Molecules involved in sperm-oviduct adhesion and release

Factors affecting the success of laparoscopic artificial insemination in sheep

Successful artificial breeding underpins rapid genetic and production gains in animal agriculture. In sheep, artificial insemination with frozen semen is performed via intrauterine laparoscopy as frozen-thawed spermatozoa do not traverse the cervix in sufficient numbers for high fertility and transcervical insemination is anatomically impossible in most ewes. Historically, laparoscopic artificial insemination has always been considered reasonably successful, but recent anecdotal reports of poor fertility place it at risk of warning adoption. Understanding the male, female and environmental factors that influence the fertility of sheep is warranted if the success of artificial insemination is to be improved and genetic progress maximised for the sheep industry. This review details the current practice of laparoscopic AI in sheep. It explores the effects of semen quantity and quality, the ewe, her preparation, and environmental conditions, on the fertility obtained following laparoscopic artificial insemination.

A systematic review on the prospects of X- and Y-sexed semen in ruminant livestock: implications for conservation, a South African perspective

South Africa is home to numerous indigenous and locally developed sheep (Nguni Pedi, Zulu, and Namaqua Afrikaner, Afrino, Africander, Bezuidenhout Africander, Damara, Dorper, Döhne Merino, Meat Master, South African Merino, South African Mutton Merino, Van Rooy, and Dorper), goat (SA veld, Tankwa, Imbuzi, Bantu, Boer, and Savanna) and cattle (Afrigus, Afrikaner, Bolowana, Bonsmara, Bovelder, Drakensberger, South African Angus, South African Dairy Swiss, South African Friesland, South African Red, and Veld Master) animals. These breeds require less veterinary service, feed, management efforts, provide income to rural and or poor owners. However, most of them are under extinction risks and some with unknown status hence, require immediate conservation intervention. To allow faster genetic progress on the endangered animals, it is important to generate productive animals while reducing wastages and this can be achieved through sex-sorted semen. Therefore, this systematic review is aimed to evaluate the prospects of X and Y-sexed semen in ruminant livestock and some solutions that can be used to address poor sex-sorted semen and its fertility. This review was incorporated through gathering and assessing relevant articles and through the data from the DAD-IS database. The keywords that were used to search articles online were pre-gender selection, indigenous ecotypes, fertility, flow cytometry, artificial insemination, conservation, and improving sexed semen. Following a careful review of all articles, PRISMA guidelines were used to find the articles that are suitable to address the aim of this review. Sex-sorted semen is a recently introduced technology gaining more attention from researchers particularly, in the conservation programs. Preselection of semen based on the sex chromosomes (X- and or Y-bearing chromosomes) is of paramount importance to obtain desired sex of the offspring and avoid animal wastage as much as possible. However, diverse factors can affect quality of semen of different animal species especially after sex-sorting. Flow cytometry is a common method used to select male and female sperm cells and discard dead and abnormal sperm cells during the process. Thus, sperm sexing is a good advanced reproductive technology (ART) however, it is associated with the production of oxidative stress (OS) and DNA fragmentation (SDF). These findings, therefore, necessitates more innovation studies to come up with a sexing technology that will protect sperm cell injuries during sorting in frozen-thawed.

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.

Arresting calcium-regulated sperm metabolic dynamics enables prolonged fertility in poultry liquid semen storage

The preservation of liquid semen is pivotal for both industrial livestock production and genetic management/conservation of species with sperm that are not highly cryo-tolerant. Nevertheless, with regard to poultry semen, even brief in vitro storage periods can lead to a notable decline in fertility, despite the in vivo capacity to maintain fertility for several weeks when within the hen's sperm storage tubules. For fertility in sperm, intracellular calcium ions ([Ca2+]i) play a key role in signaling towards modifying energy metabolism. While reducing [Ca2+]i has been found to enhance the preservation of sperm fertility in some mammals, the connection between semen fertility and calcium availability in avian sperm has received limited attention. In this study, we demonstrate that the use of extracellular and intracellular calcium chelators in liquid semen extenders, specifically EGTA and EGTA-AM, has distinct effects on prolonging the fertility of chicken sperm. These results were validated through in vivo fertility tests. Mechanistically, the effects observed were linked to coordination of mitochondrial metabolism and ATP catabolism. Despite both calcium chelators inducing hypoxia, they differentially regulated mitochondrial respiration and ATP accumulation. This regulation was closely linked to a bimodal control of dynein ATPase activity; a direct initial activation with reduction in [Ca2+]i, and subsequent suppression by cytoplasmic acidification caused by lactic acid. These findings not only contribute to advancing poultry liquid semen preservation techniques, but also elucidates biologically relevant mechanisms that may underlie storage within the female reproductive tract in birds.

Candidate genes and proteins regulating bull semen quality: a review

Poor semen profile reflected by suboptimum fertility statistics is a concern in bulls reared for breeding purpose. A critical review of research on candidate genes and proteins associated with semen quality traits will be useful to understand the progress of molecular marker development for bull semen quality traits. Here, we have tabulated and classified candidate genes and proteins associated with bull semen quality based on a literature survey. A total of 175 candidate genes are associated with semen quality traits in various breeds of cattle. Several studies using candidate gene approach have identified 26 genes carrying a total of 44 single nucleotide polymorphisms. Furthermore, nine genome-wide association studies (GWASes) have identified 150 candidate genes using bovine single nucleotide polymorphisms (SNP) chips. Three genes, namely membrane-associated ring-CH-type finger 1 (MARCH1), platelet-derived growth factor receptor beta, and phosphodiesterase type 1, were identified commonly in two GWASes, which, especially MARCH1, are required to explore their regulatory roles in bull semen quality in in-depth studies. With the advancement of high-throughput-omic technologies, more candidate genes associated with bull semen quality may be identified in the future. Therefore, the functional significance of candidate genes and proteins need to be delved further into future investigations to augment bull semen quality.

Molecules involved in the sperm interaction in the human uterine tube: a histochemical and immunohistochemical approach

In humans, even where millions of spermatozoa are deposited upon ejaculation in the vagina, only a few thousand enter the uterine tube (UT). Sperm transiently adhere to the epithelial cells lining the isthmus reservoir, and this interaction is essential in coordinating the availability of functional spermatozoa for fertilization. The binding of spermatozoa to the UT epithelium (mucosa) occurs due to interactions between cell-adhesion molecules on the cell surfaces of both the sperm and the epithelial cell. However, in humans, there is little information about the molecules involved. The aim of this study was to perform a histological characterization of the UT focused on determining the tissue distribution and deposition of some molecules associated with cell adhesion (F-spondin, galectin-9, osteopontin, integrin αV/β3) and UT's contractile activity (TNFα-R1, TNFα-R2) in the follicular and luteal phases. Our results showed the presence of galectin-9, F-spondin, osteopontin, integrin αV/β3, TNFα-R1, and TNFα-R2 in the epithelial cells in ampullar and isthmic segments during the menstrual cycle. Our results suggest that these molecules could form part of the sperm-UT interactions. Future studies will shed light on the specific role of each of the identified molecules.

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

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

Escaping Behavior of Sperms on the Biomimetic Oviductal Surface

Before fertilization, sperms adhere to oviductal epithelium cells, and only a restrictive number of winner sperms can escape to reach the egg. To study the sperm escape behavior from the oviductal surface, we developed a microfluidic chip to fabricate an adhesive surface and to create a gradient of progesterone (P₄) for mimicking the oviduct microenvironment in vivo. We identified three sperm motion patterns in such a microenvironment─anchored spin, run-and-spin, and escaped mode. By using kinetic analysis, we verified the hypothesis that the responsive rotation energy anchored with the adhered sperm head determines whether the sperm is trapped or detaching, which is defined as the hammer flying strategy of successful escape after accumulating energy in the process of rotating. Intriguingly, this hammer-throw escaping is able to be triggered by the P₄ biochemical stimulation. Our results revealed the tangled process of sperm escape before fertilization in the ingenious microfluidic system.

NR3C1 and glucocorticoid-regulatory genes mRNA and protein expression in the endometrium and ampulla during the bovine estrous cycle

The bovine reproductive tract exhibits changes during the estrous cycle modulated by the interplay of steroid hormones. Glucocorticoids can be detrimental when stress-induced but are relevant at baseline levels for appropriate reproductive function. Here, an analysis of quantitative real-time PCR was performed to study the bovine glucocorticoid-related baseline gene transcription in endometrial and ampullar tissue samples derived from three time points of the estrous cycle, stage I (Days 1-4), stage III (Days 11-17) and stage IV (Days 18-20). Our results revealed expression differences during stages, as expression observed in the ampulla was higher during the post-ovulatory phase (stage I), including the glucocorticoid receptor NR3C1, and some of its regulators, involved in glucocorticoid availability (HSD11B1 and HSD11B2) and transcriptional actions (FKBP4 and FKBP5). In contrast, in the endometrium, higher expression of the steroid receptors was observed during the late luteal phase (stage III), including ESR1, ESR2, PGRMC1 and PGRMC2, and HSD11B1 expression decreased, while HSD11B2 increased. Moreover, at protein level, FKBP4 was higher expressed during the late luteal phase, and NR3C1 during the pre-ovulatory phase (stage IV). These results suggest that tight regulation of the glucocorticoid activity is promoted in the ampulla, when reproductive events are taking place, including oocyte maturation. Moreover, most expression changes in the endometrium were observed during the late luteal phase, and may be related to the embryonic maternal recognition. In conclusion, the glucocorticoid regulation changes across the estrous cycle and may be playing a role on the reproductive events occurring in the bovine ampulla and endometrium.

Evaluation of sperm integrin α5β1 as a potential marker of fertility in humans

Sperm selection for assisted reproduction techniques is generally based on basic parameters, while key aspects of sperm competence and its journey from the deposition site to the fertilization site are overlooked. Consequently, identifying molecular markers in spermatozoa that can efficiently predict the fertility of a semen sample could be of great interest, particularly in cases of idiopathic male infertility. When spermatozoa reach the female reproductive tract, it provides to them the cellular and molecular microenvironment needed to acquire fertilizing ability. In this sense, considering the role that integrin α5β1 of spermatozoa plays in reproduction-related events, we investigated the correlation between the subcellular localization of sperm integrin α5β1 and early embryo development outcome after in vitro fertilization (IVF) procedures in human. Twenty-four semen samples from normozoospermic men and metaphase II (MII) oocytes from healthy women aged under 38 years, from couples who underwent IVF cycles, were used in this work. Sperm α5β1 localization was evaluated by immunofluorescence assay using an antibody against integrin α5 subunit. Integrin α5β1 was mainly localized in the sperm acrosomal region (45.33±7.89%) or the equatorial segment (30.12±7.43%). The early embryo development rate (data obtained from the Fertility Center) correlated positively with the localization of α5β1 in the acrosomal region (number of usable embryos / inseminated oocytes: ρ = 0.75; p<0.01 and number of usable embryos/total number of two pronuclear zygotes: ρ = 0.80; p<0.01). However, this correlation was not significant when the equatorial segment mark was evaluated. In addition, human sperm released from co-culture with bovine oviductal epithelial cells (BOEC) showed a significant enrichment in the acrosomal localization pattern of α5β1 compared to those sperm that were not co-cultured with BOEC (85.20±5.35% vs 35.00±17.09%, respectively, p<0.05). In conclusion, the evaluation of sperm integrin α5β1 immunolocalization could be a useful tool to select sperm with fertilizing ability from human semen samples before IVF procedures.

Putative Degradation of Non-Stored Sperm in the Female Reproductive Tract of the Dengue Vector Mosquito Aedes aegypti

In insect vectors of disease, male and female molecules that mediate reproductive processes are promising targets to suppress fertility of these populations. One process, the storage of sperm in the female reproductive tract, is essential for optimal fertility in all organisms examined to date. In the dengue vector mosquito Aedes aegypti, female sperm storage has not been fully characterized, a requirement to identify sex-specific molecules that mediate this process. Aedes aegypti males deposit the ejaculate into the bursa of the female reproductive tract, and sperm enter the spermathecae—the long-term storage sites—quickly after insemination. However, the proportion of sperm received during mating that are stored in the spermathecae is unclear, and the fate of non-stored sperm unknown. We quantified sperm storage in two Ae. aegypti strains, mated in all combinations, and in two contexts (mass mated and when mating was observed) at 1-, 3- and 5-days post-mating. Sperm quantity in the spermathecae was similar at all timepoints; most females stored ~400 sperm on average. Sperm that did not enter the spermathecae remained in the bursa, where they declined in number and became more fragile to mechanical manipulation at each timepoint. Further, sperm viability in the bursa fell from 91.6% shortly after mating to 12.2% 24 h later. One day after insemination, ~50% of sperm detected in the female reproductive tract was stored in the spermathecae. When we quantified sperm storage in females mated to males that transferred reduced ejaculate quantities (but still able to induce optimal fertility in their mates), sperm detected in the spermathecae similarly declined; females stored ~50% of the sperm received even as sperm quantities transferred at mating declined. Our results suggest that sperm storage in Ae. aegypti females is influenced by ejaculate volume, and that sperm that do not enter the spermathecae remain in the bursa, where they appear to degrade. The consistent presence of sperm in the bursa, even when males transferred low sperm quantities, suggests that the putative degradation of bursa sperm may play a role in Ae. aegypti female fertility, potentially identifying a novel process in this important vector species.

High throughput deep proteomic analysis of seminal plasma from stallions with contrasting semen quality

Seminal plasma proteins and pathways associated with sperm motility have not been elucidated in stallions. Therefore, in the current study, using the high throughput LC/MS-MS approach, we profiled stallion seminal plasma proteins and identified the proteins and pathways associated with sperm motility. Seminal plasma from six stallions producing semen with contrasting sperm motility (n = 3 each high-and low-motile group) was utilized for proteomic analysis. We identified a total of 1687 proteins in stallion seminal plasma, of which 1627 and 1496 proteins were expressed in high- (HM) and low- motile (LM) sperm of stallions, respectively. A total number of 1436 proteins were co-expressed in both the groups; 191 (11%) and 60 (3.5%) proteins were exclusively detected in HM and LM groups, respectively. A total of 220 proteins were upregulated (>1-fold change) and 386 proteins were downregulated in SP from LM group stallions as compared to HM group stallions, while 830 proteins were neutrally expressed in both the groups. Gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed dysregulation of the important proteins related to mitochondrial function, acrosome, and sperm cytoskeleton in the seminal plasma of stallions producing ejaculates with low sperm motility. High abundance of peroxiredoxins and low abundance of seminal Chaperonin Containing TCP1 Complex (CCT) complex and Annexins indicate dysregulated oxidative metabolism, which might be the underlying etiology for poor sperm motility in LM group stallions. In conclusion, the current study identified the seminal plasma proteomic alterations associated with poor sperm motility in stallions; the results indicate that poor sperm motility in stallions could be associated with altered expression of seminal plasma proteins involved in oxidative metabolism.

Hyperactivation is sufficient to release porcine sperm from immobilized oviduct glycans

Fertilizing sperm are retained by adhesion to specific glycans on the epithelium of the oviduct forming a reservoir before sperm are released from the reservoir so fertilization can ensue. Capacitated sperm lose affinity for the oviduct epithelium but the components of capacitation that are important for sperm release are uncertain. One important correlate of capacitation is the development of hyperactivated motility. Hyperactivation is characterized by asymmetrical flagellar beating with high beat amplitude. We tested whether the development of full-type asymmetrical motility was sufficient to release sperm from immobilized oviduct glycans. Sperm hyperactivation was induced by four different compounds, a cell-permeable cAMP analog (cBiMPS), CatSper activators (4-aminopyridine and procaine), and an endogenous steroid (progesterone). Using standard analysis (CASA) and direct visualization with high-speed video microscopy, we first confirmed that all four compounds induced hyperactivation. Subsequently, sperm were allowed to bind to immobilized oviduct glycans, and compounds or vehicle controls were added. All compounds caused sperm release from immobilized glycans, demonstrating that hyperactivation was sufficient to release sperm from oviduct cells and immobilized glycans. Pharmacological inhibition of the non-genomic progesterone receptor and CatSper diminished sperm release from oviduct glycans. Inhibition of the proteolytic activities of the ubiquitin-proteasome system (UPS), implicated in the regulation of sperm capacitation, diminished sperm release in response to all hyperactivation inducers. In summary, induction of sperm hyperactivation was sufficient to induce sperm release from immobilized oviduct glycans and release was dependent on CatSper and the UPS.

Boar Sperm Cryopreservation Improvement Using Semen Extender Modification by Dextran and Pentaisomaltose

The long-term storage of boar sperm presents an ongoing challenge, and the modification of the cryoprotective compounds in semen extenders is crucial for improving cryopreservation’s success rate. The aim of our study was to reduce the percentage of glycerol in the extender by elimination or substitution with biocompatible, non-toxic polysaccharides. For boar semen extender improvement, we tested a novel modification with the polysaccharides dextran and pentaisomaltose in combination with unique in silico predictive modeling. We targeted the analysis of in vitro qualitative sperm parameters such as motility, viability, mitochondrial activity, acrosome integrity, and DNA integrity. Non-penetrating polysaccharide-based cryoprotective agents interact with sperm surface proteins such as spermadhesins, which are recognized as fertility markers of boar sperm quality. The in silico docking study showed a moderate binding affinity of dextran and pentaisomaltose toward one specific spermadhesin known as AWN, which is located in the sperm plasma membrane. Pentaisomaltose formed a hydrophobic pocket for the AWN protein, and the higher energy of this protein–ligand complex compared with dextran was calculated. In addition, the root mean square deviation (RMSD) analysis for the molecular dynamics (MD) of both polysaccharides and AWN simulation suggests their interaction was highly stable. The in silico results were supported by in vitro experiments. In the experimental groups where glycerol was partially or entirely substituted, the use of pentaisomaltose resulted in improved sperm mitochondrial activity and DNA integrity after thawing when compared with dextran. In this paper, we demonstrate that pentaisomaltose, previously used for cryopreservation in hematopoietic stem cells, represents a promising compound for the elimination or reduction of glycerol in extenders for boar semen cryopreservation. This novel approach, using in silico computer prediction and in vitro testing, represents a promising technique to help identify new cryoprotectants for use in animal breeding or genetic resource programs.

Sperm Transcripts Associated With Odorant Binding and Olfactory Transduction Pathways Are Altered in Breeding Bulls Producing Poor-Quality Semen

Spermatozoa carries a reservoir of mRNAs regulating sperm functions and fertilizing potential. Although it is well recognized that a considerable proportion of high genetic merit breeding bulls produce poor-quality semen, the transcriptomic alterations in spermatozoa from such bulls are not understood. In the present study, comparative high-throughput transcriptomic profiling of spermatozoa from good and poor-quality semen-producing bulls was carried out to identify the transcripts associated with semen quality. Using next-generation sequencing (NGS), we identified 11,632 transcripts in Holstein Friesian bull spermatozoa; after total hit normalization, a total of 544 transcripts were detected, of which 185 transcripts were common to both good and poor-quality semen, while 181 sperm transcripts were unique to good quality semen, and 178 transcripts were unique to poor-quality semen. Among the co-expressed transcripts, 31 were upregulated, while 108 were downregulated, and 46 were neutrally expressed in poor-quality semen. Bioinformatics analysis revealed that the dysregulated transcripts were predominantly involved in molecular function, such as olfactory receptor activity and odor binding, and in biological process, such as detection of chemical stimulus involved in sensory perception, sensory perception of smell, signal transduction, and signal synaptic transmission. Since a majority of the dysregulated transcripts were involved in the olfactory pathway (85% of enriched dysregulated genes were involved in this pathway), the expression of selected five transcripts associated with this pathway (OR2T11, OR10S1, ORIL3, OR5M11, and PRRX1) were validated using real-time qPCR, and it was found that their transcriptional abundance followed the same trend as observed in NGS; the sperm transcriptional abundance of OR2T11 and OR10S1 differed significantly (p < 0.05) between good and poor-quality semen. It is concluded that poor-quality semen showed altered expression of transcripts associated with olfactory receptors and pathways indicating the relationship between olfactory pathway and semen quality in bulls.

Bundle formation of sperm: Influence of environmental factors

Cooperative behaviour of sperm is one of the mechanisms that plays a role in sperm competition. It has been observed in several species that spermatozoa interact with each other to form agglomerates or bundles. In this study, we investigate the effect of physical and biochemical factors that will most likely promote bundle formation in bull sperm. These factors include fluid viscosity, swim-up process, post-thaw incubation time and media additives which promote capacitation. While viscosity does not seem to influence the degree of sperm bundling, swim-up, post-thaw migration time and suppressed capacitation increase the occurrence of sperm bundles. This leads to the conclusion that sperm bundling is a result of hydrodynamic and adhesive interactions between the cells which occurs frequently during prolonged incubation times.

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.

Assessment of Sperm Binding Capacity in the Tubal Reservoir Using a Bovine Ex Vivo Oviduct Culture and Fluorescence Microscopy

Sperm binding within the oviductal sperm reservoir plays an important role for reproductive success by enabling sperm survival and maintaining fertilizing capacity. To date, numerous in vitro technologies have been established to measure sperm binding capacity to cultured oviductal cells or oviductal explants. However, these methods do not accurately represent the microenvironment and complex multi-molecular nature of the oviduct. In this paper, we describe a novel protocol for assessing sperm binding capacity in the tubal sperm reservoir using an ex vivo oviduct culture in the bovine model. This protocol includes the staining of frozen-thawed bovine spermatozoa with the DNA-binding dye Hoechst 33342, the co-incubation of stained sperm in closed segments of the oviduct and the visualization and quantification of bound spermatozoa by fluorescence microscopy. By generating overlays of multiple Z-stacks of randomly selected regions of interest (ROIs), spermatozoa bound in the sperm reservoir can be visualized and quantified within the 3D arrangement of the oviductal folds. This method, which is applicable to multiple species, can be used to assess individual sperm binding capacity in males for prognostic purposes as well as to assess the impact of diseases and medications on the formation of the sperm reservoir in the oviduct in humans and animals.

αV Integrin Expression and Localization in Male Germ Cells

Integrins are transmembrane receptors that facilitate cell adhesion and cell–extracellular matrix communication. They are involved in the sperm maturation including capacitation and gamete interaction, resulting in successful fertilization. αV integrin belongs to the integrin glycoprotein superfamily, and it is indispensable for physiological spermiogenesis and testosterone production. We targeted the gene and protein expression of the αV integrin subunit and described its membrane localization in sperm. Firstly, in mouse, we traced αV integrin gene expression during spermatogenesis in testicular fraction separated by elutriation, and we detected gene activity in spermatogonia, spermatocytes, and round spermatids. Secondly, we specified αV integrin membrane localization in acrosome-intact and acrosome-reacted sperm and compared its pattern between mouse, pig, and human. Using immunodetection and structured illumination microscopy (SIM), the αV integrin localization was confined to the plasma membrane covering the acrosomal cap area and also to the inner acrosomal membrane of acrosome-intact sperm of all selected species. During the acrosome reaction, which was induced on capacitated sperm, the αV integrin relocated and was detected over the whole sperm head. Knowledge of the integrin pattern in mature sperm prepares the ground for further investigation into the pathologies and related fertility issues in human medicine and veterinary science.

Expression Profile of New Gene Markers and Signaling Pathways Involved in Immunological Processes in Human Cumulus-Oophorus Cells

The function of the immune system extends from defense against external pathogens to the recognition and elimination of mutated or dying cells, aiding elimination of malignant potential and/or maintaining homeostasis. The many cell types of the immune system secrete a broad range of factors to enable cellular signaling that is vital to physiological processes. Additionally, in the ovary, follicular selection and maturation, as well as ovulation, are directly regulated by the nearby immune cells. Additionally, ovulation and rupture of the follicle have been observed to resemble a local inflammatory response. Cells of the cumulus–oocyte complex (COC) show evolving gene expression profiles throughout the oocytes’ lifespan, including genes associated with immunological processes. Analysis of these genes allows the identification of useful molecular markers, as well as highlighting gene functions and interactions in these cells. Cumulus cells were obtained from hormonally stimulated patients undergoing an in vitro fertilization procedure and studied under long-term culture conditions. The microarray technique made it possible to compare the level of CCs’ gene expression on the 1st, 7th, 15th and 30th day of cultivation. Additionally, RNA microarray analysis was performed to map gene expression in these cells, associated with immunological processes and associated cytokine signaling. Subsequently, the use of DAVID software allowed us to identify the “defense response to other organism”, “defense response”, “defense response to virus”, “cytokine secretion”, “cytokine production” and “cytokine-mediated signaling pathway” GO BP terms, as well as allowing further analysis of the most differentially expressed genes associated with these processes. Of the 122 genes involved, 121 were upregulated and only one was downregulated. The seven most upregulated genes related to the abovementioned terms were ANXA3, IFIT1, HLA-DPA1, MX1, KRT8, HLA-DRA and KRT18. Therefore, genes involved in immunological defense processes are upregulated in CC cultures and could serve as useful molecular markers of growth and development in the COC, as well as the proliferation of granulosa and cumulus cells.

Sperm Oxidative Stress during In Vitro Manipulation and Its Effects on Sperm Function and Embryo Development

Reactive oxygen species (ROS) generated at low levels during mitochondrial respiration have key roles in several signaling pathways. Oxidative stress (OS) arises when the generation of ROS exceeds the cell's antioxidant scavenging ability and leads to cell damage. Physiological ROS production in spermatozoa regulates essential functional characteristics such as motility, capacitation, acrosome reaction, hyperactivation, and sperm-oocyte fusion. OS can have detrimental effects on sperm function through lipid peroxidation, protein damage, and DNA strand breakage, which can eventually affect the fertility of an individual. Substantial evidence in the literature indicates that spermatozoa experiencing OS during in vitro manipulation procedures in human- and animal-assisted reproduction are increasingly associated with iatrogenic ROS production and eventual impairment of sperm function. Although a direct association between sperm OS and human assisted reproductive techniques (ART) outcomes after in vitro fertilization (IVF) and/or intracytoplasmic sperm injection (ICSI) is still a matter of debate, studies in animal models provide enough evidence on the adverse effects of sperm OS in vitro and defective fertilization and embryo development. This review summarized the literature on sperm OS in vitro, its effects on functional ability and embryo development, and the approaches that have been proposed to reduce iatrogenic sperm damage and altered embryonic development.

Effects of In Vitro Interactions of Oviduct Epithelial Cells with Frozen-Thawed Stallion Spermatozoa on Their Motility, Viability and Capacitation Status

Simple Summary

The use of assisted reproductive techniques, which involve the manipulation of sperm and oocytes in the laboratory, support owner production of valuable animals’ offspring. However, several limitations remain underlining the need to further optimize existing protocols as well as to develop new strategies. For example, the required conditions to make equine spermatozoa competent to fertilize an oocyte in vitro (IVF) have not been established. Therefore, our initial goal was to optimize different conditions associated with frozen equine sperm manipulations in order to improve their quality. We observed that simple factors such as sample concentration, incubation period and centrifugation time affect the sperm motility. Since in vivo fertilization involves the interaction between spermatozoa and epithelial cells in the mare’s oviductal tract, our next goal was to mimic this environment by establishing primary cultures of oviductal cells. Using this in vitro system, we were able to select a sperm population capable of fertilization. In short, this study provides a novel protocol that improves the yield of fertilization-capable sperm obtained from equine frozen spermatozoa.

Abstract

Cryopreservation by negatively affecting sperm quality decreases the efficiency of assisted reproduction techniques (ARTs). Thus, we first evaluated sperm motility at different conditions for the manipulation of equine cryopreserved spermatozoa. Higher motility was observed when spermatozoa were incubated for 30 min at 30 × 10⁶/mL compared to lower concentrations (p < 0.05) and when a short centrifugation at 200× g was performed (p < 0.05). Moreover, because sperm suitable for oocyte fertilization is released from oviduct epithelial cells (OECs), in response to the capacitation process, we established an in vitro OEC culture model to select a sperm population with potential fertilizing capacity in this species. We demonstrated E-cadherin and cytokeratin expression in cultures of OECs obtained. When sperm–OEC cocultures were performed, the attached spermatozoa were motile and presented an intact acrosome, suggesting a selection by the oviductal model. When co-cultures were incubated in capacitating conditions a greater number of alive (p < 0.05), capacitated (p < 0.05), with progressive motility (p < 0.05) and with the intact acrosome sperm population was observed (p < 0.05) suggesting that the sperm population released from OECs in vitro presents potential fertilizing capacity. Improvements in handling and selection of cryopreserved sperm would improve efficiencies in ARTs allowing the use of a population of higher-quality sperm.

Еffect of different breeds on the protein profile in ram seminal plasma

In this study the individual profiles of seminal plasma proteins (SPP) in rams of three breeds – Merino, Pleven Blackhead and Ile de France - were analysed. The study was carried out with three rams at 3, 6 and 10 years of age, grown and fed under similar conditions. Eighteen ejaculates (6 ejaculates from each ram) were evaluated by Sperm Class Analyzer. The total SPP concentration was measured spectrophotometrically. The separation and characterisation of SPP was performed by HPLC and one dimensional polyacrylamide gel electrophoresis (SDS-PAGE). There were no significant differences between the characteristics of ejaculates and the main kinematic parameters of the sperm in the breeds studied. Chromatograms showed specific profiles with 9, 10 and 11 protein peaks for Merino, Pleven Blackhead and Ile de France breeds, respectively. The total SPP concentration was the highest in the Pleven Blackhead breed and the lowest in Ile de France breed. The major parts of SPP in the three breeds were identical. The seminal plasma of Merino breed contained proteins with molecular mass of 30.3 kDa, 15.7 kDa and 15.2 kDa that were not present in the other two breeds. In the Ile de France and Pleven Blackhead samples only, two proteins with molecular masses of 39.7 kDa and 21.1 kDa, were observed. In conclusion, the detection of specific proteins can be used as a biological marker for sheep breed identification.

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

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

Sperm interactions with the female reproductive tract: A key for successful fertilization in mammals

Sperm migration through the female genital tract is not a quiet journey. Uterine contractions quickly operate a drastic selection, leading to a very restrictive number of sperm reaching the top of uterine horns and finally, provided the presence of key molecules on sperm, the oviduct, where fertilization takes place. During hours and sometimes days before fertilization, subpopulations of spermatozoa interact with dynamic and region-specific maternal components, including soluble proteins, extracellular vesicles and epithelial cells lining the lumen of the female tract. Interactions with uterine and oviductal cells play important roles for sperm survival as they modulate the maternal immune response and allow a transient storage before ovulation. The body of work reported here highlights the importance of sperm interactions with proteins originated from both the uterine and oviductal fluids, as well as hormonal signals around the time of ovulation for sperm acquisition of fertilizing competence.

Epididymal and ejaculated sperm functionality is regulated differently by periovulatory oviductal fluid in pigs

BACKGROUND

The current results of in vitro reproduction techniques in pigs, such as in vitro fertilization (IVF) and embryo development, show high performance with both epididymal and ejaculated spermatozoa. However, the results using ejaculated spermatozoa are even better. Ejaculated spermatozoa are exposed to the secretions of the accessory seminal glands: the seminal plasma (SP). It has been reported that exposure of spermatozoa to reproductive fluids, such as SP or periovulatory oviductal fluid (pOF), modulates sperm functionality both in vivo and in vitro. But whether or not this modulating effect of pOF depends on the origin of the spermatozoa being epididymal or ejaculated, is still unknown.

OBJECTIVES

To determine and compare the effect of pOF on epididymal and ejaculated sperm functionality.

MATERIAL AND METHODS

The effects of incubating spermatozoa from the epididymis and ejaculate with pOF in capacitating conditions were investigated by analyzing sperm motility, phosphorylation of protein kinase A substrates and proteins in tyrosine (pPKAs and pTyr, respectively), the interaction of the spermatozoa with the oocyte in IVF and intracytoplasmic sperm injection (ICSI), and, finally, the spermatozoa chromatin condensation status.

RESULTS

The pOF modified events related to capacitation in epididymal spermatozoa by decreasing motility, pPKAs and pTyr. In the interaction with the oocyte after sperm capacitation, pOF regulated the epididymal and ejaculated spermatozoa differently. While pOF decreased the number of spermatozoa bound to the zona pellucida (Spz/ZP) and increased oocyte activation after ICSI with epididymal spermatozoa, with the ejaculated spermatozoa, it decreased the mean number penetrating each oocyte (Spz/O). Additionally, pOF significantly increased the nuclear decondensation of the epididymal spermatozoa after the fertilization of the oocyte.

CONCLUSION

The modulation of sperm functionality by pOF is conditioned by the origin of the spermatozoa.

Sperm Proteome after Interaction with Reproductive Fluids in Porcine: From the Ejaculation to the Fertilization Site

Ejaculated sperm are exposed to different environments before encountering the oocyte. However, how the sperm proteome changes during this transit remains unsolved. This study aimed to identify proteomic changes in boar sperm after incubation with male (seminal plasma, SP) and/or female (uterine fluid, UF; and oviductal fluid, OF) reproductive fluids. The following experimental groups were analyzed: (1) SP: sperm + 20% SP; (2) UF: sperm + 20% UF; (3) OF: sperm + 20% OF; (4) SP + UF: sperm + 20% SP + 20% UF; and (5) SP+OF: sperm + 20% SP + 20% OF. The proteome analysis, performed by HPLC-MS/MS, allowed the identification of 265 proteins. A total of 69 proteins were detected in the UF, SP, and SP + UF groups, and 102 proteins in the OF, SP, and SP + OF groups. Our results showed a higher number of proteins when sperm were incubated with only one fluid than when they were co-incubated with two fluids. Additionally, the number of sperm-interacting proteins from the UF group was lower than the OF group. In conclusion, the interaction of sperm with reproductive fluids alters its proteome. The description of sperm-interacting proteins in porcine species after co-incubation with male and/or female reproductive fluids may be useful to understand sperm transport, selection, capacitation, or fertilization phenomena.

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

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

Ram seminal plasma and its functional proteomic assessment

Ejaculation results in the confluence of epididymal spermatozoa with secretions of the accessory sex glands. This interaction is not a prerequisite for fertilisation success, but seminal factors do play a crucial role in prolonging the survival of spermatozoa both in vitro and in vivo by affording protection from handling induced stress and some selective mechanisms of the female reproductive tract. Reproductive biologists have long sought to identify specific factors in seminal plasma that influence sperm function and fertility in these contexts. Many seminal plasma proteins have been identified as diagnostic predictors of sperm function and have been isolated and applied in vitro to prevent sperm damage associated with the application of artificial reproductive technologies. Proteomic assessment of the spermatozoon, and its surroundings, has provided considerable advances towards these goals and allowed for greater understanding of their physiological function. In this review, the importance of seminal plasma will be examined through a proteomic lens to provide comprehensive analysis of the ram seminal proteome and detail the use of proteomic studies that correlate seminal plasma proteins with ram sperm function and preservation ability.

Identification of lipid raft glycoproteins obtained from boar spermatozoa

The surface of the spermatozoa is coated with glycoproteins the redistribution of which during in vitro capacitation plays a key role in the subsequent fertilization process. Lipid rafts are membrane microdomains involved in signal transduction through receptors and include or recruit specific types of proteins and glycoproteins. Few studies have focused on identifying glycoproteins resident in the lipid rafts of spermatozoa. Proteins associated with lipid rafts modify their localization during capacitation. The objective of the study was to identify the glycoproteins associated with lipid rafts of capacitated boar spermatozoa through a lectin-binding assay coupled to mass spectrometry approach. From the proteomic profiles generated by the raft proteins extractions, we observed that after capacitation the intensity of some bands increased while that of others decreased. To determine whether the proteins obtained from lipid rafts are glycosylated, lectin blot assays were performed. Protein bands with a good resolution and showing significant glycosylation modifications after capacitation were analyzed by mass spectrometry. The bands of interest had an apparent molecular weight of 64, 45, 36, 34, 24, 18 and 15 kDa. We sequenced the 7 bands and 20 known or potential glycoproteins were identified. According to us, for ten of them this is the first time that their association with sperm lipid rafts is described (ADAM5, SPMI, SPACA1, Seminal plasma protein pB1, PSP-I, MFGE8, tACE, PGK2, SUCLA2, MDH1). Moreover, LYDP4, SPAM-1, HSP60, ZPBP1, AK1 were previously reported in lipid rafts of mouse and human spermatozoa but not in boar spermatozoa. We also found and confirmed the presence of ACR, ACRBP, AWN, AQN3 and PRDX5 in lipid rafts of boar spermatozoa. This paper provides an overview of the glycosylation pattern in lipid rafts of boar spermatozoa before and after capacitation. Further glycomic analysis is needed to determine the type and the variation of glycan chains of the lipid rafts glycoproteins on the surface of spermatozoa during capacitation and acrosome reaction.

Post-ejaculatory modifications to sperm (PEMS)

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

Avian uterine fluid proteome: Exosomes and biological processes potentially involved in sperm survival

Uterine fluid is an aqueous milieu to which sperm are exposed during their storage and ascent. In this study, a bottom-up proteomic strategy and bioinformatic analysis of hen uterine fluid was performed to improve the understanding of this fluid and its potential role in sperm survival mechanisms. The proteomic data were submitted to ProteomeXchange. Among the 913 proteins identified, 160 are known to be secreted and 640 are referenced in exosomes databases. We isolated exosomes from the avian uterine fluid, analyzed them using electron microscopy, and targeted several exosomes markers (ANXA1/2/4/5, VCP, HSP90A, HSPA8, PARK7, and MDH1) using immunoblotting. Electron microscopy and immunohistochemistry were also used to analyze uterovaginal junctions for the exosomal proteins ANXA4, VCP, and PARK7. Exosomes were observed both at the surface epithelium and inside sperm storage tubules. Our data were compared with two previously published studies on proteomic of hen uterine fluid, and with one study describing the proteomic content of rooster seminal plasma and sperm. In conclusion, we demonstrated for the first time that avian uterine fluid contains exosomes. These may play a key role in preserving sperm functions within the female genital tract. Their presence in the sperm storage tubules may represent an important mechanism regarding interaction between the female genital tract and sperm.

Porcine model for the study of sperm capacitation, fertilization and male fertility

Mammalian fertilization remains a poorly understood event with the vast majority of studies done in the mouse model. The purpose of this review is to revise the current knowledge about semen deposition, sperm transport, sperm capacitation, gamete interactions and early embryonic development with a focus on the porcine model as a relevant, alternative model organism to humans. The review provides a thorough overview of post-ejaculation events inside the sow's reproductive tract including comparisons with humans and implications for human fertilization and assisted reproductive therapy (ART). Porcine methodology for sperm handling, preservation, in vitro capacitation, oocyte in vitro maturation, in vitro fertilization and intra-cytoplasmic sperm injection that are routinely used in pig research laboratories can be successfully translated into ART to treat human infertility. Last, but not least, new knowledge about mitochondrial inheritance in the pig can provide an insight into human mitochondrial diseases and new knowledge on polyspermy defense mechanisms could contribute to the development of new male contraceptives.

Adhesion molecules in gamete transport, fertilization, early embryonic development, and implantation-role in establishing a pregnancy in cattle: A review

Cell-cell adhesion molecules have critically important roles in the early events of reproduction including gamete transport, sperm-oocyte interaction, embryonic development, and implantation. Major adhesion molecules involved in reproduction include cadherins, integrins, and disintegrin and metalloprotease domain-containing (ADAM) proteins. ADAMs on the surface of sperm adhere to integrins on the oocyte in the initial stages of sperm-oocyte interaction and fusion. Cadherins act in early embryos to organize the inner cell mass and trophectoderm. The trophoblast and uterine endometrial epithelium variously express cadherins, integrins, trophinin, and selectin, which achieve apposition and attachment between the elongating conceptus and uterine epithelium before implantation. An overview of the major cell-cell adhesion molecules is presented and this is followed by examples of how adhesion molecules help shape early reproductive events. The argument is made that a deeper understanding of adhesion molecules and reproduction will inform new strategies that improve embryo survival and increase the efficiency of natural mating and assisted breeding in cattle.

Oviductal extracellular vesicles interact with the spermatozoon's head and mid-piece and improves its motility and fertilizing ability in the domestic cat

Fertilization and early embryo development are regulated by a unique maternal-gamete/embryo cross-talk within the oviduct. Recent studies have shown that extracellular vesicles (EVs) within the oviduct play important roles in mediating this developmental process. Here, we examined the influence of oviductal EVs on sperm function in the domestic cat. We demonstrated that (1) EVs are enriched in proteins related to energy metabolism, membrane modification, and reproductive function; (2) EVs bound and fused with the membranes of the acrosome and mid piece; and (3) incubating sperm with EVs improved motility, fertilizing capacity of cat spermatozoa and prevented acrosomal exocytosis in vitro. These findings indicated that oviductal EVs mediate sperm function and fertilization in the cat and provides new insights to improve sperm cryopreservation and in vitro fertilization in the domestic and wild felids and human.

Seminal plasma proteins as markers of sperm fertility

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

An oviduct-on-a-chip provides an enhanced in vitro environment for zygote genome reprogramming

Worldwide over 5 million children have been conceived using assisted reproductive technology, and research has concentrated on increasing the likelihood of ongoing pregnancy. However, studies using animal models have indicated undesirable effects of in vitro embryo culture on offspring development and health. In vivo, the oviduct hosts a period in which the early embryo undergoes complete reprogramming of its (epi)genome in preparation for the reacquisition of (epi)genetic marks. We designed an oviduct-on-a-chip platform to better investigate the mechanisms related to (epi)genetic reprogramming and the degree to which they differ between in vitro and in vivo embryos. The device supports more physiological (in vivo-like) zygote genetic reprogramming than conventional IVF. This approach will be instrumental in identifying and investigating factors critical to fertilization and pre-implantation development, which could improve the quality and (epi)genetic integrity of IVF zygotes with likely relevance for early embryonic and later fetal development.

Genes Encoding Mammalian Oviductal Proteins Involved in Fertilization are Subjected to Gene Death and Positive Selection

Oviductal proteins play an important role in mammalian fertilization, as proteins from seminal fluid. However, in contrast with the latter, their phylogenetic evolution has been poorly studied. Our objective was to study in 16 mammals the evolution of 16 genes that encode oviductal proteins involved in at least one of the following steps: (1) sperm–oviduct interaction, (2) acrosome reaction, and/or (3) sperm–zona pellucida interaction. Most genes were present in all studied mammals. However, some genes were lost along the evolution of mammals and found as pseudogenes: annexin A5 (ANXA5) and deleted in malignant brain tumor 1 (DMBT1) in tarsier; oviductin (OVGP1) in megabat; and probably progestagen-associated endometrial protein (PAEP) in tarsier, mouse, rat, rabbit, dolphin, and megabat; prostaglandin D2 synthase (PTGDS) in microbat; and plasminogen (PLG) in megabat. Four genes [ANXA1, ANXA4, ANXA5, and heat shock 70 kDa protein 5 (HSPA5)] showed branch-site positive selection, whereas for seven genes [ANXA2, lactotransferrin (LTF), OVGP1, PLG, S100 calcium-binding protein A11 (S100A11), Sperm adhesion molecule 1 (SPAM1), and osteopontin (SPP1)] branch-site model and model-site positive selection were observed. These results strongly suggest that genes encoding oviductal proteins that are known to be important for gamete fertilization are subjected to positive selection during evolution, as numerous genes encoding proteins from mammalian seminal fluid. This suggests that such a rapid evolution may have as a consequence that two isolated populations become separate species more rapidly.

Differences in sperm protein abundance and carbonylation level in bull ejaculates of low and high quality

In breeding and insemination centres, significant variation in bull ejaculate quality is often observed between individuals and also within the same individual. Low-quality semen does not qualify for cryopreservation and is rejected, generating economic loss. The mechanisms underlying the formation of low-quality ejaculates are poorly understood; therefore, the aim of the present study was to investigate the proteomic differences and oxidative modifications (measured as changes in protein carbonylation level) of bull ejaculates of low and high quality. Flow cytometry and computer-assisted sperm analysis were used to assess differences in viability, reactive oxygen species (ROS) level, and sperm motility. To analyse changes in protein abundance, two-dimensional difference gel electrophoresis (2D-DIGE) was performed. Western blotting in conjunction with two-dimensional electrophoresis (2D-oxyblot) was used to quantitate carbonylated sperm proteins. Proteins were identified using matrix-assisted laser desorption/ionisation time-of-flight/time-of-flight spectrometry. High quality ejaculates were characterised by higher sperm motility, viability, concentration, and a lower number of ROS-positive cells (ROS⁺). We found significant differences in the protein profile between high- and low-quality ejaculates, and identified 14 protein spots corresponding to 10 proteins with differences in abundance. The identified sperm proteins were mainly associated with energetic metabolism, capacitation, fertilisation, motility, and cellular detoxification. High-quality ejaculates were characterised by a high abundance of extracellular sperm surface proteins, likely due to more efficient secretion from accessory sex glands and/or epididymis, and a low abundance of intracellular proteins. Our results show that sperm proteins in low-quality ejaculates are characterised by a high carbonylation level. Moreover, we identified, for the first time, 14 protein spots corresponding to 12 proteins with differences in carbonylation level between low- and high-quality ejaculates. The carbonylated proteins were localised mainly in mitochondria or their immediate surroundings. Oxidative damage to proteins in low-quality semen may be associated with phosphorylation/dephosphorylation disturbances, mitochondrial dysfunction, and motility apparatus disorders. Our results contribute to research regarding the mechanism by which low- and high-quality ejaculates are formed and to the identification of sperm proteins that are particularly sensitive to oxidative damage.

Finite cell lines of turkey sperm storage tubule cells: ultrastructure and protein analysis

Cell lines of turkey sperm storage tubule (SST) epithelial cells were established. Turkey SSTs were dissected from freshly obtained uterovaginal junction (UVJ) tissue and placed in explant culture on various substrates and media. Primary cultures of SST epithelium only survived and grew from SST explants that were cultured on inactivated Sandoz inbred strain, thioguanine- and ouabain-resistance (STO) mouse feeder-cell layers in 12% fetal bovine serum-supplemented Dulbecco's Modified Eagle Medium mixed 1:1 with F12 nutrient mixture. Three independent primary colonies gave rise to 3 finite cell lines, SST-1, -2, and -3, which were continuously cultured for 8 to 16 passages at 1:3 passage ratios over a period of 3 to 4 mo. The cells were passaged by pretreatment with Y27632 and dissociation with Accutase. The SST cells grew as tightly knit monolayers on top of the feeder cells at a slow rate (approximately 96 h doubling time) at a medium pH of approximately 6.9. Lipid vacuoles were visible by light microscopy in the cells particularly at the periphery of growth. Transmission electron microscopy revealed the cells to be a polarized epithelium with apical microvilli and to have lateral tight-junction-like unions and associated desmosomes. Numerous secretory vesicles filled the upper portion of the cells’ cytoplasm, and nuclei and other major organelles such as mitochondria, rough endoplasmic reticulum, and Golgi apparatus were distributed somewhat lower in the cytoplasm. The secretory vesicles resembled mucin secretory vesicles. Proteomic analysis by mass spectroscopy of the conditioned medium of the cells, and of the cells themselves, showed the cell lines did not secrete large amounts of any particular protein, and the analysis confirmed their epithelial character. In conclusion, the SST-derived cell lines resembled the mucus-secreting cells found in the epithelium lining the UVJ of the turkey's reproductive tract.

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.

Gamete-mediated mate choice: towards a more inclusive view of sexual selection

'Sperm competition'-where ejaculates from two or more males compete for fertilization-and 'cryptic female choice'-where females bias this contest to suit their reproductive interests-are now part of the everyday lexicon of sexual selection. Yet the physiological processes that underlie these post-ejaculatory episodes of sexual selection remain largely enigmatic. In this review, we focus on a range of post-ejaculatory cellular- and molecular-level processes, known to be fundamental for fertilization across most (if not all) sexually reproducing species, and point to their putative role in facilitating sexual selection at the level of the cells and gametes, called 'gamete-mediated mate choice' (GMMC). In this way, we collate accumulated evidence for GMMC across different mating systems, and emphasize the evolutionary significance of such non-random interactions among gametes. Our overall aim in this review is to build a more inclusive view of sexual selection by showing that mate choice often acts in more nuanced ways than has traditionally been assumed. We also aim to bridge the conceptual divide between proximal mechanisms of reproduction, and adaptive explanations for patterns of non-random sperm-egg interactions that are emerging across an increasingly diverse array of taxa.

Oviductal epithelial cells selected boar sperm according to their functional characteristics

The interaction of oviductal epithelial cells (OECs) with the spermatozoa has beneficial effects on the sperm functions. The aim of this study is to evaluate the in vitro fertilizing capacity of incubating spermatozoa previously selected by density gradient in OEC and determinate some sperm characteristics that could explain the results obtained. In this study, we assessed in vitro fertilization (IVF), tyrosine phosphorylation, phosphatidylserine translocation, nuclear DNA fragmentation, and chromatin decondensation. Three experimental sperm groups, previously selected by Percoll gradient, were established according to the origin of the sperm used for IVF: (i) W30 group: spermatozoa were incubated with oocytes in the absence of OEC; (ii) NB group: after sperm incubation in OEC, the unbound spermatozoa were incubated with oocytes, in the absence of OEC; and (iii) B group: after sperm incubation with OEC, the bound spermatozoa were incubated with oocytes in the OEC plates. The results showed that sperm from the NB group led to a lower IVF yield, accompanied by low penetration rates (NB: 19.6%, B: 94.9%, and W30: 62.9%; P < 0.001) and problems of nuclear decondensation. Moreover, higher levels of tyrosine phosphorylation were observed in the NB group compared with the W30 and B groups (NB: 58.7%, B: 2.5%, and W30: 4.5%; P < 0.01). A similar trend was observed in phosphatidylserine translocation (NB: 93.7%, B: 5.7%, and W30: 44.2%; P < 0.01). These results demonstrate that the OEC exerts a rigorous degree of sperm selection, even within an already highly selected population of spermatozoa, and can capture the best functional spermatozoa for fertilization.

Review: The epic journey of sperm through the female reproductive tract

Millions or billions of sperm are deposited by artificial insemination or natural mating into the cow reproductive tract but only a few arrive at the site of fertilization and only one fertilizes an oocyte. The remarkable journey that successful sperm take to reach an oocyte is long and tortuous, and includes movement through viscous fluid, avoiding dead ends and hostile immune cells. The privileged collection of sperm that complete this journey must pass selection steps in the vagina, cervix, uterus, utero-tubal junction and oviduct. In many locations in the female reproductive tract, sperm interact with the epithelium and the luminal fluid, which can affect sperm motility and function. Sperm must also be tolerated by the immune system of the female for an adequate time to allow fertilization to occur. This review emphasizes literature about cattle but also includes work in other species that emphasizes critical broad concepts. Although all parts of the female reproductive tract are reviewed, particular attention is given to the sperm destination, the oviduct.

Identification by proteomics of oviductal sperm-interacting proteins

The interactions between oviductal fluid (OF) proteins and spermatozoa play major roles in sperm selection, storage and capacitation before fertilization. However, only a few sperm-interacting proteins in the OF has been identified and very little is known about the regulation of sperm-oviduct interactions across the estrous cycle. Samples of bovine frozen-thawed sperm from three bulls were incubated with OF at pre-, post-ovulatory stages (Pre-/Post-ov) or luteal phase (LP) of the estrous cycle (7 mg/mL proteins, treated groups) or with a protein-free media (control). The proteomes of sperm cells were assessed by nanoLC-MS/MS and quantified by label-free methods. A total of 27 sperm-interacting proteins originating in the OF were identified. Among those, 14 were detected at all stages, eight at Post-ov and LP and five only at LP. The sperm-interacting proteins detected at all stages or at LP and Post-ov were on average more abundant at LP than at other stages (P < 0.05). At Pre-ov, OVGP1 was the most abundant sperm-interacting protein while at Post-ov, ACTB, HSP27, MYH9, MYH14 and OVGP1 were predominant. Different patterns of abundance of sperm-interacting proteins related to the stage were evidenced, which greatly differed from those previously reported in the bovine OF. In conclusion, this study highlights the important regulations of sperm-oviduct interactions across the estrous cycle and provides new protein candidates that may modulate sperm functions.

Sex Steroid-Mediated Control of Oviductal Function in Cattle

In cattle, the oviduct is a tubular organ that connects the ovary and the uterus. The oviduct lumen stages a dynamic set of cellular and molecular interactions to fulfill the noble role of generating a new individual. Specific anatomical niches along the oviduct lumen provide the appropriate microenvironment for final sperm capacitation, oocyte capture and fertilization, and early embryo development and transport. To accomplish such complex tasks, the oviduct undergoes spatially and temporally-regulated morphological, biochemical, and physiological changes that are associated with endocrine events of the estrous cycle. Specifically, elevated periovulatory concentrations of estradiol (E2) and progesterone (P4) influence gene expression and morphological changes that have been associated positively to fertility in beef cattle. In this review, we explore how E2 and P4 influence oviductal function in the beginning of the estrous cycle, and prepare the oviductal lumen for interactions with gametes and embryos.

Chang's meaning of capacitation: A molecular perspective

Dr. Min Chue Chang's contributions to the field of reproductive biology set the stage for the development of the contraceptive pill and in vitro fertilization. Throughout his publications, Dr. Chang was also able to transmit his view of the fertilization process in ways that organized research for newer generations of reproductive biologists. Particularly relevant for the achievement of in vitro fertilization in mammals was the discovery that the sperm required a period of residence in the female tract to become fertilization-competent; Dr. Chang and Dr. Austin, in Australia, independently reported this process, now known as sperm capacitation. This review discusses Dr. Chang's views on capacitation, and puts them in the context of recent advances in the understanding of the molecular basis of this process. Mol. Reprod. Dev. 83: 860-874, 2016 © 2016 Wiley Periodicals, Inc.