Cervical mucins affect the motility of human spermatozoa in vitro

Sialylation: fate decision of mammalian sperm development, fertilization, and male fertility†

Sperm development, maturation, and successful fertilization within the female reproductive tract are intricate and orderly processes that involve protein translation and post-translational modifications. Among these modifications, sialylation plays a crucial role. Any disruptions occurring throughout the sperm's life cycle can result in male infertility, yet our current understanding of this process remains limited. Conventional semen analysis often fails to diagnose some infertility cases associated with sperm sialylation, emphasizing the need to comprehend and investigate the characteristics of sperm sialylation. This review reanalyzes the significance of sialylation in sperm development and fertilization and evaluates the impact of sialylation damage on male fertility under pathological conditions. Sialylation serves a vital role in the life journey of sperm, providing a negatively charged glycocalyx and enriching the molecular structure of the sperm surface, which is beneficial to sperm reversible recognition and immune interaction. These characteristics are particularly crucial during sperm maturation and fertilization within the female reproductive tract. Moreover, enhancing the understanding of the mechanism underlying sperm sialylation can promote the development of relevant clinical indicators for infertility detection and treatment.

An Exploratory Data Analysis from Ovine and Bovine RNA-Seq Identifies Pathways and Key Genes Related to Cervical Dilatation

The present study developed a review and exploration of data in public and already validated repositories. The main objective was to identify the pathways involved in ruminants' cervical dilatation, which are conserved between cattle and sheep in the follicular and luteal phases of the reproductive cycle. In cattle, 1961 genes were more differentially expressed in the follicular phase and 1560 in the luteal phase. An amount of 24 genes were considered exclusively expressed from these. A total of 18 genes were in the follicular phase and 6 genes were in the luteal phase. In sheep, 2126 genes were more differentially expressed in the follicular phase and 2469 genes were more differentially expressed in the luteal phase. Hoxb genes were identified in both species and are correlated with the PI3K/Akt pathway. PI3K/Akt was also found in both cattle and sheep, appearing prominently in the follicular and luteal phases of both species. Our analyses have pointed out that the PI3K/Akt pathway and the Hoxb genes appear in prominence in modulating mechanisms that involve estrus alterations in the cervix. PI3K/Akt appears to be an important pathway in the cervical relaxation process.

Siglec expression on the surface of human, bull and ram sperm

Sialic acid (Sia) is a major constituent of both the sperm glycocalyx and female reproductive mucosal surface and is involved in regulating sperm migration, uterotubal reservoir formation and oocyte binding. Siglecs (sialic acid-binding immunoglobulin - like lectins) commonly found on immune cells, bind to Sia in a linkage- and sugar-specific manner and often mediate cell-to-cell interactions and signalling. Proteomic and transcriptomic analysis of human and bovine sperm have listed Siglecs, but to date, their presence and/or localisation on sperm has not been studied. Therefore, the aim of this study was to characterise the presence of Siglecs on the surface of bovine, human and ovine sperm using both immunostaining and Western blotting. Siglec 1, 2, 5, 6, 10 and 14 were identified and displayed both species- and regional-specific expression on sperm. Almost universal expression across Siglecs and species was evident in the sperm neck and midpiece region while variable expression among Siglecs, similar among species, was detected in the head and tail regions of the sperm. The possible role for these proteins on sperm is discussed.

Seminal plasma and cryopreservation alter ram sperm surface carbohydrates and interactions with neutrophils

Spermatozoa deposited vaginally must navigate the physical, chemical and immune barriers of the cervix to reach the site of fertilisation. Characteristics that favour successful cervical transit remain largely unknown beyond the obvious factors of motility and viability. Epididymal and cryopreserved ram spermatozoa demonstrate poor cervical transit, for unknown reasons. We hypothesised that seminal plasma exposure and cryopreservation alter the surface sugars of these sperm populations and, consequently, their interaction with immune cells, both potential factors for successful cervical transit. The carbohydrate profiles of epididymal, ejaculated and frozen–thawed ram spermatozoa were assessed by flow cytometry and western blotting using lectins for galactose, sialic acid, N-acetylglucosamine and mannose. Seminal plasma exposure and cryopreservation caused significant changes to the relative amounts of surface sugars detected by flow cytometry and lectin blotting. Immune cell interaction was characterised using a neutrophil-binding assay. Seminal plasma acted as a robust protective mechanism, limiting binding of spermatozoa, whereas the media used for cryopreservation caused a significant disruption to opsonin-mediated binding. We were unable to demonstrate a link between changes to surface sugars and neutrophil susceptibility. Seminal plasma and cryopreservation clearly alter the sperm glycocalyx, as well as the interaction of spermatozoa with immune cells.

The whole genome sequence of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), reveals insights into the biology and adaptive evolution of a highly invasive pest species

Background

The Mediterranean fruit fly (medfly), Ceratitis capitata, is a major destructive insect pest due to its broad host range, which includes hundreds of fruits and vegetables. It exhibits a unique ability to invade and adapt to ecological niches throughout tropical and subtropical regions of the world, though medfly infestations have been prevented and controlled by the sterile insect technique (SIT) as part of integrated pest management programs (IPMs). The genetic analysis and manipulation of medfly has been subject to intensive study in an effort to improve SIT efficacy and other aspects of IPM control.

Results

The 479 Mb medfly genome is sequenced from adult flies from lines inbred for 20 generations. A high-quality assembly is achieved having a contig N50 of 45.7 kb and scaffold N50 of 4.06 Mb. In-depth curation of more than 1800 messenger RNAs shows specific gene expansions that can be related to invasiveness and host adaptation, including gene families for chemoreception, toxin and insecticide metabolism, cuticle proteins, opsins, and aquaporins. We identify genes relevant to IPM control, including those required to improve SIT.

Conclusions

The medfly genome sequence provides critical insights into the biology of one of the most serious and widespread agricultural pests. This knowledge should significantly advance the means of controlling the size and invasive potential of medfly populations. Its close relationship to Drosophila, and other insect species important to agriculture and human health, will further comparative functional and structural studies of insect genomes that should broaden our understanding of gene family evolution.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-016-1049-2) contains supplementary material, which is available to authorized users.

Molecular aspects of mucin biosynthesis and mucus formation in the bovine cervix during the periestrous period

Mucus within the cervical canal represents a hormonally regulated barrier that reconciles the need to exclude the vaginal microflora from the uterus during progesterone dominance, while permitting sperm transport at estrus. Its characteristics change during the estrous cycle to facilitate these competing functional requirements. Hydrated mucin glycoproteins synthesized by the endocervical epithelium form the molecular scaffold of this mucus. This study uses the bovine cervix as a model to examine functional groups of genes related to mucin biosynthesis and mucus production over the periestrous period when functional changes in cervical barrier function are most prominent. Cervical tissue samples were collected from 30 estrus synchronized beef heifers. Animals were slaughtered in groups starting 12 h after the withdrawal of intravaginal progesterone releasing devices (controlled internal drug releases) until 7 days postonset of estrus (luteal phase). Subsequent groupings represented proestrus, early estrus, late estrus, metestrus, and finally the early luteal phase. Tissues were submitted to next generation RNA-seq transcriptome analysis. We identified 114 genes associated with biosynthesis and intracellular transport of mucins, and postsecretory modifications of cervical; 53 of these genes showed at least a twofold change in one or more experimental group in relation to onset of estrus, and the differences between groups were significant ( P < 0.05). The majority of these genes showed the greatest alteration in their expression in the 48 h postestrus and luteal phase groups.

Characteristics of the menstrual cycle after discontinuation of oral contraceptives

BACKGROUND

Menstrual cycle function may continue to be altered after discontinuation of oral contraceptives (OC). Few studies have been published on the effects of recent OC use on menstrual cycle parameters; none have examined characteristics of the menstrual flow or the quality of cervical mucus. The purpose of this retrospective matched cohort study is to assess biomarkers of the menstrual cycle after discontinuation of OCs.

METHODS

Among a sample of women who daily recorded observations of menstrual cycle biomarkers, 70 women who had recently discontinued OCs were randomly matched by age and parity with 70 women who had not used OCs for at least 1 year. Outcomes investigated included overall cycle length, length of the luteal phase, estimated day of ovulation, duration of menstrual flow, menstrual intensity, and mucus score. Differences between recent OC users and controls were assessed using random effects modeling.

RESULTS

Recent OC users had statistically significantly lower scores for mucus quality for cycles 1 and 2. Additionally, OC users had a later estimated day of ovulation that was statistically significant in cycle 2 and a decreased intensity of menstrual flow that was significant in the first four cycles (difference = -0.48 days). In random effects modeling, all these parameters were significantly different for the first six cycles combined.

CONCLUSIONS

Menstrual cycle biomarkers are altered for at least two cycles after discontinuation of OCs, and this may help explain the temporary decrease in fecundity associated with recent OC use.

Biofluid mechanics of the human reproductive process: modelling of the complex interaction and pathway to the oocytes

Recent revelations in the human reproductive process have fuelled much interest in this field of study. In particular, the once prevailing view of large numbers of ejaculated sperms racing towards the egg has been refuted recently. This is opposed to the current views derived from numerous clinical findings that state that only a very small number of sperms will ever enter the oviduct. It is believed that these few sperms must have been guided to make the long, tedious and obstructed journey to the egg. For a mature spermatozoon, its hyperactivated swimming motility upon capacitation plays an important role in the fertilization of a mature egg. Likewise, the female genital tract also provides guiding mechanisms to complement the survival of normal hydrodynamic profile sperms and thus promotes an eventual sperm–egg interaction. Understanding these mechanisms can be essential for the derivation of assisted conception techniques especially those in vitro. With the aid of computational models and simulation, suitability and effectiveness of novel assisted conception methodology can be assessed, particularly for those yet to be ready for clinical trials. This review discusses the possible bioengineering models and the mechanisms by which human spermatozoa are guided to the egg.

The inhibition of the Human Immunodeficiency Virus type 1 activity by crude and purified human pregnancy plug mucus and mucins in an inhibition assay

Background

The female reproductive tract is amongst the main routes for Human Immunodeficiency Virus (HIV) transmission. Cervical mucus however is known to protect the female reproductive tract from bacterial invasion and fluid loss and regulates and facilitates sperm transport to the upper reproductive tract. The purpose of this study was to purify and characterize pregnancy plug mucins and determine their anti-HIV-1 activity in an HIV inhibition assay.

Methods

Pregnancy plug mucins were purified by caesium chloride density-gradient ultra-centrifugation and characterized by Western blotting analysis. The anti-HIV-1 activities of the crude pregnancy plug mucus and purified pregnancy plug mucins was determined by incubating them with HIV-1 prior to infection of the human T lymphoblastoid cell line (CEM SS cells).

Results

The pregnancy plug mucus had MUC1, MUC2, MUC5AC and MUC5B. The HIV inhibition assay revealed that while the purified pregnancy plug mucins inhibit HIV-1 activity by approximately 97.5%, the crude pregnancy plug mucus failed to inhibit HIV-1 activity.

Conclusion

Although it is not clear why the crude sample did not inhibit HIV-1 activity, it may be that the amount of mucins in the crude pregnancy plug mucus (which contains water, mucins, lipids, nucleic acids, lactoferrin, lysozyme, immunoglobulins and ions), is insufficient to cause viral inhibition or aggregation.

MUC1 in human testis and ejaculated spermatozoa and its relationship to male fertility status

MUC1 is a cell surface glycoprotein with a previously described antiadhesive role involved in different aspects of reproductive function. We found MUC1 expressed in male germ cell line and within the ejaculated sperm, but its presence in mature sperm does not seem to be related to male fertility. This was confirmed after analysis of results from assisted reproduction techniques with oocyte donation related with MUC1, although higher MUC1 expression is related to sperm recovery after preparation.

Mucin gene expression in human male urogenital tract epithelia

BACKGROUND

Mucins are large, hydrophilic glycoproteins that protect wet-surfaced epithelia from pathogen invasion as well as provide lubrication. At least 17 mucin genes have been cloned to date. This study sought to determine the mucin gene expression profile of the human male urogenital tract epithelia, to determine if mucins are present in seminal fluid and to assess the effect of androgens on mucin expression.

METHODS AND RESULTS

Testis, epididymis, vas deferens, seminal vesicle, prostate, bladder, urethra and foreskin were assessed for mucin expression by RT-PCR (for 14 mucin genes) and immunohistochemistry (nine antibodies for five mucins). Epithelia of the vas deferens, prostate and urethra expressed the greatest number of mucins, each with mRNA for between 5 and 8 mucins. Except for MUC20 in epididymis, mRNA for MUC1 and MUC20, both membrane-associated mucins, was detected in all tissues analysed. By comparison, MUC6 was more restricted in expression, being primarily detected in seminal vesicle. MUC1, MUC5B and MUC6 were detected in seminal fluid samples by immunoblot analysis. Androgens had no effect on mucin expression in cultured human prostatic epithelial cells.

CONCLUSIONS

Each region of urogenital tract epithelium expressed a unique mucin gene repertoire. Secretory mucins are present in seminal fluid, and androgens do not appear to regulate mucin gene expression in prostatic epithelial cells in culture.

Ultrastructure of the human periovulatory cervical mucus

Two main types of cervical mucus have been described during the menstrual cycle: oestrogenic and progestative. Each category shows diverse morphological and functional features from the reproductive point of view. Traditionally, this change has been approached by analysing morphological patterns. In fact, a mesh model has been described for cervical mucus, structurally composed of fibrillar subunits with a parallel orientation, together with another model in a characteristic network shape with canalicular units, but the real model is not clear. The objective of our work was to study the different morphological structures of the mucus, as related to the day of follicular rupture (considered as day 0) determined by ultrasound. Cervical mucus samples were obtained from the cervical canal with an ASPIRETTEtrade mark from day -4 to day +1 of the menstrual cycle. Samples were fixed and dried by critical point. The ultrastructure was examined with scanning electron microscopy. The presence of three types of oestrogenic and one type of progestative cervical mucus was confirmed in this period. Our paper shows different types of ultrastructure in the oestrogenic mucus in relation to ovulation, which would help to understand the interaction between male gametes and cervical mucus in migration through the female genital tract.

Reduced Fertilization Rates in Older Men When Cervical Mucus Is Suboptimal

OBJECTIVE

Cervical mucus is vital in the regulation of sperm survival and transport through the reproductive tract. The goal of this study is to assess whether the lowered fertility for men in their late 30s and early 40s is related to the nature of cervical mucus on the day of intercourse.

METHODS

In a prospective study of 7 European family planning centers, 782 couples not using birth control recorded daily observations of intercourse and the nature of cervical mucus. Using data from 1,459 menstrual cycles, 342 ending in pregnancy, we estimate day-specific conception probabilities in relation to mucus and male and female age.

RESULTS

On days where cervical mucus was not evident, intercourse for men in their late 30s and early 40s was 50% less likely to result in a clinical pregnancy, adjusting for intercourse timing and female age. As secretions become more conducive to sperm transport, the effect of male age diminishes steadily from 21% on days with damp secretions, to 11% on days with thick mucus, to only 4% on days with most fertile-type mucus.

CONCLUSION

The effect of male age on fecundability can be minimized by timing intercourse on days with optimal secretions.

LEVEL OF EVIDENCE

II-2.

The expression of free oligosaccharides in human seminal plasma

Human seminal plasma is a complex mixture of proteins, glycoproteins, peptides, glycopeptides, and prostaglandins secreted by organs of the male reproductive tract. The components of this fluid have been implicated in the suppression of immune response, agonistic effects on sperm-egg binding, and promotion of successful implantation of the human embryo. Fractionation followed by biophysical analyses revealed that free oligosaccharides constitute a major component of the total glycoconjugates within seminal plasma. Significant findings of our analyses include the following: (i) the concentration of free oligosaccharides is 0.3-0.4 mg/ml; (ii) mono- and difucosylated forms of the disaccharide lactose are major components; (iii) many of the remaining oligosaccharides are also rich in fucose and carry Lewis(x) and/or Lewis(y) epitopes; (iv) a subset of the oligosaccharides express the reducing end sequence (GlcNAcbeta1-3/4Glc) not reported in human milk oligosaccharides; (v) oligosaccharides in seminal plasma exclusively express type 2 (Galbeta1-4GlcNAc) but not the type 1 sequences (Galbeta1-3GlcNAc) that predominate in human milk glycans; and (vi) the structural diversity of seminal plasma oligosaccharides is far less than human milk oligosaccharides. The agonistic effect of both fucose and fucosylated glycoconjugates on human sperm-egg binding in vitro suggests that fucosylated oligosaccharides may also promote fertilization in the female reproductive tract.