy supplies and any alteration in this feature compromise sperm quality. For ATP production, spermatozoa require substrate availability and the involvement of specific hexose membrane carriers. DM is known to modulate the spermatozoa substrate consumption and/or production due to altered glycolytic behavior. In fact, glucose uptake and metabolism is highly deregulated in diabetic individuals. Herein, we present an overview of the implications of DM in sperm glucose uptake and metabolism. The understanding of these processes is essential to identify key mechanisms associated with DM-related male (in)fertility. Moreover, it may contribute to the development of therapeutics to counteract the dysfunction induced by DM in sperm metabolism.

Porcine sperm capacitation involves tyrosine phosphorylation and activation of aldose reductase

Mammalian sperm must be activated in the tubal isthmus through capacitation to induce the acrosome reaction and subsequent fertilization. Although the molecular mechanisms involved in capacitation have yet to be fully elucidated, increased concentrations of reactive oxygen species (ROS) and the extent of tyrosine phosphorylation of proteins have been suggested to play central roles in the completion of capacitation. In this study, aldose reductase was for the first time identified as one of the tyrosine-phosphorylated proteins involved in the capacitation of porcine cauda epididymal sperm. Both tyrosine phosphorylation and activity of aldose reductase associated with the particulate fraction of sperm cells were significantly enhanced during capacitation. Alrestatin, a membrane-permeable and specific inhibitor of aldose reductase, plays a role in the inhibition of aldose reductase activity, elevation of intracellular levels of ROS, and induction of hyperactivated motility, all at similar dose dependencies. Alrestatin canceled both the increase in the tyrosine phosphorylation of aldose reductase and the decrease in the glutathione levels in sperm-induced during capacitation. The hyperactivated motility was induced to a higher extent in the presence of glucose than in the presence of fructose. These results indicate that aldose reductase plays an important role in induction of hyperactivation and capacitation of sperm through the elevation of ROS in sperm cells. Furthermore, aldose reductase was shown to be added to sperm during transit through the epididymis, suggesting that aldose reductase is one of the key proteins that support the functional maturation of sperm.