Bovine placental extracellular vesicles carry the fusogenic syncytin BERV-K1

Syncytins are endogenous retroviral envelope proteins which induce the fusion of membranes. A human representative of this group, endogenous retrovirus group W member 1 envelope (ERVW-1) or syncytin-1 is present in trophoblast-derived extracellular vesicles and supports the incorporation of these extracellular vesicles into recipient cells. During pregnancy, placenta-derived extracellular vesicles participate in feto-maternal communication. Bovine fetal binucleate trophoblast cells express the syncytin, bovine endogenous retroviral envelope protein K1 (BERV-K1). These cells release extracellular vesicles into the maternal stroma, but it is unclear whether BERV-K1 is included in these extracellular vesicles. Here, extracellular vesicles were isolated from bovine placental tissue using collagenase digestion, ultracentrifugation, and size exclusion chromatography. They were characterized with transmission electron microscopy, nanoparticle tracking analysis, immunoblotting and mass spectrometry. Immunohistochemistry and immunoelectron microscopy were used to localize BERV-K1 within the bovine placental tissue. The isolated extracellular vesicles range between 50 and 300 nm, carrying multiple extracellular vesicle biomarkers. Proteomic analysis and immunoelectron microscopy confirmed BERV-K1 presence on the isolated extracellular vesicles. Further, BERV-K1 was localized on intraluminal vesicles in secretory granules of binucleate trophoblast cells. The presence of BERV-K1 on bovine placental extracellular vesicles suggests their role in feto-maternal communication and potential involvement of BERV-K1 in uptake of extracellular vesicles by target cells.

Characterization of oviduct epithelial spheroids for the study of embryo-maternal communication in cattle

Most in vitro models of oviduct epithelial cells (OEC) used thus far to gain insights into embryo-maternal communication induce cell dedifferentiation or are technically challenging. Moreover, although the presence of developing embryos has been shown to alter gene expression in OEC, the effect of embryos on OEC physiology remains largely unknown. Here, we propose a model based on bovine oviduct epithelial spheroids (OES) with specific shape and diameter (100-200 μm) criteria. The aims of this study were to i) determine the appropriate culture conditions of bovine OES cultured in suspension by evaluating their morphology, total cell number, viability, and activity of ciliated cells; ii) monitor gene expression in OES at the time of their formation (day 0) and over the 10 days of culture; and iii) test whether the vicinity of developing embryos affects OES quality criteria. On day 10, the proportions of vesicle-shaped OES (V-OES) were higher in M199/500 (500 μl of HEPES-buffered TCM-199) and synthetic oviduct fluid (SOF)/25 (25-μL droplet of SOF medium under mineral oil) than in M199/25 (25-μL droplet of M199 under mineral oil). The proportion of viable cells in V-OES was not affected by culture conditions and remained high (>80%) through day 10. The total number of cells per V-OES decreased over time except in SOF/25, while the proportions of ciliated cells increased over time in M199/500 but decreased in M199/25 and SOF/25. The movement amplitude of OES in suspension decreased over time under all culture conditions. Moreover, the gene expression of ANXA1, ESR1, HSPA8, and HSPA1A in OES remained stable during culture, while that of PGR and OVGP1 decreased from day 0 to day 10. Last, the co-culture of developing embryos with OES in SOF/25 increased the rates of blastocysts on days 7 and 8 compared to embryos cultured alone, and increased the proportion of V-OES compared to OES cultured alone. In conclusion, M199/500 and SOF/25 provided the optimal conditions for the long-time culture of OES. The supporting effect of OES on embryo development and of developing embryos on OES morphology was evidenced for the first time. Altogether, these results point OES as an easy-to-use, standardizable, and physiological model to study embryo-maternal interactions in cattle.

Uterine extracellular vesicles as multi-signal messengers during maternal recognition of pregnancy in the mare

In contrast to other domestic mammals, the embryo-derived signal(s) leading to maternal recognition of pregnancy (MRP) are still unknow in the mare. We hypothesize that these embryonic signals could be packed into uterine extracellular vesicles (uEVs), acting as multi-signal messengers between the conceptus and the maternal tract, and contributing to MRP. To unveil these signals, the RNA and protein cargos of uEVs isolated from uterine lavages collected from pregnant mares (P; day 10, 11, 12 and 13 after ovulation) and cyclic control mares (C; day 10 and 13 after ovulation) were analyzed. Our results showed a fine-tuned regulation of the uEV cargo (RNAs and proteins), by the day of pregnancy, the estrous cycle, and even the size of the embryo. A particular RNA pattern was identified with specific increase on P12 related to immune system and hormonal response. Besides, a set of proteins as well as RNAs was highly enriched in EVs on P12 and P13. Differential abundance of miRNAs was also identified in P13-derived uEVs. Their target genes were linked to down- or upregulated genes in the embryo and the endometrium, exposing their potential origin. Our study identified for first time specific molecules packed in uEVs, which were previously associated to MRP in the mare, and thus bringing added value to the current knowledge. Further integrative and functional analyses will help to confirm the role of these molecules in uEVs during MRP in the mare.

Unveiling how vitrification affects the porcine blastocyst: clues from a transcriptomic study

Background

Currently, there is a high demand for efficient pig embryo cryopreservation procedures in the porcine industry as well as for genetic diversity preservation and research purposes. To date, vitrification (VIT) is the most efficient method for pig embryo cryopreservation. Despite a high number of embryos survives in vitro after vitrification/warming procedures, the in vivo embryo survival rates after embryo transfer are variable among laboratories. So far, most studies have focused on cryoprotective agents and devices, while the VIT effects on porcine embryonic gene expression remained unclear. The few studies performed were based on vitrified/warmed embryos that were cultured in vitro (IVC) to allow them to re–expand. Thus, the specific alterations of VIT, IVC, and the cumulative effect of both remained unknown. To unveil the VIT-specific embryonic alterations, gene expression in VIT versus (vs.) IVC embryos was analyzed. Additionally, changes derived from both VIT and IVC vs. control embryos (CO) were analyzed to confirm the VIT embryonic alterations. Three groups of in vivo embryos at the blastocyst stage were analyzed by RNA–sequencing: (1) VIT embryos (vitrified/warmed and cultured in vitro), (2) IVC embryos and (3) CO embryos.

Results

RNA–sequencing revealed three clearly different mRNA profiles for VIT, IVC and CO embryos. Comparative analysis of mRNA profiles between VIT and IVC identified 321, differentially expressed genes (DEG) (FDR < 0.006). In VIT vs. CO and IVC vs. CO, 1901 and 1519 DEG were found, respectively, with an overlap of 1045 genes. VIT-specific functional alterations were associated to response to osmotic stress, response to hormones, and developmental growth. While alterations in response to hypoxia and mitophagy were related to the sum of VIT and IVC effects.

Conclusions

Our findings revealed new insights into the VIT procedure-specific alterations of embryonic gene expression by first comparing differences in VIT vs. IVC embryos and second by an integrative transcriptome analysis including in vivo control embryos. The identified VIT alterations might reflect the transcriptional signature of the embryo cryodamage but also the embryo healing process overcoming the VIT impacts. Selected validated genes were pointed as potential biomarkers that may help to improve vitrification.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00672-1.

Isolation and Characterization of Equine Uterine Extracellular Vesicles: A Comparative Methodological Study

Extracellular vesicles (EVs) have been identified in the uterine fluid in different species and have been pointed as key players in the embryo-maternal dialogue, maternal recognition of pregnancy and establishment of pregnancy. However, little is known about the uterine EVs in the mare. Therefore, the present study aimed at characterizing EVs from uterine lavage of cyclic mares by comparing five EVs isolation methods and the combination of them: (1) ultracentrifugation (UC); (2) concentration of lavage volume by Centricon ultrafiltration (CE); (3) the use of CE with different washing steps (phosphate-buffered saline with or without trehalose); (4) size-exclusion chromatography with iZON-qEV columns, and (5) a combination of the methods with best results based on EVs yield, purity, and protein cargo profiles. Transmission electron microscopy and Western blotting confirmed the isolation of EVs by all methods but with quantitative and qualitative differences. Mass spectrometry provided differences in protein profiles between methods, number of identified proteins, and protein classes. Our results indicate that the combination of CE/trehalose/iZON/UC is an optimal method to isolate equine uterine EVs with good yield and purity that can be applied in future studies to determine the role of equine uterine EVs in embryo-maternal interactions.

Oviduct fluid extracellular vesicles regulate polyspermy during porcine in vitro fertilisation

High polyspermy is one of the major limitations of porcine invitro fertilisation (IVF). The addition of oviductal fluid (OF) during IVF reduces polyspermy without decreasing the fertilisation rate. Because extracellular vesicles (EVs) have been described as important OF components, the aim of this study was to evaluate the effect of porcine oviductal EVs (poEVs) on IVF efficiency compared with porcine OF (fresh and lyophilised). OF was collected from abattoir oviducts by phosphate-buffered saline flush, and poEVs were isolated by serial ultracentrifugation. Four IVF treatments were conducted: poEVs (0.2mgmL-1), OF (10%), lyophilized and reconstituted pure OF (LOF; 1%) and IVF without supplementation (control). Penetration, monospermy and IVF efficiency were evaluated. Transmission electron microscopy showed an EVs population primarily composed of exosomes (83%; 30-150nm). Supplementation with poEVs during IVF increased monospermy compared with control (44% vs 17%) while maintaining an acceptable penetration rate (61% vs 78% respectively) in a similar way to OF and LOF. Western blotting revealed poEVs proteins involved in early reproductive events, including zona pellucida hardening. In conclusion, our finding show that poEVs are key components of porcine OF and may play roles in porcine fertilisation and polyspermy regulation, suggesting that supplementation with poEVs is a reliable strategy to decrease porcine polyspermy and improve invitro embryo production outcomes.

Protein Cargo of Extracellular Vesicles From Bovine Follicular Fluid and Analysis of Their Origin From Different Ovarian Cells

Follicular fluid (FF) fills the interior portion of the ovarian antral follicle and provides a suitable microenvironment for the growth of the enclosed oocyte through molecular factors that originate from plasma and the secretions of follicular cells. FF contains extracellular nanovesicles (ffEVs), including 30-100-nm membrane-coated exosomes, which carry different types of RNA, proteins, and lipids and directly influence oocyte competence to develop embryo. In the present study, we aimed to characterize the protein cargo of EVs from the FF of 3-6-mm follicles and uncover the origins of ffEVs by assessing expression levels of corresponding mRNAs in bovine follicular cells and oocyte and cell proteomes. Isolated exosome-like ffEVs were 53.6 + 23.3 nm in size and could be internalized by cumulus-oocyte complex. Proteomes of ffEVs and granulosa cells (GC) were assessed using nanoflow liquid chromatography coupled with high-resolution tandem mass spectrometry after the gel fractionation of total proteins. In total, 460 protein isoforms corresponding to 322 unique proteins were identified in ffEVs; among them, 190 were also identified via GC. Gene Ontology terms related to the ribosome, protein and RNA folding, molecular transport, endocytosis, signal transduction, complement and coagulation cascades, apoptosis, and developmental biology pathways, including PI3K-Akt signaling, were significantly enriched features of ffEV proteins. FfEVs contain numerous ribosome and RNA-binding proteins, which may serve to compact different RNAs to regulate gene expression and RNA degradation, and might transfer ribosomal constituents to the oocyte. Majority of genes encoding ffEV proteins expressed at different levels in follicular cells and oocyte, corroborating with numerous proteins, which were reported in bovine oocyte and cumulus cells in other studies thus indicating possible origin of ffEV proteins. The limited abundance of several mRNAs within follicular cells indicated that corresponding ffEV proteins likely originated from circulating exosomes released by other tissues. Analysis of bovine ffEV transcriptome revealed that mRNAs present in ffEV accounted for only 18.3% of detected ffEV proteins. In conclusion, our study revealed numerous proteins within ffEVs, which originated from follicular and other cells. These proteins are likely involved in the maintenance of follicular homeostasis and may affect oocyte competence.

Embryo-Maternal Interactions Underlying Reproduction in Mammals

This Special Issue, “Embryo-Maternal Interactions Underlying Reproduction in Mammals”, gathers a collection of 23 articles, 16 original research articles and 7 up-to-date reviews, providing new findings or summarizing current knowledge on embryo–maternal interactions in seven different mammalian species including humans. Considering the different players involved in these embryo-maternal interactions, articles are mainly focused on one of these different players: the oviduct, the uterus, the embryo or the emergent extracellular vesicles. Additionally, a few articles bring up the impact of reproductive, but also non-reproductive, diseases, as well as stress factors, on the establishment of pregnancy. We hope the readers enjoy this collection of articles and that the knowledge assembled here will support and inspire current and future research investigations. We would like to thank all authors for their contributions to this Special Issue.

Extracellular vesicles: Multi-signal messengers in the gametes/embryo-oviduct cross-talk

Extracellular vesicles (EVs) have emerged as novel cell-to-cell communication mediators in physiological and pathological scenarios. Their ability to transfer their molecular cargo (RNAs, proteins and lipids) from one cell to another, in the vicinity or far from the cell of origin, together with their capacity of exerting a functional impact on the target cell make them valuable diagnostic tools as well as therapeutic vectors in a variety of diseases. In the reproductive field, there is a growing interest in the role of EVs in gamete/embryo-maternal communication and their potential implications in the reproductive success. In this review, we provide current knowledge of EVs secreted by the oviduct (oEVs) and embryos (eEVs), since both have been proposed as key players in the crucial two-way dialogue between the oviduct (lining epithelium and secretions) and the embryo that ensures successful pregnancy. Both oEVs and eEVs molecular cargos and their potential role as multi-signal messengers in the gametes/embryo-oviduct cross-talk and in the embryo-to-embryo communication in different species are also addressed. Eventually, a comparative analysis between oEVs and eEVs has been performed to shed some light on common and specific cargos responsible for their functions supporting the early reproductive events and as prime candidate molecules for improving fertility and assisted reproductive technologies outcomes.

The Oviductal Extracellular Vesicles' RNA Cargo Regulates the Bovine Embryonic Transcriptome

Oviductal extracellular vesicles (oEVs) are emerging as key players in the gamete/embryo–oviduct interactions that contribute to successful pregnancy. Various positive effects of oEVs on gametes and early embryos have been found in vitro. To determine whether these effects are associated with changes of embryonic gene expression, the transcriptomes of embryos supplemented with bovine fresh (FeEVs) or frozen (FoEVs) oEVs during in vitro culture compared to controls without oEVs were analyzed by low-input RNA sequencing. Analysis of RNA-seq data revealed 221 differentially expressed genes (DEGs) between FoEV treatment and control, 67 DEGs for FeEV and FoEV treatments, and minor differences between FeEV treatment and control (28 DEGs). An integrative analysis of mRNAs and miRNAs contained in oEVs obtained in a previous study with embryonic mRNA alterations pointed to direct effects of oEV cargo on embryos (1) by increasing the concentration of delivered transcripts; (2) by translating delivered mRNAs to proteins that regulate embryonic gene expression; and (3) by oEV-derived miRNAs which downregulate embryonic mRNAs or modify gene expression in other ways. Our study provided the first high-throughput analysis of the embryonic transcriptome regulated by oEVs, increasing our knowledge on the impact of oEVs on the embryo and revealing the oEV RNA components that potentially regulate embryonic development.

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.

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.

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

The online version of this article (10.1186/s12864-018-4982-5) contains supplementary material, which is available to authorized users.

Oviduct extracellular vesicles protein content and their role during oviduct-embryo cross-talk

Successful pregnancy requires an appropriate communication between the mother and the embryo. Recently, exosomes and microvesicles, both membrane-bound extracellular vesicles (EVs) present in the oviduct fluid have been proposed as key modulators of this unique cross-talk. However, little is known about their content and their role during oviduct-embryo dialog. Given the known differences in secretions by in vivo and in vitro oviduct epithelial cells (OEC), we aimed at deciphering the oviduct EVs protein content from both sources. Moreover, we analyzed their functional effect on embryo development. Our study demonstrated for the first time the substantial differences between in vivo and in vitro oviduct EVs secretion/content. Mass spectrometry analysis identified 319 proteins in EVs, from which 186 were differentially expressed when in vivo and in vitro EVs were compared (P < 0.01). Interestingly, 97 were exclusively expressed in in vivo EVs, 47 were present only in in vitro and 175 were common. Functional analysis revealed key proteins involved in sperm-oocyte binding, fertilization and embryo development, some of them lacking in in vitro EVs. Moreover, we showed that in vitro-produced embryos were able to internalize in vivo EVs during culture with a functional effect in the embryo development. In vivo EVs increased blastocyst rate, extended embryo survival over time and improved embryo quality. Our study provides the first characterization of oviduct EVs, increasing our understanding of the role of oviduct EVs as modulators of gamete/embryo-oviduct interactions. Moreover, our results point them as promising tools to improve embryo development and survival under in vitro conditions.

78 INTERCEPTION OF EXOSOMAL MESSAGES BETWEEN THE OVIDUCT AND THE EMBRYO: WHAT ARE THEY TWEETING ABOUT?

Successful pregnancy requires an appropriate communication between the mother and the embryo(s). Recent studies indicate that exosomes, small (30–100 nm) membrane-bound vesicles of endocytotic origin, could act as intercellular vehicles in this unique communication system in the uterus. However, little is known about the role of these vesicles in the oviduct. Our study aimed at (1) demonstrating the existence of oviducal-embryo communication via exosomes, (2) deciphering the exosomal dialogue between them at the proteomic level, and (3) comparing the exosomal proteomic content to the oviducal fluid proteomic content in order to highlight the key role of exosomes in this dialogue. Cow oviducts (pool of 6 oviducts at different stages of the cycle in 4 replicates) were flushed, and exosomes were isolated by serial ultracentrifugation. Exosomes were measured by dynamic light scattering analysis, resulting in exosomes (63.25–97.03 nm) and microvesicle observations (>100 nm). Bovine embryos were produced in vitro up to the blastocyst and hatching/hatched blastocyst stages. To demonstrate the existence of the oviducal-embryo communication via exosomes, oviducal exosomes were labelled with green fluorescent dye (PKH67), filtered (0.22 µm) to remove microvesicles, and co-incubated with blastocysts and hatching/hatched (H) blastocysts for 20 h, under 5% CO2 and 5% O2 conditions. Subsequently, embryos were washed in exosome-free medium, fixed in 4% paraformaldehyde, and labelled with Hoechst 33342 and Actin Red Phallodin. Confocal microscopy observations confirmed that exosomes were internalized by blastocysts and H-blastocysts and located around the nucleus, demonstrating the existence of an oviducal-embryo communication via exosomes. Moreover, our results showed that the zona pellucida does not represent a barrier for exosomes and they act as natural nanoshuttles bringing oviducal signals into the embryo. Then, proteomic analysis by LC1D-nanoESI-LTQ-Orbitrap was used to decipher oviducal exosomal content, identifying 480 proteins. Gene ontology analysis revealed that a high number of these proteins were involved in metabolism (24.9%), cellular process (19.3%), and 0.8% reproductive processes. Further analysis revealed that more than 56% of exosomal proteins involved in cellular process were associated with cell-to-cell communication. Finally, exosomal proteins were compared with proteins present in oviducal fluid from a pool of samples from cows at Day 0 and Day 10 of the oestrous cycle. Comparative analysis showed that from a total of 607 proteins identified in both oviducal exosomes and fluid sources, 105 were specific to exosomes, 127 were specific to fluid, whereas 375 were common to both sources. Our findings provide the first evidence of oviducal-embryo communication via exosomes, an important first step in furthering the understanding of the oviducal environment and the role of exosomes as early mediators of embryo-maternal cross talk. This research was supported by the EU AgreenSkills fellowship n° 267196 and EU FECUND Project no 312097.

108 CHARACTERIZATION OF BOVINE OVIDUCTAL EXOSOMES FROM IN VIVO AND IN VITRO ORIGIN

Successful pregnancy requires an appropriate communication between the mother and the embryo(s). Recent studies indicate that exosomes, small (30–200 nm) membrane vesicles of endocytotic origin, could act as intercellular vehicles in this unique communication system. Exosomes have been identified in vivo in all body fluids including follicular, uterine, and oviductal fluids and can be secreted by most cell types in vitro. Bovine oviductal epithelial cells (BOEC) have been thoroughly used to study embryo-maternal communication and to improve embryo development in vitro. Hence, our objective was to provide a morphologic and proteomic characterisation of exosomes secreted by BOEC in vivo in the oviductal fluid and in vitro in the conditioned media. Oviducts from cows were flushed to recover in vivo exosomes and then BOEC were scraped in order to derive primary cultures. In vitro exosomes were collected from conditioned media of BOEC primary cultures after reaching confluence (10 days). Isolation of exosomes from in vivo and in vitro origin was performed by ultracentrifugation. The presence of exosomes was confirmed in oviductal flushings and conditioned media by electron microscopy. Further characterisation of exosomes was carried out based on morphology (transmission electron microscopy), size (dynamic light scattering, DLS), and protein composition (protein profile analysis by SDS-PAGE and Western immunoblotting). Preliminary results by DLS revealed different size distribution profiles in exosome samples (in vivo: mean size of 93.41 nm; in vitro: 433.5 nm). Because exosomes are considered as “micromaps” of the originating cells, protein patterns expressed by in vivo exosomes and in vitro exosomes were compared with scraped and cultured BOEC, respectively. Protein profile analysis by SDS-PAGE showed quantitative and qualitative differences among the exosome samples, their cells of origin, and the milieu (conditioned media or flushing). Exosome-specific protein bands were detected and will be further characterised. In addition, exosomes from in vivo and in vitro origin exhibited distinct proteomic profiles. Western blot analysis demonstrated that (1) both exosomal protein samples were positive for HSP70, a known exosomal protein, and negative for Grp78, an endoplasmic reticulum marker detected in BOEC; (2) in vivo exosomes expressed oviductal glycoprotein (OVGP), heat shock protein A8 (HSPA8), and myosin 9 (MYH9), 3 oviductal proteins with known roles in fertilization and early pregnancy. However, only HSPA8 and MYH9 were detected in in vitro exosomes. Our results provide the first extensive characterisation of oviductal exosomes from in vivo and in vitro origin, an essential step in furthering our understanding of the early embryo-maternal cross talk.

The battle of the sexes starts in the oviduct: modulation of oviductal transcriptome by X and Y-bearing spermatozoa

BACKGROUND

Sex allocation of offspring in mammals is usually considered as a matter of chance, being dependent on whether an X- or a Y-chromosome-bearing spermatozoon reaches the oocyte first. Here we investigated the alternative possibility, namely that the oviducts can recognise X- and Y- spermatozoa, and may thus be able to bias the offspring sex ratio.

RESULTS

By introducing X- or Y-sperm populations into the two separate oviducts of single female pigs using bilateral laparoscopic insemination we found that the spermatozoa did indeed elicit sex-specific transcriptomic responses. Microarray analysis revealed that 501 were consistently altered (P-value < 0.05) in the oviduct in the presence of Y-chromosome-bearing spermatozoa compared to the presence of X-chromosome-bearing spermatozoa. From these 501 transcripts, 271 transcripts (54.1%) were down-regulated and 230 transcripts (45.9%) were up-regulated when the Y- chromosome-bearing spermatozoa was present in the oviduct. Our data showed that local immune responses specific to each sperm type were elicited within the oviduct. In addition, either type of spermatozoa elicits sex-specific signal transduction signalling by oviductal cells.

CONCLUSIONS

Our data suggest that the oviduct functions as a biological sensor that screens the spermatozoon, and then responds by modifying the oviductal environment. We hypothesize that there might exist a gender biasing mechanism controlled by the female.

Seminal plasma proteins as modulators of the sperm function and their application in sperm biotechnologies

Seminal plasma (SP) is known to play an important role in mammalian fertilization. However, the variability found in its composition among species, males and even fractions of the same ejaculate has made difficult to completely understand its effect in sperm function. Proteins are one of the major SP components that modulate sperm functionality. During the last years, intensive work has been performed to characterize the role of these proteins. They have been found to influence sperm capacitation, formation of the oviductal sperm reservoir and sperm-oocyte interaction. Sperm biotechnologies, such as sperm cryopreservation and flow cytometric sex-sorting, that involve a substantial dilution of the SP are detrimental to sperm quality. Attempts to improve the outcome of these biotechnologies include the restoration of SP, which has produced contradictory results. To overcome this variability, different research groups have proposed the application of isolated SP proteins. Herein, we will review the current knowledge in the role of the major SP proteins as modulators of sperm functionality. Furthermore, we will discuss the possible applications of the SP proteins in sperm cryopreservation and flow cytometric sex-sorting.

Exploring the application of high-throughput genomics technologies in the field of maternal-embryo communication

Deciphering the complex molecular dialogue between the maternal tract and embryo is crucial to increasing our understanding of pregnancy failure, infertility problems and in the modulation of embryo development, which has consequences through adulthood. High-throughput genomic technologies have been applied to look for a holistic view of the molecular interactions occurring during this dialogue. Among these technologies, microarrays have been widely used, being one of the most popular tools in maternal-embryo communication. Today, next generation sequencing technologies are dwarfing the capabilities of microarrays. The application of these new technologies has broadened to almost all areas of genomics research, because of their massive sequencing capacity. We review the current status of high-throughput genomic technologies and their application to maternal-embryo communication research. We also survey next generation technologies and their huge potential in many research areas. Given the diversity of unanswered questions in the field of maternal-embryo communication and the wide range of possibilities that these technologies offer, here we discuss future perspectives on the use of these technologies to enhance maternal-embryo research.

Pentoxifylline added to freezing or post-thaw extenders does not improve the survival or in vitro fertilising capacity of boar spermatozoa

This study evaluated whether pentoxifylline added to freezing and thawing extenders influenced the function of boar spermatozoa. In Experiment 1, pooled ejaculated sperm-rich fractions were frozen in 0.5 ml straws after dilution in extender supplemented with pentoxifylline to a final concentration of 0, 2, 4, 8, 16 or 32 mM. The addition of 4, 8, 16 and 32 mM pentoxifylline to the freezing extender significantly decreased the progressive and total motility of spermatozoa. The percentage of viable spermatozoa with intact acrosomes as well as the penetration rate and the efficiency of fertilisation were significantly lower in pentoxifylline-treated groups compared with the untreated control. In Experiment 2, a pool of three straws with ‘good’ post-thaw sperm quality parameters and another three straws with ‘poor’ sperm quality were diluted in extender with 0, 1, 2, 4, 8, 16 or 32 mM pentoxifylline. Post-thaw samples with both ‘good’ and ‘poor’ sperm quality with 0, 2, 4, 8 and 16 mM were used to assess IVF parameters. The addition of pentoxifylline to post-thaw extender did not improve the post-thaw motility or viability of spermatozoa compared with the control. The in vitro penetration was higher (P<0.05) than the control for oocytes fertilised with spermatozoa that were thawed and incubated in extender with 4, 8 and 16 mM pentoxifylline. However, no differences were observed in the efficiency of fertilisation. We conclude that pentoxifylline, as a supplement added to the freezing extender, has a deleterious effect and that it does not improve the survival or in vitro fertilising efficiency of frozen–thawed boar spermatozoa when added after thawing.

335 EFFECT OF MEM VITAMINS AND FORSKOLIN ON IN VITRO EMBRYO PRODUCTION AND SOPS-VITRIFICATION ABILITY OF IN VITRO DERIVED PORCINE BLASTOCYSTS

The aims of this study were, first to investigate the effect of minimum essential medium (MEM) vitamins (VITs) during IVM of porcine oocytes on in vitro embryo production of porcine embryos and second, to determine if the addition of VITs during IVM and the chemical delipidation with forskolin improve the vitrification ability of in vitro-derived porcine blastocysts. COCs were divided in two groups and matured in NCSU-23 for 44 h with 0.05% VITs (V group) or without VITs (NV group). Matured oocytes were inseminated with frozen-thawed spermatozoa. Presumptive zygotes were cultured for 16 h to assess IVF parameters (N = 767) or for 6 days (N = 2858) to evaluate the in vitro embryo development (Day 0 = day of IVF). On Day 5, some embryos from NV and V groups were cultured for 24 h with 10 μM forskolin (NVF and VF groups). The remaining embryos were cultured without forskolin (NVNF and VNF groups). On Day 6, embryos from the four experimental groups were assessed for blastocysts formation and some blastocysts (N = 414) were vitrified using superfine open pulled straws (SOPS). Vitrified blastocysts were warmed (one-step dilution method) and cultured for 24 h to assess their viability. Blastocysts with totally or partially reformed blastocoel cavity and normal or excellent morphology were considered viable. Five replicates of a 2 × 2 factorial design were conducted. Data was analyzed with the MIXED procedure. The threshold for significance was set at P < 0.05. Results are expressed as least squares means ± SEM. No differences were observed in the maturation of COCs treated with VITs (92.7 ± 1.3%) and non-treated COCs (94.3 ± 1.3%). The NV and V maturation groups showed similar penetration (83.0 ± 3% and 82.6 ± 3%, respectively) and monospermy (48.9 ± 6%, and 48.3 ± 6%, respectively) rates. The rate of monosermic oocytes related to the total of analyzed oocytes was similar for NV (38.1 ± 3.7%) and V (38.4 ± 3.7%) groups. The values of cleavage rate on Day 2 were similar for NV (66.7 ± 1.5%) and V (69.6 ± 1.6%) embryos. The addition of VITs to IVM medium improved (P < 0.01) up to 10 points the blastocysts formation rate, but the addition of forskolin at Day 5 did not affect this parameter. The V group showed a higher (P < 0.01) blastocysts rate (45.1 ± 2.5%) than the NV group (38.4 ± 2.3%).The addition of VITs did not affect the survival of in vitro-derived blastocysts after SOPS-vitrification on Day 6. However, the blastocysts cultured for 24 h with forskolin showed higher (P < 0.05) viability (44.0 ± 7.9%) after vitrification and warming than those embryos cultured without forskolin (34.1 ± 7.8%). In conclusion, the addition of MEM vitamins to IVM medium improves the blastocysts formation rate and the chemical delipidation with forskolin improve the cryosurvival of SOPS-vitrified porcine in vitro-derived blastocysts. This study was supported by the Seneca foundation of Murcia (GERM 04543/07), MICINN (AGL2009-12091 and RC-2007), and CARM (2I05SU0012).

Superfine open pulled straws vitrification of porcine blastocysts does not require pretreatment with cytochalasin B and/or centrifugation

The present study investigated the in vitro development of and cytoskeletal disruption suffered by in vivo-derived porcine blastocysts subjected to superfine open pulled straws (SOPS) vitrification. Blastocysts were either untreated prior to SOPS vitrification or were subjected to one of the following three pretreatment protocols: (1) centrifugation (12 min, 13 000g); (2) 25 min equilibration with 7.5 μg mL–1 cytochalasin B; or (3) equilibration with cytochalasin B followed by centrifugation. After 24 h culture, fresh (n = 32) and vitrified–warmed (n = 188) blastocysts were evaluated by stereomicroscopy, with survival and hatching rates recorded. Some blastocysts were stained with 4′,6′-diamidino-2-phenylindole and processed for cytoskeletal evaluation. Three cytoskeletal patterns were identified: Grade I, intact cytoskeleton; Grade II, gross maintenance of integrity, but with some clumps of actin within the cytoplasm; and Grade III, a highly disrupted cytoskeleton. There were no differences in the survival, hatching and cell death rats, total cell number or cytoskeletal integrity between the different vitrification groups. Cell death was greater for vitrified blastocysts than for fresh blastocysts (3.6 ± 0.4% v. 0.4 ± 0.7%, respectively; P < 0.05) and the percentage of blastocysts with a Grade I cytoskeletal pattern was lower for vitrified compared with fresh blastocysts (60.8% v. 92%, respectively; P < 0.05). The vitrified–warmed blastocysts that hatched during culture exhibited a Grade I cytoskeletal pattern. In conclusion, successful SOPS vitrification of porcine blastocysts does not require pretreatment with cytochalasin B and/or centrifugation.

Vitrification and warming of in vivo-derived porcine embryos in a chemically defined medium

The aim of this study was to design a protocol for vitrification and warming of porcine embryos in a chemically defined medium. A total of 663 morulae and blastocysts were collected from weaned crossbred sows (Large White-Landrace) 5 to 6 d after estrus and vitrified with the Superfine Open Pulled Straw method. In Experiment 1, embryos were vitrified using as a basic medium TCM-199-HEPES supplemented with 20% newborn calf serum (NBCS) or with 0, 0.1%, 0.5%, or 1% polyvinyl alcohol (PVA). Nonvitrified embryos were used as a fresh control group. Survival and hatching rates were evaluated after 72 h of in vitro culture to assess embryo viability. In addition, some hatched blastocysts derived from morulae and blastocysts were processed to determine the total cell number and the cell proliferating index as measures of their quality. Within each stage of embryo development, the different vitrification groups and the fresh control group showed similar high embryo survival (range, 70.5+/-7.1% to 84.9+/-8.1% and 85.3+/-8.1% to 98.4+/-8.2% for morulae and blastocysts, respectively) and hatching rate (range, 46.3+/-10.1% to 66.7+/-11.2% and 73.7+/-11.3% to 89.4+/-11.2% for morulae and blastocysts, respectively) and quality after in vitro culture. In Experiment 2, embryos were vitrified using 0.1% PVA and warmed with TCM-199-HEPES-0.13 M sucrose supplemented with 20% NBCS or either 0 or 0.1% PVA. Nonvitrified embryos were used as a fresh control group. As in Experiment 1, no significant differences were detected in embryo survival (range, 67.9+/-6.6% to 74.5+/-6.6% and 91.9+/-7.0% to 99.5+/-6.3% for morulae and blastocysts, respectively) and hatching rate (range, 47.0+/-7.2% to 64.8+/-9.9% and 89.4+/-7.4% to 98.2+/-6.9% for morulae and blastocysts, respectively) and quality among the warming groups or among vitrified and fresh control embryos. In both experiments, the developmental embryo stage influenced the survival and hatching rates, as well as the number of cells (P<0.01), with the blastocyst stage yielding the best results. In conclusion, PVA can be used as a substitute for serum in vitrification and warming solutions without detrimental effects on the in vitro development of in vivo-derived porcine morulae and blastocysts.

Pre-pubertal Di(2-ethylhexyl) Phthalate (DEHP) Exposure of Young Boars Did Not Affect SpermIn vitroPenetration Capacity of Homologous Oocytes Post-puberty

Di(2-ethylhexyl) phthalate (DEHP), a plastic softener used in polyvinylchloride (PVC) products (e.g., plastic bags and medical equipment), has been reported to have toxic effects on animal reproduction and is considered an environmental hazard based, mostly, on rodent studies. However, the doses used in these studies are often considerably higher than that presumed in human exposure. In the present study we used young boars as model animals to assess the effects of pre-pubertal DEHP exposure on the ability of spermatozoa to penetrate homologous oocytes in vitro. Eight pairs of cross-bred male boar siblings were used. One brother in each pair became, at random, the test animal exposed to DEHP per os, three times a week, from 3 to 7 weeks of age while the other acted as the control, i.e., placebo-exposed. Semen was collected and frozen between 8 and 9 months of age and stored until spermatozoa were evaluated for their ability to in vitro penetrate in vitro-matured homologous oocytes post-thaw. Both the penetration rate and the number of spermatozoa per oocyte were considered within expected ranges for frozen boar semen of good quality. Penetration rate did not significantly differ (p > 0.05) between the groups with DEHP-exposed: 50%; control: 59%, which could be owing to a large variation between boars, and between replicates. The number of spermatozoa in the ooplasm was low and similar (p > 0.05) between the groups with DEHP-exposed: 1.5 and the control: 1.7. Under the conditions of the present experiment, pre-pubertal exposure to DEHP does not seem to cause a deleterious effect on the in vitro fertilizing ability of frozen spermatozoa post-puberty.

In vitro maturation of porcine oocytes with retinoids improves embryonic development

In the present study, the effects of retinoid metabolite administration during in vitro maturation (IVM) on oocyte maturation, parameters of in vitro fertilisation (IVF) and embryo development were examined. Varying concentrations of 9-cis retinoic acid (RA; 0, 5, 50 and 500 nm; Experiment 1) and all-trans retinol (ROH; 0, 125, 1250 and 12 500 nm; Experiment 2) were included in the maturation medium. Cumulus-oocyte complexes were matured in vitro and inseminated with frozen-thawed spermatozoa. Presumptive zygotes were cultured for 16 h to assess IVF parameters or for 7 days to assess embryo development and quality. In Experiment 1, the oocyte maturation rate to metaphase II was significantly decreased (P < 0.001), with values below 5%, in the presence of the highest concentration of RA (500 nm). However, 5 and 50 nm RA had no effect compared with control. Treatment with 5 nm RA improved the blastocyst development rate (P < 0.001). In Experiment 2, the oocyte maturation rate did not differ between 125 and 1250 nm ROH treatment groups and control. However, treatment with 12 500 nm ROH was deleterious because no matured oocytes were observed following the treatment. The penetration rate was lower in the group treated with 1250 nm ROH compared with the 125 nm ROH-treated and control groups, but the blastocyst formation rate did not differ among the three groups. In conclusion, 5 nm RA in the IVM medium significantly increased the blastocyst formation rate, suggesting that RA may play an important role during IVM.

Effects of ultrashort gamete co-incubation time on porcine in vitro fertilization

A reduction in co-incubation time has been suggested as an alternative method to reduce polyspermic fertilization. The aim of this study was to evaluate the effect of short periods of gamete co-incubation during pig in vitro fertilization. A total of 2,833 in vitro matured oocytes were inseminated with thawed spermatozoa and coincubated for 0.25, 1, 2, 3, 7, 10 min and 6h. The oocytes from the 0.25-10 min groups were washed three times in modified Tris-buffered medium (mTBM) medium to remove spermatozoa not bound to the zona and transferred to the same medium (containing no spermatozoa) until 6h of co-incubation time were completed. After 6h, presumptive zygotes from each group were cultured in NCSU-23 medium for 12-15 h to assess fertilization parameters. After each period of co-incubation, 45-50 oocytes from each group were stained with Hoechst-33342 and the number of spermatozoa bound to the zona was counted. Although the number of zona bound spermatozoa increased (p<0.05) with the co-incubation time, no increase was observed in penetration rates among groups from 2 min to 6h of co-incubation time (ranging from 53.5+/-2.8 to 61.3+/-2.6%). Similarly, the efficiency of fertilization reached a maximum for the 2 min of co-incubation group with values ranging between 32.3+/-2.4 and 41.9+/-2.5%. The reduction of co-incubation time did not affect the monospermy rate (range: 71.3+/-3.4-80.2+/-3.8%) and the mean number of spermatozoa/oocyte (range: 1.2+/-0.4-1.4+/-0.5). These results show that, under our in vitro conditions, high penetration rate can be obtained with co-incubation times as short as 2 min, although monospermy could not be improved using this strategy.

PSP-I/PSP-II spermadhesin exert a decapacitation effect on highly extended boar spermatozoa

PSP-I/PSP-II heterodimer is a major protein of boar seminal plasma that is able to preserve, in vitro, the viability, motility and mitochondrial activity of highly-extended boar spermatozoa. However, a relationship between the protective effects of the heterodimer and sperm capacitation is still unclear. The present study investigated the effect of the PSP-I/PSP-II (1.5 mg/mL) on membrane stability, intracellular calcium concentration ([Ca(2+)](I)) and plasma membrane and acrosome integrity of highly extended boar spermatozoa. Boar spermatozoa were diluted to 1 x 10(6) spermatozoa/mL and incubated at 38 degrees C in Phosphate-buffered saline (PBS) for 10, 30, 60, 120 and 300 min or in modified Tris-buffered medium (mTBM) for 10, 20, 30, 60 and 120 min. After each incubation time, the membrane stability (using Merocyanine-540/Yo-Pro-1), elevation of [Ca(2+)](I) (using Fluo-3-AM/PI) and the sperm plasma membrane and acrosome integrity (using SYBR-14/PI/PE-PNA) were evaluated by flow cytometry. As expected, exposure of the spermatozoa to the PSP-I/PSP-II preserved the plasma membrane and acrosome integrity compared to non-exposed spermatozoa in both media PBS and mTBM (p < .01). The evaluation of membrane stability showed no differences in the percentages of viable sperm with instable plasma membrane in the presence of the PSP-I/PSP-II compared to controls irrespective of the dilution media. The evaluation of the [Ca(2+)](I) levels showed that while spermatozoa incubated in mTBM and exposed to PSP-I/PSP-II had lower [Ca(2+)](I) than controls (39.08% vs. 47.97%, respectively; p < .05), no differences were observed in those samples incubated in PBS. However, a temporal evaluation of the samples showed that a similar proportion of live spermatozoa were able to achieve high levels of [Ca(2+)](I) and membrane instability independent of the presence of PSP-I/PSP-II. In conclusion, PSP-I/PSP-II exert a non-permanent decapacitation effect on highly extended boar spermatozoa that is related with a delay in the increase of [Ca(2+)](I) levels.

70 EFFECT OF CRYOPROTECTANT CONCENTRATION ON THE IN VITRO SURVIVAL AND CELL PROLIFERATION OF PORCINE BLASTOCYSTS VITRIFIED USING THE OPEN PULLED STRAW SYSTEM

The objective of the present project was to study the effect of the concentrations of ethylene glycol (EG) and dimethyl sulfoxide (DMSO) during vitrification on the survival and hatching rates of porcine blastocysts. Embryos were collected by laparotomy from weaned crossbred sows (n = 18), vitrified, and warmed (one-step dilution) as described by Cuello et al. (2004 Theriogenology 62, 1144–1152). Vitrification was performed in different concentrations of EG and DMSO (15%, 16%, and 17% v/v for each cryoprotectant) or in an EG-based medium (40% v/v) using superfine open pulled straws. Fresh and vitrified blastocysts were cultured for 24 h in TCM199 and assessed by stereomicroscopy during the culture. Blastocysts that reformed their blastocoelic cavities after warming, displaying a normal zona pellucida and excellent appearance, were considered viable. The in vitro survival rate was defined as the ratio of viable embryos divided by the total number of embryos cultured. The hatching rate is determined as the ratio of the number of embryos hatched in vitro to the total number embryos cultured. Some vitrified and fresh embryos classified as viable were processed for Hoechst 33342 staining and proliferation cell nuclear antigen (PCNA) inmunolocalization. The proliferation index was defined as the number of PCNA-positive nuclei divided by the total number of nuclei stained with Hoechst 33342. Data were analyzed by ANOVA using the MIXED procedure (SPSS version 11.5; SPSS, Inc., Chicago, IL, USA). Data were expressed as mean values � SEM. The survival rate was similar for fresh and vitrified blastocysts, except for blastocysts vitrified using 15% cryoprotectants, which displayed a lower (P < 0.05) survival rate (84.2 � 4.8%) than fresh blastocysts (94.6 � 5%) and blastocysts vitrified using 40% EG, 16%, or 17% EG-DMSO (88.8 � 4.9, 96.8 � 4.9, and 96.4 � 5%, respectively). Fresh blastocysts showed a higher (P < 0.05) hatching rate (80.7 � 4.5%) than their vitrified counterparts (range: 48.4 � 7.7–55.3 � 7.8%). Vitrified and fresh blastocysts showed similar cell proliferation indexes (range: 75.8 � 3.2–83.7 � 3). When only hatched blastocysts among groups were compared, the proliferation rate decreased (P < 0.05) after vitrification with 17% EG-DMSO. Among vitrification groups, there was no significant difference in the number of total cells. However, vitrified blastocysts had a lower (P < 0.05) total cell number (range: 116.6 � 6.7–124.8 � 6.6) than fresh blastocysts (195.5 � 11.4). In conclusion, under our experimental conditions, the concentration of EG-DMSO can be decreased until 16% in the vitrification medium with no reduction of the in vitro developmental ability of the blastocysts. In addition, a 40% EG-based medium can be used for vitrification with results similar to those achieved using a medium containing 16% EG-DMSO.

Factors affecting the success rate of porcine embryo vitrification by the Open Pulled Straw method

The objectives of this study were: (1) to evaluate the influence of porcine embryo developmental stage on in vitro embryo development after vitrification, (2) to study the efficiency of the one-step dilution procedure, compared with conventional warming, for vitrified embryos at different stages of development, and (3) to determine the influence of the embryo donor on the in vitro survival of vitrified embryos at morulae and blastocyst stages. Two to four cell embryos, morulae and blastocysts were collected by laparotomy from weaned crossbred sows (n=55). Vitrification and conventional warming were performed using the OPS procedure with Superfine Open Pulled Straws (SOPS). For one-step dilution, embryos were placed in 800 microl TCM199-HEPES containing 20% of new born calf serum and 0.13 M sucrose for 5 min. To evaluate development, two to four cell embryos, morulae and blastocysts were cultured in vitro for 120, 48 and 24h, respectively. Some fresh embryos from each developmental stage were not vitrified and cultured as controls. Embryos were morphologically evaluated for their developmental capacity during the in vitro culture by stereomicroscopy. The total cell number of embryos was assessed by Hoechst-33342 staining and fluorescence microscope observation. There was a significant effect of the stage of development on the in vitro survival, perihatching rate and the number of cells of embryos after vitrification and warming (Experiment 1; p<0.001). The survival and perihatching rates of two to four cell embryos were lower than those obtained for morulae and blastocysts (p<0.001). No differences (p>0.05) in survival rates were found between vitrified and fresh blastocysts. The warming procedure did not affect the development and total cell number of vitrified two to four cell embryos, morulae or blastocysts (Experiment 2). However, donor had a significant effect (p<0.001) on the in vitro development and the number of cells of morulae and blastocysts after vitrification and warming (Experiment 3). In conclusion, the embryo developmental stage and the embryo donor were important factors that affected the development of porcine embryos after OPS-vitrification and warming. OPS-vitrification and the one-step dilution are efficient procedures to be used with intact porcine morulae and blastocysts.

Vitrification of in vitro cultured porcine two-to-four cell embryos

The objective of this experiment was to evaluate the effect of a 5-day period of in vitro culture of two-to-four cell porcine embryos up to the blastocyst stage on their ability to survive vitrification and warming. In order to increase the cooling rate, superfine open pulled straws and Vit-Master((R)) technology were used for vitrification. Two-to-four cell embryos were collected from weaned sows (n=11) on day 2 (D0=onset of estrus). Some embryos (N=63) were vitrified within 3h after collection, warmed and cultured for 120h (Group V2). Additionally, 81 two-to-four cell embryos were cultured for 96h in order to obtain blastocysts; these were then vitrified, warmed and cultured for 24h (Group VB; N=65). The remaining two-to-four cell embryos were used as controls and thus not vitrified (control embryos; N=70) but were cultured in vitro for 120h. The V2, VB and control embryos were evaluated for their developmental progression and morphology during culture. All embryos (V2, VB and controls) were fixed on the same day of development in order to assess the total number of blastomeres. The survival and blastocyst formation rates obtained from V2 embryos were very poor (9.6+/-0.7% and 3.2+/-0.5%, respectively). The survival and hatching rates of VB embryos (75.0+/-0.69% and 33.6+/-0.13%) were lower (p<0.001) than those obtained with control embryos (89.1+/-0.8% and 47.5+/-0.12%). Hatched VB embryos had a lower (p<0.01) total cell number than hatched control embryos (70.3+/-4.5 versus 90.6+/-3.2, respectively). There was no difference between expanded VB and control blastocysts. In conclusion, blastocysts derived from in vitro culture of two-to-four cell pig embryos could be successfully vitrified using SOPS straws and Vit-Master.

Brief coincubation of gametes in porcine in vitro fertilization: Role of sperm:oocyte ratio and post-coincubation medium

In this study, a short coincubation time of 10 min was used to determine the effect of different sperm:oocyte ratios during in vitro fertilization (IVF), and different periods of post-coincubation in a medium that is not appropriate for IVF, on fertilization parameters. In the first experiment, a total of 1624 in vitro matured oocytes, from 4 replicates, were inseminated with frozen-thawed spermatozoa at different sperm:oocyte ratios (2000, 1500, 1000 and 500 sperm:oocyte) and coincubated for 10 min or 6 h. The oocytes from 10 min of coincubation were washed in IVF medium to remove spermatozoa not bound to the zona pellucida and transferred to another droplet of the same medium (containing no spermatozoa) for 6h. The oocytes from the other group remained with the spermatozoa for 6h. Oocytes from both groups were then cultured in embryo culture medium (IVC) for 12h to assess fertilization parameters. In the second experiment, 1872 in vitro matured oocytes, in 3 replicates were inseminated with frozen-thawed spermatozoa using the same sperm:oocyte ratios as in the first experiment. The oocytes were coincubated for 10 min and transferred directly to IVC medium for 18 h (group A), to IVF medium (containing no sperm) only for 2h and then to IVC medium for 16 h (group B), or to IVF medium (containing no sperm) for 6h and then to IVC medium for 12 h (group C or control). There was an effect of sperm:oocyte ratio on all fertilization parameters in experiment 1. The efficiency of IVF (number of monospermic oocytes/total number inseminated) was higher (P<0.05) for oocytes coincubated with spermatozoa for 10 min and inseminated with 1500 and 1000 sperm:oocyte (35.8+/-3 and 37.6+/-2.7%, respectively) and for those coincubated for 6h with 500 spermatozoa per oocyte (37.2+/-3.1%). In experiment 2, the penetration and efficiency rates obtained in group A were poor (between 3 and 15%) irrespective of the sperm:oocyte ratio. However, in group B the fertilization parameters were similar to the controls and were also affected by the sperm:oocyte ratio. These results demonstrate that coincubation time may be reduced to 10 min to increase the efficiency of fertilization depending on the sperm:oocyte ratio, and that the spermatozoa bound to the zona pellucida require a maximum of 2h in an appropriate medium to penetrate the oocytes.

Adjustments in IVF system for individual boars: value of additives and time of sperm-oocyte co-incubation

In vitro fertilization (IVF) in pigs is still considered sub-optimal, due to the variable occurrence of polyspermy, variability mainly related to sperm differences. The present study was conducted in an attempt to increase the efficiency of the in vitro production of porcine embryos by optimizing the in vitro fertilization (IVF) protocol for individual males, with regard to the composition of the fertilization medium (experiments 1 and 2) and the length of gamete co-incubation time (experiment 3). A total of 5,943 COC's were in vitro matured (IVM) and inseminated with frozen-thawed spermatozoa from 2 boars (A and B). Experiment 1 determined the effect of additives caffeine (2mM), hyaluronic acid (HA; [0.5mg/mL]) and adenosine (10 microM), alone or in combination, to the IVF-medium during sperm-oocyte co-incubation. Experiment 2 tested the addition of various HA (0, 0.5, 1.0 and 1.5mg/ml) and adenosine (0, 10, 20 and 40 microM) concentrations in the fertilization medium; while experiment 3 investigated the effect of two periods of sperm-oocyte co-incubation (10 min or 6h). In the case of 10 min sperm-oocyte co-incubation, oocytes with attaching spermatozoa were further cultured in IVF-medium containing no spermatozoa until the 6h of insemination was completed. Presumptive zygotes were cultured in embryo culture medium for 12-15 h to assess fertilization parameters. In experiment 1, only caffeine significantly influenced the outcome of fertilization, albeit being a clearly boar-dependent effect. In experiment 2, similar boar differences were seen for HA supplementation while presence of exogenous adenosine did not influence fertilization parameters in either boar. The results of experiment 3 demonstrated that a short co-incubation time significantly (P<0.001) increased penetration rate and mean number of spermatozoa per oocyte (74.9+/-3.9% versus 62.7+/-3.9% and 1.5+/-3.2 versus 1.3+/-3.5 for 10 min or 6h, respectively), but reduced mono-spermy (P<0.001, 57.9+/-2.5% versus 70.0+/-2.8%) when boar A was used. However, such effects were not seen with boar B, in which sperm-oocyte co-incubation time did not affect the efficiency of fertilization. In view of the present results, a preliminary screening for each individual male is required to select optimal conditions for IVF.

275 PENTOXIFYLLINE ADDED TO FREEZING EXTENDER HAS A DELETERIOUS EFFECT ON POST-THAW BOAR SPERM QUALITY AND IN VITRO FERTILIZATION RATE

Pentoxifylline, a methylxanthine derivative, is considered to be a hyperactivation and acrosome reaction-improving agent. The purpose of this study was to test how the addition of pentoxifylline to freezing extender influences post-thaw sperm motility and membrane integrity. The ability of thawed spermatozoa to fertilize in vitro-matured oocytes was also assessed. Pooled ejaculate sperm-rich fractions collected from three fertile boars were frozen in 0.5-mL straws after being diluted in lactose/egg yolk/glycerol/Orvus-ES-Paste extender (0 pentoxifylline = control) or the same extender supplemented with 2, 4, 8, 16, and 32 mM pentoxifylline. To evaluate post-thaw sperm survival, the percentage of total motile spermatozoa and rapid progressive spermatozoa (CASA system) and plasma membrane and acrosome integrity (flow cytometry) were assessed. Data from six replicates were analyzed in a split plot design using a PROMIXED model. The addition of 4, 8, 16, and 32 mM pentoxifylline to freezing extender significantly decreased progressive and total motility (P < 0.001) compared with control (4.5/26.6%, 4.5/24.5%, 2.8/20.5%, 0.6/11.4%, and 13.2/49.7% for the 4, 8, 16, and 32 mM pentoxifylline groups and the control group, respectively). The same was observed for sperm viability; the percentage of viable spermatozoa with intact acrosomes was significantly lower (P < 0.001) in pentoxifylline-treated groups compared with the control group, chiefly in the 16 mm, and 32 mM pentoxifylline groups (54, 11.6, and 6.2% for control, 16 and 32 mM, respectively). To evaluate in vitro fertilization parameters, cumulus-oocyte complexes were matured in BSA-free NCSU23 medium with 10% porcine follicular fluid, 0.1% cysteine, 10 ng EGF, 10 IU/mL eCG, and 10 IU/mL hCG, in a incubator at 39�C and 5% CO2. After 40-44 h of maturation, oocytes (n = 1067, in three replicates) were denuded of cumulus cells, washed, transferred to droplets (30 oocytes in 50 �L) of TBM medium supplemented with 2 mM caffeine and 0.2% BSA, and inseminated (2000 thawed sperm/oocyte). After a co-incubation period of 6 h, oocytes were washed and transferred to droplets (500 �L) of NCSU23 with 0.4% BSA for another 10-14 h, then fixed and stained for 72 h, and examined under a phase-contrast microscope. Data were analyzed as split plot design using a PROMIXED model. The addition of pentoxifylline to the freezing extender reduced significantly (P < 0.001) the penetration rate (51.4, 17.5, 15.8, 17.8, 9.5, and 4.8% for the 0, 2, 4, 8, 16, and 32 mM pentoxifylline groups, respectively) and the efficiency (monospermic oocytes/total inseminated oocytes) of fertilization (34.8, 14.6, 14.7, 15.5, 7.9, and 4.8% for the 0, 2, 4, 8, 16, and 32 mM pentoxifylline groups, respectively) as compared with the control group (the first value in each of these two cases). It is therefore concluded that pentoxifylline added to the freezing extender has a deleterious effect on post-thaw boar sperm quality and on their ability to fertilize the oocytes in vitro. This work was supported by CICYT (AGL05-0471).

352 IMPROVING THE EFFICIENCY OF LAPAROSCOPIC INTRAOVIDUCTAL INSEMINATION WITH SEX-SORTED BOAR SPERMATOZOA

The insemination of a low number of sex-sorted spermatozoa is a critical issue that must be solved in order to enable the commercial application of this technology in pigs. A new procedure for laparoscopic intraoviductal insemination in sows has recently been reported (Vazquez et al. 2005 Reprod. Dom. Animals 40, 375 abst.). To improve the efficiency of this technique, this experiment was designed to determine the influence of insemination time, relative to the time of ovulation, on the number and quality of zygotes recovered after laparoscopic insemination of sows with sex-sorted spermatozoa. Spermatozoa were stained with Hoechst 33342 and sexed using the EPICS Altra flow sorter (Coulter Corporation, Miami, FL, USA) modified to operate at 42 psi for spermatozoa. Sorted spermatozoa were collected in tubes containing 1.5 mL of TEST-yolk (2%)-seminal plasma (10%). Post-weaning crossbred sows (n = 212; parity 2-4) were hormonally treated with eCG (Folligon; Intervet, Boxmeer, The Netherlands) and hCG (Veterin Corion, Divasa, Spain) and their ovaries were examined using transrectal ultrasonography at intervals of 4 h from 30 h after hCG injection to the laparoscopic insemination. Sows were allotted into three groups according to their ovarian status at insemination: preovulatory (P; n = 131), ovulating (O; n = 43), and ovulated (CL; n = 38) follicles. Follicle status was reconfirmed at insemination by direct observation using the laparoscope. Sows were inseminated in both oviducts with 0.3 million sex-sorted spermatozoa in 0.1 mL of extender. Eighteen hours later, putative zygotes were collected by washing the oviducts after laparotomy, fixed, stained with lacmoid, and examined by phase-contrast microscopy. Penetration rates were evaluated as numbers of monospermic and polyspermic oocytes per oocytes collected. Monospermic rates were evaluated as numbers of monospermic oocytes per oocytes penetrated. Data were analyzed by ANOVA. The number of putative zygotes collected were 2825, 957, and 736 for P, O, and CL groups, respectively. Penetration rates were not different (P > 0.05) among groups (90.4%, 94.5%, and 93.7% for P, O, and CL, respectively). However, the monospermic rate was significantly higher (P < 0.05) in the P group (97.4%) when compared to the O or CL groups (66.7% and 5.1% for O and CL, respectively). Moreover, percentages of sows with six or more zygotes, potentially able to carry the pregnancy to term, were 90.8% and 46.5% for P and O groups, respectively (P < 0.05). No sow of the CL group presented six or more zygotes. In conclusion, laparoscopic insemination should be performed only in sows with preovulatory follicles when sex sorted spermatozoa are inseminated using this technology. This work was supported by CDTI and Fundacion Seneca.

88 IS STEREOMICROSCOPY AN EFFICIENT METHOD FOR EVALUATING THE VITRIFIED PORCINE EMBRYO QUALITY?

The development of the open pulled straw vitrification has provided excellent results of in vitro porcine embryo development. Embryo quality evaluation after vitrification has been traditionally focused on morphological assessment performed by stereomicroscopy. The objective of this experiment was to evaluate the efficiency of the stereomicroscopic evaluation of vitrified-warmed (V) porcine blastocysts. Unhatched blastocysts were obtained after slaughter from Large-White gilts (n = 9). Blastocysts (n = 75) were vitrified and warmed using the protocol described by Cuello et al. (2004 Theriogenology 61, 353-361). After warming, vitrified blastocysts were cultured for 24 h. Then blastocysts were morphologically assessed for their progression and morphology by stereomicroscopy. Blastocysts that reformed their blastocoelic cavities showing an excellent appearance were considered viable. Some of the viable blastocysts kept their zonae pellucidae (V viable expanded blastocysts) and others hatched during the in vitro culture (V viable hatched blastocysts). The remaining blastocysts were classified as degenerated embryos. A group of fresh blastocysts was not vitrified and cultured in vitro for 24 h (control group). All of the control blastocysts were considered viable by stereomicroscopy. Some fresh, V viable expanded, V viable hatched, and V degenerated blastocysts (n = 13, n = 19, n = 9, and n = 9, respectively) were processed for ultrastructural study by light and transmission electron microscopy or stained with Hoechst-33342 and TUNEL for cell death evaluation (n = 16, n = 21, n = 11, and n = 6, respectively). All V hatched blastocysts showed ultrastructure similar to that of control hatched blastocysts. However, 26.3% of the V viable expanded blastocysts revealed important ultrastructural alterations in comparison with control expanded blastocysts. These observations suggest that stereomicroscopic evaluation was not efficient enough for V expanded blastocysts. As expected, degenerated blastocysts showed ultrastructural disintegration and disorganization. Hatched V blastocysts did not differ (P < 0.05) from control hatched blastocysts with regard to the total cell number and ratio of death cells (173 � 4.8 vs. 202.1 � 10.9 and 2.8 � 0.5% vs. 1.9 � 0.3%, respectively). However, V expanded blastocysts a had higher (P < 0.01) cell death level (4.3 � 3.4%) than that observed in the control expanded blastocysts (1.1 � 0.3%). Degenerated embryos showed the lowest (P < 0.01) total cell number (45.7 � 4.0). The 66.7% of the degenerated blastocysts exhibited wide TUNEL-labeled areas, and the remaining 33.3% showed TUNEL label over 19.4 � 6.3% of the cells. In conclusion, the hatching rate assessed by stereomicroscopy is a more efficient parameter than assessing the in vitro viability (ratio of blastocysts that reformed their blastocoelic cavities after warming) for estimating the quality of V blastocysts. This work was supported by CICYT (AGL2004-07546) and S�neca (01287/PD/04).

Influence of storage time on functional capacity of flow cytometrically sex-sorted boar spermatozoa

Sex-sorting of boar spermatozoa is an emerging biotechnology, still considered suboptimal owing to the slowness of the process, which requires long sorting periods to obtain an adequate number of spermatozoa to perform a non-surgical insemination. This period involves storage of sorted cells that could impair their functional capacity. Here, we have studied how the storage of sex-sorted boar spermatozoa affects their functional capacity. Sorted spermatozoa were assessed at various times (0, 2, 5h or 10h) during storage after sorting and compared with diluted and unsorted spermatozoa for sperm motility patterns, plasma membrane and acrosomal integrity and their ability to penetrate homologous IVM oocytes. Sex-sorted sperm motility and membrane integrity only decreased significantly (p<0.05) by the end of the storage period (10h) compared to unsorted spermatozoa. Sperm velocity, ALH and Dance increased significantly (p<0.05), immediately post-sorting, returning to unsorted sperm values during storage. Acrosome integrity was not seriously affected by the sorting process, but decreased (p<0.05) during storage after sorting. Sorted spermatozoa stored 2h after sorting did not differ from unsorted in penetration rates and numbers of spermatozoa per oocyte, reaching the highest (p<0.05) penetration rates and sperm numbers per oocyte, when co-cultured for 6 or more hours. Non-storage or storage for 5h or 10h negatively (p<0.05) affected sperm penetration ability. In conclusion, although flow cytometrically sex-sorted spermatozoa are able to maintain motility, viability and acrosomal integrity at optimal levels until 10h of storage after sorting, fertilizing ability is maintained only over shorter storage times (<5h).

309 SEX SORTED BOAR SPERMATOZOA: TIME COURSE AND PROFILE OF THEIR IN VITRO PENETRATION ABILITY AFTER STORAGE IN THE PRESENCE OF HOMOLOGOUS SEMINAL PLASMA

Addition of seminal plasma (SP) to the collection medium has been shown to be beneficial for motility and viability of sex-sorted and stored spermatozoa. However, SP could not only delay but also decrease the in vitro fertilization rates of IVM pig oocytes. In the present study, the time-course of IVM pig oocyte penetration of sex sorted boar spermatozoa stored in the presence or absence of SP was evaluated. Spermatozoa were sex-sorted following the Beltsville sperm sexing technology (Johnson and Welch 1999 Theriogenology 52, 1323–1342) and collected in TEST-egg yolk buffer (2%) with (10%) or without (control) SP. Sex-sorted spermatozoa were stored at 20°C during 0, 2, 5, and 10 h after sorting. Oocytes were matured in vitro in NCSU23 (Peters and Wells 1663 J. Reprod. Fertil. 48, 61–73) for 44 h in 5% CO2 in air at 39°C. The in vitro penetration time-course was determined by co-incubating the sex-sorted and stored spermatozoa with IVM oocytes during 3, 6, and 18 h in modified TRIS-buffered medium (mTBM) (Abeydeera and Day 1997 Theriogenology 48, 537–544) at 39°C in an atmosphere of 5% CO2 in air. Penetration rates and number of spermatozoa per oocyte were assessed after fixation and staining of the oocytes. Statistical analyses were conducted by ANOVA. Presence of SP did not delay the onset of the oocyte penetration. Moreover, at 3 h of co-incubation, SP increased (P < 0.05) both penetration rates and mean number of spermatozoa per oocyte in sorted and stored boar spermatozoa when compared with control (45 vs. 20, 50 vs. 32, 38 vs. 23, 15 vs. 8, at 0, 2, 5, and 10 h of storage with SP and control, respectively). High penetration rates were reached after 6 h of co-incubation (82 vs. 51, 96 vs. 76, 83 vs. 48, 31 vs. 24, at 0, 2, 5, and 10 h of storage with SP and control, respectively) in sorted and stored samples, with no further increase at 18 h (70 vs. 63, 92 vs. 79, 87 vs. 53, 55 vs. 40, at 0, 2, 5, and 10 h of storage with SP and control, respectively). Spermatozoa stored 2 h in the presence of SP showed the best penetration rate and highest mean number of spermatozoa per oocyte. The mean number of spermatozoa per oocyte increased as the co-incubation time increased (ranging from 2.1 to 5.8 for sorted spermatozoa stored 2 h in the presence of SP at 3 h and 18 h of co-incubation, respectively). In conclusion, the presence of SP during the storage of sex-sorted spermatozoa improves their in vitro fertilizing ability without affecting the onset of the oocyte penetration time. This work was supported by DGICYT (AGL 2001-0471), Fundación Seneca (PB174/FS/02) and CTIC (2103SIU0040).