Sperm-oviduct interaction: induction of capacitation and preferential binding of uncapacitated spermatozoa to oviductal epithelial cells in porcine species

Phosphatidylserine on sperm head interact with Annexin A5 on oviduct luminal cilia to form a sperm reservoir in pigs

After insemination, a subpopulation of sperm reaches the oviducts and binds to isthmic epithelial cells to form a "sperm reservoir". Our objective was to explore the role of annexin A5 (ANXA5), a protein that binds with high affinity to phosphatidylserine (PS), in the formation of the sperm reservoir in pigs. Phosphatidylserine was detected on the head of approximately 10 % of boar sperm at ejaculation. Porcine ANXA5 was immunodetected with a strong signal on luminal cilia in the isthmus and in derived isthmic epithelial spheroids (IES). Exogenous PS between 0.01 and 0.1 µg/mL and recombinant porcine ANXA5 (rpANXA5) above 0.1 µg/mL inhibited sperm binding to IES without reducing sperm motility. Pre-incubation of sperm, but not IES, with rpANXA5 inhibited sperm binding to IES. Under capacitating conditions, the proportion of live sperm with head PS exposure and the ability of sperm to bind to rpANXA5 and IES cilia increased within 30 min. Conversely, the acrosome reaction decreased the ability of sperm to bind rpANXA5 and prevented sperm binding to IES. In conclusion, sperm membrane remodelling during capacitation enhanced head PS exposure in motile sperm, resulting in increased interaction with ciliary ANXA5 on isthmic epithelial spheroids. These findings support a role for PS-ANXA5 interaction in the formation of the sperm reservoir in mammalian females.

Guinea pig spermatozoa adhesion to an immobilized fibronectin matrix alters their physiology and increases their survival†

Isthmus is the region of the oviduct considered a reservoir for spermatozoa, where they are retained and released synchronously with ovulation. Integrins mediate this interaction, and it is suggested that they regulate the viability and capacitation of spermatozoa. Spermatozoa retained in the oviductal epithelial cells show specific characteristics: normal morphology, intact acrosome and plasma membrane, no DNA fragmentation, and low levels of intracellular Ca2+, and protein phosphorylation at Tyr. This work aimed to define spermatozoa's ability to adhere to an immobilized fibronectin matrix and its effects on their viability and capacitation. We found that guinea pig spermatozoa showed a high affinity for adhering to an immobilized fibronectin matrix but not to those made up of type 1 collagen or laminin. This interaction was mediated by integrins that recognize the RGD domain. Spermatozoa adhered to an immobilized fibronectin matrix were maintained in a state of low capacitation: low levels of intracellular concentration of Ca2+, protein phosphorylation in Tyr, and F-actin. Also, spermatozoa kept their plasma membrane and acrosome intact, flagellum beating and showed low activation of caspases 3/7. The spermatozoa adhered to the immobilized fibronectin matrix, gradually detached, forming rosettes and did not undergo a spontaneous acrosomal reaction but were capable of experiencing a progesterone-induced acrosomal reaction. In conclusion, the adhesion of spermatozoa to an immobilized fibronectin matrix alters the physiology of the spermatozoa, keeping them in a steady state of capacitation, increasing their viability in a similar way to what was reported for spermatozoa adhered to oviductal epithelial cells.

Sperm selection by the oviduct: perspectives for male fertility and assisted reproductive technologies†

The contribution of sperm to embryogenesis is gaining attention with up to 50% of infertility cases being attributed to a paternal factor. The traditional methods used in assisted reproductive technologies for selecting and assessing sperm quality are mainly based on motility and viability parameters. However, other sperm characteristics, including deoxyribonucleic acid integrity, have major consequences for successful live birth. In natural reproduction, sperm navigate the male and female reproductive tract to reach and fertilize the egg. During transport, sperm encounter many obstacles that dramatically reduce the number arriving at the fertilization site. In humans, the number of sperm is reduced from tens of millions in the ejaculate to hundreds in the Fallopian tube (oviduct). Whether this sperm population has higher fertilization potential is not fully understood, but several studies in animals indicate that many defective sperm do not advance to the site of fertilization. Moreover, the oviduct plays a key role in fertility by modulating sperm transport, viability, and maturation, providing sperm that are ready to fertilize at the appropriate time. Here we present evidence of sperm selection by the oviduct with emphasis on the mechanisms of selection and the sperm characteristics selected. Considering the sperm parameters that are essential for healthy embryonic development, we discuss the use of novel in vitro sperm selection methods that mimic physiological conditions. We propose that insight gained from understanding how the oviduct selects sperm can be translated to assisted reproductive technologies to yield high fertilization, embryonic development, and pregnancy rates.

Effect of zinc on boar sperm liquid storage

Storage and transport of liquid boar sperm for artificial insemination (AI) requires the addition of solutions called extenders, which increase the volume of the ejaculate and help preserve its functional characteristics. Yet, the quality of sperm decreases over time primarily due to the increased production of reactive oxygen species (ROS) that damage the plasma membrane. Many commercial extenders are supplemented with additives that mitigate this effect. In semen, zinc is supplied at high concentration on the seminal plasma and helps protect the plasma membrane of sperm. However, zinc in the seminal plasma is diluted and chelated upon addition of extenders for storage, potentially reducing its antioxidant effect. Here we characterize viability, motility, mitochondrial activity, DNA integrity and ROS content of boar sperm diluted with Sus (Medi Nova, Italy) extender supplemented with different concentrations of ZnCl₂, at intervals after dilution during 3 days. The ability of sperm supplemented with 2 mM ZnCl₂ to fertilize oocytes in vivo of was also tested. Sperm viability was over 82% for all treatments. Mitochondrial integrity analysis, measured by Cytochrome c activity, indicated a protector effect of Zn, noted as a reduced number of sperm with extensive loss of mitochondrial activity. Acrosomal integrity was improved by treatment with all concentrations of ZnCl₂ tested. Sperm kinematics were affected by treatment with ZnCl₂, showing higher percentage of progressive and rapid sperm in doses supplemented with 2mM ZnCl₂. ROS levels and chromatin integrity did not show differences between ZnCl₂-supplemented doses and the control. Fertilization rate, total number, live, still born and mummified piglets did not change when sperm were diluted with extender containing 2 mM ZnCl₂. The presented characterization indicates that Zn addition to Sus extender have a protective effect on mitochondrial sheath and acrosomal membranes; and provides the basis for further studies aimed to optimize sperm performance in AI.

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

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

Assessment of Chilling Injury in Boar Spermatozoa by Kinematic Patterns and Competitive Sperm-Oviduct Binding In Vitro

Sensitive detection of chilling injury in boar spermatozoa is required to evaluate novel hypothermic preservation concepts. The study’s aim was to examine whether analyses of motility patterns and sperm binding in a competitive oviduct explant assay (cOEA) sensitively detect chilling-induced alterations in sperm function. Semen samples (n = seven boars) were split into four subsamples by dilution either in Beltsville Thawing Solution (BTS) or Androstar® Plus and stored at 5 °C or 17 °C. Storage temperature had a significant effect on the distribution of spermatozoa in seven major kinematic clusters. The effect size of chilling at 5 °C as estimated by Cramer’s V was higher (p < 0.05) in the BTS medium (0.21) compared to AndroStar® Plus (0.11). Spermatozoa extended in Androstar® Plus had higher relative binding capacity compared to sperm in BTS (p < 0.05). Binding indices correlated with the percentage of viable, acrosome-intact (r = 0.62) and motile spermatozoa (r = 0.72, both p < 0.001). The cluster size of sperm with slow, vigorous movement was negatively correlated with sperm-oviduct binding (r = −0.43, p < 0.05). In conclusion, the cluster analysis of sperm kinematics and competitive sperm oviduct binding in vitro present meaningful biological tests to assess novel concepts for hypothermic semen preservation.

Optimization of dissolved oxygen levels in extender prevents development of cryocapacitation like changes, oxidative stress and augments zona binding capacity of crossbred bull spermatozoa

The present study was undertaken to determine the efficacy of partial deoxygenation of extender at constant temperature (35°C) in freezability of crossbred bull semen. The dissolved oxygen (DO) levels were reduced by the use of newly developed technique of nitrogen effervescence at a flow rate of 2-3 bubbles per second. Four different levels of oxygen in semen extender, that is 11.7, 2, 4 and 8 ppm as control (Group-I), Group-II, Group-III and Group-IV, respectively, were used to assess the effect of partial deoxygenation on semen quality parameters. The 4 ppm level of DO resulted in higher (p < 0.05) progressive motility in comparison with non-treated group at post-thaw stage, whereas reduction up to 2 ppm resulted in drastic fall in motility. Oxidative stress status revealed low superoxide dismutase (SOD) and total antioxidant capacity (TAC) in Group-II, whereas higher (p < 0.05) SOD and TAC activities were observed in Group-III in comparison with non-treated group at pre-freeze and post-thaw stages. The sperm-zona binding at 4 ppm level of DO was significantly higher than control group, 2 and 8 ppm levels of DO. In conclusion, reduction of DO in the extender up to 4 ppm reduced oxidative stress and improved in vitro fertility of crossbred bull spermatozoa.

Sperm phenotypic characteristics and oviduct binding ability are altered in breeding bulls with high sperm DNA fragmentation index

In the present study, we standardized an in vitro oviduct explants model for cattle and assessed the oviduct explants binding ability and phenotypic characteristics of spermatozoa obtained from breeding bulls with high- and low-sperm DNA fragmentation index (DFI%). Cryopreserved spermatozoa from Holstein Friesian crossbred breeding bulls (n = 45) with known field fertility were assessed for DFI% and were classified into either high DFI% or low DFI% category. Flow cytometry was used to assess sperm membrane integrity, acrosome reaction status, mitochondrial membrane potential and intracellular calcium concentrations. It was found that spermatozoa from bulls with low DFI% had significantly higher (P < 0.05) membrane integrity, acrosome intactness, and mitochondrial membrane potential. To assess the sperm oviduct binding ability, oviduct explants were prepared by incubating the oviduct cells overnight in TCM-199 medium at 38.5 °C under 5% CO₂. Different sperm concentrations and times of incubation were evaluated and found that 2 million spermatozoa and 1-h incubation yielded high binding index (BI). The BI was also significantly (P < 0.01) higher (>2 times) in the bulls with low-DFI% as compared to high DFI% bulls. The correlation between binding index and DFI% was negative and significant (r = -0.528; P < 0.05). Further, the binding index was positively correlated with conception rate (r = 0.703), intact sperm membrane (r = 0.631) and mitochondrial membrane potential (r = 0.609). It is inferred that sperm phenotypic characteristics and oviduct binding ability are impaired in breeding bulls with high sperm DFI%, which might be associated with low conception rates in these bulls.

Immunological response of fallopian tube epithelial cells to spermatozoa through modulating cytokines and chemokines

BACKGROUND

Spermatozoa interactions with fallopian tubes may influence fertilization. The purpose was to investigate cytokines, chemokines and growth factors expression from human fallopian tube epithelial cells (OE-E6/E7) exposed to spermatozoa.

METHODS

Fresh semen samples were obtained from 10 healthy normozoospermic men. Sperms were prepared and co-cultured with OE-E6/E7. The cell line without spermatozoa was considered as the control group. Afterwards, Expression of 84 cytokines from OE-E6/E7 cell line in the presence and absence of spermatozoa were measured using PCR-array. Quantitative PCR was performed on seven genes to confirm the results of PCR-array analysis. Differentially expressed genes were subjected to www.geneontology.org and www.pantherdb.org to perform GO enrichment and panther pathway analysis. The concentration of IL-8, IL-10, IL-1B and BMP-4 in culture medium were analyzed by ELISA.

RESULTS

Sperm interaction with the epithelial cells resulted in a significant increase in expression of TGF-β2, BMP-4, IL-10, IL-9, and CD40LG markers. Moreover, expression of IL-16, IL-17F, SPP-1, CXCL-13, MSTN, IL-1A, IL-1B, IL-8, BMP-7, CSF-2, CSF-3, VEGF-A, OSM, LTA, TNF, TNFRSF11B, TNFSF11, CCL-11, CCL-20, CCL-24, CCL-3, CCL-8, CX3CL1 and CXCL-9 were considerably reduced in presence of spermatozoa. Panther pathway analysis discovered 3 pathways for upregulated genes including gonadotropin-releasing hormone receptor, TGF-beta and interleukin signaling pathways. Furthermore, 9 pathways were detected for down-regulated genes. Inflammation signaling pathway which is mediated by chemokine and cytokine contains the most number of genes.

CONCLUSION

This study indicates that sperm modifies expression of cytokines, chemokines and growth factors from OE-E6/E7. Moreover, altered genes expression are toward higher survival chance of the spermatozoa.

Progesterone induces porcine sperm release from oviduct glycans in a proteasome-dependent manner

In mammals, the oviduct retains sperm, forming a reservoir from which they are released in synchrony with ovulation. However, the mechanisms underlying sperm release are unclear. Herein, we first examined in greater detail the release of sperm from the oviduct reservoir by sex steroids, and secondly, if the ubiquitin-proteasome system (UPS) mediates this release in vitro. Sperm were allowed to bind to oviductal cells or immobilized oviduct glycans, either bi-SiaLN or a suLeX, and channeled with steroids in the presence or absence of proteasome inhibitors. Previously, we have demonstrated progesterone-induced sperm release from oviduct cells and immobilized glycans in a steroid-specific manner. Herein, we found that the release of sperm from an immobilized oviduct glycan, a six-sialylated branched structure, and from immobilized fibronectin was inhibited by the CatSper blocker NNC 055-0396, akin to the previously reported ability of NNC 055-0396 to inhibit sperm release from another oviduct glycan, sulfated Lewis-X trisaccharide. Thus, CatSper may be required for release of sperm from a variety of adhesion systems. One possible mechanism for sperm release is that glycan receptors on sperm are degraded by proteasomes or shed from the sperm surface by proteasomal degradation. Accordingly, the inhibition of proteasomal degradation blocked sperm release from oviduct cell aggregates both immobilized oviduct glycans as well as fibronectin. In summary, progesterone-induced sperm release requires both active CatSper channels and proteasomal degradation, suggesting that hyperactivation and proteolysis are vital parts of the mechanism by which sperm move from the oviduct reservoir to the site of fertilization.

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.

Spermatozoa produced during winter are superior in terms of phenotypic characteristics and oviduct explants binding ability in the water buffalo (Bubalus bubalis)

Although reduced reproductive efficiency during summer has been well documented in buffaloes, the reason for the same is yet to be understood. The present study was conducted to identify the subtle differences in sperm phenotypic characteristics (motility, membrane integrity, acrosome reaction and lipid peroxidation status), oviduct binding ability and expression of fertility-associated genes (AK 1, ATP5D, CatSper 1, Cytochrome P450 aromatase, SPP1 and PEBP1) between winter and summer seasons in buffaloes. Cryopreserved spermatozoa from 6 Murrah buffalo bulls (3 ejaculates/bull/season) were utilized for the study. Real-time quantitative PCR was performed for assessing the expression patterns of select fertility-associated genes. The proportion of motile and membrane intact spermatozoa was significantly higher (p < .05) in winter as compared to summer ejaculates. The proportion of moribund and lipid peroxidized spermatozoa was significantly lower (p < .05) in winter ejaculates as compared to summer. The sperm-oviduct binding index was significantly lower (p < .01) when spermatozoa from summer ejaculates were used as compared to winter ejaculates. The expression of fertility-associated genes did not differ significantly between the two seasons except for PEPB1; the transcriptional abundance of PEPB1 was significantly (p < .05) lower in summer as compared to winter season. It was inferred that buffalo spermatozoa produced during winter season were superior in terms of cryotolerance, membrane and acrosome integrity, lipid peroxidation status and the ability to bind with oviduct explants.

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.

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.

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.

Periovulatory oviductal fluid decreases sperm protein kinase A activity, tyrosine phosphorylation, and in vitro fertilization in pig

BACKGROUND

Molecules from the female reproductive tract modulate capacitation and function of sperm cells in vivo. These molecules vary in a quantitative and qualitative manner throughout the estrous cycle.

OBJECTIVES

This work evaluates the effect of using various female reproductive fluids on capacitation and fertilization of pig spermatozoa in vitro.

MATERIAL AND METHODS

The effects of culturing spermatozoa in different fluids on the levels of sperm protein kinase A (pPKA), tyrosine phosphorylation, acrosome reaction, and in vitro fertilization (IVF) were evaluated. The fluids tested were as follows: oviductal fluid (OF) from five phases of the estrous cycle, namely early and late follicular (OF-EF, OF-LF), early and late luteal (OF-EL, OF-LL) and periovulatory (pOF), follicular fluid from medium-sized follicles, and secretions of cumulus-oocyte complexes (conditioned medium).

RESULTS

The pPKAs and tyrosine phosphorylation were decreased by OF-EF, OF-LF, OF-EL, and pOF but not by follicular fluid and conditioned medium. OF-EF, OF-LF, and pOF also decreased the sperm acrosome reaction. Moreover, the effect of pOF on pPKAs and tyrosine phosphorylation was reversible. In in vitro fertilization, OF-EF, OF-LF, OF-EL, and pOF reduced the percentage of penetrated oocytes, the mean number of spermatozoa per penetrated oocyte, and increased monospermy.

CONCLUSION

OF from follicular, early luteal, and periovulatory phases of the estrous cycle modulates the sperm protein phosphorylation as well as the acrosome reaction involved in capacitation and increases monospermic fertilization in in vitro fertilization. Our findings suggest that fluids from the female reproductive tract could be used as additives in porcine IVF systems to modulate sperm-oocyte interaction.

Specific trophoblast transcripts transferred by extracellular vesicles affect gene expression in endometrial epithelial cells and may have a role in embryo-maternal crosstalk

Background

Successful establishment of pregnancy hinges on appropriate communication between the embryo and the uterus prior to implantation, but the nature of this communication remains poorly understood. Here, we tested the hypothesis that the endometrium is receptive to embryo-derived signals in the form of RNA.

Methods

We have utilized a non-contact co culture system to simulate the conditions of pre implantation environment of the uterus. We bioorthogonally tagged embryonic RNA and tracked the transferred transcripts to endometrium. Transferred transcripts were separated from endometrial transcripts and sequenced. Changes in endometrial transcripts were quantified using quantitative PCR.

Results

We show that three specific transcripts are transferred to endometrial cells. We subsequently demonstrate a role of extracellular vesicles (EVs) in this process, as EVs obtained from cultured trophoblast spheroids incubated with endometrial cells induced down-regulation of all the three identified transcripts in endometrial cells.

Finally, we show that EVs/nanoparticles captured from conditioned culture media of viable embryos as opposed to degenerating embryos induce ZNF81 down-regulation in endometrial cells, hinting at the functional importance of this intercellular communication.

Conclusion

Ultimately, our findings demonstrate the existence of an RNA-based communication which may be of critical importance for the establishment of pregnancy.

Sperm function in vitro and fertility after antibiotic-free, hypothermic storage of liquid preserved boar semen

The role of antibiotics (AB) in semen extenders as a potential contribution to the global antimicrobial resistance threat is emerging. Here, we establish an AB-free hypothermic preservation strategy for boar semen and investigate its impact on sperm function, microbial load and fertility after artificial insemination (AI). Spermatozoa (12 boars) preserved in AB-free AndroStar Premium extender at 5 °C maintained high motility, membrane integrity, and a low DNA-fragmentation index throughout 72 h storage and results did not significantly differ from controls stored at 17 °C in extender containing AB (p = 0.072). Likewise, kinetic response of spermatoza to the capacitation stimulus bicarbonate during 180 min incubation in Tyrode's medium did not differ from 17 °C-controls. In a competitive sperm oviduct binding assay, binding indices did not differ between semen stored for 72 h AB-free at 5 °C and 17 °C-controls (n = 6 boars). Bacterial load < 103 CFU/ml after 72 h was measured in 88.9% of samples stored at 5 °C AB-free compared to 97.2% in 17 °C-controls (n = 36 semen pools, 23 boars). Fertility traits of 817 females did not differ significantly between the two semen groups (p > 0.05). In conclusion, a hypothermic semen preservation strategy is presented which offers antibiotic-free storage of boar semen doses.

The fate of spermatozoa in the female reproductive tract: A comparative review

The journey that spermatozoa take following deposition in the female tract is a long and perilous one. The barriers they face within the female tract differ depending on whether they are deposited in the vagina or uterus, like spermatozoa of the ram or boar respectively. Comparative studies on the transit of spermatozoa through the ewe and sow tracts serves to highlight similarities, or differences, in the way their sperm-surface properties enable them to overcome these barriers, progress through the tract and fertilise the oocyte. The female environment contributes towards this successful transit by providing a vehicle for sperm transport, aiding the removal of dead spermatozoa and other pathogens and applying strict selection pressures to ensure only those cells with the highest quality reach the site of fertilisation. Understanding the criteria behind these natural barriers helps an understanding of the limitations to fertility associated with preserved spermatozoa, and how in vitro manipulation can alter this complex interaction between spermatozoa and the female environment. Similar mechanisms or surface coat interactions exist in both species, but each has evolved to be used for physiologically disparate functions. Here we briefly describe the sperm surface characteristics of both fresh and frozen-thawed boar and ram spermatozoa and compare how these properties equip them to survive the physical, biochemical and immune interactions within the female reproductive tract.

Efficient isolation, biophysical characterisation and molecular composition of extracellular vesicles secreted by primary and immortalised cells of reproductive origin

Effective communication between the maternal reproductive tract, gametes and the pre-implantation embryo is essential for the successful establishment of pregnancy. Recent studies have recognised extracellular vesicles (EVs) as potent vehicles for intercellular communication, potentially via their transport of microRNAs (miRNAs). The aim of the current investigation was to determine the size, concentration and electrical surface properties (zeta potential) of EVs secreted by; (1) primary cultures of porcine oviductal epithelial cells (POECs) from the isthmus and ampullary regions of the female reproductive tract; (2) Ishikawa and RL95-2 human endometrial epithelial cell line cultures; and (3) the non-reproductive epithelial cell line HEK293T. In addition, this study investigated whether EVs secreted by POECs contained miRNAs. All cell types were cultured in EV-depleted medium for 24 or 48 h. EVs were successfully isolated from conditioned culture media using size exclusion chromatography. Nanoparticle tracking analysis (NTA) was performed to evaluate EV size, concentration and zeta potential. QRT-PCR was performed to quantify the expression of candidate miRNAs (miR-103, let-7a, miR-19a, miR-203, miR-126, miR-19b, RNU44, miR-92, miR-196a, miR-326 and miR-23a). NTA confirmed the presence of EVs with diameters of 50-150 nm in all cell types. EV size distribution was significantly different between cell types after 24 and 48 h of cell culture and the concentration of EVs secreted by POECs and Ishikawa cells was also time dependent. The distribution of EVs with specific electrokinetic potential measurements varied between cell types, indicating that EVs of differing cellular origin have varied membrane components. In addition, EVs secreted by POECs exhibited significantly different time dependant changes in zeta potential. QRT-PCR confirmed the presence of miR-103, let-7a, miR-19a, miR-203, miR-126, and miR-19b in EVs secreted by POECs (C_T ≥ 29). Bioinformatics analysis suggests that these miRNAs are involved in cell proliferation, innate immune responses, apoptosis and cellular migration. In conclusion, reproductive epithelial cells secrete distinct populations of EVs containing miRNAs, which potentially act in intercellular communication in order to modulate the periconception events leading to successful establishment of pregnancy.

Sperm functional attributes and oviduct explant binding capacity differs between bulls with different fertility ratings in the water buffalo (Bubalus bubalis)

We report here the differences in sperm functional attributes and sperm–oviduct binding index in bulls with different field fertility ratings. Cryopreserved spermatozoa from Murrah buffalo bulls (n=9) with different fertility ratings were evaluated for membrane integrity, capacitation status, acrosome intactness and protein tyrosine phosphorylation status. Frozen­–thawed spermatozoa were incubated with oviduct explants for 1h under 5% CO2, 38.5°C with 95% relative humidity and the number of spermatozoa bound to the unit area of oviduct explants (binding index; BI) was assessed using 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolyl-carbocyanine iodide (JC-1) fluorescent staining. The proportion of membrane-intact and acrosome-intact spermatozoa was significantly (P&lt;0.05) higher and the proportion of capacitated spermatozoa was significantly (P&lt;0.05) lower in high-fertile bulls compared with medium- and low-fertile bulls. The relationship between BI and bull fertility was significant and positive (r=0.69; P=0.04). BI was negatively and significantly (r=−0.83; P=0.01) related to membrane-compromised spermatozoa. It was concluded that the sperm–oviduct explant binding index was positively related to (1) the proportion of membrane-intact spermatozoa in a given semen sample and (2) invivo fertility of the buffalo bull, indicating the possibility of developing a fertility prediction tool using a sperm–oviduct explant binding model, once validated on a greater number of bulls.

Bovine sperm sex-selection technology in Japan

BACKGROUND

In Japan, Livestock Improvement Association of Japan started commercially producing sexed bovine semen 10 years ago, and sexed bovine semen is currently used for the artificial insemination (AI) in the farms. In this review, the authors introduce the technology for sperm sexing by flow cytometry, the efforts at commercializing sexed semen in Japan, and recent field data on artificial insemination of the cattle with sexed semen.

METHODS

In the procedures of the flow cytometric method, X-chromosome-bearing sperm and Y-chromosome-bearing sperm were fluorescently stained, separated from each other by analyzing the difference in the DNA content, and cryopreserved. The authors surveyed the conception rates after AI with these sperm and sex ratios of the offspring with the cooperation from livestock associations, AI technicians, and farmers.

MAIN FINDINGS RESULTS

Although AI with sexed semen was associated with lower conception rates in comparison with AI with conventional semen, the accuracy of sex selection using AI with sexed semen was beyond >90%.

CONCLUSION

Sexed semen produced by flow cytometry has the potential to produce offspring of the preferred sex with high accuracy and reliability. Thus, it is expected that sexed semen is used for AI more frequently in the farms.

Progesterone induces the release of bull spermatozoa from oviductal epithelial cells

The mechanism that causes the detachment of spermatozoa from the oviductal reservoir around the time of ovulation remains to be elucidated. Because the cumulus cells of the bovine oocyte are known to secrete progesterone (P4), and P4 has been shown to act upon cation channels of spermatozoa (CatSper) in human spermatozoa, it was hypothesised that P4 could induce hyperactivation due to an influx of extracellular calcium, and this would facilitate detachment of spermatozoa from oviductal epithelial cells. Therefore, this study aimed to investigate the role and mechanism of action of P4 in the release of spermatozoa from bovine oviduct epithelial cells (BOEC). Initial dose–response assessments on sperm hyperactivation determined the optimum concentration of P4 (10 nM), mibefradil (a non-specific Ca2+ channel antagonist; 5µM), NNC 55-0396 dihydrochloride (NNC; a CatSper antagonist; 2µM), mifepristone (a classical and membrane P4 receptor antagonist; 400nM) and AG205 (a membrane P4 receptor antagonist; 10μM). BOEC explants were incubated with frozen–thawed bovine spermatozoa for 30min, following which loosely bound spermatozoa were removed. Two experiments were completed. In Experiment 1, BOECs were treated for 30min with either no treatment, P4, NNC, mibefradil, P4+mibefradil, P4+NNC, P4+mibefradil+NNC or P4+EGTA. In Experiment 2, BOECs were treated for 30min with either no treatment, P4, mifepristone, AG205, mifepristone+AG205, P4+mifepristone, P4+AG205 or P4+mifepristone+AG205. The number of spermatozoa remaining bound per millimetre squared of BOEC explant was determined. Progesterone stimulated the release of bound spermatozoa from BOEC explants, whereas NNC, mibefradil and EGTA inhibited this release. The release of spermatozoa by P4 was inhibited in the presence of both mifepristone and AG205, whereas the combination of both had the greatest inhibitory action on P4 release of spermatozoa. These findings suggest the presence of a P4 membrane receptor on bovine spermatozoa and that P4-induced release of spermatozoa from BOECs is likely mediated by extracellular Ca2+.

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.

The development and functions of multiciliated epithelia

Multiciliated cells are epithelial cells that are in contact with bodily fluids and are required for the proper function of major organs including the brain, the respiratory system and the reproductive tracts. Their multiple motile cilia beat unidirectionally to remove particles of external origin from their surface and/or drive cells or fluids into the lumen of the organs. Multiciliated cells in the brain are produced once, almost exclusively during embryonic development, whereas in respiratory tracts and oviducts they regenerate throughout life. In this Review, we provide a cell-to-organ overview of multiciliated cells and highlight recent studies that have greatly increased our understanding of the mechanisms driving the development and function of these cells in vertebrates. We discuss cell fate determination and differentiation of multiciliated cells, and provide a comprehensive account of their locations and functions in mammals.

Transport, Distribution and Elimination of Mammalian Sperm Following Natural Mating and Insemination

The integrity of transport, distribution and elimination of sperm in the female genital tract plays a pivotal role for successful reproduction in mammals. At coitus, millions or billions of sperm are deposited either into the anterior vagina (human, primates), the cervix (most mammalian species) or the uterus (pig). In most species, the first anatomical barrier is the cervix, where spermatozoa with poor morphology and motility are filtered out by sticking to the cervical mucus. The second anatomical barrier is the uterotubal junction (UTJ) with its tortuous and narrow lumen. Finally, only a few thousand sperm enter the oviduct and less than 100 sperm reach the site of fertilization. As soon as the sperm enter the oviduct, they form a sperm reservoir enabling them to stay vital and maintain fertilizing capacity for 3-4 days (cow, horse) up to several months (bats). After ovulation, mammalian sperm show hyperactivation which allows them to detach from the tubal epithelium and migrate to the site of fertilization. This review will focus on recent insights of sperm transport, sperm storage and sperm-oviduct interaction in mammals which have been gained by live cell imaging in cows and mice under near in vivo conditions. Detailed knowledge of the biology of spermatozoa within the female genital tract creates the basis for new therapeutic concepts for male subfertility and infertility - an essential prerequisite to increase success rates in assisted reproduction.

The porcine sperm reservoir in relation to the function of hyaluronan

The oviduct plays a role in successful animal reproduction not only in spermatozoa and ova transport to the fertilization site but also by affording a microenvironment for fertilization and early embryonic development. The sperm reservoir (SR) is restricted in the uterotubal junction (UTJ) and caudal isthmus. Billions of porcine spermatozoa are distributed to the female reproductive tract during/after insemination, and small amounts of them are stored for about 36–40 hours in the SR, which maintains sperm viability in the pre-ovulation period through its surface epithelium and production of fluid. The SR regulates the release of spermatozoa so that only a small population moves towards the fertilization site (ampulla) to decrease polyspermy. This review attempts to provide information about the structure and function of the porcine SR, its intraluminal content (hyaluronan, HA), and the influences of HA on porcine spermatozoa in vivo. In pigs, the spermatozoa are stored in a mucous-like fluid within the UTJ and caudal isthmus in the pre-ovulation period. The oviduct fluid contains sulfated glycosaminoglycans (GAGs) and non-sulfated GAGs, i.e., HA. It is interesting to note that HA is synthesized by hyaluronan synthase-3 (HAS-3), and its receptor, CD44, is found in the epithelium of the porcine SR site. Additionally, sperm capacitation does not occur in vivo in the SR during the pre- and peri-ovulation periods, but spermatozoa in the SR will attempt to capacitate if exposed to bicarbonate. However, capacitation in the SR will rise in the post-ovulation period, indicating the role of HA in modulating sperm capacitation after ovulation. All data support the understanding that the porcine SR ensures the viability of fertile spermatozoa and maintains the non-capacitated status during the pre-ovulation period. This basic knowledge about the SR is believed to be useful to advance sperm preparation procedures for in vitro fertilization (IVF) and improve the preservation process of porcine semen.

Enhanced fertility prediction of cryopreserved boar spermatozoa using novel sperm function assessment

Due to reduced fertility, cryopreserved semen is seldom used for commercial porcine artificial insemination (AI). Predicting the fertility of individual frozen ejaculates for selection of higher quality semen prior to AI would increase overall success. Our objective was to test novel and traditional laboratory analyses to identify characteristics of cryopreserved spermatozoa that are related to boar fertility. Traditional post-thaw analyses of motility, viability, and acrosome integrity were performed on each ejaculate. In vitro fertilization, cleavage, and blastocyst development were also determined. Finally, spermatozoa-oviduct binding and competitive zona-binding assays were applied to assess sperm adhesion to these two matrices. Fertility of the same ejaculates subjected to laboratory assays was determined for each boar by multi-sire AI and defined as (i) the mean percentage of the litter sired and (ii) the mean number of piglets sired in each litter. Means of each laboratory evaluation were calculated for each boar and those values were applied to multiple linear regression analyses to determine which sperm traits could collectively estimate fertility in the simplest model. The regression model to predict the percent of litter sired by each boar was highly effective (p < 0.001, r(2) = 0.87) and included five traits; acrosome-compromised spermatozoa, percent live spermatozoa (0 and 60 min post-thaw), percent total motility, and the number of zona-bound spermatozoa. A second model to predict the number of piglets sired by boar was also effective (p < 0.05, r(2) = 0.57). These models indicate that the fertility of cryopreserved boar spermatozoa can be predicted effectively by including traditional and novel laboratory assays that consider functions of spermatozoa.

Distinct segment-specific functions of calyculin A-sensitive protein phosphatases in the regulation of cAMP-triggered events in ejaculated bull spermatozoa

Livestock spermatozoa possess more tenacious suppressors of cAMP-triggered events-including capacitation-associated changes-than laboratory animal spermatozoa, leading to flagellar hyperactivation. In order to identify the suppressors, we examined effects of an inhibitor of serine/threonine protein phosphatases (calyculin A) on cAMP-triggered changes in the protein phosphorylation state, and subsequent occurrence of hyperactivation and acrosome reaction in ejaculated bull spermatozoa. Ejaculated spermatozoa were incubated in cAMP-supplemented medium, then assessed for motility, acrosome morphology, and phosphorylated protein localization. The addition of calyculin A greatly enhanced cAMP-triggered protein phosphorylation at serine/threonine and tyrosine residues in the connecting piece and induction of flagellar hyperactivation. Most hyperactivated spermatozoa exhibited extremely asymmetrical bends at the middle piece, which produced intensive twisting or figure-eight movements. In the sperm head, however, cAMP-triggered dephosphorylation of serine/threonine-phosphorylated proteins and subsequent acrosome reaction were abolished by the addition of calyculin A. Based on these results, we suggest that calyculin A-sensitive protein phosphatases in the connecting piece are suppressors of cAMP-triggered events leading to hyperactivation. By contrast, similar protein phosphatases in the sperm head accelerate cAMP-triggered events leading to the acrosome reaction. These findings are consistent with the indication that calyculin A-sensitive protein phosphatases have distinct functions in the regulation of cAMP-triggered events in different regions of ejaculated bull spermatozoa.

Seminal fluid promotes in vitro sperm-oviduct binding in the domestic cat (Felis catus)

From many endangered or threatened species which are expected to profit from assisted reproduction techniques, mainly epididymal sperm of dead or freshly castrated males are available. These sperm had contact to epididymal secretion products but not to seminal fluid components. Notably, products of accessory sex glands have been shown in domestic animals to condition sperm for fertilization, in particular by mediating sperm-oviduct interaction. We report for the first time that motile epididymal sperm from domestic cats are able to bind to fresh oviduct epithelial cell explants from preovulatory females (median [min, max] of 10 [8, 16] and 10 [8, 17] sperm per 0.01 mm(2) explant surface from both isthmic and ampullar regions, respectively). More sperm attach to the explants when epididymal sperm were preincubated for 30 minutes with seminal fluid separated from electroejaculates of mature tomcats (median [min, max] of 17 [13, 25] and 16 [12, 21] sperm per 0.01 mm(2) explant surface from isthmus and ampulla, respectively). The proportion of bound sperm increased from a median of 54% to 62% by seminal fluid treatment. Sperm-oviduct binding could be facilitated by the decelerated sperm motion which was observed in seminal fluid-treated samples or supported by seminal fluid proteins newly attached to the sperm surface. Seminal fluid had no effect on the proportion of sperm with active mitochondria. Extent and pattern of sperm interaction in vitro were independent of explant origin from isthmus or ampulla. Sperm were attached to both cilia and microvilli of the main epithelial cell types present in all explants. In contrast to published sperm-binding studies with porcine and bovine oviduct explants where predominantly the anterior head region of sperm was attached to ciliated cells, the tails of some cat sperm were firmly stuck to the oviduct cell surfaces, whereas the heads were wobbling. Whether this response is a preliminary step toward phagocytosis or a precondition to capacitation and fertilization remains to be determined. In conclusion, treatment of epididymal sperm with seminal fluid or particular protein components should be considered in future investigations for its potential to improve the outcome of artificial insemination in felids.

LewisX-containing glycans on the porcine oviductal epithelium contribute to formation of the sperm reservoir

In many mammals, after semen deposition, a subpopulation of the sperm is transported to the lower oviduct, or isthmus, to form a functional sperm reservoir that provides sperm to fertilize oocytes. The precise molecular interactions that allow formation of this reservoir are unclear. It is proposed that binding of sperm receptors (lectins) to their oviductal cell ligands is accomplished by glycans. Previous results indicated that Lewis trisaccharides are present in glycosphingolipids and O- and N-linked glycans of the porcine isthmus and that Le(X)-containing molecules bind porcine sperm. Immunohistochemistry indicated that the Lewis structures identified by mass spectrometry were, in fact, Lewis X (Le(X)) trisaccharides. These motifs were localized to the luminal border of the isthmus. Assays using fluoresceinated glycans showed that 3-O-sulfated Le(X) (suLe(X)) bound to receptors localized on the head of nearly 60% of uncapacitated boar sperm but that the positional isomer 3-O-sulfo-Le(A) (suLe(A)) bound to <5% of sperm. Sperm also bound preferentially to suLe(X) made insoluble by coupling to beads. Capacitation reduced the ability of suLe(X) to bind sperm to <10%, perhaps helping to explain why sperm are released at capacitation. Pretreatment of oviduct cell aggregates with the Le(X) antibody blocked 57% of sperm binding to isthmic aggregates. Blocking putative receptors on sperm with soluble Le(X) and suLe(X) glycans specifically reduced sperm binding to oviduct cells up to 61%. These results demonstrate that the oviduct isthmus contains Le(X)-related moieties and that sperm binding to these oviduct glycans is necessary and sufficient for forming the sperm reservoir.

Antioxidant effect of rosemary (Rosmarinus officinalis L.) extract in soybean lecithin-based semen extender following freeze-thawing process of ram sperm

The aim of current study was to evaluate effect of rosemary aqueous extract on post-thawed ram sperm quality in a soybean lecithin-based (SL) extender. Ram semen samples were obtained, extended with SL extender and supplemented with 0% (SL-R0), 2% (SL-R2), 4% (SL-R4), 6% (SL-R6), and 8% (SL-R8) rosemary aqueous extract. Following equilibration, the straws were frozen, and then plunged into the liquid nitrogen. After thawing, sperm motility and velocity parameters, plasma membrane functionality, viability, acrosomal and capacitation status were evaluated. Membrane lipid peroxidation was also analyzed through the malondialdehyde (MDA) concentration. Our results showed that SL-R4 and SL-R6 groups resulted in higher (p < 0.05) percentages of total motility, progressive motility, and plasma membrane functionality, as compared with other groups. Highest (p < 0.05) viable and lowest (p < 0.05) dead spermatozoa were observed in SL-R6 group compared to the other groups. The acrosomal and capacitation status were not affected (p > 0.05) by different levels of rosemary aqueous extract. Lower (p < 0.05) MDA concentration has been observed in SL-R4 and SL-R6 groups. The results of this study demonstrate that supplementation of SL extender with rosemary aqueous extract influences post-thawed ram sperm quality in a dose dependent manner.

Effects of spermatozoa-oviductal cell coincubation time and oviductal cell age on spermatozoa-oviduct interactions

The oviduct plays a crucial role in sperm storage, maintenance of sperm viability and sperm transport to the site of fertilisation. The aim of the present study was to investigate the effects of oviductal cell culture passage number, oviductal cell age and spermatozoa-oviduct coincubation times on gene expression in oviductal cells. Immortalised oviductal epithelial cells (OPEC) obtained from two different cell passages (36 and 57) were subcultured three times with and without spermatozoa for 24 h (control group). In a second study, OPEC were cocultured with spermatozoa for different time intervals (0, 4, 12 and 24 h). Expression of adrenomedullin (ADM), heat shock 70 kDa protein 8 (HSPA8) and prostaglandin E synthase (PGES) in OPEC was measured by quantitative polymerase chain reaction. The expression of ADM and HSPA8 was decreased significantly in OPEC cells from Passage 57, particularly in the later subculture group. These effects on HSPA8, but not ADM, expression in OPEC were further altered after coculture with spermatozoa for 24 h. We also demonstrated that spermatozoa-oviduct coculture for 12 and 24 h resulted in significantly higher expression of ADM, HSPA8 and PGES in OPEC. Overall, the data suggest that the OPEC lose some of their properties as a result of oviductal cell aging and that there are spermatozoa-oviduct interactions leading to increased oviductal cell gene expression.

Is the function of the porcine sperm reservoir restricted to the ovulatory period?

The uterotubal junction (UTJ) and caudal isthmus are recognized as a functional pre-ovulatory sperm reservoir (SR). Spermatozoa are released from the SR in a complex and concerted action. However, whether this functionality is restricted only to the ovulatory period is still open to debate. Our study was aimed to analyze the presence of spermatozoa within the UTJ (SR), isthmus (ISTH) and ampulla (AMP) after laparoscopic intrauterine insemination (LIUI) either in the peri- (PERI) or post-ovulatory (POST) period or at mid cycle (MID). Each uterine horn of estrus synchronized gilts (n=12) was inseminated with 20 ml sperm (29.5×10⁶ cells/ml). Oviducts were recovered 7 h after LIUI and separated into the UTJ, ISTH and AMP, and sections were flushed with 10 ml PBS+EDTA solution. After centrifugation, the sperm pellet was evaluated by Čeřovský staining. The median sperm numbers in the PERI, POST and MID groups were 578, 171 and 789 in the UTJ; 545, 233 and 713 in the ISTH; and 496, 280 and 926 in the AMP, respectively, and there were differences between the POST and MID groups (P<0.05) but not between the oviductal sections of each group (P>0.05). Compared with the MID group, the percent of intact sperm cells was higher (P<0.01) in the PERI and POST groups (32.8 vs. 66.4 and 76.8%). Also, the percentages of aberrations in the acrosome and tail were higher (P<0.05) in the MID group. Based on this, it can be assumed that the sperm reservoir is active during different phases of the estrus cycle. However, the mid-cycle oviduct environment considerably impairs sperm cell quality.

Heat-shock protein A8 restores sperm membrane integrity by increasing plasma membrane fluidity

The constitutive 70  kDa heat-shock protein, HSPA8, has previously been shown to contribute to the long-term survival of spermatozoa inside the mammalian female reproductive tract. Here, we show that a recombinant form of HSPA8 rapidly promotes the viability of uncapacitated spermatozoa, the ability of spermatozoa to bind to oviductal epithelial cells, enhances IVF performance, and decreases sperm mitochondrial activity. Fluorescence recovery after photobleaching revealed that the repair of membrane damage is achieved by an almost instantaneous increase in sperm membrane fluidity. The ability of HSPA8 to influence membrane stability and fluidity, as well as its conserved nature among mammalian species, supports the idea that this protein protects sperm survival through membrane repair mechanisms. Free Persian abstract A Persian translation of the abstract is freely available online at http://www.reproduction-online.org/content/147/5/719/suppl/DC1.

Boar sperm tyrosine phosphorylation patterns in the presence of oviductal epithelial cells: in vitro, ex vivo, and in vivo models

Spermatozoa transport through the oviduct is a controlled process that regulates sperm capacitation. A crucial event involved in capacitation is protein tyrosine phosphorylation (TP). This study was undertaken to determine whether similarities exist in protein TP distribution between spermatozoa bound or unbound to oviductal epithelial cells (OEC) in three different conditions: i)in vitro, spermatozoa coincubated with OEC cultures; ii)ex vivo, spermatozoa deposited in porcine oviductal explants from slaughtered animals; iii)in vivo, in which sows were inseminated and the oviduct was recovered. The localization of phosphotyrosine protein was determined using indirect immunofluorescence. The distribution of protein TP was significantly (P<0.05) different between bound and unbound cell populations in all experiments. In sows inseminated close to ovulation, spermatozoa were found mainly in the utero–tubal junction, where spermatozoa exhibited higher proportion of flagellum phosphorylation. Spermatozoa not bound to OEC exhibited high levels of protein phosphorylation (phosphorylated equatorial subsegment and acrosome and/or phosphorylated flagellum) in theex vivoandin vivoexperiments (P<0.05). However, unbound spermatozoa coincubated with OEC inin vitroconditions tended to show intermediate levels of TP (equatorial subsegment with or without phosphorylated flagellum). In spermatozoa bound to OEC, protein TP was located in the equatorial subsegment or presented no phosphorylation (P<0.05). Although sperm capacitation conditionsin vivowere not reproduciblein vitroin our experimental conditions, sperm and OEC binding seemed to be a mechanism for selecting spermatozoa with a low level of TP inin vivo,ex vivo, andin vitroexperiments.

Different migration patterns of sea urchin and mouse sperm revealed by a microfluidic chemotaxis device

Chemotaxis refers to a process whereby cells move up or down a chemical gradient. Sperm chemotaxis is known to be a strategy exploited by marine invertebrates such as sea urchins to reach eggs efficiently in moving water. Less is understood about how or whether chemotaxis is used by mammalian sperm to reach eggs, where fertilization takes place within the confinement of a reproductive tract. In this report, we quantitatively assessed sea urchin and mouse sperm chemotaxis using a recently developed microfluidic model and high-speed imaging. Results demonstrated that sea urchin Arbacia punctulata sperm were chemotactic toward the peptide resact with high chemotactic sensitivity, with an average velocity V_x up the chemical gradient as high as 20% of its average speed (238 μm/s), while mouse sperm displayed no statistically significant chemotactic behavior in progesterone gradients, which had been proposed to guide mammalian sperm toward eggs. This work demonstrates the validity of a microfluidic model for quantitative sperm chemotaxis studies, and reveals a biological insight that chemotaxis up a progesterone gradient may not be a universal strategy for mammalian sperm to reach eggs.