Biological basis for human capacitation

How sperm protects itself: A journey in the female reproductive system

Sperm must pass a complex route in the female reproductive tract (FRT) to reach the fertilization site and join the oocyte. Thus, it should employ several mechanisms to survive against the female immune system, fertilize the oocyte, and successfully transmit paternal genes to the next generation. In addition to self-protection, sperm may be involved in the immune tolerance to the developing embryo and regulating the FRT for embryo implantation and subsequent pregnancy. Hence, this review intends to summarize the mechanisms that protect sperm in the FRT: including immunomodulatory factors that are carried by seminal plasma, cell-to-cell and molecular interaction of sperm with epithelial and immune cells of the FRT, high regulated secretions of inflammatory factors such as cytokines, chemokines, and growth factors, inducing immune tolerance to paternal antigens, and specialized expression of cell receptors and binding proteins. In most of these events sperm induces the FRT to protect itself by modulating immune responses for its own benefit. However, not all sperm in the semen are able to trigger the survival mechanisms and only high-quality sperm will overcome this challenge. A clear understanding of the molecular mechanisms that maintain sperm viability and function in the FRT can lead to new knowledge about infertility etiology and a new approach in assisted reproductive technologies for the preparation and selection of the best sperm based on the criteria that physiologically happen in-vivo.

Flagellar beating forces of human spermatozoa with different motility behaviors

BACKGROUND

One of the causes of male infertility is associated with altered spermatozoa motility. These sperm features are frequently analyzed by image-based approaches, which, despite allowing the acquisition of crucial parameters to assess sperm motility, they are unable to provide details regarding the flagellar beating forces, which have been neglected until now.

RESULTS

In this work we exploit Fluidic Force Microscopy to investigate and quantify the forces associated with the flagellar beating frequencies of human spermatozoa. The analysis is performed on two groups divided according to the progressive motility of semen samples, as identified by standard clinical protocols. In the first group, 100% of the spermatozoa swim linearly (100% progressive motility), while, in the other, spermatozoa show both linear and circular motility (identified as 80 - 20% progressive motility). Significant differences in flagellar beating forces between spermatozoa from semen sample with different progressive motility are observed. Particularly, linear motile spermatozoa exhibit forces higher than those with a circular movement.

CONCLUSIONS

This research can increase our understanding of sperm motility and the role of mechanics in fertilization, which could help us unveil some of the causes of idiopathic male infertility.

Three-dimensional correlative microscopy of the Drosophila female reproductive tract reveals modes of communication in seminal receptacle sperm storage

In many taxa, females store sperm in specialized storage organs. Most insect sperm storage organs have a tubular structure, typically consisting of a central lumen surrounded by epithelial cells. These specialized tubules perform the essential tasks of transporting sperm through the female reproductive tract and supporting long-term sperm survival and function. Little is known about the way in which female sperm storage organs provide an environment conducive to sperm survival. We address this using a combined light microscopy, micro computed tomography (microCT), and Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) approach for high-resolution correlative three-dimensional imaging to advance our understanding of sperm-female interactions in Drosophila melanogaster. Using this multimodal approach, we were able to scan the lower female reproductive tract and distal portion of the seminal receptacle at low magnification, and to subsequently zoom in for further analysis on an ultrastructural level. Our findings highlight aspects of the way in which the seminal receptacle keeps sperm viable in the lumen, and set the stage for further studies. The methods developed are suitable not only for Drosophila but also for other organisms with soft, delicate tissues.

Deletion of the Sodium Glucose Cotransporter 1 (Sglt-1) impairs mouse sperm movement

The Sodium Glucose Cotransporter Isoform 1 (Sglt-1) is a symporter that moves Na+ and glucose into the cell. While most studies have focused on the role of Sglt-1 in the small intestine and kidney, little is known about this transporter's expression and function in other tissues. We have previously shown that Sglt-1 is expressed in the mouse sperm flagellum and that its inhibition interferes with sperm metabolism and function. Here, we further investigated the importance of Sglt-1 in sperm, using a Sglt-1 knockout mouse (Sglt-1 KO). RNA, immunocytochemistry, and glucose uptake analysis confirmed the ablation of Sglt-1 in sperm. Sglt-1 KO male mice are fertile and exhibit normal sperm counts and morphology. However, Sglt-1 null sperm displayed a significant reduction in total, progressive and other parameters of sperm motility compared to wild type (WT) sperm. The reduction in motility was exacerbated when sperm were challenged to swim in media with higher viscosity. Parameters of capacitation, namely protein tyrosine phosphorylation and acrosomal reaction, were similar in Sglt-1 KO and WT sperm. However, Sglt-1 KO sperm displayed a significant decrease in hyperactivation. The impaired motility of Sglt-1 null sperm was observed in media containing glucose as the only energy substrate. Interestingly, the addition of pyruvate and lactate to the media partially recovered sperm motility of Sglt-1 KO sperm, both in the low and high viscosity media. Altogether, these results support an important role for Sglt-1 in sperm energetics and function, providing sperm with a higher capacity for glucose uptake.

Sperm Mitochondria, the Driving Force Behind Human Spermatozoa Activities: Its Functions and Dysfunctions - A Narrative Review

Male infertility is a major issue, and numerous factors contribute to it. One of the important organelles involved in the functioning of human spermatozoa is mitochondria. There are 50-75 mitochondria helically arranged in mid-piece bearing one mitochondrial DNA each. Sperm mitochondria play a crucial role in sperm functions, including the energy production required for sperm motility and the production of reactive oxygen species, which in the physiological range helps in sperm maturation, capacitation, and acrosome reaction. It also plays a role in calcium signaling cascades, intrinsic apoptosis, and sperm hyperactivation. Any structural or functional dysfunction of sperm mitochondria results in increased production of reactive oxygen species and, a state of oxidative stress, decreased energy production, all leading to sperm DNA damage, impaired sperm motility and semen parameters, and reduced male fertility. Furthermore, human sperm mitochondrial DNA mutations can result in impaired sperm motility and parameters leading to male infertility. Numerous types of point mutations, deletions, and missense mutations have been identified in mtDNA that are linked with male infertility. Methods: Recent literature was searched from English language peer-reviewed journals from databases including PubMed, Scopus, EMBASE, Scholar, and Web of Science till September 2021. Search terms used were "Sperm mitochondria and male fertility", "Bioenergetics of sperm", "Sperm mitochondria and reactive oxygen species", "Sperm mitochondrial mutations and infertility". Conclusion: Sperm mitochondria is an important organelle involved in various functions of human spermatozoa and sperm mitochondrial DNA has emerged as one of the potent biomarkers of sperm quality and male fertility.

Influence of Two Widely Used Solvents, Ethanol and Dimethyl Sulfoxide, on Human Sperm Parameters

To study mechanisms involved in fertility, many experimental assays are conducted by incubating spermatozoa in the presence of molecules dissolved in solvents such as ethanol (EtOH) or dimethyl sulfoxide (DMSO). Although a vehicle control group is usually included in such studies, it does not allow to evaluate the intrinsic effect of the solvent on sperm parameters and its potential influence on the outcome of the experiment. In the present study, we incubated human spermatozoa for 4 h in a capacitation medium in the absence or the presence of different concentrations of EtOH and DMSO (0.1, 0.5, 1.0, and 2.0%) to assess the impact of these solvents on sperm motility, vitality, capacitation, and acrosome integrity. The presence of statistically significant relationships between increasing solvent concentrations and the investigated parameters was assessed using linear mixed models. A significant effect was observed with both solvents for total and progressive sperm motilities. We also evaluated the effect of time for these parameters and showed that the influence of the solvents was stable between 0 and 4 h, indicating an almost direct impact of the solvents. While EtOH did not influence sperm vitality and acrosome integrity, a significant effect of increasing DMSO concentrations was observed for these parameters. Finally, regarding capacitation, measured via phosphotyrosine content, although a dose-dependent effect was observed with both solvents, the statistical analysis did not allow to precisely evaluate the intensity of the effect. Based on the results obtained in the present study, and the corresponding linear mixed models, we calculated the concentration of both solvents which would result in a 5% decline in sperm parameters. For EtOH, these concentrations are 0.9, 0.7, and 0.3% for total motility, progressive motility, and capacitation, respectively, while for DMSO they are 1.5, 1.1, >2, 0.3 and >2% for total motility, progressive motility, vitality, capacitation, and acrosome integrity, respectively. We recommend using solvent concentrations below these values to dissolve molecules used to study sperm function in vitro, to limit side effects.

Effect of High Viscosity on Energy Metabolism and Kinematics of Spermatozoa from Three Mouse Species Incubated under Capacitating Conditions

In order to sustain motility and prepare for fertilization, sperm require energy. The characterization of sperm ATP production and usage in mouse species revealed substantial differences in metabolic pathways that can be differentially affected by capacitation. Moreover, spermatozoa encounter different environments with varying viscoelastic properties in the female reproductive tract. Here, we examine whether viscosity affects sperm ATP levels and kinematics during capacitation in vitro. Sperm from three mouse species (Mus musculus, M. spretus, M. spicilegus) were incubated under capacitating conditions in a modified Tyrode's medium containing bicarbonate, glucose, pyruvate, lactate, and bovine serum albumin (mT-BH) or in a bicarbonate-free medium as a non-capacitating control. Viscosity was increased with the inclusion of polyvinylpyrrolidone. ATP was measured with a bioluminescence kit, and kinematics were examined with a computer-aided sperm analysis system. In M. musculus sperm, ATP declined during capacitation, but no differences were found between non-capacitating and capacitating sperm. In contrast, in M. spretus and M. spicilegus, ATP levels decreased in capacitating sperm. Increasing viscosity in the medium did not modify the timing or proportion of cells undergoing capacitation but did result in additional time- and concentration-dependent decreases in ATP in M. spretus and M. spicilegus under capacitating conditions. Additionally, increased viscosity altered both velocity and trajectory descriptors. The limited impact of capacitation and higher viscosity on M. musculus sperm ATP and kinematics could be related to the low intensity of postcopulatory sexual selection in this species. Responses seen in the other two species could be linked to the ability of their sperm to perform better under enhanced selective pressures.

Motility Assessment of Ram Spermatozoa

For successful fertilisation to occur, spermatozoa need to successfully migrate through the female reproductive tract and penetrate the oocyte. Predictably, poor sperm motility has been associated with low rates of fertilisation in many mammalian species, including the ram. As such, motility is one of the most important parameters used for in vitro evaluation of ram sperm quality and function. This review aims to outline the mechanical and energetic processes which underpin sperm motility, describe changes in motility which occur as a result of differences in sperm structure and the surrounding microenvironment, and assess the effectiveness of the various methods used to assess sperm motility in rams. Methods of subjective motility estimation are convenient, inexpensive methods widely used in the livestock industries, however, the subjective nature of these methods can make them unreliable. Computer-assisted sperm analysis (CASA) technology accurately and objectively measures sperm motility via two-dimensional tracing of sperm head motion, making it a popular method for sperm quality assurance in domesticated animal production laboratories. Newly developed methods of motility assessment including flagellar tracing, three-dimensional sperm tracing, in vivo motility assessment, and molecular assays which quantify motility-associated biomarkers, enable analysis of a new range of sperm motion parameters with the potential to reveal new mechanistic insights and improve ram semen assessment. Experimental application of these technologies is required to fully understand their potential to improve semen quality assessment and prediction of reproductive success in ovine artificial breeding programs.

The link between intrauterine adhesions and impaired reproductive performance: a systematic review of the literature

Background

Intrauterine adhesions (IUAs) are one of the main reproductive system diseases in women worldwide. Fusion between the injured opposing walls leads to partial-to-complete obliteration of the cavity and/or cervical canal. The main clinical manifestations in case of IUAs are menstrual disturbances, cyclic pain and reproductive disorders. The reproductive outcomes of women with IUAs remain limited and inefficient compared to women without IUAs, even after adhesiolysis. An exact understanding of the underlying mechanisms and processes to explain the compromised reproductive performance and outcomes in case of IUAs are lacking.

Methods

A systematic literature review of MEDLINE-PubMed (1966 to January 2022) and EMBASE (1974 to January 2022) was performed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies were included if they reported underlying causes, related mechanisms and processes to explain the association between IUAs and impaired reproductive performance, pregnancy and obstetric complications.

Results

After an extensive review of the literature, 58 articles were identified reporting underlying mechanisms to explain the association between IUAs and impaired fertility. Intrauterine scarring influences the process of fertilization, reproductive performance and ultimately reproductive outcome. IUAs can disturb the cervico-utero-tubal sperm transport and result in an avascular and unresponsive endometrium with decreased receptivity and thickness. Abnormal decidualization and abnormal trophoblastic infiltration leads to placental attachment disorders. Moreover, the risk for premature delivery, intrauterine fetal growth restriction and fetal anomalies is increased in case of IUAs.

Conclusion

The impact of IUAs on reproductive performance, even after adhesiolysis, is becoming more apparent. The postulated mechanisms to explain the association are related to sperm transport, embryo implantation and placentation. Prevention, by preserving the basal layer of the endometrium is essential. Effective and evidence-based strategies for the prevention of endometrial injury and formation of IUAs, are urgently needed.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-05164-2.

Sperm Ion Transporters and Channels in Human Asthenozoospermia: Genetic Etiology, Lessons from Animal Models, and Clinical Perspectives

In mammals, sperm fertilization potential relies on efficient progression within the female genital tract to reach and fertilize the oocyte. This fundamental property is supported by the flagellum, an evolutionarily conserved organelle that provides the mechanical force for sperm propulsion and motility. Importantly several functional maturation events that occur during the journey of the sperm cells through the genital tracts are necessary for the activation of flagellar beating and the acquisition of fertilization potential. Ion transporters and channels located at the surface of the sperm cells have been demonstrated to be involved in these processes, in particular, through the activation of downstream signaling pathways and the promotion of novel biochemical and electrophysiological properties in the sperm cells. We performed a systematic literature review to describe the currently known genetic alterations in humans that affect sperm ion transporters and channels and result in asthenozoospermia, a pathophysiological condition defined by reduced or absent sperm motility and observed in nearly 80% of infertile men. We also present the physiological relevance and functional mechanisms of additional ion channels identified in the mouse. Finally, considering the state-of-the art, we discuss future perspectives in terms of therapeutics of asthenozoospermia and male contraception.

Effect of Synthetic Cholesterol (Synthechol®) Supplementation in an Egg Yolk-free Extender on Dog Sperm Cryopreservation

BACKGROUND: SyntheChol® is a new synthetic, non-animal-derived cholesterol that is easily dissolved in ethanol, ready to use, and behaves in a similar way as natural cholesterol. Therefore, it could be used as a substitute of natural cholesterol in dog sperm freezing extender. OBJECTIVE: To evaluate the effect of supplementing an egg yolk-free (EY-free) extender with synthetic cholesterol (SyntheChol®) on cryopreserved dog sperm. MATERIALS AND METHODS: Spermatozoa (1 × 108 sperm/mL) were suspended in EY-free extender supplemented with 0% (control), 0.25, 0.5, 1, 2, 4, or 6% SyntheChol® (Extender 1), cooled at 4 °C for 1 h, and diluted (1:1, v/v) with Extender 1 containing 1 M glycerol. The spermatozoa were then cooled to 4 °C for 30 min. Sperm-containing straws were frozen using LN2 vapor. Sperm motility (computer-assisted sperm analysis, CASA), sperm membrane integrity (SYBR-14 and PI staining), and acrosome integrity (FITC-PSA) were evaluated after thawing. Thereafter, optimal concentrations were determined (0.25, 0.5, 1, or 2%) and used to evaluate reactive oxygen species (ROS) generation, apoptosis, and the gene expression of motility-related sperm mitochondria-associated cysteine-rich protein, apoptosis-related B-cell lymphoma 2 (BCL2), and BCL2-associated X protein ( BAX) in cryopreserved sperm. RESULTS: Sperm progressive motility, membrane integrity, and acrosome integrity were markedly greater in the SyntheChol®-supplemented groups (0.25, 0.5, 1, or 2%) than in the control group. Only BAX expression was significantly reduced in the SyntheChol® groups (0.25, 1, or 2%) compared with the control group. However, there were no significant effects on the ROS generation or apoptosis index. CONCLUSION: SyntheChol® (0.25, 1, or 2%) proved to be effective in reducing the BAX gene expression level and improving sperm progressive motility, and membrane and acrosome integrity.

Influence of in vitro capacitation time on structural and functional human sperm parameters

A cascade of dramatic physiological events is linked to the sperm acrosome reaction and binding to the oocyte's zona pellucida during human sperm capacitation. However, structural and functional sperm changes during capacitation currently remain poorly defined. Here, we performed a multibiomarker approach based on the utilization of sperm concentration, motility, viability, morphology, acrosome reaction, tyrosine phosphorylation, DNA fragmentation, and lectin-binding sites to analyze the impact caused by swim-up selection times (uncapacitated, 1 h capacitated, and 4 h capacitated) on sperm function and structure in normozoospermic samples. We found that a 4 h swim-up capacitation increased sperm quality, because a large number of cells with normal morphology and lower DNA fragmentation rates were recovered. Furthermore, the long-term capacitation induced a higher percentage of cells with tyrosine phosphorylation of the principal piece as well as a redistribution of lectin-binding sites. Overall, the multivariate biomarkers analyzed showed a less variable distribution on spermatozoa recovered after 4 h capacitation than that with the shorter capacitation time. These findings stress the importance of capacitation time as a relevant factor in sperm quality with potential biological reproductive implications both for basic research and in assisted reproduction techniques.

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.

Ovarian odorant-like biomolecules in promoting chemotaxis behavior of spermatozoa olfactory receptors during migration, maturation, and fertilization

Background

Studies have shown that olfactory receptor genes are the largest in the human genome, which are significantly expressed in olfactory and non-olfactory tissues such as the reproductive systems where they perform many important biological functions.

Main body

There is growing evidence that bioactive metabolites from the ovary, follicular fluid, and other parts of the female reproductive tract signal the sperm through a series of signal transduction cascades that regulate sperm migration, maturation, and fertilization processes. Several studies have highlighted the role of G-protein-coupled receptors in these cellular processes. Thus, we aimed to summarize the existing evidence describing the physiological role of most prominent exogenous and endogenous biomolecules found in the female reproductive organ in enhancing the chemotaxis behavior of spermatozoa during migration, maturation, and fertilization and also to elucidate the pathological implications of its dysfunctions and the clinical significance in human fertility.

Short conclusion

In the future, drugs and molecules can be designed to activate these receptors on sperm to facilitate fertility among infertile couples and use as contraceptives.

CatSper: The complex main gate of calcium entry in mammalian spermatozoa

Calcium ions (Ca²⁺) are involved in nearly every aspect of cellular life. They are one of the most abundant elements in mammals and play a vital role in physiological and biochemical processes acting mainly as intracellular messengers. In spermatozoa, several key functions are regulated by cytoplasmic Ca²⁺ concentration such as sperm capacitation, chemotaxis, hyperactive motility, and acrosome reaction. The sperm-specific ion channel CatSper is the principal calcium channel in sperm mediating the calcium influx into the sperm flagellum and acting as an essential modulator of downstream mechanisms involved in fertilization. This review aims to provide insights into the structure, localization, and function of the mammalian CatSper channel, primarily human and mice. The activation of CatSper by progesterone and prostaglandins, as well as the ligand-independent regulation of the channel by a change in the membrane voltage and intracellular pH are going to be addressed. Finally, major questions, challenges, and perspectives are discussed.

Vitamin C ameliorates tetrahydrocannabinol-induced spermatotoxicity in-vitro

BACKGROUND

We investigated the in-vitro effects of vitamin C on delta-9-tetrahydrocannabinol (THC) -induced reduction in spermatozoa motility and kinematics.

METHODS

Six rats were used for the study. Semen from each of the 6 rats was randomly divided into 6 groups such that each rat's semen was in all of the groups. Groups I-III received placebo, THC (1 mM), and vitamin C (5 mM) respectively. Group IV was pre-treated with cannabinoid receptors' blockers (CBs-) 1 and 2, followed by THC. Groups V and VI received THC and vitamin C, but group VI was additionally pre-treated with CBs-.

RESULTS

The spermatozoa progressive motility, average path velocity (VAP), curvilinear velocity (VCL), straight-line velocity (VSL), amplitude of lateral head (ALH) and beat cross frequency (BCF) were reduced by THC (6.08 ± 1.16%; 5.64 ± 0.82 μm/s; 6.96 ± 0.74 μm/s; 2.75 ± 0.23 μm/s; 0.31 ± 0.02 μm; and 0.78 ± 0.08 Hz respectively) but increased by vitamin C (51.20 ± 1.32%; 17.90 ± 0.21 μm/s; 25.11 ± 0.96 μm/s; 8.80 ± 0.27 μm/s; 0.75 ± 0.01 μm; and 3.15 ± 0.03 Hz respectively) when compared to control (39.72 ± 0.38%; 13.70 ± 0.29 μm/s; 18.04 ± 0.58 μm/s; 7.54 ± 0.34 μm/s; 0.65 ± 0.02 μm; and 2.79 ± 0.01 Hz respectively). Vitamin C inhibited the THC-induced reduction in these parameters (37.36 ± 0.73%; 10.98 ± 0.45 μm/s; 13.58 ± 0.30 μm/s; 7.11 ± 0.22 μm/s; 0.58 ± 0.01 μm; and 2.60 ± 0.01 Hz respectively) in the absence of CBs- 1 and 2, and even caused additional increases in progressive motility (49.54 ± 1.01%), VAP (15.70 ± 0.38 μm/s) and VCL (22.53 ± 0.29 μm/s) above the control levels with CBs-.

CONCLUSION

Vitamin C ameliorates the THC-induced reduction in spermatozoa motility in-vitro by modulation of their kinematics.

Metabonomic Insights into the Sperm Activation Mechanisms in Ricefield Eel (Monopterus albus)

In fish, sperm motility activation is one of the most essential procedures for fertilization. Previous studies have mainly focused on the external environmental effects and intracellular signals in sperm activation; however, little is known about the metabolic process of sperm motility activation in fish. In the present study, using ricefield eel (Monopterus albus) sperm as a model, metabonomics was used to analyze the metabolic mechanism of the sperm motility activation in fish. Firstly, 529 metabolites were identified in the sperm of ricefield eel, which were clustered into the organic acids, amino acids, nucleotides, benzene, and carbohydrates, respectively. Among them, the most abundant metabolites in sperm were L-phenylalanine, DL-leucine, L-leucine, lysolecithin choline 18:0, L-tryptophan, adenine, hypoxanthine, 7-Methylguanine, shikimic acid, and L-tyrosine. Secondly, compared to pre-activated sperm, the level of S-sulfo-L-cysteine and L-asparagine were both increased in the post-activated sperm. Ninety-two metabolites were decreased in the post-activated sperm, including quinic acid, acetylsalicylic acid, 7,8-dihydro L-biopterin, citric acid, glycylphenylalanine, and dihydrotachysterol (DHT). Finally, basing on the pathway analysis, we found that the changed metabolites in sperm motility activation were mainly clustered into energy metabolism and anti-oxidative stress. Fish sperm motility activation would be accompanied by the release of a large amount of energy, which might damage the genetic material of sperm. Thus, the anti-oxidative stress function is a critical process to maintain the normal physiological function of sperm.

Knockout of family with sequence similarity 170 member A (Fam170a) causes male subfertility, while Fam170b is dispensable in mice†

Families with sequence similarity 170 members A and B (FAM170A and FAM170B) are testis-specific, paralogous proteins that share 31% amino acid identity and are conserved throughout mammals. While previous in vitro experiments suggested that FAM170B, an acrosome-localized protein, plays a role in the mouse sperm acrosome reaction and fertilization, the role of FAM170A in the testis has not been explored. In this study, we used CRISPR/Cas9 to generate null alleles for each gene, and homozygous null (-/-) male mice were mated to wild-type females for 6 months to assess fertility. Fam170b-/- males were found to produce normal litter sizes and had normal sperm counts, motility, and sperm morphology. In contrast, mating experiments revealed significantly reduced litter sizes and a reduced pregnancy rate from Fam170a-/- males compared with controls. Fam170a-/-;Fam170b-/- double knockout males also produced markedly reduced litter sizes, although not significantly different from Fam170a-/- alone, suggesting that Fam170b does not compensate for the absence of Fam170a. Fam170a-/- males exhibited abnormal spermiation, abnormal head morphology, and reduced progressive sperm motility. Thus, FAM170A has an important role in male fertility, as the loss of the protein leads to subfertility, while FAM170B is expendable. The molecular functions of FAM170A in spermatogenesis are as yet unknown; however, the protein localizes to the nucleus of elongating spermatids and may mediate its effects on spermatid head shaping and spermiation by regulating the expression of other genes. This work provides the first described role of FAM170A in reproduction and has implications for improving human male infertility diagnoses.

Low-dose in utero exposure to finasteride promotes developmental changes in both male and female gerbil prostates

The prostate is an accessory reproductive gland that is sensitive to the action of exogenous compounds known as endocrine disrupters that alter normal hormonal function. Finasteride is a widely used chemical that acts to inhibit the conversion of testosterone in its most active form, dihydrotestosterone. It is known that intrauterine exposure to finasteride causes changes in the male prostate even at low dosages; however, it is not known whether these dosages are capable of causing changes in the female prostate, which is present in a large number of mammalian species, including humans. In the present study, histochemistry, immunohistochemistry, immunofluorescence, serological dosages, and three-dimensional reconstruction techniques were employed to evaluate the effects of intrauterine exposure to a low dose of finasteride (100 μg.BW/d) on postnatal prostate development in male and female Mongolian gerbils. The results indicate that the gerbil female prostate also undergoes alterations following intrauterine exposure to finasteride, exhibiting a thickening of periductal smooth muscle and increased stromal proliferation. There are also intersex differences in the impact of exposure on the expression of the androgen receptor, which was increased in males, and of the estrogen-α receptor, which was decreased in the male prostate but unchanged in females. Altogether, this study indicates there are sex differences in the effects of finasteride exposure even at low dosages.

Proteomic Changes in Human Sperm During Sequential in vitro Capacitation and Acrosome Reaction

The male gamete is not completely mature after ejaculation and requires further events in the female genital tract to acquire fertilizing ability, including the processes of capacitation and acrosome reaction. In order to shed light on protein changes experienced by the sperm cell in preparation for fertilization, a comprehensive quantitative proteomic profiling based on isotopic peptide labeling and liquid chromatography followed by tandem mass spectrometry was performed on spermatozoa from three donors of proven fertility under three sequential conditions: purification with density gradient centrifugation, incubation with capacitation medium, and induction of acrosome reaction by exposure to the calcium ionophore A23187. After applying strict selection criteria for peptide quantification and for statistical analyses, 36 proteins with significant changes in their relative abundance within sperm protein extracts were detected. Moreover, the presence of peptide residues potentially harboring sites for post-translational modification was revealed, suggesting that protein modification may be an important mechanism in sperm maturation. In this regard, increased levels of proteins mainly involved in motility and signaling, both regulated by protein modifiers, were detected in sperm lysates following incubation with capacitation medium. In contrast, less abundant proteins in acrosome-reacted cell lysates did not contain potentially modifiable residues, suggesting the possibility that all those proteins might be relocated or released during the process. Protein-protein interaction analysis revealed a subset of proteins potentially involved in sperm maturation, including the proteins Erlin-2 (ERLIN2), Gamma-glutamyl hydrolase (GGH) and Transmembrane emp24 domain-containing protein 10 (TMED10). These results contribute to the current knowledge of the molecular basis of human fertilization. It should now be possible to further validate the potential role of the detected altered proteins as modulators of male infertility.

Proteomic characterization of human sperm plasma membrane-associated proteins and their role in capacitation

BACKGROUND

Plasma membranes of ejaculated sperm are covered by epididymal and accessory glands secreted proteins that must be released from sperm surface during the female reproductive tract passage in order to capacitate and fertilize the oocyte.

OBJECTIVES

As human sperm plasma membrane-associated proteins (SMAP) have not yet been investigated, the aim of this study was to characterize the SMAP released during in vitro human capacitation and to study their possible role as decapacitation factors.

MATERIALS AND METHODS

SMAP were characterized by 2-dimensional electrophoresis and mass spectrometry analysis. Besides, we explored SMAP effects on motility, protein tyrosine phosphorylation, and calcium ionophore-induced acrosome reaction of spermatozoa either incubated for 6 h in capacitating medium ± SMAP or for 5 h in capacitating medium alone followed by incubation for 1 h ± SMAP.

RESULTS

Mass spectrometry analysis allowed the identification of 29 proteins, all of which have previously been identified in the human seminal fluid. Spermatozoa incubated for 6 h under capacitating conditions in the presence of the SMAP showed a significant decrease in the incidence of non-progressive motility, hyperactivation, protein tyrosine phosphorylation, and calcium ionophore-induced acrosome reaction. However, spermatozoa incubated for 5 h in capacitating medium and further incubated for 1 h with the SMAP showed a lower percentage of spermatozoa with non-progressive motility and hyperactivated cells but no effects on protein tyrosine phosphorylation were detected.

DISCUSSION AND CONCLUSIONS

Our results indicate that SMAP inhibit the progress of human sperm capacitation, but only motility changes related to capacitation may be reversed by these proteins. The study of the identified proteins on sperm function and their mechanisms of action on this cell may contribute to the understanding of their role during capacitation.

Proteins from male and female reproductive tracts involved in sperm function regulation

Spermatogenesis is a dynamic process that culminates in the production of mature spermatozoa in the seminiferous tubules of sexually mature animals. Although sperm leaving the testis are fully differentiated, they must further undergo two additional maturation steps before acquiring the capability to fertilize the egg. Such processes take place during the epididymal residency and transport in the seminal fluid during ejaculation and, after delivery into the female reproductive tract, during the journey aiming the encountering the egg in the oviduct. Throughout this trip, spermatozoa are exposed to different reproductive fluids whose molecular compositions regulate the progress towards obtaining a fertilized competent cell. This review summarizes the evidence obtained so far supporting the participation of male and female reproductive tract-derived proteins in the modulation of sperm fertilizing ability and discusses the mechanisms by which such regulation may be accomplished.

THE EFFECT OF HSP60 ON FERTILIZATION AND PRE-IMPLANTATION EMBRYO DEVELOPMENT IN MICE: AN IN VITRO STUDY

Context

Heat Shock Protein 60 (HSP60) is a chaperone protein which is involved in proteins transfer and re-folding of proteins.

Objective

Importance of HSP60 in sperm capacitation and facility of sperm-oocyte membrane binding was confirmed, therefore in this study the effect of HSP60 on the rate of in vitro fertilization and the cleavage rate in mouse embryo was investigated.

Design

Ten male mice and twenty five female mice were involved to collect sperms and oocytes required for this study.

Subjects and Methods

Sperms were collected from the epididymis of male mouse and oocytes were collected from the oviduct of female mouse following ovarian hyperstimulation. Then, capacitated sperms and oocytes were placed together in fertilization medium in four groups in the presence of different concentrations of HSP60 (10, 50 and 100 ng/mL) and in the absence of HSP60. After calculation of the fertilization rate, zygotes were transformed into the other medium for development and the cleavage rate was monitored to blastocyst stage.

Results

There was not a significant difference in the rate of fertilization between 10 ng/mL HSP60 group and the control group. The rate of fertilization and two-cell embryo development decreased significantly (P≤0.05) in 100 ng/mL HSP60 compared to other experimental and control groups. Further, the rate of two-cell embryo development increased significantly (P≤0.05) in 10 ng/mL HSP60 compared to other experimental and control groups.

Conclusions

The present study demonstrated that HSP60 in low dose had a positive effect on two-cell embryo development, however it did not have any significant effect on the fertilization rate. Conversely, HSP60 had adverse effects on the fertilization and cleavage rates at higher doses.

Understanding the seminal plasma proteome and its role in male fertility

Seminal plasma is a complex fluid comprised of secretions from the seminal vesicles, the prostate, bulbourethral glands and from the seminiferous tubule lumen / epididymides / vasa deferentia. While it has been established that seminal plasma serves not only as a medium to carry, protect, and nourish sperm after ejaculation up to fertilization, but also as a functional modulator of sperm function, there is still a need to properly characterize the molecular make-up of seminal plasma in fertile men, and to understand how this is altered in different causes of male infertility. The main purpose of this manuscript was to review articles that studied the human seminal plasma proteome, ranging from characterizing a fertile seminal plasma proteomic map to studies comparing seminal plasma from fertile and infertile men, and comparing seminal plasma of fertile or normozoospermic men to a diverse range of biological causes for male infertility. Finally, this review has focused on the association between semen and sperm functional quality and the seminal plasma proteome, in order to demonstrate cellular and molecular mechanisms of male infertility. Due to the untargeted nature of the majority of the studies presented in this review, and to the diverse range of techniques utilized to study the seminal plasma proteomic composition, many differentially expressed proteins were observed. However, in general, it seems that there is a seminal plasma proteome associated to male fertility, and that different biological conditions or cellular phenotypes shift its pathways away from its homeostatic condition to altered energy production pathways. Moreover, it seems there is an inflammatory component to the seminal plasma of infertile men. In conclusion, there are a number of studies focused on the proteomic composition of human seminal plasma; downstream confirmatory studies will help to understand specific pathways of infertility in different biological conditions.

Uterine flushings from women treated with levonorgestrel affect sperm functionality in vitro

Levonorgestrel (LNG), a synthetic 19 nor-testosterone derivative, is widely used for emergency contraception. It is well known that LNG prevents ovulation only when given prior to the surge of serum luteinizing hormone (LH) during the periovulatory phase of the menstrual cycle. This observation suggests that LNG, given its contraceptive efficacy, has additional effects other than those affecting ovulation. In this study, we have evaluated the effects on human sperm functionality of uterine flushings (UF) obtained from women at day LH + 1 of a control cycle (CTR-LH + 1) and after receiving LNG (LNG-LH + 1) two days before the surge of LH. Human sperm from normozoospermic donors were incubated with UF and protein tyrosine phosphorylation, sperm motility, acrosome reaction as well as zona pellucida (ZP) binding capacity were assessed. A significant decrease in total motility and tyrosine phosphorylation accompanied by an increase on spontaneous acrosome reaction was observed when sperm were incubated in the presence of LNG-LH + 1. None of these effects were mimicked by purified glycodelin A (GdA). Moreover, the addition of UF obtained during the periovulatory phase from LNG-treated women or the presence of purified GdA significantly decreased sperm-ZP binding. The data were compatible with changes affecting sperm capacitation, motility and interaction with the ZP. These results may offer evidence on additional mechanisms of action of LNG as an emergency contraceptive.

Biological basis for human capacitation-revisited

BACKGROUND

A little more than a decade ago a review entitled 'Biological basis for human capacitation' was published. A primary conclusion of the review was that with all the technological advances that have been made since the first experiments demonstrated the in vivo requirement of capacitation for fertilization, very little progress had since been made, most significantly for human.

OBJECTIVE AND RATIONALE

The present review was carried out to provide an update on the biological basis for human capacitation. It briefly revisits the original schema, presents a review of the literature that urged research interest in human sperm capacitation and puts under the spotlight the original definition of capacitation balanced against the limitations of experiments in vitro to characterize a complex process that necessarily mandates a female component, and very recent findings in the mouse. It also includes proposed considerations for new thinking regarding capacitation, and progress toward understanding the biology of human capacitation.

SEARCH METHODS

The PubMed, Google Scholar and Scopus literature databases were reviewed extensively using inclusive, broad and multispecies search terms without publication date limitation.

OUTCOMES

Comprehensive screening of the literature database showed that no papers regarding human sperm capacitation in vivo have been published in the past 20 years. Recent experiments in the mouse have provided compelling and unanticipated data regarding capacitation and in vivo fertilization. Questions were posed and addressed regarding: stimuli for initiation of capacitation, capacitation relative to the cumulus-oocyte complex, comparison between in vivo and in vitro capacitation, and potential species-specific differences in location and timing of capacitation.

WIDER IMPLICATIONS

There has been no progress on the in vivo biology of human sperm capacitation since before the turn of the century. Human IVF and its technologies may likely have inhibited, and continue to hold back, any future in vivo experiments that would address one or more questions regarding acquisition of fertilizing capacity in human. The limiting factor for progress in the area is access to funding and human subjects.

Lead Inhibits Human Sperm Functions by Reducing the Levels of Intracellular Calcium, cAMP, and Tyrosine Phosphorylation

It is well known that there has been a worldwide decrease in human male fertility in recent years. One of the main factors affecting this is environmental pollution. Lead is one of the major heavy metal contaminants that threaten the health of animals and human beings in China. It preferentially accumulates in male reproductive organs and can be up to 10 µM in human seminal plasma. Lead impairs mammalian spermatogenesis and sperm quality in vivo. It also inhibits sperm functions in vitro but the underlying mechanisms remain unclear. Therefore, we aimed to investigate the in vitro toxicity of lead on human sperm functions and to elucidate the underlying mechanisms. Semen samples were collected from 20 healthy volunteers with different careers and backgrounds living in Nanchang, Jiangxi. Human sperm suspensions were treated with different concentrations of lead acetate (0, 0.5, 2.5, 10, 50, and 100 µM) and the viability, motility, capacitation and progesterone-induced acrosome reaction were examined. Treatment with 10-100 µM lead acetate dose-dependently inhibited total and progressive motility measures, capacitation and progesterone-induced acrosome reaction. It also dose-dependently decreased the intracellular concentrations of cyclic adenosine monophosphate (cAMP) and calcium ([Ca(2+)]i), and reduced the tyrosine phosphorylation of sperm proteins, all of which are thought to be key factors in the regulation of sperm function. Our findings suggest that lead inhibits human sperm functions by reducing the levels of sperm intracellular cAMP, [Ca(2+)]i and tyrosine phosphorylation of sperm proteins in vitro.

Lipopolysaccharide Compromises Human Sperm Function by Reducing Intracellular cAMP

A worldwide decline in the quality of human semen is currently occurring. In mammals, sperm are produced from diploid stem-cell spermatogonia by spermatogenesis in testes and become mature in epididymis. Nevertheless, these biological processes can be affected by Gram-negative bacterial infection mediated by lipopolysaccharide (LPS), the major endotoxin of Gram-negative bacteria. It is well known that LPS can disturb spermatogenesis and affect sperm maturation and quality in vivo. However, the effect of LPS on the ejaculated mature sperm in vitro remains unclear. Thus, this study aimed to assess the in vitro toxicity of LPS on human sperm function and to elucidate the underlying mechanism. Human sperm were incubated with LPS (0.1-100 μg/ml) for 1-12 h in vitro and, subsequently, sperm viability, motility and capacitation, and the acrosome reaction were examined. LPS dose-dependently inhibited total and progressive motility and the ability to move through a viscous medium of the sperm but did not affect sperm viability, capacitation, and the acrosome reaction. To explore the underlying mechanism of LPS's actions, we examined the effects of LPS on the intracellular concentrations of cyclic adenosine monophosphate (cAMP) and calcium ([Ca(2+)]i) and protein-tyrosine phosphorylation of human sperm, which are key regulators of human sperm function. LPS decreased intracellular cAMP dose-dependently but had no effect on [Ca(2+)]i and protein-tyrosine phosphorylation of human sperm. These findings suggest that LPS inhibits human sperm motility by decreasing intracellular cAMP.

Modulation of Human Sperm Capacitation by Progesterone, Estradiol, and Luteinizing Hormone

Sperm residency in female reproductive tract is essential to undergo functional changes that allow the cell to encounter the oocyte and fertilize it. Those changes, known as capacitation, are modulated by molecules located in the uterotubal surface and fluids. During the fertile window, there is a notable increase in some reproductive hormones such as progesterone, estradiol, and luteinizing hormone in the female reproductive tract, so spermatozoa are exposed to these hormones in an environment that must favor gamete encountering and fusion. This spatiotemporal coincidence suggests that they are suitable candidates to modulate sperm function in order to synchronize the events that ultimately allow the success of fertilization. The presence of receptors for these hormones in the human sperm has been described, but their physiological relevance and mechanisms of action have been either subject of controversy or not properly investigated. This review intends to summarize the evidence that support the participation of these hormones in the regulation of sperm capacitation.

Uterosome-like vesicles prompt human sperm fertilizing capability

STUDY QUESTION

Does the rapid transit through the uterine environment modulate the sperm physiological state?

SUMMARY ANSWER

The uterosome-like vesicles (ULVs) secreted by endometrial epithelial cells (EECs) in vitro are able to fuse with human spermatozoa, prompting their fertilizing capacity.

WHAT IS KNOWN ALREADY

Early studies suggest that sperm capacitation begins in the uterus and ends in the oviduct, and that a synergistic effect of both female organs may accelerate this process. Although it has been reported that co-incubation of human spermatozoa with endometrial cell-conditioned medium (CM) stimulates sperm capacitation, the mechanism mediating this communication is unknown.

STUDY DESIGN, SIZE, DURATION

Human ULVs secreted by EECs were characterized and their effect on human sperm physiology was analysed. Spermatozoa were incubated with EEC-derived CM or ULV, after which sperm capacitation was evaluated at different time points. In addition, the interaction of spermatozoa with ULV was analysed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

ULVs were isolated by ultracentrifugation and identified using electron microscopy and Western blotting to assess the presence of specific protein markers. Following seminal plasma removal, human spermatozoa were incubated CM or ULV, after which sperm capacitation was evaluated as the ability of the sperm to undergo the induced acrosome reaction and the level of protein tyrosine phosphorylation (PY) determined by Western blot and immunocytochemistry. The interaction of spermatozoa with labelled ULV was analysed by fluorescence microscopy. In all cases, at least three biological replicates from different sperm donors were performed for each set of experiments. Significant differences between mean values were determined by one-way ANOVA followed by Tukey's post hoc test. Differences between treatments were considered statistically significant at P ≤ 0.05.

MAIN RESULTS AND THE ROLE OF CHANCE

The level of capacitated spermatozoa and those recruited by chemotaxis increased 3- to 4-fold when spermatozoa were incubated in the presence of CM for 4 h. Even a 15 min incubation of spermatozoa with CM was also enough to increase the level of capacitated cells 3- to 4-fold (P < 0.05). Furthermore, a short co-incubation of spermatozoa with ULV stimulates sperm capacitation, as determined by the increase in the level of induced acrosome reaction and the induction of PY. In addition, after the co-incubation of spermatozoa with fluorescent labelled ULV, the sperm cells acquired the fluorescent staining which indicates that ULV might be transferred to the sperm surface by a fusion mechanism.

LIMITATIONS, REASONS FOR CAUTION

This is an in vitro study performed with human biological material, spermatozoa and endometrial derived cells; the latter being a cell line originally isolated from a uterine adenocarcinoma.

WIDER IMPLICATIONS OF THE FINDINGS

The capability of spermatozoa to briefly interact with ULVs supports the hypothesis that any step of sperm transport may have physiological consequences, despite the interaction lasting for only a limited period of time. This way of communication of spermatozoa with cell products of uterine origin opens new frontiers of investigation (e.g. the signalling molecules involved), shedding light on the sperm processes that prepare the male gamete for fertilization, which might have implications for human infertility treatment.

LARGE SCALE DATA

N/A.

STUDY FUNDING AND COMPETING INTERESTS

The project was financially supported by SECyT-UNC. The authors declare no conflict of interest.

Effects of Synthetic Serum Supplementation in Sperm Preparation Media on Sperm Capacitation and Function Test Results

Albumin supplementation of culture media induces sperm capacitation in assisted reproduction technique cycles. Synthetic serum supplementation is clinically used to replace albumin for preventing transmission of infectious agents. However, the effects of synthetic serum supplementation on sperm capacitation have rarely been investigated. Spermatozoa from 30 men with normal basic semen analysis results were collected, divided into five aliquots, and cultured in capacitating conditions in four combinations of two synthetic serum supplements, serum substitute supplement (SSS) and serum protein substitute (SPS), and two fertilization media, Quinns Advantage™ Fertilization (QF) and human tubular fluid (HTF) media. Reactive oxygen species (ROS) levels in spermatozoa were measured through chemiluminescence. Furthermore, acrosome reaction and western blotting for tyrosine phosphorylation were used to evaluate sperm capacitation. HTF+SSS had significantly higher ROS levels than QF+SPS did (11,725 ± 1,172 versus 6,278 ± 864 relative light units). In addition, the spermatozoa cultured in QF+SPS had lower motility, acrosome reaction rates, and tyrosine phosphorylation levels compared with those cultured in HTF+SSS. In conclusion, the effects of synthetic serum supplementation on sperm capacitation varied according to the combination of media. These differences may lead to variations in spermatozoon ROS levels, thus affecting sperm function test results.

A Preliminary Study: N-acetyl-L-cysteine Improves Semen Quality following Varicocelectomy

Background

Surgery is considered the primary treatment for male infertility from clinical varicocele. One of the main events associated with varicocele is excessive production of reactive oxygen species (ROS). N-acetyl-L-cysteine (NAC), an antioxidant that scavenges free radicals, is considered a supplement to alleviate glutathione (GSH) depletion during oxidative stress. Despite beneficial effects of NAC in other pathological events, there is no report on the effect of NAC in individuals with varicocele. Therefore, the aim of this study is to evaluate the outcome of NAC on semen quality, protamine content, DNA damage, oxidative stress and fertility following varicocelectomy.

Materials and Methods

This prospective clinical trial included 35 infertile men with varicocele randomly divided into control (n=20) and NAC (n=15) groups. We assessed semen parameters, protamine content [chromomycin A3 (CMA3)], DNA integrity [terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling (TUNEL)] and oxidative stress [2', 7'-dichlorodihydrofluorescein-diacetate (DCFH-DA)] before and three months after varicocelectomy.

Results

Percentage of abnormal semen parameters, protamine deficiency, DNA fragmentation and oxidative stress were significantly decreased in both groups compared to before surgery. We calculated the percentage of improvement in these parameters compared to before surgery for each group, then compared the results between the groups. Only percentage of protamine deficiency and DNA fragmentation significantly differed between the NAC and control groups.

Conclusion

The results of this study, for the first time, revealed that NAC improved chromatin integrity and pregnancy rate when administered as adjunct therapy post-varico- celectomy (Registeration Number: IRCT201508177223N5).

Matrine compromises mouse sperm functions by a [Ca(2+)]i-related mechanism

Matrine, a bioactive alkaloid widely used in Chinese medicine, inhibits mouse sperm functions in vitro. In this study, we investigated the reproductive toxicity of matrine to male mice in vivo. C57BL/6J mice were administered with daily doses of 0, 1, 10 and 50mg/kg matrine by intraperitoneal injection for 30 days. The results showed that matrine did not affect testis size, testis weight, sperm count and sperm viability, but it significantly inhibited total motility, progressive motility, linear velocity, capacitation and the progesterone-induced acrosome reaction of mouse sperm. Furthermore, the intracellular Ca(2+) concentration ([Ca(2+)]i), a key regulator of sperm function, was reduced in sperm of matrine-exposed mice. The current and gene expression of the sperm specific Ca(2+) channel, CatSper, which modulates Ca(2+) influx in sperm, were decreased in testes of matrine-exposed mice. These results indicate that matrine inhibits mouse sperm functions by a [Ca(2+)]i-related mechanism via CatSper channel.

Towards Understanding Male Infertility After Spinal Cord Injury Using Quantitative Proteomics

The study of male infertility after spinal cord injury (SCI) has enhanced the understanding of seminal plasma (SP) as an important regulator of spermatozoa function. However, the most important factors leading to the diminished sperm motility and viability observed in semen of men with SCI remained unknown. Thus, to explore SP related molecular mechanisms underlying infertility after SCI, we used mass spectrometry-based quantitative proteomics to compare SP retrieved from SCI patients to normal controls. As a result, we present an in-depth characterization of the human SP proteome, identifying ∼2,800 individual proteins, and describe, in detail, the differential proteome observed in SCI. Our analysis demonstrates that a hyper-activation of the immune system may influence some seminal processes, which likely are not triggered by microbial infection. Moreover, we show evidence of an important prostate gland functional failure,i.e.diminished abundance of metabolic enzymes related to ATP turnover and those secreted via prostasomes. Further we identify the main outcome related to this fact and that it is intrinsically linked to the low sperm motility in SCI. Together, our data highlights the molecular pathways hindering fertility in SCI and shed new light on other causes of male infertility.

Protein profile screening: reduced expression of Sord in the mouse epididymis induced by nicotine inhibits tyrosine phosphorylation level in capacitated spermatozoa

Many studies have revealed the hazardous effects of cigarette smoking and nicotine exposure on male fertility, but the actual, underlying molecular mechanism remains relatively unclear. To evaluate the detrimental effects of nicotine exposure on the sperm maturation process, two-dimensional gel electrophoresis and mass spectrometry analyses were performed to screen and identify differentially expressed proteins from the epididymal tissue of mice exposed to nicotine. Data mining analysis indicated that 15 identified proteins were mainly involved in the molecular transportation process and the polyol pathway, indicating impaired epididymal secretory functions. Experiments in vitro confirmed that nicotine inhibited tyrosine phosphorylation levels in capacitated spermatozoa via the downregulated seminal fructose concentration. Sord, a key gene encoding sorbitol dehydrogenase, was further investigated to reveal that nicotine induced hyper-methylation of the promoter region of this gene. Nicotine-induced reduced expression of Sord could be involved in impaired secretory functions of the epididymis and thus prevent the sperm from undergoing proper maturation and capacitation, although further experiments are needed to confirm this hypothesis.

Effects of lactoferrin, a protein present in the female reproductive tract, on parameters of human sperm capacitation and gamete interaction

In a recent study, lactoferrin (LF) was detected in human oviductal secretion. The protein was able to bind to oocytes and sperm, and modulated gamete interaction. The aim of the present study was to investigate the effect of LF on parameters related to human sperm capacitation and sperm-zona pellucida interaction. Semen samples were obtained from healthy normozoospermic donors (n = 7). Human follicular fluids and oocytes were collected from patients undergoing in vitro fertilization. Motile sperm obtained by swim-up were incubated for 6 or 22 h under capacitating conditions with LF (0-100 μg/mL). After incubations, viability, motility, presence of α-d-mannose receptors (using a fluorescent probe on mannose coupled to bovine serum albumin), spontaneous and induced acrosome reaction (assessed with Pisum sativum agglutinin conjugated to fluorescein isothiocyanate), and tyrosine phosphorylation of sperm proteins were evaluated. Sperm-zona pellucida interaction in the presence of LF was investigated using the hemizone assay. The presence of LF did not affect sperm viability or motility, but caused a dose-dependent significant decrease in sperm α-d-mannose-binding sites, and the effect was already significant with the lowest concentration of the protein used after 22 h incubation. Dose-dependent significant increases in both induced acrosome reaction and tyrosine phosphorylation of sperm proteins were observed in the presence of LF. The present data indicate that LF modulates parameters of sperm function. The inhibition of gamete interaction by LF could be partially explained by the decrease in sperm d-mannose-binding sites. The presence of the LF promoted sperm capacitation in vitro.

In vitro fertilization in pigs: New molecules and protocols to consider in the forthcoming years

Assisted reproduction technology (ART) protocols are used in livestock for the improvement and preservation of their genetics and to enhance reproductive efficiency. In the case of pigs, the potential use of embryos for biomedicine is being followed with great interest by the scientific community. Owing to the physiological similarities with humans, embryos produced in vitro and many of those produced in vivo are used in research laboratories for the procurement of stem cells or the production of transgenic animals, sometimes with the purpose of using their organs for xenotransplantation. Several techniques are required for the production of an in vitro-derived embryo. These include in vitro oocyte maturation, sperm preparation, IVF, and further culture of the putative zygotes. Without doubt, among these technologies, IVF is still a critical limiting factor because of the well-known, but still unsolved, question of polyspermy. Despite the improvements made in the past decade, current IVF systems hardly reach 50% to 60% efficiency and any progression in porcine ARTs requires an unavoidable improvement in the monospermy rate. It is time, then, to learn from what happens under in vivo physiological conditions and to transfer this knowledge into ART. This review describes the latest advances in porcine IVF, from sperm preparation procedures to culture media supplements with special attention paid to molecules with a known or potential role in in vivo fertilization. Oviductal fluid is the natural medium in which fertilization takes place, and, in the near future, could become the definitive supplement for culture media, where it would help to solve many of the problems inherent in ARTs in swine and improve the quality of in vitro-derived porcine embryos.

Discovery, primary, and crystal structures and capacitation-related properties of a prostate-derived heparin-binding protein WGA16 from boar sperm

Mammalian sperm acquire fertility through a functional maturation process called capacitation, where sperm membrane molecules are drastically remodeled. In this study, we found that a wheat germ agglutinin (WGA)-reactive protein on lipid rafts, named WGA16, is removed from the sperm surface on capacitation. WGA16 is a prostate-derived seminal plasma protein that has never been reported and is deposited on the sperm surface in the male reproductive tract. Based on protein and cDNA sequences for purified WGA16, it is a homologue of human zymogen granule protein 16 (ZG16) belonging to the Jacalin-related lectin (JRL) family in crystal and primary structures. A glycan array shows that WGA16 binds heparin through a basic patch containing Lys-53/Lys-73 residues but not the conventional lectin domain of the JRL family. WGA16 is glycosylated, contrary to other ZG16 members, and comparative mass spectrometry clearly shows its unique N-glycosylation profile among seminal plasma proteins. It has exposed GlcNAc and GalNAc residues without additional Gal residues. The GlcNAc/GalNAc residues can work as binding ligands for a sperm surface galactosyltransferase, which actually galactosylates WGA16 in situ in the presence of UDP-Gal. Interestingly, surface removal of WGA16 is experimentally induced by either UDP-Gal or heparin. In the crystal structure, N-glycosylated sites and a potential heparin-binding site face opposite sides. This geography of two functional sites suggest that WGA16 is deposited on the sperm surface through interaction between its N-glycans and the surface galactosyltransferase, whereas its heparin-binding domain may be involved in binding to sulfated glycosaminoglycans in the female tract, enabling removal of WGA16 from the sperm surface.

Emodin inhibits human sperm functions by reducing sperm [Ca(2+)]i and tyrosine phosphorylation

Emodin, a bioactive anthraquinone widely used in Chinese traditional medicine, disrupts mouse testicular gene expression in vivo. In this study, we investigated the toxicity of emodin to human sperm in vitro. Different doses of emodin (25, 50, 100, 200 and 400μM) were applied to ejaculated human sperm. The results indicated that 100, 200 and 400μM emodin significantly inhibited the total motility, progressive motility and linear velocity of human sperm. In addition, sperm's ability to penetrate viscous medium together with progesterone induced capacitation and acrosome reaction was also adversely affected by emodin. In contrast, emodin did not affect sperm viability. Furthermore, intracellular Ca(2+) concentration ([Ca(2+)]i) and tyrosine phosphorylation, which serve as key regulators of sperm function, were dose-dependently reduced by emodin (50-400μM). These results suggest that emodin inhibits human sperm functions by reducing sperm [Ca(2+)]i and suppressing tyrosine phosphorylation in vitro.

The mechanics of hyperactivation in adhered human sperm

Hyperactivation is an important phenomenon exhibited by mammalian sperm during the process of acquiring fertilization capacity. The majority of studies have focused on incubation-induced hyperactivation in non-human species, which typically differ in size, shape, and are more homogeneous than human sperm. We develop an alternative approach via drug-induction, using high-speed imaging and analysis of same-cell changes in the flagellar movement of adhered cells. Following stimulation with 4-aminopyridine, approximately two-thirds (21 of 34) of the cells analysed exhibited a waveform with a single characteristic frequency; in all cases, the frequency was lower than before stimulation. The remaining cells (13 of 34) exhibited a more complex motility with multiple-frequency modes. The lowest mode in all cases was lower than the frequency prior to stimulation. Flagellar bending increased in all cells following stimulation and was significantly greater in the multiple-frequency responders. Despite the increased bending, time-averaged hydrodynamic power dissipation decreased significantly when assessed across all cells, the effect being significantly greater in the multiple-frequency responders than single frequency. These results reveal the heterogeneity of responses of human sperm to a hyperactivating stimulus, the methodology being potentially useful for assessing dynamic responses to stimuli in human sperm, and physiological selection of cells for assisted reproduction.

Differential protein expression in seminal plasma from fertile and infertile males

AIM

The aim of this study was to analyze human seminal plasma proteins in association with male fertility status using the proteomic mass spectrometry technology Surface-Enhanced Laser Desorption Ionization Time-of-Flight (SELDI-TOF-MS).

MATERIALS AND METHODS

Semen analysis was performed using conventional methods. Protein profiles of the seminal plasma were obtained by SELDI-TOF mass spectrometry over a strong anion exchanger, ProteinChip(®) Q10 array.

RESULTS AND CONCLUSION

We found statistically significant differences in motility and sperm count between fertile and infertile men. In addition, we observed ten seminal proteins that are significantly up-regulated in the infertile group. In conclusion, comparison of seminal plasma proteome in fertile and infertile men provides new aspects in the physiology of male fertility and might help in identifying novel markers of male infertility.

Bioenergetics of mammalian sperm capacitation

After ejaculation, the mammalian male gamete must undergo the capacitation process, which is a prerequisite for egg fertilization. The bioenergetics of sperm capacitation is poorly understood despite its fundamental role in sustaining the biochemical and molecular events occurring during gamete activation. Glycolysis and mitochondrial oxidative phosphorylation (OXPHOS) are the two major metabolic pathways producing ATP which is the primary source of energy for spermatozoa. Since recent data suggest that spermatozoa have the ability to use different metabolic substrates, the main aim of this work is to present a broad overview of the current knowledge on the energy-producing metabolic pathways operating inside sperm mitochondria during capacitation in different mammalian species. Metabolism of glucose and of other energetic substrates, such as pyruvate, lactate, and citrate, is critically analyzed. Such knowledge, besides its obvious importance for basic science, could eventually translate into the development of novel strategies for treatment of male infertility, artificial reproduction, and sperm selection methods.

Effect of oxamic analogues on functional mice sperm parameters

The present study evaluates the effect of oxamate derivatives (N-ethyl, N-propyl, N-butyl oxamates) on functional murine sperm parameters, towards a new male non-hormonal contraceptive. These derivatives are selective inhibitors of lactate dehydrogenase-C4 (LDH-C4). LDH-C4 is a sperm-specific enzyme that plays an important role in ATP production for maintaining progressive motility as well as to induce capacitation and hyperactivation. The results demonstrate that all oxamate derivatives selectively inhibited LDH-C4 in mouse sperm extracts. The IC(50) values for hexokinase and glyceraldehyde-3-phosphate dehydrogenase were at least an order of magnitude greater than LDH-C4 IC(50) values. Prodrugs of oxamate derivatives assayed on sperm cells diminished normal sperm motility parameters, acrosome reaction, and cell viability in a concentration dependent manner. Also, we performed in vivo studies to determine the potential toxicity and possible contraceptive ability of these inhibitors. Mouse sperm were more sensitive to the N-butyl oxamate ethyl ester (NBOXet). Furthermore, results showed that NBOXet was of a low toxicity substance that diminished the total and progressive motility as well as the kinematic parameters of sperm cells. Data from in vitro and in vivo studies showed that N-butyl oxamate and its prodrug, are selective inhibitors of sperm LDH-C4, has low toxicity, and inhibits sperm progressive motility, offering some of the desirable characteristics of a male contraceptive: effect, low toxicity, and selectivity.

Phenotype and functionality of CD4+ and CD8+ T cells in the upper reproductive tract of healthy premenopausal women

PROBLEM

The goal of this study was to investigate the phenotype and functional responsiveness of CD4(+) and CD8(+) T-cells in the upper reproductive tract of healthy premenopausal women. The lower reproductive tract is frequently studied as a site of sexually transmitted infections; however, the upper reproductive tract may also be a portal of entry and dissemination for pathogens, including HIV-1.

METHOD OF STUDY

Endometrial biopsy, endocervical curettage, cytobrush, and blood were collected during mid-luteal phase from 23 healthy women. T-cells were isolated and analyzed by flow cytometry.

RESULTS

As compared with their counterparts in blood, endometrial and endocervical T-cells had enhanced CCR5 expression, and were enriched for activated, effector memory cells. Endometrial T-cells were more responsive to polyclonal stimuli, producing a broad range of cytokines and chemokines.

CONCLUSION

These findings underscore the responsiveness of endometrial T-cells to stimulation, and reveal their activated phenotype. These findings also suggest susceptibility of the upper reproductive tract to HIV-1 infection.