The coculture of in vitro produced porcine embryos and oviductal epithelial cells improves blastocyst formation and modify embryo quality

The efficiency of in vitro embryo production in mammals is influenced by variables associated with culture conditions during maturation, fertilization, and embryonic development. The embryos obtained often exhibit low quality due to suboptimal in vitro culture conditions compared to the in vivo environment. Co-culturing gametes and embryos with somatic cells has been developed to enhance in vitro culture conditions. This study aimed to assess the impact of coculturing in vitro-produced porcine embryos with porcine oviductal epithelial cells (POEC) on embryo development and quality. Firstly, a pure culture of POEC suitable for coculture systems was established. The epithelial origin of the cells was confirmed by the expression of E-cadherin and cytokeratin. The expression pattern of hormone receptors aligned with the diestrous oviduct, and POEC also secreted oviductal glycoprotein type 1 (OVGP-1). Secondly, POEC from passage 1 (POEC-1) were used to coculture with in vitro-produced porcine embryos. A successful coculture system was established without the addition of fetal bovine serum as a supplement. Coculturing POEC-1 in monolayers with in vitro-produced porcine embryos during the initial two days of culture enhanced the percentage of blastocysts and their hatching. Although the coculture did not alter the number of cells in the blastocysts or apoptosis assessed by TUNEL, it significantly reduced reactive oxygen species (ROS) levels in cleaved porcine embryos. This study represents the first report evaluating the quality of porcine embryos produced by IVF in coculture systems and assessing ROS levels in cleaved porcine embryos obtained by IVF.

How sperm protects itself: A journey in the female reproductive system

Sperm must pass a complex route in the female reproductive tract (FRT) to reach the fertilization site and join the oocyte. Thus, it should employ several mechanisms to survive against the female immune system, fertilize the oocyte, and successfully transmit paternal genes to the next generation. In addition to self-protection, sperm may be involved in the immune tolerance to the developing embryo and regulating the FRT for embryo implantation and subsequent pregnancy. Hence, this review intends to summarize the mechanisms that protect sperm in the FRT: including immunomodulatory factors that are carried by seminal plasma, cell-to-cell and molecular interaction of sperm with epithelial and immune cells of the FRT, high regulated secretions of inflammatory factors such as cytokines, chemokines, and growth factors, inducing immune tolerance to paternal antigens, and specialized expression of cell receptors and binding proteins. In most of these events sperm induces the FRT to protect itself by modulating immune responses for its own benefit. However, not all sperm in the semen are able to trigger the survival mechanisms and only high-quality sperm will overcome this challenge. A clear understanding of the molecular mechanisms that maintain sperm viability and function in the FRT can lead to new knowledge about infertility etiology and a new approach in assisted reproductive technologies for the preparation and selection of the best sperm based on the criteria that physiologically happen in-vivo.

Extracellular vesicles-coupled miRNAs from oviduct and uterus modulate signaling pathways related to lipid metabolism and bovine early embryo development

BACKGROUND

Extracellular vesicles (EVs) present in oviductal (OF) and uterine fluid (UF) have been shown to enhance bovine embryo quality during in vitro culture by reducing lipid contents and modulating lipid metabolism-related genes (LMGs), while also influencing cell proliferation, suggesting their involvement on the regulation of different biological pathways. The regulation of signaling pathways related to cell differentiation, proliferation, and metabolism is crucial for early embryo development and can determine the success or failure of the pregnancy. Bioactive molecules within EVs in maternal reproductive fluids, such as microRNAs (miRNAs), may contribute to this regulatory process as they modulate gene expression through post-transcriptional mechanisms.

RESULTS

From the 20 differentially expressed miRNAs, 19 up-regulated in UF-EVs (bta-miR-134, bta-miR-151-3p, bta-miR-155, bta-miR-188, bta-miR-181b, bta-miR-181d, bta-miR-224, bta-miR-23b-3p, bta-miR-24-3p, bta-miR-27a-3p, bta-miR-29a, bta-miR-324, bta-miR-326, bta-miR-345-3p, bta-miR-410, bta-miR-652, bta-miR-677, bta-miR-873 and bta-miR-708) and one (bta-miR-148b) in OF-EVs. These miRNAs were predicted to modulate several pathways such as Wnt, Hippo, MAPK, and lipid metabolism and degradation. Differences in miRNAs found in OF-EVs from the early luteal phase and UF-EVs from mid-luteal phase may reflect different environments to meet the changing needs of the embryo. Additionally, miRNAs may be involved, particularly in the uterus, in the regulation of embryo lipid metabolism, immune system, and implantation. This study evaluated miRNA cargo in OF-EVs from the early luteal phase and UF-EVs from the mid-luteal phase, coinciding with embryo transit within oviduct and uterus in vivo, and its possible influence on LMGs and signaling pathways crucial for early embryo development. A total of 333 miRNAs were detected, with 11 exclusive to OF, 59 to UF, and 263 were common between both groups.

CONCLUSIONS

Our study suggests that miRNAs within OF- and UF-EVs could modulate bovine embryo development and quality, providing insights into the intricate maternal-embryonic communication that might be involved in modulating lipid metabolism, immune response, and implantation during early pregnancy.

Three-dimensional particle streak velocimetry based on optical coherence tomography for assessing preimplantation embryo movement in mouse oviduct in vivo

The mammalian oviduct (or fallopian tube) is a tubular organ hosting reproductive events leading to pregnancy. Dynamic 3D imaging of the mouse oviduct with optical coherence tomography (OCT) has recently emerged as a promising approach to study the hidden processes vital to elucidate the role of oviduct in mammalian reproduction and reproductive disorders. In particular, with an intravital window, in vivo OCT imaging is a powerful solution to studying how the oviduct transports preimplantation embryos towards the uterus for pregnancy, a long-standing question that is critical for uncovering the functional cause of tubal ectopic pregnancy. However, simultaneously tracking embryo movement and acquiring large-field-of-view images of oviduct activity in 3D has been challenging due to the generally limited volumetric imaging rate of OCT. A lack of OCT-based 3D velocimetry method for large, sparse particles acts as a technical hurdle for analyzing the mechanistic process of the embryo transport. Here, we report a new particle streak velocimetry method to address this hurdle. The method relies on the 3D streak of a moving particle formed during the acquisition of a single OCT volume, where double B-scans are acquired at each B-scan location to resolve ambiguity in assessing the movement of particle. We validated this method with the gold-standard, direct volumetric particle tracking in a flow phantom, and we demonstrated its in vivo applications for simultaneous velocimetry of embryos and imaging of oviduct. This work sets the stage for quantitative understanding of the oviduct transport function in vivo, and the method fills in a gap in OCT-based velocimetry, providing the potential to enable new applications in 3D flow imaging.

Deciphering the role of female reproductive tract microbiome in reproductive health: a review

Relevant studies increasingly indicate that female reproductive health is confronted with substantial challenges. Emerging research has revealed that the microbiome interacts with the anatomy, histology, and immunity of the female reproductive tract, which are the cornerstone of maintaining female reproductive health and preventing adverse pregnancy outcomes. Currently, the precise mechanisms underlying their interaction and impact on physiological functions of the reproductive tract remain elusive, constituting a prominent area of investigation within the field of female reproductive tract microecology. From this new perspective, we explore the mechanisms of interactions between the microbiome and the anatomy, histology, and immunity of the female reproductive tract, factors that affect the composition of the microbiome in the female reproductive tract, as well as personalized medicine approaches in managing female reproductive tract health based on the microbiome. This study highlights the pivotal role of the female reproductive tract microbiome in maintaining reproductive health and influencing the occurrence of reproductive tract diseases. These findings support the exploration of innovative approaches for the prevention, monitoring and treatment of female reproductive tract diseases based on the microbiome.

Morphology of the immune cells in the wall of the human uterine tube and their possible impact on reproduction-uterine tube as a possible immune privileged organ

The uterine tube, as well as other parts of the upper female reproductive system, is immunologically unique in its requirements for tolerance to allogenic sperm and semi-allogenic embryos, yet responds to an array of sexually transmitted pathogens. To understand this dichotomy, there is a need to understand the functional morphology of immune cells in the wall of the uterine tube. Thus, we reviewed scientific literature regarding immune cells and the human uterine tube by using the scientific databases. The human uterine tube has a diverse population of immunocompetent cells representing both the innate and adaptive immune systems. We describe in detail the possible roles of cells of the mononuclear phagocyte system (macrophages and dendritic cells), T and B lymphocytes, natural killer cells, neutrophils and mast cells in association with the reproductive functions of uterine tubes. We are also discussing about the possible "immune privilege" of the uterine tube, as another mechanism to tolerate sperm and embryo without eliciting an inflammatory immune response. In uterine tube is not present an anatomical blood-tissue barrier between antigens and circulation. However, the immune cells of the uterine tube probably represent a type of "immunological barrier," which probably includes the uterine tube among the immunologically privileged organs. Understanding how immune cells in the female reproductive tract play roles in reproduction is essential to understand not only the mechanisms of gamete transport and fertilization as well as embryo transport through the uterine tube, but also in improving results from assisted reproduction.

Lab-on-chip (LoC) application for quality sperm selection: An undelivered promise?

Quality sperm selection is essential to ensure the effectiveness of assisted reproductive techniques (ART). However, the methods employed for sperm selection in ART often yield suboptimal outcomes, contributing to lower success rates. In recent years, microfluidic devices have emerged as a promising avenue for investigating the natural swimming behavior of spermatozoa and developing innovative approaches for quality sperm selection. Despite their potential, the commercial translation of microfluidic-based technologies has remained limited. This comprehensive review aims to critically evaluate the inherent potential of lab-on-chip technology in unraveling sophisticated mechanisms encompassing rheotaxis, thermotaxis, and chemotaxis. By reviewing the current state-of-the-art associated with microfluidic engineering and the swimming of spermatozoa, the goal is to shed light on the multifaceted factors that have impeded the broader commercialization of these cutting-edge technologies and recommend a commercial that can surmount the prevailing constraints. Furthermore, this scholarly exploration seeks to enlighten and actively engage reproductive clinicians in the profound potential and implications of microfluidic methodologies within the context of human infertility.

Bovine oviductal organoids: a multi-omics approach to capture the cellular and extracellular molecular response of the oviduct to heat stress

BACKGROUND

The mammalian oviduct is a complex, fibromuscular organ known for its role in orchestrating a series of timely and dynamic changes to suitably support early embryogenesis. Climate change-induced heat stress (HS) is one of the largest single stressors compromising reproductive function in humans and farm animals via systemic changes in the redox status of the maternal environment, adversely affecting fertilization and early embryonic development. Oviductal organoids represent a unique 3-dimensional, biomimetic model to study the physiology of the oviduct and its subsequent impact on embryo development under various environmental conditions.

RESULTS

Our study is the first to demonstrate an innovative approach to understanding the cascade of molecular changes sustained by bovine oviductal organoids under HS and the subsequent maternal signals harnessed within their secreted extracellular vesicles (EVs). Transcriptomic analysis of oviductal organoids exposed to HS revealed 2,570 differentially expressed genes (1,222 up- and 1,348 downregulated), while EV-coupled miRNome analysis disclosed 18 miRNAs with significant differential expression (12 up- and 6 downregulated) in EVs from thermally stressed organoids compared to EVs released from organoids cultured under thermoneutral conditions. Genes activated in oviductal organoids in response to thermal stress, include: COX1, ACTB, CST6, TPT1, and HSPB1, while miR-1246, miR-148a, miR21-5p, miR-451, and miR-92a represent the top highly abundant EV-coupled miRNAs released in response to HS. Pathway analysis of genes enriched in organoids exposed to thermal stress showed the enrichment of endocrine resistance, cellular senescence, and notch signaling pathways. Similarly, EV-coupled miRNAs released from thermally stressed organoids showed their potential regulation of genes involved in cellular senescence, p53 signaling, and TGF-beta signaling pathways.

CONCLUSIONS

In conclusion, the cellular and extracellular response of bovine oviductal organoids to in vitro HS conditions reveal the prospective impact of environmental HS on the physiology of the oviduct and the probable subsequent impacts on oocyte fertilization and early embryo development. Future studies elucidating the potential impact of HS-associated EVs from oviductal organoids on oocyte fertilization and preimplantation embryo development, would justify the use of an organoid model to optimally understand the oviduct-embryo communication under suboptimal environments.

Advancing bovine in vitro fertilization through 3D printing: the effect of the 3D printed materials

Nowadays there is an increasing demand for assisted reproductive technologies due to the growth of infertility problems. Naturally, fertilization occurs in the oviduct, where the oviductal epithelial cells (OECs) secrete many molecules that affect the embryo's metabolism and protect it from oxidative stress. When the OECs are grown in 3D culture systems, they maintain a great part of their functional characteristics, making them an excellent model for in vitro fertilization (IVF) studies. In this work, we aimed to evaluate the suitability of different 3D-printing processes in conjunction with the corresponding set of commercially available biomaterials: extrusion-based processing using polylactic acid (PLA) and polycaprolactone (PCL) and stereolithography or digital-light processing using polyethylene-glycol-diacrylate (PEGDA) with different stiffness (PEGDA500, PEGDA200, PEGDA PhotoInk). All the 3D-printed scaffolds were used to support IVF process in a bovine embryo assay. Following fertilization, embryo development and quality were assessed in terms of cleavage, blastocyst rate at days 7 and 8, total cell number (TCN), inner cell mass/trophectoderm ratio (ICN/TE), and apoptotic cell ratio (ACR). We found a detrimental effect on cleavage and blastocyst rates when the IVF was performed on any medium conditioned by most of the materials available for digital-light processing (PEGDA200, PEGDA500). The observed negative effect could be possibly due to some leaked compound used to print and stabilize the scaffolds, which was not so evident however with PEGDA PhotoInk. On the other hand, all the extrusion-based processable materials did not cause any detrimental effect on cleavage or blastocyst rates. The principal component analysis reveals that embryos produced in presence of 3D-printed scaffolds produced via extrusion exhibit the highest similarity with the control embryos considering cleavage, blastocyst rates, TCN, ICN/TE and ACR per embryo. Conversely, all the photo-cross linkable materials or medium conditioned by PLA, lead to the highest dissimilarities. Since the use of PCL scaffolds, as well as its conditioned medium, bring to embryos that are more similar to the control group. Our results suggest that extrusion-based 3D printing of PCL could be the best option to be used for new IVF devices, possibly including the support of OECs, to enhance bovine embryo development.

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.

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.

Acquisition of fertilization competence in guinea pig spermatozoa under different capacitation protocols

Guinea pig in vitro fertilization (IVF) are poorly developed due to the limited accessibility to oocytes and the lack of an efficient method of sperm capacitation. Thus, we aimed to evaluate different capacitation protocols that we validated through sperm analysis and using heterologous (He) IVF with zona-intact bovine oocytes. Spermatozoa of guinea pigs were collected and processed separately by 4 different protocols: A) Spermatozoa were obtained by flushing the lumen of one cauda epididymis and incubated in a minimal culture medium (MCM); B) One epididymis was placed in a prewarmed of M2 medium and gently minced with fine scissors. Spermatozoa were incubated in a modified human tubal fluid medium (HTF). In both protocols, the spermatozoa were capacitated at 37 °C under an atmosphere of 5% CO2 for 2 h. In the protocols C and D, the spermatozoa were collected by flushing the lumen of the cauda epididymis and selected by commercial density gradient Bovipure® (Nidacon Laboratories AB, Göthenborg, Sweden), according to the manufacturer's instructions. Then for Protocol C) spermatozoa were incubated in MCM medium supplemented with 10 mg/mL heparin (MCM-Hep); while for Protocol D) spermatozoa were incubated in FERT medium supplemented 10 mg/mL heparin (FERT-Hep). Incubation of C and D protocols were performed at 38.5 °C under an atmosphere of 5% CO₂ for 2 h. Capacitation protocols C and D showed a higher percentage of viability, total and hyperactive-like motility, and acrosome reaction compared to protocols A and B. For this reason, protocols C and D were used for further He-IVF analysis. Guinea pig sperm and matured zona-intact bovine oocytes were co-incubated at 5% CO₂ and 38.5 °C. Sperm-oocyte interaction was assessed at 2.5 h post-insemination (hpi) and pronuclear formation (PrF) were evaluated at 18, 20, 22, 24 and 26 hpi, while the cleavage rate was evaluated at 48 hpi. In protocol D, PrF was significantly higher than in protocol C (P ≤ 0.05) at every time point evaluated. Also, the cleavage rate at 48 hpi was higher (P ≤ 0.05) in He-IVF protocol D (69.8 ± 1.7%) compared to He-IVF protocol C (49.1 ± 1.1%). In conclusion, we determined the most adequate sperm capacitation conditions for guinea pig that allow zona-intact bovine oocyte penetration and lead to hybrid embryo formation, suggesting that these conditions could be optimal to develop IVF in guinea pigs.

Dynamics of gametes and embryos in the oviduct: what can in vivo imaging reveal?

In brief

In vivo imaging of gametes and embryos in the oviduct enables new studies of the native processes that lead to fertilization and pregnancy. This review article discusses recent advancements in the in vivo imaging methods and insights which contribute to understanding the oviductal function.

Abstract

Understanding the physiological dynamics of gametes and embryos in the fallopian tube (oviduct) has significant implications for managing reproductive disorders and improving assisted reproductive technologies. Recent advancements in imaging of the mouse oviduct in vivo uncovered fascinating dynamics of gametes and embryos in their native states. These new imaging approaches and observations are bringing exciting momentum to uncover the otherwise-hidden processes orchestrating fertilization and pregnancy. For mechanistic investigations, in vivo imaging in genetic mouse models enables dynamic phenotyping of gene functions in the reproductive process. Here, we review these imaging methods, discuss insights recently revealed by in vivo imaging, and comment on emerging directions, aiming to stimulate new in vivo studies of reproductive dynamics.

Bull spermatozoa selected by thermotaxis exhibit high DNA integrity, specific head morphometry, and improve ICSI outcome

BACKGROUND

Sperm migration by thermotaxis is a guidance mechanism that operates along the oviduct and it has proved to be a valid method for selecting spermatozoa with low DNA fragmentation (SDF) in mice, humans, and stallions. This study aimed to analyse if bull spermatozoa could be selected by thermotaxis and to assess their quality in terms of SDF as well as determine the presence of a specific sperm subpopulation based on sperm morphometry and assess their fertilizing capacity by ICSI.

METHODS

We used frozen-thawed sperm from 6 bulls and sperm selection by thermotaxis was performed with TALP medium supplemented with 25 mmol/L of HEPES and 5 mmol/L of caffeine. In these conditions, sperm selection was achieved, obtaining a net thermotaxis of 3.6%. Subsequently, we analysed the SDF of the migrated and not-migrated spermatozoa using the neutral COMET assay, and we evaluated the size of the sperm head using Hemacolor® staining with Motic Images Plus 3 software. Additionally, migrated and not-migrated spermatozoa by thermotaxis were used to fertilize bovine in vitro matured (IVM) oocytes by ICSI, a very inefficient procedure in cattle that is only successful when the oocyte is artificially activated.

RESULTS

The results showed lower SDF (χ², P < 0.001, 13.3% reduction, n = 8) and lower head size parameters (length and width, P < 0.01; and perimeter and area, P < 0.001; n = 4) in those spermatozoa migrated in comparison to those not-migrated. The distribution of sperm subpopulations structure varied between groups, highlighting cluster 2, characterized by spermatozoa with small head size, and high ellipticity and elongated heads, as the most abundant in the thermotaxis migrated group. When performed ICSI (without oocyte artificial activation) with the thermotactic sperm, the blastocyst rate was 32.2% ± 9.3% in the group microinjected with the thermotactic spermatozoa vs. 8.3% ± 7.8% in the group of not-migrated sperm (χ², P < 0.05).

CONCLUSION

Our results showed that bull sperm selection by thermotaxis has a much higher DNA integrity, small and elongated head size parameters, and different sperm subpopulation structure than the not-selected spermatozoa. Additionally, we evidenced that thermotactic spermatozoa improve ICSI success rates.

Conservation Biology and Reproduction in a Time of Developmental Plasticity

The objective of this review is to ask whether, and how, principles in conservation biology may need to be revisited in light of new knowledge about the power of epigenetics to alter developmental pathways. Importantly, conservation breeding programmes, used widely by zoological parks and aquariums, may appear in some cases to reduce fitness by decreasing animals' abilities to cope when confronted with the 'wild side' of their natural habitats. Would less comfortable captive conditions lead to the selection of individuals that, despite being adapted to life in a captive environment, be better able to thrive if relocated to a more natural environment? While threatened populations may benefit from advanced reproductive technologies, these may actually induce undesirable epigenetic changes. Thus, there may be inherent risks to the health and welfare of offspring (as is suspected in humans). Advanced breeding technologies, especially those that aim to regenerate the rarest species using stem cell reprogramming and artificial gametes, may also lead to unwanted epigenetic modifications. Current knowledge is still incomplete, and therefore ethical decisions about novel breeding methods remain controversial and difficult to resolve.

Recombinant human OVGP1 increases intracellular calcium and further potentiates the effects of progesterone on human sperm

Purpose

To investigate the effects of recombinant human oviduct–specific glycoprotein (rHuOVGP1) alone and in combination with progesterone (P4) on intracellular Ca²⁺ concentration [Ca²⁺]_i and to investigate if rHuOVGP1 in combination with P4 can further enhance tyrosine phosphorylation (pY) of sperm proteins during human sperm capacitation.

Methods

Fluorometric flow cytometry was performed to examine the effects of rHuOVGP1 on [Ca²⁺]_i in human sperm during capacitation. Confocal microscopy was used in conjunction with live cell imaging to analyze the influence of rHuOVGP1 and P4 on [Ca²⁺]_i in the sperm tail and to examine the involvement of CatSper channels in their effect on [Ca²⁺]_i. Western blot analysis was performed to assess the protein levels of p105, a major tyrosine-phosphorylated sperm protein.

Results

rHuOVGP1 increases [Ca²⁺]_i in human sperm at the beginning of capacitation and further increases and sustains the level of [Ca²⁺]_i in the sperm tail following the addition of P4. Inhibition of CatSper channels impedes the effects of rHuOVGP1 on [Ca²⁺]_i in the sperm tail. P4 alone can increase pY of a major human sperm protein, p105, yet yields a further increase when used in combination with rHuOVGP1.

Conclusion

The present study revealed that rHuOVGP1 may work with P4 to upregulate [Ca²⁺]_i at the beginning of capacitation in part through CatSper channels which, in turn, leads to the downstream event of pY of sperm proteins and enhancement of sperm capacitation.

Supplementary information

The online version contains supplementary material available at 10.1007/s10815-022-02591-0.

The semenogelin I-derived peptide SgI-52 in seminal plasma participates in sperm selection and clearance by macrophages

BACKGROUND

Macrophages can phagocytose sperm, especially damaged spermatozoa, in the female genital tract. The semenogelin I-derived peptide SgI-52 in seminal plasma exhibits seminal plasma motility inhibitor (SPMI) activity and can inhibit sperm motility. This raises the question of the role played by SPMIs in macrophage-mediated phagocytosis of sperm. We speculated that SgI-52 promotes sperm clearance by macrophages. Therefore, we investigated the phagocytosis of sperm in different states using this peptide.

METHODS

SgI-52 was fluorescently labeled, and its binding site for sperm was observed. The ability of macrophages to phagocytose sperm was observed using fluorescence confocal microscopy. Spermatozoa from different sources were co-cultured with SgI-52 in BWW medium for 4 and 22 h to compare the differences in their phagocytosis by macrophages. Sperm motility, induced acrosome reaction, mitochondrial membrane potential, and ATP content were examined after incubation with SgI-52.

RESULTS

SgI-52 could bind to spermatozoa in different states, mainly to the tail, and then spread to the acrosome. This effect was more pronounced in demembranated spermatozoa. SgI-52 promoted phagocytosis of spermatozoa by macrophages, decreased the mitochondrial membrane potential, and increased the average ATP content of spermatozoa (P < 0.05).

CONCLUSIONS

We found for the first time that SgI-52 can bind to spermatozoa in different states and promote their phagocytosis by macrophages. Therefore, we speculate that SgI-52 is involved in the screening of sperm in the female reproductive tract and has potential value in improving assisted reproductive technology.

Pre-Treatment of Swine Oviductal Epithelial Cells with Progesterone Increases the Sperm Fertilizing Ability in an IVF Model

Mammalian spermatozoa are infertile immediately after ejaculation and need to undergo a functional modification, called capacitation, in order to acquire their fertilizing ability. Since oviductal epithelial cells (SOECs) and progesterone (P4) are two major modulators of capacitation, here we investigated their impact on sperm functionality by using an IVF swine model. To that, we treated SOECs with P4 at 10, 100, and 1000 ng/mL before the coincubation with spermatozoa, thus finding that P4 at 100 ng/mL does not interfere with the cytoskeleton dynamics nor the cells’ doubling time, but it promotes the sperm capacitation by increasing the number of spermatozoa per polyspermic oocyte (p < 0.05). Moreover, we found that SOECs pre-treatment with P4 100 ng/mL is able to promote an increase in the sperm fertilizing ability, without needing the hormone addition at the time of fertilization. Our results are probably due to the downregulation in the expression of OVGP1, SPP1 and DMBT1 genes, confirming an increase in the dynamism of our system compared to the classic IVF protocols. The results obtained are intended to contribute to the development of more physiological and efficient IVF systems.

Sperm-oviduct interaction: Differential gene expression of growth factors induced by sperm DNA fragmentation

The present study investigated the effects of DNA fragmentation of spermatozoa on the growth factors expression by a human oviduct epithelial cell line (OE-E6/E7). Two separate groups were examined in this study. The cell line was cultured in the presence of spermatozoa with normal DNA fragmentation index (DFI) or abnormal DFI. Total RNA from the cell line in each group was isolated, and relative expression of objective genes was analysed using PCR array. Also, the concentration of VEGF, BMP-2, BMP-7 and MSTN in the supernatant of cell culture was analysed by the ELISA method. The PCR array analysis revealed that most of the growth factors had been upregulated in the abnormal group. However, the differences between groups were statistically significant (p < 0.05) for five genes, including VEGF-A, BMP-2, BMP-6, BMP-7 and OSM. Furthermore, MSTN was the only gene that down-regulated significantly under the influence of the spermatozoa with abnormal DFI. Moreover, the results of ELISA analysis were in agreement with the data of the PCR array. It has been concluded that DNA fragmentation in human spermatozoa can probably change regular events throughout the oviducts. Consequently, the genes of interest may change sperm function and probably its fate in the female reproductive tract.

Sperm Selection for ICSI: Do We Have a Winner?

In assisted reproductive technology (ART), the aim of sperm cells’ preparation is to select competent spermatozoa with the highest fertilization potential and in this context, the intracytoplasmic sperm injection (ICSI) represents the most applied technique for fertilization. This makes the process of identifying the perfect spermatozoa extremely important. A number of methods have now been developed to mimic some of the natural selection processes that exist in the female reproductive tract. Although many studies have been conducted to identify the election technique, many doubts and disagreements still remain. In this review, we will discuss all the sperm cell selection techniques currently available for ICSI, starting from the most basic methodologies and continuing with those techniques suitable for sperm cells with reduced motility. Furthermore, different techniques that exploit some sperm membrane characteristics and the most advanced strategy for sperm selection based on microfluidics, will be examined. Finally, a new sperm selection method based on a micro swim-up directly on the ICSI dish will be analyzed. Eventually, advantages and disadvantages of each technique will be debated, trying to draw reasonable conclusions on their efficacy in order to establish the gold standard method.

Parameters to identify good quality oocytes and embryos in cattle

Oocyte/embryo selection methodologies are either invasive or noninvasive and can be applied at various stages of development from the oocyte to cleaved embryos and up to the blastocyst stage. Morphology and the proportion of embryos developing to the blastocyst stage are important criteria to assess developmental competence. Evaluation of morphology remains the method of choice for selecting viable oocytes for IVP or embryos prior to transfer. Although non-invasive approaches are improving, invasive ones have been extremely helpful in finding candidate genes to determine oocyte/embryo quality. There is still a strong need for further refinement of existing oocyte and embryo selection methods and quality parameters. The development of novel, robust and non-invasive procedures will ensure that only embryos with the highest developmental potential are chosen for transfer. In the present review, various methods for assessing the quality of oocytes and preimplantation embryos, particularly in cattle, are considered. These methods include assessment of morphology including different staining procedures, transcriptomic and proteomic analyses, metabolic profiling, as well as the use of artificial intelligence technologies.

An Update on Semen Physiology, Technologies, and Selection Techniques for the Advancement of In Vitro Equine Embryo Production: Section II

Simple Summary

In order to improve fertilization and pregnancy rates within artificial insemination or in vitro fertilization techniques in horses, producers may choose to select the best sperm within an ejaculate. In this paper, we review conventional and novel methods of sperm selection.

Abstract

As the use of assisted reproductive technologies (ART) and in vitro embryo production (IVP) expand in the equine industry, it has become necessary to further our understanding of available semen selection techniques. This segment of our two-section review will focus on the selection of spermatozoa based on quality and sex for equine intracytoplasmic sperm injection (ICSI), as well as current and future developments in sperm sorting technologies. Ultimately, novel methods of semen selection will be assessed based on their efficacy in other species and their relevance and future application towards ARTs in the horse.

Analysis of Expression Profiles of CircRNA and MiRNA in Oviduct during the Follicular and Luteal Phases of Sheep with Two Fecundity (FecB Gene) Genotypes

CircRNA and miRNA, as classes of non-coding RNA, have been found to play pivotal roles in sheep reproduction. There are many reports of circRNA and miRNA in the ovary and uterus, but few in the oviduct. In this study, RNA-Seq was performed to analyze the expression profile of circRNA and miRNA in the oviduct during the follicular phase and luteal phase of sheep with FecB^BB and FecB⁺⁺ genotypes. The results showed that a total of 3223 circRNAs and 148 miRNAs were identified. A total of 15 DE circRNAs and 40 DE miRNAs were found in the comparison between the follicular phase and luteal phase, and 1 DE circRNA and 18 DE miRNAs were found in the comparison between the FecB^BB genotype and FecB⁺⁺ genotype. GO and KEGG analyses showed that the host genes of DE circRNAs were mainly enriched in the Rap1 signaling pathway, PI3K-Akt signaling pathway and neuroactive ligand-receptor interactions. Novel_circ_0004065, novel_circ_0005109, novel_circ_0012086, novel_circ_0014274 and novel_circ_0001794 were found to be possibly involved in the oviductal reproduction process. GO and KEGG analyses showed that the target genes of DE miRNAs were mainly enriched in insulin secretion, the cAMP signaling pathway, the cGMP-PKG signaling pathway, the Rap1 signaling pathway and the TGF-β signaling pathway, and the target genes LPAR1, LPAR2, FGF18, TACR3, BMP6, SMAD4, INHBB, SKP1 and TGFBR2 were found to be associated with the reproductive process. Miranda software was used to identify 27 miRNAs that may bind to 13 DE circRNAs, including miR-22-3p (target to novel_circ_0004065), miR-127, miR-136 (target to novel_circ_0000417), miR-27a (target to novel_circ_0014274) and oar-miR-181a (target to novel_circ_ 0017815). The results of this study will help to elucidate the regulatory mechanisms of circRNAs and miRNAs in sheep reproduction. Our study, although not establishing direct causal relationships of the circRNA and miRNA changes, enriches the sheep circRNA and miRNA database and provides a basis for further studies on sheep reproduction.

Misconceptions about Conception and Other Fallacies: Historical Bias in Reproductive Biology

Natural selection (differential reproduction) is a major tenet of evolutionary theory. In mammals the success of reproduction is primarily controlled by females who provide the majority of offspring care via gestation and lactation. In some species, maternal care also extends post-weaning. This primacy of female reproduction in evolution has not quite crept into our understanding of organismal adaptations in anatomy, physiology, and behavior. This cultural legacy has left its mark and led to misconceptions in our understanding of reproductive biology that are especially prominent in the understanding of reproduction in the general public. Here, I give examples of such misconceptions. I focus on aspects of physiology (the "sperm race," the "estrous cycle," the "28-day" menstrual cycle, "sex" hormones, and meiosis) as well as aspects of terminology in morphology and behavior. The issues I raise are not new, but all remain embedded in the teaching of reproductive biology especially at the introductory level. For each issue, I examine the historical bias, the consequences of that bias, and, more importantly, ways to ameliorate that bias going forward.

Microvascularization and Expression of Fibroblast Growth Factor and Vascular Endothelial Growth Factor and Their Receptors in the Mare Oviduct

Simple Summary

The oviduct provides the ideal conditions for fertilization and early embryonic development. Adequate vascularization is essential for proper oviduct physiological function. In this work on the mare oviduct, differences in the oviductal artery and arterioles and their ramifications in the infundibulum, ampulla and isthmus were examined. Locally, vascularization is modulated by the action of angiogenic factors, mediated by their specific receptors. In the present study, the isthmus presented the largest vascular area and the highest number of vascular structures in the follicular phase. We have also shown that the relative abundance of angiogenic transcripts and proteins, such as fibroblast growth factor 1 (FGF1) and 2 (FGF2) and vascular endothelial growth factor (VEGF), and their respective receptors (FGFR1, FGFR2, VEGFR2 = KDR), were present in all portions of the oviduct throughout the estrous cycle. There was an increase in the transcripts of angiogenic receptors FGF1 and FGFR1 in the ampulla and isthmus, and of FGF2 and KDR in the isthmus. This was also observed in the isthmus, where the relative abundance of proteins FGFR1 and KDR was the highest. This study shows that the equine oviduct presents differences in microvascular density in its portions. The angiogenic factors VEGF, FGF1, FGF2 and their respective receptors are expressed in all studied regions of the mare oviduct, in agreement with microvascular patterns.

Abstract

The oviduct presents the ideal conditions for fertilization and early embryonic development. In this study, (i) vascularization pattern; (ii) microvascular density; (iii) transcripts of angiogenic factors (FGF1, FGF2, VEGF) and their receptors—FGFR1, FGFR2, KDR, respectively, and (iv) the relative protein abundance of those receptors were assessed in cyclic mares’ oviducts. The oviductal artery, arterioles and their ramifications, viewed by means of vascular injection-corrosion, differed in the infundibulum, ampulla and isthmus. The isthmus, immunostained with CD31, presented the largest vascular area and the highest number of vascular structures in the follicular phase. Transcripts (qPCR) and relative protein abundance (Western blot) of angiogenic factors fibroblast growth factor 1 (FGF1) and 2 (FGF2) and vascular endothelial growth factor (VEGF), and their respective receptors (FGFR1, FGFR2, VEGFR2 = KDR), were present in all oviduct portions throughout the estrous cycle. Upregulation of the transcripts of angiogenic receptors FGF1 and FGFR1 in the ampulla and isthmus and of FGF2 and KDR in the isthmus were noted. Furthermore, in the isthmus, the relative protein abundance of FGFR1 and KDR was the highest. This study shows that the equine oviduct presents differences in microvascular density in its three portions. The angiogenic factors VEGF, FGF1, FGF2 and their respective receptors are expressed in all studied regions of the mare oviduct, in agreement with microvascular patterns.

Porcine oocyte preincubation in oviductal fluid flush before in vitro fertilization in the presence of oviductal epithelial cells improves monospermic zygote production

The present study was designed to evaluate the effect of the combination of oviduct fluid flush (OFF) and oviduct epithelial cells (OEC) in modulating the incidence of polyspermy in pigs. Therefore, for in vitro fertilization (IVF), oocyte and sperm were co-cultured in Tris-buffered medium (TBM) either supplemented with 10% OFF (OFFD group), or in the presence of a bovine OEC monolayer (OEC group), or the oocytes were exposed to OFF for 30 min before IVF (OFFB group), or in the presence of an OEC monolayer (OFFB + OEC group). Regardless of sperm concentration used (0.5, 1.5, and 4.5 × 105 cells/ml), supplementation of IVF medium with 10% OFF led to an increased (P < 0.05) monospermy rate, without alteration (P > 0.05) of the penetration rate in comparison with the control and OEC groups. When the IVF medium was supplemented with heparin, an overall increase (P < 0.05) of the final output of the IVF system in terms of zygotes with two pronuclei (2PN) was observed in the OFFD group, compared with the control and OEC groups, at a sperm concentration of 4.5 × 105 cells/ml. At this concentration, OFFB improved the monospermy rate but decreased the penetration rate, resulting in low efficiency of monospermic zygotes production. Despite this, no major effect was observed in the developmental competence of the presumed zygotes up to the blastocyst stage. The combination of OFFB with OEC improved the penetration rate, while maintaining the high monospermic rate induced by OFFB. In conclusion, the combination of treatment of oocytes by diluted OFF 30 min before IVF, followed by IVF in the presence of OEC, improved monospermic zygote production without reducing the penetration rate, when the IVF medium was supplemented with heparin.

New insights into molecular aspects of sperm-oviductal binding in Egyptian buffaloes using an in vitro model: Effects of oviductal segments and media

We aimed (I) to simulate an in vivo milieu, through establishing an in vitro paradigm to study sperm-oviductal interactions using different segments of oviduct, as well as different incubation media, and (II) to investigate spatial changes of oviductal gene expression. Two experiments were designed; one was to investigate the yield of oviduct aggregates from different oviduct segments; in the second experiment, we observed effects of different incubation media on sperm-oviductal binding. Oviduct cell pellets before (control) and after sperm binding were collected for RNA isolation and gene expression. Isthmus resulted in a higher aggregate yield and possessed the highest affinity towards spermatozoa. The different segments of oviduct showed clear changes in gene expression after sperm binding. TALP medium promoted formation of a higher number of oviduct aggregates towards spermatozoa. Different media resulted in profound alterations in isthmus gene expression. Collectively, isthmus segment in TALP media showed the highest binding affinity to spermatozoa. At the molecular level, our in vitro model was successful for simulation in vivo milieu. Thus, our findings could be used as a simple tool to gain more insights into the molecular regulation of sperm movement, selection and affinity for oviductal binding in buffaloes.

A fully integrated biomimetic microfluidic device for evaluation of sperm response to thermotaxis and chemotaxis

In recent decades, humans have faced greater challenges in reproduction. Assisted reproductive technology is the most prominent approach for addressing this problem. Current clinical screening methods simply consider the motility or morphology of the sperm. However, as the spermatozoa need to navigate over a long distance in the female reproductive tract and survive the natural screening processes therein, these methods are imperfect. Many approaches have been undertaken to study the chemotaxis and thermotaxis navigation behavior of spermatozoa, but few of these have involved integrated screening that considers motility, chemotaxis, and thermotaxis based on the biological environment of the human body. Current routine sperm evaluation techniques are inadequate and fail to simultaneously provide conclusive evidence for the thermotactic and chemotactic characteristics of sperm. Thus, such screening of functional spermatozoa will be an advancement in assisted reproduction. In this study, we developed a fully integrated biomimetic microfluidic system for screening sperm for their characteristics when exposed to temperature and chemical gradients. Based on our results, we showed that spermatozoa were attracted by temperature and chemical gradients in the physiological range. Moreover, we ascertained a suitable temperature gradient range for thermotaxis and statistically proved that the thermotactic and chemotactic responses are not linked. Here, we report the first quantitative study of functional sperm during thermotaxis and chemotaxis, and our analysis of the difference in motility caused by different conditions. More broadly, we foresee the clinical application of these biologically motivated parameters and characteristics in assisted reproduction in humans.

Metabolomic differences in blastocoel and uterine fluids collected in vivo by ultrasound biomicroscopy on rabbit embryos†

The success of embryo development and implantation depends in part on the environment in which the embryo evolves. However, the composition of the uterine fluid surrounding the embryo in the peri-implantation period remains poorly studied. In this work, we aimed to develop a new strategy to visualize, collect, and analyze both blastocoelic liquid and juxta-embryonic uterine fluid from in vivo peri-implantation rabbit embryos. Using high-resolution ultrasound biomicroscopy, embryos were observed as fluid-filled anechoic vesicles, some of which were surrounded by a thin layer of uterine fluid. Ultrasound-guided puncture and aspiration of both the blastocoelic fluid contained in the embryo and the uterine fluid in the vicinity of the embryo were performed. Using nuclear magnetic resonance spectroscopy, altogether 24 metabolites were identified and quantified, of which 21 were detected in both fluids with a higher concentration in the uterus compared to the blastocoel. In contrast, pyruvate was detected at a higher concentration in blastocoelic compared to uterine fluid. Two acidic amino acids, glutamate and aspartate, were not detected in uterine fluid in contrast to blastocoelic fluid, suggesting a local regulation of uterine fluid composition. To our knowledge, this is the first report of simultaneous analysis of blastocoelic and uterine fluids collected in vivo at the time of implantation in mammals, shedding new insight for understanding the relationship between the embryo and its local environment at this critical period of development.

A Comparative View on the Oviductal Environment during the Periconception Period

The oviduct plays important roles in reproductive events: sperm reservoir formation, final gamete maturation, fertilization and early embryo development. It is well known that the oviductal environment affects gametes and embryos and, ultimately, the health of offspring, so that in vivo embryos are better in terms of morphology, cryotolerance, pregnancy rates or epigenetic profile than those obtained in vitro. The deciphering of embryo-maternal interaction in the oviduct may provide a better understanding of the embryo needs during the periconception period to improve reproductive efficiency. Here, we perform a comparative analysis among species of oviductal gene expression related to embryonic development during its journey through the oviduct, as described to date. Cross-talk communication between the oviduct environment and embryo will be studied by analyses of the secreted or exosomal proteins of the oviduct and the presence of receptors in the membrane of the embryo blastomeres. Finally, we review the data that are available to date on the expression and characterization of the most abundant protein in the oviduct, oviductin (OVGP1), highlighting its fundamental role in fertilization and embryonic development.

Effect of oviductal fluid on bull sperm functionality and fertility under non-capacitating and capacitating incubation conditions

This study investigated the effect of bovine oviductal fluid from late follicular (LF) and early luteal (EL) phases on bull sperm functionality under non-capacitating (NCAP) and capacitating (CAP) conditions. Frozen-thawed semen samples from five bulls were thawed and incubated (0, 1 or 2 h) in NCAP and CAP media supplemented with 1% bovine oviductal fluid (LF and EL groups) and in absence of fluid (C group). Motion parameters were assessed by CASA; sperm viability, acrosomal integrity and membrane lipid disorder parameters were evaluated by flow cytometry; and sperm DNA fragmentation was evaluated by the Comet assay. Finally, in vitro fertilization with sperm treated under CAP conditions was performed and further embryo culture results evaluated. In NCAP medium, addition of LF and EL fluid increased the total and progressive motility, and LF fluid improved the stability of sperm DNA. However, under CAP conditions addition of LF and EL fluid decreased some sperm motion parameters and some parameters of sperm DNA stability. Proportion of viable sperm cells with low lipid disorder was higher in NCAP than CAP medium and addition of LF fluid markedly increased the proportion of viable spermatozoa with high lipid disorder and acrosome alteration (spontaneous acrosome reaction). Under current conditions, incubation of bull sperm with oviductal fluid before insemination did not affect detrimentally the IVF results nor embryo development, being blastocyst rate similar between CAP-LF, CAP-EL and control groups. In conclusion, oviductal fluid positively influences sperm functionality and modulate in vitro capacitation.

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.

Impact of extracellular folic acid levels on oviductal gene expression

Folate plays a specific role as methyl donor for nucleotide synthesis and genomic methylation patterns, which in turn are important epigenetic determinants in gene expression. Previous studies have revealed the presence of folate in bovine oviductal fluid as well as the existence of a fine-tuned regulation of the gene expression of folate receptors and transporters in bovine oviduct epithelial cells (BOECs). However, the functional implications of folate in the oviduct remain unknown. The present study aimed to assess the effect of folic acid (FA) on expression levels of selected genes that potentially respond to the folate status in in vitro BOECs. To obtain an insight into the optimization of a culture system for assays, gene expression of folate receptors and transporters was compared between BOECs grown in monolayers and in suspension. The results showed that BOECs from isthmus and ampulla in suspension culture better preserved the region-dependent gene expression profile than in monolayers. Subsequently, BOECs from both anatomical regions were separately cultured in suspension for 24 h assaying different FA concentrations: I) TCM-199 (control); II) TCM-199 + 1 μM FA (similar to the oviduct concentration); III) TCM-199 + 10 μM FA and IV) TCM-199 + 100 μM FA. Expression analysis of genes related to important cellular processes including folate transport, DNA methylation, cell-cell interaction, antioxidant activity and signaling pathways was performed in BOECs using RT-qPCR. Our data demonstrated that addition of 1 μM FA did not affect mRNA levels of most genes analyzed. In contrast, BOECs cultured with 10 μM FA exhibited increased mRNA expression levels of genes involved in folate intake, DNA methylation and antioxidant protection. It is worth noting that at 100 μM FA, transcriptional response in BOECs mainly resulted in decreased mRNA levels of the majority of the genes assayed. Interestingly, cytotoxicity analysis showed a similar LDH activity in the culture media of the experimental groups, indicating that cell integrity was not affected by the FA concentrations assayed. In conclusion, our findings suggest that folate can affect BOECs, promoting changes in gene activity in a framework of functional readjustments in response to environmental conditions.

Zinc supplementation within the reference ranges for zinc status in cattle improves sperm quality without modifying in vitro fertilization performance

Zinc (Zn) has important functions in mammalian reproductive processes. In cattle, Zn status can be classified as deficient, marginal, and adequate, depending on the plasma Zn concentration. In addition, Zn deficiency can lead to reproductive failure. The aim of this study was to investigate the effect of maternal Zn status at the beginning of a fixed-time artificial insemination (FTAI) treatment regimen on pregnancy rate in cattle, and evaluate the effect of supplementing in vitro fertilization (IVF) medium with Zn concentrations within the reference range for Zn status on sperm quality and IVF performance. Pregnancy rates of animals with marginal and adequate Zn status did not differ, and there were no Zn-deficient animals detected. Supplementation of 0.8 μg/mL Zn to IVF medium enhanced progressive motility, sperm viability, functional sperm membrane integrity (HOST), acrosomal integrity and sperm-zona binding, without modifying pronuclear formation, or development of embryos to the cleavage or blastocyst stage after IVF. In conclusion, the present results indicate pregnancy rates are not associated with maternal Zn status at the beginning of the FTAI treatment regimen if Zn status is marginal or adequate. Furthermore, supplementation of IVF medium with Zn at concentrations which is considered adequate for Zn status in cattle led to improved sperm quality, without having effects on embryo development in cattle.

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

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

The Presence of D-Penicillamine during the In Vitro Capacitation of Stallion Spermatozoa Prolongs Hyperactive-Like Motility and Allows for Sperm Selection by Thermotaxis

Assisted reproductive technologies (ARTs) in the horse still yield suboptimal results in terms of pregnancy rates. One of the reasons for this is the lack of optimal conditions for the sperm capacitation in vitro. This study assesses the use of synthetic human tubal fluid (HTF) supplemented with D-penicillamine (HTF + PEN) for the in vitro capacitation of frozen/thawed stallion spermatozoa by examining capacitation-related events over 180 min of incubation. Besides these events, we explored the in vitro capacity of the spermatozoa to migrate by thermotaxis and give rise to a population of high-quality spermatozoa. We found that HTF induced higher levels of hyperactive-like motility and protein tyrosine phosphorylation (PTP) compared to the use of a medium commonly used in this species (Whitten's). Also, HTF + PEN was able to maintain this hyperactive-like motility, otherwise lost in the absence of PEN, for 180 min, and also allowed for sperm selection by thermotaxis in vitro. Remarkably, the selected fraction was enriched in spermatozoa showing PTP along the whole flagellum and lower levels of DNA fragmentation when compared to the unselected fraction (38% ± 11% vs 4.4% ± 1.1% and 4.2% ± 0.4% vs 11% ± 2% respectively, t-test p < 0.003, n = 6). This procedure of in vitro capacitation of frozen/thawed stallion spermatozoa in HTF + PEN followed by in vitro sperm selection by thermotaxis represents a promising sperm preparation strategy for in vitro fertilization and intracytoplasmic sperm injection in this species.

A PMMA-Based Microfluidic Device for Human Sperm Evaluation and Screening on Swimming Capability and Swimming Persistence

The selection of high-quality sperm is essential to the success of in vitro fertilization (IVF). As human cervical mucus has a high viscosity, without enough swimming persistence, human sperm clouds cannot arrive at the ampulla to fertilize the egg. In this study, we used swimming capability and motion characteristics that are known to be associated with fertilization ability to evaluate the quality of sperm. Here, a clinically applicable polymethyl methacrylate (PMMA)-based microdevice was designed and fabricated for sperm evaluation and screening for swimming capability and persistence in a viscous environment. In this study, we applied methylcellulose (MC) to mimic the natural properties of mucus in vivo to achieve the selection of motile sperm. Sperm motion was recorded by an inverted microscope. The statistical features were extracted and analyzed. Hundreds of sperm in two treated groups with different concentrations of MC and one control group with human tubal fluid (HTF) media were video recorded. This device can achieve a one-step procedure of high-quality sperm selection and achieve the quantitative evaluation of sperm swimming capability and persistence. Sperm with good swimming capability and persistence may be more suitable for fertilization in a viscous environment. This microdevice and methods could be used to guide the evaluation of sperm motility and screening in the future.

Exosomes and Female Infertility

BACKGROUND

Exosomes are small Extracellular Vesicles (EVs) (40-100 nm) secreted by living cells and mediate the transmission of information between cells. The number and contents of exosomes are associated with diseases such as inflammatory diseases, cancer, metabolic diseases and what we are focusing in this passage-female infertility.

OBJECTIVE

This review focused on the role of exosomes in oocyte development, declined ovarian function, PCOS, uterine diseases, endometrial receptivity and fallopian tube dysfunction in the female.

METHODS

We conducted an extensive search for research articles involving relationships between exosomes and female infertility on the bibliographic database.

RESULTS

It has been reported that exosomes can act as a potential therapeutic device to carry cargoes to treat female infertility. However, the pathophysiological mechanisms of exosomes in female infertility have not been entirely elucidated. Further researches are needed to explore the etiology and provide evidence for potential clinical treatment.

CONCLUSIONS

This review systematically summarized the role exosomes play in female infertility and its potential as drug delivery.

Extracellular vesicles and melatonin benefit embryonic develop by regulating reactive oxygen species and 5-methylcytosine

Embryo culture conditions are crucial as they can affect embryo quality and even offspring. Oviductal extracellular vesicles (EVs) long been considered a major factor influencing interactions between the oviduct and embryos, and thus its absence is associated with inferior embryonic development in in vitro culture. Herein, we demonstrated that melatonin is present in oviduct fluids and oviduct fluid-derived EVs. Addition of either EVs (1.87 × 10¹¹ particles/mL) or melatonin (340 ng/mL) led to a significant downregulation of reactive oxygen species (ROS) and 5-methylcytosine (5-mC), as well as an increase in the blastocyst rate of embryos, which was inhibited by the addition of luzindole-a melatonin receptor agonist. A combination of EVs (1.87 × 10¹⁰ particles/mL) and melatonin (at 34.3 pg/mL) led to the same results as well as a significant decrease in the apoptosis index and increase in the inner cell mass (ICM)/trophectoderm (TE) index. These results suggest that an EV-melatonin treatment benefits embryonic development. Our findings provide insights into the role of EVs and melatonin during cell communication and provide new evidence of the communication between embryos and maternal oviduct.

Stage-specific metabolomic changes in equine oviductal fluid: New insights into the equine fertilization environment

A repeatable protocol for equine in vitro fertilization (IVF) has remained elusive. This is likely, in part, due to suboptimal composition of capacitation or IVF media that are currently in use. Hence, we aimed to analyse the metabolome of equine oviductal fluid (OF) at the pre- (PRE) and immediate post-ovulatory (PST) stages using proton magnetic resonance spectroscopy (¹H NMR). Oviductal fluid from eight PRE and six PST mares were used to prepare a total of five samples per group. A total of 18 metabolites were identified. The five metabolites with the highest concentrations in the OF samples were lactate, myoinositol, creatine, alanine and carnitine. Only fumarate and glycine showed significant differences in their concentrations between PRE and PST OF samples, with higher concentrations in the PST samples. In a preliminary study, stallion spermatozoa (n = 3 ejaculates) were incubated with different concentrations of PST OF from one mare (0, 0.0625, 0.125, 0.25, 0.5 or 1%; v:v). After 4 h of sperm incubation, protein tyrosine phosphorylation (PY) by western blotting, sperm motility, and acrosomal status were evaluated. An increase of PY was observed in sperm from two stallions when treated with 0.0625% and 0.125% of OF; however no change in PY was noted in the other stallion. There were no effects of OF on spermatozoa motility or acrosome status. These results provide the first information on the metabolomics of equine OF at different stages of the estrus cycle, and present the possibility that OF may affect PY in stallion spermatozoa.

Novel Techniques of Sperm Selection for Improving IVF and ICSI Outcomes

Almost 50% of the infertility cases are due to male factors. Assisted reproductive technologies (ARTs) allow to overcome the incapacity of these patients' spermatozoa to fertilize the oocyte and produce a viable and healthy offspring, but the efficiency of the different techniques has still the potential to improve. According to the latest reports of the European Society of Human Reproduction and Embryology (ESHRE) and the Centers for Disease Control and Prevention of the United States (CDC), the percentages of deliveries per ART cycle in 2014 and 2016 were 21 and 22%, respectively. Among the reasons for this relatively low efficiency, the quality of the spermatozoa has been pointed out as critical, and the presence of high percentages of DNA-damaged spermatozoa in patients' ejaculates is possibly one of the main factors reducing the ARTs outcomes. Thus, one of the main challenges in reproductive medicine is to ensure the highest quality of the spermatozoa used in ARTs, and specifically, in terms of genetic integrity. The latest techniques for the preparation and selection of human spermatozoa are herein discussed focusing on those proven to improve one or several of the following parameters: sperm genetic integrity, fertilization capacity, embryo production, and in vitro survival, as well as pregnancy and delivery rates following in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). In addition, we discuss the potential of techniques developed in non-human mammals that could be further transferred to the clinic.

Bovine oviductal fluid (bOF) collected in the follicular or luteal phase of the estrous cycle exerts similar effects on ram sperm kinematics and acrosome reactivity in vitro

This study examined the effects of bovine oviductal fluid (bOF) obtained during the follicular or luteal phase of the estrous cycle on ram sperm kinematics, capacitation status and plasma membrane (PM) integrity at various time points during the 24-h incubation period. Fresh ram spermatozoa were selected using the swim-up technique and then incubated separately with either follicular phase (FbOF) or luteal phase (LbOF) bovine oviductal fluid added to Fert-TALP medium (positive control - POSControl) or in Fert-TALP medium without capacitating agents (negative control - NEGControl) at 38 °C under 5% CO₂. Incubation with FbOF or LbOF for 2 h and 4 h promoted an increase (P <  0.05) in most of the sperm motility parameters as compared with the NEGControl group, and bOF-induced changes in sperm kinematics were similar (P >  0.05) to those seen in the POSControl group. After 6 h of incubation, the stimulatory effect of FbOF or LbOF on ram sperm kinematics was no longer observed (P >  0.05). Sperm PM integrity was not affected (P >  0.05) by incubation in bOF-supplemented media or in absence of capacitating factors (NEGControl). Although neither FbOF nor LbOF had any effect on sperm capacitation rates, the proportion of acrosome-reacted spermatozoa was greater (P < 0.05) for bOF-containing media compared with the NEGControl group during the long incubation periods (18 h and 24 h). In conclusion, bOF from either follicular or luteal phase of the estrous cycle enhances ram sperm motility for up to 4 h and the rate of acrosome reaction after long (18-24 h) incubation periods without affecting sperm viability.

Extracellular Vesicles in the Oviduct: Progress, Challenges and Implications for the Reproductive Success

The oviduct is the anatomical part of the female reproductive tract where the early reproductive events take place, from gamete transport, fertilization and early embryo development to the delivery of a competent embryo to the uterus, which can implant and develop to term. The success of all these events rely upon a two-way dialogue between the oviduct (lining epithelium and secretions) and the gametes/embryo(s). Recently, extracellular vesicles (EVs) have been identified as major components of oviductal secretions and pointed to as mediators of the gamete/embryo-maternal interactions. EVs, comprising exosomes and microvesicles, have emerged as important agents of cell-to-cell communication by the transfer of biomolecules (i.e., mRNAs, miRNAs, proteins) that can modulate the activities of recipient cells. Here, we provide the current knowledge of EVs in the oviductal environment, from isolation to characterization, and a description of the EVs molecular content and associated functional aspects in different species. The potential role of oviductal EVs (oEVs) as modulators of gamete/embryo-oviduct interactions and their implications in the success of early reproductive events is addressed. Lastly, we discuss current challenges and future directions towards the potential application of oEVs as therapeutic vectors to improve pregnancy disorders, infertility problems and increase the success of assisted reproductive technologies.

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.

Extracellular vesicle mediated embryo-endometrial cross talk during implantation and in pregnancy

Extracellular vesicles are lipoproteinaceous membrane-enclosed nanometer-sized structures produced by cells and are thought to mediate cellular communications. Loaded with a specific set of miRNA and protein depending on their tissue of origin, these extracellular vesicles modulate diverse set of biological processes in their target tissues. In recent years, data has gathered on the roles of extracellular vesicles in embryo implantation and pregnancy. Embryo, oviduct, endometrial epithelium and stroma/decidua derived vesicles interact with trophoblast cells and promote their growth and differentiation to aid in embryo implantation. The placental vesicles are detected in maternal circulation that aids in feto-maternal immune tolerance, their levels vary in women with pregnancy-related complications like preeclampsia. Beyond the host, the microbes in the genital tract are also reported to produce extracellular vesicles which are thought to be responsible for inflammation and preterm births. This review focuses on the extracellular vesicular trafficking involved in success of pregnancy.

Detection of extracellular vesicles in the mouse vaginal fluid: Their delivery of sperm proteins that stimulate capacitation and modulate fertility

Extracellular vesicles (EVs) were isolated by ultracentrifugation of vaginal luminal fluid (VLF) from superovulated mice and identified for the first time using transmission electron microscopy. Characterized by size and biochemical markers (CD9 and HSC70), EVs were shown to be both microvesicular and exosomal and were dubbed as "Vaginosomes" (VGS). Vaginal cross-sections were analyzed to visualize EVs in situ: EVs were present in the lumen and also embedded between squamous epithelial and keratinized cells, consistent with their endogenous origin. Western blots detected Plasma membrane Ca²⁺ -ATPase 1 (PMCA1) and tyrosine-phosphorylated proteins in the VGS cargo and also in uterosomes. Flow cytometry revealed that following coincubation of caudal sperm and VLF for 30 min, the frequencies of cells with the highest Sperm adhesion molecule 1 (SPAM1), PMCA1/4, and PMCA1 levels increased 16.4-, 8.2-, and 27-fold, respectively; compared with control coincubated in phosphate buffered saline (PBS). Under identical conditions, sperm tyrosine-phosphorylated proteins were elevated ~3.3-fold, after VLF coincubation. Progesterone-induced acrosome reaction (AR) rates were significantly (p < 0.001) elevated in sperm coincubated with VGS for 10-30 min, compared with PBS. Sperm artificially deposited in the vaginas of superovulated females for these periods also showed significant (p < 0.01) increases in AR rates, compared with PBS. Thus in vitro and in vivo, sperm acquire from the vaginal environment factors that induce capacitation, explaining recent findings for their acrosomal status in the isthmus. Overall, VGS appear to deliver higher levels of proteins involved in preventing premature capacitation and AR than those promoting them. Our findings which have implications for humans open the possibility of new approaches to infertility treatment with exosome therapeutics.

Epi-nutrients in the oviductal environment: Folate levels and differential gene expression of its receptors and transporters in the bovine oviduct

Recent studies have demonstrated that the oviductal environment plays an active role in modulating the epigenetic marks of the preimplantation embryo genome, but the molecular factors that mediate this epigenetic effect are unknown. Folate is a well-known epi-nutrient that can impact on cell epigenetic machinery during embryonic and fetal development. However, the study of this epi-nutrient in the oviduct is still limited. The present study was conducted to confirm the presence and physiological concentration of folate in bovine oviductal fluid (OF) and to determine if bovine oviduct epithelial cells (BOECs) are able to regulate the uptake of this micronutrient. Samples of OF from ipsi- and contralateral oviducts were collected at different stages of the estrous cycle and folate levels were determined using a competitive receptor binding immunoassay. In addition, gene expression of folate receptors (FOLR1, FOLR2) and transporters (SLC19A1, SLC46A1) were analyzed in BOECs from ampulla and isthmus regions during different stages of the estrous cycle using RT-qPCR. In vitro culture assays were also performed to evaluate whether expression of these genes responds to hormonal stimulation. Our results demonstrated presence of folate in the OF, showing changes of its concentration in the ipsilateral oviduct during the estrous cycle and significantly lower levels at the postovulatory stage. Moreover, gene expression of folate receptors and transporters was detected in BOECs, showing regional and cycle-dependent changes. In particular, differential expression of FOLR1 mRNA was observed in BOECs from the isthmus region, reaching significantly higher levels during the postovulatory stage. Under in vitro culture conditions, gene expression of folate receptors and transporters was maintained in BOEC explants and a particular susceptibility to steroid hormone stimulation was observed. In conclusion, the present study confirms the presence of folate in the bovine oviduct and proves the existence of a fine-tuned regulation of the expression of its receptors and transporters, highlighting the importance to expand the knowledge about this epi-nutrient in the oviductal context.