Comparison of human cervical mucus and artificial sperm penetration media

Phosphodiesterase 10A inhibitor PF-2545920 as a prospective agent for the clinical promotion of sperm motility

Phosphodiesterase (PDE) inhibitors can improve sperm motility in patients with asthenozoospermia. However, the most commonly reported nonselective PDE inhibitor pentoxifylline and PDE5 inhibitor sildenafil have the disadvantages of requiring a high concentration and destroying sperm integrity. We examined the PDE10A inhibitor PF-2545920 to compare its ability to promote sperm motility with that of pentoxifylline and sildenafil. After seminal plasma was discarded, several semen samples were subjected to four treatments (control, PF-2545920, pentoxifylline, and sildenafil) to evaluate their ability to affect motility, viability, and spontaneous acrosome reactions. Intracellular calcium and adenosine triphosphate (ATP), mitochondrial membrane potential, and penetration through viscous medium were assessed by flow cytometry, luciferase, and hyaluronic acid after treatment with PF-2545920. Statistical analyses were performed using the analysis of variance statistical test. PF-2545920 elevated the percentage of motile spermatozoa compared to the control, pentoxifylline, and sildenafil groups at 10 µmol l -1 ( P < 0.01). It is less toxic to GC-2spd mouse spermatocytes cells and spermatozoa and causes fewer spontaneous acrosomal reactions ( P < 0.05). PF-2545920 also increased mitochondrial membrane potential ( P < 0.001) and altered intracellular calcium ( P < 0.05) in a dose-dependent manner, including increasing sperm hyaluronic acid penetrating ability ( P < 0.05). Therefore, PF-2545920 might be an excellent choice for stimulating the sperm motility.

Cervix chip mimicking cervical microenvironment for quantifying sperm locomotion

As the gate for sperm swimming into the female reproductive tract, cervix is full of cervical mucus, which plays an important role in sperm locomotion. The fact that sperm cannot pass through the cervical mucus-cervix microenvironment will cause the male infertility. However, how the sperm swim across the cervix microenvironment remains elusive. We used hyaluronic acid (HA), a substitute of cervical mucus to mimic cervix microenvironment and designed a cervix chip to study sperm selection and behavior. An accumulation of sperm in HA confirmed that HA served as a reservoir for sperm, similar to cervical mucus. We found that sperm escaping from HA exhibited higher motility than the sperm accessing into HA, suggesting that HA functions as a filter to select sperm with high activity. Our findings construct a practical platform to explore the sophisticated interaction of sperm with cervix microenvironment, with elaborate swimming indicators thus provide a promising cervix chip for sperm selection with kinematic features on-demand. What's more, the cervix chip allows the convenient use in clinical infertility diagnosis, owing to the advantage of simple, fast and high efficiency.

Simulating nature in sperm selection for assisted reproduction

Sperm selection in the female reproductive tract (FRT) is sophisticated. Only about 1,000 sperm out of millions in an ejaculate reach the fallopian tube and thus have a chance of fertilizing an oocyte. In assisted reproduction techniques, sperm are usually selected using their density or motility, characteristics that do not reflect their fertilization competence and, therefore, might result in failure to fertilize the oocyte. Although sperm processing in in vitro fertilization (IVF) and intrauterine insemination (IUI) bypasses many of the selection processes in the FRT, selection by the cumulus mass and the zona pellucida remain intact. By contrast, the direct injection of a sperm into an oocyte in intracytoplasmic sperm injection (ICSI) bypasses all natural selection barriers and, therefore, increases the risk of transferring paternal defects such as fragmented DNA and genomic abnormalities in sperm to the resulting child. Research into surrogate markers of fertilization potential and into simulating the natural sperm selection processes has progressed. However, methods of sperm isolation - such as hyaluronic acid-based selection and microfluidic isolation based on sperm tactic responses - use only one or two parameters and are not comparable with the multistep sperm selection processes naturally occurring within the FRT. Fertilization-competent sperm require a panel of molecules, including zona pellucida-binding proteins and ion channel proteins, that enable them to progress through the FRT to achieve fertilization. The optimal artificial sperm selection method will, therefore, probably need to use a multiparameter tool that incorporates the molecular signature of sperm with high fertilization potential, and their responses to external cues, within a microfluidic system that can replicate the physiological processes of the FRT in vitro.

Ram spermatozoa migrating through artificial mucus in vitro have reduced mitochondrial membrane potential but retain their viability

Sperm motility in vitro is one of the most common predictors of fertility in male screening. We propose that a mucus-penetration assay can isolate a cellular subpopulation critical to reproductive success. To this end, a device was designed with three modules (sample, test and collection) and its conditions of use evaluated (length of mucus, incubation time, mucus medium, sperm concentration and position in relation to the horizontal). The number of spermatozoa migrating and the viability and acrosomal status of the spermatozoa not migrating were calculated. The second objective was to evaluate the qualitative parameters of the spermatozoa migrating in 1.6% polyacrylamide for 30 min. The number of spermatozoa migrating and the sperm motility, viability and the acrosomal and mitochondrial status of three sperm populations (fresh, not migrating and migrating) were determined. A higher number of migrating spermatozoa were observed after 60 min of incubation, but this situation adversely affected sperm quality. The methylcellulose-based test showed a significantly lower number of migrating spermatozoa than the polyacrylamide test. The position at an angle of 45° resulted in a higher number of migrating spermatozoa in the polyacrylamide-based test. The sperm counts for three consecutive assays indicated an acceptable repeatability of the method. The viability and acrosomal status of the migrating spermatozoa showed no significant changes with regard to the control when the device was placed at 45°, whereas these parameters showed lower values at 0°. The percentage of high mitochondrial membrane potential spermatozoa was significantly reduced in the population of migrating spermatozoa.

A common mutation in the defensin DEFB126 causes impaired sperm function and subfertility

A glycosylated polypeptide, β-defensin 126 (DEFB126), derived from the epididymis and adsorbed onto the sperm surface, has been implicated in immunoprotection and efficient movement of sperm in mucosal fluids of the female reproductive tract. Here, we report a sequence variant in DEFB126 that has a two-nucleotide deletion in the open reading frame, which generates an abnormal mRNA. The allele frequency of this variant sequence was high in both a European (0.47) and a Chinese (0.45) population cohort. Binding of the Agaricus bisporus lectin to the sperm surface glycocalyx was significantly lower in men with the homozygous variant (del/del) genotype than in those with either a del/wt or a wt/wt genotype, suggesting an altered sperm glycocalyx with fewer O-linked oligosaccharides in del/del men. Moreover, sperm from del/del carriers exhibited an 84% reduction in the rate of penetration of a hyaluronic acid gel, a surrogate for cervical mucus, compared to the other genotypes. This reduction in sperm performance in hyaluronic acid gels was not a result of decreased progressive motility (average curvilinear velocity) or morphological deficits. Nevertheless, DEFB126 genotype and lectin binding were correlated with sperm performance in the penetration assays. In a prospective cohort study of newly married couples who were trying to conceive by natural means, couples were less likely to become pregnant and took longer to achieve a live birth if the male partner was homozygous for the variant sequence. This common sequence variation in DEFB126, and its apparent effect of impaired reproductive function, will allow a better understanding, clinical evaluation, and possibly treatment of human infertility.

Defending male fertility

An estimated 10 to 15% of couples suffer from infertility, and many treatment decisions rely on trial and error. In this issue of Science Translational Medicine, Tollner and colleagues provide strong evidence from a human genetics study that a common variant in the beta defensin 126 gene, the "del" variant, can reduce male fertility substantially. In addition, they show a plausible mechanism for reduced fertility: Sperm from del/del homozygotes lack an important component of their glycoprotein coat and have difficulty penetrating a surrogate for cervical mucus. If replicated in future studies, these findings promise to guide choices about the timing and type of assisted reproduction interventions-and further hint at the possibility of treating sperm from del/del homozygotes to promote fertility.

Frozen-thawed rhesus sperm retain normal morphology and highly progressive motility but exhibit sharply reduced efficiency in penetrating cervical mucus and hyaluronic acid gel

The preservation of the genetic diversity of captive populations of rhesus monkeys is critical to the future of biomedical research. Cryopreservation of rhesus macaque sperm is relatively simple to perform, yields high post-thaw motility, and theoretically, provides via artificial insemination (AI) a way to easily transfer genetics among colonies of animals. In the interest of optimizing semen cryopreservation methods for use with vaginal AI, we evaluated the ability of frozen-thawed rhesus sperm to penetrate periovulatory cervical mucus (CM). Motile sperm concentration of pre-freeze ("fresh") and post-thawed ("thawed") samples from five different males were normalized for both computer assisted sperm motion analysis and CM penetration experiments. Sperm samples were deposited into slide chambers containing CM or gel composed of hyaluronic acid (HA) as a surrogate for CM and numbers of sperm were recorded as they entered a video field a preset distance from the sperm suspension-CM (or HA) interface. Fresh and thawed sperm were dried on glass slides, "Pap"-stained, and assessed for changes in head dimensions and head and flagellar shape. While retaining better than 80% of fresh sperm progressive motility, thawed sperm from the same ejaculate retained on average only 18.6% of the CM penetration ability. Experiments using HA gel yielded similar results only with reduced experimental error and thus improved detection of treatment differences. Neither the percentage of abnormal forms nor head dimensions differed between fresh and thawed sperm. While findings suggests that sperm-CM interaction is a prominent factor in previous failures of vaginal AI with cryopreserved macaque sperm, neither sperm motility nor morphology appears to account for changes in the ability of cryopreserved sperm to penetrate CM. Our data points to a previously unidentified manifestation of cryodamage which may have implications for assessment of sperm function beyond the cervix and across mammalian species.

CASA assessment of kinematic parameters of ram spermatozoa and their relationship to migration efficiency in ruminant cervical mucus

Sperm motility is an indicator of male fertility because of its importance for sperm migration through the female genital tract and for gamete interaction at fertilization. This study analyses the relationship between computer assisted semen analysis (CASA) motility patterns and sperm migration of rams in ruminant cervical mucus. In experiment 1, spermatozoa extended with sperm analysis medium (SAM) and seminal plasma were compared in terms of motility. In experiment 2, 56 semen samples were collected either with artificial vagina (AV) or electroejaculator to be compared in terms of motility performance. In experiment 3, 104 ejaculates collected by AV from 26 males were analysed via the CASA system to characterize their motility patterns. In experiment 4, ejaculates from pairs of rams (20 rams in total) were simultaneously assessed for mucus migration (ovine, caprine, bovine) and motility patterns to evaluate the correlations between both parameters. Semen collected by AV and extended in SAM allows the most reliable assessment for sperm motility. Ram spermatozoa move fast and follow a linear trajectory compared with other ruminants. Continuous line velocity (VCL) and average path velocity (VAP) are the only sperm kinematic parameters that presented significant positive correlations with the ability to migrate in sheep cervical mucus (p < 0.05). Continuous line velocity, VAP, straight line velocity and linearity are highly significantly related with migration efficiency in goat cervical mucus (p < 0.01) and only lateral head displacement is negatively related to sperm migration in bovine cervical mucus (p < 0.05). These results suggest that specific kinematic parameters confer the ability of spermatozoa to colonize and migrate through epithelial mucus with different rheological properties.

Assessment of in vitro sperm characteristics in relation to fertility in dairy bulls

The performance of frozen-thawed spermatozoa from 10 Holstein bulls in a range of in vitro diagnostic tests and the relationship with adjusted in vivo fertility data was determined. The tests included an assessment of motility (subjective and computer-assisted), morphology, concentration, viability, acrosomal and chromatin integrity conducted immediately post-thaw and after swim-up, in conjunction with membrane status (CTC staining) and migration in an artificial cervical mucus. Adjusted in vivo fertility correlated with subjectively assessed post-thaw motility (r=0.672, p=0.033), post-thaw straight-line velocity (r=0.636, p=0.048), post-thaw sperm morphology (r=-0.762, p=0.010), post-thaw sperm viability (r=0.635, p=0.048), the concentration of spermatozoa after swim-up (r=0.649, p=0.042), sperm morphology after swim-up (r=-0.687, p=0.028), the number of spermatozoa migrating 10mm into artificial cervical mucus (r=0.632, p=0.050) and the distance migrated by the vanguard spermatozoon in artificial mucus (r=0.701, p=0.024). A stepwise regression analysis identified tests which, when combined, produced models with a strong correlation (R(2)>0.9) to fertility.

Development of a novel home sperm test

BACKGROUND

The majority of men find the production of a semen sample an embarrassing and stressful experience. Consequently, the availability of an over-the-counter home sperm test, which would reliably and accurately allow the patient to obtain an assessment of fertility potential at their convenience, would be a major benefit. Our objective was to develop and evaluate a home sperm test that provides a visual estimate of the concentration of progressively motile sperm in a semen sample.

METHODS

Three particular challenges are described (i) developing a visualization system; (ii) optimization of the detection limit; and (iii) controlling variation due to changes in ambient temperature. The accuracy of the device was tested against two reference methods: computer-assisted sperm analysis (CASA) and a hyaluronate migration test (HMT).

RESULTS

In 129 semen samples, where both reference methods agreed (positive or negative), the accuracy of the device was 95%. The observed likelihood ratio of 8.8 indicated that a sample showing a red line in the device was over eight times more likely to have a positive (normal) result in CASA and HMT than a sample without a red line.

CONCLUSIONS

The final device provides a visual estimate of the concentration of progressively motile sperm in a semen sample using a test that is completed within approximately 1 h of production of the sample and can be used by the man in the comfort of his own home.

Ultrastructural and Rheological Properties of Bovine Vaginal Fluid and its Relation to Sperm Motility and Fertilization: a Review

The tubular genital organs of the mammalian female reproductive tract provide different luminal microenvironments that can act as an aid or a barrier to gamete transport and the first steps of embryonic development. The mechanism of sperm transport through the genital tract has not been fully established but, first of all, sperm cells encounter and need to overcome mucous-like secretions to reach the site where fertilization occurs. One of these secretions, vaginal fluid, is a complex biological product, which is mainly derived from cervical mucus. In this review, we focus on recent studies that describe the relationships between the ultrastructural and rheological properties of bovine vaginal fluid and sperm motion. In the light of this, we propose bovine vaginal fluid as a morphofunctional model for the study of sperm transport in mammals.

Liquid storage of flow cytometrically sorted ram spermatozoa

This study investigated the optimum short-term storage conditions for ram spermatozoa before and after flow cytometric sorting. Prior to sorting, semen from four rams (n = 3 ejaculates per ram) was diluted in either a Tris-based diluent (TRIS) or AndroHep (AH) and stored at 5, 15 or 21 degrees C for 0, 6 or 24h. Sperm characteristics were assessed during storage and after sorting, freeze-thawing and incubation (6h, 37 degrees C). Functional capacity and migration ability in artificial cervical mucus (sperm migration test (SMT)) of stored, sorted and non-sorted (control) spermatozoa were assessed after freeze-thawing. After sorting, semen from three rams (n = 3 ejaculates per ram) was diluted in four different extenders: ultra-heat-treated (UHT) long life milk, TRIS containing 10% (v/v) egg yolk (TRIS-EY), AH (pH 7.4), or TEST buffer containing 10% (v/v) egg yolk (TYB). Sorted and non-sorted (control) spermatozoa were stored at 15 degrees C for 24h or 5 degrees C for 6 days. Sperm characteristics were evaluated at 0, 6 and 24h for samples stored at 15 degrees C and daily for samples stored at 5 degrees C. The SMT was performed on sorted and non-sorted (control) spermatozoa after 6h and 3 days storage at 15 and 5 degrees C, respectively. Spermatozoa stored in TRIS were sorted more efficiently, had higher motility after sorting, freezing, thawing and incubation and had greater numbers of spermatozoa penetrating into the SMT than spermatozoa stored in AH prior to sorting. Spermatozoa stored in UHT at both temperatures had higher motility, acrosome integrity and traveled greater distances in the SMT than spermatozoa stored in all other diluents. In summary, storage in TRIS at 21 degrees C was optimal for transport of ram spermatozoa to the sorting site, and storage of spermatozoa in UHT diluent (after sorting) preserved sperm viability and migration ability best at both 15 and 5 degrees C.

Migration of bovine spermatozoa in a synthetic medium and its relation to in vivo bull fertility

Although sperm migration has been extensively refined and validated in human infertility studies, its application to predict bovine fertility has been very limited, and a clear relation between the sperm migration distance and in vivo bull fertility has never been demonstrated. A synthetic medium based upon methyl cellulose (MC) was tested for its suitability to serve as a migration medium for frozen-thawed bovine spermatozoa. The effects of the concentration of MC, the incubation time, and sperm concentration on sperm migration capacity was determined. The relation between sperm migration capacity at different incubation times of the frozen-thawed spermatozoa of five bulls, and their 56 days nonreturn rates (NRRs) was assessed in order to evaluate its suitability as a tool to predict in vivo bull fertility. The highest repeatability of the sperm migration test (CV = 10.7%) was obtained when the sperm migration distance of the five vanguard motile spermatozoa was determined at 30 min incubation at 37 degrees C in a migration medium with 1.35% MC. No significant difference in migration distance was demonstrated when sperm concentrations of 100 x 10(6) and 150 x 10(6) spermatozoa/ml, respectively, were used. Despite the relatively high repeatability of the migration test, no relation was found between the sperm migration distance and the 56 days NRRs of five sire bulls. Therefore, the sperm migration test in 1.35% MC cannot be used to predict in vivo bull fertility accurately.

Synthetic cervical mucus formulation

A synthetic formulation has been developed with viscosity, spinnbarkeit, and pH comparable to that reported for human cervical mucus. The formulation contains guar gum crosslinked with borate ion, mucin (dried porcine gastric), and a mixed preservative system in pH 7.4, 0.1M phosphate buffer. The guar gum source, mucin concentration, and method of preparation were shown to be critical factors in the performance of the formulation.