Quantifying maternal investment in mammals using allometry

Maternal investment influences the survival and reproduction of both mothers and their progeny and plays a crucial role in understanding individuals' life-history and population ecology. To reveal the complex mechanisms associated with reproduction and investment, it is necessary to examine variations in maternal investment across species. Comparisons across species call for a standardised method to quantify maternal investment, which remained to be developed. This paper addresses this limitation by introducing the maternal investment metric - MI - for mammalian species, established through the allometric scaling of the litter mass at weaning age by the adult mass and investment duration (i.e. gestation + lactation duration) of a species. Using a database encompassing hundreds of mammalian species, we show that the metric is not highly sensitive to the regression method used to fit the allometric relationship or to the proxy used for adult body mass. The comparison of the maternal investment metric between mammalian subclasses and orders reveals strong differences across taxa. For example, our metric confirms that Eutheria have a higher maternal investment than Metatheria. We discuss how further research could use the maternal investment metric as a valuable tool to understand variation in reproductive strategies.

Twin management in the mare: A review

Twin gestation in the mare is undesirable and can have disastrous consequences. As in many cases, the key to success in twin management lies in a thorough follow-up and accurate recording of clinical findings in the pre-breeding examination. A pregnancy diagnosis in the mobility phase is imperative for a good outcome in the event of twin reduction. If a twin gestation is not diagnosed during this early pregnancy stage, several other procedures exist for managing post-fixation twins (>16 days) with varying degrees of success. Most twin pregnancies are the result of multiple ovulations (dizygotic twins). However, monozygotic twins are also sporadically diagnosed, due to the increasing number of transferred in vitro produced equine embryos. In these cases, the most optimal treatment strategy still needs to be determined. This review provides an overview of the various twin reduction techniques described with the expected prognosis as well as of some less reported techniques with their results. In addition, physiological events and the reduction techniques are demonstrated to the user in virtual 3-dimensional illustrations.

tRNAGlu-derived fragments from embryonic extracellular vesicles modulate bovine embryo hatching

Transfer RNA-derived small RNAs (tsRNAs) have been shown to be involved in early embryo development and repression of endogenous retroelements in embryos and stem cells. However, it is unknown whether tsRNAs also regulate embryo hatching. In this study, we mined the sequencing data of a previous experiment in which we demonstrated that the microRNA (miRNA) cargo of preimplantation embryonic extracellular vesicles (EVs) influences embryo development. We thus profiled the tsRNA cargo of EVs secreted by blastocysts and non-blastocysts. The majority of tsRNAs was identified as tRNA halves originating from the 5´ ends of tRNAs. Among the 148 differentially expressed tsRNAs, the 19 nt tRNA fragment (tRF) tDR-14:32-Glu-CTC-1 was found to be significantly up-regulated in EVs derived from non-blastocysts. RT-qPCR assays confirmed its significant up-regulation in non-blastocyst embryos and their conditioned medium compared to the blastocyst group (P < 0.05). Inhibition of tDR-14:32-Glu-CTC-1 by supplementing antagomirs to the conditioned medium improved embryo hatching (P < 0.05). Transcriptomic analysis of embryos treated with tDR-14:32-Glu-CTC-1 antagomirs further showed differential expression of genes that are associated with embryo hatching and implantation. In summary, tDR-14:32-Glu-CTC-1 is up-regulated in non-blastocyst embryos and their secretions, and inhibition of tDR-14:32-Glu-CTC-1 promotes embryo hatching, while influencing embryo implantation-related genes and pathways. These results indicate that embryonic EVs containing specific tRFs may regulate preimplantation embryo development.

Genome-wide equine preimplantation genetic testing enabled by simultaneous haplotyping and copy number detection

In different species, embryonic aneuploidies and genome-wide errors are a major cause of developmental failure. The increasing number of equine embryos being produced worldwide provides the opportunity to characterize and rank or select embryos based on their genetic profile prior to transfer. Here, we explored the possibility of generic, genome-wide preimplantation genetic testing concurrently for aneuploidies (PGT-A) and monogenic (PGT-M) traits and diseases in the horse, meanwhile assessing the incidence and spectrum of chromosomal and genome-wide errors in in vitro-produced equine embryos. To this end, over 70,000 single nucleotide polymorphism (SNP) positions were genotyped in 14 trophectoderm biopsies and corresponding biopsied blastocysts, and in 26 individual blastomeres from six arrested cleavage-stage embryos. Subsequently, concurrent genome-wide copy number detection and haplotyping by haplarithmisis was performed and the presence of aneuploidies and genome-wide errors and the inherited parental haplotypes for four common disease-associated genes with high carrier frequency in different horse breeds (GBE1, PLOD1, B3GALNT2, MUTYH), and for one color coat-associated gene (STX17) were compared in biopsy-blastocyst combinations. The euploid (n = 12) or fully aneuploid (n = 2) state and the inherited parental haplotypes for 42/45 loci of interest of the biopsied blastocysts were predicted by the biopsy samples in all successfully analyzed biopsy-blastocyst combinations (n = 9). Two biopsies showed a loss of maternal chromosome 28 and 31, respectively, which were confirmed in the corresponding blastocysts. In one of those biopsies, additional complex aneuploidies not present in the blastocyst were found. Five out of six arrested embryos contained chromosomal and/or genome-wide errors in most of their blastomeres, demonstrating their contribution to equine embryonic arrest in vitro. The application of the described PGT strategy would allow to select equine embryos devoid of genetic errors and pathogenetic variants, and with the variants of interest, which will improve foaling rate and horse quality. We believe this approach will be a gamechanger in horse breeding.

Oxidative stress in donor mares for ovum pick-up delays embryonic development

The in vitro production of equine embryos via ovum pick-up (OPU) and intracytoplasmic sperm injection (ICSI) has increased rapidly. There is a marked effect of the individual mare on the outcome of OPU-ICSI, but little is known about the influence of the mare's health condition. This study aimed to investigate the potential associations between the concentrations of interleukin-6 (IL-6), reactive oxygen metabolites (d-ROMs), and biological antioxidant potential (BAP) in serum of oocytes' donor mares and the subsequent embryonic development. Just before OPU, a blood sample was collected from 28 Warmblood donor mares, that were subjected to a routine OPU-ICSI program. The serum concentrations of IL-6, d-ROMs, and BAP were assayed photometrically. The maturation, cleavage and blastocyst rate as well as the kinetics of blastocyst development were recorded. The average blastocyst rate was 24.68 ± 5.16% and the average concentrations of IL-6, d-ROMs, and BAP were 519.59 ± 157.08 pg/mL, 171.30 ± 4.55 carratelli units (UCARR), and 2711.30 ± 4.55 μmol/L, respectively. Serum concentrations of IL-6, d-ROMs, and BAP were not significantly different between mares yielding at least one blastocyst (552.68 ± 235.18 pg/mL, 168.36 ± 5.56 UCARR, and 2524.80 ± 159.55 μmol/L) and mares yielding no blastocysts (468.47 ± 179.99 pg/mL, 175.85 ± 7.89 UCARR, and 2999.50 ± 300.13 μmol/L, respectively). Serum concentrations of d-ROMs were significantly lower in mares with fast growing (at day 7-8 post ICSI; 148.10 ± 8.13 UCARR) compared to those with slow growing blastocysts (≥ day 9 post ICSI; 179.41 ± 4.89 UCARR; P = 0.003). Taken together, the serum concentration of IL-6, d-ROMs, and BAP do not determine the mare's ability to produce blastocysts in vitro. Although it may be questioned whether a single sample is representative of the mare's health status, changes in serum metabolites related to oxidative stress at the time of oocyte retrieval were linked to a delayed blastocyst development in a clinical OPU-ICSI outcome.

Manual versus deep learning measurements to evaluate cumulus expansion of bovine oocytes and its relationship with embryo development in vitro

Cumulus expansion is an important indicator of oocyte maturation and has been suggested to be indicative of greater oocyte developmental capacity. Although multiple methods have been described to assess cumulus expansion, none of them is considered a gold standard. Additionally, these methods are subjective and time-consuming. In this manuscript, the reliability of three cumulus expansion measurement methods was assessed, and a deep learning model was created to automatically perform the measurement. Cumulus expansion of 232 cumulus-oocyte complexes was evaluated by three independent observers using three methods: (1) measurement of the cumulus area, (2) measurement of three distances between the zona pellucida and outer cumulus, and (3) scoring cumulus expansion on a 5-point Likert scale. The reliability of the methods was calculated in terms of intraclass-correlation coefficients (ICC) for both inter- and intra-observer agreements. The area method resulted in the best overall inter-observer agreement with an ICC of 0.89 versus 0.54 and 0.30 for the 3-distance and scoring methods, respectively. Therefore, the area method served as the base to create a deep learning model, AI-xpansion, which reaches a human-level performance in terms of average rank, bias and variance. To evaluate the accuracy of the methods, the results of cumulus expansion calculations were linked to embryonic development. Cumulus expansion had increased significantly in oocytes that achieved successful embryo development when measured by AI-xpansion, the area- or 3-distance method, while this was not the case for the scoring method. Measuring the area is the most reliable method to manually evaluate cumulus expansion, whilst deep learning automatically performs the calculation with human-level precision and high accuracy and could therefore be a valuable prospective tool for embryologists.

Lipid metabolites, interleukin-6 and oxidative stress markers in follicular fluid and their association with serum concentrations in mares

The application of trans-vaginal ovum pick up (OPU) and intracytoplasmic sperm injection (ICSI) is well established for commercial in vitro embryo production in horses. These assisted reproductive techniques are especially applied during the non-breeding season of the mare. However, little is known about how the health of the oocyte donor may affect the biochemical composition of the follicular fluid (FF) in small and medium-sized follicles routinely aspirated during OPU. This study aimed to investigate associations between systemic and FF concentrations of interleukin-6 (IL-6), total cholesterol, triglycerides, non-esterified fatty acids (NEFA), reactive oxygen metabolites (d-ROMs), biological antioxidant potential (BAP), and oxidative stress index (OSI) during the non-breeding season in mares. At the slaughterhouse, serum and FF of small (5-10 mm in diameter), medium (> 10-20 mm in diameter), and large (> 20-30 mm in diameter) follicles were sampled from 12 healthy mares. There was a strong positive association (P < 0.01) between the concentration of IL-6 in serum and those measured in small (r = 0.846), medium (r = 0.999), and large (r = 0.996) follicles. Serum concentrations of NEFA were positively correlated (P < 0.05) with those measured in small (r = 0.726), medium (r = 0.720), and large (r = 0.974) follicles. Values of total cholesterol and OSI in serum and medium follicles were significantly associated (r = 0.736 and r = 0.696, respectively). The serum concentrations of all lipid metabolites were markedly higher than those measured in FF of small- and medium-sized follicles. Values of IL-6 and OSI did not change significantly between serum and all follicle classes (P ≥ 0.05). To conclude, changes in the blood composition associated with inflammation, oxidative stress, and disturbed lipid metabolism of mares may lead to an inadequate oocyte microenvironment, which could affect oocyte quality and the success rate of OPU/ICSI programs. Further research should indicate whether these changes may ultimately affect in vitro oocyte developmental capacity and subsequent embryo quality.

Single closed-tube quantitative real-time PCR assay with dual-labelled probes for improved sex determination of equine embryos

In addition to fulfilling many breeders' curiosity, equine embryonic sex determination can have a profound commercial impact. However, the application of currently described assays for equine embryonic sexing has rendered variable diagnosis and validation rates, with sensitivity being the main problem. In addition, while pregnancy results of in vivo-flushed equine embryos following a needle aspiration biopsy equal those of non-biopsied embryos, the effect on in vitro-produced embryos is unknown. Here, we aimed to develop a highly sensitive and specific assay for equine sex determination that can be directly performed on few embryonic cells, and to test the effect of a needle aspiration biopsy on the viability of the in vitro-produced embryo. To this end, a multiplex quantitative real-time PCR (qPCR) assay with dual-labelled probes was designed to allow the simultaneous generation of both male-specific and control fragments in a single closed-tube reaction, avoiding potential sample loss or contamination. To improve sensitivity, multicopy and polymeric genes were chosen to be specifically amplified, i.e., eight copies of Y-chromosomal ETSTY5 as male-specific and four autosomal UBC monomers as control fragment. Specificity was enhanced by the equine-specific character of ETSTY5 and by using dual-labelled probes. The assay was optimised with equine male and female genomic DNA and demonstrated a 100% accuracy and a >95% qPCR efficiency down to 10 pg of DNA. The assay was subsequently applied to determine the sex of 44 in vitro-produced embryos, collecting trophectoderm biopsies by means of a needle aspiration biopsy and herniating cells. Of all trophectoderm biopsies and herniating cell samples (n = 54), 87% could be diagnosed. Assay results were validated on a second sample obtained from the biopsied embryo (n = 18) or, by ultrasound-based sex determination of the foetus (n = 7) following the transfer of the biopsied embryo to a recipient mare, with about half of the embryos being fillies and colts. The needle aspiration biopsy procedure did not impair initial pregnancy rate or early pregnancy losses as compared to non-biopsied embryos. In conclusion, we report a safe, reliable, fast, and cost-effective assay for equine sex determination which was validated for the sex determination of in vitro-produced embryos based on few embryonic cells, and needle aspiration biopsy did not impair the embryo's viability. The assay and safe biopsy strategy hold potential for other applications.

A comparative study of canine epididymal sperm collection techniques and cryopreservation

Introduction

An optimized collection method and freezing protocol for preservation of epididymal spermatozoa remains a topic of interest to many scientists. The current study focused on the collection and preservation of canine epididymal spermatozoa. During the process of collection of canine epididymal spermatozoa, blood content can occur, which may affect sperm cryopreservation in a negative way. Here, we compared first two epididymal sperm collection techniques [epididymal mincing (EM) and single incision epididymal sperm aspiration (SESA)]; and next we tried to solve the issue of blood content using an erythrocyte lysis buffer (ELB).

Methods

Hence spermatozoa were collected after weighing the epididymides, either by EM or SESA, and sperm quality assessed prior to and post freezing (concentration, total sperm output (TSO), motility, viability and morphology). Next, new sperm samples were collected from eight epididymides by EM and subjected either to a standard freezing protocol or to an ELB treatment freezing protocol. Post-thaw sperm parameters (concentration, TSO, motility, viability and morphology), including intracellular reactive oxygen species (ROS) and lipid peroxidation were assessed. The correlation between the weight of the epididymis and the TSO was evaluated based on the collection technique, and differences in sperm parameters were detected both within different collection techniques and between different pre-freezing treatment protocols.

Results

There was a very strong correlation between the weight of the epididymis and the TSO for the EM technique (p  =  0.002, R2 =  0.6), along with an increased sperm motility with EM compared to SESA (median 80%, inter-quartile range (IQR) 88-65 and median 67.5%, IQR 72.5-52.5, respectively; (p  =  0.002). Post-thaw samples subjected to ELB treatment freezing protocol had lower motility and higher intracellular ROS compared to the standard freezing protocol (motility: median 56.25%, IQR 60-48.75 and median 70%, IQR 72.5-63, respectively; p   =  0.01; ROS: median 78.5%, IQR 81.25-75.5 and median 70%, IQR 70.5-68.75, respectively; (p  =  0.04).

Discussion

The results indicated that EM is a better technique to harvest epididymal spermatozoa despite the presence of some blood content. Furthermore, the ELB treatment should not be implemented to remove those red blood cells prior to cryopreservation of epididymal spermatozoa in dogs.

Postmortem Collection of Gametes for the Conservation of Endangered Mammals: A Review of the Current State-of-the-Art

The collection of gametes from recently deceased domestic and wildlife mammals has been well documented in the literature. Through the utilization of gametes recovered postmortem, scientists have successfully produced embryos in 10 different wildlife species, while in 2 of those, offspring have also been born. Thus, the collection of gametes from recently deceased animals represents a valuable opportunity to increase genetic resource banks, obviating the requirement for invasive procedures. Despite the development of several protocols for gamete collection, the refinement of these techniques and the establishment of species-specific protocols are still required, taking into account both the limitations and the opportunities. In the case of wildlife, the optimization of such protocols is impeded by the scarcity of available animals, many of which have a high genetic value that must be protected rather than utilized for research purposes. Therefore, optimizing protocols for wildlife species by using domestic species as a model is crucial. In this review, we focused on the current advancements in the collection, preservation, and utilization of gametes, postmortem, in selected species belonging to Equidae, Bovidae, and Felidae, both domestic and wildlife.

Transcriptomics Reveal Molecular Differences in Equine Oocytes Vitrified before and after In Vitro Maturation

In the last decade, in vitro embryo production in horses has become an established clinical practice, but blastocyst rates from vitrified equine oocytes remain low. Cryopreservation impairs the oocyte developmental potential, which may be reflected in the messenger RNA (mRNA) profile. Therefore, this study aimed to compare the transcriptome profiles of metaphase II equine oocytes vitrified before and after in vitro maturation. To do so, three groups were analyzed with RNA sequencing: (1) fresh in vitro matured oocytes as a control (FR), (2) oocytes vitrified after in vitro maturation (VMAT), and (3) oocytes vitrified immature, warmed, and in vitro matured (VIM). In comparison with fresh oocytes, VIM resulted in 46 differentially expressed (DE) genes (14 upregulated and 32 downregulated), while VMAT showed 36 DE genes (18 in each category). A comparison of VIM vs. VMAT resulted in 44 DE genes (20 upregulated and 24 downregulated). Pathway analyses highlighted cytoskeleton, spindle formation, and calcium and cation ion transport and homeostasis as the main affected pathways in vitrified oocytes. The vitrification of in vitro matured oocytes presented subtle advantages in terms of the mRNA profile over the vitrification of immature oocytes. Therefore, this study provides a new perspective for understanding the impact of vitrification on equine oocytes and can be the basis for further improvements in the efficiency of equine oocyte vitrification.

Cathepsin-L Secreted by High-Quality Bovine Embryos Exerts an Embryotrophic Effect In Vitro

While human in vitro embryo production is generally performed individually, animal models have shown that culturing embryos in groups improves blastocyst yield and quality. Paracrine embryotrophins could be responsible for this improved embryo development, but their identity remains largely unknown. We hypothesize that supplementation of embryotrophic proteins to a culture medium could be the key to improve individual embryo production. In this study, proteomics screening of culture media conditioned by bovine embryos revealed cathepsin-L as being secreted by both excellent- and good-quality embryos, while being absent in the medium conditioned by poor-quality embryos. The embryotrophic role of cathepsin-L was explored in vitro, whereby bovine zygotes were cultured individually for 8 days with or without cathepsin-L. Preliminary dose–response experiments pointed out 100 ng/mL as the optimal concentration of cathepsin-L in embryo culture medium. Supplementation of cathepsin-L to individual culture systems significantly improved blastocyst development and quality in terms of blastocoel formation at day 7, and the hatching ratio and apoptotic cell ratio at day 8, compared to the control. Taken together, cathepsin-L acts as an important embryotrophin by increasing embryo quality, and regulating blastulation and hatching in bovine in vitro embryo production.

Development of a Microfluidic Chip Powered by EWOD for In Vitro Manipulation of Bovine Embryos

Digital microfluidics (DMF) holds great potential for the alleviation of laboratory procedures in assisted reproductive technologies (ARTs). The electrowetting on dielectric (EWOD) technology provides dynamic culture conditions in vitro that may better mimic the natural embryo microenvironment. Thus far, EWOD microdevices have been proposed for in vitro gamete and embryo handling in mice and for analyzing the human embryo secretome. This article presents the development of the first microfluidic chip utilizing EWOD technology designed for the manipulation of bovine embryos in vitro. The prototype sustains the cell cycles of embryos manipulated individually on the chips during in vitro culture (IVC). Challenges related to the chip fabrication as well as to its application during bovine embryo IVC in accordance with the adapted on-chip protocol are thoroughly discussed, and future directions for DMF in ARTs are indicated.

Embryo morphokinetics derived from fresh and vitrified bovine oocytes predict blastocyst development and nuclear abnormalities

Embryo development is a dynamic process and critical stages may go unnoticed with the use of traditional morphologic assessments, especially the timing of embryonic divisions and aberrant zygotic cleavage patterns. Bovine embryo development is impaired after oocyte vitrification, but little is known about the underlying morphokinetic behavior. Here, bovine zygotes from fresh (n = 708) and vitrified oocytes (n = 182) were monitored by time-lapse imaging and the timing and nature of early blastomere divisions were modeled to find associations with blastocyst development at day 8. The predictive potential of morphokinetic parameters was analyzed by logistic regression and receiver operating characteristic curve analysis to determine optimal cut-off values. Lag-phase was highly correlated with embryo development. Remarkably, 100% of zygotes that reached the blastocyst stage showed a lag-phase. Fast first cleavage increased the chance of blastocyst development to 30% with a cut-off of 32 h and 22 min. Aberrant zygotic cleavage events, including multipolar division, unequal blastomere sizes, and membrane ruffling resulted in decreased blastocyst development. Multipolar division leads to uneven blastomeres, which was associated with anuclear and multinuclear blastomeres, indicating genome segregation errors. Moreover, we described for the first time morphokinetics of embryos derived from vitrified bovine oocytes. Vitrification severely affected blastocyst development, although lower cryoprotectant concentration in equilibration solutions seems to be less detrimental for embryo yield. Impaired development was linked to slow cleavages, lower lag-phase incidence, and increased early embryonic arrest. Typically, less than 15% of the embryos produced from vitrified oocytes reached more than eight cells. Interestingly, the rate of abnormal first cleavage events was not affected by oocyte vitrification. In conclusion, time to first cleavage, the presence of a lag-phase, and the absence of aberrant zygotic cleavage were the best predictors of bovine blastocyst development for both fresh and vitrified oocytes.

Feline ovarian tissue vitrification: The effect of fragment size and base medium on follicular viability and morphology

To achieve optimal vitrification, tissue structure and fragment size represent a challenge for obtaining sufficient cooling velocity. Theoretically, thin ovarian tissue fragments lead to higher surface contact, hence higher solute penetration. Another critical factor is the concentration of cryoprotectants (CPA): CPA toxicity may occur with high concentrations, and as such, this may induce local apoptosis. Therefore two experiments were conducted: In experiment I, we compared the effect of sucrose supplementation in vitrification solution along with ovarian fragments of different sizes on post-warming tissue viability and follicle architecture. Fragments of two different sizes, with a thickness and radius of 1.5 × 0.75 mm and 3 × 1.5 mm respectively were vitrified in vitrification solution without sucrose and with 0.5 M sucrose supplementation. Post-warming, fragments of ovarian tissue (fresh and vitrified) were evaluated for viability (Calcein AM/Propidium Iodide) and for morphology (hematoxylin-eosin). In experiment II, we aimed to reduce cryoprotectant toxicity by using lower CPA concentrations in combination with an optimized carrier medium (HypThermosol®; HTS). Ovarian tissue fragments were randomly allocated to five groups (A: fresh controls; B: vitrified in GLOBAL® TOTAL® LP w/HEPES with 15% ethylene glycol (EG) and 15% DMSO; C: vitrified in HTS with 5% EG and 5% DMSO; D: vitrified in HTS with 10% EG and 10% DMSO; E: vitrified in HTS with 15% EG and 15% DMSO). Fragments (fresh and vitrified) were evaluated for morphology (hematoxylin-eosin) and for apoptosis through the activity of caspase-3. Results showed that follicular morphology was affected by the size of the fragment; smaller sized fragments contained a greater proportion of intact follicles (53.8 ± 2.0%) compared to the larger fragments (40.3 ± 2.0%). Our results demonstrated that 1.5 × 0.75 mm sized pieces vitrified in a vitrification solution supplemented with 0.5 M sucrose had more intact follicles (54.8 ± 1.3%; P = 0.0002) after vitrification. In addition, HTS presented no additional protective effect as a base medium, neither for follicular morphology nor apoptotic rate.

Parental genomes segregate into distinct blastomeres during multipolar zygotic divisions leading to mixoploid and chimeric blastocysts

Background

During normal zygotic division, two haploid parental genomes replicate, unite and segregate into two biparental diploid blastomeres.

Results

Contrary to this fundamental biological tenet, we demonstrate here that parental genomes can segregate to distinct blastomeres during the zygotic division resulting in haploid or uniparental diploid and polyploid cells, a phenomenon coined heterogoneic division. By mapping the genomic landscape of 82 blastomeres from 25 bovine zygotes, we show that multipolar zygotic division is a tell-tale of whole-genome segregation errors. Based on the haplotypes and live-imaging of zygotic divisions, we demonstrate that various combinations of androgenetic, gynogenetic, diploid, and polyploid blastomeres arise via distinct parental genome segregation errors including the formation of additional paternal, private parental, or tripolar spindles, or by extrusion of paternal genomes. Hence, we provide evidence that private parental spindles, if failing to congress before anaphase, can lead to whole-genome segregation errors. In addition, anuclear blastomeres are common, indicating that cytokinesis can be uncoupled from karyokinesis. Dissociation of blastocyst-stage embryos further demonstrates that whole-genome segregation errors might lead to mixoploid or chimeric development in both human and cow. Yet, following multipolar zygotic division, fewer embryos reach the blastocyst stage and diploidization occurs frequently indicating that alternatively, blastomeres with genome-wide errors resulting from whole-genome segregation errors can be selected against or contribute to embryonic arrest.

Conclusions

Heterogoneic zygotic division provides an overarching paradigm for the development of mixoploid and chimeric individuals and moles and can be an important cause of embryonic and fetal arrest following natural conception or IVF.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13059-022-02763-2.

Electrically-driven handling of gametes and embryos: taking a step towards the future of ARTs

Electrical stimulation of gametes and embryos and on-chip manipulation of microdroplets of culture medium serve as promising tools for assisted reproductive technologies (ARTs). Thus far, dielectrophoresis (DEP), electrorotation (ER) and electrowetting on dielectric (EWOD) proved compatible with most laboratory procedures offered by ARTs. Positioning, entrapment and selection of reproductive cells can be achieved with DEP and ER, while EWOD provides the dynamic microenvironment of a developing embryo to better mimic the functions of the oviduct. Furthermore, these techniques are applicable for the assessment of the developmental competence of a mammalian embryo in vitro. Such research paves the way towards the amelioration and full automation of the assisted reproduction methods. This article aims to provide a summary on the recent developments regarding electrically stimulated lab-on-chip devices and their application for the manipulation of gametes and embryos in vitro.

The health effect of probiotics on high-fat diet-induced cognitive impairment, depression and anxiety: A cross-species systematic review

Obesity is a complex disease with many co-morbidities, including impaired cognitive functions. Obese individuals often contain an aberrant microbiota. Via the microbiota-gut-brain axis, the altered microbiota composition can affect cognition or induce anxiety- or depressive-like behavior. Probiotics have been shown to alleviate both obesity- and neurobehavioral disorder-related symptoms. Here, we evaluated previously published results on the effectiveness of probiotic intervention in alleviating obesity- or high-fat diet (HFD)-related cognitive impairment, depression and anxiety. A systematic search was performed in PubMed, Embase, and Google Scholar until June 2021 to identify relevant articles. Seventeen studies were included: one human and sixteen animal studies. Overall, the findings support the beneficial health effect of probiotics on HFD-induced cognitive impairment and anxiety. However, the results suggest that multi-strain probiotic treatments should be used with caution, especially in the absence of HFD-induced impairment. Future studies should overcome the large variation in study design and high risk of bias found in the current evidence. Nevertheless, probiotic treatment, in particular using the Lactobacillus genus, seems promising.

Single-cell genome-wide concurrent haplotyping and copy-number profiling through genotyping-by-sequencing

Single-cell whole-genome haplotyping allows simultaneous detection of haplotypes associated with monogenic diseases, chromosome copy-numbering and subsequently, has revealed mosaicism in embryos and embryonic stem cells. Methods, such as karyomapping and haplarithmisis, were deployed as a generic and genome-wide approach for preimplantation genetic testing (PGT) and are replacing traditional PGT methods. While current methods primarily rely on single-nucleotide polymorphism (SNP) array, we envision sequencing-based methods to become more accessible and cost-efficient. Here, we developed a novel sequencing-based methodology to haplotype and copy-number profile single cells. Following DNA amplification, genomic size and complexity is reduced through restriction enzyme digestion and DNA is genotyped through sequencing. This single-cell genotyping-by-sequencing (scGBS) is the input for haplarithmisis, an algorithm we previously developed for SNP array-based single-cell haplotyping. We established technical parameters and developed an analysis pipeline enabling accurate concurrent haplotyping and copy-number profiling of single cells. We demonstrate its value in human blastomere and trophectoderm samples as application for PGT for monogenic disorders. Furthermore, we demonstrate the method to work in other species through analyzing blastomeres of bovine embryos. Our scGBS method opens up the path for single-cell haplotyping of any species with diploid genomes and could make its way into the clinic as a PGT application.

New Alternative Mixtures of Cryoprotectants for Equine Immature Oocyte Vitrification

Simple Summary

Oocyte cryopreservation allows female gametes to be conserved for long periods, which would be of benefit for mares of high genetic merit, but its efficiency is not satisfactory yet. Therefore, the aim of this study was to optimize a vitrification protocol for equine oocytes using a systematic approach. We performed a side-by-side comparison of different cryoprotective agents (CPAs) during the vitrification and warming of equine oocytes. In the first experiment, a fixed mixture of CPAs that enter the oocyte was used, and three sugars were compared, which cannot penetrate the oocyte but provide protection through an osmotic effect. In the second experiment, one sugar from the first experiment was selected to compare three mixtures of CPAs that enter the oocyte. Overall, the embryo development was reduced after oocyte cryopreservation when compared to fresh oocytes. Yet, we were able to produce embryos with all six cryoprotective agent mixtures, and we identified one promising combination of cryoprotectants, consisting of propylene glycol, ethylene glycol, and galactose, that resulted in blastocyst rates in the same range as the fresh control group.

Abstract

Equine oocyte vitrification would benefit the growing in vitro embryo production programs, but further optimization of the protocol is necessary to reach clinical efficiency. Therefore, we aimed to perform a direct comparison of non-permeating and permeating cryoprotective agents (CPAs) during the vitrification and warming of equine immature oocytes. In the first experiment, cumulus oocytes complexes (COCs) were vitrified comparing sucrose, trehalose, and galactose in combination with ethylene glycol (EG) and dimethyl sulfoxide (DMSO). In the second experiment, the COCs were vitrified using three mixtures of permeating CPAs in a 50:50 volume ratio (ethylene glycol-dimethyl sulfoxide (ED), propylene glycol-ethylene glycol (PE), and propylene glycol-dimethyl sulfoxide (PD)) with galactose and warmed in different galactose concentrations (0.3 or 0.5 mol/L). Overall, all the treatments supported blastocyst formation, but the developmental rates were lower for all the vitrified groups in the first (4.3 to 7.6%) and the second (3.5 to 9.4%) experiment compared to the control (26.5 and 34.2%, respectively; p < 0.01). In the first experiment, the maturation was not affected by vitrification. The sucrose exhibited lower cleavage than the control (p = 0.02). Although the galactose tended to have lower maturation than trehalose (p = 0.060) and control (p = 0.069), the highest numerical cleavage and blastocyst rates were obtained with this CPA. In the second experiment, the maturation, cleavage, and blastocyst rates were similar between the treatments. Compared to the control, only the ED reached similar maturation (p = 0.02) and PE similar cleavage (p = 0.1). The galactose concentration during warming did not affect the maturation, cleavage, or blastocyst rates (p > 0.1), but the PE-0.3 exhibited the highest blastocyst rate (15.1%) among the treatments, being the only one comparable to the control (34.2%). As such, PE–galactose provides a valuable option for equine immature oocyte vitrification and should be considered for the future optimization of the protocol.

P–207 Heterogoneic cell division proven to occur in bovine zygotes

Study question

We hypothesize that the zygote can segregate parental genomes via a non-canonical pathway. We coined this heterogoneic cell division. Can we proof the existence of this new segregational pathway?

Summary answer

We confirmed the existence of this non-canonical segregation mechanism leading to mixoploidy and provide a catalogue of abnormal zygotic divisions.

What is known already

Embryos show a high degree of chromosomal instability leading to chromosomal mosaicism. Chromosomal aberrations affect the developmental potential. We developed haplarithmisis which determines the single-cell genome-wide haplotype and copy number and allows to deduce the parental and segregational origin. Analysis of cleavage-stage bovine embryos by haplarithmisis, discovered the presence of uniparental and biparental blastomere lineages in individual embryos. We hypothesized that whole genome segregations can occur via a non-canonical zygotic division, a process termed “heterogoneic” division. Abnormal zygotic division has been observed in bovine and human in vitro produced zygotes using time-lapse, but parental genome segregation has never been disclosed.

Study design, size, duration

We hypothesized that abnormal cytokinetics and spindle mechanics may underlie the segregation of parental genomes in a separate blastomere line. In vitro produced zygotes were monitored by time-lapse microscopy. Zygotes cleaving 3 or 4 cells were disaggregated, picked and analysed by haplarithmisis.

Participants/materials, setting, methods

Blastomeres from bovine in vitro produced zygotes cleaving directly into 3 or 4 blastomeres, identified by time-lapse monitoring, were tubed following zona removal and blastomere dissociation and whole-genome amplified. Samples were subsequently hybridized on Illumina Bovine HD BeadChip SNP arrays. Data was analyzed by haplarithmisis, using a the siCHILD-bovine algorithm, to infer the haplotypes and the copy number of the parental genomes. Blastomeres showing failed haplarithmisis plots were low-coverage whole-genome sequenced on a HiSeq4000 sequencer. Main results and the role of chance: We obtained 25 bovine embryos, comprising 82 blastomeres, derived from 12 families (12 cows and 2 bulls) that cleaved directly into 3 or 4 blastomeres. Sixteen, 7 and 2 out of 25 zygotes cleaved respectively in 3 cells, 4 cells and 3 cells and a fragment. In at least 20 embryos, more than one paternal haplotype was identified, showing that a polyspermic fertilization resulted in an abnormal division. All embryos contained a whole-genome abnormality in at least one blastomere, resulting in mixoploid (5), mixed diploid biparental and androgenetic (12), polyploid (4), mixed gynogenetic and androgenetic (2) and androgenetic (2) embryos. Twenty-one embryos had at least one blastomere containing a uniparental signature. Based on the blastomere haplotype profiles we classified the embryos in six segregation categories. In twelve blastomeres haplarithmisis failed. Massive parallel sequencing of the amplified DNA showed the presence of mitochondrial DNA, indicating the blastomere did not contain any genomic DNA. This observation confirms that heterogoneic cell division does occur via different non-canonical zygotic segregations, which result in a variety of chimeric and mixoploid embryos constitutions.

Limitations, reasons for caution

These findings apply to a small set of bovine in vitro produced abnormally cleaving embryos. Segregation patterns may be incomplete and their true in vitro and in vivo prevalence remains unknown. Based on the haplotypes the non-canonical divisions have been reconstructed. Those patterns can now be evaluated and tested.

Wider implications of the findings: This study shows that heterogoneic cell division occurs. We hypothesize this non-canonical division occurs frequently in both in vitro and in vivo, not only in cattle but also in man and hypothesize that persistence of such cell lines might explain the development of androgenetic tumorous outgrowths and mosaic uniparental individuals.

Trial registration number

Not applicable

Anti-Müllerian Hormone and OPU-ICSI Outcome in the Mare

Anti-Müllerian hormone (AMH) reflects the population of growing follicles and has been related to mammalian fertility. In the horse, clinical application of ovum pick-up and intracytoplasmic sperm injection (OPU-ICSI) is increasing, but results depend largely on the individuality of the mare. The aim of this study was to assess AMH as a predictor for the OPU-ICSI outcome in horses. Therefore, 103 mares with a total follicle count above 10 were included in a commercial OPU-ICSI session and serum AMH was determined using ELISA. Overall, the AMH level was significantly correlated with the number of aspirated follicles and the number of recovered oocytes (p < 0.001). Mares with a high AMH level (≥2.5 µg/L) yielded significantly greater numbers of follicles (22.9 ± 1.2), oocytes (13.5 ± 0.8), and blastocysts (2.1 ± 0.4) per OPU-ICSI session compared to mares with medium (1.5-2.5 µg/L) or low AMH levels (<1.5 µg/L), but no significant differences in blastocyst rates were observed. Yet, AMH levels were variable and 58% of the mares with low AMH also produced an embryo. In conclusion, measurement of serum AMH can be used to identify mares with higher chances of producing multiple in vitro embryos, but not as an independent predictor of successful OPU-ICSI in horses.

Cryopreservation of equine oocytes: looking into the crystal ball

Invitro embryo production has evolved rapidly in the horse over the past decade, but blastocyst rates from vitrified equine oocytes remain quite poor and further research is needed to warrant application. Oocyte vitrification is affected by several technical and biological factors. In the horse, short exposure of immature oocytes to the combination of permeating and non-permeating cryoprotective agents has been associated with the best results so far. High cooling and warming rates are also crucial and can be obtained by using minimal volumes and open cryodevices. Vitrification of invivo-matured oocytes has yielded better results, but is less practical. The presence of the corona radiata seems to partially protect those factors that are necessary for the construction of the normal spindle and for chromosome alignment, but multiple layers of cumulus cells may impair permeation of cryoprotective agents. In addition to the spindle, the oolemma and mitochondria are also particularly sensitive to vitrification damage, which should be minimised in future vitrification procedures. This review presents promising protocols and novel strategies in equine oocyte vitrification, with a focus on blastocyst development and foal production as most reliable outcome parameters.

151 Multipolar zygotic divisions result in multinuclear and anuclear blastomeres in cattle

The mammalian zygotic cleavage is expected to result in two mononuclear blastomeres. However, zygotes undergoing multipolar divisions resulting in direct cleavage into three or four cells are frequently observed in bovine and human embryonic development and have been associated with decreased euploidy rates of resulting blastocysts and a lower pregnancy rate (Somfai et al. 2010 J. Reprod. Dev. 56, 200-207; https://doi.org/10.1262/jrd.09-097a; Zhan et al. 2016 PLoS ONE 11, 1-19; https://doi.org/10.1371/journal.pone.0166398; Sugimura et al. 2017 J. Reprod. Dev. 63, 353-357; https://doi.org/10.1262/jrd.2017-041). Therefore, multipolar zygotic divisions may underly genetic abnormalities by aberrant segregation of the chromosomal material resulting in multinucleated or anuclear blastomeres. These abnormal blastomeres have been observed in human cleavage-stage embryos (Nogueira et al. 2000 Fertil. Steril. 74, 295-298; https://doi.org/10.1016/s0015-0282(00)00642-7; Chatzimeletiou et al. 2006 Hum. Reprod. 20, 672–682; https://doi.org/10.1093/humrep/deh652), but the prevalence in bovine embryos and the direct association with the multipolar division in both bovine and human embryos remains unknown. We hypothesised that anuclear and multinuclear blastomeres also occur in bovine embryos, and we aimed to unravel the link between multipolar zygotic divisions and genome segregation errors by determining the nuclear blastomere content in a bovine model. Therefore, oocytes from 5 cows were matured and fertilized in vitro by the same bull according to our standard in vitro production procedure (Wydooghe et al. 2014 Reproduction 148, 519-529). The first cleavage was monitored the by time-lapse imaging. Forty-three blastomeres from 22 bipolar zygotic divisions, and 65 blastomeres from 20 multipolar zygotic divisions were collected immediately after the first cleavage, using pronase to isolate the individual blastomeres. The area of each blastomere was measured and the number of nuclei was determined after fixation and staining with Hoechst 33342. Generalized mixed effect models were built to identify the effect of the type of cleavage (bipolar vs. multipolar) on the number of nuclei (mononuclear vs. anuclear or multinuclear) in the blastomeres. Linear mixed models were built to determine the effect of the type of cleavage and the nuclear content on the size of the blastomeres. Embryos presented a greater number of blastomeres with a normal nuclear content (92.6 ± 0.4%) after a bipolar cleavage compared with multipolar division (73.2 ± 0.7%; P=0.03). Moreover, blastomeres presented a 28% larger blastomere area (P&lt;0.001) after bipolar division compared with multipolar division. Notably, anuclear blastomeres tended to be smaller than multi- and mononuclear blastomeres (P=0.09 for both), while no difference was found between mono and multinucleated blastomeres (P=0.84). In conclusion, this is one of the first reports on the association between nuclear blastomere content in bovine embryos and the dynamics of the first zygotic division. Even though sample size was limited, these results confirm the hypothesised link between multipolar division and abnormal genome segregation as determined by multinuclear and anuclear blastomeres in the resulting blastomeres. Therefore, multipolar cell divisions at the zygotic division may underly at least some of the genetic abnormalities observed in embryos at early development.

Guidelines for first responders based on results from deploying a mockup radiological dispersal device

During the past 7th Security Framework Program the European Commission funded a research project called CATO (CBRN Crisis management, Architectures, Technologies and Operational procedures) to develop a prototype decision support system for crisis management in addition to providing a suite of guidelines for first responders and incident commanders when dealing with chemical, biological, radiological or nuclear incidents. In order to derive these guidelines a proof-of-concept experiment was setup during which several passive agent (Stable CsCl) dispersions with improvised explosive devices and vehicle-borne improvised explosive devices were carried out. Each dispersion was thoroughly characterised by a number of monitoring devices, including high-volume air samplers and size-segregated air samplers. All environmental and forensic samples were collected by the UK counter terrorism police, following strict labelling and chain-of-custody protocols. The samples were analysed at the Belgian Nuclear Research Center suing the k0 method for instrumental neutron activation technique. A full consequence assessment analysis was carried out assuming that the observed concentration of Cs-133 in samples was Cs-137 instead and use was made of the specific activity of Cs-137. Due to the sensitivity of the information the European Commission classified this research. The resulted reported on in this work have been unclassified and are released to assist emergency planners and first responders to take the necessary precautions. The results indicate that, up to distances of 50 m from ground zero radiation levels will be considerable and therefore live-saving actions must be performed by fire/rescue wearing full protective gear. In addition, low-wind conditions will favor a long airborne residence time and therefore the use of full-face protective gear is a must. In order to protect first responders, a radiation protection specialist is to determine how long people can enter and remain in the contaminated area. The recovery of evidence in the case of a car-bomb will be hard or even impossible due to the high level of radioactive material remaining inside the vehicle.

A high glucose concentration during early stages of in vitro equine embryo development alters expression of genes involved in glucose metabolism

BACKGROUND

Equine embryos exhibit an unusual pattern of glucose tolerance in vitro and are currently cultured in hyperglycaemic conditions.

OBJECTIVE

Our main objective was to analyse the effect of different glucose concentrations on in vitro-produced equine embryo development and quality.

STUDY DESIGN

Experiments comparing in vitro and in vivo produced embryos.

METHODS

Oocytes (n = 641) were collected from post-mortem ovaries, matured in vitro and fertilised by intracytoplasmic sperm injection (ICSI). Embryo culture was divided from Day 0 to Day 4 and from Day 4 to Day 9 in three groups: 5-10 (5 and 10 mmol/L glucose respectively; n = 87); 5-17 (5 and 17.5 mmol/L; n = 66); and 10-17 (10 and 17.5 mmol/L; n = 117). A control group of 20 in vivo produced blastocysts was included. Cleavage and blastocyst rates were evaluated and embryos were snap-frozen for analysis of the relative mRNA expression of genes related to mitochondrial function, DNA methylation, apoptosis, glucose transport and metabolism.

RESULTS

No differences were observed in the cleavage or blastocyst rates among in vitro groups. Under high glucose conditions in vitro (10-17 group), BAX/BCL2 was higher, and PFKP, LDHA and COX2 were overexpressed compared to all other groups. The two groups with 5 mmol/L glucose concentration during the first culture stage (5-10 and 5-17) displayed similar patterns which differed to the 10-17 group.

MAIN LIMITATIONS

Conclusions related to embryo quality are based on gene expression patterns. Transfer of in vitro-produced embryos would reveal whether the observed differences improve embryo developmental competence.

CONCLUSIONS

Five mM glucose during the first days of culture seems to be preferable to avoid over-activation of embryonic glycolytic pathways. Further studies are necessary to determine whether this improves embryo developmental competence.

Maternal Recognition of Pregnancy in the Horse: Are MicroRNAs the Secret Messengers?

The signal for maternal recognition of pregnancy (MRP) has still not been identified in the horse. High-throughput molecular biology at the embryo-maternal interface has substantially contributed to the knowledge on pathways affected during MRP, but an integrated study in which proteomics, transcriptomics and miRNA expression can be linked directly is currently lacking. The aim of this study was to provide such analysis. Endometrial biopsies, uterine fluid, embryonic tissues, and yolk sac fluid were collected 13 days after ovulation during pregnant and control cycles from the same mares. Micro-RNA-Sequencing was performed on all collected samples, mRNA-Sequencing on the same tissue samples and mass spectrometry was conducted previously on the same fluid samples. Differential expression of miRNA, mRNA and proteins showed high conformity with literature and confirmed involvement in pregnancy establishment, embryo quality, steroid synthesis and prostaglandin regulation, but the link between differential miRNAs and their targets was limited and did not indicate the identity of an unequivocal signal for MRP in the horse. Differential expression at the embryo-maternal interface was prominent, highlighting a potential role of miRNAs in embryo-maternal communication during early pregnancy in the horse. These data provide a strong basis for future targeted studies.

29 Time-lapse analysis of bovine embryos derived after invitro fertilization from vitrified and fresh oocytes

Oocyte vitrification enables the long-term conservation of female genetic resources. However, obtaining viable bovine embryos from vitrified oocytes has proven to be difficult. Embryo development is a dynamic process, and critical stages can go unnoticed with the use of traditional morphologic assessments. Therefore, the aim was to evaluate morphokinetic parameters in embryos derived from fresh versus vitrified oocytes. After 22h of IVM, oocytes were divided into (1) oocytes surrounded by multiple layers of cumulus cells (COCs; n=275) and (2) oocytes partially denuded, leaving only corona radiata (CR; n=178). Then, two-thirds of the CR oocytes were subjected to one of two vitrification protocols as follows: high concentration of cryoprotectants (CR-H; n=171; Ortiz-Escribano et al. 2016 Theriogenology 86, 635-641) and low concentration of cryoprotectants (CR-L; n=163; Ishii et al. 2018 J. Reprod. Develop. 6). After warming, vitrified oocytes were incubated ~2h in maturation medium. Invitro fertilization and culture were performed simultaneously for all groups. Four to eight zygotes from each group were assigned randomly to time lapse (Primo Vision; Vitrolife), and group culture was performed in leftovers as a control. Differences between groups in survival (intact zygotes after IVF), cleavage, and blastocyst rates were evaluated by logistic regression. Morphokinetic data (time to reach first (1-2 cells), second (3-4 cells), third (5-8), fourth (9-16 cells), fifth (&gt;16 cells), cleavage, and blastocyst stage, and time in lag phase) were investigated. Survival rates in COCs (98%) and CR (96%) groups were not different; CR-H (87%) showed lower survival than COCs but similar survival to that of CR. Group CR-L (82%) had a lower survival rate than the rest of the groups (P&lt;0.05). Higher cleavage rate (83%) was found in COCs compared with the rest of the groups. The CR and CR-H groups showed similar cleavage rate (65 and 55%, respectively), whereas CR-L had a lower cleavage rate (42%) than other groups (P&lt;0.05). As expected, both vitrified groups showed lower blastocyst rates (4% for CR-H and 10% for CR-L) than fresh COCs (44%; P&lt;0.05). Morphokinetics measures were affected by the treatments: time to reach first cleavage was similar for COCs (35.3h), CR (38.4h), and CR-L (34.8h), whereas CR-H was slower (42.4h). However, the fourth division was reached earlier by CR-H (51.7h), which was significantly faster than for CR-L (88.8 h; P&lt;0.05) but similar for COCs (71.3h) and CR (60.7h). In conclusion, more morphokinetic data are needed to compare different vitrification methods and confirm whether time-lapse analysis can be used to predict blastocyst outcome after oocyte vitrification.

Platelet-activating factor acetylhydrolase 1B3 (PAFAH1B3) is required for the formation of the meiotic spindle during in vitro oocyte maturation

Platelet-activating factor (PAF) is a well-described autocrine growth factor involved in several reproductive processes and is tightly regulated by its hydrolysing enzyme, PAF acetylhydrolase 1B (PAFAH1B). This intracellular enzyme consists of three subunits: one regulatory, 1B1, and two catalytic, 1B2 and 1B3. PAFAH1B3 has remained uncharacterised until now. Here, we report that PAFAH1B3 is present during the different stages of the first meiotic division in bovine, murine and human oocytes. In these species, the PAFAH1B3 subunit was clearly present in the germinal vesicle, while at metaphase I and II, it localised primarily at the meiotic spindle structure. In cattle, manipulation of the microtubules of the spindle by nocodazole, taxol or cryopreservation revealed a close association with PAFAH1B3. On the other hand, disruption of the enzyme activity either by P11, a selective inhibitor of PAFAH1B3, or by PAFAH1B3 antibody microinjection, caused arrest at the MI stage with defective spindle morphology and consequent failure of first polar body extrusion. In conclusion, our results show that one of the catalytic subunits of PAFAH1B, namely PAFAH1B3, is present in bovine, murine and human oocytes and that it plays a functional role in spindle formation and meiotic progression during bovine oocyte maturation.

Bta-miR-10b Secreted by Bovine Embryos Negatively Impacts Preimplantation Embryo Quality

In a previous study, we found miR-10b to be more abundant in a conditioned culture medium of degenerate embryos compared to that of blastocysts. Here, we show that miR-10b mimics added to the culture medium can be taken up by embryos. This uptake results in an increase in embryonic cell apoptosis and aberrant expression of DNA methyltransferases (DNMTs). Using several algorithms, Homeobox A1 (HOXA1) was identified as one of the potential miR-10b target genes and dual-luciferase assay confirmed HOXA1 as a direct target of miR-10b. Microinjection of si-HOXA1 into embryos also resulted in an increase in embryonic cell apoptosis and downregulation of DNMTs. Cell progression analysis using Madin–Darby bovine kidney cells (MDBKs) showed that miR-10b overexpression and HOXA1 knockdown results in suppressed cell cycle progression and decreased cell viability. Overall, this work demonstrates that miR-10b negatively influences embryo quality and might do this through targeting HOXA1 and/or influencing DNA methylation.

Intracellular localisation of platelet-activating factor during mammalian embryo development in vitro: a comparison of cattle, mouse and human

Platelet-activating factor (PAF) is a well-known marker for embryo quality and viability. For the first time, we describe an intracellular localisation of PAF in oocytes and embryos of cattle, mice and humans. We showed that PAF is represented in the nucleus, a signal that was lost upon nuclear envelope breakdown. This process was confirmed by treating the embryos with nocodazole, a spindle-disrupting agent that, as such, arrests the embryo in mitosis, and by microinjecting a PAF-specific antibody in bovine MII oocytes. The latter resulted in the absence of nuclear PAF in the pronuclei of the zygote and reduced further developmental potential. Previous research indicates that PAF is released and taken up from the culture medium by preimplantation embryos invitro, in which bovine serum albumin (BSA) serves as a crucial carrier molecule. In the present study we demonstrated that nuclear PAF does not originate from an extracellular source because embryos cultured in polyvinylpyrrolidone or BSA showed similar levels of PAF in their nuclei. Instead, our experiments indicate that cytosolic phospholipase A2 (cPLA2) is likely to be involved in the intracellular production of PAF, because treatment with arachidonyl trifluoromethyl ketone (AACOCF3), a specific cPLA2 inhibitor, clearly lowered PAF levels in the nuclei of bovine embryos.

Genome stability of bovine in vivo-conceived cleavage-stage embryos is higher compared to in vitro-produced embryos

STUDY QUESTION

Is the rate and nature of chromosome instability (CIN) similar between bovine in vivo-derived and in vitro-cultured cleavage-stage embryos?

SUMMARY ANSWER

There is a major difference regarding chromosome stability of in vivo-derived and in vitro-cultured embryos, as CIN is significantly lower in in vivo-derived cleavage-stage embryos compared to in vitro-cultured embryos.

WHAT IS KNOWN ALREADY

CIN is common during in vitro embryogenesis and is associated with early embryonic loss in humans, but the stability of in vivo-conceived cleavage-stage embryos remains largely unknown.

STUDY DESIGN, SIZE, DURATION

Because human in vivo preimplantation embryos are not accessible, bovine (Bos taurus) embryos were used to study CIN in vivo. Five young, healthy, cycling Holstein Friesian heifers were used to analyze single blastomeres of in vivo embryos, in vitro embryos produced by ovum pick up with ovarian stimulation (OPU-IVF), and in vitro embryos produced from in vitro matured oocytes retrieved without ovarian stimulation (IVM-IVF).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Single blastomeres were isolated from embryos, whole-genome amplified and hybridized on Illumina BovineHD BeadChip arrays together with the bulk DNA from the donor cows (mothers) and the bull (father). DNA was also obtained from the parents of the bull and from the parents of the cows (paternal and maternal grandparents, respectively). Subsequently, genome-wide haplotyping and copy-number profiling was applied to investigate the genomic architecture of 171 single bovine blastomeres of 16 in vivo, 13 OPU-IVF and 13 IVM-IVF embryos.

MAIN RESULTS AND THE ROLE OF CHANCE

The genomic stability of single blastomeres in both of the in vitro-cultured embryo cohorts was severely compromised (P < 0.0001), and the frequency of whole chromosome or segmental aberrations was higher in embryos produced in vitro than in embryos derived in vivo. Only 18.8% of in vivo-derived embryos contained at least one blastomere with chromosomal anomalies, compared to 69.2% of OPU-IVF embryos (P < 0.01) and 84.6% of IVM-IVF embryos (P < 0.001).

LARGE SCALE DATA

Genotyping data obtained in this study has been submitted to NCBI Gene Expression Omnibus (GEO; accession number GSE95358).

LIMITATIONS REASONS FOR CAUTION

There were two main limitations of the study. First, animal models may not always reflect the nature of human embryogenesis, although the use of an animal model to investigate CIN was unavoidable in our study. Second, a limited number of embryos were obtained, therefore more studies are warranted to corroborate the findings.

WIDER IMPLICATIONS OF THE FINDINGS

Although CIN is also present in in vivo-developed embryos, in vitro procedures exacerbate chromosomal abnormalities during early embryo development. Hence, the present study highlights that IVF treatment compromises embryo viability and should be applied with care. Additionally, our results encourage to refine and improve in vitro culture conditions and assisted reproduction technologies.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by the Agency for Innovation by Science and Technology (IWT) (TBM-090878 to J.R.V. and T.V.), the Research Foundation Flanders (FWO; G.A093.11 N to T.V. and J.R.V. and G.0392.14 N to A.V.S. and J.R.V.), the European Union's FP7 Marie Curie Industry-Academia Partnerships and Pathways (IAPP, SARM, EU324509 to J.R.V., T.V., O.T, A.D., A.S. and A.K.) and Horizon 2020 innovation programme (WIDENLIFE, 692065 to J.R.V., O.T., T.V., A.K. and A.S.). M.Z.E., J.R.V. and T.V. are co-inventors on a patent application ZL913096-PCT/EP2014/068315-WO/2015/028576 ('Haplotyping and copy-number typing using polymorphic variant allelic frequencies'), licensed to Cartagenia (Agilent Technologies).

Steroids affect gene expression, ciliary activity, glucose uptake, progesterone receptor expression and immunoreactive steroidogenic protein expression in equine oviduct explants in vitro

The oviduct undergoes dramatic functional and morphological changes throughout the oestrous cycle of the mare. To unravel the effects of steroids on the morphology, functionality and gene expression of the equine oviduct, an in vitro oviduct explant culture system was stimulated with physiological concentrations of progesterone and 17β-oestradiol. Four conditions were compared: unsupplemented preovulatory explants, preovulatory explants that were stimulated with postovulatory hormone concentrations, unsupplemented postovulatory explants and postovulatory explants that were stimulated with preovulatory hormone concentrations. The modulating effects of both steroids on oviduct explants were investigated and the following parameters examined: (1) ciliary activity, (2) glucose consumption and lactate production pattern, (3) ultrastructure, (4) mRNA expression of embryotrophic genes, (5) steroidogenic capacities of oviductal explants and (6) progesterone receptor expression. The present paper shows that the equine oviduct is an organ with potential steroidogenic capacities, which is highly responsive to local changes in progesterone and 17β-oestradiol concentrations at the level of morphology, functionality and gene expression of the oviduct. These data provide a basis to study the importance of endocrine and paracrine signalling during early embryonic development in the horse.