Sperm Interactions from Insemination to Fertilization

Spermatozoa, acts as an external cue and alters the cargo and production of the extracellular vesicles derived from oviductal epithelial cells in vitro

The oviduct provides optimum physiological and biochemical milieu essential for successful fertilization, early embryo development and facilitates functional maturation of spermatozoa. A study has revealed that spermatozoa alters the gene expression in bovine oviductal epithelial cells (BOECs) remotely via bio-active particles, thus acting as a cue to the oviduct prior to their arrival. However, very little attention has been paid to the question of whether spermatozoa could alter the cargo of extracellular vesicles (EVs) derived from BOECs. Therefore, the aim of this study was to investigate the alterations in small non-coding RNAs in EVs cargo derived from BOECs when incubated with spermatozoa in contact and non-contact co-culture models. After 4 h of incubation the EVs were isolated from the conditioned media, followed by small non-coding sequencing of the BOEC derived EVs. Our results revealed that EVs from both co-culture models contained distinct cargo in form of miRNA, fragmented mRNA versus control. The pathway enrichment analysis revealed that EV miRNA from direct co-culture were involved in the biological processes associated with phagocytosis, macroautophagy, placenta development, cellular responses to TNF and FGF. The mRNA fragments also varied within the different groups and mapped to the exonic regions of the transcriptome providing vital insights regarding the changes in cellular transcriptome on the arrival of spermatozoa. The findings of this study suggest that spermatozoa, in contact as well as remotely, alter the EV cargo of female reproductive tract epithelial cells which might be playing an essential role in pre and post-fertilization events.

Vaginal and vestibular electrical resistance as an alternative marker for optimum timing of artificial insemination with liquid-stored and frozen-thawed spermatozoa in sows

Development of a pen-side test to objectively determine the ideal time for artificial insemination (AI) in the sow would save producers time and money. Current processes rely on identification of oestrus via subjective behavioural and physiological markers that are indicative of high blood oestrogen concentrations. This study attempted to use measurements of electrical resistance (ER) in the cervical mucus to pinpoint timing of AI accurately enough to lead to equivalent pregnancy rates as a natural mating. Thirty-six sows were divided into 3 groups and observed for signs of oestrus. Seven sows did not show any oestrus behaviour and were excluded from the study. The remaining 29 sows were inseminated via natural mating and conventional oestrus detection (n = 14), or inseminated artificially with either liquid-stored semen (n = 8) or frozen-thawed semen (n = 7) according to timing indicated from electrical resistance measurements in the vagina and vestibule. Sows that were artificially inseminated on the basis of the electrical resistance readings had a lower pregnancy rate (P = 0.034) and less piglets born alive per litter (P < 0.05) than those that were naturally mated according to a conventional oestrus detection regime. However, the pregnancy rate and total piglets born alive did not differ between the two groups that underwent artificial insemination. Change in electrical resistance in the vagina has the potential to accurately predict ovulation timing, but more work is required to refine the timing of AI in relation to the readings before the technique can be adopted by industry.

Methylprednisolone improves the quality of liquid preserved boar spermatozoa in vitro and reduces polymorphonuclear neutrophil chemotaxis and phagocytosis

After artificial insemination, immune cells such as polymorphonuclear neutrophils will be recruited into the genital tract and induce endometrial inflammation, adversely affecting the spermatozoa. This study aimed to analyze the effect of methylprednisolone (MPS) on boar spermatozoa quality of in vitro liquid preservation and chemotaxis and phagocytosis of polymorphonuclear neutrophils toward boar spermatozoa. Various concentrations of MPS were added to the extender and analyzed for their effects on spermatozoa motility, kinetic parameters, abnormality rate, total antioxidant capacity (T-AOC) levels, H₂O₂ content, mitochondrial membrane potential and acrosome integrity. Testing of MPS on chemotaxis and phagocytosis of polymorphonuclear neutrophils toward spermatozoa induced by lipopolysaccharide (LPS). The results showed that an extender containing 2 × 10^-7 mol/mL MPS was the most effective for preserving boar spermatozoa during in vitro liquid preservation at 17°C. It effectively improved spermatozoa motility, kinetic parameters, T-AOC levels, mitochondrial membrane potential and acrosome integrity, reducing the abnormality rate and H₂O₂ content. Meanwhile, the chemotaxis and phagocytosis of polymorphonuclear neutrophils toward spermatozoa under LPS induction were inhibited in a concentration-dependent manner. In conclusion, MPS has positive implications for improving in vitro liquid preserved boar spermatozoa quality, inhibiting chemotaxis and phagocytosis of polymorphonuclear neutrophils toward spermatozoa.

Sperm storage by females across the animal phyla: A survey on the occurrence and biomolecules involved in sperm storage

Long-term sperm storage by females in various regions of the oviduct is documented across many invertebrate and vertebrate species. Although, many reports emphasize on the histology, histochemistry and ultrastructural features of sperm storage, very little is known about the mechanisms underlying the sperm storage. The current review documents the occurrence of sperm storage by females in a wide array of invertebrate and vertebrate species. This review also provides an insight on the presence of various molecular factors of the sperm storage tubules presumably responsible for the prolonged sperm storage with an emphasis on a model reptile, the Indian garden lizard, Calotes versicolor which contains a unique approximately 55-kDa protein in its utero-vaginal lavage and found to inhibit washed epididymal sperm motility in a concentration and time-dependent manner in a reversible fashion.

Adverse Effects of Single Neutrophil Extracellular Trap-Derived Components on Bovine Sperm Function

Neutrophil extracellular traps (NETs) play a key role in fertilisation by eliminating microorganisms and entrapping spermatozoa in the female reproductive tract (FRT). The deleterious effects of NETs on spermatozoa have been previously described; however, individual exposure to NET-derived components in bull spermatozoa has not been explored. The aim of this study was to evaluate the effects of the main NET-derived proteins, histone 2A (H2A), neutrophil elastase (ELA), myeloperoxidase (MPO), pentraxin 3 (PTX), cathepsin G (Cat-G), and cathelicidin LL37 (LL-37), at concentrations of 1, 10, and 30 μg/mL, on sperm parameters. Sperm were selected and incubated with different NET-derived proteins for 4 h. Membrane and acrosome integrity, lipoperoxidation, and membrane phospholipid disorders were also evaluated. Bovine polymorphonuclear neutrophil (PMN)/sperm co-cultures were evaluated by scanning electron microscopy and immunofluorescence. All NET-derived proteins/enzymes resulted in a reduction in membrane integrity, acrosome integrity, and lipoperoxidation at a concentration of 30 μg/mL. Bovine PMN/sperm co-cultures showed marked NET formation in the second hour. In conclusion, all NET-derived proteins/enzymes exerted cytotoxic effects on bull sperm, and this effect should be considered in future investigations on the uterine microenvironment and the advancement of spermatozoa in the FRT.

Zearalenone interferes with the sperm-triggered inflammation in the bovine uterus in vitro: Negative impact on sperm motility and survival

Zearalenone (ZEN)-contaminated diets induce detrimental effects on the bovine reproduction. Recently, we reported that active sperm induce pro-inflammatory responses in bovine endometrial epithelial cells (BEECs) in vitro. This study aimed to investigate the impact of presence of ZEN on the sperm-uterine crosstalk in vitro. BEECs monolayers were stimulated by ZEN (10, 100, and 1000 ng/mL) for 0, 3, 6, 12, or 24 h and gene expressions were analyzed by real-time PCR. Moreover, BEECs were pre-exposed to ZEN (10, 100, and 1000 ng/mL) for 24 h then, co-incubated with sperm for 6 h. Conditioned media (CM) from a sperm-BEECs co-culture, after pre-exposure to ZEN, were harvested and exploited to challenge either polymorphonuclear cells (PMNs) or sperm. Both PMNs phagocytic activity toward sperm and sperm motility parameters were then assessed. Results showed that ZEN alone induced pro-inflammatory responses in BEECs through the induction of mRNA expressions of pro-inflammatory cytokines (TNFA and IL1B) and PGES1 at different time points. Pre-exposure of BEECs to ZEN, amplified the sperm-triggered upregulation of pro-inflammatory cytokines (TNFA and IL1B) and chemokine IL8 mRNA abundance in BEECs. Sperm-BEECs conditioned media, primed by ZEN, stimulated the PMNs phagocytosis for sperm whereas suppressed sperm motility parameters. Taken together, these findings indicate that the presence of ZEN augments the pro-inflammatory cascade triggered by sperm in BEECs, provokes PMNs phagocytosis for sperm, and reduces sperm motility parameters. Such immunological reactions may create a hostile environment for sperm competence and survival in the bovine uterus, thus impair fertility.

Role of reproductive fluids and extracellular vesicles in embryo&#x2013;maternal interaction during early pregnancy in cattle

The coordinated interaction between the developing embryo and the maternal reproductive tract is essential for the establishment and maintenance of pregnancy in mammals. An early cross-talk is established between the oviduct/uterus and the gametes and embryo. This dialogue will shape the microenvironment in which gamete transport, fertilisation, and early embryonic development occur. Due to the small size of the gametes and the early embryo relative to the volume of the oviductal and uterine lumina, collection of tissue and fluid adjacent to these cells is challenging in cattle. Thus, the combination of in vivo and in vitro models seems to be the most appropriate approach to better understand this fine dialogue. In this respect, the aim of this review is to summarise the recent findings in relation to gamete/embryo-maternal interaction during the pre-elongation period.

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.

Interaction of Mycobacterium avium subsp. paratuberculosis with bovine sperm

Mycobacterium avium subsp. paratuberculosis (MAP) is responsible for Paratuberculosis mainly affecting domestic ruminants. The interaction between MAP and sperm and/or germ cells has not yet been established, however the adherence between MAP and the host cell surface is associated to the 85 complex proteins that bind to the host cell's fibronectin. Therefore, this study aimed to evaluate the binding of MAP to bovine sperm and to verify changes in these cells by the presence of MAP before and after sperm cryopreservation. Polyclonal antibodies to MAP 85 complex proteins were produced and utilized in the analyzes. Two Nelore bulls were used for semen collection and MAP dilutions (10³-10⁸ CFU/mL) were inoculated in the samples; sperm motility and vigor were evaluated using light microscopy at different times before and after cryopreservation and in the presence and absence of the antibodies 85A and 85B. Interaction of MAP and sperm, interaction of MAP and sperm in the presence of Ab 85A and in the presence of Ab 85B were analyzed by scanning electron microscopy. The viability of MAP after sperm cryopreservation were evaluated by plating the samples after thawing. It was observed that sperm in the presence of MAP shows a decrease in motility and vigor, and that the higher the MAP concentration, the lower the sperm performance. It was possible to determine the viability of MAP after cryopreservation in samples of higher concentrations, which demonstrates the potential of transmission of this pathogen through artificial insemination. The interaction of MAP with bovine sperm occurs mainly in the midpiece and may be linked to the proteins 85A and 85B present in the MAP membrane.

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.

Bovine Sperm Sexing Alters Sperm Morphokinetics and Subsequent Early Embryonic Development

In artificial insemination the use of sex-sorted bovine sperm results in reduced conception, the causes of which are only partly understood. Therefore, we set out to investigate the effects of sexing on bovine sperm function and early embryonic development. Computer-assisted semen analysis (CASA) of sperm of the same bulls (n = 5), before and after sexing, demonstrated significantly reduced fast (A) and slow (B) progressively motile sperm (p < 0.05) after sexing. Sexed-sperm also revealed significantly less hyperactivated sperm (p < 0.05). As shown by time-lapse videomicroscopy of in vitro produced embryos (n = 360), embryos derived from sexed-sperm displayed significantly increased incidences of arrest at the 4-cell stage (p < 0.05). The relative risk for shrinkage/fusion of blastomeres with subsequent lysis was 1.71 times higher in the embryos derived from sexed-sperm as compared to conventional embryos (p < 0.05) resulting in significantly reduced blastocyst rates (p < 0.001). The relative risk for cleavage was 2.36 times lower in the embryos derived from sex-sorted sperm (p < 0.001). Additionally, sexed-sperm-derived embryos showed reduced survival times (hazard ratio HR = 1.54, p < 0.001) which were bull dependent (p < 0.001). However, the percentage of apoptotic cells was similar to conventional embryos. Furthermore, embryos derived from sexed-sperm were found to reach developmental stages at similar timings as conventional embryos. Our results suggest that reduced conception rates after sexing are due to altered sperm morphokinetics, decreasing the chance of sperm to reach and fertilise the oocyte, and aberrant early embryonic development.

Studies of gel with immobilized semen by intrauterine endoscopy post-artificial insemination

An extended lifespan of spermatozoa following artificial insemination (AI) can make the timing of insemination less critical, as previously demonstrated with immobilized spermatozoa that are gradually released from an alginate gel. The purpose was to examine the in vivo dissolution of SpermVital (SV) alginate gel over time by endoscopy and secondly to assess spermatozoa quality after incubation of the gel. In vivo endoscopy showed SV gel in the uterus 3, 6, 20 and 24 hr after AI, demonstrating the potential release of spermatozoa to the uterus during this period. In utero ex vivo incubation of the semen demonstrated that high motility and viability of sperm cells was sustained following overnight incubation.

Salpingitis Impairs Bovine Tubal Function and Sperm-Oviduct Interaction

Salpingitis is a common cause for subfertility and infertility both in humans and animals. However, the effects of salpingitis on tubal function and reproductive success are largely unknown. Therefore we set out to investigate the effects of inflammation on sperm and oocyte transport and gameto-maternal interaction in the oviduct using the bovine as a model. For this purpose, oviducts revealing mild (n = 45), moderate (n = 55) and severe (n = 45) inflammation were obtained from cows immediately after slaughter and investigated by live cell imaging, histochemistry and scanning electron microscopy. Our studies showed that endometritis was always correlated with salpingitis. Moderate and severe inflammation caused a significant increase in the thickness of tubal folds (p < 0.05). Severe inflammation was characterized by luminal accumulations of mucus and glycoproteins, increased apoptosis, loss of tight junctions and shedding of tubal epithelial cells. The mean ciliary beat frequency (CBF) in the ampulla was significantly reduced as compared to the controls (p < 0.05). The higher the grade of inflammation, the lower was the CBF (p < 0.001). In severe inflammation, spermatozoa were stuck in mucus resulting in decreased sperm motility. Our results imply that tubal inflammation impairs proper tubal function and leads to reduced sperm fertilizing capacity.

Seminal plasma mitigates the adverse effect of uterine fluid on boar spermatozoa

After natural or artificial insemination, spermatozoa start their journey within the uterus to reach the site of fertilization, but only few of them attain this goal. Part of this spermatozoa loss happens in the uterus, in which uterine fluid (UF) seems to be involved. It is known from other species that UF provokes damage to spermatozoa, which is avoided when seminal plasma (SP) is present. Therefore, the aim of the present study was to evaluate the effect of UF on the quality of ejaculated (previously contacted with SP) and epididymal (without previous contact with SP) boar spermatozoa analyzing motility, kinetic parameters, viability and acrosome integrity in the presence or absence of SP over time. Three experimental groups were evaluated in each source of spermatozoa (ejaculated and epididymal): 1) Control: spermatozoa with 20% of SP; 2) UF: spermatozoa with 20% of UF; and 3) UF-SP: spermatozoa with 20% of SP and 20% of UF. Total and progressive motility, kinetic parameters (VCL, VSL, VAP, LIN, STR, WOB, and BCF), viability and acrosome damage were analyzed at 15, 60, 120 and 180 min after incubation. Total and progressive motility decreased when ejaculated spermatozoa were incubated in UF in contrast to control and UF-SP groups (p < 0.0007), with no differences between control and UF-SP. The VCL decreased in the UF group compared to the control and UF-SP groups in ejaculated spermatozoa (p = 0.0002). The VSL, VAP, LIN and STR kinetic parameters were greater when ejaculated spermatozoa were incubated in the UF-SP group than in the UF group (all: p ≤ 0.02). Acrosome damage increased in ejaculated and epididymal spermatozoa incubated in the UF group compared to the control and UF-SP groups (both: p < 0.0001). Also, the viability of epididymal spermatozoa decreased in the UF group, while it did not change in the control and UF-SP groups (p = 0.0004). The rest of the parameters in either ejaculated or epididymal spermatozoa did not differ between experimental groups, except for WOB when epididymal spermatozoa were used (UF-SP higher than the control group, with UF being similar for both; p = 0.03). In conclusion, both ejaculated and epididymal spermatozoa are affected by UF, suggesting a negative effect on their quality. This negative effect is reduced by the presence of SP, improving the spermatozoa functionality, preserving motility, viability and acrosome integrity.

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.

TLR2/4 signaling pathway mediates sperm-induced inflammation in bovine endometrial epithelial cells in vitro

We have recently shown that sperm attachment to bovine endometrial epithelial cells (BEECs) triggers uterine local innate immunity with induction of a pro-inflammatory response in vitro, however details of the mechanism remain unknown. Here, we investigated the involvement of Toll-like receptor 2/4 (TLR2/4) pathway in mediating sperm-BEECs inflammatory process. Immunohistochemistry of the uterine tissue revealed that TLR2 and TLR4 proteins were present in the luminal and glandular epithelia of bovine endometrium. Moreover, BEECs monolayers were treated with TLR2 agonist (Pam; 0, 10, 100, and 1000 ng/ml) or TLR4 agonist (LPS; 0, 0.1, 1, and 10 ng/ml) for 0, 1, 3, or 6 h, followed by evaluating mRNA expression of the pro-inflammatory genes (TNFA, IL-1B, IL-8, and PGES) in BEECs using a real-time PCR. Both Pam and LPS treatments showed a dose-dependent stimulation of mRNA expression of the pro-inflammatory genes. To elucidate the functional role of TLR2/4 in sperm-BEECs interaction, BEECs monolayers were incubated with either TLR2 antagonist or TLR4 antibody for 2 h prior to the co-culture with sperm for 3 h. Importantly, pre-incubation of BEECs with TLR2 antagonist or TLR4 antibody prevented the stimulatory effect of sperm on the transcription of pro-inflammatory genes in BEECs. Furthermore, sperm increased the phosphorylation levels of TLR2/4 downstream targets (p38MAPK and JNK) in BEECs within 1 h of the co-culture. Treatment of BEECs with TLR2 antagonist prior to sperm addition inhibited JNK phosphorylation, while TLR4 antibody inhibited the phosphorylation of both p38MAPK and JNK. In conclusion, the present in vitro findings strongly suggest that bovine endometrial epithelial cells respond to sperm via TLR2/4 signal transduction.

An application of higher order multivariate cumulants in modelling of myoelectrical activity of porcine uterus during early pregnancy

The analysis of the uterine contraction have become a general practice in an effort to improve the clinical management of uterine contractions during pregnancy and labour in human beings. The fluctuations in uterine activity may occur without affecting progress of gestation, however the painful and fashion contractions may be the first threat of miscarriage. While pigs were considered as an referential preclinical model, the computational modelling of spontaneous myoelectrical activity of complex systems of porcine myometrium in peri-fertilization period has been proposed. The higher order statistic, multivariate cumulants and Joint Skewness Band Selection method, have been applied to study the dependence structure of electromyographic (EMG) signal with an effective EMG feature. Than the model of recognition of multivariate, myoelectricaly changes according to crucial stages for successful fertilization and early pregnancy maintenance has been estimated. We found that considering together time and frequency features of EMG signal was extremely non-Gaussian distributed and the higher order multivariate statistics such as cumulants, have to be used to determine the pattern of myoelectrical activity in reproductive tract. We confirmed the expectance that the probabilistic model changes on a daily base. We demonstrated the changes in proposed model at the crucial time points of in peri-fertilization period. We speculate the activity of the middle of uterine horn and the power (minimum and maximum) and pauses between myoelectrical burst features are essential for the functional role of uterine contractility in peri-fertilization period.

Endoscopy-mediated intratubal insemination in the cow - Development of a novel minimally invasive AI technique

Conventionally inseminated spermatozoa suffer a dramatic reduction in numbers during their long journey until fertilization. In addition sperm survival seems to be strongly affected by the reconstitution of the female reproductive tract in the post partum period. The purpose of this study was to develop a novel AI technique for cattle that allows the deposition of spermatozoa directly into the ampulla in the immediate vicinity of the fertilization site. This new reproductive biotechnique was investigated with focus on semen origin, sperm dosage, semen preparation and time of insemination. Finally, a first practical application was carried out by inseminating superovulated heifers with sex-sorted semen. In total, 49 Simmental heifers were used for 65 intratubal inseminations (ITI) with single ovulation and 8 ITIs after superovulation, respectively. Insemination into the oviduct was performed under epidural anesthesia via transvaginal endoscopy using a curved glass capillary loaded with semen. Two days later the oviduct and the adjacent uterine horn were endoscopically flushed and embryos or unfertilized oocytes were collected for determination of fertilization success. Across all experimental groups, tubal insemination successfully resulted in the collection of embryos; however, first tubal AI attempts and ITIs close to ovulation led to low recovery rates. In total, 109 complexes were flushed from ITIs in superstimulated heifers (n = 8) using sex sorted semen, of which 24 (22%) were at the embryo stage. In conclusion, it was shown that intratubal insemination can be successfully used for semen deposition, thus bypassing the lower female genital tract. Factors such as time of insemination, semen processing and semen quantity for superovulatory use should be further investigated.

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.

Sperm Storage in the Female Reproductive Tract

The capacity for sperm storage within the female reproductive tract occurs widely across all groups of vertebrate species and is exceptionally well developed in some reptiles (maximum duration seven years) and fishes (maximum duration >1 year). Although there are many reports on both the occurrence of female sperm storage in diverse species and its adaptive benefits, few studies have been directed toward explaining the mechanisms involved. In this article we review recent findings in birds and mammals in an effort to develop hypotheses that could be translated into research applications in animal breeding technologies. There are pockets of evidence to suggest that the local epithelial cells, sometimes arranged as sperm storage tubules, can respond to spermatozoa by producing heat shock proteins as well as providing an environment rich in antioxidants. Moreover, the local immune system seems to tolerate the arrival of spermatozoa, while retaining the ability to combat the arrival of infectious microorganisms.

Outstanding questions concerning sperm-epithelial binding in the mammalian oviduct

Preovulatory binding of viable spermatozoa in the oviduct isthmus is widely accepted as a preliminary to fertilization, but details of physiological events associated with epithelial binding and release from binding are themselves little understood. Important questions include the potential number, distribution and stability of such sites in the caudal isthmus, whether multiple molecular forms of binding exist within a single-mated individual, and whether some sites are more favourable than others for the maintenance of preovulatory sperm viability. Also to be resolved is whether spermatozoa interact with the first available binding sites in the isthmus, whether spermatozoa from second or subsequent matings bind closer to the site of fertilization, and whether the first spermatozoa entering the oviduct are those that will be released first with impending ovulation. Ideally, future research needs to focus on a fertilizing spermatozoon monitored in vivo and not on spermatozoa destined to remain on or in the zona pellucida or in the lower reaches of the oviduct.

Cross-talk between free and bound spermatozoa to modulate initial sperm:egg ratios at the site of fertilization in the mammalian oviduct

This essay proposes that highly localized communication between free and bound spermatozoa in the caudal portion of the oviduct acts to regulate the numbers detaching from the epithelium and progressing to the site of fertilization close to the time of ovulation. Low initial sperm:egg ratios are essential for monospermic fertilization. Liberation of surface macromolecules and metabolic prompting from activated spermatozoa, together with altered patterns of sperm movement and dynamic differences in intracellular Ca(2+) ion status between neighboring sperm cells, would influence the progressive release of spermatozoa from the reservoir in the oviduct isthmus. Different intensities of preovulatory epithelial binding, reflecting a range of states in the sperm surface membranes and associated proteins, would provide a further explanation for a chronologically staggered periovulatory detachment of spermatozoa. Intimate sperm-sperm interactions within the confines of the oviduct isthmus offer a sensitive means of fine-tuning the vanguard of competent male gametes reaching the isthmo-ampullary junction.

Polymorphonuclear neutrophil profile in genital discharge vis-à-vis pregnancy outcome in crossbred cows: effect of varying cow fertility and insemination from different bulls

The study investigated the relationship between count and/or viability percentage of polymorphonuclear neutrophil(s) (PMN) in genital discharge and pregnancy outcome during 180 estrous periods in 163 normal and repeat breeder. The relationship was also evaluated as a response to AI by three of the most frequently used bulls. The estrous periods leading to pregnancy in the normal cows were considered fertile (FE; n=66), whereas others with pregnancy failure were considered non-fertile in the remaining normal (NFE; n=86) and the entire group of repeat breeder cows (RB; n=28) cows. Another set of reproductively healthy cows, not inseminated, were also studied (C; n=10). The PMN characteristics were investigated in 3μl fraction of cervical discharge, aspirated initially at mid-estrus in C/pre-AI in the inseminated cows and subsequently 18 to 24h later. The first sample did not reveal PMN in all the cows. However, there was a variable PMN response in the second sample. The PMN count of 9.3±1.9 in the C group was least and significantly less than the FE and NFE groups. A count of 90.9±8.4 in the FE group was greater (P<0.01) than 60.9±5.1 in the NFE and 36.7±5.2 in the RB group. The PMN viability percentage among the four groups was similar (range: 61.3±6.5% to 70.1±6.4%). The average PMN count in response to AI with all the three bulls, JY-426 (47 inseminations), JY-450 (23 inseminations) and HF-5 (33 inseminations), was less in the NFE than the FE group, the differences being marked in NFE compared with FE for JY-450 (51.8±12.4 compared with 88.0±17.4; P=0.10) and HF-5 (38.5±10.1 compared with 92.9±26.5; P<0.05). It is concluded that a greater PMN count post-AI could favor pregnancy outcome. Further, PMN migration is likely to be controlled by maternal factors rather than semen characteristics.

Storage and release of spermatozoa from the pre-uterine tube reservoir

In mammals, after coitus a small number of spermatozoa enter the uterine tube and following attachment to uterine tube epithelium are arrested in a non-capacitated state until peri-ovulatory signalling induces their detachment. Whilst awaiting release low numbers of spermatozoa continually detach from the epithelium and the uterine tube reservoir risks depletion. There is evidence of attachment of spermatozoa to uterine epithelium in several species which might form a potential pre-uterine tube reservoir. In this study we demonstrate that: (1) dog spermatozoa attach to uterine epithelium and maintain flagellar activity, (2) in non-capacitating conditions spermatozoa progressively detach with a variety of motility characteristics, (3) attachment is not influenced by epithelial changes occurring around ovulation, (4) attachment to uterine epithelium slows capacitation, (5) capacitated spermatozoa have reduced ability to attach to uterine epithelium, (6) under capacitating conditions increased numbers of spermatozoa detach and exhibit transitional and hyperactive motility which differ to those seen in non-capacitating conditions, (7) detachment of spermatozoa and motility changes can be induced by post-ovulation but not pre-ovulation uterine tube flush fluid and by components of follicular fluid and solubilised zona pellucida, (8) prolonged culture does not change the nature of the progressive detachment seen in non-capacitating conditions nor the potential for increased detachment in capacitating conditions. We postulate that in some species binding of spermatozoa to uterine epithelium is an important component of the transport of spermatozoa. Before ovulation low numbers of spermatozoa continually detach, including those which are non-capacitated with fast forward progressive motility allowing the re-population of the uterine tube, whilst around the time of ovulation, signalling from as-yet unknown factors associated with follicular fluid, oocytes and uterine tube secretion promotes the detachment of large numbers of capacitated spermatozoa with hyperactive motility that may contribute to the fertilising pool.

Effects of heat stress on the well-being, fertility, and hatchability of chickens in the northern Guinea savannah zone of Nigeria: a review

The paper examines heat stress and its adverse effects as a hindrance to profitable poultry production in the tropics, with emphasis on the Northern Guinea Savannah zone of Nigeria. It elucidates the general negative effects of heat stress on physiological parameters of domestic chickens, and the specific impact of the stress on reproduction in the tropics. The deleterious effects are expressed in poor poultry well-being and reproductive performance. It is concluded that measures aimed at alleviating heat stress in domestic chickens must be adopted in order to enhance reproductive and, consequently, efficiency of modern poultry production in the tropics.

Practical applications of sperm selection techniques as a tool for improving reproductive efficiency

Modern biotechnologies are used extensively in the animal breeding industry today. Therefore, it is essential that sperm handling procedures do not modulate the normal physiological mechanisms occurring in the female reproductive tract. In this paper, the different selection mechanisms occurring in vivo are described briefly, together with their relevance to artificial insemination, followed by a detailed description of the different selection processes used in reproductive biotechnologies. These selection methods included fractionated semen collection, cryopreservation, biomimetic sperm selection, selection based on hyaluronic acid binding, and last, but not least, sperm sex selection. Biomimetic sperm selection for AI or for cryopreservation could improve pregnancy rates and help to reverse the decline in fertility seen in several domestic species over the recent decades. Similarly, selection for hyaluronic acid binding sites may enable the most mature spermatozoa to be selected for IVF or ICSI.

Expression of progesterone receptor in the utero-tubal junction after intra-uterine and deep intra-uterine insemination in sows

The aim of this study was to investigate the expression of progesterone receptor (PR) in the utero-tubal junction (UTJ) of sows at 24 h after intra-uterine insemination (IUI) and deep intra-uterine insemination (DIUI) compared with conventional artificial insemination (AI) in pigs. Fifteen multiparous sows were used: AI (n = 5), IUI (n = 5) and DIUI (n = 5). The sows were inseminated with a single dose of diluted semen during the second oestrus after weaning at 6-8 h prior to ovulation (AI: 3000 × 10(6) spermatozoa, IUI: 1000 × 10(6) spermatozoa and DIUI: 150 × 10(6) spermatozoa). The UTJ was collected and subject to immunohistochemical staining using avidin-biotin immunoperoxidase technique with mouse monoclonal antibody to PR. In the oviductal part of the UTJ, the intensity of PR in the tunica muscularis and the proportion of PR-positive cells in the surface epithelium after DIUI were lower than AI (p < 0.05). The intensity and the proportion of PR-positive cells between AI and IUI in all compartments of the UTJ did not differ significantly (p > 0.05). When comparing between tissue compartments, prominent staining was observed in the muscular layer of the UTJ. It could be concluded that the expression of PR in the UTJ prior to fertilization after DIUI with a reduced number of spermatozoa was lower than that after AI. This might influence sperm transportation and the fertilization process.

Fertility after post-cervical artificial insemination with cryopreserved sperm from boar ejaculates of good and poor freezability

This study compared the field fertility outcomes in frozen-thawed (FT) sperm from boar ejaculates with different freezability (good, GFE/poor, PFE) while testing the reliability of the post-cervical artificial insemination (post-CAI) in FT sperm. The assay was conducted over eight months with 86 weaned sows being inseminated by post-CAI. Every ejaculate in a total of 26 from 15 Piétrain boars was divided into a refrigerated semen portion (FS; control treatment) and a cryopreserved portion (FT sperm), and the ejaculates were in turn classified as GFE or PFE in function of the sperm progressive motility and viability at 240min post-thaw. As result, one of four possible treatments was randomly given to each sow: FS-GFE, FS-PFE, FT-GFE and FT-PFE. The number of pregnant and farrowing sows in FT-GFE did not significantly differ from those of FS control treatments. Contrarily, the probabilities of pregnancy were two times lower after inseminations with FT-PFE (P<0.05) compared to FT-GFE, which indicates that ejaculates with high post-thaw sperm progressive motility and viability are more likely to result in pregnancies than those with poor in vitro sperm function. There were no differences in litter size or the risk of backflow among treatments. Further trials are required to determine the optimal volume and concentration of FT sperm in post-CAI to obtain a more reliable method for farmers interested in cryopreserved sperm.