Improving porcine in vitro fertilization output by simulating the oviductal environment

Sperm functionality is differentially regulated by porcine oviductal extracellular vesicles from the distinct phases of the estrous cycle

Context Extracellular vesicles (EVs) derived from the oviductal fluid (oEVs) play a critical role in various reproductive processes, including sperm capacitation, fertilisation, and early embryo development. Aims To characterise porcine oEVs (poEVs) from different stages of the estrous cycle (late follicular, LF; early luteal, EL; mid luteal, ML; late luteal, LL) and investigate their impact on sperm functionality. Methods poEVs were isolated, characterised, and labelled to assess their binding to boar spermatozoa. The effects of poEVs on sperm motility, viability, acrosomal status, protein kinase A phosphorylation (pPKAs), tyrosine phosphorylation (Tyr-P), and in in vitro fertility were analysed. Key results poEVs were observed as round or cup-shaped membrane-surrounded vesicles. Statistical analysis showed that poEVs did not significantly differ in size, quantity, or protein concentration among phases of the estrous cycle. However, LF poEVs demonstrated a higher affinity for binding to sperm. Treatment with EL, ML, and LL poEVs resulted in a decrease in sperm progressive motility and total motility. Moreover, pPKA levels were reduced in presence of LF, EL, and ML poEVs, while Tyr-P levels did not differ between groups. LF poEVs also reduced sperm penetration rate and the number of spermatozoa per penetrated oocyte (P Conclusions poEVs from different stages of the estrous cycle play a modulatory role in sperm functionality by interacting with spermatozoa, affecting motility and capacitation, and participating in sperm-oocyte interaction. Implications The differential effects of LF and LL poEVs suggest the potential use of poEVs as additives in IVF systems to regulate sperm-oocyte interaction.

The role of highly dispersed silica nanoparticles in the realization of the effects of granulosa on the maturation and fertilization competence of <i>Sus scrofa domesticus</i> oocytes

Reproductive technologies are some of the key directions in the context of the need to preserve and select highly productive farmed animals in terms of economically useful traits. Improvements of the existing models of the in vitro oocyte maturation system help to solve the problem of low yield of porcine embryos at the final stages of preimplantation development. In the present study, a model of culture medium for gametes (NCSU-23 with 10 % homologous follicular fluid, 10 IU hCG and 10 IU eCG) modernized by the addition of 1·106 granulosa cells (GCs) per ml and 0.001 % of highly dispersed silica nanoparticles (HDSn) is proposed for use in the IVM and IVF technology of donor porcine oocytes. Analysis of the oocyte chromatin status by the Tarkowsky method and assessment of the level of destructive changes in chromatin (apoptosis, pyknosis) revealed a significant percentage increase in matured oocytes and a decrease in the proportion of granulosa cells with degenerated chromatin when using the original culture system. The positive effects of a joint addition of GCs and HDSn to the maturation system have made it possible to increase the indicators of the meiotic maturation and fertilization of oocytes. Optimal results of developmental competence of oocytes were achieved with the joint use of GCs and HDSn in the maturation system (the proportion of matured cells reached 89 %, the level of oocytes with chromosome degeneration was 12 %, 39 % of embryos reached the final stage of preimplantation development). The positive effect of HDSn on oocyte fertilization was accompanied by an abrupt decrease in destructive processes in GCs during culture in the presence of HDSn. The level of somatic cells with pyknotic nuclei was 32 % and the level of apoptosis (TUNELtest), 21 %, compared with the control (43 and 31 %, p <0.01, respectively). Thus, a high efficiency of the porcine oocyte maturation system in the joint culture of gametes with GCs and HDSn was revealed. It makes it possible to recommend a model of this culture medium at the IVM of female gametes of Sus scrofa domesticus for improving the quality of donor oocytes used in cell and genetic engineering.

Production of Pigs From Porcine Embryos Generated in vitro

Generating porcine embryos in vitro is a critical process for creating genetically modified pigs as agricultural and biomedical models; however, these embryo technologies have been scarcely applied by the swine industry. Currently, the primary issue with in vitro-produced porcine embryos is low pregnancy rate after transfer and small litter size, which may be exasperated by micromanipulation procedures. Thus, in this review, we discuss improvements that have been made to the in vitro porcine embryo production system to increase the number of live piglets per pregnancy as well as abnormalities in the embryos and piglets that may arise from in vitro culture and manipulation techniques. Furthermore, we examine areas related to embryo production and transfer where improvements are warranted that will have direct applications for increasing pregnancy rate after transfer and the number of live born piglets per litter.

Nitric oxide-targeted protein phosphorylation during human sperm capacitation

Among many other molecules, nitric oxide insures the correct progress of sperm capacitation by mediating phosphorylation events. For a more comprehensive understanding of how this happens, we capacitated human spermatozoa from healthy men in the presence/absence of S-Nitrosoglutathione, a nitric oxide donor, two nitric oxide synthase inhibitors, N^G-Nitro-l-arginine Methyl Ester Hydrochloride and Aminoguanidine Hemisulfate salt and, finally, with/without l-Arginine, the substrate for nitric oxide synthesis, and/or human follicular fluid. When analyzing the phosphorylation of protein kinase A substrates and tyrosine residues, we particularly observed how the inhibition of nitric oxide synthesis affects certain protein bands (~ 110, ~ 87, ~ 75 and ~ 62 kD) by lowering their phosphorylation degree, even when spermatozoa were incubated with l-Arginine and/or follicular fluid. Mass spectrometry analysis identified 29 proteins in these species, related to: spermatogenesis, binding to the zona pellucida, energy and metabolism, stress response, motility and structural organization, signaling and protein turnover. Significant changes in the phosphorylation degree of specific proteins could impair their biological activity and result in severe fertility-related phenotypes. These findings provide a deeper understanding of nitric oxide’s role in the capacitation process, and consequently, future studies in infertile patients should determine how nitric oxide mediates phosphorylation events in the species here described.

Practical Approaches for Knock-Out Gene Editing in Pigs

Pigs are an important resource for meat production and serve as a model for human diseases. Due to their physiological and anatomical similarities to humans, these animals can recapitulate symptoms of human diseases, becoming an effective model for biomedical research. Although, in the past pig have not been widely used partially because of the difficulty in genetic modification; nowadays, with the new revolutionary technology of programmable nucleases, and fundamentally of the CRISPR-Cas9 systems, it is possible for the first time to precisely modify the porcine genome as never before. To this purpose, it is necessary to introduce the system into early stage zygotes or to edit cells followed by somatic cell nuclear transfer. In this review, several strategies for pig knock-out gene editing, using the CRISPR-Cas9 system, will be summarized, as well as genotyping methods and different delivery techniques to introduce these tools into the embryos. Finally, the best approaches to produce homogeneous, biallelic edited animals will be discussed.

In vivo measurement of pH and CO2 levels in the uterus of sows through the estrous cycle and after insemination

The pH-CO₂-HCO₃^- system is a ubiquitous biological regulator with important functional implications for reproduction. Knowledge of the physiological values of its components is relevant for reproductive biology and the optimization of Assisted Reproductive Technologies (ARTs). However, in situ measurements of these parameters in the uterus are scarce or null. This study describes a non-invasive method for in situ time-lapse recording of pH and CO₂ within the uterus of non-anesthetized sows. Animals were at three different reproductive conditions, estrous with no insemination and two hours after insemination, and diestrous. From pH and CO₂ data, HCO₃^- concentration was estimated. The non-invasive approach to the porcine uterus with novel optical probes allowed the obtaining of in situ physiological values of pH, CO₂, and HCO₃^-. Variable oscillatory patterns of pH, CO₂ and HCO₃^- were found independently of the estrous condition. Insemination did not immediately change the levels of uterine pH, CO₂ (%) and HCO₃^- concentration, but all the values were affected by the estrous cycle decreasing significantly at diestrous condition. This study contributes to a better understanding of the in vivo regulation of the pH-CO₂-HCO₃^- system in the uterus and may help to optimize the protocols of sperm treatment for in vitro fertilization.

Selection of Boar Sperm by Reproductive Biofluids as Chemoattractants

Simple Summary

Both in natural breeding and some assisted reproduction technologies, spermatozoa are deposited into the uterus. The journey the spermatozoa must take from the place of semen deposition to the fertilization site is long, hostile, and selective of the best spermatozoa. For the fertilization to succeed, spermatozoa are guided by chemical stimuli (chemoattractants) to the fertilization site, mainly secreted by the oocyte, cumulus cells, and other substances poured into the oviduct in the periovulatory period. This work studied some sources of chemotactic factors and their action on spermatozoa functionality in vitro, including the fertility. A special chemotactic chamber for spermatozoa selection was designed which consists of two wells communicated by a tube. The spermatozoa are deposited in well A, and the chemoattractants in well B. This study focuses on the use of follicular fluid (FF), periovulatory oviductal fluid (pOF), conditioned medium from the in vitro maturation of oocytes (CM), and progesterone (P4) as chemoattractants to sperm. The chemotactic potential of these substances is also investigated as related to their action on CatSper which is a calcium channel in the spermatozoa known to be sensitive to chemoattractants and essential for motility.

Abstract

Chemotaxis is a spermatozoa guidance mechanism demonstrated in vitro in several mammalian species including porcine. This work focused on follicular fluid (FF), periovulatory oviductal fluid (pOF), the medium surrounding oocytes during in vitro maturation (conditioned medium; CM), progesterone (P4), and the combination of those biofluids (Σ) as chemotactic agents and modulators of spermatozoa fertility in vitro. A chemotaxis chamber was designed consisting of two independent wells, A and B, connected by a tube. The spermatozoa are deposited in well A, and the chemoattractants in well B. The concentrations of biofluids that attracted a higher proportion of spermatozoa to well B were 0.25% FF, 0.25% OF, 0.06% CM, 10 pM P4 and 0.25% of a combination of biofluids (Σ2), which attracted between 3.3 and 12.3% of spermatozoa (p < 0.05). The motility of spermatozoa recovered in well B was determined and the chemotactic potential when the sperm calcium channel CatSper was inhibited, which significantly reduced the % of spermatozoa attracted (p < 0.05). Regarding the in vitro fertility, the spermatozoa attracted by FF produced higher rates of penetration of oocytes and development of expanded blastocysts. In conclusion, porcine reproductive biofluids show an in vitro chemotactic effect on spermatozoa and modulate their fertilizing potential.

Boar sperm incubation with reduced glutathione (GSH) differentially modulates protein tyrosine phosphorylation patterns and reorganization of calcium in sperm, in vitro fertilization, and embryo development depending on concentrations

The sperm in the female's reproductive tract undergo changes to fertilize the oocyte (sperm capacitation). These changes are regulated by redox system. However, some assisted reproductive technologies require sperm capacitation under in vitro conditions, though this increases the generation of ROS. Therefore, the aim of this study was to evaluate the effect of GSH as an antioxidant agent during the capacitation of boar sperm [evaluated by calcium compartmentalization, tyrosine phosphorylation (Tyr-P), motility, viability, and acrosomal integrity], in vitro fertilization (evaluated by penetration, monospermy, and efficiency %), and later embryo development (evaluated by cleavage and blastocyst rates, total number of cells per blastocyst and blastocyst diameter). Four experimental groups with different GSH concentrations (0-control, 0.5, 1, and 5 mM) were formed. When 1-GSH was added to the medium, the percentage of capacitated sperm increased after 4 h of incubation; the localization of Tyr-P was modified at 1 h and 4 h of incubation depending on the GSH concentration. Percentages of total and progressive sperm motility also increased at 4 h of incubation, but only in the 5-GSH group compared to control. Viability, acrosomal integrity, and general Tyr-P (Western blot) not differ among the experimental groups. The addition of GSH during gamete interaction increased penetration, monospermy, and efficiency rates in the 1-GSH group compared to the others. However, the effect of GSH was not observed in cleavage and blastocyst rates compared to the control. In conclusion, adding GSH modulates sperm capacitation (by means of calcium compartmentalization and tyrosine phosphorilation pattern) depending on its concentration, and improves IVF output at 1-GSH during gamete interaction.

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

BACKGROUND

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

OBJECTIVES

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

MATERIAL AND METHODS

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

RESULTS

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

CONCLUSION

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

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.

Reproductive technologies in swine

This chapter highlights the importance of reproductive technologies that are applied to porcine breeds. Nowadays the porcine industry, part of a high technological and specialized sector, offers high-quality protein food. The development of the swine industry is founded in the development of breeding/genetics, nutrition, animal husbandry, and animal health. The implementation of reproductive technologies in swine has conducted to levels of productivity never reached before. In addition, the pig is becoming an important species for biomedicine. The generation of pig models for human disease, xenotransplantation, or production of therapeutic proteins for human medicine has in fact generated a growing field of interest.

Regulation of boar sperm functionality by the nitric oxide synthase/nitric oxide system

Purpose

Nitric oxide (NO) is a free radical synthesized mainly by nitric oxide synthases (NOSs). NO regulates many aspects in sperm physiology in different species. However, in vitro studies investigating NOS distribution, and how NO influences sperm capacitation and fertilization (IVF) in porcine, have been lacking. Therefore, our study aimed to clarify these aspects.

Methods

Two main experiments were conducted: (i) boar spermatozoa were capacitated in the presence/absence of S-nitrosoglutathione (GSNO), a NO donor, and two NOS inhibitors, N^G-nitro-L-arginine methyl ester hydrochloride (L-NAME) and aminoguanidine hemisulfate salt (AG), and (ii) IVF was performed in the presence or not of these supplements, but neither the oocytes nor the sperm were previously incubated in the supplemented media.

Results

Our results suggest that NOS distribution could be connected to pathways which lead to capacitation. Treatments showed significant differences after 30 min of incubation, compared to time zero in almost all motility parameters (P < 0.05). When NOSs were inhibited, three protein kinase A (PKA) substrates (~ 75, ~ 55, and ~50 kDa) showed lower phosphorylation levels between treatments (P < 0.05). No differences were observed in total tyrosine phosphorylation levels evaluated by Western blotting nor in situ. The percentage of acrosome-reacted sperm and phosphatidylserine translocation was significantly lower with L-NAME. Both inhibitors reduced sperm intracellular calcium concentration and IVF parameters, but L-NAME impaired sperm ability to penetrate denuded oocytes.

Conclusions

These findings point out to the importance of both sperm and cumulus-oocyte-derived NO in the IVF outcome in porcine.

Electronic supplementary material

The online version of this article (10.1007/s10815-019-01526-6) contains supplementary material, which is available to authorized users.

Implications of boar sperm kinematics and rheotaxis for fertility after preservation

Artificial insemination (AI) is the single most important assisted reproductive technique devised to facilitate the genetic improvement of livestock. In the swine industry, it has broadly replaced natural service over the last number of decades which has been made possible by the high pregnancy rates and litter sizes obtainable with semen extended, up to, and sometimes beyond 5 d. Central to achieving good reproductive performance is the ability of boar studs to monitor semen quality, the basis of which has long been the assessment of sperm motility by subjective and, more recently, by more objective computerised systems. In this review, the literature on the relationship between sperm motility and kinematic parameters and field fertility is summarised. We discuss how this relationship is dependent on factors such as the viscosity of the media and the use of standard operating procedures. Emerging evidence is discussed regarding the importance of sperm rheotaxis and thigmotaxis as long-distance sperm guidance mechanisms, which enable motile functional spermatozoa to avoid the backflow of fluid, mucus and semen from the sow's uterus in the hours post AI, facilitating the establishment of sperm reservoirs in the oviducts. The literature on the use of microfluidics in studying sperm rheotaxis in vitro is also summarised, and we discuss how these systems, when combined with techniques such as lensless microscopy, have the potential to offer more physiological assessments of the swimming patterns of boar spermatozoa. Finally, possible future avenues of further investigation are proposed.

Pig in vitro fertilization: Where are we and where do we go?

The pig is an important livestock animal. Biotechnological interest in this species has increased due to its use, among others, in the generation of transgenic animals for use in biomedicine based on its greater physiological proximity to the human species than other large domestic animals. This development has paralleled an improvement in Assisted Reproduction Techniques (ART) used for this species. However, the ability to generate animals from embryos produced entirely in vitro is still limited and a wide margin for improvement remains. Here we review the procedures, additives, and devices used during pig in vitro fertilization (IVF), focusing on the main points of each step that have offered the best results in terms of increased efficiency of the system. The lack of standardized protocols and consensus on the parameters to be assessed makes it difficult to compare results across different studies, but some conclusions are drawn from the literature. We anticipate that new physiological protocols will advance the field of swine IVF, including induction of prefertilization ZP hardening with oviductal fluid, sperm preparation by swim-up method, increased viscosity through the addition of inert molecules or reproductive biofluids, and the incorporation of 3D devices. Here we also reflect on the need to expand the variables on which the efficiency of pig IVF is based, providing new parameters that should be considered to supply more objective and quantitative assessment of IVF additives and protocols.

Identification of Rabbit Oviductal Fluid Proteins Involved in Pre-Fertilization Processes by Quantitative Proteomics

Oviductal fluid (ODF) proteins modulate and support reproductive processes in the oviduct. In the present study, proteins involved in the biological events that precede fertilization have been identified in the rabbit ODF proteome, isolated from the ampulla and isthmus of the oviduct at different time points within 8 h after intrauterine insemination. A workflow is used that integrates lectin affinity capture with stable-isotope dimethyl labeling prior to nanoLC-MS/MS analysis. In total, over 400 ODF proteins, including 214 lectin enriched glycoproteins, are identified and quantified. Selected data are validated by Western blot analysis. Spatiotemporal alterations in the abundance of ODF proteins in response to insemination are detected by global analysis. A subset of 63 potentially biologically relevant ODF proteins is identified, including extracellular matrix components, chaperones, oxidoreductases, and immunity proteins. Functional enrichment analysis reveals an altered peptidase regulator activity upon insemination. In addition to protein identification and abundance changes, N-glycopeptide analysis further identifies 281 glycosites on 199 proteins. Taken together, these results show, for the first time, the evolving oviductal milieu early upon insemination. The identified proteins are likely those that modulate in vitro processes, including spermatozoa function.