The abundance and localization of heat shock proteins (HSP)-60, -70, and -90 in the oviductal ampulla of hamadryas baboon (Papio hamadryas) during the menstrual cycle

The presence of HSPs in female reproductive and their relationship with the steroid hormone fluctuation have been reported in several mammals but not in non-human primates. The present research dealt with the oviductal expression and localization of the more studied HSPs (60, 70, and 90) as well as the morphological changes in the Hamadryas baboon (Papio hamadryas) during the follicular, preovulatory, and luteal phases of the menstrual cycle. Therefore, western blots, histomorphological, and immunohistochemical analyses were carried out. The results of western blot analysis displayed the lowest HSP expression in the luteal phase. The histomorphology showed that the mucosal epithelium consisted of undifferentiated cuboidal cells in follicular and luteal phases and well-distinguishable columnar ciliated and non-ciliated cells during the preovulatory phase. Immunohistochemistry evidenced that the mucosal epithelium contained cytoplasmic and nuclear HSP60, 70, and 90 immunostaining in the follicular and luteal phases. During the preovulatory phase, the non-ciliated cells showed: (i) cytoplasmic HSP60; (ii) nuclear and cytoplasmic HSP90. Ciliated cells showed cytoplasmic and ciliary HSP70 and ciliary HSP90. The stromal cells and myocytes of muscular layer displayed a decreased cytoplasmic HSP60 in the preovulatory phase and nuclear and low cytoplasmic HSP70 throughout the menstrual cycle. Nuclear HSP90 decreased in ampulla stromal cells and the follicular phase myocytes. These findings indicate that the expression pattern of HSP60,70, and 90 is related to the morphofunctional features of the baboon oviductal ampulla during the menstrual cycle and could represent a referent point for further studies in the oviduct of Primates.

Microbial, proteomic, and metabolomic profiling of the estrous cycle in wild house mice

Symbiotic microbial communities affect the host immune system and produce molecules contributing to the odor of an individual. In many mammalian species, saliva and vaginal fluids are important sources of chemical signals that originate from bacterial metabolism and may act as honest signals of health and reproductive status. In this study, we aimed to define oral and vaginal microbiomes and their dynamics throughout the estrous cycle in wild house mice. In addition, we analyzed a subset of vaginal proteomes and metabolomes to detect potential interactions with microbiomes. 16S rRNA sequencing revealed that both saliva and vagina are dominated by Firmicutes and Proteobacteria but differ at the genus level. The oral microbiome is more stable during the estrous cycle and most abundant bacteria belong to the genera Gemella and Streptococcus, while the vaginal microbiome shows higher bacterial diversity and dynamics during the reproductive cycle and is characterized by the dominance of Muribacter and Rodentibacter. These two genera cover around 50% of the bacterial community during estrus. Proteomic profiling of vaginal fluids revealed specific protein patterns associated with different estrous phases. Highly expressed proteins in estrus involve the keratinization process thus providing estrus markers (e.g., Hrnr) while some proteins are downregulated such as immune-related proteins that limit bacterial growth (Camp, Clu, Elane, Lyz2, and Ngp). The vaginal metabolome contains volatile compounds potentially involved in chemical communication, for example, ketones, aldehydes, and esters of carboxylic acids. Data integration of all three OMICs data sets revealed high correlations, thus providing evidence that microbiomes, host proteomes, and metabolomes may interact.IMPORTANCEOur data revealed dynamic changes in vaginal, but not salivary, microbiome composition during the reproductive cycle of wild mice. With multiple OMICs platforms, we provide evidence that changes in microbiota in the vaginal environment are accompanied by changes in the proteomic and metabolomics profiles of the host. This study describes the natural microbiota of wild mice and may contribute to a better understanding of microbiome-host immune system interactions during the hormonal and cellular changes in the female reproductive tract. Moreover, analysis of volatiles in the vaginal fluid shows particular substances that can be involved in chemical communication and reproductive behavior.

Proteomic Approaches to Unravel the Molecular Dynamics of Early Pregnancy in Farm Animals: An In-Depth Review

Infertility is a major problem in farm animals, which has a negative economic effect on farm industries. Infertility can be defined as the inability of animals to achieve a successful pregnancy. Early pregnancy is crucial to establish a successful pregnancy, and it is reported that 70-80% and 20-30% of total embryonic loss occur in cattle and pigs, respectively, during the first month of pregnancy. The advanced high-throughput proteomics techniques provide valuable tools for in-depth understanding of the implantation process in farm animals. In the present review, our goal was to compile, assess, and integrate the latest proteomic research on farm animals, specifically focused on female reproduction, which involves endometrial tissues, uterine fluids, oviductal fluids, and microRNAs. The series of studies has provided in-depth insights into the events of the implantation process by unfolding the molecular landscape of the uterine tract. The discussed data are related to pregnant vs. non-pregnant animals, pregnancy vs. oestrous cycle, different days of the early pregnancy phase, and animals with uterine infections affecting reproduction health. Some of the studies have utilized non-invasive methods and in vitro models to decipher the molecular events of embryo-maternal interaction. The proteomics data are valuable sources for discovering biomarkers for infertility in ruminants and new regulatory pathways governing embryo-uterine interaction, endometrium receptivity, and embryonic development. Here, we envisage that the identified protein signatures can serve as potential therapeutic targets and biomarkers to develop new therapeutics against pregnancy diseases.

Metabolomic evolution of the postpartum dairy cow uterus

High rates of early pregnancy loss are a critical issue in dairy herds, particularly in seasonal, grazing systems. Components of the uterine luminal fluid (ULF), on which the early embryo depends for sustenance and growth, partly determine early pregnancy losses. Here, changes in ULF from early to mid-postpartum in crossbred dairy cows were explored, linking them with divergent embryo development. For this, the uteri of 87 cows at Day 7 of pregnancy at first and third estrus postpartum were flushed to collect ULF. Eighteen metabolites (chiefly organic acids and sugars) significantly varied in abundance across postpartum, indicating a molecular signature of physiological recovery consistent of the upregulation of pyrimidine metabolism and glycerophospholipid metabolism, and downregulation of pentose phosphate and taurine metabolism pathways. Joint pathway analysis of metabolomics data and a previously generated proteomics data set on the same ULF samples suggests key links between postpartum recovery and subsequent successful embryo development. These include upregulation of VEGFA and downregulation of metabolism, NRF2, T-cell receptor, which appear to improve the ULF's capacity of sustaining normal embryo development, and a putative osmo-protectant role of beta-alanine. These relationships should be further investigated to develop tools to detect and reduce early pregnancy loss in dairy cows.

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.

The bovine uterine fluid proteome is more impacted by the stage of the estrous cycle than the proximity of the ovulating ovary in the periconception period

Uterine secretions provide a suitable environment for sperm selective migration during a couple of days preceding ovulation and for early embryo development before implantation. Our goal was to identify and quantify proteins in the bovine uterine fluid during the periovulatory period of the estrous cycle. Genital tracts with normal morphology were collected from adult cyclic Bos taurus females in a local slaughterhouse and classified into pre-ovulatory or post-ovulatory stages of cycle (around days 19-21 and 0-5 of cycle, respectively; n = 8 cows per stage) based on ovarian morphology. Proteins from uterine fluid collected from the utero-tubal junction to the base of each horn (four pools of two cows per condition) were analyzed by nanoLiquid Chromatography coupled with tandem Mass Spectrometry (nanoLC-MS/MS). A total of 1214 proteins were identified, of which 91% were shared between all conditions. Overall, 57% of proteins were predicted to be secreted and 17% were previously reported in uterine extracellular vesicles. Paired comparisons between uterine horns ipsilateral and contralateral to ovulation evidenced 12 differentially abundant proteins, including five at pre-ovulatory stage. Furthermore, 35 proteins differed in abundance between pre- and post-ovulatory stages, including 21 in the ipsilateral side of ovulation. Functional analysis of identified proteins demonstrated roles in binding, metabolism, cellular detoxification and the immune response. This study provides a valuable database of uterine proteins for functional studies on sperm physiology and early embryo development.

The sperm-interacting proteome in the bovine isthmus and ampulla during the periovulatory period

BACKGROUND

Spermatozoa interact with oviduct secretions before fertilization in vivo but the molecular players of this dialog and underlying dynamics remain largely unknown. Our objectives were to identify an exhaustive list of sperm-interacting proteins (SIPs) in the bovine oviduct fluid and to evaluate the impact of the oviduct anatomical region (isthmus vs. ampulla) and time relative to ovulation (pre-ovulatory vs. post-ovulatory) on SIPs number and abundance.

METHODS

Pools of oviduct fluid (OF) from the pre-ovulatory ampulla, pre-ovulatory isthmus, post-ovulatory ampulla, and post-ovulatory isthmus in the side of ovulation were collected from the slaughterhouse. Frozen-thawed bull sperm were incubated with OF or phosphate-buffered saline (control) for 60 min at 38.5 °C. After protein extraction and digestion, sperm and OF samples were analyzed by nanoLC-MS/MS and label-free protein quantification.

RESULTS

A quantitative comparison between proteins identified in sperm and OF samples (2333 and 2471 proteins, respectively) allowed for the identification of 245 SIPs. The highest number (187) were found in the pre-ovulatory isthmus, i.e., time and place of the sperm reservoir. In total, 41 SIPs (17%) were differentially abundant between stages in a given region or between regions at a given stage and 76 SIPs (31%) were identified in only one region × stage condition. Functional analysis of SIPs predicted roles in cell response to stress, regulation of cell motility, fertilization, and early embryo development.

CONCLUSION

This study provides a comprehensive list of SIPs in the bovine oviduct and evidences dynamic spatio-temporal changes in sperm-oviduct interactions around ovulation time. Moreover, these data provide protein candidates to improve sperm conservation and in vitro fertilization media.

miR-17-5p in bovine oviductal fluid affects embryo development

This study identified microRNAs (miRNAs) in bovine oviductal fluids (OFs) and examined the effect of miR-17-5p in OFs on embryonic development to the blastocyst stage. Small RNA-seq of extracellular vesicles of OFs revealed 242 miRNAs. Additionally, analyzing expressions of randomly selected OF-miRNAs with RT-qPCR in the culture medium of oviductal epithelial cells indicated that the abundance of miRNAs in OFs increased during the luteal phase. miR-17-5p mimic-treated eight-cell-stage zona pellucida-free embryos showed improved embryonic development to the blastocyst stage. The effect of the miR-17-5p mimic was confirmed using a dual-luciferase assay and immunostaining. In addition, RNA-seq of the miR-17-5p mimic- or control-treated embryos revealed differentially expressed genes (DEGs), suggesting possible pathways that overlapped with the in silico-predicted pathways for miR-17-5p targeting genes. Furthermore, ingenuity pathway analysis of DEG predicted miR-17 to be a significant upstream regulator. Our results suggest that miR-17-5p in OFs regulates embryonic development in bovines.

Equine Oviductal Organoid Generation and Cryopreservation

Organoids are a type of three-dimensional (3D) cell culture that more closely mimic the in vivo environment and can be maintained in the long term. To date, oviductal organoids have only been reported in laboratory mice, women, and cattle. Equine oviductal organoids were generated and cultured for 42 days (including 3 passages and freeze-thawing at passage 1). Consistent with the reports in mouse and human oviductal organoids, the equine oviductal organoids revealed round cell clusters with a central lumen. Developing a 3D model of the mare oviduct may allow for an increased understanding of their normal physiology, including hormonal regulation. These organoids may provide an environment that mimics the in vivo equine oviduct and facilitate improved in vitro embryo production in equids.

Spatiotemporal profiling of the bovine oviduct fluid proteome around the time of ovulation

Understanding the composition of the oviduct fluid (OF) is crucial to better comprehend the microenvironment in which sperm capacitation, fertilization and early embryo development take place. Therefore, our aim was to determine the spatiotemporal changes in the OF proteome according to the anatomical region of the oviduct (ampulla vs. isthmus), the proximity of the ovulating ovary (ipsilateral vs. contralateral side) and the peri-ovulatory stage (pre-ovulatory or Pre-ov vs. post-ovulatory or Post-ov). Oviducts from adult cyclic cows were collected at a local slaughterhouse and pools of OF were analyzed by nanoLC-MS/MS and label-free protein quantification (n = 32 OF pools for all region × stage × side conditions). A total of 3760 proteins were identified in the OF, of which 65% were predicted to be potentially secreted. The oviduct region was the major source of variation in protein abundance, followed by the proximity of the ovulating ovary and finally the peri-ovulatory stage. Differentially abundant proteins between regions, stages and sides were involved in a broad variety of biological functions, including protein binding, response to stress, cell-to-cell adhesion, calcium homeostasis and the immune system. This work highlights the dynamic regulation of oviduct secretions and provides new protein candidates for interactions between the maternal environment, the gametes and the early embryo.

Proteomic determinants of uterine receptivity for pregnancy in early and mid-postpartum dairy cows†

Dairy cow subfertility is a worldwide issue arising from multiple factors. It manifests in >30% early pregnancy losses in seasonal pasture-grazed herds, especially when cows are inseminated in the early post-partum period. Most losses occur before implantation, when embryo growth depends on factors present in maternal tract fluids. Here we examined the proteomic composition of early and mid-postpartum uterine luminal fluid in crossbred lactating dairy cows to identify molecular determinants of fertility. We also explored changes in uterine luminal fluid from first to third estrus cycles postpartum in individual cows, linking those changes with divergent embryo development. For this, we flushed uteri of 87 cows at day 7 of pregnancy at first and third estrus postpartum, recovering and grading their embryos. Out of 1563 proteins detected, 472 had not been previously reported in this fluid, and 408 were predicted to be actively secreted by bioinformatic analysis. The abundance of 18 proteins with roles in immune regulation and metabolic function (e.g. cystatin B, pyruvate kinase M2) was associated with contrasting embryo quality. Matched-paired pathway analysis indicated that, from first to third estrus postpartum, upregulation of metabolic (e.g. creatine and carbohydrate) and immune (e.g. complement regulation, antiviral defense) processes were related to poorer quality embryos in the third estrus cycle postpartum. Conversely, upregulated signal transduction and protein trafficking appeared related to improved embryo quality in third estrus. These results advance the characterization of the molecular environment of bovine uterine luminal fluid and may aid understanding fertility issues in other mammals, including humans.

Pronounced Postmating Response in the Drosophila Female Reproductive Tract Fluid Proteome

Fertility depends on the progression of complex and coordinated postmating processes within the extracellular environment of the female reproductive tract (FRT). Molecular interactions between ejaculate and FRT proteins regulate many of these processes, including sperm motility, migration, storage, and modification, along with concurrent changes in the female. Although extensive progress has been made in the proteomic characterization of the male-derived components of sperm and seminal fluid, investigations into the FRT have remained more limited. To achieve a comparable level of knowledge regarding female-derived proteins that comprise the reproductive environment, we utilized semiquantitative MS-based proteomics to study the composition of the FRT tissue and, separately, the luminal fluid, before and after mating in Drosophila melanogaster. Our approach leveraged whole-fly isotopic labeling to delineate female proteins from transferred male ejaculate proteins. Our results revealed several characteristics that distinguish the FRT fluid proteome from the FRT tissue proteome: (1) the fluid proteome is encoded by genes with higher overall levels of FRT gene expression and tissue specificity, including many genes with enriched expression in the fat body, (2) fluid-biased proteins are enriched for metabolic functions, and (3) the fluid exhibits pronounced postmating compositional changes. The dynamic mating-induced proteomic changes in the FRT fluid inform our understanding of secretory mechanisms of the FRT, serve as a foundation for establishing female contributions to the ejaculate-female interactions that regulate fertility, and highlight the importance of applying proteomic approaches to characterize the composition and dynamics of the FRT environment.

The Proteome of Equine Oviductal Fluid Varies Before and After Ovulation: A Comparative Study

Equine fertilization cannot be performed in the laboratory as equine spermatozoa do not cross the oocyte's zona pellucida in vitro. Hence, a more profound study of equine oviductal fluid (OF) composition at the pre-ovulatory and post-ovulatory stages could help in understanding what components are required to achieve fertilization in horses. Our work aimed to elucidate the proteomic composition of equine OF at both stages. To do this, OF was obtained postmortem from oviducts of slaughtered mares ipsilateral to a pre-ovulatory follicle (n = 4) or a recent ovulation (n = 4); the samples were kept at −80°C until analysis. After protein extraction and isobaric tags for relative and absolute quantification (iTRAQ) labeling, the samples were analyzed by nano-liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The analysis of the spectra resulted in the identification of a total of 1,173 proteins present in pre-ovulatory and post-ovulatory samples; among these, 691 were unique for Equus caballus. Proteins from post-ovulatory oviductal fluid were compared with the proteins from pre-ovulatory oviductal fluid and were categorized as upregulated (positive log fold change) or downregulated (negative log fold change). Fifteen proteins were found to be downregulated in the post-ovulatory fluid and 156 were upregulated in the post-ovulatory OF compared to the pre-ovulatory fluid; among the upregulated proteins, 87 were included in the metabolism of proteins pathway. The identified proteins were related to sperm–oviduct interaction, fertilization, and metabolism, among others. Our data reveal consistent differences in the proteome of equine OF prior to and after ovulation, helping to increase our understanding in the factors that promote fertilization and early embryo development in horses.

Changes in Oviductal Cells and Small Extracellular Vesicles miRNAs in Pregnant Cows

Early embryonic development occurs in the oviduct, where an ideal microenvironment is provided by the epithelial cells and by the oviductal fluid produced by these cells. The oviductal fluid contains small extracellular vesicles (sEVs), which through their contents, including microRNAs (miRNAs), can ensure proper cell communication between the mother and the embryo. However, little is known about the modulation of miRNAs within oviductal epithelial cells (OECs) and sEVs from the oviductal fluid in pregnant cows. In this study, we evaluate the miRNAs profile in sEVs from the oviductal flushing (OF-sEVs) and OECs from pregnant cows compared to non-pregnant, at 120 h after ovulation induction. In OF-sEVs, eight miRNAs (bta-miR-126-5p, bta-miR-129, bta-miR-140, bta-miR-188, bta-miR-219, bta-miR-345-3p, bta-miR-4523, and bta-miR-760-3p) were up-regulated in pregnant and one miRNA (bta-miR-331-5p) was up-regulated in non-pregnant cows. In OECs, six miRNAs (bta-miR-133b, bta-miR-205, bta-miR-584, bta-miR-551a, bta-miR-1193, and bta-miR-1225-3p) were up-regulated in non-pregnant and none was up-regulated in pregnant cows. Our results suggest that embryonic maternal communication mediated by sEVs initiates in the oviduct, and the passage of gametes and the embryo presence modulate miRNAs contents of sEVs and OECs. Furthermore, we demonstrated the transcriptional levels modulation of selected genes in OECs in pregnant cows. Therefore, the embryonic-maternal crosstalk potentially begins during early embryonic development in the oviduct through the modulation of miRNAs in OECs and sEVs in pregnant cows.

Comprehensive Proteomics Analysis of In Vitro Canine Oviductal Cell-Derived Extracellular Vesicles

Simple Summary

As the dog shows unique and peculiar reproductive characteristics, assisted reproductive techniques such as in vitro maturation and in vitro fertilization have not been well-established compared with those of other mammals. Our recent work demonstrated the interplay between in vitro oviductal cell-derived extracellular vesicles (OC-EVs) and cumulus-oocyte complexes in dogs. Here, we provided for the first time a comprehensive proteomic analysis of OC-EVs. A total of 398 proteins were identified in all OC-EVs samples. A functional enrichment analysis indicated that these core proteins were involved in the key cellular metabolic process related to oocyte maturation and embryonic development. The current comprehensive description of the canine OC-EVs proteome would provide a fundamental resource for further understanding canine reproductive physiology, the interaction of sperms with female counterparts during fertilization, early pregnancy, and establishing an efficient system of in vitro embryo production.

Abstract

Dogs (Canis lupus familiaris) have unique and peculiar reproductive characteristics. While the interplay between in vitro oviductal cell-derived extracellular vesicles (OC-EVs) and cumulus-oocyte complexes in dogs has begun to be elucidated, no study has yet provided extensive information on the biological content and physiological function of OC-EVs and their role in canine oocyte development. Here, we aimed to provide the first comprehensive proteomic analysis of OC-EVs. We identified 398 proteins as present in all OC-EVs samples. The functional enrichment analysis using Gene Ontology terms and an Ingenuity Pathway Analysis revealed that the identified proteins were involved in several cellular metabolic processes, including translation, synthesis, expression, and protein metabolism. Notably, the proteins were also involved in critical canonical pathways with essential functions in oocyte and embryo development, such as ERK/MAPK, EIF2, PI3K/AKT, and mTOR signaling. These data would be an important resource for studying canine reproductive physiology and establishing a successful in vitro embryo production system in dogs.

Local sex steroid hormone milieu in the bovine oviduct ipsilateral and contralateral to preovulatory follicle or corpus luteum during the periovulatory phase

Estradiol-17β (E2) and progesterone (P4) regulate oviductal functions, providing a suitable environment for the transport and maturation of gametes, fertilization, and embryonic development. In addition to the E2 and P4 nuclear receptors, estrogen receptor (ESR) α and β, nuclear progesterone receptor (PGR), nongenomic mechanisms through G protein-coupled estrogen receptor (GPER1), and progesterone receptor membrane component (PGRMC) 1 and 2 mediate E2 and P4 actions. This study aimed to characterize the local endocrine environment of the oviduct by examining the oviductal E2 and P4 concentrations and their receptors' mRNA expression during the periovulatory phase. The bovine oviducts were collected in a slaughterhouse and the days postovulation were estimated according to state of the ovaries and the uterus. Samples of the ampulla and isthmus ipsilateral and contralateral to the preovulatory follicle or corpus luteum were collected on Days 19 to 21, Days 0 to 1, Days 2 to 4, and Days 5 to 7 of the estrous cycle. The effects of the estrous cycle phase and oviductal region (ampulla and isthmus) and side (ipsilateral and contralateral) were analyzed by 3-way ANOVA. Moreover, to clarify the regulatory mechanisms of the mRNA expression of hormone receptors, the effects of E2 and P4 on mRNA expression in the oviduct were examined by multiple linear regression. The oviductal endocrine milieu on Days 19 to 21 was characterized by an E2-dominant environment with high E2 and low P4, high ESR1 and PGR mRNA expression, and low ESR2, GPER1, and PGRMC2 mRNA expression, whereas the corresponding on Days 0 to 1 was characterized by the endocrine milieu without hormone dominance. The environment on Days 2 to 4 and Day 5 to 7 was characterized by opposite tendency of oviductal hormone concentrations and their receptors' mRNA expression to Days 19 to 21. Additionally, the ipsilateral oviduct had the more P4-dominant endocrine milieu, with lower E2 and higher P4 concentrations, and different expression of ESR1/2, GPER1, PGR, and PGRMC2 mRNA when compared with the contralateral oviduct on Days 2 to 4 and Days 5 to 7, except for PGRMC1. Although oviductal E2 and P4 influenced the mRNA expression of ESR1/2, GPER1, PGR, and PGRMC1/2, their effects were different between regions and sides. In summary, the oviductal endocrine milieu varies according to the estrous cycle phase and the oviductal region and side, which may be involved in the estrous cycle phase-specific and oviductal region-specific and side-specific functions.

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.

Extracellular Vesicles and the Oviduct Function

In mammals, the oviduct (or the Fallopian tube in humans) can be divided into the infundibulum (responsible for oocyte pick-up), ampulla (site of fertilization), isthmus (where preimplantation embryos develop), and uterotubal junction (where embryos transit to the uterus). The oviductal fluid, as well as extracellular vesicles produced from the oviduct epithelial cells, referred to as oEVs, have been shown to improve the fertilization process, prevent polyspermy, and aid in embryo development. oEVs contain molecular cargos (such as miRNAs, mRNAs, proteins, and lipids) that can be delivered and fuse to recipient cells. oEVs produced from the ampulla appear to be functionally distinct from those produced from the isthmus. In multiple species including mice, cats, dogs, pigs, and cows, oEVs can be incorporated into the oocytes, sperm, and embryos. In this review, we show the positive impact of oEVs on gamete function as well as blastocyst development and how they may improve embryo quality in in vitro conditions in an assisted reproductive technology setting for rodents, domestic animals, farm animals, and humans.

Exosomes as a Potential Tool for Supporting Canine Oocyte Development

Simple Summary

To date, extracellular vesicles, including exosomes, have markedly gained attention in scientific research because of their physiological homogeneity as well as stability for transporting regulatory molecules to recipient cells. Recently, it has been shown that exosomes impact gametes and embryo development in several mammalian species; however, there is still scant information on the physiological effects of exosomes on the canine reproduction system. In this regard, we elucidate the possible roles of exosomes involvement in oviduct and cumulus-oocyte complexes mutual communications and how oviduct regulates their development via molecular signaling pathways.

Abstract

The canine oviduct is a unique reproductive organ where the ovulated immature oocytes complete their maturation, while the other mammals ovulate matured gametes. Due to their peculiar reproductive characteristics, the in vitro maturation of dog oocytes is still not wellestablished compared with other mammals. Investigations of the microenvironment conditions in the oviductal canal are required to establish a reliable in vitro maturation system in the dog. Previous studies have suggested that the oviduct and its derivatives play a key role in improving fertilization as well as embryo development. In particular, the biological function of oviduct-derived exosomes on sperm and early embryo development has been investigated in porcine, bovine, and murine species. However, the information about their functions on canine cumulus-oocyte complexes is still elusive. Recent canine reproductive studies demonstrated how oviduct-derived extracellular vesicles such as microvesicles and exosomes interact with oocyte-cumulus complexes and how they can play roles in regulating canine cumulus/oocyte communications. In this review, we summarize the physiological characteristics of canine oviduct-derived exosomes and their potential effects on cumulus cells development as well as oocyte in vitro maturation via molecular signaling pathways.

Influence of metabolic status and genetic merit for fertility on proteomic composition of bovine oviduct fluid†

The oviduct plays a crucial role in fertilization and early embryo development providing the microenvironment for oocyte, spermatozoa, and early embryo. Since dairy cow fertility declined steadily over the last decades, reasons for early embryonic loss have gained increasing interest. Analyzing two animal models, this study aimed to investigate the impact of genetic predisposition for fertility and of metabolic stress on the protein composition of oviduct fluid. A metabolic model comprised maiden Holstein heifers and postpartum lactating (Lact) and non-lactating (Dry) cows, while a genetic model consisted of heifers from the Montbéliarde breed and Holstein heifers with low- and high-fertility index. In a holistic proteomic analysis of oviduct fluid from all groups using nano-liquid chromatography tandem-mass spectrometry analysis and label-free quantification, we were able to identify 1976 proteins, among which 143 showed abundance alterations in the pairwise comparisons within both models. Most differentially abundant proteins were revealed between low fertility Holstein and Montbéliarde (52) in the genetic model and between lactating and maiden Holstein (19) in the metabolic model, demonstrating a substantial effect of genetic predisposition for fertility and metabolic stress on the oviduct fluid proteome. Functional classification of affected proteins revealed actin binding, translation, and immune system processes as prominent gene ontology (GO) clusters. Notably, Actin-related protein 2/3 complex subunit 1B and the three immune system-related proteins SERPIND1 protein, immunoglobulin kappa locus protein, and Alpha-1-acid glycoprotein were affected in both models, suggesting that abundance changes of immune-related proteins in oviduct fluid play an important role for early embryonic loss.

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.

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

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

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.

Quantitative proteomic strategies to study reproduction in farm animals: Female reproductive fluids

Reproductive fluids from the female reproductive tract are gaining attention for their potential to support and optimize reproductive processes, including gamete maturation and embryo culture in vitro. Quantitative proteomics is a powerful way to decipher the proteome of reproductive tract fluids and to identify biologically relevant proteins. The present review describes proteomic strategies for analysing female reproductive fluid proteins. In addition, it considers the strategies for the preparation of oviductal, uterine and follicular fluid samples. Finally, it highlights the main results of quantitative proteomic studies, providing insights into the biological processes related to reproductive biology in farm animals. SIGNIFICANCE: Assisted reproductive technologies (ARTs) have become vitally important for farm animal breeding and much effort is going into the optimization and refinement of the techniques. There are also attempts to imitate physiological conditions by adding reproductive fluids or individual fluid proteins to improve in vitro procedures. A detailed knowledge of the reproductive fluid proteomes is indispensable. The present review summarizes the most widely used quantitative proteomic approaches for the analysis of fluids from the female reproductive tract and highlights the potential of quantitative proteomics to delineate reproductive processes and identify candidate proteins for ARTs in farm animals.

Porcine oviductal extracellular vesicles interact with gametes and regulate sperm motility and survival

Once in the female reproductive tract, spermatozoa undergo several modifications to acquire their complete fertilizing ability. Interactions between the oviductal fluid (OF) and gametes contribute to a successful fertilization. Recently, oviductal extracellular vesicles have been identified as an important part of the OF but their interactions with gametes are not fully understood. In the present study, we aim at determining the patterns of interactions between porcine oviductal extracellular vesicles (poEVs) and gametes (spermatozoa and oocytes). Moreover, we evaluate the effect of poEVs on sperm survival and motility to better understand the mechanisms by which poEVs modulate the processes leading to fertilization. Evaluation of poEVs uptake by spermatozoa showed that poEVs bind to spermatozoa in a time and dose dependent manner. Co-incubation of spermatozoa with poEVs (0.2 μg/μL) increased fresh and frozen sperm survival after 6 and 17 h, respectively. By contrast, poEVs supplementation reduced the total and progressive sperm motility after 2 h. Additionally, we demonstrated that poEVs interacted with the cumulus cells, zona pellucida (ZP) and oocyte, being able to cross the ZP. Besides, we showed that poEVs delivered their cargo into the oocyte, by the transfer of OVGP1 protein. In conclusion, our results demonstrated that poEVs are able to interact with both gametes. Besides, the findings from the present study showed that poEVs may participate in maintaining sperm viability and reducing motility, functions associated with the oviduct sperm reservoir. Although further investigations are needed, our results indicate that poEVs can be a potential tool to improve sperm life span during sperm handling and enhance IVF outcomes.

Sperm-Driven Micromotors Moving in Oviduct Fluid and Viscoelastic Media

Biohybrid micromotors propelled by motile cells are fascinating entities for autonomous biomedical operations on the microscale. Their operation under physiological conditions, including highly viscous environments, is an essential prerequisite to be translated to in vivo settings. In this work, a sperm-driven microswimmer, referred to as a spermbot, is demonstrated to operate in oviduct fluid in vitro. The viscoelastic properties of bovine oviduct fluid (BOF), one of the fluids that sperm cells encounter on their way to the oocyte, are first characterized using passive microrheology. This allows to design an artificial oviduct fluid to match the rheological properties of oviduct fluid for further experiments. Sperm motion is analyzed and it is confirmed that kinetic parameters match in real and artificial oviduct fluids, respectively. It is demonstrated that sperm cells can efficiently couple to magnetic microtubes and propel them forward in media of different viscosities and in BOF. The flagellar beat pattern of coupled as well as of free sperm cells is investigated, revealing an alteration on the regular flagellar beat, presenting an on-off behavior caused by the additional load of the microtube. Finally, a new microcap design is proposed to improve the overall performance of the spermbot in complex biofluids.

Hormone-regulated PKA activity in porcine oviductal epithelial cells

The oviduct is a dynamic organ that suffers changes during the oestrous cycle and modulates gamete and embryo physiology. We analyse the possible existence of Protein kinase A (PKA)-dependent hormone-regulated pathways in porcine ampulla and primary cell cultures by 2D-electrophoresis/Western blot using anti-phospho PKA substrate antibodies. Differential phosphorylation was observed for ten proteins that were identified by mass spectrometry. The results were validated for five of the proteins: Annexin A5, Calumenin, Glyoxalase I and II and Enolase I. Immunofluorescence analyses show that Calumenin, Glyoxalase II and Enolase I change their localisation in the oviductal epithelium through the oestrus cycle. The results demonstrate the existence of PKA hormone-regulated pathways in the ampulla epithelium during the oestrus cycle.

Spatial and Pregnancy-Related Changes in the Protein, Amino Acid, and Carbohydrate Composition of Bovine Oviduct Fluid

Knowledge of how the biochemical composition of the bovine oviduct is altered due to the oviduct anatomy or the presence of an embryo is lacking. Thus, the aim of this study was to assess the effect of (І) oviduct anatomy and (ІІ) embryo presence on oviductal fluid (OF) protein, amino acid, and carbohydrate composition. Cross-bred beef heifers (n = 19) were synchronized and those in standing estrus were randomly allocated to a cyclic (non-bred) or pregnant (artificially inseminated) group. All heifers were slaughtered on Day 3 after estrus. The oviducts ipsilateral to the corpus luteum from each animal were isolated, straightened and cut, separating ampulla and isthmus. Each portion was flushed with 500 µl of PBS enabling recovery of the oocyte/embryo. Recovered unfertilized oocytes (cyclic group) and embryos (8-cell embryos; pregnant group) were located in the isthmus of the oviduct. Samples of flushing medium from the isthmus and ampulla were used for proteomic (n = 2 per group), amino acid (n = 5), and carbohydrate (n = 5) analysis. For proteomic analysis, total protein from cyclic and pregnant samples were labelled with different cyanine fluorescent probes and separated according to the isoelectric point using immobilized pH gradient strips (pH 3-10, 17 cm, Protean® IEF cell system, Bio Rad). Second dimension was performed in a polyacrylamide gel (12%) in the presence of SDS using a Protean II XL system (Bio Rad). Images were obtained with a Typhoon 9410 scanner and analyzed with Progenesis SameSpots software v 4.0. Amino acid content in the OF was determined by high performance liquid chromatography (HPLC). Glucose, lactate, and pyruvate were quantified using microfluorometric enzyme-linked assays. For the proteomic assessment, the results of the image analysis were compared by ANOVA. For both amino acid and carbohydrate analyses, statistical analysis was carried out by 2-way ANOVA with the Holm-Sidak nonparametric post hoc analysis. On Day 3 post-estrus, OF composition varied based on (І) anatomical region, where isthmic metabolites were present in lower (i.e., lactate, glycine, and alanine) or higher (i.e., arginine) concentrations compared to the ampulla; and (ІІ) embryo presence, which was correlated with greater, arginine, phosphoglycerate kinase 1, serum albumin, α-1-antiproteinase and IGL@ protein concentrations. In conclusion, data indicate that the composition of bovine OF is anatomically dynamic and influenced by the presence of an early embryo.

The Expression of ERK1/2 in Female Yak (Bos grunniens) Reproductive Organs

The main reproductive organs undergo different histological appearances and physiological processes under different reproductive statuses. The variation of these organs depends on a delicate regulation of cell proliferation, differentiation, and apoptosis. Extracellular signal-regulated kinases1/2 (ERK1/2) are members of the mitogen-activated protein kinase (MAPK) super family. They have important roles in regulating various biological processes of different cells, tissues, and organ types. Activated ERK1/2 generally promotes cell survival, but under certain conditions, ERK1/2 also have the function of inducing apoptosis. It is widely believed that ERK1/2 play a significant role in regulating the reproductive processes of mammals. The goal of our research is to investigate the expression and distribution of ERK1/2 in the yak's main reproductive organs during different stages. In the present study, samples of the ovary, oviduct, and uterus of 15 adult female yak were collected and used in the experiment. The ERK1/2 proteins, localization, and quantitative expression of their mRNA were investigated using immunohistochemistry (IHC), western blot (WB) and relative quantitative real-time polymerase chain reaction (RT-PCR). The results indicated that ERK1/2 proteins and their mRNA were highly expressed in the ovary of the luteal phase and gestation period, in the oviduct of the luteal phase, and in the uterus of the luteal phase and gestation period. Immunohistochemical analysis revealed a strong distribution of ERK1/2 proteins in follicular granulosa cells, granular luteal cells, villous epithelial cells of the oviduct, endometrial glandular epithelium, and luminal epithelium. These results demonstrated that the expression of ERK1 and ERK2 proteins and their mRNA in the yak's ovary, oviduct, and uterus varies with the stage of the reproductive cycle. The variation character of ERK1 and ERK 2 expression in the yak's main reproductive organs during different stages implies that they play an important role in regulating the reproductive function under different physiological statuses.

Identification of 56 Proteins Involved in Embryo-Maternal Interactions in the Bovine Oviduct

The bovine embryo develops in contact with the oviductal fluid (OF) during the first 4–5 days of pregnancy. The aim of this study was to decipher the protein interactions occurring between the developing embryo and surrounding OF. In-vitro produced 4–6 cell and morula embryos were incubated or not (controls) in post-ovulatory OF (OF-treated embryos) and proteins were then analyzed and quantified by high resolution mass spectrometry (MS) in both embryo groups and in OF. A comparative analysis of MS data allowed the identification and quantification of 56 embryo-interacting proteins originated from the OF, including oviductin (OVGP1) and several annexins (ANXA1, ANXA2, ANXA4) as the most abundant ones. Some embryo-interacting proteins were developmental stage-specific, showing a modulating role of the embryo in protein interactions. Three interacting proteins (OVGP1, ANXA1 and PYGL) were immunolocalized in the perivitelline space and in blastomeres, showing that OF proteins were able to cross the zona pellucida and be taken up by the embryo. Interacting proteins were involved in a wide range of functions, among which metabolism and cellular processes were predominant. This study identified for the first time a high number of oviductal embryo-interacting proteins, paving the way for further targeted studies of proteins potentially involved in the establishment of pregnancy in cattle.

Composing the Early Embryonic Microenvironment: Physiology and Regulation of Oviductal Secretions

The oviductal fluid is the first environment experienced by mammalian embryos at the very beginning of life. However, it has long been believed that the oviductal environment was not essential for proper embryonic development. Successful establishment of in vitro embryo production techniques (which completely bypass the oviduct) have reinforced this idea. Yet, it became evident that in vitro produced embryos differ markedly from their in vivo counterparts, and these differences are associated with lower pregnancy outcomes and more health issues after birth. Nowadays, researchers consider the oviduct as the most suitable microenvironment for early embryonic development and a substantial effort is made to understand its dynamic, species-specific functions. In this review, we touch on the origin and molecular components of the oviductal fluid in mammals, where recent progress has been made thanks to the wider use of mass spectrometry techniques. Some of the factors and processes known to regulate oviductal secretions, including the embryo itself, as well as ovulation, insemination, endogenous and exogenous hormones, and metabolic and heat stress, are summarized. Special emphasis is laid on farm animals because, owing to the availability of sample material and the economic importance of fertility in livestock husbandry, a large part of the work on this topic has been carried out in domestic animals used for dairy and/or meat production.

Metabolomic Profile of Oviductal Extracellular Vesicles across the Estrous Cycle in Cattle

Oviductal extracellular vesicles (oEVs) have been proposed as key modulators of gamete/embryo maternal interactions. The aim of this study was to examine the metabolite content of oEVs and its regulation across the estrous cycle in cattle. Oviductal EVs were isolated from bovine oviducts ipsilateral and contralateral to ovulation at four stages of the estrous cycle (post-ovulatory stage, early and late luteal phases, and pre-ovulatory stage). The metabolomic profiling of EVs was performed by proton nuclear magnetic resonance spectroscopy (NMR). NMR identified 22 metabolites in oEVs, among which 15 were quantified. Lactate, myoinositol, and glycine were the most abundant metabolites throughout the estrous cycle. The side relative to ovulation had no effect on the oEVs' metabolite concentrations. However, levels of glucose-1-phosphate and maltose were greatly affected by the cycle stage, showing up to 100-fold higher levels at the luteal phase than at the peri-ovulatory phases. In contrast, levels of methionine were significantly higher at peri-ovulatory phases than at the late-luteal phase. Quantitative enrichment analyses of oEV-metabolites across the cycle evidenced several significantly regulated metabolic pathways related to sucrose, glucose, and lactose metabolism. This study provides the first metabolomic characterization of oEVs, increasing our understanding of the potential role of oEVs in promoting fertilization and early embryo development.

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.

Equine chorionic gonadotropin increases estradiol levels in the bovine oviduct and drives the transcription of genes related to fertilization in superstimulated cows

In the bovine oviduct, estradiol (E2) stimulates secretion and cell proliferation, whereas progesterone (P4) suppresses them. In this study, we have evaluated the effect of two superstimulatory protocols (follicle-stimulating hormone [FSH] or FSH combined with equine chorionic gonadotropin [eCG]) on the oviductal levels of E2 and P4 and its outcome on oviductal cells. Compared with the control group (a single pre-ovulatory follicle), we have observed that the cows submitted to FSH/eCG treatment showed a higher concentration of E2 in the oviduct tissue, together with a higher abundance of messenger RNA encoding steroid receptors (ESR1 and progesterone receptor), and genes linked to gamete interactions and regulation of polyspermy (oviduct-specific glycoprotein 1, heat-shock protein family A member 5, α-l-fucosidase 1 [FUCA1], and FUCA2) in the infundibulum and ampulla segments of the oviduct. However, we did not observe any modulation of gene expression in the isthmus segment. Even though the FSH protocol upregulated some of the genes analyzed, we may infer that the steady effect of FSH combined with eCG on oviduct regulation might benefit fertilization and may potentially increase pregnancy rates.

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

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

Stage-dependent changes in oviductal phospholipid profiles throughout the estrous cycle in cattle

Sperm capacitation, fertilization and embryo development take place in the oviduct during the periovulatory period of the estrous cycle. Phospholipids are crucial metabolites for sperm capacitation and early embryo development. The aim of this study was to monitor the abundance of phospholipids in the bovine oviductal fluid (OF) according to the stage of the estrous cycle and the side relative to ovulation. Pairs of bovine oviducts were collected in a slaughterhouse and classified into four stages of the estrous cycle: post-ovulatory (Post-ov), mid-luteal (Mid-lut), late-luteal (Late-lut) and pre-ovulatory (Pre-ov) phases (n = 17 cows/stage). Cell-free OF from oviducts ipsilateral and contralateral to the site of ovulation were analyzed using MALDI-TOF mass spectrometry. Lipid identification was achieved by high resolution mass spectrometry. A total of 274 lipid masses were detected in the mass range of 400-1000 Da, corresponding mostly to phosphatidylcholines (PC), lysoPC, phosphatidylethanolamine (PE), lysoPE and sphingomyelins (SM). Ipsilateral and contralateral OF did not differ in their lipid profiles at any stage of the cycle. However, 127 and 96 masses were differentially abundant between stages in ipsilateral and contralateral OF, respectively. Highest differences in lipid profiles were observed in the Pre-ov vs. Mid-lut and Pre-ov vs. Late-lut comparisons in both sides relative to ovulation. Differential abundance of specific molecules of PC, PE, SM and l-carnitine were observed at Pre-ov and Post-ov compared with the luteal phase. This work proposes new candidates potentially able to regulate sperm capacitation and early embryo development.

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.

A novel approach to study the bovine oviductal fluid proteome using transvaginal endoscopy

The oviduct provides the optimal micro milieu for early embryo development. However, accessing the bovine oviductal fluid in vivo for analysis is still challenging and therefore the oviductal fluid is usually collected post mortem. In the study presented here we introduce a novel approach to gain minimal invasive access to the bovine oviductal fluid proteome in vivo by transvaginal endoscopy at different stages of the estrous cycle. The first experiment aimed at transferring C4 derivatised magnetic beads to bind the oviductal fluid proteome in situ. Protein carrying beads were recovered by flushing the oviduct and proteins were eluted. In the second experiment a flushing solution was injected into and aspirated from the oviduct repeatedly. The flushing solution was centrifuged to separate the fluid from the cellular debris. Proteins were identified by nano-LC-MS/MS. Two different stages of the estrous cycle (Day 1 and Day 3) were analyzed in samples from 30 heifers. Both methods were applied successfully and in total, more than 3000 proteins were identified, so far representing the most comprehensive OF proteome published. This new minimal invasive approach to access the bovine oviductal fluid proteome facilitates future innovative experimental designs to study the role of the oviductal micro environment during early embryo development.

Relative effects of location relative to the corpus luteum and lactation on the transcriptome of the bovine oviduct epithelium

Background

Lactation and associated metabolic stresses during the post-partum period have been shown to impair fertility in dairy cows. The oviduct plays key roles in embryo development and the establishment of pregnancy in cattle. The aim of this study was to investigate the effects of lactation and location relative to the corpus luteum (CL) on the transcriptome of the bovine oviduct epithelium.

Results

An original animal model was used. At 60 days post-partum, Holstein lactating (n = 4) and non-lactating (i.e. never milked after calving; n = 5) cows, as well as control nulliparous heifers (n = 5), were slaughtered on Day 3 following induced estrus, and epithelial samples from the oviductal ampulla and isthmus ipsilateral and contralateral to the corpus luteum (CL) were recovered for RNA sequencing. In the oviduct ipsilateral to the CL, differentially expressed genes (DEGs) were identified between heifers compared with both postpartum cow groups. However, only 15 DEGs were identified between post-partum lactating and non-lactating cows in the ipsilateral isthmus and none were identified in the ipsilateral ampulla. In contrast, 192 and 2583 DEGs were identified between ipsilateral and contralateral ampulla and isthmus, respectively. In both regions, more DEGs were identified between ipsilateral and contralateral oviducts in non-lactating cows and heifers than in lactating cows. Functional annotation of the DEGs associated with comparisons between metabolic groups highlighted a number of over-represented biological functions and cell pathways including immune response and cholesterol/steroid biosynthesis.

Conclusions

Gene expression in the oviduct epithelium, particularly in the isthmus, was more affected by the location relative to the CL than by lactation at Day 3 post-estrus. Furthermore, the effect of the proximity to the CL was modulated by the metabolic status of the cow.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5616-2) contains supplementary material, which is available to authorized users.

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.

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

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

Effect of bovine oviductal fluid on motility, tyrosine phosphorylation, and acrosome reaction in cryopreserved bull spermatozoa

This study was conducted to investigate the complex interactions between oviducts and cryopreserved spermatozoa. Herein we report the dynamic changes in bull sperm functions during in vitro incubation with bovine estrus and luteal oviductal fluid. Frozen-thawed bull spermatozoa was incubated either in non-capacitating medium, capacitating medium, non-capacitating medium containing 20% v/v estrus oviductal fluid or non-capacitating medium containing 20% v/v luteal oviductal fluid for 6 h at 38 °C under 5% CO₂. At hourly interval spermatozoa were evaluated for kinematics, tyrosine phosphorylation and acrosome reaction. The sperm velocity parameters were higher (P < 0.05) in capacitating medium compared to the other treatments. At 4 and 5 h of incubation, the proportion of live tyrosine phosphorylated spermatozoa was higher (P < 0.05) in estrus oviductal fluid compared to all other treatments. From 4 to 6 h of incubation the proportion of live acrosome reacted spermatozoa was higher (P < 0.05) in estrus oviductal fluid compared to the other treatments. We conclude that estrus oviductal fluid induced tyrosine phosphorylation and acrosome reaction in a higher proportion of frozen-thawed bull spermatozoa compared to luteal oviductal fluid, although sperm kinematics were not significantly influenced by oviductal during incubation.

Deciphering the oviductal extracellular vesicles content across the estrous cycle: implications for the gametes-oviduct interactions and the environment of the potential embryo

Background

The success of early reproductive events depends on an appropriate communication between gametes/embryos and the oviduct. Extracellular vesicles (EVs) contained in oviductal secretions have been suggested as new players in mediating this crucial cross-talk by transferring their cargo (proteins, mRNA and small ncRNA) from cell to cell. However, little is known about the oviductal EVs (oEVS) composition and their implications in the reproductive success. The aim of the study was to determine the oEVs content at protein, mRNA and small RNA level and to examine whether the oEVs content is under the hormonal influence of the estrous cycle.

Results

We identified the presence of oEVs, exosomes and microvesicles, in the bovine oviductal fluid at different stages of the estrous cycle (postovulatory-stage, early luteal phase, late luteal phase and pre-ovulatory stage) and demonstrated that their composition is under hormonal regulation. RNA-sequencing identified 903 differentially expressed transcripts (FDR < 0.001) in oEVs across the estrous cycle. Moreover, small RNA-Seq identified the presence of different types of ncRNAs (miRNAs, rRNA fragments, tRNA fragments, snRNA, snoRNA, and other ncRNAs), which were partially also under hormonal influence. Major differences were found between post-ovulatory and the rest of the stages analyzed for mRNAs. Interesting miRNAs identified in oEVs and showing differential abundance among stages, miR-34c and miR-449a, have been associated with defective cilia in the oviduct and infertility. Furthermore, functional annotation of the differentially abundant mRNAs identified functions related to exosome/vesicles, cilia expression, embryo development and many transcripts encoding ribosomal proteins. Moreover, the analysis of oEVs protein content also revealed changes across the estrous cycle. Mass spectrometry identified 336 clusters of proteins in oEVs, of which 170 were differentially abundant across the estrous cycle (p-value< 0.05, ratio < 0.5 or ratio > 2). Our data revealed proteins related to early embryo development and gamete-oviduct interactions as well as numerous ribosomal proteins.

Conclusions

Our study provides with the first molecular signature of oEVs across the bovine estrous cycle, revealing marked differences between post- and pre-ovulatory stages. Our findings contribute to a better understanding of the potential role of oEVs as modulators of gamete/embryo-maternal interactions and their implications for the reproductive success.

Electronic supplementary material

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Comparative Proteomic Analysis of Rana chensinensis Oviduct

As one of most important traditional Chinese medicine resources, the oviduct of female Rana chensinensis (Chinese brown frog) was widely used in the treatment of asthenia after sickness or delivery, deficiency in vigor, palpitation, and insomnia. Unlike other vertebrates, the oviduct of Rana chensinensis oviduct significantly expands during prehibernation, in contrast to the breeding period. To explain this phenomenon at the molecular level, the protein expression profiles of Rana chensinensis oviduct during the breeding period and prehibernation were observed using isobaric tags for relative and absolute quantitation (iTRAQ) technique. Then, all identified proteins were used to obtain gene ontology (GO) annotation. Ultimately, KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis was performed to predict the pathway on differentially expressed proteins (DEPs). A total of 4479 proteins were identified, and 312 of them presented different expression profiling between prehibernation and breeding period. Compared with prehibernation group, 86 proteins were upregulated, and 226 proteins were downregulated in breeding period. After KEGG enrichment analysis, 163 DEPs were involved in 6 pathways, which were lysosome, RNA transport, glycosaminoglycan degradation, extracellular matrix (ECM)–receptor interaction, metabolic pathways and focal adhesion. This is the first report on the protein profiling of Rana chensinensis oviduct during the breeding period and prehibernation. Results show that this distinctive physiological phenomenon of Rana chensinensis oviduct was mainly involved in ECM–receptor interaction, metabolic pathways, and focal adhesion.

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

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

Identification by proteomics of oviductal sperm-interacting proteins

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

Metabolomic profiling of bovine oviductal fluid across the oestrous cycle using proton nuclear magnetic resonance spectroscopy

In the present study we tested whether regulation of the metabolome in bovine oviductal fluid depended on the stage of the oestrous cycle, the side relative to ovulation and local concentrations of steroid hormones. Luminal fluid samples from both oviducts were collected in the preovulatory, postovulatory, mid- and late luteal phases, from cyclic cows at a local abattoir (18–27 cows per stage and side). The metabolomes were assessed by proton nuclear magnetic resonance spectroscopy (H-NMR). In all, 39 metabolites were identified, among which the amino acid glycine and the energy substrates lactate and myoinositol were the most abundant at all stages. The concentrations of 14 metabolites varied according to the stage of the oestrous cycle in at least one side relative to ovulation, of which four (choline, glucose-1-phosphate, glycine and pyruvate) were correlated with intraoviductal progesterone or oestradiol concentrations. Glucose-1-phosphate was most affected by the stage of the cycle, with four- to sixfold higher levels in luteal than periovulatory stages. These results provide new knowledge on the regulation of secretory activity in the oviduct and may help optimise culture media for gamete maturation, IVF and embryo production.

Gene expression of bovine embryos developing at the air-liquid interface on oviductal epithelial cells (ALI-BOEC)

We recently developed an air-liquid interface long-term culture of differentiated bovine oviductal epithelial cells (ALI-BOEC). This ex vivo oviduct epithelium is capable of supporting embryo development in co-culture up to the blastocyst stage without addition of embryo culture medium. However, blastocyst rates in co-culture were markedly lower than in conventional in vitro embryo production procedures. In the present study, we assessed target gene expression of ALI-BOEC derived embryos to test their similarity to embryos from conventional in vitro embryo culture. We screened previously published data from developing bovine embryos and selected 41 genes which are either differentially expressed during embryo development, or reflect differences between various in vitro culture conditions or in vitro and in vivo embryos. Target gene expression was measured in 8-cell embryos and blastocysts using a 48.48 Dynamic Array™ on a Biomark HD instrument. For comparison with the ALI-BOEC system, we generated embryos by two different standard IVP protocols. The culture conditions lead to differential gene expression in both 8-cell embryos and blastocysts. Across the expression of all target genes the embryos developing on ALI-BOEC did not depart from conventional IVP embryos. These first results prove that gene expression in ALI-BOEC embryos is not largely aberrant. However, there was no clear indication for a more in vivo-like target gene expression of these embryos. This calls for further optimization of the ALI-BOEC system to increase its efficiency both quantitatively and qualitatively.